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Synthesis, characterization, DFT calculations, and antimicrobial activity of Pd(II) and Co(III) complexes with the condensation derivative of 2-(diphenylphosphino)benzaldehyde and Girard’s T reagent
Abstract
Complexes of Pd(II) and Co(III) with the condensation derivative of 2-(diphenylphosphino)benzaldehyde and Girard T reagent were synthesized, characterized, and their antimicrobial activities were evaluated. The ligand and the complexes were characterized by elemental analysis, IR and NMR spectroscopies, and X-ray crystallography. In both complexes, the deprotonated ligand was coordinated to the metal through the phosphorus, the imine nitrogen, and the carbonyl oxygen atoms. In the octahedral Co(III) complex, two molecules of ligands were coordinated to metal ion, while square-planar environment of Pd(II) complex was constituted of one tridentate ligand and chloride in the fourth coordination place. The ligand and complexes showed moderate antibacterial activity. The molecular structures of the obtained metal complexes and the relative stabilities of two stereoisomers of the ligand were calculated using density functional theory at the S12g/TZ2P level.
... Hydrazones of 2-(diphenylphosphino)benzaldehyde represent an interesting group of phosphine ligands which possess a combination of soft and hard electron donor atoms and exhibit versatile coordination modes depending on reaction conditions and the nature of central metal ion [1][2][3][4][5][6][7][8][9][10][11][12][13]. Of particular importance is the observed biological activity (antimicrobial and antitumor) of these ligands and their complexes [13][14][15][16][17][18][19][20][21]. Recently, we synthesized two series of square-planar Ni(II) complexes with tridentate PNO acylhydrazones of 2-(diphenylphosphino)benzaldehyde and studied their antimicrobial and antitumor activity [20,21]. ...
Square-planar azido Ni(II) complex with condensation product of 2-(diphenylphosphino)benzaldehyde and Girard's T reagent was synthesized and its crystal structure was determined. Cytotoxic activity of the azido complex and previously synthesized isothiocyanato, cyanato and chlorido Ni(II) complexes with this ligand was examined on six tumor cell lines (HeLa, A549, K562, MDA-MB-453, MDA-MB-361 and LS-174) and two normal cell line (MRC-5 and BEAS-2B). All the investigated nickel(II) complexes were cytotoxic against all tumor cell lines. The newly synthesized azido complex showed selectivity to HeLa and A549 tumor cell lines compared to the normal cells (for A549 IC50 was similar to that of cisplatin). Azido complex interferes with cell cycle phase distribution of A549 and HeLa cells and possesses nuclease activity towards supercoiled DNA. The observed selectivity of the azido complex for some tumor cell lines can be connected with its strong DNA damaging activity.
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Abstract
This article details the synthesis of new Girard-T reagent ligands. Condensation of 2-hydroxyacetophenone or 2-acetyl-thiophene with Girard-T reagent results in new hydrazone ligands. The interaction of these Girard-T hydrazones with transition metal chlorides, like Au (III), Ru (III), Pd (II), and Pt (II), produces different complexes. Elements and spectrum analyses (IR, UV–Vis, EI-mass, and 1H NMR) were used to characterize the isolated solid complexes, as well as conductimetric and magneto-chemical studies. Metal complexes can have different geometrical configurations, including square planar and octahedral coordination. The DMOL3 method, which is a part of the Material Studio package, was also utilized for structure optimization. Horowitz–Metzger and Coats–Redfern methods were utilized to calculate the various thermodynamic and kinetic parameters. The ligands and the complexes of their metal were evaluated for anticancer activity against carcinoma cervix (Prostate) and the mammary gland female breast (MCF-7) cell line having cancer, with promising results. Among these compounds, the Ru (III) and Pt (II) complexes' anticancer activity against (MCF-7) cell lines, comparable with that of 5-fluorouracil were carried out and their interactions were performed by molecular docking simulations against MCF-7 (PDB ID: 3W2S) receptor.
The reaction of ethyl isothiocyanate with Girard's T affords a new hydrazone named 2‐(2‐N,N,N‐trimethyl‐2‐oxoethane‐1‐auminium chloride [EtGT]). Its structure was confirmed by single crystal X‐ray diffraction. Also, the isolations and characterizations of new metal complexes with EtGT were confirmed by elemental analyses, IR, UV‐visible, magnetic measurements, ¹³C‐NMR, ¹H‐NMR, and thermal analyses. IR spectra suggest that the ligand acts as a bidentate coordinating either via the carbonyl oxygen and the nitrogen atom of the hydrazine group or through the sulfur (C=S and/or C‐S) and the NH groups. The computational estimation of EtGT and its complexes were approved with the Gaussian 09 W program in DFT/B3LYP. DPPH and ABTS are two free radical scavenger tests that were utilized in order to evaluate the antioxidant potential of complexes in vitro. Furthermore, the biological effectiveness of the ligand and its complexes against bacteria varieties Gram (+ve) and Gram (−ve) bacteria was in vitro investigated. Also, antifungal action was investigated utilizing inhibition zone diameter. Moreover, the ligand and its complexes also exhibited a broad spectrum of DNA degradation effects, as measured by agarose gel electrophoresis. Cyclic voltammetry of Co²⁺ with different concentrations was measured experimentally. Molecular docking is exercised to examine the inhibitor characteristics of complexes through binding propensity with CTX‐M‐14 β‐lactamase (Class A).
Phosphino hydrazones represent a versatile class of nitrogen‐containing phosphine ligands. Herein, we report a modular synthesis of phosphino hydrazone ligands by hydrazone condensation reaction of three different aryl hydrazines with 3‐(diphenylphosphino)propanal (PCHO). Complexation reactions of these phosphino hydrazone ligands with palladium(II) and platinum(II) were investigated and the catalytic activity of the palladium(II) complexes was explored in a Cu‐free Sonogashira cross‐coupling reaction achieving yields up to 96 %. Additionally it was shown that the catalytically active species is homogeneous.
Herein we studied the synthesis and the biological properties of palladium (II) complexes derived from iminophosphine ligands DPPB-3-hydroxybenzohydrazone (DPPB-HBH), DPPB-4-phenylthiosemicarbazone (DPPB-PTSC), and DPPB-thiosemicarbazone (DPPB-TSC)
(DPPB = 2-(diphenylphosphino)benzaldehyde) using theoretical and experimental methods. The molecular structures of [PdCl(DPPB-HBH)]Cl, [Pd(DPPB-HBH)2]2Cl∙2CH3CN, [PdCl(DPPB-PTSC)], and [PdCl(DPPB-TSC)] were characterized by various spectroscopic techniques and X-ray crystallographic for [PdCl(DPPB-HBH)]Cl, [Pd(DPPB-HBH)2]2Cl∙2CH3CN, and [PdCl(DPPB-PTSC)], confirming the distorted square-planar geometry for the palladium atoms. Complexes with the general formula [PdCl(Ligand)x] (x = 1) were employed to evaluate biological activities such as cytotoxicity against the MDA-MB-231 breast cancer cells and DNA binding ability. The results revealed the high cytotoxicity of the palladium complexes compared to the reference drug cisplatin (IC50= 24.59 µg/mL), as well as their moderate binding ability to DNA through electrostatic interactions and groove binding. It was also found that [PdCl(DPPB-HBH)]Cl has the highest activity among others (IC50 = 9.3 µg/mL). Their interaction mode with DNA was investigated using molecular docking and NCI calculations, which showed complete agreement with the experimental results. Furthermore, quantum chemistry calculations were used to analyze the structure-activity relationship and introduce reactive sites, which determined the cause of the difference in the reactivity of the samples.
In this work we present the synthesis, and experimental and theoretical analysis of a binuclear nickel(II) complex coordinated to a new phthalazine dihydrazone-based ligand. Single-crystal X-ray diffraction analysis of the metal complex shows that the coordination geometry around each nickel(II) atom is distorted octahedral. DFT calculations predict that the magnetic exchange coupling constant of the binuclear nickel(II) complex is predominantly anti-ferromagnetic.
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The pseudohalide metal complexes with hydrazones of Girard's T reagent are reviewed with respect to their synthesis, characterization, structures (in both solution and solid state) and magnetic properties. This microreview can serve as a concise guide through chemistry of pseudohalide metal complexes with hydrazones of Girard's T reagent.
Pentagonal-bipyramidal isothiocyanato Co(II) and Ni(II) complexes with condensation product of 2,6-diacetylpyridine and trimethylammoniumacetohydrazide (Girard’s T reagent) were synthesized and characterized by elemental analyses, IR and UV-Vis spectra, molar conductivity and magnetic susceptibility. Crystal structures of the Co(II) and Ni(II) complexes were also determined. Antimicrobial activities of the ligand and metal complexes were examined.
Square-planar isocyanate and chloride Ni(II) complexes with tridentate PNO condensation product of 2-(diphenylphosphino)benzaldehyde and Girard’s T reagent have been synthesized and their crystal structures determined. These Ni(II) complexes with different monodentate ligands, chloride, cyanate and thiocyanate, were tested for their antimicrobial activities against pathogenic microorganisms. The ligand and Ni(II) complexes were active not only against laboratory control strains of bacteria and yeast, but also on clinical isolates of E. coli and P. aeruginosa strains resistant to most of the clinically used antibiotics.
Octahedral and square-planar isothiocyanato complexes of Ni(II) with the condensation derivative of 2-(diphenylphosphino)benzaldehyde and Girard‟s T reagent were synthesized and characterized by elemental analysis, IR spectroscopy and X-ray crystallography. Results of magnetic measurements for octahedral Ni(II) complex were also reported. In all the complexes the ligand is coordinated as tridentate via the phosphorus, the imine nitrogen and the carbonyl oxygen atoms while the remaining coordination positions are occupied with thiocyanato anions. Coordination of deprotonated phosphine ligand results in formation of square-planar complexes, while the octahedral complex was formed with protonated ligand. Reaction energetics with both forms of ligand were studied by the means of DFT and results were in complete agreement with experimental observations. Furthermore, ligand field splitting analysis gave the deeper insight in the relationship of the isolated complex coordination environment and protonation of the ligand.
Syntheses, structures and antimicrobial activities of cobalt(III) complexes with two tetradentate Schiff base ligands, (BA)2en = bis(benzoylacetone)ethylenediimine dianion and (acac)2en = bis(acetylacetone)ethylenediimine dianion, and two axial pyridines (py) have been investigated. These complexes were characterized by FT-IR, H–NMR, UV–Vis spectroscopy and elemental analysis. The crystal structures of the complexes were determined by X-ray crystallography. Single crystal X-ray diffraction analyses revealed that both complexes have distorted octahedral environments, Schiff base ligand coordinates cobalt in four equatorial positions and the two axial positions are occupied by pyridines. The pyridines and Schiff base ligands are involved in N−H···O hydrogen bonds with perchlorate. Biological activities of the ligands and metal complexes have been studied on Staphylococcus aureus, Escherichia coli, and Bacillus subtilis by the well diffusion method. The activity data show the metal complexes to be more potent than the parent ligand against two bacterial species.
New hydrazones of 2-(5-thioxo-4,5-dihydro-1,3,4-thiadiazol-2-ylthio)acetohydrazide have been obtained and the percentages
of anti/syn - conformers were determined. Based on the analyses of 1H NMR spectra, it was concluded that for hydrazones obtained from the 2- hydroxybenzaldehydes and 2’-hydroxycetophenones the
ratio between the anti-and syn-conformers depends on the strength of intramolecular hydrogen bond (IMHB) between the nitrogen atom of the imino group and
the proton of the 2-hydroxy group. It was shown that increase in IMHB strength results in stabilization of the anti-conformer in solution.
Analytical expressions are derived for the evaluation of energy gradients in the zeroth order regular approximation (ZORA) to the Dirac equation. The electrostatic shift approximation is used to avoid gauge dependence problems. Comparison is made to the quasirelativistic Pauli method, the limitations of which are highlighted. The structures and first metal-carbonyl bond dissociation energies for the transition metal complexes W(CO)6, Os(CO)5, and Pt(CO)4 are calculated, and basis set effects are investigated. © 1999 American Institute of Physics.
Two new potentially hexadentate Schiff bases, [H2L1] and [H2L2], were prepared by condensation of 2-(3-(2-aminophenoxy) naphthalen-2-yloxy) benzenamine with 3,5-di-tertbutyl- 2-hydroxy benzaldehyde and o-vanillin, respectively. Reaction of these ligands with cobalt(II) chloride, copper(II) perchlorate, and zinc(II) nitrate gave complexes ML. The ligands and their complexes have been characterized by a variety of physico-chemical techniques. The solid and solution state investigations show that the complexes are neutral. Molecular structures of [CuL1], [CoL1] center dot C7H8, and [ZnL2] center dot CH3CN, which have been determined by single-crystal X-ray diffraction, indicate that [CuL1] and [ZnL2] center dot CH3CN display distorted square planar and distorted trigonal-bipyramidal geometry, respectively; the geometry around cobalt in [CoL1] center dot C7H8 is almost exactly between trigonal bipyramidal and square pyramidal. The synthesized ligands and their complexes were screened for their antibacterial activities against eight bacterial strains and the ligands and complexes have antibacterial effects. The most effective ones are [CuL2] against Proteus vulgaris, Serratia marcescens, Staphylococcus subtilis, [(HL1)-L-2] against S. subtilis, and [H2L2] against S. subtilis.
New software,
OLEX2
, has been developed for the determination, visualization and analysis of molecular crystal structures. The software has a portable mouse-driven workflow-oriented and fully comprehensive graphical user interface for structure solution, refinement and report generation, as well as novel tools for structure analysis.
OLEX2
seamlessly links all aspects of the structure solution, refinement and publication process and presents them in a single workflow-driven package, with the ultimate goal of producing an application which will be useful to both chemists and crystallographers.
The method of dispersion correction as an add-on to standard Kohn-Sham density functional theory (DFT-D) has been refined regarding higher accuracy, broader range of applicability, and less empiricism. The main new ingredients are atom-pairwise specific dispersion coefficients and cutoff radii that are both computed from first principles. The coefficients for new eighth-order dispersion terms are computed using established recursion relations. System (geometry) dependent information is used for the first time in a DFT-D type approach by employing the new concept of fractional coordination numbers (CN). They are used to interpolate between dispersion coefficients of atoms in different chemical environments. The method only requires adjustment of two global parameters for each density functional, is asymptotically exact for a gas of weakly interacting neutral atoms, and easily allows the computation of atomic forces. Three-body nonadditivity terms are considered. The method has been assessed on standard benchmark sets for inter- and intramolecular noncovalent interactions with a particular emphasis on a consistent description of light and heavy element systems. The mean absolute deviations for the S22 benchmark set of noncovalent interactions for 11 standard density functionals decrease by 15%-40% compared to the previous (already accurate) DFT-D version. Spectacular improvements are found for a tripeptide-folding model and all tested metallic systems. The rectification of the long-range behavior and the use of more accurate C(6) coefficients also lead to a much better description of large (infinite) systems as shown for graphene sheets and the adsorption of benzene on an Ag(111) surface. For graphene it is found that the inclusion of three-body terms substantially (by about 10%) weakens the interlayer binding. We propose the revised DFT-D method as a general tool for the computation of the dispersion energy in molecules and solids of any kind with DFT and related (low-cost) electronic structure methods for large systems.
Two new programs have been developed for searching the Cambridge Structural Database (CSD) and visualizing database entries:
ConQuest
and
Mercury
. The former is a new search interface to the CSD, the latter is a high-performance crystal-structure visualizer with extensive facilities for exploring networks of intermolecular contacts. Particular emphasis has been placed on making the programs as intuitive as possible. Both
ConQuest
and
Mercury
run under Windows and various types of Unix, including Linux.
Two new transition metal complexes of Schiff bases, [Pd2(L1)2Cl2] (1) and [Zn(L2)2] (2), [L1 = N-(4-fluorobenzylidene)-2,6-diisopropylbenzenamine and L2 = 2,4-dibromo-6-((E)(mesitylimino)methyl)phenol], have been synthesized solvothermally and characterized by elemental analysis, IR-spectroscopy, thermogravimetric analysis, powder X-ray diffraction, UV-vis absorption spectra, and single-crystal X-ray diffraction. Complex 1 is a μ-chloro-bridged dinuclear cyclometallated Pd(II) complex, whereas 2 is mononuclear with the ZnII tetrahedrally coordinated by two L2. Both 1 and 2 display photoluminescence in the solid state at 298 K (fluorescence lifetimes τ = 22.516 ns at 468 nm for 1, τ = 3.697 μs at 490 nm for 2). These Schiff bases and their metal compounds have been screened for antibacterial activity against several bacteria, and the results are compared with the activity of penicillin.
The structural, spectroscopic, and electrochemical properties of [Co{(naph)2dien}(N3)] and [Co{(naph)2dpt}(N3)], where (naph)2dien = bis-(2-hydroxy-1-naphthaldimine)-N-diethylenetriaminedianion and (naph)2dpt = bis-(2-hydroxy-1-naphthaldimine)-N-dipropylenetriaminedianion have been investigated. These complexes are characterized by elemental analyses, IR, and UV–Vis spectroscopy. The crystal structures of these complexes have been determined by X-ray diffraction. The geometry around cobalt is distorted octahedral. The electrochemical behavior of these complexes in acetonitrile solution was also investigated. Both complexes show an irreversible CoIII–CoII reduction at ca. −0.8 V, accompanied by dissociation of the axial CoII–N3 bond. The in vitro antibacterial activities of these complexes were tested against Staphylococcus aureus and Bacillus licheniformis.
A new family of (range-separated) hybrid functionals is presented that
corrects several of the shortcomings of the recently reported SSB-D
functional. The new functionals include Grimme's D3
dispersion energy, contain a reduced number of parameters which have
been optimized against a number of different interaction types. When
comparing the new functionals with over thirty other density
functionals, the new hybrid functional S12h and its range-separated
analogue CAM-S12h are found to be the best performing ones for the
different interaction types. The performance for spin states is poor for
the hybrid functionals, but very well for the GGA counterpart S12g.
A series of square planar mononuclear palladium(II) complexes, [Pd(L-n)(OMe)(2)] (where L-n = 4-(4-chlorophenyl)-6-phenyl-2,2'-bipyridine, 4,6-bis(4-chlorophenyl)-2,2'-bipyridine, 4-(4-bromophenyl) -6-(4-chlorophenyl)-2,2'-bipyridine, and 6-(4-chlorophenyl)-4-p-tolyl-2,2'-bipyridine), have been synthesized and characterized. Interaction of palladium complexes with DNA has been investigated by electronic absorption spectra, viscosity measurements and DNA melting temperature techniques. The metal complex-DNA interaction produced hypochromism and bathochromism, suggesting intercalative binding. Viscosity data support the intercalation mode of binding. Palladium(II) complexes promote cleavage of plasmid pUC19 DNA from the supercoiled form to the open circular form. Antibacterial activities of the complexes have also been evaluated against five pathogenic bacteria. The antimicrobial test results reveal that all compounds have good antibacterial activity against both Gram(-ve) and Gram(+ve) bacterial species compared to the ligands and metal salt.
Photoreactivities of Ni(II)- and Pt(II)-hydrazone complexes, [NiCl(L)] (Ni1) and [PtCl(L)] (Pt1), respectively [HL = 2-(diphenylphosphino)benzaldehyde-2-pyridylhydrazone], were investigated in detail via UV-vis absorption, (1)H nuclear magnetic resonance (NMR) spectroscopy, and electrospray ionization time-of-flight (ESI-TOF) mass spectrometry; the two photoproducts obtained from the photoreaction of Pt1 were also successfully identified via X-ray analysis. The absorption bands of the Ni1 and Pt1 complexes were very similar, centered around 530 nm, and were assigned as an intraligand charge transfer transition of the hydrazone moiety. The absorption spectrum of Pt1 in a CH3CN solution changed drastically upon photoirradiation (λ = 530 nm), whereas no change was observed for Ni1. (1)H NMR and ESI-TOF mass spectra under various conditions suggested that the photoexcited Pt1* reacts with dissolved dioxygen to form a reactive intermediate, and the ensuing dark reactions afforded two different products without any decomposition. In contrast to the simple photo-oxidation of HL to form a phosphine oxide HL(P═O), the X-ray crystallographic analyses of the photoproducts clearly indicate the formation of a mononuclear Pt complex with the oxygenated hydrazone ligand (Pt1O) and a dinuclear Pt complex with the oxygenated and dimerized hydrazone ligand (Pt2). The photosensitized reaction in the presence of an (1)O2-generating photosensitizer, methylene blue (MB), also produced Pt1O and Pt2, indicating that the reaction between (1)O2 and ground-state Pt1 is the important step. In a highly viscous dimethyl sulfoxide solution, Pt1 was slowly, but quantitatively, converted to the mononuclear form, Pt1O, without the formation of the dinuclear product, Pt2, upon photoirradiation (and in the reaction photosensitized by MB), suggesting that this photoreaction of Pt1 involves at least one diffusion-controlled reaction. On the other hand, the same complexes Pt1O and Pt2 were also produced in the degassed solution, probably because of the reaction of the photoexcited Pt1* with the biradical character and H2O.
The reaction of an ethanolic solution of the newly synthesized 2-(diphenylphosphino)benzaldehyde 1-adamantoylhydrazone (HL) with aqueous solutions of K2[MCl4] (M = Pd(II), Pt(II)) resulted in neutral complexes of the general formulae [M(L)Cl]. These complexes have a square-planar structure that was achieved by tridentate PNO coordination of the monoprotonated Schiff base and a chloride ligand. The ligand and its metal complexes were analyzed for their antimicrobial activity and their in vitro cytotoxicity in human larynx carcinoma cells (Hep-2) and non-cancerous human lung fibroblast cells (MRC-5). The platinum(II) complex shows cytotoxicity towards Hep-2 cells comparable to oxaliplatin and exhibited improved selectivity for cancer cells. The ligand and its complexes were characterized by elemental analysis, NMR and IR spectroscopy, and single crystal X-ray diffraction analysis.
Four new acetylhydrazone derivatives of quinazoline have been synthesized and characterized. The molecular structures and relative stabilities of four possible isomers for each acetylhydrazone are calculated using DFT/B3LYP/6-31G(d,p) method. The calculations results predicted higher stability of the E-isomers compared to the Z-isomers in the gas phase. The syn-E isomer is the predominant form in gaseous phase for all the studied hydrazones except for the hydrazone derived from salicylaldehyde where the anti-E is the most stable isomer. The latter is stabilized by two strong intramolecular H-bonds instead of one in the others. The electronic and spectroscopic properties of the most stable isomers were also calculated using the same level of theory. The calculated atomic polar tensor (APT) charges indicated an increase of the positive charge density at the H-sites involved in the H-bonding interactions. The HOMO and LUMO energies are negative indicating that the compounds under investigation are stable. The electronic transition from the ground state to the excited state belongs to π–π* transition. The calculated vibrational spectra showed strong red shifts and increase in the vibrational intensity of the Nsingle bondH and Osingle bondH stretching modes due to the intramolecular H-bonding interactions. In DMSO solution, the NMR spectra of the studied hydrazones revealed that such polar solvents stabilize the syn isomers for all the studied hydrazones except for the hydrazone derived from salicylaldehyde where the anti isomer is the major.
Eight new palladium(II) complexes with 4-toluenesulfonyl-L-amino acid dianion and 1,4-dab/1,3-dap, [Pd(1,4-dab)(TsglyNO)] · H2O (1), [Pd(1,4-dab)(TsvalNO)] (2), [Pd(1,4-dab)(TsleuNO)] (3), [Pd(1,4-dab)(TsileNO)] (4), [Pd(1,4-dab)(TsserNO)] · 0.5H2O (5), [Pd(1,4-dab)(TspheNO)] · 0.5H2O (6), [Pd(1,4-dab)(TsthrNO)] · H2O (7), and [Pd(1,3-dap)(TsserNO)] (8), have been synthesized and characterized by elemental analysis, IR, UV, H NMR, and mass spectrometry. Crystal structure of 8 has been determined by X-ray diffraction. The cytotoxicities were tested by MTT assay. The results indicate the complexes exert cytotoxic effects against HL-60 and Bel-7402. The structure–activity relationship suggests that both amino acids and N-containing ligands have important effects on cytotoxicity, but the IC50 values do not show definite correlation with variation of these ligands.
Five new palladium(II) complexes with 4-toluenesulfonyl-L-amino acid dianion and en, [Pd(en)(TsserNO)] (1), [Pd(en)(TsglyNO)] (2), [Pd(en)(TsalaNO)] · 1.5H2O (3), [Pd(en)(TsleuNO)] · H2O (4), and [Pd(en)(TspheNO)] · 2H2O (5), have been synthesized and characterized by elemental analysis, IR, UV, H NMR, and mass spectrometry. Crystal structure of 1 has been determined by X-ray diffraction analysis. The cytotoxicity was tested by MTT and SRB assays. The results indicate 1–5 exert cytotoxic effects against HL-60, Bel-7402, BGC-823, and KB cell lines and 5 displays the best cytotoxicity. The structure–activity relationships suggest that both amino acid and N-containing ligands have important effects on cytotoxicity.
A new palladium(II) complex with the amino acid L-tryptophan (Pd-TRP) was synthesized in aqueous solution and characterized by chemical and spectroscopic methods. Elemental, ESI-QTOF mass spectrometric, and thermal analyses of the solid compound permitted proposing the [Pd(C11H11N2O2)2] · 2H2O composition. Infrared, Raman, and UV-Vis spectroscopic data indicate the coordination of the ligand to Pd(II) through monodentate oxygen of carboxylate and through nitrogen of the amino group. The H and C NMR spectroscopic data confirm coordination through the carboxylate, while N NMR data confirm coordination of nitrogen of NH2. Density functional theory studies confirmed nitrogen and oxygen coordination to palladium(II) as a minimum of the potential energy surface with calculations of the hessians showing no imaginary frequencies. Biological studies were performed to provide information concerning the antibacterial activities of the compound. The Pd-TRP complex was shown to be active against Gram-positive and Gram-negative pathogenic bacterial strains.
The tridentate hydrazonic ligand 2-(diphenylphosphino)benzaldehyde benzoylhydrazone (HPNO) reacts with Rh2(CO)4Cl2 in toluene or THF leading to the formation of the chloro Rh(III) complex [RhCl3(HPNO)] (5) and of the carbonyl Rh(I) complex [Rh(PNO)(CO)] (3); the reaction occurs with evolution of CO and H2. The same products are obtained on refluxing a THF or a toluene solution of the chloro-carbonyl Rh(I) complex [RhCl(HPN)(CO)] (2). Furthermore, complex 5 also forms on bubbling gaseous HCl into a solution of 3, but in this case its formation is preceded by the precipitation of another species that is tentatively identified as the hydride-carbonyl Rh(III) complex [RhCl2H(HPN)(CO)]
(4). Pure 5 is synthesized by reacting equimolar amounts of HPNO and hydrated RhCl3 in THF at room temperature. Once dissolved in dmso, complex 5 transforms into complex [RhCl2(PNO)(dmso)]·dmso (6) by elimination of a HCl molecule; complex 6 has been structurally characterized. On bubbling an excess of HCl into a solution of the acetyl Rh(III) complex [RhI(MeCO)(PNO)] (7), complex 5 and acetaldehyde are produced. Conversely, on using a stoichiometric amount of HCl, the reaction brings to the acetyl complex [RhCl1.6I0.4(MeCO)(HPNO)]·CH2Cl2 (8), which has been characterized
by X-ray crystallography.
Several potentially tridentate hydrazonic ligands containing a PNO donor atom set were synthesised and used to prepare the corresponding acetato palladium(II) complexes. These were used as catalysts in the homogeneous hydrogenation of styrene and other unsaturated C–C bonds under mild conditions. Depending on the basicity of the hydrazonic nitrogen of the ligand, a different catalytic activity of the complexes was observed. This substantiates a heterolytic activation of the molecular hydrogen, which leads to the protonation of the ligand and formation of a palladium(II) hydride complex. Kinetic studies of the hydrogenation of styrene in methanol were performed, using complex 1a as catalyst. A dependence, approximately of first order in hydrogen and catalyst concentrations and zero order in styrene concentration, was found. Two kinetic equations derived from a statistic processing are compared. The X-ray crystal structure of complex 1a is also reported.
The hydrazone ligand 2-(diphenylphosphanyl)benzaldehyde benzoylhydrazone (HPNO) forms the methyl PdII complex [Pd(HPN)(Me)Cl] (1) in high yield when treated with [(COD)Pd(Me)Cl] in dichloromethane or diethyl ether at room temperature. In complex 1, the ligand remains neutral and is P,N bidentate. The deprotonation of the ligand by Et3N affords [Pd(PNO)(Me)] (2), in which the anionic ligand is P,N,O tridentate. When 1 is treated with AgCF3SO3, the cationic complex [Pd(HPNO)(Me)]+[CF3SO3]− (3) is formed; here the neutral ligand coordinates in a tridentate P,N,O fashion. All three methyl complexes were subjected to 30 atm of CO pressure, resulting in the isolation of the corresponding acetyl complexes [Pd(HPN)(MeCO)Cl] (4), [Pd(PNO)(MeCO)] (5) and [Pd(HPNO)(MeCO)]+[CF3SO3]− (6). Complex 4 is completely stable in solution in the absence of CO, whereas 5 and 6 quickly decarbonylate to regenerate the starting methyl complexes 2 and 3. Complexes 5 and 6 can also be obtained in high yields by treatment of 4 with Et3N and AgCF3SO3, respectively. The X-ray crystal structures of the complexes 2, 5 and 6 were determined.
A cobalt(III) complex with the condensation derivative of 2-(diphenylphosphino)benzaldehyde and ethyl
carbazate was synthesized. X-ray crystal structure was determined for both the ligand and the complex.
In the cobalt(III) complex two deprotonated ligand molecules coordinate the metal atom in a distorted
octahedral geometry by chelation through the PNO donor system formed by the phosphorus, the imine
nitrogen and the carbonyl oxygen. The complex showed a moderate antibacterial activity and a strong
cytotoxic activity, stronger than cisplatin. Based on cell cycle progression, apoptotic assays, spectroscopic
and electrophoretic studies, it was shown that high cytotoxicity and moderate potential of induction of
apoptosis are not consequence of interactions with DNA.
Starting from the screening in conductors, an algorithm for the accurate calculation of dielectric screening effects in solvents is presented, which leads to rather simple explicit expressions for the screening energy and its analytic gradient with respect to the solute coordinates. Thus geometry optimization of a solute within a realistic dielectric continuum model becomes practicable for the first time. The algorithm is suited for molecular mechanics as well as for any molecular orbital algorithm. The implementation into MOPAC and some example applications are reported.
The synthesis and crystal structure analysis of the diamagnetic complex [Ni(L)Py]NO3 (L = the monoanion of the newly synthesized ligand 2-(diphenylphosphino)benzaldehyde thiosemicarbazone) are reported. The complex crystallizes in the space group P21/n (No. 14) with a = 8.533(1), b = 29.123(3), c = 10.627(a) Å, β = 100.36(1)°, V = 2597.8(5) Å. As revealed by X-ray analysis, the 2-(diphenylphosphino)benzaldehyde thiosemicarbazone ligand deprotonated at N(3) acts as a monoanionic tridentate donor, coordinating through SNP. The core of the bulky {Ni[(C6H5)2P-(C6H4CH=N-N=CS-NH2)·]} cation is a slightly puckered quadrangle formed around Ni by SNP accompanied by a pyridine nitrogen. The dihedral angle of the atomic triangles S/N(4)/N(41) and P(2)/N(4)/N(41) is 18.0(4)°. The NO3 anions are well separated from the cations which may account for the observed disorder of the oxygen atoms.
The bimetallic [Ni2(H2L2)2](ClO4)4 (1), [Ni2(HL2)(H2L2)](ClO4)3 (2) and [Zn2(H2L2)2](BF4)4 (3) complexes (H2L2=N′,N′2-bis[(1E)-1-(2-pyridyl)ethylidene]propanedihydrazide) were synthesized and characterized. The structure of complexes (1) and (2) was established by X-ray analysis. NMR spectroscopy was used for the characterization of complex (3). The complexes (1) and (2) were obtained from the same synthetic reaction and two crystal types of these complexes have been isolated during the fractional crystallization process.In complex (1) each Ni(II) ion is coordinated with two NNO donor atom sets from two H2L2 ligands forming an octahedral geometry. Similarly, in complex (2) the octahedral geometry of each Ni(II) ion is attained by coordination of two NNO donor atom sets, one from the neutral and the other from the monoanionic form of the ligand. The antimicrobial activity of the ligand and complexes is also presented.
Palladium(II) complexes of the type Pd(PNO)Y (PNO = 2-(diphenylphosphino)benzaldehyde picolinhydrazone, nicotinhydrazone, isonicotinhydrazone; Y = CH3CO2, Cl, I) and Pd(PNS)Y (PNS = 2-(diphenylphosphino)benzaldehyde thiosemicarbazone; Y = CH3CO2, Cl, I) were synthesised and characterised by spectroscopic methods. The X-ray structure of an iodo complex was also determined. The catalytic activity of all the complexes in the homogeneous hydrogenation of terminal double and triple bonds was tested with particular regards to the chemoselectivity from triple to double bond. A correlation between the catalytic activity and the nature of the ligand and Y group was established. In the hydrogenation of phenylacetylene using acetato complexes as catalysts, stable phenylethynylpalladium(II) complexes were recovered and characterised by spectroscopic methods. A facile route of synthesis of alkynyl complexes was also determined.
The well-known rhodamine spiro-lactam framework offers an ideal model for the development of fluorescence-enhanced chemosensors through simple and convenient syntheses. Herein, we report a new tridentate PNO receptor, which was introduced into a rhodamine spiro-lactam system to develop Pd(2+) -chemosensor RPd4, that displayed significantly improved sensing properties for palladium. Compound RPd4 shows a very fast response time (about 5 s), high sensitivity (5 nM), and excellent specificity for Pd(2+) ions over other PGE ions (Pt(2+) , Rh(3+) , and Ru(3+) ). In addition, RPd4 displays quite different responses to different valence states of the Pd ions, that is, very fast response towards Pd(2+) ions but slow response towards Pd(0) , which may provide us with a convenient method for the selective discrimination of Pd species in different valence states. According to proof-of-concept experiments, RPd4 has potential applications in Pd(2+) -analysis in drug compounds, water, soil, and leaf samples. Owing to its good reversibility, RPd4 can also be used as a sensor material for the selective detection and visual recovery of trace Pd(2+) ions in environmental samples.
(NBu4)[ReOCl4] reacts with 2-(diphenylphosphino)benzaldehyde 4-phenylsemicarbazone (HL1) in methanol under formation of the red rhenium(V) complex [ReO(Cl)(OMe)(L1)]. The semicarbazonato ligand is singly deprotonated and coordinates meridionally via the phosphorus atom and two nitrogen atoms. This unusual coordination mode of a semicarbazone is confirmed by IR and NMR spectroscopy and by the solid state structure of the product.
Recently, analytical second derivatives with respect to nuclear coordinates have been implemented in the Amsterdam density functional (ADF) package. This article presents the detailed formalism of that implementation. Calculations on small molecules such as methane show good agreement between the analytical and numerical frequencies. Calculations on benzene and larger molecules show that the analytical second derivatives code is 2 to 3 times faster than the numerical. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
We present the theoretical and technical foundations of the Amsterdam Density Functional (ADF) program with a survey of the characteristics of the code (numerical integration, density fitting for the Coulomb potential, and STO basis functions). Recent developments enhance the efficiency of ADF (e.g., parallelization, near order-N scaling, QM/MM) and its functionality (e.g., NMR chemical shifts, COSMO solvent effects, ZORA relativistic method, excitation energies, frequency-dependent (hyper)polarizabilities, atomic VDD charges). In the Applications section we discuss the physical model of the electronic structure and the chemical bond, i.e., the Kohn–Sham molecular orbital (MO) theory, and illustrate the power of the Kohn–Sham MO model in conjunction with the ADF-typical fragment approach to quantitatively understand and predict chemical phenomena. We review the “Activation-strain TS interaction” (ATS) model of chemical reactivity as a conceptual framework for understanding how activation barriers of various types of (competing) reaction mechanisms arise and how they may be controlled, for example, in organic chemistry or homogeneous catalysis. Finally, we include a brief discussion of exemplary applications in the field of biochemistry (structure and bonding of DNA) and of time-dependent density functional theory (TDDFT) to indicate how this development further reinforces the ADF tools for the analysis of chemical phenomena. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 931–967, 2001
A series of RuII complexes containing [(H)PNO] hydrazonic ligands were synthesised using different ruthenium sources such as [Ru(PPh3)3Cl2], [Ru(dmso)4Cl2] and [Ru(p-cymene)Cl2]2. The complexes were characterised by 1H NMR, 31P{1H} NMR, IR, FAB-MS, microanalysis and in some cases by X-ray diffraction analysis on a single crystal. The ligands show a great variety of different coordinating behaviours such as κ3-(H)PNO, κ2-(H)PN, κ1-(H)P and κ3-PNO, depending on the ruthenium precursor and on the synthetic experimental conditions. The complexes trans-[Ru(κ3-(H)PNO)(PPh3)Cl2] reacted with dmso to give the bis-chelate complex [Ru(κ3-PNO)2], [Ru(dmso)4]Cl2, OPPh3, HCl and Me2S, through an oxygen-transfer reaction from dmso to PPh3. A catalytic version of this reaction was also developed. The complexes obtained from [Ru(PPh3)3Cl2] were tested as homogeneous pre-catalysts for the coupling between benzoic acid and terminal alkynes to give the corresponding enol esters. High stereo- and regio-selectivity, up to 100 % (determined by 1H NMR), in favour of the (Z)-anti-Markovnikov products (Z)-alk-1-en-1-yl benzoate was observed. An ESI-MS monitoring of the catalytic couplings revealed that the enol ester formation occurs through an intermolecular attack of an external carboxylate anion onto a vinylidene–Ru intermediate of the type [Ru(PNO)(PPh3)(C=CH–C4H9)Cl]. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Complexes of Pt(II), Pd(II), and Ni(II) with the condensation derivative of 2-(diphenylphosphino)benzaldehyde and semioxamazide
were synthesized, characterized, and their antimicrobial activity was evaluated. The ligand and the complexes were characterized
by spectroscopic methods with the particular accent on NMR spectral analysis. For the palladium(II) complex, the crystal structure
was determined by X-ray analysis. In all the complexes the ligand is coordinated as a tridentate via a P, N, O donor set. The Pd(II) and Pt(II) complexes have a square planar geometry, whereas the geometry of the Ni(II) complex
is tetrahedral. The ligand showed antibacterial and antifungal activity, which was enhanced upon complexation.
The conductor-like screening model (COSMO) of solvation has been implemented in the Amsterdam density functional program
with maximum flexibility in mind. Four cavity definitions have been incorporated. Several iterative schemes have been tested
for solving the COSMO equations. The biconjugate gradient method proves to be both robust and memory-conserving. The interaction
between the surface charges and the electron density may be calculated by integrating over either the fitted or exact density,
or by calculating the molecular potential. A disk-smearing algorithm is applied in the former case to avoid singularities.
Several self-consistent field/COSMO coupling schemes were examined in an attempt to reduce computational effort. A gradient-preserving
algorithm for removing outlying charge has been implemented. Preliminary optimized radii are given. Applications to the benzene
oxide-oxepin valence tautomerization and to glycine conformation are presented.
Phosphino hydrazones derived from C(2)-symmetric hydrazines exhibit excellent catalytic activity and provide good enantioselectivities in the asymmetric Suzuki-Miyaura cross-coupling to axially chiral biaryls, in particular for the most challenging reactions of monocyclic, functionalized aryl bromides and triflates. X-ray analysis of preformed [Pd(P/N)Cl(2)] precatalysts [(P/N) = phosphino hydrazone] revealed a strong n-π conjugation in the hydrazone moiety, identified by a high planarity degree at the pyrrolidine N(sp(3)) atom, that makes rotations around N-N bonds inconsequential. The complexes are also characterized by an envelope-like conformation with the Pd atom placed at the opposite side to the 2-phenyl group on the nearest stereogenic center of the pyrrolidine group. The isolation and structural analysis of oxidative addition intermediates indicate that the configurational stability of Pd-C(Ar) bonds is dependent on the substitution pattern in the aryl bromide.
We have computed the proton affinities in water of archetypal anionic and neutral bases across the periodic table using the generalized gradient approximation (GGA) of density functional theory (DFT) at BP86/QZ4P//BP86/TZ2P. The main purpose of this work is to provide an intrinsically consistent set of values of the 298-K proton affinities in aqueous solution of all anionic (XHn-1-) and neutral bases (XHn) constituted by maingroup-element hydrides of groups 14-17 and the noble gases (i.e., group 18) along the periods 1-6. Hydration has little effect on the trends in PA values, especially in the case of the neutral bases. However, in the case of the anionic bases, hydration drastically reduces the magnitude of the PA values. Finally, we have studied how proton affinities in water are affected by methyl substitution at the protophilic center. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).
A new palladium(II) complex 1 of the condensation product of 2-(diphenylphosphino)benzaldehyde (dpba) and ethyl hydrazinoacetate (etha) was synthesized and characterized by elemental analyses, IR, and (1)H NMR spectroscopy. The bound ligand is a bidentate (PN chromophore), the remaining two coordination places being occupied by chloride ions in overall square planar geometry. The cytotoxic activity of the complex 1 and two related Pd(II) and Pt(II) complexes 2 and 3 was tested against a panel of four tumor cell lines. The activity of the complexes was similar to that of cisplatin, the most widely used metal-based antitumor drug. It is important to notice that complexes 2 and 3 were active to cisplatin-resistant U2-OS/Pt cells. Cell cycle alteration investigation, apoptotic assay and gelatin zymography in relation to invasion and metastasis of tumor cells, were performed with all the investigated complexes on Human cervix carcinoma (HeLa) cells. The results suggest that 1 has a similar effect to cisplatin, inducing apoptosis followed by arrest of cells in S phase of cell cycle, while 2 and 3 induce apoptosis without significant perturbations of cell cycle distribution.
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