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Monomeric and dimeric structures analysis and spectroscopic characterization of 3,5-difluorophenylboronic acid with experimental (FT-IR, FT-Raman, 1H and 13C NMR, UV) techniques and quantum chemical calculations
Supplementary resource (1)
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December 2014
... 4-Mercaptophenylboronic acid (4-mpba, C 6 H 7 BO 2 S) known in the literature with different synonym such as boronic acid 4-boronothiophenol, is a phenylboronic acid derivative. Phenylboronic acid and its derivatives have been studied extensively by spectroscopic and theoretical methods[2][3][4][5][6][7][8][9][10][11][12][13][14]. In the literature, there are several examples of 4-mpba, being used as a starting material for organic synthesis, nanoparticle science and engineering[15][16][17][18][19][20][21][22][23]. ...
... Therefore, the cc form can be evaluated as a non-planar structure. Similar observations are reported for some phenylboronic acids in the literature[14,30]. The most stable form, tc, however, has a planar structure and we have focused on this form and its dimer for geometrical and vibrational analysis. ...
... In the spectra of phenylboronic acid[2,5], 2,6dimethoxyphenylboronic acid[3], 2,4-dimethoxyphenylboronic acid[4], 2,3-difluorophenylboronic acid[30], vibrational bands were observed at 3280 (IR)/3428 (IR), 3335 (IR)/3278 (R), 3480 (IR)/3339 (IR), 3400 (IR)/3332 (IR) cm À1 , respectively. For 3,5difluorophenylboronic acid[14], these bands were not observed both in the IR and Raman spectra. The OH stretching modes are weakly polarized and therefore, they are generally not observed in the Raman spectrum. ...
4-Mercaptophenylboronic acid (4-mpba, C6H7BO2S) was investigated experimentally by vibrational spectroscopy. The molecular structure and spectroscopic parameters were studied by computational methods. The molecular dimer was investigated for intermolecular hydrogen bonding. Potential energy distribution analysis of normal modes was performed to identify characteristic frequencies. The present work provides a simple physical picture of the OH stretch vibrational spectra of 4-mpba and analogues of the compound studied. When the different computational methods are compared, there is a strong evidence of the better performance of the BLYP functional than the popular B3LYP functional to describe hydrogen bonding in the dimer. The findings of this research work should be useful to experimentalists in their quests for functionalised 4-mpba derivatives.
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... The vibrational spectra and molecular structure of the 4-chlorophenylboronic acids [14], 3-bromo- [15] and 4-bromophenylboronic acid [14], 3,4-and 3,5-dichlorophenylboronic acid [16,17], and 2,6dimethoxy phenylboronic acid [18] were studied experimentally and theoretically. Moreover, the experimental and theoretical investigation of the conformation, vibrational and electronic transitions of 2,3-and 3,5-difluorophenylboronic acid molecules [19,20], acenaphthene-5-boronic acid [21], methylboronic acid [22] and 2-Thienylboronic acid [23] were investigated. ...
... Bhat et al. [34] calculated B-C bond lengths at 1.566 Å and 1.567 Å in the most stable form for phenylboronic acid, respectively. In this study, the bond distances of B-C show well agreement with structurally similar molecules in the literature [14,15,[18][19][20][21]. ...
... The bond angles showed the small difference between the experimental values [9,12], this can be due to calculation belongs to vapor phase and experimental results belong to solid phase. One can quite easily see from Table 2, all the calculations of bond angles are in very consistency with the compared experimental values [14,15,[18][19][20][21]. ...
... There are many theoretical and experimental structural investigations on boronic acid derivatives such as 4-pyridineboronic acid [13], methylboronic acid [14], acenaphthene-5-boronic acid [15] and 2-thienylboronic acid [16]. Furthermore, conformational, vibrational or electronic properties of phenylboronic acid derivatives such as 4-chloroor -bromo-phenylboronic acid [17], 3,4-dichlorophenylboronic acid [18], 2,4-or 2,6-dimethoxy phenylboronic acids [19], [20], 2,3-difluorophenylboronic [21], 3-bromophenylboronic acid [22], 3,5-difluorophenylboronic acid [23], 3-fluorophenylboronic acid [24], 4-mercaptophenylboronic acid [25], 4-carboxy phenylboronic acid [26], 3-(acrylamido)phenylboronic acid [27], 5-bromo-2ethoxyphenylboronic acid [28] and pentafluorophenylboronic acid [29] were reported by combining both experimental and theoretical works. This research is a continuation of these previous studies [17]- [29] and according to the detailed literature survey there is no any theoretical or experimental studies on the structural and vibrational properties of 2,3-dmpba. ...
... According to direction of various substituents in the gas phase, 3,4-dichloro [18], 2,4-dimethoxy [19], 2,3-difluoro [21] and 3,5-difluoro phenylboronic acid [23] prefer to CT form whereas the CC conformer is the most stable for 2,6-dimethoxy phenylboronic acid [20]. Optimized relative energies and mole fractions for all forms of 2,3-dmpba in different medium are listed in Table 2. Computed optimize energies indicate that the CT form is more stable than CC, TC and TT forms by 7.77-9.57 ...
... The OH in-plane bending vibrations are occurring in the region 1330-1420 cm À1 . The spectra of alcohols and phenols determined in the liquid state show a broad absorption band in the 650-770 cm À1 and 570-710 cm À1 [38,40,41] region due to out-of-plane bending vibrations of OeH group. In the present study the broad band observed 3805 cm À1 in the FTIR spectrum and theoretical calculated at 3823, 3829 cm À1 are assigned to OeH stretching vibrations. ...
... The chemical shifts of aromatic ring protons (H 14 Table S3. Comparing the experimental data with the theoretical ones indicate that the DFT values are closer to experimental values, and the deviation between experimental and computed chemical shifts of these protons may be due to the presence of intermolecular hydrogen bonding and the effect of solvent [38], there by confirming the structure of title compound. ...
The structure of 4-Hydroxy-3-methoxycinnamaldehyde (4H3MC) has been analyzed by spectroscopic and theoretical investigations. The vibrational spectral analysis of title compound was characterized by FT-IR and FT-Raman in the mid IR region. The 1H and 13C NMR chemical shifts of title compound were recorded at 300 K in DMSO solution. The HOMO-LUMO energy was calculated for the molecule. The Global reactivity descriptors and molecular electrostatic surface potential (MESP) were obtained to get better insight on charge density distribution. Thermodynamic parameters such as heat capacity (C), entropy (S), enthalpy changes (H) also determined for the title compound at different temperatures. NPA and MPA charge distribution was investigated with the help of quantum chemical calculations. The optimized bond lengths, bond angles, vibrational wave numbers, chemical shift and electronic transitions showed the best agreement with the experimental results. The biological activites were carried out using PASS online data base prediction and hence, these molecules could be potential selective inhibitors of JAK2 that can be experimentally validated and their backbone structural scaffold could serve as building blocks in designing drug-like molecules for JAK2. Hence, the above docking study indicate that the binding affinity and hydrogen bond interactions of these molecule with respect to amino residues can be supportive evidence for the further studies in designing structure-based JAK2 kinase inhibitors may be of significant therapeutic importance.
... For the title molecule, the bands observed at 1316, 963, 907cm -1 (B3LYP), 1321,903 cm −1 (FT-IR) and 1321, 908 cm −1 (FT-RAMAN) are assigned as O-H in plane bending vibrations. These vibrations are matched with literature [16,17]. The O-H out of plane bending vibrations are theoretically computed at 532,469,404 and 350 cm -1 and peaks are observed at 536,468 cm -1 and 536,459,343 cm -1 in FT-IR and FT-Raman spectra respectively. ...
... The O-H out of plane bending vibrations are theoretically computed at 532,469,404 and 350 cm -1 and peaks are observed at 536,468 cm -1 and 536,459,343 cm -1 in FT-IR and FT-Raman spectra respectively. These values have shown good agreement with literature [16,17]. ...
The aim of this work is to study the possible stable, geometrical molecular structure, experimental and theoretical FT-IR and FT-Raman spectroscopic methods of 3-Methoxyphenyl boronic acid (3MPBA). FT-IR and FT-Raman spectra were recorded in the region of 4000–400 cm⁻¹ and 40000–50 cm⁻¹ respectively. The optimized geometric structure and vibrational wavenumbers of the title compound were searched by B3LYP hybrid density functional theory method with 6-311++G (d, p) basis set. The Selectedexperimentalbandswereassignedandcharacterizedonthebasisofthescaledtheoreticalwavenumbersby their potential energy distribution (PED) of the vibrational modes obtained from VEDA 4 program. Finally, the predicted calculation results were applied to simulated FT-IR and FT-Raman spectra of the title compound, which show agreement with the observed spectra. Whereas, it is observed that, the theoretical frequencies are more than the experimental one for O-H stretching vibration modes of the title molecule.
... These values are well agreed with observed bands at 1066 cm -1 and 1328, 1052,952 and, 902 in FT-IR and FT-Raman spectra respectively. These vibrations are also matched with literature [15,16]. 506,468,400 and 339 cm -1 are calculated frequencies assigned to out of plane C-H bending vibrations and bands observed FT-IR and FT-Raman spectra are at 484,404 cm -1 and 480,412,343 cm -1 respectively. ...
... 506,468,400 and 339 cm -1 are calculated frequencies assigned to out of plane C-H bending vibrations and bands observed FT-IR and FT-Raman spectra are at 484,404 cm -1 and 480,412,343 cm -1 respectively. These values have shown good agreement with literature [15,16]. ...
This paper reports the experimental and theoretical study on the structure and vibrations of 2-Methylphenyl boronic acid (2MPBA). The different spectroscopic techniques such as FT-IR (4000-400 cm⁻¹) and FT-Raman (4000-50 cm⁻¹) of the title molecule in the solid phase were recorded. The geometry of the molecule was fully optimized using density functional theory (DFT) (B3LYP) with 6-311++G(d, p) basis set calculations. The vibrational wavenumbers were also corrected with scale factor to take better results for the calculated data. Vibrational spectra were calculated and fundamental vibrations were assigned on the basis of the potential energy distribution (PED) of the vibrational modes obtained from VEDA 4 program. The calculated wavenumbers showed the best agreement with the experimental results. Whereas, it is observed that, the theoretical frequencies are more than the experimental one for O-H stretching vibration modes of the title molecule.
... The molecular structures of phenylboronic acid and its derivatives have been studied many authors for years [6][7][8][9][10][11][12][13][14][15]. Rettig and Trotter [6] studied crystal and molecular structures of phenylboronic acid. ...
... This work is a continuation of our previous studies [14,15,27] and the detailed literature survey showed that to the best of our knowledge neither theoretical (DFT) nor experimental spectroscopic study are performed on the conformation, vibrational IR and Raman NMR and UV-Vis spectra of 3FPBA. The detailed description of the title molecule was established both experimentally (FT-IR and FT-Raman, 1 H and 13 C NMR and UV-Vis spectra) and theoretically (DFT). ...
... The main intention of DOS plots illustrates the occupied and virtual molecular orbitals, chemical bonding and Energy gap of the molecules. The DOS spectrum exhibits the colours which is shown in red colour as a negative, green colour as a positive respectively [41]. ...
... The peak in the range 580 cm À1 corresponds to the bending vibration C-B. [36] 3.2. NMR spectrum of samples Figure 4 (CBE1 and CBE2) also confirms the chemical structure of PBA binding to epoxy resin using signal data from 13 C NMR spectra. ...
In this project, a novel flame retardant was synthesized using a modification of epoxy resin with phenylboronic acid in the presence of tetra-n-butyl ammonium bromide catalyst during reaction at 80–120 °C. The flame retardant was prepared from the polymerization process without solvent and two ratios of phenylboronic acid. Then, using this obtained material, epoxy coating formula 828 was prepared and the effect of adding this compound was investigated then by examining the properties, the optimal sample was obtained. The results of the FTIR, NMR, TGA and DSC analysis confirmed the successful synthesis of flame retardant compounds. The curves obtained from the calorimetric test showed an increase in the efficiency of coal production and thermal resistance of the samples containing flame retardants. The rate of thermal degradation of the samples decreased from 100% for the pure epoxy coating to 94% and 87% for BE1 and BE2 samples containing flame retardant, respectively. The limited oxygen index increased from 21.8% for the pure epoxy sample to 26.6% and 31.2% for BE1 and BE2 samples, respectively. Examination of flame resistance properties showed that the coating containing 20% by weight of flame retardant BE2 had better results.
... At the same time, the thermal ellipsoid plot in XRD has trans conformation. All other experimentally observed bond lengths and bond angles are comparable with the calculated values (see Table 2) and related literature [39,40]. ...
Carbohydrate sensing in an aqueous solution remains a very challenging area of interest. Using the idea of covalent reversible interaction between boronic acids and the diol groups in carbohydrates enable us to design a carbohydrate sensor 1-thianthrenylboronic acid (1T), which has high selectivity towards fructose. To elucidate the sensing and binding properties of 1T with sugars, we have incorporated theoretical (DFT and TD-DFT) and spectroscopic techniques. For an optimized geometry, the complete vibrational assignments were done with FT-IR and FT-Raman spectra. Physiochemical parameters were obtained by implementing frontier molecular orbital (FMO) analysis. Further, excited state properties were determined by performing TD-DFT calculations in solvent and these properties were in good agreement with the experiment. The steady state fluorescence measurements with varying concentration of sugars, revealed that the fluorescence intensity of boronic acid is enhanced by studied sugars due to the structural modification. We also noticed remarkable changes in fluorescence lifetimes and quantum yield after adding sugars. The article also reports influence of pH on boronic acid’s fluorescence intensity with and without sugars. The fluorescence of boronic acid increases with the increase in pH. These changes are due to acid–base equilibrium of boronic acid and led us to estimate the pKa value of 7.6. All the theoretical and experimental evidences suggested that 1T can be used as a possible fluorescent sensor for fructose. In addition, 1T showed very good affinity for Cu2+ ion with Ka = 150 × 102 M−1, which suggests that 1T can also be used as a chemosensor for Cu2+ ions.
... At the same time, the thermal ellipsoid plot in XRD has trans conformation. All other experimentally observed bond lengths and bond angles are comparable with the calculated values (see Table 2) and related literature [39,40]. ...
Carbohydrate sensing in an aqueous solution remains a very challenging area of interest. Using the idea of covalent reversible interaction between boronic acids and the diol groups in carbohydrates enable us to design a carbohydrate sensor 1-thianthrenylboronic acid (1T), which has high selectivity towards fructose. To elucidate the sensing and binding properties of 1T with sugars, we have incorporated theoretical (DFT and TD-DFT) and spectroscopic techniques. For an optimized geometry, the complete vibrational assignments were done with FT-IR and FT-Raman spectra. Physiochemical parameters were obtained by implementing frontier molecular orbital (FMO) analysis. Further, excited state properties were determined by performing TD-DFT calculations in solvent and these properties were in good agreement with the experiment. The steady state fluorescence measurements with varying concentration of sugars, revealed that the fluorescence intensity of boronic acid is enhanced by studied sugars due to the structural modification. We also noticed remarkable changes in fluorescence lifetimes and quantum yield after adding sugars. The article also reports influence of pH on boronic acid’s fluorescence intensity with and without sugars. The fluorescence of boronic acid increases with the increase in pH. These changes are due to acid–base equilibrium of boronic acid and led us to estimate the pKa value of 7.6. All the theoretical and experimental evidences suggested that 1T can be used as a possible fluorescent sensor for fructose. In addition, 1T showed very good affinity for Cu2+ ion with Ka = 150 × 102 M−1, which suggests that 1T can also be used as a chemosensor for Cu2+ ions.
... The Four bands that appeared at 1003, 1064, 1196, and 1329 cm À1 for pyrogallol were attributed to the in-plane bending vibrations (b) of CeH (Mohammed-Ziegler and Billes, 2002). The peaks observed at around 1244 and 1284 cm À1 were ascribed to OeH in-plane bending vibrations (Karabacak et al., 2014). Several peaks ranging from 1450 to 1650 cm À1 were prominent appeared, which corresponded to the CeC ring vibrations of pyrogallol (S et al., 2018). ...
Pyrogallol, an eco-friendly derivative of tannic, was a potential substitute of toxic depressant used in bismuth-molybdenum (Bi–Mo) sulfide ore flotation. However, unclear depression mechanisms of pyrogallol on bismuth sulfides hindered its further application in the industry. In this work, the effect of pyrogallol on the flotation performance of bismuthinite was evaluated using flotation tests, and associated interaction mechanisms were investigated by using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. Micro-flotation tests showed that pyrogallol exhibited excellent depressing performance to bismuthinite in the whole pH range tested (2–12). In the presence of 300 g/t pyrogallol, over 95% of bismuthinite was effectively depressed in the real flotation process at pH around 9. FTIR and XPS results demonstrated that pyrogallol was chemisorbed on bismuthinite through the interactions among Bi atoms exposed on the bismuthinite surface and O−H groups in pyrogallol. The adsorption mechanism was further ascertained by DFT calculations, which revealed that the Bi–O–C single bond and the five-membered ring complex models were involved in the chemisorption of pyrogallol on bismuthinite surface. The work presented here not only provides new insights into the inhibition mechanisms of pyrogallol on bismuthinite but also provides theoretical support for the industrial application of pyrogallol.
... Lately, frontier molecular orbitals (HOMO and LUMO) have been used to describe the chemical reactivity. The energy gap between the HOMO and LUMO can be used to determine the kinetic stability, chemical reactivity, optical polarizability, and chemical hardness and softness of a compound [31][32][33][34]. ...
Treatment of 3-methylcyclohexanone with ethyl formate in the presence of sodium methoxide afforded sodium (2-methyl-6-oxocyclohexylidene)methanolate which reacted with aminopyrazoles, aminotriazole, and aminotetrazole to produce fused quinazoline derivatives; its reactions with cyanothioacetamide, cyanoacetamide, and cyanoacetohydrazide gave tetrahydroquinoline-3-carbonitrile derivatives. The reactions of 8-methyl-2-sulfanyl-5,6,7,8-tetrahydroquinoline-3-carbonitrile with alkylating agents led to the formation of thieno[2,3-b]quinoline derivatives. DFT computational studies of the synthesized compounds were carried out using B3LYP/6−311+G** and HF/6−311+G** approximations. The calculated HOMO and LUMO energies showed that charge transfer occurs in their molecules
... A large number of studies concern the experimental analysis of monomeric and dimeric structures of various molecule types relative to theoretical calculations [19][20][21][22]. There have been reports on natural chalcones that form several dimeric forms and act as anti-viral or anti-cancer agents [23,24]. ...
This is the first study of the crystal structure of cardamonin (CA) confirmed using single-crystal XRD analysis. In the crystal lattice of CA, two symmetry independent molecules are linked by hydrogen bonds within the layers and by the π···π stacking interactions in the columns which lead to the occurrence of two types of conformations among the CA molecules in the crystal structure. To better understand the stability of these arrangements in both crystals and the gaseous phase, seven different CA dimers were theoretically calculated. The molecular structures were optimized using density functional theory (DFT) at the B3LYP/6-311G+(d,p) level and the spectroscopic results were compared. It was found that the calculated configurations of dimer I and III were almost identical to the ones found in the CA crystal lattice. The calculated UV-Vis spectra for the CA monomer and dimer I were perfectly consistent with the experimental spectroscopic data. Furthermore, enhanced emissions induced by aggregated CA molecules were registered in the aqueous solution with the increase of water fractions. The obtained results will help to further understand the relation between a variety of conformations and the biological properties of CA, and the results are also promising in terms of the applicability of CA as a bioimaging probe to monitor biological processes.
... The DFT computations have been used to study various molecular and spectroscopic properties of the molecules. The compounds like nicotinic acid N-oxide,24 sesquiterpene lactone, 25 mesitylene, 26 5-nitro-2-(4-nitrobenzyl) benzoxazole, 27 2-arylidene indanone, 28 3,5-difluorophenylboronic acid, 29 cyclohexanone oxime, 30 2-methylpyridine 1-oxide, 31 pycolinaldehydeoxime, 32 o-methoxybenzoates, 33 (E)-1-(4-bromobenzylidene)semicarbazide, 34 1,5-diphenylpenta-1,4-dien-3-one, 35 3-(2-Chloro 6-fluorophenyl)-1-(2-thienyl) prop-2-en-1one, 36 dihydropyrimidinone, 37 39 etc. have been studied to explore their structural, electronic, chemical, and spectroscopic facets. In the last decade majority of researchers are working on computational models utilizing some potential nanomaterials for theoretical aspects. ...
In the current examination, (E)-3-(4-chlorophenyl)-1-(2-hydroxyphenyl) prop-2-en-1-one has been studied to investigate geometrical entities, electronic properties, and chemical reactivity viewpoints. To inspect structural, spectroscopic, and chemical reactivity aspects, density functional theory method (DFT) at B3LYP/6-311G(d,p) basis set has been employed. The (E)-3-(4-chlorophenyl)-1-(2-hydroxyphenyl)prop-2-en-1-one has been synthesized and characterized by FT-IR, 1 HNMR, and 13 C NMR spectral techniques. The detailed investigation of bond lengths and bond angles is discussed to comprehend the geometrical framework. To explore its chemical behaviour, Mulliken atomic charges, molecular electrostatic potential surface, and electronic parameters are introduced. The imperative exploration of the electronic properties, such as HOMO and LUMO energies, was studied by the time-dependent DFT (TD-DFT) method. The dipole moment of the title molecule is 2.57 Debye with C1 point group symmetry. The most electropositive carbon and hydrogen atoms in the title molecule are C14 and H27 respectively. Amongst aromatic C=C, the C16-C18 is the longest, and C17-C19 is the shortest bond. The molecular electrostatic potential plot predicts the positive electrostatic potential is around hydrogen atoms. The vibrational assignments were made by comparing the experimental FT-IR absorption peaks with the scaled frequencies obtained using computational work. Besides, some significant thermochemical information is obtained using the same basis set using frequencies.
... Frontier molecular orbit, Global chemical reactivity descriptor, MEP, Contour map, HOMO and LUMO energy levels, Mulliken population analysis, Natural charges and NLO properties are calculated with the help of optimized structure [12]. The vibrational assignments are performed using VEDA 4.0 software [13] program. ...
... Recent studies have been made on the tri-substituted benzene ring system, which provides a strong evidence for the increase and decrease of OH vibrations [37]. The OeH in-plane bending vibrations show their presence in the region 1250e1150 cm À1 [38]. But it is complicated to identify due to interaction with hydrogen wagging vibrations in alcoholic group containing aromatic systems. ...
... Several articles have been published on experimental and computational studies on phenylboronic acid [13], 1H-indene-2-boronic acid [14] and 3, 5-difluorophenylboronic acid [15]. O. Alver et al. [16] studied the molecular structure, vibrational structural analysis and electronic properties of 3-(acrylamido)phenylboronic acid using DFT theory. ...
In this study, the structural and photophysical properties of 2-ethoxy-4-fluoro phenyl boronic acid (BA1) fluorescent compound was analysed using experimental spectroscopy, single crystal X-ray diffraction techniques and theoretical calculations were implemented using DFT and TD-DFT methods. The complete vibrational assignments of wave numbers were made on the basis of potential energy distribution (PED). The calculated HOMO-LUMO energies shows charge transfer within the molecule and the transitions were predicted to be as п-п∗. Besides, frontier molecular orbitals (FMO), molecular electrostatic potential (MEP), UV–Vis absorption spectra and Non-linear optical properties were also studied using the same method and basis set. The BA1 compound has been tested for sugar sensing applications by absorption and emission spectroscopic analysis, to understand BA1 with sugars (D-glucose and D-fructose) complexes. The fluorescence measurements of BA1 at physiological pH 7.5, demonstrated a phenomenal quenching response to fructose and glucose molecules by having a decrease in fluorescence intensity with 3.5 fold and 1.3 fold for 0 M–0.5 M concentration of fructose and glucose, respectively, which shows strong sugar binding affinity. The association and dissociation constants were calculated by employing Stern-Volmer equation. The Job's plot and the mass spectroscopic analysis was carried to know the stoichiometry ratio of binding. The counterpoise correction method was implemented to calculate the complexation energy of the BA1-sugar complexes. The fluorescence life time of the molecule was measured in the presence and absence of sugars. The obtained lifetimes were in comparison with the theoretically calculated lifetimeusing PhotochemCAD. All these results showed that, BA1 can readily bind with sugars and could play an important role in carbohydrate sensing applications.
... Two absorbance bands were observed, centered at 230 and 265 nm, respectively, corresponding to π−π* transitions. 38 The bilayer deposition was followed at λ max = 230 nm. ...
... According to the abovementioned references, in the present study, the OH stretching vibrations was observed and assigned at 3393 cm −1 in the FT-IR spectrum and calculated at 3854 cm −1 , it shows good agreement with the literature values. The in-plane-bending vibrations of OH group were observed in the region 1250-1150 cm −1 and are not much affected by hydrogen bonding unlike stretching and out-of-plane bending vibrations [33] . According to the reference, the OH in-plane-bending vibrations are assigned at 1305, 1267, 1205, 1160 cm −1 in the FT-IR spectrum and at 1297, 1275, 1218, 1164 cm −1 in the FT-Raman spectrum, the corresponding bands are calculated in the range 1291-1175 cm −1 . ...
Spectroscopic properties of 4-hydroxy carbazole have been characterized by analytical spectroscopic techniques with help of high level quantum chemical calculations. For the structural confirmation and to gain better insight on 4-hydroxy carbazole, the structural properties, vibrational assignments, chemical shifts, electronic properties and other molecular parameters were determined and comprehensively discussed. The molecular electrostatic potential surfaces (MESP) have been generated to isolate the reactive sites for electron rich and electron poor regions in this compound, and additionally confirmed with Mullikan atomic charge distribution analysis. The obtained experimental and theoretical results show an excellent correlation to confirm the molecular structure of 4-hydroxy carbazole.
... In the present study, the eOH stretching vibration was observed and assigned at 3399 cm À1 in the FT-IR spectrum and calculated at 3850 cm À1 , which shows good agreement with the previously reported results of K.W.Blessel et al. [9]. The in-plane-bending vibrations of eOH group were observed in the region 1250e1150 cm À1 and are not much affected by hydrogen bonding unlike stretching and out-of-plane bending vibrations [32]. According to the reference, the eOH in-plane-bending vibrations are assigned at 1262, 1222, 1166 cm À1 in the FT-IR spectrum and at 1265, 1211, 1183 cm À1 in the FT-Raman spectrum, whereas the corresponding values are calculated in the range of 1266-1107 cm À1 . ...
... Conformational analysis of 2-fluorophenylboronic acid and a series of 2-X-phenylboranes (X = Cl, Br, NH 2 , PH 2 , OH and SH) have been analyzed by Silla et al. [14]. Karabacak et al. [15,16] determined conformers and spectroscopic features of 3-bromophenylboronic acid and 3,5-difluorophenylboronic acid using experimental and theoretical techniques. Pharmaceutical importance of boronic acid and its derivatives drove us to investigate the molecular structural properties, vibrational and energetic data of 2TBA with a long-term objective to achieve a better understanding of the properties of such derivatives. ...
... At the optimized geometry for the title molecule no imaginary frequency modes were obtained, therefore, there is a true minimum on the potential energy surface was found. The calculated vibrational frequencies are scaled according to the B3LYP/6-311++G(d,p) basis set, the wavenumbers upper 1700 cm À1 scale with 0.958 and under 1700 cm À1 scale with 0.983 [33][34][35]. After scaling, the experimental and computed results show a good agreement. ...
... Aromatic carbons give signals in overlapped areas of the spectrum with chemical shift values from 100 to 150 ppm [57,58]. In our present investigation, the experimental chemical shift values of aromatic carbons are in the range of 165.17-113.19 ...
... Then the spectrum is obtained here, this spectrum is referred to as partial density of state (PDOS) that shows the contribution to each molecular orbital for selected specific atoms or functional groups. Another important feature of the DOS spectrum is to show MO configuration and their contributions to chemical bonding through the overlap population density of state (OPDOS) spectrum [38]. OPDOS is also known as COOP in the literature. ...
... Fig. 5 shows the TDOS (total density of states) plot provided a diagrammatic view of the molecular orbital contributions, computed by the GaussSum 3.0 program [32] at B3LYP/6-31G(d,p). Molecular orbital parameters such as electron affinity, ionization potential energy, chemical hardness and potential, electrophilicity index [50,51] which can be obtained by HOMO and LUMO orbital energies have been added to Table 3. ...
... The corresponding fitting equations are as follows: C ¼ À1:75097 þ 0:12454T À 6:69958 Â 10 À5 T 2 ðR 2 ¼ 0:9999Þ S ¼ 50:13492 þ 0:12562T À 3:40418 Â 10 À5 T 2 ðR 2 ¼ 1:0000Þ H ¼ À0:58141 þ 0:00937T þ 3:5739 Â 10 À5 T 2 ðR 2 ¼ 0:9997Þ As a result, the thermodynamical data supply helpful information for the further study on the 3,5-DFA. These results also showed good coherence with the previous work for the similar compound [67,68]. They can be used to calculate the other thermodynamic energies according to relationships of thermodynamic functions and estimate directions of chemical reactions according to the second law of thermodynamics in Thermochemical field. ...
The new series of donor-π-acceptor dyes have been designed using pyridine derivatives as a donor group and thienothiophene as a π-spacer group, which were linked via 10 acceptor groups. The highest occupied molecular orbital energies range from − 6.177 to − 5.786 eV, whereas the lowest unoccupied molecular orbital energies range from − 2.181 to − 3.664 eV. A6 dye has smaller energy gap, lower hardness, higher electrophilicity index, and good photovoltaic performance than other sensitizers. The lowest dihedral angle is observed in A1, A2, A6, A7, and A8 which are appropriate for intramolecular charge transfer between the molecules. The A8 has higher light harvesting efficiency, which increases the photovoltaic efficiency of the designed dye. The A6, A7, and A8 dyes spend less time in the excited state, which means they emit photons more efficiently than other dyes. The interaction between donor to π-spacer (red line) parts of the dyes has the bonding interaction (positive), and π-spacer to acceptor (blue line) parts of the dyes have the bonding and antibonding (negative) behaviours. The dyes A5 and A9 have 305.79 and 357.71 times higher β0 values than urea (0.781 × 10−30 esu) molecules. The spectral properties of the A6 dye strongly affect the structural modification.
The density functional theory (DFT) and time-dependent DFT (TD-DFT) approach B3LYP/6-311G (d,p) basic set were used to optimize the designed dyes. All the calculations are performed using Gauss view 6.0 and Gaussian 09 software. The density of state spectrum is plotted using Gauss sum 2.6.
Constructing oxygen vacancies (OVs) with desired concentration and stability on the surfaces of semiconductors has been demonstrated to be a powerful tactic to enhance their photocatalytic performances. Nevertheless, forming OVs usually requires rigorous conditions, and OVs harshly suffer from deactivation during photoreaction. Herein, a facile strategy is developed to introduce surface OVs with tunable concentrations and long-term stability in bismuth-based semiconductors (BBS) through organic small-molecule surface-bonding. Taking I-doped BiOCl (I-BiOCl) as a model photocatalyst and catechol and its derivatives as ligands, a series of organic/I-BiOCl bonded hybrid photocatalysts are successfully synthesized. Compared with I-BiOCl, hybrid photocatalysts exhibited substantially enhanced catalytic activity toward multiple contaminants removal. Experimental characterizations and DFT calculations reveal a strong interfacial interaction between organic ligands and BBS through the formation of Bi-O-C bonds, which lengthen Bi-O bonds within [Bi2O2]²⁺ structural units and reduce the formation energy of OVs, facilitating the escape of lattice O atoms and thus producing abundant surface OVs. More importantly, the concentration of OVs can be easily regulated by controlling the number of organic ligands, and the OVs exhibit high stability during photoreaction, attributing to the existence of high-valence-state Bi(3+x)+ that is near the OVs, which would not be re-oxidized by oxidative species like the low-valence-state Bi(3-x)+, that is, they would not be reset to original Bi³⁺. As a verification of its universality, the surface bonded strategy has been successfully extended to other BBS.
Molecular Dynamics-simulated OH•••O bonded-cyclic dimer structure, called Dc, has been proposed for 2,5-Dihydroxyterephthalic acid a potential organic linker in Hydrogen-bonded Organic Frameworks (HOF). Among many dimer species bound by inter-molecular OH•••O bonds, Dc was chosen because of its relatively highest lifetime of 18.3 ps as indicated by the radial distribution functions (RDF). Experimentally observed intense but broad down-shifted IR absorptions peak at ∼ 3023 cm⁻¹ and bands near 2556 cm⁻¹ combined with staggered occurrence of IR and Raman bands in other spectral regions suggested that the proposed cyclic dimer appeared to possess an extended quasi-centrosymmetric configuration. Upon optimization of Dc at B3LYP/6-311++G(d,p) level, it yielded geometry and vibrational spectra in agreement with experimental spectra. Further, we have characterized both intra- and inter-molecular OH•••O bonds in Dc using stabilization energy E⁽²⁾ and other molecular orbital (MO) properties from NBO analysis. Bond critical points (BCPs) and ring critical points (RCPs) deduced from electron density (ρ(r)), its laplacian (∇2ρ(r)) and potential energy density (v(r)) using AIM calculations have provided complementary perspectives. Additionally, a combination of quantitative analysis and graphical visualization of the charge regions where non-covalent interactions occur in real space intra- and inter-molecular OH•••O bonds, van der Waals and repulsive steric clash interactions have been obtained from NCI calculations.
Organic‐inorganic metal halide perovskites are regarded as one of the most promising candidates in the photovoltaic field, but simultaneous realization of high efficiency and long‐term stability is still challenging. Here, a one‐step solution‐processing strategy is demonstrated for preparing efficient and stable inverted methylammonium lead iodide (MAPbI3) perovskite solar cells (PSCs) by incorporating a series of organic molecule dopants of fluorophenylboronic acids (F‐PBAs) into perovskite films. Studies have shown that the F‐PBA dopant acts as a cross‐linker between neighboring perovskite grains through hydrogen bonds and coordination bonds between F‐PBA and perovskite structures, yielding high‐quality perovskite crystalline films with both improved crystallinity and reduced defect densities. Benefiting from the repaired grain boundaries of MAPbI3 with the organic cross‐linker, the inverted PSCs exhibit a remarkably enhanced performance from 16.4% to approximately 20%. Meanwhile, the F‐PBA doped devices exhibit enhanced moisture/thermal/light stability, and specially retain 80% of their initial power conversion efficiencies after more than two weeks under AM 1.5G one‐sun illumination. This work highlights the impressive advantages of the perovskite crystal cross‐linking strategy using organic molecules with strong intermolecular interactions, providing an efficient route to prepare high‐performance and stable planar PSCs.
The information of interactions is given by RDG versus sign( λ 2 ) ρ product of the sign of the second largest eigenvalue of electron density Hessian matrix and electron density) investigated by RDG surface analysis.
5-Bromoisophthalic acid is a potential organic linker in Hydrogen-bonded Organic Frameworks (HOFs). Its H-bonding properties would be determinants, among others, in optimizing the reversible structural transformations, dissolution and re-crystallization, low densities and high porosity. In the present study, a DFT cyclic dimer model computed at B3LYP/cc-pVDZ level based on inter-molecular –OH•••O bonding has been proposed. The proposed cyclic dimer model fits observed vibrational IR and Raman spectral features. Computed chemical shifts for the protons in 5-Bromoisophthalic acid monomer agree with the experimental ¹H NMR values in d6-DMSO which dissociates the cyclic dimer into monomers. In the OH (Acceptor) •••O– (Donor) bonding, NBO, AIM and NCI calculations have provided a satisfactory electronic characterization based on orbital overlaps, electron density and associated topological, non-covalent interaction properties consistent with structural and vibrational analysis.
The present study focuses on the use of borax composite sodium silicate activator (B) in place of water glass (S) in the fly ash–GGBS composite (4:1) geopolymerization. The substituent is favoured as it delivers advantages such as increased setting time and workability by mitigating the agglomeration of flocks without affecting the compressive strength of the geopolymer. Microstructural changes of boroaluminosilicate were studied with the help of ATR-FT-IR and MAS NMR. Rheology studies indicated that the borax composite pastes display shear thinning behaviour with low yield stress and fit well with the Bingham model. In-situ ATR-FT-IR spectrum revealed the severing of silica bonds by soluble [BO4] and its incorporation into the silicate backbone resulted in the drop in of Si–O–T asymmetry vibration response. The NMR spectral changes of ²⁹Si,²⁷Al and ¹¹B nuclei environment in geopolymeric tetrahedral network showed that the fraction of [SiO4] and [BO4] increases upon borax addition with the diminished fraction of B³ non-rings without any specific changes in Al coordination. The tetrahedral boron absorption band in the wave numbers at 1380–1310 cm⁻¹ and1134 cm–1is observed in FT-IR and its configuration is compatible in the reaction product.
The conformational stability, vibrational frequencies, and thermodynamic parameters of 2-fluoro-4-pyridineboronic acid (FPB, C5H5BFNO2) are theoretically predicted using DFT-B3LYP with 6–31G(d), 6–31+G(d), and 6–311++G(d,p) basis sets employing the Gaussian 09 software. According to the internal rotation of two hydroxyl groups around the C–B bond, four conformers are suggested: TC, CT, TT, and CC (C/T refer to the cis/trans positions of O10-H15 and O9-H14 groups towards the C–B bond). The results of calculations favor the TC conformer with a 70% relative population compared with low values of 28%, 1.5%, and 0.06% for CT, TT, and CC, respectively. An additional calculation in the solid state (CASTEP) are performed for a molecule per unit cell (C1 symmetry) for all conformers using the DFT-PBE method. The TC conformer is also favored by 2.5 kJ/mol, 2.9 kJ/mol and 16.3 kJ/mol for conformers CT, TT and CC, respectively. TC is the most stable conformer owing to O9…H15, O10…H12 and F7…H11 intramolecular hydrogen bonding. Additionally, 13C NMR chemical shifts are predicted for the TC conformer by means of B3LYP/6-311++G(d,p) calculations utilizing the GIAO approximation and the PCM solvation model. To precisely assign the observed IR bands vis. the estimated vibrational frequencies, a normal coordinate analysis (NCA) is carried using the calculated force constants. The calculated wavenumbers and IR intensities of the TC form are in good similarity with those experimentally observed. With the aid of the potential energy surface scan (2D and 3D), the OH barrier to internal rotations is estimated using the optimized structural parameters from the B3LYP method with the 6–311++G(d,p) basis set. The results are debated herein and compared with similar available molecules.
Rapid development of research on the chemistry of boronic acids is connected with their applications in organic synthesis, analytical chemistry, materials’ chemistry, biology and medicine. In many applications Lewis acidity of boron atoms plays an important role. Special group of arylboronic acids are fluoro-substituted compounds, in which the electron withdrawing character of fluorine atoms influences their properties. The present paper deals with fluoro-substituted boronic acids and their derivatives: esters, benzoxaboroles and boroxines. Properties of these compounds, i.e. acidity, hydrolytic stability, structures in crystals and in solution as well as spectroscopic properties are discussed. In the next part examples of important applications are given.
Brønsted acidic ionic liquids (BAILs) can play a dual role, as a solvent and as a catalyst, in many reactions. However, molecular details of the catalytic mechanism are poorly understood. We present here a density functional theory (DFT) study for the catalytic mechanism of the transesterification of methyl ester (ME) with trimethylolpropane (TMP), in the presence of three representative BAILs, namely, N-methylimidazole-IL, pyridinium-IL, and triethylamine-IL. The deprotonation of the BAIL cation and the transesterification step are investigated. Key inter- and intra-molecular hydrogen bonds (HBs) that govern the catalytic performance of BAILs were identified and analyzed using natural bond orbital (NBO) and atoms in molecule (AIM) methods. For the deprotonation of BAILs, it was found that the intermolecular O-HO HB between the hydroxyl group of TMP and the oxygen of the sulfonic group of BAIL was indispensable for proton transfer. DFT computed free energy barriers for the transesterification step are in excellent agreement with the experimental results only after taking into account the BAIL cation-anion interaction in terms of HBs in which the O-HO between the hydroxyl group of the anion and the oxygen of the sulfonic group of the cation was the strongest HB, suggesting the role of the anion in governing the catalytic activity of BAILs. The existence of the HBs suggested by DFT calculations was further validated using in situ FTIR experiments/ATR-FTIR.
4-Ferrocenyl-2-fluorophenylboronic acid was obtained from ferrocene in two steps. In crystal, this compound forms a dimer due to the O–H...O hydrogen bonds and exhibits a stacking-interaction between benzene rings (∼3.47 Å), combining the dimers in chains.
One of the most significant aromatic amines is aniline, a primary aromatic amine replacing one hydrogen atom of a benzene molecule with an amino group (NH2). This study reports an experimental and theoretical investigation of 2,5-difluoroaniline molecule (2,5-DFA) by using mass, ultraviolet-visible (UV–vis), 1H and 13C nuclear magnetic resonance (NMR), Fourier transform infrared and Raman (FT-IR and FT-Raman) spectra, and supported with theoretical calculations. Mass spectrum (MS) of 2,5-DFA is presented with their stabilities. The UV-vis spectra of the molecule are recorded in the range of 200–400 nm in water and ethanol solvents. The 1H and 13C NMR chemical shifts are recorded in CDCl3 solution. The vibrational spectra are recorded in the region 4000–400 cm−1 (FT-IR) and 3500–10 cm−1 (FT-Raman), respectively. Theoretical studies are underpinned the experimental results as described below; 2,5-DFA molecule is optimized by using B3LYP/6-311++G (d,p) basis set. The mass spectrum is evaluated and possible fragmentations are proposed based on the stable structure. The electronic properties, such as excitation energies, oscillator strength, wavelengths, frontier molecular orbitals (FMO), HOMO and LUMO energies, are determined by time-dependent density functional theory (TD-DFT). The molecular electrostatic potential surface (MEPs), density of state (DOS) diagrams are also prepared and evaluated. In addition to these, reduced density gradient (RDG) analysis is performed, and thermodynamic features are carried out theoretically. The NMR spectra (1H and 13C) are calculated by using the gauge-invariant atomic orbital (GIAO) method. The vibrational spectra of 2,5-DFA molecule are obtained by using DFT/B3LYP method with 6-311++G (d,p) basis set. Fundamental vibrations are assigned based on the potential energy distribution (PED) of the vibrational modes. The nonlinear optical properties (NLO) are also investigated. The theoretical and experimental results give a detailed description of the structural and physicochemical properties of the title molecule and contribute to understanding of the nature of di-substituted aniline derivatives.
Possible stable conformers, geometrical molecular structures, vibrational properties as well as band assignments, nuclear magnetic shielding tensors of 2-Fluoro-3-Methylpyridine-5-Boronic Acid (2F3MP5BA) were studied experimentally and theoretically using FT-IR, Raman, (CP/MAS) NMR and XRD spectroscopic methods. FT-IR and Raman spectra were evaluated in the region of 3500-400 cm(-1), and 3200-400 cm(-1), respectively. The optimized geometric structures, vibrational wavenumbers and nuclear magnetic shielding tensors were examined using Becke-3 Lee-Yang-Parr (B3LYP) hybrid density functional theory method with 6-311++G(d, p) basis set. H-1,C-13 NMR chemical shifts were calculated using the gauge invariant atomic orbital (GIAO) method. H-1, C-13, APT and HETCOR NMR experiments of title molecule were carried out in DMSO solution. C-13 CP/MAS NMR measurement was done with 4 mm zirconium rotor and glycine was used as an external standard. Single crystal of 2F3MP5BA was also prepared for XRD measurements. Assignments of vibrational wavenumbers were also strengthened by calculating the total energy distribution (TED) values using scaled quantum mechanical (SQM) method.
Possible stable conformers and geometrical molecular structures of 6-Bromo-3-Pyridinyl Boronic acid (6B3PBA; C5H5BBrNO2) were studied experimentally and theoretically using FT-IR and Raman spectroscopic methods. FT-IR and Raman spectra were recorded in the region of 4000–400 cm−1 and 3700–400 cm−1, respectively. The structural properties were investigated further, using 1H, 13C, 1H coupled 13C, HETCOR, COSY and APT NMR techniques. The optimized geometric structures were searched by Becke-3–Lee–Yang–Parr (B3LYP) hybrid density functional theory method with 6-311++G(d, p) basis set. Vibrational wavenumbers of 6B3PBA were calculated whereby B3LYP density functional methods including 6-311++G(d, p), 6-311G(d, p), 6-311G(d), 6-31G(d, p) and 6-31G(d) basis sets. The comparison of the experimentally and theoretically obtained results using mean absolute error and experimental versus calculated correlation coefficients for the vibrational wavenumbers indicates that B3LYP method with 6-311++G(d, p) gives more satisfactory results for predicting vibrational wavenumbers when compared to the 6-311G(d, p), 6-311G(d), 6-31G(d, p) and 6-31G(d) basis sets. However, this method and none of the mentioned methods here seem suitable for the calculations of OH stretching modes, most likely because increasing unharmonicity in the high wave number region and possible intra and inter molecular interactions at OH edges lead some deviations between experimental and theoretical results. Moreover, reliable vibrational assignments were made on the basis of total energy distribution (TED) calculated using scaled quantum mechanical (SQM) method.
In the present paper, effects of concentration of sodium hydroxide solution (NaOH) and curing temperature on properties of boroaluminosilicate fly ash-based geopolymers are studied. Geopolymers, cement-free eco-friendly construction materials, are formed by alkali activation of an aluminosilicate source. By changing the alkali activator from a silica-rich to boron-rich one, it may be possible to have boroaluminosilicate binders. Results obtained indicated formation of B-O bonds in these types of geopolymers. Increasing NaOH concentration was observed to reduce compressive strength due to changes occurring in the nature of reactions between the alkali activator and fly ash particles. Establishment of unwanted complex compounds as well as formation of non-stoichiometric aluminosilicate binders instead of boroaluminosilicate ones were supposed to be the main reasons for this strength reduction. Additionally, curing temperature had a strong effect on the formation of new phases. Various microstructures were observed in boroaluminosilicate binders, where the presence of needle-like crystals was the main difference between these types of geopolymers and the aluminosilicate one.
In this work, a method for incorporating fly ash in constructional technology was developed by production of boroaluminosilicate geopolymers. These new class of geopolymers were appropriately synthesized from mixtures of fly ash and anhydrous borax and compressive strengths as high as 64 MPa were achieved by using suitable amount of borax. Different types of microstructures were observed by changing mixture proportion of the specimens. All of specimens revealed a brittle fracture with no crack branching in the mixture. Additionally, less unreacted fly ash particle was observed in the considered pastes indicating a totally different fracture mechanism in boroaluminosilicate geopolymers than aluminosilicate ones. FT-IR analyses of the mixtures revealed an additional B–O bond in comparison with aluminosilicate geopolymers. It was shown that this bond is a key factor to determine compressive strength and specimens with no B–O bond have lower strengths.
Stable conformers and geometrical molecular structures of 1H-indene-2-boronic acid (I-2B(OH)(2)) were studied experimentally and theoretically using FT-IR and FT-Raman spectroscopic methods. FT-IR and FT-Raman spectra were recorded in the region of 4000-400 cm(-1), and 3700-400 cm(-1), respectively. The optimized geometric structures were searched by Becke-3-Lee-Yang-Parr (B3LYP) hybrid density functional theory method with 6-31++G(d,p) basis set. Vibrational wavenumbers of I-2B(OH)(2) were calculated using B3LYP density functional methods including 6-31++G(d,p) basis set. Experimental and theoretical results show that density functional B3LYP method gives satisfactory results for predicting vibrational wavenumbers except OH stretching modes which is probably due to increasing unharmonicity in the high wave number region and possible intra and inter molecular interaction at OH edges. To support the assigned vibrational wavenumbers, the potential energy distribution (PED) values were also calculated using VEDA 4 (Vibrational Energy Distribution Analysis) program.
In the crystal structure of the title compound, C6H 8B2O4, centrosymmetric 1,4-phenylenediboronic acid molecules are linked by characteristic hydrogen bonding of B(OH) 2 groups. Primary association involves the formation of centrosymmetric cyclic dimers which leads to the formation of linear chains; these, in turn, associate by secondary hydrogen bonding, via unit-cell translations in the a axis direction, to form sheets. © 2004 International Union of Crystallography Printed in Great Britain - all rights reserved.
Ab initio and density functional computations of the vibrational (IR) spectrum, molecular geometry, the atomic charges and molecular polarizabilities were carried out on melatonin. The FTIR spectrum of melatonin is recorded in solid phase. Assignments were made in accordance with the calculated and experimental spectra. The UV spectrum was measured in methanol. In order to gain some insight into the recorded spectrum, the quantum mechanical calculations were performed for melatonin using both ZINDO/CIS and TD DFT with B3LYP/6-31G* basis set. In addition, isotropic 1 H- and 13C-nuclear magnetic shielding constants of this compound were calculated by employing the direct implementation of the gauge including-atomic-orbital (GIAO) method at the B3LYP density functional theory using 6-311G basis set. Theoretical values are compared to the experimental data.
Crystals of the title compound, C6F5B(OH)(2), were obtained from an attempted recrystallization of (C6F5)(3)B3O3.Et3PO from THF/hexane solution. The central B atom of the boronic acid has a trigonal planar configuration with two hydroxyl groups and one pentafluorphenyl substituent.
New boron-containing anion active functional copolymers are synthesized by complex-radical copolymerization of 4-vinylphenyl boronic acid and maleic or citraconic anhydrides with 2,2′-azobisisobutyronitrile as an initiator in DMF at 70 °C under nitrogen atmosphere. Macrobranched derivatives of these copolymers are synthesized by the partial grafting with α-hydroxy,ω-methoxy-poly(ethylene oxide) and incorporation with poly(ethylene imine). Effect of H-bonding on the formation of self-assembled supramolecular macrocomplexes with higher crystallinity and thermal stability was observed and confirmed by FTIR, and 1H(13C DEPT-135( NMR spectroscopy, X-ray diffraction, DSC and TGA analyses of monomer, homopolymer, copolymer and grafted copolymer systems. Observed water solubility, biocompatibility and high density of acid groups in macromolecules allow these anion active B-containing copolymer systems for the developing new generation of effective antitumor agents, polymeric carriers for enzymes, gene delivery and boron neutron capture therapy.
Provides an introduction to those needing to use infrared spectroscopy for the first time, explaining the fundamental aspects of this technique, how to obtain a spectrum and how to analyse infrared data covering a wide range of applications. Includes instrumental and sampling techniques Covers biological and industrial applications Includes suitable questions and problems in each chapter to assist in the analysis and interpretation of representative infrared spectra Part of the ANTS (Analytical Techniques in the Sciences) Series.
The experimental and theoretical vibrational spectra of 2-fluorophenylboronic acid (2fpba) were studied. The Fourier transform Raman and Fourier transform infrared spectra of the 2fpba molecule were recorded in the solid phase. The structural and spectroscopic analysis of the molecule was carried out by using Hartree-Fock and density functional harmonic calculations. For the title molecule, only one form was found to be the most stable structure, by using B3LYP level with the 6-31++G(d,p) basis set. Selected experimental bands were assigned and characterized on the basis of the scaled theoretical wavenumbers by their total energy distribution (TED). The 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the 2fpba molecule were calculated using the Gauge-Invariant- atomic orbital (GIAO) method in DMSO solution using IEF-PCM model and compared with the experimental data. Finally, geometric parameters, vibrational wavenumbers and chemical shifts were compared with available experimental data of the molecule. Copyright © 2009 John Wiley & Sons, Ltd.
The title compound, C6H6BFO2, is a versatile building block in organic synthesis. In the crystal structure, intermolecular O—H⋯O hydrogen bonds link the molecules into dimers, which may be effective in the stabilization of the crystal structure.
Several new synthetic methods for B-10 containing nucleoside derivatives have been developed. (1) The palladium-catalyzed coupling reaction of halogenated nucleoside derivatives with the aryltin compound having a boronic moiety proceeds chemoselectively at the C-Sn bond rather than the C-B bond to give boron-containing nucleoside derivatives. (2) The 1,2-addition reaction of the carbanions, generated from nucleoside derivatives, with aromatic aldehydes having boronic moiety gives boronated nucleoside derivatives bearing a hydroxy group. (3) The reaction of nucleoside derivatives having an acetylene group with decaborane produces carborane containing nucleosides. (4) Boron containing amino acid derivatives, which have both hydrophilic and liphophilic moiety, have been prepared. The cytotoxicity of the boron-containing biorelated compounds, and their application to neutron capture therapy are discussed.
Crystals of the title compound, C6F5B(OH)2, were obtained from an attempted recrystallization of (C6F5)3B3O3·Et3PO from THF/hexane solution. The central B atom of the boronic acid has a trigonal planar configuration with two hydroxyl groups and one pentafluorphenyl substituent.
The title compound, C7H5FO3, is nearly planar, and the dihedral angle between the phenyl and carboxyl groups is 4.0 (1)°. There are intramolecular O—H…O and intermolecular O—H…O and O—H…F hydrogen bonds, forming ribbons along the c axis.
In this study, the Fourier-transform infrared (FT-IR) and FT-Raman spectra of 3,5-dichlorophenylboronicacid (3,5-dcpba) were
recorded in the solid phase. The structural and spectroscopic analysis of the 3,5-dichlorophenylboronic was made by using
density functional harmonic calculations. There are three conformers for thismolecule. The computational results diagnose the
most stable conformer of 3,5-dcpba as the ct form. The geometrical parameters and energies have been obtained for all three
conformers from DFT (B3LYP) with 6-311++G(d,p) basis set calculations. The vibrations of stable and unstable conformers of
3,5-dcpba are researched by using quantum chemical calculations. The complete assignments were performed on the basis
of the total energy distribution (TED) of the vibrational modes calculated with the scaled quantum mechanics (SQM) method.
The stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using
the natural bond orbital (NBO) analysis. The results show that the charge in electron density (ED) in the ¥ð
. and ¥ò
. antibonding
orbitals and E2 energies confirms the occurrence of ©¥ntermolecular charge transfer (ICT) within the molecule. Finally, the
calculation results were applied to simulated infrared and Raman spectra of the title compound, which show agreement with
the observed spectra. Copyright�c 2009 JohnWiley & Sons, Ltd.
Specificity differences between the S1-pockets of subtilisin B. lentus (SBL), and its M222C/S mutants have been explored with boronic acid inhibitors. Similar binding trends were noted, with 2,4-dichlorophenylboronic acid being the best overall inhibitor for each enzyme. In addition, a correlation between inhibitor binding and the electrophilicity of boron was found for both the M222C and M222S enzymes.Specificity differences between the S 1-pockets of subtilisin from B. lentus (SBL), and its M222C/S mutants, have been explored with boronic acid inhibitors. Similar binding trends were noted, with 2,4-dichlorophenyl boronic acid being the best overall inhibitor for each enzyme. In addition, a correlation between inhibitor binding and the electrophilicity of boron was found for both M222C and M222S enzymes.
The infrared absorption spectra of gaseous and liquid 1,2,4,5‐tetrafluorobenzene have been obtained in the region 2–22μ with the aid of LiF, NaCl, and KBr prisms. The Raman spectrum of the liquid phase has been photographed with a three‐prism glass spectrograph of linear dispersion 15 A/mm at 4358A. Relative intensities and depolarization ratios have been measured for the stronger Raman bands. A complete assignment of fundamental vibration frequencies is made and the spectra are interpreted in detail. The values of the nonplanar fundamental frequencies are checked by normal coordinate analysis.
The infrared absorption spectra of liquid p‐fluorochloro‐, p‐fluorobromo‐, and p‐fluoroiodobenzene, and the stronger bands of the first two compounds in the gaseous state, have been obtained in the region 2—38μ with NaCl and CsBr prisms. The Raman spectra of the compounds in the liquid state have been photographed with a 3‐prism glass spectrograph of linear dispersion 15 A/mm at 4358 A, and depolarization ratios have been measured for the stronger Raman bands of p‐fluorochloro‐ and p‐fluorobromobenzene. Complete assignments of the fundamental vibrational frequencies have been made, and the spectra are interpreted in detail.
The laser Raman and i.r. spectra of the liquid 1-fluoro 2:4-dinitrobenzene are investigated. Depolarization ratios of the Raman lines have been calculated. Vibrational frequencies observed in both the spectra have been correlated and assigned to various normal modes of vibrations assuming Cs symmetry for the molecule.
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Possible stable forms and molecular structures of 2,6-dimethoxyphenylboronic acid (2,6-dmpba) were studied experimentally and theoretically using FT-IR, Raman, liquid–solid state NMR and XRD spectroscopic methods. FT-IR and Raman spectra were recorded in the region of 4000–200cm−1. 13C cross-polarization magic-angle spinning NMR and liquid phase 1H, 13C and HETCOR NMR spectra of 2,6-dmpba ((CH3O)2C6H3B(OH)2) were reported. The optimized geometric structures concerning to the minimum on the potential energy surface was investigated by Becke-3-Lee-Yang-Parr (B3LYP) hybrid density functional theory method together with 6-31++G(d,p) basis set. Vibrational wavenumbers and 1H, 13C NMR chemical shifts of 2,6-dmpba were calculated by means of B3LYP density functional methods with 6-31++G(d,p) basis set. Comparison between the experimental and theoretical results indicates that density functional B3LYP method is able to provide satisfactory results for predicting vibrational wavenumbers and nuclear magnetic shielding tensors. Furthermore, reliable vibrational assignments were made on the basis of total energy distribution (TED) calculated with scaled quantum mechanical (SQM) method.
This paper deals with the ground state of an interacting electron gas in an external potential v(r). It is proved that there exists a universal functional of the density, Fn(r), independent of v(r), such that the expression Ev(r)n(r)dr+Fn(r) has as its minimum value the correct ground-state energy associated with v(r). The functional Fn(r) is then discussed for two situations: (1) n(r)=n0+n(r), n/n01, and (2) n(r)= (r/r0) with arbitrary and r0. In both cases F can be expressed entirely in terms of the correlation energy and linear and higher order electronic polarizabilities of a uniform electron gas. This approach also sheds some light on generalized Thomas-Fermi methods and their limitations. Some new extensions of these methods are presented.
The title compound, C6H6BFO2, is a versatile building block in organic synthesis. In the crystal structure, intermolecular O-H (.) (.) (.) O hydrogen bonds link the molecules into dimers, which may be effective in the stabilization of the crystal structure.
In this work, the Fourier transform Raman and Fourier transform infrared spectra of pentafluorophenylboronic acid (= pfpba) were recorded in the solid phase. The structural and spectroscopic analysis of the pentafluorophenylboronic acid were made by using ab initio and density functional harmonic and anharmonic calculations. Geometric parameters, Infrared and Raman spectra were compared with single crystal X-ray diffraction data of the molecule. Previous proposed structure for the pfpba derived from the infrared spectra are consistent with the X-ray diffraction data and theoretical calculations.
The differential affinity of boron towards the oxygen and nitrogen lone pairs of electrons in 2-aminocarbonyl-phenylboronic acid (2-AC-PBA) and its corresponding ester, ethanediol (2-aminocarbonyl) phenylboronate (ED-2-AC-PB), has been investigated computationally using both density functional theory and second-order Møller–Plesset perturbation theory. In vacuo, the optimized boron–oxygen or boron–nitrogen distances in conformers of 2-AC-PBA, that involve either an intramolecular five-membered (:OC–CC–B) or (:N–C–CC–B) ring motif, are long, ∼2.4–3.0Å, and the calculated charge distribution and 11B chemical shifts for these structures are not indicative of the presence of a B–O or B–N dative bond. In a variety of solvents, however, the optimized B–O or B–N distances from self-consistent reaction field calculations are much shorter, ∼1.7–1.8Å, and the charge distribution and 11B chemical shifts are consistent with the formation of dative bonds. The results for the ester ED-2-AC-PB are similar, although a conformer with a B–N dative bond is also found in vacuo. The calculations show that conformers with the (:OC–CC–B) ring motif are consistently lower in energy than the corresponding conformers with the (:N–C–CC–B) ring motif, both in vacuo and in solution.
The boronic acid functional group has been incorporated into various biologically important compounds. In order to study this class of compounds better with molecular mechanics, five alkyl- and arylboronic acids were calculated using ab initio methods (Spartan) at the RHF/6–31G* level. MM3 force field parameters were developed based on the theoretically calculated geometries, vibrational spectra, and torsional profiles. © 1998 John Wiley & Sons, Ltd.
The possible stable forms and molecular structures of 2,4-dimethoxyphenylboronic acid (2,4-dmpba) have been experimentally and theoretically studied using FT-IR, Raman and solution and solid state NMR spectroscopic methods. FT-IR and Raman spectra were recorded in the region of 4000–400cm−1. 13C cross-polarization magic-angle spinning NMR and solution phase 1H, 13C and HETCOR NMR spectra of 2,4-dmpba ((CH3O)2C6H3B(OH)2) have been reported. The optimized geometric structures concerning to the minimum on the potential energy surface was investigated by Becke-3-Lee-Yang-Parr (B3LYP) hybrid density functional theory method together with 6-31++G(d,p) basis set. The vibrational wavenumbers and 1H, 13C NMR chemical shifts of 2,4-dmpba have been calculated by means of B3LYP density functional methods with 6-31++G(d,p) basis set. Reliable vibrational assignments were made on the basis of total energy distribution (TED) calculated with scaled quantum mechanical (SQM) method. Comparison between the experimental and the theoretical results indicates that density functional B3LYP method is able to provide satisfactory results for predicting vibrational wavenumbers and nuclear magnetic shielding tensors. Furthermore, the cis–trans (ct) form of 2,4-dmpba with Cs point group has been found to be the most stable conformer.
The acceptor strength of a number of Lewis-acidic fluorinated triarylboron compounds has been established and shown to depend on the amount and position of fluorine substitution. The donor strength of tert-butyl-phosphine has been found to be greater than phosphine towards these acceptor compounds; two series of adducts have been characterised and reversible adduct formation has been demonstrated for some adducts. Crystal structures of the phosphine adducts of tris(pentafluorophenyl)boron and tris(2,6-difluorophenyl)boron have been compared with those of the tert-butylphosphine adducts of tris(pentafluorophenyl)boron and tris(3,4,5-trifluorophenyl)boron to show a correlation between the length and the strength of the adduct bond. Mixing aryl groups in the acceptor compounds has not produced new adducts. The strong acceptor compounds have been found to form unstable adducts with water which act as drying agents ultimately producing arylboric acids; the crystal structure of (2,6-difluoropheny)dihydroxyborane has been determined.
Crystals of phenylboronic acid are orthorhombic, a = 17.9049(7), b = 115.3264(5), c = 9.8113(2) Å, Z = 16, space group Iba2. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to a final R of 0.031 and Rw of 0.041 for 1409 reflections with I ≥ 3σ(I). The asymmetric unit consists of two independent molecules linked by a pair of O—H … O hydrogen bonds. Each dimeric unit is also hydrogen bonded to four other such units (at ) to form an infinite array of layers which stack along the c axis. Mean bond lengths corrected for libration (rms deviations from the mean in parentheses) are: O—B, 1.371(7), B—C, 1.565(3), and C—C(phenyl), 1.394(11) Å.
The infrared spectra of phenylboronic acid, normal and deuterated, and diphenyl phenylboronate have been recorded in the range 4000–300 cm−1 and assignments of the observed frequencies have been made. The spectrum of the acid in the OH stretching region shows evidence of intramolecular hydrogen bonding. The spectrum of diphenyl phenylboronate has been interpreted by analogy with monosubstituted benzene derivatives. The two different environments of the phenyl groups in this molecule give rise to splitting of two of the characteristic vibrations of the benzene ring near 760 and 680 cm−1.
This eight-chapter book was originally published in German in 1984. Although a few more recent references were added during translation, the majority are from the 1970s. Appendices include answers to problems presented in the text, selected reading, a list of abbreviations and acronyms, and an index of compounds. A 12-page subject index is also included.
In the search for a quantitative correlation between reactivity and electronic configuration of aromatic hydrocarbons, the electron density, at each carbon atom, of the highest occupied π-orbital in the ground state of the molecule is calculated by means of the LCAO method. Comparing the result of such a calculation on fifteen condensed aromatic hydrocarbons with their chemical reactivities, we find that the position at which the electron density is largest is most readily attacked by electrophilic or oxidizing reagents.
It is, therefore, concluded that distinct from other π-electrons the pair of π-electrons occupying the highest orbital, which is referred to as frontier electrons, plays a decisive role in chemical activation of these hydrocarbon molecules. The theoretical significance of this discrimination of the frontier electrons in relation to the chemical activation is discussed.
Hartree‐Fock perturbation theory of magnetic susceptibility and magnetic shielding is developed using a basis set of gauge invariant atomic orbitals. The theory is used to calculate magnetic shielding and spin‐rotation constants associated with the nuclei in LiH and HF giving results in good agreement with experimental values.
The present essay offers an overview of the latest developments in the chemistry of organoboron compounds. The unique structural characteristics and the versatile reactivity profile of organoboron compounds continue to expand their roles in several areas of chemistry. A growing number of boron-mediated reactions have become vital tools for synthetic chemistry, particularly in asymmetric synthesis, metal-catalyzed processes, acid catalysis, and multicomponent reactions. As a result, boronic acids and related molecules have now evolved as major players in synthetic and medicinal chemistry. Moreover, their remnant electrophilic reactivity, even under physiological conditions, has allowed their incorporation in a growing number of bioactive molecules, including bortezomib, a clinically approved anticancer agent. Finally, the sensitive and selective binding of boronic acids to diols and carbohydrates has led to the development of a growing number of novel chemosensors for the detection, quantification, and imaging of glucose and other carbohydrates. There is no doubt that the chemistry of organoboron compounds will continue to expand into new discoveries and new applications in several fields of science.
We present an alternative approach to the derivation of scaled quantum mechanical (SQM) force fields involving the direct scaling of individual primitive valence force constants from a full set of redundant valence coordinates. Our approach is completely general and more flexible than previous SQM schemes. Optimal scaling factors for various primitive stretching, bending, and torsional force constants are derived from a training set of 30 molecules containing C, O, N, H, and Cl and used to scale force constants for a further 30 molecules. Calculated vibrational frequencies are compared with experimental values for over 1500 fundamentals. Using the hybrid three-parameter B3-LYP density functional with the split-valence 6-31G* basis set, our scaling procedure gives an average error of less than 8.5 cm-1 in the scaled frequencies. The average percentage error is under 1%.
Two electron correlation theories, second-order Møller−Plesset perturbation (MP2), and density functional (DFT) methods have been adopted to obtain fully optimized structures of styrene, trans-stilbene, and cis-stilbene. Full geometry optimizations with MP2 shows that the nonplanar conformations of styrene and trans-stilbene are preferred by 0.24 (styrene) and 0.80 kcal/mol (trans-stilbene), respectively. However, B3LYP, BLYP, and BVWN prefer a planar conformation contradicting the MP2 results. Due to the disorder of the crystal, X-ray experimental data of CC double bond length of trans-stilbene seem to be too short. Vibrational spectra of these molecules are calculated at the BLYP/6-31++G** level without any empirical scaling. The agreement with experiment is excellent, some normal modes are reassigned. The dependence of the IR spectrum as a function of conformation in the 700−800 cm-1 region allows the determination of the solution-phase conformation. Both styrene and trans-stilbene are planar in solution, implying that these molecular conformations are mainly determined by the intermolecular forces rather than intramolecular ones.
A number of new aromatic boronic acids have been synthesized for testing in brain tumor therapy. Some observations are reported on difficulties in the determination of melting point and purification and on the influence of the solvent used for recrystallization upon the transition: acid ⇄anhydride. A tentative characterization of the aromatic boronic acids by infrared absorption is proposed. The treatment with n-butyllithium of a brominated boronic acid was found to produce an unusual cleavage of the C-B bond.
A detailed analysis of bonding in systems with chains of condensed molybdenum octahedra is given. A one-dimensional model proves to be applicable over the range of molybdates yet synthesized. The electronic coupling between chains is discussed. Distortions in newly synthesized quaternary systems are seen to result from increased electron count on the molybdenum chains. The band theoretic explanation of these distortions parallels the treatment of second-order Jahn-Teller distortions.
An implementation of the gauge independent atomic orbital (GIAO) method for the ab initio self-consistent-field (SCF) calculation of nuclear magnetic resonance (NMR) chemical shifts is described. Using modern techniques borrowed from analytical derivative methods, we were able to improve the efficiency of the GIAO method significantly. Results with several basis sets, some of them large, are presented for methane, methyl fluoride, cyclopropene, cyclopropane, oxirane, benzene, carbon disulfide, the sulfate and thiosulfate anions, dimethyl sulfide, dimethyl sulfoxide, and dimethyl sulfone. Computer timings for energy and chemical shielding calculations are given for a few large organic molecules. Comparisons are made with the individual gauge for localized orbitals (IGLO) method of Schindler and Kutzelnigg, and with the localized orbital/local origin (LORG) method of Hansen and Bouman. The GIAO method appears to converge faster than the localized techniques; i.e., it provides the same accuracy with a smaller basis, particularly for the individual tensor components. The computational effort for the ab initio calculation of the NMR chemical shifts is only ≃ 2.5 times of the energy calculation.
Crystal structures of 4-chloro- and 4-bromophenylboronic acids (1 and 2) and hydrates of 2 and 4-iodophenylboronic acid in two different forms (2a, 3a, and 3b), which were characterized by single-crystal X-ray diffraction methods, are reported. In structures 1 and 2, −B(OH)2 forms a syn−anti conformation, but it exists in syn−syn as well as anti−anti conformations in the hydrated structures 2a, 3a, and 3b. In all the structures, the molecules are held together by O−H···O interactions formed by −B(OH)2 groups. The C−H···X (X = Cl, Br, and I) interactions play an important role in crystal packing. In 2, Br···Br interactions are also observed. Interestingly, all the three hydrates form similar types of three-dimensional structures with the formation of channels, which are occupied by water molecules. The two hydrates of 4-iodophenylboronic acid (3a and 3b) are distinguishable on the basis of O···O short contacts, with an identical host lattice of the boronic acid.
This work presents the characterization of 2,3-difluorophenylboronic acid (abbreviated as 2,3-DFPBA, C(6)H(3)B(OH)(2)F(2)) by quantum chemical calculations and spectral techniques. The spectroscopic properties were investigated by FT-IR, FT-Raman UV-Vis, (1)H and (13)C nuclear magnetic resonance (NMR) techniques. The FT-IR spectrum (4000-400cm(-1)) and the FT-Raman spectrum (3500-10cm(-1)) in the solid phase were recorded for 2,3-DFPBA. The (1)H and (13)C NMR spectra were recorded in DMSO solution. The UV-Vis absorption spectra of the 2,3-DFPBA that dissolved in water and ethanol were recorded in the range of 200-400nm. There are four possible conformers for this molecule. The computational results diagnose the most stable conformer of the 2,3-DFPBA as the trans-cis form. The structural and spectroscopic data of the molecule were obtained for all four conformers from DFT (B3LYP) with 6-311++G (d,p) basis set calculations. The theoretical wavenumbers were scaled and compared with experimental FT-IR and FT-Raman spectra. The complete assignments were performed on the basis of the experimental results and total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method, interpreted in terms of fundamental modes. We obtained good consistency between experimental and theoretical spectra. (13)C and (1)H NMR chemical shifts of the molecule were calculated by using the gauge-invariant atomic orbital (GIAO) method. The electronic properties, such as excitation energies, absorption wavelengths, HOMO and LUMO energies, were performed by time-dependent DFT (TD-DFT) approach. Finally the calculation results were analyzed to simulate infrared, Raman, NMR and UV spectra of the 2,3-DFPBA which show good agreement with observed spectra.
The molecular structure and properties of phenylboronic acid were investigated experimentally using X-ray structural analysis and spectroscopic methods. Infrared (IR) spectroscopy measurements were performed to assess the hydrogen bonding strength. The experimental part is enhanced by computational results concerning the geometrical and electronic structure. The molecular dimer (basic structural motif) was investigated on the basis of density functional theory (DFT) and Møller–Plesset second order (MP2) perturbation theory. The basis-set superposition error (BSSE) was calculated to correct the binding energy. Atoms in molecules (AIM) and topological analysis of electron localization function (ELF) were applied to study the intermolecular hydrogen bond properties and localization pattern for the neighborhood of the boron atom. The anharmonicity of the hydrogen bond potential function was studied by solving the time-independent Schrödinger equation. Potential energy distribution (PED) analysis of the normal modes was performed to identify the characteristic frequencies of the studied system. Subsequently, the interaction energy for the dimeric form was decomposed using the symmetry-adapted perturbation theory (SAPT) scheme. Car–Parrinello molecular dynamics (CPMD) gave an insight into dynamical processes occurring in the phenylboronic acid dimer in vacuo. The hydrogen bridge protons in the phenylboronic acid are not shifted significantly toward the acceptor. Lower dimerization energy with respect to the carboxylic acid dimers is explained on the basis of the interaction energy decomposition as the effect of diminished induction term. The employment of SAPT and CPMD approaches is a step forward in the understanding of the physico-chemical nature of the large family represented by the investigated compound. Copyright © 2008 John Wiley & Sons, Ltd.
The complexes [Ru(SCN)2(PPh3)2(L)2], where L=py and γ-pic, and [Ru(SCN)2(PPh3)2(L)], where L=py-2-CH2NH2 and py-2-CH2O, have been prepared and studied by IR, NMR, EPR, UV–Vis spectroscopy and X-ray crystallography. The complexes were prepared in the reactions of [RuCl2(PPh3)3] with pyridine, γ-picoline, 2-(aminomethyl)pyridine and 2-(hydroxymethyl)pyridine in methanol solutions. The electronic structures of the obtained compounds have been calculated using the DFT/TD-DFT method.
The experimental and theoretical vibrational spectra of 4-chloro- and 4-bromophenylboronic acids (abbreviated as 4Clpba and 4Brpba) were studied. The Fourier transform Raman and Fourier transform infrared (FTIR) spectra of 4Clpba and 4Brpba molecules were recorded in the solid phase. The structural and spectroscopic analyses of the molecules were made by using Hartree–Fock and density functional harmonic calculations. In both 4Clpba and 4Brpba only one form was most stable using B3LYP level with the 6–311 + + G(d,p) basis set. Selected experimental bands were assigned and characterized on the basis of the scaled theoretical wavenumbers by their total energy distribution (TED). Finally, geometric parameters as well as infrared (IR) and Raman bands were compared with the experimental data of the molecules. Copyright © 2008 John Wiley & Sons, Ltd.
The experimental and theoretical study on the structures and vibrations of 5-fluoro-salicylic acid and 5-chloro-salicylic acid (5- FSA and 5-ClSA, C 7H 5FO 3 and C 7H 5C lO 3) is presented. The Fourier transform infrared spectra (4000-400 cm -1) and the Fourier transform Raman spectra (4000-50 cm -1) of the title molecules in the solid phase were recorded. The molecular structures, vibrational wave numbers, infrared intensities, Raman intensities and Raman scattering activities were calculated for a pair of molecules linked by the intermolecularO-H· · ·O hydrogen bond. The geometrical parameters and energies of 5-FSA and 5ClSA were obtained for all eight conformers/isomers from density functional theory (DFT) (B3LYP) with 6-311++G(d,p) basis set calculations. The computational results identified the most stable conformer of 5-FSA and 5-ClSA as the C1 form. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. The spectroscopic and theoretical results were compared with the corresponding properties for 5-FSA and 5-ClSAmonomers and dimer of C1 conformer. The optimized bond lengths, bond angles and calculated wave numbers showed the best agreement with the experimental results.