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Structural, antimicrobial and spectral studies of copper(II) complexes of 2-benzoylpyridine N(4)-phenyl thiosemicarbazone
Abstract
Reaction of 2-benzoylpyridine N(4)-phenyl thiosemicarbazone (HL) with a variety of copper salts yielded a series of copper(II) complexes of the type [CuLX] where X=Cl (1), Br (2), NO3 (3), NCS (4), N3 (5) excluding the perchlorate complex. In the perchlorate complex (6), one molecule each of the neutral and deprotonated ligand is found to be coordinated to the metal. The complexes are characterized by molar conductivity measurements, magnetic studies, electronic, infrared and EPR spectral studies. The crystal structures of two copper complexes, 1 and 4 have been resolved using single crystal X-ray studies. The crystal structure of compound 1 revealed chlorine bridged dimer having monoclinic lattice with space group symmetry P21/c. The compound 4 adopts a distorted square planar geometry with N3S core as the base. The antimicrobial activity of the ligand and the copper complexes were tested against five types of bacteria isolated from clinical samples. The ligand (HL) was found to be active against Staphylococcus aureus. The copper(II) complexes were found to be active against Vibrio cholerae O1 and Salmonella paratyphi.
... As a result, the -NO 2 group bonded to conjugated system absorbs energy at lower frequencies than that in non-conjugated system, so the strong absorption band was seen at 1521 cm -1 in free Nitistpyrdlpz and 1492 cm -1 in Cu-Nitistpyrdlpz attributed to the asymmetric stretching of ν(NO 2 ) [24]. The absence of band at 2575 cm -1 corresponding to the stretching vibration of ν(S-H) [25] and presence of two strong bands at 1385 and 836 cm -1 corresponding to the stretching vibration of ν(C=S) indicates that thiosemicarbazone exists in thio-keto form [11,22,26]. The two IR bands attributed to ν(C=S) of ligand shifted to lower frequency (1242 cm -1 , 815 cm -1 ) on coordinated to copper(II) ion [26]. ...
... The absence of band at 2575 cm -1 corresponding to the stretching vibration of ν(S-H) [25] and presence of two strong bands at 1385 and 836 cm -1 corresponding to the stretching vibration of ν(C=S) indicates that thiosemicarbazone exists in thio-keto form [11,22,26]. The two IR bands attributed to ν(C=S) of ligand shifted to lower frequency (1242 cm -1 , 815 cm -1 ) on coordinated to copper(II) ion [26]. A sharp absorption band present at 1161 cm -1 , assigned to the stretching vibration of ν(N-N) in uncomplexed ligand [26,27] shifted to slightly higher frequency (1176 cm -1 ) in its copper(II) complex [27]. ...
... The two IR bands attributed to ν(C=S) of ligand shifted to lower frequency (1242 cm -1 , 815 cm -1 ) on coordinated to copper(II) ion [26]. A sharp absorption band present at 1161 cm -1 , assigned to the stretching vibration of ν(N-N) in uncomplexed ligand [26,27] shifted to slightly higher frequency (1176 cm -1 ) in its copper(II) complex [27]. In the complex, the positive mode of ν(N-N) band may arise because of the increasing bond strength i.e. increasing π-electrons density between these atoms as a result of deprotonation at H-N-C=S during the coordination of thiosemicarbazone anion to copper(II) ion [26]. ...
The anticancer activity of 5-Nitroisatin-4-(1-(2-pyridyl)piperazinyl)-3-thiosemicarbazone (Nitistpyrdlpz) and its Cu(II) complex against breast cancer cell lines; MCF-7 and MDA-MB-231 and epidermoid carcinoma; A431 showed that the complex contributed to reduce the percentage of cell viability toward all the tested cell lines but remarkable contribution toward MDA-MB-231 cell line. The IC 50 values of the complex and free ligand were found in the range of IC 50 0.85-1.24 µM and IC 50 3.28-3.53 µM, respectively. Among those cell lines, the complex may be the better anticancer agent toward MDA-MB-231 because of its action at micromolar concentration (IC 50 0.85 µM). The anticancer potency of ligands can be increased by substitution on parent isatin and pyridyl piperazinyl rings as well as their coordination to metal ions.
... 17,19 The non-existence of stretching band at about 2570 cm -1 , specific to ν(S-H) and the existence of two strong bands at 1336-1317 cm -1 , and 790-785cm -1 , specific to ν(C=S) confirmed the existence of solid thiosemicarbazones (L1 and L2) in the thione tautomeric form. [19][20][21][22] Bands appeared in uncomplexed thiosemicarbazones (L1 and L2) showed downward shift of ν(C=S) in their respective copper(II) complexes due to the coordination of sulphur in thiol tautomeric form and the deprotonation at H-N-C=S group and hence observed at the lower energy region 1311-1255 cm -1 and 773-746 cm -1 . 23 In the thiosemicarbazone L1, strong stretching bands appeared at 1693 cm -1 and 1619 cm -1 assigned to ν(C=O) and ν(C=N) of thiosemicarbazone respectively. ...
... The strong bands appeared at 1138-1113 cm -1 assigned to ν(N-N) frequencies of thiosemicarbazones. 20,23 The coordination of ligands (L1 and L2) to metal ion showed the positive shift of ν(N-N) band (1148-1127 cm -1 ) (CuL1 and CuL2), thereby confirming the formation of π bond in thioamide nitrogen atoms during coordination. 20,23 The shift in the position of ν(C=S), ν(C=O), and ν(C=N) bands of thiosemicarbazones to lower energy region in the complexes confirm the chelation of terdentate thiosemicarbazones to copper(II) ion thereby indicating the existence of complexes in distorted square planar geometry where one site is occupied by chloride ion. ...
... 20,23 The coordination of ligands (L1 and L2) to metal ion showed the positive shift of ν(N-N) band (1148-1127 cm -1 ) (CuL1 and CuL2), thereby confirming the formation of π bond in thioamide nitrogen atoms during coordination. 20,23 The shift in the position of ν(C=S), ν(C=O), and ν(C=N) bands of thiosemicarbazones to lower energy region in the complexes confirm the chelation of terdentate thiosemicarbazones to copper(II) ion thereby indicating the existence of complexes in distorted square planar geometry where one site is occupied by chloride ion. ...
N(4) modified copper thiosemicarbazones have been extensively studied for their anticancer potency toward various cancer cells as they exhibit less toxicity, wide spectrum of activity, non-resistance behavior and a novel mechanism of action as compared to that of platinum complexes. 5-Nitroisatin-4-thiomorpholinyl-3-thiosemicarbazone(L1), 5-nitroisatin-4, 4-dimethyl-3-thiosemicarbazone(L2), and their copper (II) complexes; CuL1 and CuL2 were prepared and characterized by elemental analysis, FTIR, NMR, ESI-HRMS, UV-Vis, TGA, PXRD (Le Bail fitting) and EPR techniques. PXRD analysis suggested that the copper (II) complexes possess a monoclinic crystal system with P1211 symmetry. The coordination of Cu(II) ion with thiosemicarbazones and one chloride ion suggests a distorted square planar geometry of complexes. All the compounds were screened against breast cancer (MCF-7 and MDA-MB-231), skin cancer (A431) and normal prostate cell line (PNT2) in terms of cell viability and found that all the synthesized compounds exhibited in vitro antiproliferation toward the tested cancer cells. These complexes were found to be more effective on MDA-MB-231 than on A431 and MCF-7 cells. The molecule, CuL1 was found to show a better anticancer potency compared to CuL2 as CuL1 was found to be less toxic to normal PNT2 cell line.
... As a result, the -NO2 group bonded to conjugated system absorbs energy at lower frequencies than that in non-conjugated system, so the strong absorption band was seen at 1521 cm -1 in free Nitistpyrdlpz and 1492 cm -1 in Cu-Nitistpyrdlpz attributed to the asymmetric stretching of ν(NO2) [22]. The absence of band at 2575 cm -1 corresponding to the stretching vibration of ν(S-H) [23] and presence of two strong bands at 1385 and 836 cm -1 corresponding to the stretching vibration of ν(C=S) indicates that thiosemicarbazone exists in thio-keto form [11,20,24]. The two IR bands attributed to ν(C=S) of ligand shifted to lower frequency (1242 cm -1 , 815 cm -1 ) on coordinated to copper(II) ion [24]. ...
... The absence of band at 2575 cm -1 corresponding to the stretching vibration of ν(S-H) [23] and presence of two strong bands at 1385 and 836 cm -1 corresponding to the stretching vibration of ν(C=S) indicates that thiosemicarbazone exists in thio-keto form [11,20,24]. The two IR bands attributed to ν(C=S) of ligand shifted to lower frequency (1242 cm -1 , 815 cm -1 ) on coordinated to copper(II) ion [24]. A sharp absorption band present at 1161 cm -1 , assigned to the stretching vibration of ν(N-N) in uncomplexed ligand [24,25] shifted to slightly higher frequency (1176 cm -1 ) in its copper(II) complex [25]. ...
... The two IR bands attributed to ν(C=S) of ligand shifted to lower frequency (1242 cm -1 , 815 cm -1 ) on coordinated to copper(II) ion [24]. A sharp absorption band present at 1161 cm -1 , assigned to the stretching vibration of ν(N-N) in uncomplexed ligand [24,25] shifted to slightly higher frequency (1176 cm -1 ) in its copper(II) complex [25]. In the complex, the positive mode of ν(N-N) band may arise because of the increasing bond strength i.e. increasing π-electrons density between these atoms as a result of deprotonation at H-N-C=S during the coordination of thiosemicarbazone anion to copper(II) ion [24]. ...
5-Nitroisatin-4-(1-(2-pyridyl)piperazinyl)-3-thiosemicarbazone (Nitistpyrdlpz) and its Cu(II) complex were synthesized and characterized by CHN and thermal analysis and spectroscopic measurements viz. UV-vis, FTIR, 1H NMR, 13C NMR, ESI-HRMS, PXRD and EPR. In the complex, copper(II) ion is coordinated by terdentate thiosemicarbazone anion and one chloride ion in a distorted square planar geometry. The synthesized compounds against breast cancer cell lines; MCF-7 and MDA-MB-231 and epidermoid carcinoma; A431 showed that the complex contributed to reduce the percentage of cell viability toward all the tested cell lines but remarkable contribution toward MDA-MB-231 cell line. The IC50 of the complex and free ligand was found in the range of IC50 0.85-1.24 μM and IC50 3.28-3.53 μM, respectively. Among those cell lines, the complex may be the better anticancer agent toward MDA-MB-231 because of its action at micromolar concentration (IC50 0.85 μM).
... Disappearance of ν(C=O) of amide I at 1645 cm − 1 (Qin et al., 2012) and the appearance of new band in the range of 1611-1625 cm − 1 in the ligands were indicatives of the involvement of C=O group in imine (-C=N-) bond formation (Qin et al., 2012). Partial involvement of NH 2 group in the formation of thiosemicarbazones was shown by ν(NH 2 ) at 1555-1567 cm − 1 (Yadav & Shivakumar, 2012) and ν(C=S) in two separate ranges of 841-1078 cm − 1 (Tiwari et al., 2016;Yamaguchi et al., 1958) and 1360-1380 cm − 1 (Aneesrahman et al., 2019;Joseph et al., 2006). The existence of thiosemicarbazones in thione form was shown by the absence of ν(C-SH) band at 2500-2600 cm − 1 (Bharti et al., 2003). ...
... In the FT-IR spectra of copper ( (Wiles et al., 1967) and 1320-1354 cm − 1 (Joseph et al., 2006) in the corresponding complexes showed the coordination of sulphur with metal ion. The overall impression of IR data indicated the partial grafting of thiosemicarbazone group into chitosan, and bonding of metal ion with thiosemicarbazones through phenolic oxygen, imino nitrogen and thione sulphur. ...
... If the G value is less than 4 ( G < 4) there will be an exchange interaction in the polycrystalline complex and if the G value is greater than 4 ( G > 4) the exchange interaction is negligible [67][68] . The G values for complexes 1-3 are 2.145, 4.205 and 3.686 respectively. ...
... The G values for complexes 1-3 are 2.145, 4.205 and 3.686 respectively. The result indicates that for complexes 1 and 3 there is an exchange interaction between the copper center, whereas for complex 2 the exchange interaction is negligible [67] . The geometry is elongated octahedral with the ground state d x 2 -y 2 orbital [69] for complexes 1 -3 . ...
A 2-amino-1H-benzo [de]isoquinoline-1,3-(2H)dione ligand (L) has been synthesized which forms a supramolecular metal-organic framework with various copper(Ⅱ) salts (1-3). The supramolecular structures are formed by a combination of covalent and noncovalent forces. The ligand (L) with copper chloride forms step-like chains in which the ligand is coordinated in a bidentate manner (1), whereas for the copper perchlorate derivative a ladder-like arrangement is attained in which the ligand is coordinated in both monodentate and bidentate fashion (2). A coordination polymer is formed with copper sulfate forming a wave-like arrangement (3). The EPR spectra revealed the elongated octahedral geometry around the cooper(Ⅱ) center in the complexes (1-3) which are in good agreement with the coordination environment observed from single crystal X-ray crystallographic studies. The complexes (1-3) are highly fluorescent in aqueous as well as organic solvents. Upon complexation, ligand-based emission is enhanced in complexes. So these complexes might be useful for bioimaging applications.
... [73] The peaks at 1315 cm À1 in both the thiophene-2-thiosemicarbazones were also in agreement to (C ¼ S) stretches. [75,76] The negative shifts (7-10 cm À1 ) of (C ¼ N) at 1624-1625 cm À1 in free ligands to 1614-1618 cm À1 in the corresponding complexes showed the coordination of azomethine nitrogen. [71,[77][78][79] This mode of coordination was further confirmed by the increase in (NN) from 1004-1009 cm À1 in ligands to 1014-1023 cm À1 in the respective complexes. ...
... It meant that the ring sulfur in thiophene was not involved in coordination. [73] The (C ¼ S) thiophene ring sulfur band at 1377 cm À1 [75,76] also remained unaffected in chitosan thiophene-2-thiosemicarbazones and their complexes, indicating the noninvolvement of ring sulfur in thiophene in coordination. The broad band due to (N-H) stretch was almost unaffected by coordination. ...
Chitosan is a polyfunctional biomaterial that is subjected to chemical modification through functionalization to give the derivatives of remarkable anticancer activity. In this study, functionalization of low molecular weight commercial chitosan (CS) (Mw < 3000 Da, 87% DDA) and high molecular weight crab shell chitosan (CCS) (viscosity average Mw 350 kDa, 67% DDA) as chitosan thiophene-2-thiosemicarbazones (DS 63.48–64.14%) and the formation of their copper(II) complexes were established by FT-IR, ¹³C NMR, EPR spectroscopy, powder X ray diffraction, elemental microanalysis and magnetic susceptibility measurements. The thermal study of the compounds showed a substantial stability up to 200°C until the commencement of chitosan chain degradation. The MTT assay revealed higher activity of CS (IC50 370 μgmL⁻¹ in MCF-7 and >400 μgmL⁻¹ in MDCK cell line) than CCS (IC50 > 400 μgmL⁻¹ in both cell lines), higher activity of CSTHPTSC (IC50 364 μgmL⁻¹ in MDCK and 369 μgmL⁻¹ in MCF-7 cell line) than CCSTHPTSC (IC50 > 400 μgmL⁻¹ in both cell lines), higher activity of the complexes Cu-CSTHPTSC (IC50 338 μgmL⁻¹ in MDCK and 318 μgmL⁻¹ in MCF-7 cell line) and Cu-CCSTHPTSC (IC50 293 μgmL⁻¹ in MDCK and >400 μgmL⁻¹ in MCF-7 cell line) than their corresponding ligands.
... The geometric parameter G, which is a measure of the exchange interaction between the copper centres in the polycrystalline samples, is estimated using the equation G = (g‖ − 2.0023)/(g ⊥ − 2.0023). As the value of G (3.685) is<4 indicating exchange interaction in between two paramagnetic centres [33,73,74]. Additionally, the exchange interaction is confirmed by the presence of singlet-triplet separation (J) which has the value 0.143 cm − 1 . ...
... Additionally, the exchange interaction is confirmed by the presence of singlet-triplet separation (J) which has the value 0.143 cm − 1 . The values of D and J both reveal the evidence of the existence of very weak antiferromagnetic exchange coupling for complex 3 [73]. Exchange interaction (antiferromagnetic exchange coupling) is also evidenced by the less magnetic moment value (1.63 BM) than the spin only. ...
Three new copper(II) complexes, [Cu(DPA)(ClO4)2(H2O)]MAP 1, [Cu(DPA)(ImH)(ClO4)2] 2 and [Cu2(DPA)2(2COO⁻)(ClO4)2]H2O 3 (where, DPA = di-(2-picolyl)amine, MPA = 2-methoxyacetophenone, ImH = Imidazole and 2COO⁻ = oxalate anion), have been synthesized and characterized using various physico-chemical techniques. DPA is a tridentate ligand with NNN donors atoms and imidazole is a monodentate ligand whereas, oxalate anion is a bridging ligand. Single crystal X-ray analysis reveals that 1–3 are neutral complexes. The X-band Epr spectral study in polycrystalline at RT and in DMSO solution at LNT have been analyzed. To examine the stability of complexes, density functional theory (DFT) calculations were performed. The obtained quantum chemical parameters like electron affinity, ionization potential, electronegativity, electrophilicity and global hardness and softness were discussed within the frame work of electronic structures and principles known as maximum hardness, minimum polarizability and minimum electrophilicity principles. Hirshfeld surface analysis showed that the supramolecular structures of the complexes 1–3 is stabilized mainly by CH⋯π, lp⋯π and various hydrogen bonding intermolecular interactions. Complex 3 shows ferromagnetic interaction, with J = +1.5 cm⁻¹, due to perchlorate bridging anion complex. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) support the electrochemical features of these complexes. The Hirshfeld surface analysis exhibited short-range forces of the hydrogen bonds in all studied complexes. In addition, antioxidant superoxide dismutase activity measurements of these complexes were also performed and discussed. The increased SOD activity of 1 can be assigned due to presence of labile coordinated water molecule. The results of SOD activity reveal that the coordination geometries have significant effect on the SOD catalytic activity.
... Thiosemicarbazones, crafted by combining thiosemicarbazide with aldehydes or ketones, have been extensively researched for their broad pharmacological actions, including anti-cancer [7,8], anti-microbial [9], anti-bacterial [10], and anti-fungal effects [11]. These compounds play a therapeutic role against diseases like tuberculosis, leprosy, cancer, and various infections, and are beneficial in treating conditions such as psoriasis and rheumatoid arthritis [12,13]. ...
... Thiosemicarbazones, crafted by combining thiosemicarbazide with aldehydes or ketones, have been extensively researched for their broad pharmacological actions, including anti-cancer [7,8], anti-microbial [9], anti-bacterial [10], and anti-fungal effects [11]. These compounds play a therapeutic role against diseases like tuberculosis, leprosy, cancer, and various infections, and are beneficial in treating conditions such as psoriasis and rheumatoid arthritis [12,13]. ...
... Structura scheletului de baza al hidrazincarbotioamidelor (figura 1a) este intens studiată datorită particularității sale de a fi ușor modelată în scopul amplificării sau atribuirii proprietăților necesare. Studiile recente sugerează că N-substituenții precum gruparea fenil generează compuși cu proprietăți biologice promițătoare [16]. Pe de altă parte, molecula Triapina, care demonstrează proprietăți anticancerigene valoroase și se află deja în cercetările clinice faza a III-a (figura 1b), confirmă că hidrazincarbotioamidele α-N-heterociclice prezintă interes considerabil [17; 18]. ...
The present study was focused on the synthesis of some N-(dimethylphenyl)hydrazine carbothioamides 1-4, that contain the following N-substituents: 2,4-dimethylphenyl; 2,5-dimethylphenyl; 2,6-dimethylphenyl; 3,4-dimethylphenyl, to increase lipophilicity and N-(dimethylphenyl)-2-(pyridin-2-ylmethylidene)hydrazinecarbothioamides 5-8, analogous of Triapine. The structural formula of the compounds was characterized by means of spectroscopy: FT-IR, 1H-, and 13CRMN, and the molecular structure, for the first time, by means of X-ray diffraction. The study of antioxidant activity has shown that all compounds 1-8 are powerful antioxidants. N-(dimethylphenyl)-2-(pyridin2-ylmethylidene)hydrazinecarbothioamides 5-8 were tested as inhibitors of MCF-7 (breast cancer) cell proliferation. It was found that all the compounds exhibit activity comparable to that of Doxorubicin, among them the compound N-(2,5-dimethylphenyl)-2-(pyridin-2-ylmethylidene)hydrazinecarbothioamide 6, with IC50=0.8 μM/L, demonstrated the highest activity.
... The synthesis of the copper paddle-wheel complex in acetonitrile resulted in the two solvent molecules being coordinated at the metal center; this was confirmed by single X-ray diffraction. After the crystals were immediately redissolved in a dimethylformamide solution, the molar conductivity measurement was Λ M 6.0 Ω −1 cm 2 mol −1 , as expected for a non-electrolyte compound in which the ligands were coordinated with the metal ion [33]. To identify the electronic transition bands of the copper complex, the solid-state diffuse reflectance spectra was analyzed. ...
A new Cu(II) paddle-wheel-like complex with 4-vinylbenzoate was synthesized using acetonitrile as the solvent. The complex was characterized by X-ray crystal diffraction, FT-IR, diffuse reflectance spectroscopy, thermogravimetric, differential scanning calorimetric, magnetic susceptibility, and electronic paramagnetic resonance analyses. The X-ray crystal diffraction analysis indicated that each copper ion was bound at an equatorial position to four oxygen atoms from the carboxylate groups of the 4-vinylbenzoate ligand in a square-based pyramidal geometry. The distance between the copper ions was 2.640(9) Å. The acetonitrile molecules were coordinated at the axial position to the copper ions. Exposure of the Cu(II) complex to humid air promoted the gradual replacement of the coordinated acetonitrile by water molecules, but the complex structure integrity remained. The EPR spectra exhibited signals attributed to the presence of a mixture of the monomeric (S = ½) and dimeric (S = 1) copper species in a possible 3:1 ratio. The magnetic studies revealed a peak at 50–100 K, which could be associated with the oxygen absorption capacity of the Cu(II)–vba complex.
... N-phenyl-hydrazinecarbothioamide (H 4 L) was prepared by followed reported procedure [27,28]. In brief; the phenyl isothiocyanate (1.35 g, 10 mmol) was dissolved in 50 ml methanol and 0.48 ml hydrazine hydrate were mixed drop wise for 10 minute at RT and the reaction mixture was kept for 1h or until the generation of white precipitation with continuous stirring. ...
The bidentate ligand thiosemicarbazone (H3L) and its Ni(II) complex were synthesized and characterized by single crystal X-ray diffraction and various spectroscopic methods. The Ni(II) complex exhibits almost square planar geometry around the nickel ion, coordinated by two ligands through N & S donor centers. The important structural features of single crystal of the complex are [space group: P-1; a = 11.0594(9) Ǻ; b = 12.2339(9) Ǻ; c = 14.8835(9) Ǻ; α = 110.857(6); β = 91.029(6) and γ = 108.710(7)]. The DFT/TD-DFT simulations have been performed to determine the HOMO-LUMO energy, electronic spectroscopy data, the minimum energy optimized structure and to calculate the reactivity descriptors of the compounds using the B3LYP level of theory. The DFT and NBO analysis based on theoretical investigation helps to locate the MEP surface and bonding mode of the ligand in complex respectively. Different reactivity descriptors establish a correlate between their reactivity and bio-molecular affinity of the molecules. The binding abilities of the compounds with DNA and BSA were within the order of standard DNA and BSA binders. The bio-molecular conformational change as well as interactions of the compounds were monitored by biophysical analyses like; 3D fluorescence, FRET calculations and anisotropy studies with BSA. The potent drug likeness antineoplastic and bio-activity of the H3L and Ni(II) complex were assessed using online software PASS and ADMET. The antiproliferative activity of the compounds was evaluated against the normal human embryonic kidney (HEK293) cells and the human breast carcinoma (MCF-7) cancer cell line. The Annexin V-FITC, Propidium iodide assay in the presence of the free ligand H3L and its Ni(II) complex were performed using flow cytometric method for their cell death mechanisms. Reactive Oxygen Species (ROS) production assay using 2′,7′-Dichlorodihydrofluorescein diacetate (DCFDA) was evaluated in presence of the compounds.
... The increasing importance of these ligands is attributed to their interesting coordination ability, analytical, biological, and pharmacological importance. Because of their structural variety, variable bonding, cyclo-metallation, ion-sensing capability, and physiological consequences, thiosemicarbazones, an important subclass of Schiff's bases, are exceptional chelators for many metal ions [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. They exhibit a variety of coordination modes, hence, opening up several possibilities for creation of new metal complexes that finds several biological applications [15][16]. ...
Three new conformationally rigid half-sandwich organoruthenium(II) complexes having compositions [(η6–p-cymene)Ru(TLS)Cl]Cl (1), [(η6–p-cymene)Ru(TLSM)Cl]Cl (2) and [(η6-p-cymene)Ru(TLSN)Cl]Cl (3) has been synthesized by reacting [(6-p-cymene)RuCl}2(µ-Cl)2] with respective thiosemicarbazones: 2-acetylpyridin-N(4)-phenylthiosemicarbazone (TLS), 2-acetylpyridine-N(4)-methylthiosemicarbazone (TLSM), and 2-acetylpyridine-N(4)-thiosemicarbazone (TLSN). The newly synthesized complexes have been characterized by elemental analysis, UV–Vis, FT-IR, and 1H and 13C NMR spectroscopy. The geometry optimizations for all three complexes confirmed the distorted tetrahedral piano-stool type geometry around Ru(II), which is further coordinated to azomethine nitrogen and thione sulphur centers. Apart from geometry optimizations, the Gibbs free energy calculations, frontier molecular orbital parameters, molecular electrostatic potential (MEP) values, as well as the bond order, have been computed for these complexes. Also, the newly synthesized complexes have been screened for their anti-mycobacterial and anticancer activities.
... The peaks at 1618-1620 cm − 1 were due to ν (C=N) [62,64]. The ν (C=S) stretches were shown at 884-897 cm − 1 [57,65] and 1306-1341 cm − 1 [61,66]. The IR spectra also showed the simultaneous appearance of the peaks at 1069-1096 cm − 1 corresponding to the C=S vibrations [57,65] coupled with other vibrations for the case in which thiocarbonyl group is attached with nitrogen atom [67]. ...
The one-pot synthetic method of condensation of isatin and 5-chloroisatin on to amino group at C2 position of the pyranose ring chitosan in chitosan thiosemicarbazide was employed to get these chitosan thiosemicarbazones (TSCs). The partial incorporation of thiosemicarbazone moiety in chitosan was shown by FT-IR and 13C NMR spectroscopic studies, powder X ray diffraction, and CHNS microanalysis. The NOS tridentate coordination behavior of TSCs with copper(II) chloride to give the square planar complexes was established by FT-IR spectroscopic data, magnetic susceptibility measurement, and EPR spectral analysis. The thermal stability of these biomaterial chitosan derivatives till the commencement of chain disruption at 200C was shown by thermal studies. As revealed by colorimetric MTT assays, the in vitro anticancer activity enhancement accorded with the functionalization of chitosan as isatin based chitosan TSCs, and NOS tridentate coordination of TSCs plus a monodentate coordination of chloride ion with copper(II) ion. Only a marginal activity difference of these compounds was observed against the tumorigenic MDCK and MCF-7 cancer cell lines, irrespective of unit molecular weight (Mw) and degree of deacetylation (DDA) of ring chitosan. The 5-chloroisatin chitosan TSCs showed better activity than isatin chitosan TSCs against both the cell lines.
... Similarly, the synthesized thiosemicarbazones had two significant stretching bands at the range 1691-16 81 cm −1 and 156 8-1537 cm −1 , respectively, that assigned to v (C = O) and (C = N) [27] . The strong bands due to v (N-N) of thiosemicarbazones appeared at 1155-1126 cm −1 [28] . Strong bands of isatin moieties of thiosmecarbazones appeared at 1300-1251 cm −1 , which were assigned to v (-OCH 3 -) [ 29 , 30 ] (Supplementary data S5-S7). ...
(Z)-N'-(5-methoxy-2-oxoindolin-3-ylidene)thiomorpholine-4-carbothiohydrazide (MeOIstTmor), (Z)-N'-(5-methoxy-2-oxoindolin-3-ylidene)-2,6-dimethylmorpholine-4-carbothiohydrazide (MeOIstDmMor), (Z)-N'-(5-methoxy-2-oxoindolin-3-ylidene)morpholine-4-carbothiohydrazide (MeOIstMor) and (Z)-2-(5-methoxy-2-oxoindolin-3-ylidene)-N,N-dimethylhydrazine-1-carbothioamide (MeOIstDm) were synthesized and characterized by elemental analysis, FT-IR, ¹H NMR, ¹³C NMR, UV-Vis, ESI-HRMS and single crystal X-ray analysis. Molecular docking studies showed that compound MeOIstDmMor interacted strongly with VEGFR2 via hydrogen bonding. The anticancer activities of the synthesized compounds were tested against breast cancer (MCF-7), skin cancer (A431), and lung cancer (A549) for cell viability, cell cycle arrest and western blot analysis. The compounds exhibited significant anticancer potency in micromolar concentration (IC50, 2.52-7.41μM). The compound MeOIstDmMor was found G0/G1 cell cycle arrest in A431 cells and inhibited C-Jun, β-catenin, Akt proteins involve in cell proliferation. Among the four compounds, compound MeOIstDmMor exhibited strong anticancer potency in A549 (IC50, 2.52 μM) than rest of the compounds. Similarly, compound MeOIstMor exhibited high anticancer activity in MCF-7, IC50; 2.93 μM.
... The concentration at the absorbance that is half of the maximum absorbance was obtained as half inhibitory concentration (IC 50 ). 42 The inhibition ratio (IR) was determined using the relation: 40 = IR % control abs sample abs control abs X 100% 48 showed the partial involvement of the NH 2 group of chitosan in the formation of TSCs. The absorption bands at 600 49 and 620−622 cm −1 were attributed to ν (in-plane pyridine ring deformation). ...
Chitosan-functionalized pyridine-based thiosemicarbazones and their copper(II) complexes have been found to own a substantial antiproliferative activity against the tumorigenic Madin Darby canine kidney (MDCK) and MCF-7 cancer cell lines. In the current study, chitosan oligosaccharide (CS) (87% DDA, Mw < 3000 Da) and crab shell chitosan (CCS) (67% DDA, M w 350 kDa) were functionalized as chitosan pyridine-2-thiosemicarbazones and chitosan 2-acetyl pyridine-2-thiosemicarbazones, and their copper(II) complexes were synthesized. The formation of chitosan thiosemicarbazones and their NNS tridentate behavior to give the square planar copper(II) chitosan thiosemicarbazone complexes were established by spectroscopic studies, powder X-ray diffraction, elemental analysis, and magnetic moment measurements. The thermal study showed a marked stability of these derivatives before the outset of chitosan backbone degradation at 200 °C. The colorimetric MTT assay revealed a higher activity of CS thiosemicarbazones, viz., CSTSC series (IC50 375-381 μg mL-1 in the MDCK cell line and 281-355 μg mL-1 in the MCF-7 cell line) than that of high-molecular-weight CCS thiosemicarbazones, viz., CCSTSC series (IC50 335-400 μg mL-1 in the MDCK cell line and 365-400 μg mL-1 in the MCF-7 cell line), showing an enhanced activity with a decrease in Mw and an increase in DDA of constituent chitosan, a higher activity of both of these series of thiosemicarbazones than that of their native chitosan, viz., CS (IC50 370 μg mL-1 in the MCF-7 cell line and >400 μg mL-1 in the MDCK cell line) and CCS (IC50 > 400 μg mL-1 in both cell lines), and a higher activity of the Cu-CSTSC complexes (IC50 322-342 μg mL-1 in the MDCK cell line and 278-352 μg mL-1 in the MCF-7 cell line) and Cu-CCSTSC complexes (IC50 274-400 μg mL-1 in the MDCK cell line and 231-352 μg mL-1 in the MCF-7 cell line) than that of their respective ligands.
... In addition, the Raman spectrum of CuNar-Batho was analyzed and compared with the spectra of the Batho, Nar and CuNar to evaluate the coordination mode of the chloride ligand through the determination of the presence of ν(Cu-Cl terminal ) stretching or the presence of the bridge mode ν(M-Cl-M), because both types of vibrational modes appear out of the FTIR measurement range (Fig. S5). The absence of the band at 320-350 cm −1 region (ν(Cu-Cl terminal )) and the observation of the band at 150 cm −1 associated with chloro-bridge symmetric vibration only for CuNarBatho complex suggested the presence Cu-Cl-Cu bonds (Litos et al. 2007;Joseph et al. 2006). These results are consistent with the coordination of copper(II) ion through the 5-alkoxy and 4-keto groups of the naringenin and the nitrogen atoms of bathophenanthroline ancillary ligand. ...
The development of new anticancer compounds is one of the challenges of bioinorganic and medicinal chemistry. Naringenin and its metal complexes have been recognized as promising inhibitors of cell proliferation, having enormous potential to act as an antioxidant and antitumorigenic agent. Lung cancer is the second most commonly diagnosed type of cancer. Therefore, this study is devoted to investigate the effects of Cu(II), naringenin (Nar), binary Cu(II)-naringenin complex (CuNar), and the Cu(II)-naringenin containing bathophenanthroline as an auxiliary ligand (CuNarBatho) on adenocarcinoma human alveolar basal epithelial cells (A549 cells) that are used as models for the study of drug therapies against lung cancer. The ternary complex shows selectivity being high cytotoxic against malignant cells. The cell death generated by CuNarBatho involves ROS production, loss of mitochondrial membrane potential, and depletion of GSH level and GSH/GSSG ratio. The structure-relationship activity was assessed by comparison with the reported Cu(II)-naringenin-phenanthroline complex. The CuNarBatho complex was synthesized and characterized by elemental analysis, molar conductivity, mass spectrometry, thermogravimetric measurements and UV–VIS, FT-IR, EPR, Raman and ¹H-NMR spectroscopies. In addition, the binding to bovine serum albumin (BSA) was studied at the physiological conditions (pH = 7.4) by fluorescence spectroscopy.
Graphical abstract
... All reagents and solvents were commercially available and used as without further purification. HL was prepared as described in the literature (Rebolledo et al., 2003;Joseph et al., 2006). ...
A new PbII coordination complex [PbL(OAc)], which was readily synthesized from a mixture of Pb(OAc)2·3H2O and 1-(pyridin-2-yl)benzylidene-4-phenylthiosemicarbazide (HL) is reported. The crystal structure analysis of [PbL(OAc)] showed that the PbII cation is N,N′,S-chelated by the tridentate pincer-type ligand L and by the oxygen atoms of the acetate anion. In addition, the metal centre forms Pb⋯O and Pb⋯S tetrel bonds with an adjacent complex molecule, yielding a 1D zigzag polymeric chain, which is reinforced by N—H⋯O hydrogen bonds and π⋯π interactions. These chains are interlinked by C—H⋯py non-covalent interactions, realized between one of the acetate hydrogen atoms and the pyridine rings. According to the Hirshfeld surface analysis, the crystal packing is mainly characterized by intermolecular H⋯H, H⋯C and H⋯O contacts, followed by H⋯N, H⋯S, C⋯C, C⋯N, Pb⋯H, Pb⋯O and Pb⋯S contacts. The FTIR and ¹H NMR spectra of [PbL(OAc)] testify to the deprotonation of the parent ligand HL, while the acetate ligand exhibits an anisobidentate coordination mode as established by means of single-crystal X-ray diffraction and FTIR spectroscopy. Lastly, theoretical calculations at the PBE0-D3/def2-TZVP level of theory have been used to analyze and characterize the Pb⋯O and Pb⋯S tetrel bonds observed in the crystal of [PbL(OAc)], using a combination of QTAIM (Quantum Theory of Atoms in Molecules) and NCIPlot (Non-Covalent Interaction Plot) computational tools.
... Thiosemicarbazones belong to a class of substances well known for their important applications in the research of new drug candidates, due to their broad spectrum of action [2,3]. Some of the biological applications include antitumoral [3,4], antiparasitic [5,6], antifungal [7], antivirals [8], and antibacterial [9,10] activity. ...
Thiosemicarbazones are well known for their broad spectrum of action, including antitumoral and antiparasitic activities. Thiosemicarbazones work as chelating binders, reacting with metal ions. The objective of this work was to investigate the in silico, in vitro, and in vivo toxicity and oxidative stress of 2-acetylpyridine-N(4)-orthochlorophenyl thiosemicarbazone (TSC01). The in silico prediction showed good absorption by biological membranes and no theoretical toxicity. Also, the compound did not show cytotoxicity against Hep-G2 and HT-29 cells. In the acute nonclinical toxicological test, the animals treated with TSC01 showed behavioral changes of stimulus of the central nervous system (CNS) at 300 mg/kg. One hour after administration, a dose of 2000 mg/kg caused depressive signs. All changes disappeared after 24 h, with no deaths, which suggest an estimated LD50 of 5000 mg/kg and GSH 5. The group treated with 2000 mg/kg had an increase of water consumption and weight gain in the second week. The biochemical parameters presented no toxicity relevance, and the analysis of oxidative stress in the liver found an increase of lipid peroxidation and nitric oxide. However, histopathological analysis showed organ integrity was maintained without any changes. In conclusion, the results show the low toxicological potential of thiosemicarbazone derivative, indicating future safe use.
... AC electrical conductivity and dielectric properties of the prepared transition metal complexes were examined. The work was embraced to 7.71 (m, 1H, H-7), 8.31 (s, 1H, H-5), 8.53 (s, 1H, CH]N), 9.14 (s, 1H, H-2), 10.41 (s, 1H, NH), 12.09 (s, 1H, NH). 13 C-NMR: 21.6 (CH 3 [Cu(MCMT) 2 The chemical structures of the obtained metal complexes are represented in Scheme 1. ...
New and stable coordinated compounds have been isolated in a good yield. The chelates have been prepared by mixing Co(ii), Ni(ii), Cu(ii), and Cd(ii) metal ions with (1E)-1-((6-methyl-4-oxo-4H-chromen-3-yl)methylene)thiocarbonohydrazide (MCMT) in 2 : 1 stoichiometry (MCMT : M2+). Various techniques, including elemental microanalyses, molar conductance, thermal studies, FT-IR, 1H-NMR, UV-Vis, and XRD spectral analyses, magnetic moment measurements, and electrical conductivity, were applied for the structural and spectroscopic elucidation of the coordinating compounds. Further, computational studies using the DFT-B3LYP method were reported for MCMT and its metal complexes. MCMT behaves as a neutral NS bidentate moiety that forms octahedral complexes with general formula [M(MCMT)2Cl(OH2)]Cl·XH2O (M = Cu2+; (X = ½), Ni2+, Co2+; (X = 1)); [Cd(MCMT)2Cl2]·½H2O. There is good confirmation between experimental infrared spectral data and theoretical DFT-B3LYP computational outcomes where MCMT acts as a five-membered chelate bonded to the metal ion through azomethine nitrogen and thiocarbonyl sulphur donors. The thermal analysis is studied to confirm the elucidated structure of the complexes. Also, the kinetic and thermodynamic parameters of the thermal decomposition steps were evaluated. The measured optical band gap values of the prepared compounds exhibited semiconducting nature. AC conductivity and dielectric properties of the ligand and its complexes were examined, which showed that Cu(ii) complex has the highest dielectric constant referring to its high polarization and storage ability.
... Here, the obtained f value of the copper(II) complexes from 136−139×10 −4 cm indicating perfect square planar geometry [23]. This was yet again supported by the neutral and 1:1 electrolyte nature of the thiosemicarbazone copper(II) complexes [24]. ...
Objective: In modern years, the biggest dare is to develop new chemotherapeutic agents with high efficiency as well as low toxicity. Hence, to defeat this challenge, extensive endeavors were taken on thiosemicarbazone based metal complexes. Methods: A sequence of nine thiosemicarbazone based diimine copper(II) complexes derived from three sulfur-containing ligands N-methyl-2- ((1-methyl-1H-pyrrol-2-yl)methylene)hydrazinecarbothioamide H(L1), N-ethyl-2-((1-methyl-1H-pyrrol-2-yl)methylene)hydrazinecarbothioamide H(L2), and N-benzyl-2-((1-methyl-1H-pyrrol-2-yl)methylene)hydrazinecarbothioamide H(L3). The molecular structures and coordination possibilities of thiosemicarbazone ligands toward the central metal ions have been validated by analytical and spectral techniques such as molar conductance, elemental analysis, ultraviolet–Vis, Fourier-transform infrared, and electron paramagnetic resonance spectroscopy confirms that the thiosemicarbazones ligands are coordinated to copper through NS’ donor and NN’ donor of diimine. The antimicrobial activity and DNA cleavage effectiveness of thiosemicarbazone derivatives and copper(II) complexes were assessed by disc diffusion and agarose gel electrophoresis methods. Results: All the spectral studies authenticated that the square planar geometry of the thiosemicarbazone copper(II) complexes 1–9. From the results of antibacterial activity against selected Gram-positive (Bacillus thuringiensis) and Gram-negative (Escherichia coli) bacterial strains, complex 8 exhibited noteworthy activity. Interestingly, copper(II) complexes bearing 1,10-phenanthroline (phen) moiety displayed outstanding results together with N(4)-substituted thiosemicarbazone derivatives and causes complete DNA degradation of SC (supercoiled) pUC18 DNA. Conclusion: A variety of substitutions at the thioamide nitrogen atoms have shown potential biological activity. Henceforth, N(4)-substituted thiosemicarbazone based copper(II) complexes virtually reach the effectiveness of conventional chemotherapeutic drugs.
... In the category of N, S-donor ligands, thiosemicarbazones have gained substantial attention due to diversity in the structures of their complexes formed, variety of bonding modes [1][2][3][4][5][6][7][8], carbon metal bond formation [9,10], ability of ion-sensing capability [11][12][13][14], catalytic properties [15][16][17][18] and biological applications [19][20][21][22][23][24]. Additional interest in Ni(II) -thiosemicarbazone complexes has been focused on their role as active sites for hydrogenases [25] as well as for carbon monoxide dehydrogenases [26] containing Ni(II) complexes. ...
Complexes of 4-chlorobenzaldehyde thosemicarbazone (H¹L) with Ni(II), [Ni(¹L)2] 1 and Ag(I), [Ag2(μ-X)2(η¹-S-H¹L)2(PPh3)2] (X = Cl, 2; Br, 3) have been synthesized and characterized by elemental analysis, IR and ¹H NMR spectroscopy. Ag(I) complexes, containing the 4-methylbenzaldehyde thiosemicarbazone (H²L) ligand complexes [Ag2(μ-X)2(η¹-S-H²L)2(PPh3)2] (X = Cl, 4; Br, 5) have also been synthesized. Complexes 1, 3 and 4 are also characterized by single crystal crystallography to investigate the effect of substituent at phenyl ring of the thiosemicarbazone on the bonding behavior of these Ag(I) complexes. H¹L and its Ni(II) complexes were evaluated for their anti-tubercular activities and it was found that the anti-TB actitivy of H¹L was enhanced on complexation with Ni(II) for complex 1. Molecular docking of H¹L and its nickel complex has also been examined. The results of these studies support the molecular design of the these molecules and have provided a significant background to further examine their antitubercular activity.
... The Cu-N amine and Cu-N py distances are almost equal to each other. Furthermore the bond angles N1-Cu-N2 83.41(8)°and N3-Cu-N4 83.39 (8)°deviate only slightly from the ideal 90°for regular square planar geometry [57]. The angle (θ) between the N1-Cu-N2 and N3-Cu-N4 planes is found to be 17.64°rather than 0°for a regular square plan. ...
... Moreover, it enhances the delocalization of π-electrons over the chelating ring system as well as lipophilicity of the complexes. 28 This might enhance the penetration of lipid layer and therefore affects the growth of the microorganisms. ...
This present work deals with the synthesizes of nine novel thiosemicarbazone copper(II) complexes {[Cu(L)2]Cl C3, [Cu(L)(bpy)]Cl C4–C6, [Cu(L) (phen)]Cl C7–C9 (where, L = H(L1)–H(L3), H(L1) = (E)-N-methyl-2- -(1-phenyl-2-((5-(pyridin-3-yl)-4H-1,2,4-triazol-3-yl)thio)ethylidene)hydrazinecarbothioamide, H(L2) = (E)-N-ethyl-2-(1-phenyl-2-((5-(pyridin-3-yl)-4H- -1,2,4-triazol-3-yl)thio)ethylidene) hydrazinecarbothioamide, H(L3) = (E)-N- -phenyl-2-(1-phenyl-2-((5-(pyridin-3-yl)-4H-1,2,4-triazol-3-yl)thio)ethylidene) hydrazinecarbothioamide, bpy = 2,2′-bipyridyl and phen = 1,10-phenanthroline) with improved pharmacological results. The synthesized complexes were characterized by various spectral-analytical techniques. The structure of the copper(II) complexes C1–C9 was proposed by EPR spectroscopy. It confirmed the square planar coordination around Cu(II) complexes. The antibacterial screening of the complexes revealed that complexes C7 and C8 demonstrated significant activity against Gram-positive (B. thuringiensis) and Gram-negative (E. coli) bacteria. The concentration-dependent DNA cleavage activity of supercoiled (SC) pUC18 DNA exhibited complete DNA degradation effect on complex C6 at a minimum concentration of 40 μM. In vitro cytotoxic results showed that the mixed ligand copper(II) complexes C4, C5 and C7 exhibited higher effects on human cervical cancer cell lines, HeLa, when compared to cisplatin. Hence, the results obtained from each biological screening indicated the superior biological efficacy of the mixed ligand copper(II) complexes bearing diimine moieties. It could be considered as a promising alternative to an existing anticancer drug.
... The ligand exhibits a broad band around 36,000 cm -1 assigned to the π'→π* transition of pyridyl ring and imine function of the thiosemicarbazone moiety. The shift of the π'→π* bands to the longer wavelength in complexes is a result of decrease of C=S bond order due to conjugation following complexation [15]. The peak at about 25,000 cm -1 for the free ligand is attributed to n→π* transition corresponding to the transition of the thioamide function. ...
A tridentate N,N,S-donor ligand, 2-benzoylpyridine-N(4),N(4)-(N,N-diethyl-N-methylamine-2,2'-diyl)thiosemicarbazone (Hbptsc) has been synthesized and characterized by elemental CHN analysis, UV-visible, FT-IR and 1H NMR spectroscopy. Copper(II) complexes of the ligand, Hbptsc synthesized have been characterized by elemental analysis, UV-visible spectra, FTIR spectra and EPR spectroscopic simulation. The complexes hold the stoichiometry of the type [CuLX] where X= Cl (1), NO3 (2), SO4 (3), N3 (4), SCN (5) confirmed by the molar conductivity studies of 10-3 M solutions in DMF at room temperature. The EPR spectra of the complexes recorded in DMF at 77 K shows an axial type spectra with two distinct g-values, g|| and g⊥ indicating a four coordinated planar geometry. The antimicrobial studies of the copper(II) complexes shows an appreciable activity against both gram positive and gram negative bacteria using streptomycin as positive control. The short term in vitro cytotoxicity studies following trypan blue dye exclusion method exhibits pronounced activity against the Dalton’s Lymphoma Ascites tumour cells extruded from the peritoneal cavity of mice.
Mononuclear later first-row transition metal complexes, [M(L)2] (1–4), where M = Co(II) (1), Ni(II) (2), Cu(II) (3), and Zn(II) (4) incorporating 1,8-naphthalimide based ligand were designed. The complex preparation was achieved by reacting metal nitrates with ligand (L) in 1:2 stoichiometry. The ligand and complexes were characterized with analytical and photophysical techniques. Single crystal X-ray diffraction determines that 3 is square planar. The complexes are highly fluorescent compared to the free ligand. The synthesized ligand (L) and complexes (1–4) were screened for their antibacterial activities against gram-positive [Streptococcus mutans (SM), Staphylococcus aureus (SA)] and gram-negative [Escherichia coli (EC), Klebsiella pneumoniae (KL)] bacterial strains. Ni(II) and Cu(II) complexes exhibited good activity against K. pneumonia and S. aureus compared to the free ligand. Particularly effective against gram-negative bacteria (Klebsiella pneumoniae), Ni(II) complex (2) has a MIC value of 6.25 µM and exhibits similar activity to standard ciprofloxacin. Cu(II) complex (3) is two times more effective than the common antibiotic ciprofloxacin with a MIC value of 3.125 µM against gram-positive bacteria (S. aureus).
The Schiff base (3-APT) was a bidentate ligand produced from the condensation between 3-acetylpyridine and the amine group of thiosemicarbazide. Metal chelates were successfully obtained with formulas [Cu(3-APT) 2 X]X, [Ni (3-APT) 2 ]X 2 .H 2 O and [Pd(3-APT)X 2 ] (where 3-APT = 3-acetylpyridine thiose-micarbazone and X = Cl À). The characterization was performed by various physicochemical tools. The studied (3-APT) ligand had two donor sites through both azomethine nitrogen and thiocarbonyl sulfur. The characterization tools observed the presence of two different geometric shapes. The square planar structure in the case of both nickel (II) and palladium (II) chelates and the square pyramidal structure in the case of copper (II) complex. The characterization involved a 1 HNMR study for the (3-APT) ligand and its square pla-nar Pd (II) and Ni (II) chelates. The density functional theory was used to structurally optimize the synthesized ligand and its chelates. The antibacterial activity was evaluated using different types of bacteria showing superior results. The breast (MCF-7) cell line was selected to investigate the cytotoxic effect of formed compounds. The palladium (II) complex was the most cyto-toxic effective compound with the least IC 50 value. Further theoretical molecular docking study was performed to observe the active sites in the selected proteins during their interactions with our compounds. K E Y W O R D S 3-Acetylpyridine, Microbiological screening, Molecular docking, Thiosemicarbazone
The increasing number of patients with diabetes has recently become a serious problem following changes in diet and lifestyle. Various drugs are used to treat diabetes; however, there are serious concerns regarding their physical and mental side eff ects. Zinc, copper, and nickel are trace elements present in the body that are known to have insulin-like eff ects although nickel is not essential to mammals. Here, we focused on metal complexes with the 2-acetylpyrazine N(4)-phenylthiosemicarbazone (2-APTC) ligand, which has a six-coordinate octahedral structure with an S 2N4-type coordination mode. For single oral administration experiments, [Zn(2-APTC)2], zinc sulfate (10 mg Zn/kg) and [Cu(2-APTC)2], and copper sulfate (3 mg Cu/kg) were orally administered to 5-week-old ddy mice fasted for 12 h. Moreover, of [Zn(2-APTC) 2] was administered daily to KK-A y mice, a type 2 diabetes model. In a single oral administration experiment, [Zn(2-APTC) 2] showed a signifi cant increase in plasma zinc concentration compared to zinc sulfate. Moreover, the 28-d administration of [Zn(2-APTC) 2] resulted in a signifi cant decrease in the blood glucose level. This suggests that [Zn(2-APTC) 2] has a higher absorption of the complexes than [Cu(2-APTC)2] after oral administration and is expected to have more antidiabetic activity. However, blood urea nitrogen, aspartate aminotransferase, and alanine transaminase levels increased, suggesting that [Zn(2-APTC)2] administration aff ects liver and kidney functions. Moreover, hematoxylin and eosin staining showed that [Zn(2-APTC)2] ameliorated fatty liver and exerted antidiabetic eff ects. Here, we report for the fi rst time that a zinc complex with a six-coordinated octahedral structure, with 2-APTC as a ligand, exhibits antidiabetic eff ects. reg02 [Zn(2-APTC)2] with S2N4 type has antidiabetic eff ects. Tanaka C. et al. Metallomics Research 2023; 3 (2) #MR202302
This review gives a comprehensive account in terms of the synthesis, characterization and biological application of bisthiosemicarbazone ligands and their metal complexes that have been reported until 2022. Their coordination chemistry with p and d block elements, where the structure is solved by single crystal X‐ray crystallography is explored. Complexes are placed group‐wise and their structure as well as bonding aspects are discussed separately. Various spectroscopic techniques for the characterization of ligands and their complexes like infrared (IR), ultraviolet‐visible (UV–Vis), electron spin resonance (ESR), and nuclear magnetic resonance (NMR) (¹H, ¹³C, ³¹P, ⁵⁹Co, ¹¹⁹Hg) are discussed. Complexes formed by bisthiosemicarbazones are generally mononuclear; however, in some cases, binuclear or polynuclear complexes have also been found. Square planar, square pyramidal, octahedral, and pentagonal pyramidal are some of the common geometries exhibited by these complexes. Structure–activity relationship was established for substituted and unsubstituted diimine bisthiosemicarbazone complexes of different metal ions. The effect of co‐ligands on biological activity is also discussed.
Three new copper(II) complexes, [Cu(1,10-Phen)(L)] (1), [Cu(2,2'-Bpy)(L)] (2) and [Cu(3,4-Lut)(L)] (3), where H2 L=2-[(2,4-dihydroxyphenyl)methylidene]-N-(prop-2-en-1-yl)hydrazine-1-carbothioamide, 1,10-Phen=1,10-phenanthroline, 2,2'-Bpy=2,2'-bipyridine, 3,4-Lut=3,4-lutidine, have been synthesized and characterized by elemental analysis, FTIR spectroscopy and single crystal X-ray crystallography (1, 2). All compounds are mononuclear. The introduction of a monodentate N-heteroaromatic base (3,4-dimethylpyridine) has led to a significant increase of antimicrobial activity against Gram-negative Escherichia coli and antifungal activity against Candida albicans compared to the pro-ligand and the precursor complex [Cu(L)H2 O]. The introduction of bidentate N-heteroaromatic bases did not lead to such increase of antimicrobial and antifungal activities. Moreover, complex 3 surpasses the inhibitory activity of tetracycline toward Enterobacter cloacae and the inhibitory activity of fluconazole toward Candida parapsilosis and Cryptococcus neoformans. The study of antioxidant activity against cation radicals ABTS⋅+ showed that complexes 1-3 are more active than Trolox, but only introduction of the monodentate N-heteroaromatic base (3,4-dimethylpyridine) led to the increase of antioxidant properties compared to the precursor complex.
Five novel cobalt complexes of pyridine-based heterocyclic thiosemicarbazones [Co(BpT)2]Cl (1), [Co(BpT)2](NO3)•(H2O) (2), [Co(ApT)2]Br•(CH3OH) (3), [Co(BpT)2]Br (4) and [Co(BpT)(OAc)(H2O)2]•2(H2O) (5) have been synthesized (where, HBpT = 2-benzoylpyridine-N⁴-methylthiosemicarbazone, HApT = 2-acetylpyridine-N⁴-phenylthiosemicarbazone) and characterized by analytical and spectroscopic methods. The ligands form monodeprotonated anions in all the complexes to coordinate via thiolate S, azomethine and pyridyl N atoms. The central cobalt metal in the complexes 1, 2, 3 and 4 were found to be in the +3 oxidation state, while in the complex 5 it was found to be in the +2 state. The structures of the complexes 1, 2 and 3 were confirmed by single crystal X-ray diffraction (SCXRD) technique and all of them were crystallized in monoclinic lattices with P21/n space group. The intermolecular interactions were quantified by Hirshfeld surface (HS) analysis. Further, the nature of frontier orbitals and stability of the complexes were theoretically analyzed, and the electrostatic potential plots were mapped on optimized geometries by using computational methods. The complexes 3 and 4 are related by interchanging the phenyl and methyl groups in the thiosemicarbazone moiety. In silico molecular docking study with B-DNA reveals the importance of various interactions and the positioning of the phenyl group. The cobalt(III) complex (3) cation with phenyl group at the N⁴ position is found to have a higher binding tendancy against the therapeutic target B-DNA with docking energy of -9.16 kcal/mol.
In this study, firstly, 22 thiosemicarbazone derivatives (3a-y) were synthesized. Then, ADME parameters, pharmacokinetic properties, drug-like structures, and suitability for medicinal chemistry of these molecules were studied theoretically by using SwissADME and admetSAR programs. According to the results of these theoretical studies, it can be said that the bioavailability and bioactivity of these compounds may be high. In silico molecular docking between ligands (thiosemicarbazone derivatives) and targeted proteins (protein-78 (GRP78) for C6 and quinone reductase-2 (4ZVM for MCF 7) was analyzed using Hex 8.0.0 docking software. According to the docking data, almost all molecules had higher negative E values than Imatinib (already used as a drug). For this, in vitro anticancer studies of these molecules were done. The cytotoxic activities of thiosemicarbazone derivatives (3a-y) were evaluated on C6 glioma and MCF7 breast cancer cell lines at 24 h, and Imatinib was used as the positive control. According to the results of the cytotoxicity assay, it can be said that the five compounds (3b, c, f, g, and m with IC50 = 10.59–9.08 μg/mL; Imatinib IC50 = 11.68 μg/mL) showed more potent cytotoxic activity than Imatinib on C6 cell line. Together with to these results ten compounds (3b, d, f, g, I, k, l, m, n, and r with IC50 = 7.02–9.08 μg/mL; Imatinib IC50 = 9.24 μg/mL) had a more effective cytotoxic activity against MCF7 cell line than Imatinib. Compound 3 m showed the highest antiproliferative effect against C6 and MCF7 cell lines.
The 1:1 reaction of (Z)-Ń-{(2-hydroxynapthalen-1-yl}methylene)acetohydrazide (HL) and copper(II) salt in methanol yields a series of new mononuclear complexes, [Cu(HL)(OH2)]ClO4 1, [Cu(HL)(OH2]ClO4 2, [Cu(HL)(OH2)]NO3 3 and [Cu(L)(Cl)] 4. The room temperature magnetic moments of the complexes 1-4 are 1.79, 1.78, 1.80 and 1.76 B.M. respectively. The absorption bands emerging in the UV region (337-341 nm) are characteristic of the HL ligand. In these complexes, the LMCT bands were observed in the range of 503-506 nm and the d-d band at 617-623 nm. The molecular structures of all four complexes have been solved using single-crystal X-ray analysis. The X-ray analysis shows the formation of supramolecular structures through various non-covalent interactions viz., C-H∙∙∙π and π···π intermolecular interactions. The detailed Hirshfeld surface and fingerprint plots yielded a comparative picture of the mode of non-covalent interactions. The DFT calculations were performed and the results are in good agreement with experimental results. X-band epr spectral measurements have been carried out to authenticate the paramagnetic behavior of all complexes. The stability of the copper(II) centre was examined using cyclic and differential pulse voltammetry. The IC50 and SOD activity values for all complexes reveal that they are good models among the best values reported for low molecular weight mononuclear copper(II) complexes.
Transition metal catalysts play an important role for synthesis of industrially and laboratory important organic fine chemicals to control the selectivity, activity and stability. In this review, we focus on mainly transition metal based supported catalyst, mainly oxide supported catalyst for heterogeneous catalytic hydrogenation and oxidation of some synthetically important organic molecules. First we discuss the industrially important catalytic organic synthetic reactions. This is followed by the role of supported metal catalysts in the heterogeneous synthetic catalytic reactions with specific attention to hydrogenation and oxidation of organic molecules. The role of base metals and noble metals in monometallic and bimetallic catalysts are then discussed. Some synthetic routes for preparation of oxide supported metal catalysts are also discussed. Finally, a general discussion of the metal-support interaction (MSI) in oxide supported metal catalysts is made.
In this paper, two ternary copper(II) complexes having the general formula [Cu(HL)(X)] have been synthesized by reacting equimolar solutions of Cu(ClO4)2·6H2O, HL and X (HL = (Z)-N′-{(2-hydroxynaphthalen-1-yl}methylene)acetohydrazide], X = 2,9-dimethyl-1,10-phenanthroline (DMPHEN) and BZI = benzimidazole) in methanol. The complexes have been characterized by microanalysis (C, H and N), magnetic susceptibility and spectral (IR, UV–Vis and X-band epr) measurements. The molecular structures of both complexes have been determined by single-crystal X-ray diffraction analysis. Most interestingly, complex 1, which contains of both hydrogen bonding and π∙∙∙π (chelate-chelate) interactions, forms a supramolecular architecture. Hirshfeld analysis and fingerprint plots verified weak CH∙∙∙π and π∙∙∙π non-covalent interactions that lead both complexes to build supramolecular architectures. To relate to the experimental environment, TD-DFT calculations have been carried out. The TD-DFT findings suggest that transitions in the lowest-energy region are mixed absorption bands with d-d and ligand to metal transitions (LMCT). Room temperature magnetic measurements have been performed to disclose the paramagnetic nature of the complexes. An X-band epr spectral study has been carried out to verify the paramagnetic and bonding behavior of both complexes. The stability of the metal center was explored using electrochemical (cyclic voltammetry and differential pulse voltammetry) techniques. In addition, the superoxide dismutase activities of both complexes have been evaluated using nitro blue tetrazolium assays at pH 7.4. The SOD activity data rank among the best values reported for low molecular weight mononuclear copper(II) complexes reported in the literature.
A new bidentate Schiff base ligand (ATBS [4‐bromo‐2‐(thiazole‐2‐yliminomethyl)phenol]) was synthesized via the condensation reaction of 2‐aminothiazole with 5‐bromosalicylaldehyde in ethanol. The reaction of ATBS with transition metal salts of Cu(II), Co(II), Ni(II), and Mn(II) afforded the corresponding ATBS–M complexes. Results from physicochemical and spectral analyses, such as elemental analysis, infrared, UV–Vis spectroscopy, magnetic susceptibility, and molar conductance, revealed a nonelectrolytic nature with octahedral (Oh) geometry and a metal/ligand ratio of 1:2 for Cu(II), Co(II), and Ni(II), but 1:1 for the Mn(II) complex. The density functional theory (DFT) calculations are correlated very well with the proposed structure and molecular geometry of the complexes as [M(ATBS)2] (M = Cu, Co, and Ni) and [Mn(ATBS)(H2O)2]. Significantly, the prepared compounds showed strong inhibition activity for a wide spectrum of bacteria (Escherichia coli, Bacillus subtilis, and Staphylococcus aureus) and fungi (Candida albicans, Aspergillus flavus, and Trichophyton rubrum), with the ATBS–Ni complex being the most promising antibiotic agent. Molecular docking studies of the binding interaction between the title complexes with the bacterial protein receptor CYP51 revealed clear insights about the inhibition nature against the studied microorganisms, with the following order: ATBS–Cu > ATBS–Mn > ATBS–Ni > ATBS–Co for complex stability. Moreover, the cytotoxicity measurements of all prepared metal complexes against the colon carcinoma (HCT‐116) and hepatocellular carcinoma (Hep‐G2) cell lines showed exceptional anticancer efficacy of the complexes as compared with the free ATBS Schiff base ligand. Significantly, the results attested that ATBS–Cu is the most effective complex against HCT‐116 cells, whereas ATBS–Mn has the highest cytotoxic efficiency against Hep‐G2 cells. Furthermore, electronic spectra, viscosity measurements, and gel electrophoresis techniques were employed to probe the interaction of all prepared ATBS–metal complexes with calf thymus (CT)‐DNA. Results confirmed that all complexes are strongly bound to CT‐DNA via intercalation mode, with the ATBS–Co complex having the highest binding ability.
Copper(II) complexes of 2-hydroxyacetophenone-N(4)-cyclohexylthiosemicarbazone (H2L1) and 2-hydroxyacetophenone-N(4)-phenylthiosemicarbazone (H2L2) have been synthesized and characterized by different physicochemical techniques like magnetic studies and electronic, infrared and EPR spectral studies. [(CuL1)2] (1) is a dinuclear complex having four coordination around copper(II) with distorted square planar geometry. The two individual dinuclear complexes are interconnected through two bifurcated classical hydrogen bond interactions producing a sheet-like structure along b axis. [(CuL2)2]·1/2H2O (2) also has a dimeric structure. The thiosemicarbazones bind to the metal as dianionic ONS donor ligand in all the complexes, except in the complexes [Cu(HL1)Cl]·2H2O (3), [Cu(HL1)Br]·4H2O (4) and [Cu(HL1)NO3]·C2H5OH(H2O) (5), where the ligand moieties are coordinated as monoanionic (HL¯) ones. Complexes [CuL1dmbipy] (6), [CuL2dmbipy]·3H2O (7), [CuL2bipy]·H2O (8) and [CuL2phen]·2C2H5OH (9) are heterocyclic base adducts. The synthesis and characterization of monomeric and dimeric Cu(II) complexes with 2-hydroxyacetophenone-N(4)-cyclohexyl/phenyl substituted ONS donor ligands is described. It also reports the crystal structure of a novel binuclear Cu(II) complex with oxygen bridging and its interesting coordination. This compound [CuL1]2 is a rare example of copper(II)-thiosemicarbazone complex with oxygen bridging structure.
The synthesis and solid state structural, spectral and electrochemical solution characterization of [Cu(L)(acpy)]ClO4 1 and [Cu(L)(NO3)] 2 [where L = N'-[(E)-phenyl(pyridin-2-yl)methylidene]thiophene-2-carbohydrazide and acpy = 2,6-Diacetylpyridine] have been done by elemental analysis, UV–vis, FTIR, electrochemical techniques (CV and DPV) and electron paramagnetic resonance (epr) spectroscopy. The single crystal structures were solved by the X-ray diffraction technique. In complex 1, copper ion is in a distorted octahedral environment. The geometry of copper(II) in complex 2 is distorted square pyramidal (τ = 0.201). The mono deprotonated, HL ligand act as a tridentate to a copper(II) ion. On the basis of density functional theory (DFT) calculation, the electronic excitations involve transitions mainly from metal ligand bonding mostly the α-LUMO within the dominant Cu dxy character and to α-LUMO+1. Epr spectra for polycrystalline samples showed the copper(II) hyperfine features as well as half-field signal which are appropriate for ΔMs = ±2 of dimers. Presence of half-field signal in 1 is due to solid-solid interaction (intra-molecular) where as in 2 the nature of interaction is intra-molecular. The antioxidant superoxide measurements show that the both complexes 1 and 2 behave as superoxide mimic in alkaline nitro blue tetrazolium chloride assay.
COTI-2 is a novel anticancer thiosemicarbazone in phase I clinical trial. However, the effects of metal complexation (a main characteristic of thiosemicarbazones) and acquired resistance mechanisms are widely unknown. Therefore, in this study, the copper and iron complexes of COTI-2 were synthesized and evaluated for their anticancer activity and impact on drug resistance in comparison to metal-free thiosemicarbazones. Investigations using Triapine-resistant SW480/Tria and newly established COTI-2-resistant SW480/Coti cells revealed distinct structure–activity relationships. SW480/Coti cells were found to overexpress ABCC1, and COTI-2 being a substrate for this efflux pump. This was unexpected, as ABCC1 has strong selectivity for glutathione adducts. The recognition by ABCC1 could be explained by the reduction kinetics of a ternary Cu-COTI-2 complex with glutathione. Thus, only thiosemicarbazones forming stable, nonreducible copper(II)-glutathione adducts are recognized and, in turn, effluxed by ABCC1. This reveals a crucial connection between copper complex chemistry, glutathione interaction, and the resistance profile of clinically relevant thiosemicarbazones.
New ONS hydrazone ligand, 2‐[(2‐aminochromon‐3‐yl)methylidene]‐N ‐phenylhydrazinecarbothioamide, HL , was synthesized and reacted with different salts of Cu (II) ion (OAc⁻, NO3⁻, SO4²⁻ and Cl⁻) in absence and presence of secondary ligands (L′); 8‐hydroxyquinoline, 1,10‐phenanthroline or SCN⁻; to form binary and ternary Cu(II)‐chelates. The ligand and its Cu(II)‐complexes were fully characterized by analytical, spectral, thermal, conductivity and magnetic susceptibility measurements. The metal chelates showed octahedral, square planar and /or distorted tetraherdal arrangements. Coats–Redfern equations used to calculate the kinetic parameters of the thermal decomposition stages (Ea, A, ΔH, ΔS and ΔG). The compounds exhibit luminescence property; promising interesting potential applications as photoactive materials. Lippert–Mataga, Bakhshiev, Kawski–Chamma–Viallet and microscopic solvent polarity parameter and ETN correlation methods were applied on the solvatochromic shifts of emission spectra to evaluate the ground (μg) and excited (μe) states dipole moments. Excited state dipole moment is larger than the ground state which may be attributed to π‐π* transition. The coordinating anions play an important role on the position and intensity of emission band. The ligand and its metal complexes showed antimicrobial activity towards Gram–positive bacteria, Gram–negative bacteria, yeast and fungus. The molecular structural parameters of HL and its Cu(II)‐ complexes have been calculated on the basis of DFT engaged in the Gaussian 09 program at the B3LYP/6‐31G(d,p) level; the theoretical data are correlated with the experimental data.
Four new heteroleptic silver(I) complexes with the general formula [Ag(L1–4)(nap)] (1–4), where L1–4 = 2-(1-(4-substitutedphenyl)ethylidene)hydrazinecarbothioamide and nap = naproxen, have been synthesized and characterized. The geometric parameters determined from density functional theory and UV-Vis studies indicate distorted tetrahedral geometry around silver(I) ion. Fourier transform infrared (FT IR) spectra evidenced asymmetric bidentate coordination mode of carboxyl oxygen atoms of naproxen with silver(I) ion. The complexes are stable for 72 h and biocompatibility was analysed towards normal human dermal fibroblast cells, which showed non-toxic nature up to 100 ng/ml. In vitro anti-proliferative activity of the complexes by MTT assay was tested against three human cancerous cell lines and one non-tumorigenic human breast epithelial cell line (MCF-10a) in which the complex 4 exhibited enhanced activity. The morphological changes observed by acridine orange/ethidium bromide and Hoechst 33258 staining method reveal apoptosis-inducing ability of the complexes. The molecular docking studies suggest hydrogen bonding, hydrophobic and π-pair interactions with the active site of epidermal growth factor receptor, vascular endothelial growth factor receptor 2 and lipoxygenase receptors.
The development of biocompatible fluorescent materials based on CdII (d¹⁰) systems for cytotoxic application and latent fingerprint detection under UV illumination has not yet been studied that thoroughly. In this sense, this work presents production of novel and dual nature pure Cd (II) phosphor complex based on ρ‐dimethylaminobenzaldehyde thiosemicarbazone ligand (H‐DMABTS). The structural characterization confirms that the ligand which acts as monoanionic bidentate through NS donor sites, forming mononuclear complex formulates as: [Cd (DMABTS)2(C2H5OH)2] where, DMABTS = anionic form of ρ‐dimethylaminobenzaldehyde thiosemicarbazone. TEM analysis shows that Cd (II) complex has sheet like shape in micro scale. Moreover, the Cd (II) complex was dispersed into silica host. Photoluminescence emission and lifetime of H‐DMABTS ligand, Cd (II) complex and Cd (II) complex dispersied into silica were measured. Cd (II) complex is intensive luminescent with impressive visual emission under UV excitation. All fluorescent materials were tested for their in vitro cytotoxicity against HepG‐2 cell line. The Cd (II) phosphor complex shows higher activity (IC50 = 0.005 μM) than other prepared materials and different standard antitumor drugs. Furthermore, the Cd (II) phosphor complex has a lower toxicity value (LD50 = 130 mg/Kg) relative to the standard cis‐platin (LD50 = 13.5 mg/Kg). Moreover, latent prints details, including their characteristic three levels, have been clearly identified from various forensic substrates (non‐porous, semi‐porous, porous) using Cd (II) phosphor complex.
The (E)-N′-(2-hydroxybenzylidene)morpholine-4-carbothiohydrazide (H2L) ligand and its chelates with Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) have been synthesized. Analytical and spectral data prove that the ligand acts a monobasic tridentate ligand coordinated via deprotonated phenolic O, azomethine N and thione S atoms (ONS chromophore) with cobalt(II), nickel(II) and copper(II) salts leading to two fused five and six-membered chelate rings. While with zinc(II) and cadmium(II) salts the ligand behaves as a neutral bidentate and coordinated through the azomethine nitrogen and thione sulfur (NS type). The percent of weight losses during thermal degradation processes are in agreement with the proposed formulae as indicated by the TG/DTG studies. The X-ray diffraction patterns (XRD) indicate nano-sized particles and crystalline nature of the free organic ligand as well as all of its metal complexes. The corresponding predicted spectral data of H2L and its metal chelates were calculated in the Polarizable Continuum Model (PCM) using DFT and DT-DFT methods at the B3LYP/LanL2DZ level of theory. The obtained results showed a relatively good agreement between the experimental and predicted spectral data. The in vitro antibacterial and antifungal properties of the H2L and its metal complexes against four bacteria, Gram-positive (Staphylococcus aureus and bacillus subtilis) and gram-negative (Escherichia coli and proteus vulgaris) and two strains of fungus (Aspergillus fumigatus and candida albicans) showed that metal chelates exhibit more inhibitory effects than the free ligand. Selectivity is detected in the activities of some compounds over certain microorganisms, which is important for future pharmaceutical applications.
A number of alternatives were made to overcome numerous life-threatening infectious diseases by metal-based anticancer compounds. At present, thiosemicarbazones and their metal complexes have received significant consideration as a result of their metal DNA-interaction, structural diversity and availability of bonding modes. In this study, the coordination characteristics of nine diimine copper(II) complexes with sulfur containing ligands, [Cu(L)2] (1–3), [Cu(L)(bpy)]Cl (4–6) and [Cu(L)(phen)]Cl (7–9) (L = H(L1)–H(L3), phen = 1,10-phenanthroline, bpy = 2,2′-bipyridyl, H(L1) = (Z)-2-((4-methoxynaphthalen-1-yl)methylene)-N-methylhydrazinecarbothioamide, H(L2) = (Z)-N-ethyl-2-((4-methoxynaphthalen-1-yl)methylene)hydrazinecarbothioamide and H(L3) = (Z)-2-((4-methoxynaphthalen-1-yl)methylene)-N-phenylhydrazinecarbothioamide] have been synthesized from 4-methoxy-1-naphthaldehyde along with N(4)-substituted thiosemicarbazide derivatives. The synthesized ligands and their Cu(II) complexes were characterized through different spectroscopic techniques and square-planar coordination was proposed. Biological evaluation such as DNA-cleavage, antibacterial and in vitro cytotoxicity of thiosemicarbazone ligands and their resultant Cu(II) complexes were analyzed. Interestingly, Cu(II) complex containing heteroaromatic moiety 9 had potential cytotoxic activity with strong DNA-interaction. In the future, these may be helpful to design more effective novel chemotherapeutic drugs.
The basic interest in the present study pertains to developing metal based antimicrobial agents, as several microorganism have built resistance to the conventional drugs. In this respect, reactions of 2-acetylpyridine-N1-substituted thiosemicarbazones, {(C5H4N4) -(CH3)C2= N3–N2(H)–C1(=S)-N1HR} (abbrev. HL3R : R = H, Me, Et, Ph) with copper(I) halides in equimolar ratios have been carried out and consequently mononuclear copper(II) complexes, [CuIIX(N4,N3,S-L3R] (R = H, Me, Et, Ph; X = Cl, 1-4; Br, 5-8; I, 9-12) have been isolated. The formation of these complexes with CuII-halogen bonds, especially with iodide anion, occurred via. proton coupled electron transfer mechanism (PCET), which involved simultaneous release of electron from CuI to combine with proton from- N2H- moiety and metal itself converting to CuII. The analytical data, spectroscopy (IR, ESR, UV-visible, ESI-mass) and x-ray crystallography confirmed their molecular structures. These pseudo square planar copper(II) complexes have been tested for their antimicrobial activity against methicillin resistant Staphylococcus aureus (MRSA) bacteria, Staphylococcus aureus (MTCC740), Klebisella pneumonia 1 (MTCC-109), Salmonella typhimurium 2 (MTCC1251) and Candida albicans (MTCC 227). Specifically, the antimicrobial activity against MRSA, Klebisella pneumonia 1 (MTCC-109) and Candida albicans (MTCC 227) is comparable to or better than that of the reference compounds gentamicin and amphotericin B. Significantly, several complexes have shown in vitro high cell viability (88-92%) determined using MTT assay {MTT = 3-[(4,5-dimethylthiazol-2-yl)-2,5-diphenyl] tetrazolium bromide}.
Synthesis and characterization of three nickel complexes [NiCl(L1)] 1, [NiCl(L2)] 2 and [NiCl(L3)] 3 are described {HL1 = 4‐(2,5‐dimethoxyphenyl)‐1‐((pyridin‐2‐yl)methylene)thiosemicarbazide, HL2 = 4‐(3‐nitrophenyl)‐1‐((pyridin‐2‐yl)methylene)thiosemicarbazide and HL3 = 4‐(2,4‐dimethoxyphenyl)‐1‐((pyridin‐2‐yl)methylene)thiosemicarbazide} and among the tridentate ligands HL3 is reported for the first time. The structures of the complexes were assigned based on CHNS microanalysis, spectroscopic (IR & UV–Vis.) data and solution conductivity studies. The absence of any magnetism for the complexes proved their square planar geometry. Single crystals of complex 1 were grown and analyzed by XRD analysis which confirmed the complex planarity as each Ni atom connects to three (two nitrogen and one sulfur) atoms from the thiosemicarbazone ligand and an additional chlorine atom. Packing of the complex 1 in the crystal lattice was proved to stabilize via intermolecular hydrogen bonds. Antimicrobial activities of 1–3 were studied in vitro against fungal and bacterial species and, in several instances, the complexes possessed improved antibacterial behavior in comparison to chloramphenicol. Three square planar nickel – thiosemicarbazone complexes have been prepared for the first time and one of them was characterized by means of X‐ray single crystal analysis which revealed the Ni coordination to three atoms from the thiosemicarbazone ligand and additional chlorine atom. The complexes, in many instances, displayed improved antibacterial properties in comparison to the chloramphenicol standard.
This research work was emphasized about synthesis of mixed ligands of Co(II), Ni(II), Cu(II) and Zn(II) complexes of the type [M(L)(phen)] 1–4 and [M(L)(bpy)] 5–8 where, L = potassium (S, E)-2-((5-bromo-2-hydroxybenzylidene)amino)propanoate (derived from 5-bromosalicylaldehyde and L-alanine), phen = 1, 10 phenanthroline and bpy = 2, 2′-bipyridyl. Both phen and bpy act as an auxiliary ligand. The synthesized metal(II) complexes characterized by a spectral technique like CHN analysis, electronic spectroscopy, FT-IR, NMR, ESI-Mass spectrometry, EPR, Powdered X-ray diffractometry, and cyclic voltammetry. From spectral arguments, the geometry of complexes displayed five coordination through Schiff base ligand (ONO) and diimine (NN) donor and expected to give the distorted square pyramidal geometry around metal atoms. In vitro cytotoxicity of the Cu(II) complexes (3 and 7) were checked by MTT assay towards three cancer cell lines such as human lung cancer (A549), cervical cancer (HeLa), human breast cancer (MCF-7) and one normal cell line like nontumorigenic human dermal fibroblast cell line (NHDF). The cell viability of those complexes showed an only a moderate effect on cancerous cells when compared with the drug cisplatin. In the molecular docking studies, all the metal(II) complexes showed hydrogen bond, hydrophobic and π-π stacking interaction with active sites of human thymidylate synthase receptor. Furthermore, Frontier molecular orbital analysis (HOMO-LUMO) was accomplished by Density functional theory using B3LYP/3-21G*++ basis sets to understand the chemical stability of the complexes.
Six new copper(II) complexes of 2-benzoylpyridine N(4)-cyclohexyl thiosemicarbazone (HL) have been synthesized and characterized by different physicochemical techniques like molar conductivity measurements, magnetic studies and electronic, infrared and EPR spectral studies. Five of the complexes have been found to possess the stoichiometry [CuLX], where X = CI (1), Br (2), NO3 (3), NCS (4), N-3 (5). The complex prepared from copper sulfate has the composition [Cu2L2SO4] . (H2O)(2) (6). In all the complexes the deprotonated ligand, L and the anion (Cl-, Br-, NO3-, NCS-, N-3(-), SO42-) were found to be coordinated to the Cu(II) ion. The terdentate nature of the ligand is evident from the IR spectra. The metal ligand bonding parameters evaluated from the EPR spectra indicate strong in-plane sigma and in-plane pi bonding. The magnetic and spectroscopic data indicate a square planar geometry for complexes I, 3, 4 and 5, while the complexes 2 and 6 are assigned a square pyramidal geometry. Crystal structure of the complex [CuLCI] reveals two molecules per asymmetric unit of a monoclinic lattice, with space group symmetry P2(1)/n. The complexes [{CuLBr}(2)] (2) and [CuLNCS] (4) crystallized into triclinic lattices with space group P1. Compound 2 exists as a thiolate bridged copper(II) dimer. The antimicrobial activity of the ligand and the copper complexes were tested against five types of bacteria isolated from clinical samples. The complexes were found to be active against Bacillus sp., Vibrio cholera OI, Staphylococcus auras and Salmonella paratyphi.
Four binuclear complexes [Cu(dptsc)Cl]2 · 3H2O (1), [Cu(dptsc)Br]2 (2), [Cu(dptsc)(μ-N3)]2 (3) and [Cu(dptsc)(NO3)]2 · H2O (4) (where Hdptsc = di-2-pyridyl ketone N(4)-methyl, N(4)-phenylthiosemicarbazone) have been synthesized and physicochemically characterized. Each Cu(II) atom in the monomeric unit exists in a penta-coordinate environment. The molecular structures of [Cu(dptsc)Br]2 and [Cu(dptsc)(μ-N3)]2 are resolved by single-crystal X-ray diffraction studies. Both the crystals are centrosymmetric dimers where each ligand unit coordinates through one of the pyridyl nitrogens, azomethine nitrogen and thiolate sulfur to Cu(II). A distorted square pyramidal geometry is observed around Cu(II) for both the complexes, where the N(2) nitrogen of the second ligand unit coordinates to the first Cu(II) center in compound 2 and N(6) nitrogen of the azido group bridges both the Cu(II) centers in compound 3. Spectral characterization corroborate the structural studies.
Three novel iron(III) complexes of 2-benzoylpyridine N(4), N(4)-(butyl-1,4-diyl) thiosemicarbazone (HBpypTsc), [Fe(BpypTsc)2]ClO4 (1), [Fe(BpypTsc)2]NO3 (2) and [Fe(BpypTsc)2]FeCl4 (3) were synthesized and physico-chemically characterized by means of partial elemental analyses, magnetic measurements (polycrystalline state), UV–Vis and IR spectroscopies. The spin Hamiltonian parameters, isomer shifts and quadrupolar splitting values of the complexes were assigned by variable temperature EPR and Mössbauer spectra. The presence of a spin-paired iron(III) cation with dxz2dyz2dxy1 ground state is revealed by the simulated EPR spectral data. The structures of the free ligand HBpypTsc and one of the complexes [Fe(BpypTsc)2]FeCl4 (3) were solved by single crystal X-ray diffraction which authenticated a FeN4S2 octahedral coordination in the complex, as envisaged from the spectral data. All complexes except [Fe(BpypTsc)2]FeCl4 (3) were found to be low-spin S=1/2 (2T2g), whereas 3 was found to have both low-spin (2T2g) and high-spin (6A1) centres.
Eight new copper(II) complexes of 2-benzoylpyridine N(4),N(4)-(butane-1,4-diyl)thiosemicarbazone (HBpypTsc) with general stoichiometry CuBpypTscX [X=N3, Cl, NO3, NCS, ClO4, Br, SH and CN] were synthesized and characterized by IR and UV–Vis spectroscopies. The terdentate nature of the ligand is inferred from the IR spectra. Spin Hamiltonian parameters of the compounds were calculated from the EPR spectra. The structures of the compounds CuBpypTscCl (2), CuBpypTscBr (6) and CuBpypTscSH (7) were solved by single crystal X-ray diffraction. CuBpypTscCl (2) is a centrosymmetric dimer with chloro bridges. The geometry around copper in other two complexes is square planar.
A general description of the graduate courses in object‐oriented (OO) development taught at the University of St. Thomas is presented. The nature of our student body (all professional software developers) accentuates some general problems confronted when teaching OO methods. Our response to these teaching challenges is somewhat unique, including an emphasis on what might be described as philosophical issues and the presentation of a development method that synthesizes aspects of data, model and responsibility driven approaches.
The synthesis and elemental analysis of both 2,6-diacetylpyridine mono-thiosemicarbazone (I) and bis-thiosemicarbazone (II) are reported. Electronic and i.r. spectra of both reagents are described. I and II have two pK values: 1.27 ± 0.06; 11.30 ± 0.08 and 1.51 ± 0.02; 11.48 ± 0.09, respectively. The reactions of both reagents with Ni(II), Cu(II), Co(II) and FE(III) were studied and discussed in order to test the ligating behaviour.
An interesting series of three Ni(II) complexes with the general formula [NiLX]·12H2O (X=Cl, N3 and NCS) were synthesized using di-2-pyridyl ketone N4,N4-(butane-1,4-diyl) thiosemicarbazone (HL). The structures of the compounds NiLCl (1) and NiL(N3) (2) have been solved by single crystal X-ray crystallography with P1̄ and Pbca space groups, respectively. Electronic spectral data suggests a square planar geometry around nickel(II) in all the complexes. X-ray diffraction studies reveal that the thiosemicarbazone is bonded to the nickel(II) centre as an NNS donor ligand coordinating through one of the pyridine nitrogens, azomethine nitrogen and thiolate sulfur. Magnetic susceptibility measurements at room temperature indicate the diamagnetic nature of all the complexes. 1H NMR, UV/Vis and IR spectroscopic data are consistent with the structures of compounds 1 and 2 derived from the crystallographic results and the spectral data for compound NiL(NCS) (3) suggest a structure similar to the chloro and azido derivatives.
Seven new copper(II) complexes of 2-hydroxyacetophenone N(4)-substituted thiosemicarbazones (H2L) and bidentate polypyridyl compounds 2,2′-bipyridine and 1,10-phenanthroline (B) were prepared and characterized. The thiosemicarbazones bind to the metal as dianionic ONS donors (L2−) and yield compounds of the stochiometry [MLB]. The structure of the compound [Cu(L4)(2,2′-bipy)] (6) was investigated by single-crystal X-ray diffraction method. Spin Hamiltonian and bonding parameters of the compounds calculated from the EPR spectra suggest square pyramidal (SPY) structure for the compounds. The g values predict geometry of C4v symmetry with B1g ground state. The bonding parameters show significant in-plane π-bonding. The cyclic voltammetric study of the complexes shows irreversible redox peaks corresponding to Cu(II/I) couple and quasi-reversible redox peaks corresponding to copper(II/III) oxidation. The thiosemicarbazones and their copper complexes show significant growth inhibitory activity against bacteria Escherichia coli, Staphylococcus aureus, and fungi Candida albicans and Aspergillus flavus.
The reaction between gold(III) chloride (AuCl 3) and 2-benzoylpyridine N(4), N(4)-(butane-1,4-diyl) thiosemicarbazone (HBpypTsc) leads to an unexpected formation of a first gold(III) complex from an N(4)-disubstituted thiosemicarbazone derived from 2-benzoylpyridine. The crystal structure, spectroscopic characterization, and preliminary biological activity of [Au(III)(Cl)(BpypTsc)][Au(I)Cl 2] complex are discussed. The reaction between gold(III) chloride(AuCl 3) and 2-benzoylpyridine N(4), N(4)-(butane-1,4-diyl) thiosemicarbazone (HBpypTsc) leads to an unexpected formation of a first gold(III) complex from an N(4)-disubstituted thiosemicarbazone derived from 2-benzoylpyridine. The crystal structure, spectroscopic characterization, and preliminary biological activity of [Au(III)(Cl)(BpypTsc)][Au(I)Cl 2] complex are discussed herein.
Summary Metal complexes of 2-acetylpyridineN-oxide thiosemicarbazone have been prepared and characterized. Coordination occurs as a neutral bidentate (ON) and a deprotonated tridentate (ONS) ligand.
The electronic properties and i.r. spectra of a series of bis(ethylenediamine)copper(II) complexes are reported. From a gaussian analysis of the electronic spectra, measured at room temperature and at the temperature of liquid nitrogen, of the seven complexes of known crystal structure, and three transitions 2A1gâ†�2B1g, 2B2gâ†�2B1g, and 2Egâ†�2B1g in D4h symmetry are tentatively assigned. From the e.s.r. spectra of polycrystalline samples of the complexes, which yield tetragonal spectra, the values of (g‖– 2)/(g⊥– 2) have been determined. Where the ratio is <4·0, exchange coupling is considered to be present; where it is >4·0 the observed g-values are considered to reflect approximately the local copper(II) ion g-values. In the latter case the g-values have been combined with the appropriate electronic transitions and the orbital reduction factors k⊥ and k‖ evaluated. From the i.r. spectra of the polyanions, an infrared criterion is established for recognising the presence of weakly co-ordinated polyanions in the long tetragonal positions above and below the [Cu en2]2+ cation. The term semi-co-ordination is introduced to describe this structural situation.
A novel macrocyclic tetranuclear copper(II)-copper(I) mixed -valence complex was prepared and charaterized by spectroscropic and crystallography structure analysis. Each tetranuclear unit connected to the neighbor one by one using the Cu...S bond with the type of apical Cu(1)...S(3B) bond forming an infinite step chain.
ESR spectra of copper complexes have been interpreted by means of molecular orbital theory, and the ``covalent'' character of both σ and π bonds have been discussed for a variety of compounds. Overlap integrals have been considered in a consistent manner in treating σ bonds. Particular attention has been given to Cu phthalocyanine and several of its derivatives. The in‐plane π bonding may be as important in determining the properties of a Cu complex as is the in‐plane σ bonding.
Metal-halide complexes of pyridine and certain other nitrogen-donor ligands have been extensively investigated in the 200-700 cm.-1 region and assignments of metal-halogen ν(M-X) and metal-ligand ν(M-L) stretching vibrations are made. The relationship of the numbers of ν(M-X) and ν(M-L) vibrations and their frequencies to the stereochemistries of the complexes (MXmLn) is outlined. In particular, it is shown that complexes with tetrahedral and octahedral stereochemistries may be clearly distinguished by their infrared patterns. Nujol mull spectra and solution spectra are essentially the same.
Three tin(IV) complexes of 2-benzoylpyridine N(4)-phenylthiosemicarbazone (H2Bz4Ph) were prepared: [Sn(L)Cl3] (1), [BuSn(L)Cl2] (2) and [(Bu)2Sn(L)Cl] (3), in which L stands for the anionic ligand formed upon complexation with deprotonation and release of HCl. The complexes were characterized by a number of spectroscopic techniques. The crystal structures of H2Bz4Ph and complex 3 were determined. The antifungal activity of the ligand and its tin(IV) complexes was tested against Candida albicans. The thiosemicarbazone proved to be more active than the tin(IV) complexes. Copyright © 2003 John Wiley & Sons, Ltd.
The synthesis, structure and spectroscopic properties on complexes with the formula [Cu(LIII)2] (1) and Cu(NO3) 2(HLIII)2 (2), where HLIII = thiophene-2-carbaldehyde thiosemicarbazone, have been developed. The molecular structure of compound 1 consists of monomeric entities. The copper(II) ions exhibit distorted square-planar geometry with both bidentate thiosemicarbazone ligands placed in a centrosymmetric way. Metal to ligand π-backdonation is proposed to explain several structural and spectroscopic features in these complexes. The EPR spectra of compound 1 show an orthorhombic g tensor indicating the presence of weak magnetic exchange interactions. The reaction of compound 1 with glutathione causes the reduction of the metal ion and the substitution of the thiosemicarbazone ligand by the thiol ligand. This mechanism seems to be related to the cytotoxicity of this complex against Friend Erithroleukemia cells (FLC) and melanome B16F10 cells.
Copper(II) complexes of 2-acetylpyridine 4,4-dimethyl-3-thiosemicarbazone (L′H) and 2-acetylpyridine 4-(4-methylpiperidinyl)-3-thiosemicarbazone (LH) of the general formula CuLX (where L is a deprotonated ligand and X = F−, Cl−, Br−, I−, OAc− and NO−3) have been synthesized and characterized by elemental analysis, magnetic susceptibility measurements between 93 and 298 K in the polycrystalline state, i.r. spectra, electronic spectra, conductivity measurements and ESR spectra recorded in the polycrystalline state, in chloroform and dimethylformamide solution at room temperature and at 77K. The molar conductivities measured in dimethylformamide for all complexes show them to be non-electrolytes. The terdentate character of the ligands in all the complexes is inferred from i.r. spectral studies. The i.r. spectra also confirm the monodentate nature of the polyatomic anions such as nitrate and acetate. The electronic spectra in Nujol mulls, chloroform or dimethylformamide solution suggest planar geometry for all of the complexes. The calculated ESR parameters show an axial dx2−y2 ground state and suggest coordination through sulphur in agreement with the i.r. results. Little change in the value of g with temperature indicates no significant change in planarity of these four coordinated species. ESR spectra in solution at room temperature and 77 K also suggest a strong covalent environment with strong in-plane sigma and pi bonds provided by the ligands.
The synthesis, characterization, molecular and crystal structure of 2-benzoylpyridine N(4)-cyclohexylthiosemicarbazone is reported. IR analysis was done and NMR assignments using COSY homonuclear and HMQC heteronuclear correlation techniques were carried out. The electronic structure of the compound was revealed by solid state reflectance studies and in chloroform solution. The infrared spectrum gives evidence for the compound in the thione form, which is consistent with the observed bond lengths from the crystal structure. The compound crystallizes into a monoclinic lattice with space group P21/n. The non-coplanarity of the two benzene rings in the compound is confirmed from the dihedral angles. Puckering analysis and least square planes calculations point out to chair conformation of the cyclohexyl ring.
Copper(II) complexes of general formula [Cu(L4A)X] (where L4A is the deprotonated ligand, 1 H-hexahydroazepine-1-thiocarboxylic acid-2-[1-(2-pyridinyl)ethylidene]hydrazide and X=Cl, Br, I, NCS, NO3 and OAc) and [Cu(HL4A)(L4A)]ClO4 have been prepared and characterized by elemental analyses, magnetic susceptibility measurements, i.r. spectra, electronic spectra, conductivity measurements and e.s.r. spectra in the polycrystalline state and in chloroform solution. For all complexes, except the perchlorate salt, coordination occurs via imine nitrogen, pyridine nitrogen and thione sulphur. For the perchlorate salt, L4A is tridentate, while HL4A is monodentate via imine nitrogen. Electronic spectra suggest planar geometry for all the complexes. The calculated e.s.r parameters suggest coordination through sulphur in agreement with the i.r. results.
The nature of metal complexes of heterocyclic thiosemicarbazones reported in the literature through 1989 have been reviewed
with an emphasis on variations in stoichiometry and stereochemistry. A brief introduction is followed by a survey of the biological
activity of the uncomplexed thiosemicarbazones. Next is a section on the chemical nature of thiosemicarbazones including a
discussion of preparative methods, modes of coordination and isomerism. This is followed by a discussion of structural information
and biological activity of the iron(III), iron(II), copper(II), cobalt(III), cobalt(II) and nickel(II) complexes of heterocyclic
thiosemicarbazones. Short sections on the biological activity of other chelating thiosemicarbazones and metal complexes are
also included.
The complexes [Cu(NNS)X] (HNNS represents the 2-benzoylpyridine Schiff bases of S-methyl- or S-benzyldithiocarbazate; XCl, Br, NO3) have been prepared and characterized by a variety of physico-chemical techniques. Magnetic and spectral evidence support a square-planar structure for the [Cu(BpSR)X] (BpSR=the benzoylpyridine Schiff bases; RCH3, CH2C6H5; XCl, Br) and [Cu(BpSMe)NO3] complexes and a five-coordinate distorted square-pyramidal structure for the [Cu(BpSBz)NO3] complex. The crystal structures of [Cu(BpSMe)NO3] and [Cu(BpSBz)NO3] have been determined by X-ray diffraction studies. The complex [Cu(BpSMe)NO3] crystallizes in the triclinic space group P1 with , . The complex has a distorted square-planar geometry with the copper ion lying in an approximate plane of four coordinating atoms, three of which come from the 2-benzoylpyridine Scniff base of S-methyldithiocarbazate while the fourth coordination site is occupied by an oxygen from the nitrate ligand. The complex, [Co(BpSBz)NO3] crystallizes in the monoclinic space group P21/a with . The coordination environment around the copper(II) ion is a distorted square-pyramid with three donor atoms (NNS) coming from the 2-benzoylpyridine Schiff base and the fourth and fifth atoms (oxygen) coming from the bidentade NO3− ion. The antifugal and antibacterial properties of the Schiff bases and their copper(II) complexes have been evaluated against three pathogenic fungi and two bacteria. The Schiff bases and copper(II) complexes display moderate antifungal activities but their activities are less than that of the commercially important antifungal agent nystatin.
An interesting series of eight neutral ternary Co(III) complexes of 2-hydroxyacetophenone N(4)-substituted thiosemicarbazones (H2L), bidentate heterocyclic bases (L1) 2,2'-bipyridine (bpy)/1,10-phenanthroline (phen) and azide, [MLL1(N3)], were prepd. The complexes were characterized by spectroscopic methods. The coordination geometry around Co(III) in all the complexes is distorted octahedral with one dibasic tridentate ligand L2-, one bidentate heterocyclic base and one terminally coordinated azide group. Crystal structure of the compd. CoL4(bpy)N3 (H2L4 = 2-HOC6H4CMe:NNH(CS)NMePh) was completely solved. All the electronic transitions were assigned. All complexes were diamagnetic indicating Co in a d6 strong field. [on SciFinder(R)]
Based on the antimalarial properties observed for 2-acetylpyridine 4-phenyl-3-thiosemicarbazone (1), an extensive series of related thiosemicarbazones was prepared and tested against Plasmodium berghei in mice. Screening results indicated that the presence of the 2-pyridylethylidene group was critical and that certain phenyl, benzyl, phenethyl, or cycloalkyl groups at N4 of the thiosemicarbazone moiety also contribute to antimalarial activity.
The more significant bioactivities of a variety of semicarbazones (anti-protozoa, anticonvulsant) and thiosemicarbazones (antibacterial, antifungal, antitumoral, antiviral) and their metal complexes are reviewed together with proposed mechanisms of action and structure-activity relationships. Clinical or potential pharmacological applications of these versatile compounds are discussed.
The overall structure including molecular conformation of di-2-pyridyl ketone 4-methyl-4-phenyl-thiosemicarbazone was investigated. An intramolecular hydrogen bond containing the pyridyl N atom and the H atom attached to the hydrazine N atom leads to the formation of a six-membered ring. Molecular conformations were observed when a piperidyl or hexamethyleneiminyl ring occupies the N 4-position. The results show that the intramolecular N4-H4...N2 hydrogen bond leads to the formation of a six-membered ring comprising atoms N2, C7, C6, N3, N4 and H4.
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