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Dege, Necmi/0000-0003-0660-4721 WOS: 000471778600014 New organic compound of (Z) -N'- (2, 4-dinitrobenzylidene) -2- (quinolin-8-yloxy) acetohydrazide (DBQA) was synthesized for the first time and its structural characterization was performed by single crystal X-ray diffraction method. The compound crystallizes in the triclinic system with space group P-1. The spectroscopic characterization was also performed by the applying of FT-IR, UV-Vis, H-1 and C-13 NMR spectroscopies. In order to support experimental results, density functional theory (DFT) calculations have been performed using B3LYP functionnal with 6-311++G(d, p) basis set. All of the obtained theoretical results are in a perfect agreement with the experimental ones. Furthermore, nonlinear optical (NLO) behavior of DBQA has been investigated by determining of electric dipole moment (mu), polarizability (alpha) and hyperpolarizability (beta) using the same basis set. Finally, the molecular electrostatic potential (MEP) surface of DBQA molecule was simulated and discussed. (C) 2019 Elsevier B.V. All rights reserved.

The N-(Phenylsulfonyl)-L-asparagine (NPLAS), which is a potential nonlinear optical material, was synthesized and its geometric structure was optimized to obtain its geometric parameters, vibration frequencies and electronic structures at Hartree-Fock (HF) and B3LYP level of density functional theory (DFT) with 6-311 + +G(d,p) basis set, using Gaussian 09W program. The H-1 and C-13 nuclear magnetic resonance (NMR) chemical shifts of the title molecule were calculated by using the gauge independent atomic orbital (GIAO), continuous set of gauge transformations (CSGT) and individual gauges for atoms in molecules (IGAIM) methods and were also compared with experimental values. The electronic properties HOMO and LUMO energies were calculated and analyzed. Potential energy surface scan, natural population analysis (NPA) and Mulliken's atomic charges were also investigated using DFT and HF models. A detailed molecular picture and intermolecular interactions arising from hyperconjugative interactions and charge delocalization of the molecule were analyzed using natural bond orbital (NBO) analysis. (C) 2016 Elsevier GmbH. All rights reserved.

Density functional theory calculations on ground state molecular geometry, stable conformers, and vibrational wavenumbers for 1-[(E)-{[4-(morpholin-4-yl)phenyl]imino}methyl]naphthalen-2-ol (MPIMN) molecule were performed by using B3LYP and B3PW91 functionals for the exchange-correlation energy with the 6-311++G(d,p) basis set. The detailed assignments of vibrational wavenumbers were carried out on the basis of potential energy distribution (PED) analysis. Nonlinear optical (NLO) behavior of MPIMN was investigated by the determining of electric dipole moment (mu), polarizability (alpha), and first hyperpolarizability (beta) by using B3LYP and B3PW91 functionals. Stability of the molecule arising from hyperconjugative interactions and charge delocalization was analyzed using natural bond orbital (NBO) analysis. The frontier molecular orbitals (HOMO and LUMO) were simulated, and the obtained relatively small energy gap confirmed that charge transfer occurs within MPIMN. Finally, molecular electrostatic potential (MEP) surface was simulated to demonstrate reactive sites for the title molecule.

Quantum mechanical calculations of ground state energy, vibration wavenumbers, and electronic absorption wavelengths of N '-[(Z)-(4-methylphenyl)methylidene]-4-nitrobenzohydrazide with C15H13N3O3 empirical formula was performed by using Gaussian 09 program. Becke's three-parameter exchange functional in conjunction with the Lee-Yang-Parr correlation functional and Heyd-Scuseria-Ernzerhof functional levels of density functional theory (DFT) with the 6-311++G(d,p) basis set were used in the performing of above mentioned calculations. The highest occupied and lowest unoccupied molecular orbital (HOMO and LUMO) energies have been also calculated at the same levels. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. Nonlinear optical (NLO) behavior of the title molecule has been examined by the determining of electric dipole moment (mu), polarizability (alpha), and static first-order hyperpolarizability (beta). Finally, molecular electrostatic potential (MEP) surface as well as Mulliken and NBO atomic charges were calculated by using Gaussian 09 program.

In this study, quantum chemical calculations of vibrational spectra, Raman spectra, electronic properties (total energy, dipole moment, electronegativity, chemical hardness and softness), Mulliken atomic charges and thermodynamic parameters of bis-thiourea zinc acetate (BTZA) have been performed using Gaussian 09 program. Additionally, nonlinear optical (NLO), conformational, natural bond orbital (NBO) analyses of BTZA have been carried out using the same program. The structural and spectroscopic data of the molecule in the ground state have been calculated using Hartree-Fock (HF) and density functional method (DFT/B3LYP) with the 6-311++G(d,p) basis set. In addition, the molecular frontier orbital energies (HOMO, HOMO-1, LUMO and LUMO+1) of the title compound have been calculated at the HF and B3LYP levels. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Finally, the calculated results were applied to simulate infrared and Raman spectra of the title compound which showed good agreement with the experimental ones.

Quantum chemical calculations of the ground state energy, the highest and lowest energy conformers and vibrational wavenumbers of 3-(2,3-dimethoxyphenyl)-1-(pyridin-2-yl)prop-2-en-1-one have been performed by using Gaussian 09 program. B3LYP and HSEH1PBE levels of density functional theory with the 6-311++G(d,p) basis set have been used to perform above-mentioned calculations. The vibrational wavenumbers have been assigned on the basis of potential energy distribution analysis. Stability of the molecule arising from hyper-conjugative interactions and charge delocalization has been analyzed using natural bond orbital analysis. The frontier molecular orbitals have been simulated, and obtained small energy gap between the highest occupied molecular orbital and lowest unoccupied molecular orbital energies has confirmed that charge transfer occurs within title compound. Nonlinear optical behavior of the title compound has been investigated by determining electric dipole moment, polarizability and hyperpolarizability. Finally, the molecular electrostatic potential surface and density of state have been simulated to find more reactive sites for electrophilic and nucleophilic attack.

WOS: 000280028600036 The molecular geometry, vibrational frequencies, gauge-including atomic orbital (GIAO) H-1 and C-13 chemical shift values of 3,5-bis-(4-methylbenzoyl)-2,6-bis(4-methylphenyl)-4H-pyran-4-one in the ground state have been calculated by using the Hartree-Fock (HF) and density functional method (DFT/B3LYP) with 6-31G(d) basis set. And this structure has been confirmed by IR, C-13 and H-1 spectroscopy. The results of the optimized molecular structure are presented and compared with the experimental X-ray diffraction. The computed vibrational frequencies are used to determine the types of molecular motions associated with each of the experimental bands observed. Also, calculated C-13 and H-1 chemical shift values are compared with the experimental ones. The data of the title compound display significant molecular structure. Moreover, its IR and NMR spectroscopic analysis provide the basis for future design of efficient materials having the pyran core. (C) 2010 Elsevier B.V. All rights reserved. Sapanca MunicipalityBelediyeler Authors would like to thank to Ibrahim USLU, mayor of Sapanca Municipality, for financial support.

WOS: 000265516400037 PubMed: 19264542 The molecular geometry, vibrational frequencies, gauge including atomic orbital (GIAO) H-1 and C-13 chemical shift values and several thermodynamic parameters of 3-(2-Hydroxyphenyl)-4-phenyl-1H-1,2,4-triazole-5-(4H)-thione in the ground state have been calculated by using the Hartree-Fock (HF) and density functional methods (BLYP and B3LYP) with 6-31G(d) basis set. The results of the optimized molecular structure are presented and compared with the experimental X-ray diffraction. The molecule contains one O-H center dot center dot center dot N and one C-H center dot center dot center dot pi (phenyl) intramolecular interactions. The computed vibrational frequencies are used to determine the types of molecular motions associated with each of the experimental bands observed. Data of the title compound display significant structure-correlation and provide the basis for future design of efficient materials having the derivatives of 1,2,4-triazole. Also, calculated I H chemical shift values compared with the experimental ones. (C) 2009 Elsevier B.V. All rights reserved. Sakarya UniversitySakarya University [RN: 2007 02 02 001 - BAP] We would like to thank Sakarya University for financial support (RN: 2007 02 02 001 - BAP).

In this study, the direct molecular structure implementations for calculating vibrational spectra and scaling factors, and infrared intensities at both the Hartree-Fock (HF) and density functional (B3LYP) levels of theory with 6-31G(d), 6-311G(d), 6-31++G(d,p), and 6-311++G(d,p) basis sets are presented. Also, vibrational frequencies have been investigated as dependence on the choice of method and basis set. The parameters of molecular geometry and vibrational frequencies values of 2-aryl-1,3,4-oxadiazoles 5a-g in the ground state have been calculated. Theoretical determination of vibrational frequencies is quite useful both in understanding the relationship between the molecular structures and scaling factor. The data of 2-aryl-1,3,4-oxadiazoles 5a-g display significant electronic properties provide the basis for future design of efficient materials having the oxadiazole core and theoretical IR Studies. (C) 2008 Wiley Periodicals, Inc. Int J Quantum Chem 109: 328-341, 2009

The molecular geometry, the normal mode frequencies and corresponding vibrational assignment of melaminium phthalate (C3H7N6+center dot C8H5O4-) in the ground state were performed by HF and B3LYP levels of theory using the 6-31G(d) basis set. The optimized bond length numbers with bond angles are in good agreement with the X-ray data. The vibrational spectra of melaminium phthalate which is calculated by HF and B3LYP methods, reproduces vibrational wave numbers with an accuracy which allows reliable vibrational assignments. The title compound has been studied in the 4000-100 cm(-1) region where the theoretical evaluation and assignment of all observed bands were made. (C) 2007 Elsevier B.V. All rights reserved.

The molecular geometry, vibrational frequencies, infrared intensities, Raman scattering activities and several thermodynamic parameters of anilinium nitrate in the ground state have been calculated by both Hartree-Fock (HF) and three density functional theory (DFT) methods (B3LYP, BLYP and B3PW91) using the 6-31G(d) basis set. The results of the optimized molecular structure are presented and compared with the experimental X-ray structure. The optimized geometric bond lengths are described very well by the HF method while bond angles are reproduced more accurately by the DFT methods. Comparison between the observed fundamental vibrational frequencies of anilinium nitrate and the results of DFT and HF methods indicates that B3LYP is superior to the scaled HF, BLYP and B3PW91 approaches for molecular vibrational problems. The computed vibrational frequencies are used to determine the types of molecular motions associated with each of the experimental bands observed. In addition, calculated results are related to the linear correlation plot of computed data versus experimental geometric parameters and IR data.

Vibrational frequencies and gauge including atomic orbital (GIAO) C-13 NMR and H-1 NMR chemical shift values of 2,6 distyrylpyridine (C21H17N) in the ground state have been calculated by using the Hartree-Fock (HF) and density functional method (B3LYP) with 6-31G(d) basis set. These methods are proposed as a tool to be applied in the structural characterization of 2,6 distyrylpyfidine (C21H17N). The title compound has C-2 nu point group, thus providing useful support in the interpretation of experimental IR data. In addition, obtained results were related to the linear correlation plot of experimental C-13 NMR, H-1 NMR chemical shifts values and IR data. (C) 2007 Elsevier B.V. All rights reserved.

The molecular hyperpolarizability of some donor-acceptor oxadiazoles was investigated using ab initio methods. Ab initio optimizations were performed at the Hartree-Fock level using different basis sets, starting with the minimal basis set, and then split valence sets. The first hyperpolarizabilities were calculated at the Hartree-Fock level employing the corresponding basis sets using Gaussian 98W. In general, the first hyperpolarizability is dependent on the choice of method and basis set. In order to understand this phenomenon in the context of molecular orbital picture, we examined the molecular HOMOs and molecular LUMOs generated via HF/6-31G level. It has also been calculated the polarizability, anisotropy of polarizability and ground state dipole moment of all the molecules. Several of these oxadiazoles display significant second-order molecular nonlinearity, beta(8.57-195.05 x 10(-30) esu) and provide the basis for future design of efficient nonlinear optical materials having the oxadiazole core.

The molecular geometry and vibrational frequencies of N-phenyl-AP-(2-thienyimethylene)hydrazine (C11H10N2S) have been calculated using Hartree-Fock and density functional method (B3LYP) with 6-31G(d) basis set. The optimized geometric bond lengths and angles obtained using HF and DFr (B3LYP) are in agreement with the experimental data. B3LYP method seems to be appropriate than HF method for the calculation of vibrational frequencies and geometrical parameters of the (C11H10N2S) compound. (c) 2006 Elsevier B.V. All rights reserved.

The vibrational frequencies and molecular geometry of (R)- and (rac)-4-phenly-1,3-oxazolidin-2-one (4-POO) in the ground state have been calculated using the Hartree-Fock and density functional method (B3LYP) with 6-31G(d) basis set. The optimized geometric bond lengths are described better by HF while bond angles are reproduced more accurately by DFT (B3LYP). Comparison of the observed fundamental vibrational frequencies of (R)-POO and (rac)-4-POO and calculated results by density functional B3LYP and Hartree-Fock methods indicate that B3LYP is superior to the scaled Hartree-Fock approach for molecular vibrational problems. (c) 2005 Elsevier B.V. All rights reserved.

The molecular geometry and vibrational frequencies of glutaonic acid (C5O4H6) in the ground state has been calculated using the Hartree-Fock (HF) and density functional method (B3LYP) with 6-31G(d) basis set. The optimized geometric bond lengths and bond angles obtained by using HF and DFT (B3LYP) show the best agreement with the experimental data. Comparison of the observed fundamental vibrational frequencies of glutaconic acid and calculated results by density functional B3LYP and Hartree-Fock methods indicate that B3LYP is superior to the scaled Hartree-Fock approach for molecular vibrational problems. (c) 2005 Elsevier B.V. All rights reserved.

The molecular geometry and vibrational frequencies of the [2-Oxo-2-(4-acetyl) phenyl amino] ethylene methacrylate (APEMA) were examined theoretically using the Hartree-Fock and Density function method (B3LYP) with 6-31G(d) basis set. The calculated geometrical parameters of the investigated molecule were compared with experimental data. Both the calculated structural parameters and vibrational frequencies are in good agreement with the available experimental data.

WOS: 000331341100005, PubMed ID: 24220668, A novel NHC complex of silver(I) ion, 1-pentamethylbenzyl-3-(n)buthylbenzimidazolesilver(I)bromide, was prepared and fully characterized by single crystal X-ray structure determination. FT-IR, NMR and UV-vis spectroscopies were employed to investigate the electronic transition behaviors of the complex. Additionally, the molecular geometry, vibrational frequencies, gauge including atomic orbital (GIAO) H-1 and C-13 chemical shift and electronic transition values of silver(I) complex were calculated by using density functional theory levels (B3LYP and PBE1PBE) with LANL2DZ basis set. Also, the vibrational frequencies were supported on the basis of the potential energy distribution (PED) analysis calculated for PBE1PBE level. We were also investigated total static dipole moment (mu), the mean polarizability (), the anisotropy of the polarizability (Delta alpha), the mean first-order hyperpolarizability () of the title complex. Natural bond orbital (NBO) analysis was performed to determine the presence of hyperconjugative interactions, and charge distributions

The molecular geometry, vibrational frequencies, gauge including atomic orbital (GIAO) H-1 and C-13 chemical shift values of ABZ-TNB [ABZ-TNB: 2-aminobenzimidazole-trinitrobenzene] and ABZ-PA [ABZ-PA: 2-aminobenzimidazole-picric acid] in the ground state were calculated by using density functionals (B3LYP and PBE1PBE) and Hartree-Fock (HF) methods with the 6-31 ++ G(d,p) basis set. Furthermore, the electronic spectrum of title complexes was calculated with the time dependent DFT levels (TD-PBE1PBE and TD-B3LYP) and HF (TD-HF) method starting from the ground state geometry optimized in the gas phase. A detailed assignment of vibrational spectra was made on the basis of the calculated potential energy distribution (PED). Total static dipole moment (mu), the mean polarizability (aOE (c) I +/- aOE(a)), the anisotropy of the polarizability (Delta alpha), the mean first-order hyperpolarizability (aOE (c) I(2)aOE(a)), highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies, chemical hardness (eta) and electronegativity (chi) of ABZ-TNB and ABZ-PA complexes were also investigated with quantum chemical calculations. Additionally, data obtained from quantum chemical calculations were compared with the experimental ones.

In this paper, quantum chemistry calculations of geometric parameters, harmonic vibrational wavenumbers, molecular frontier orbital energies (HOMO and LUMO) and the electronic properties of bis(8-oxy-1-methylquinolinium) hydroiodide ([(C10H9NO)(2)H+]center dot 1(-)) have been performed by using Gaussian 09 program. The structural and spectroscopic data of the molecule in the ground state have been calculated by using Hartree-Fock (HF) and density functional method (DFT/B3LYP) with the LanL2DZ basis set. For the spectra predicted, a potential energy distribution (PED) is calculated. The H-1 and C-13 nuclear magnetic resonance (NMR) chemical shifts values of bis(8-oxy-1-methylquinolinium) hydroiodide molecule have been calculated by the gage including atomic orbital (GIAO) method. Furthermore, molecular electrostatic potential maps (MEP), Mulliken charges and the natural bonding orbital (NBO) analysis of the compound have been calculated by the HF and B3LYP/Lanl2DZ methods. (C) 2012 Elsevier B.V. All rights reserved.

WOS: 000294498400010 The molecular geometry, vibrational frequencies, gauge including atomic orbital (GIAO) H-1 and C-13 chemical shift values and several thermodynamic parameters of 4-allyl-2-(morpholin-4-ylmethyl)-5-(pyridin-4-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione in the ground state were calculated using density functional methods (BLYP and B3LYP) with the 6-31G(d) basis set. The results of the optimized molecular structure are given and compared with experimentally obtained X-ray diffraction. The computed vibrational frequencies were used to determine the types of molecular motions associated with each of the experimental bands observed. Vibrational mode assignments of the title compound were carried out using a total energy distribution calculation. The calculated H-1 and C-13 chemical shift values are compared with the experimental values. The molecular frontier orbital energies of the title compound were calculated using the BLYP and B3LYP/6-31G( d) levels. The obtained data for the title compound provided its molecular structure, while the IR and NMR analyses provide a basis for the future design of efficient materials containing a 1,2,4-triazole core. Sakarya UniversitySakarya University [P.N: 2007.02.02.001-BAP] We would like to thank Sakarya University for financial support (P.N: 2007.02.02.001-BAP) and Massimo Malagoli for his assistance with the TED calculations.

WOS: 000293363000086 PubMed: 21658992 Quantum chemical calculations of geometrical structure and vibrational wavenumbers of 8-hydroxyquinolinium picrate (8-HQP) were carried out by ab initio HF and density functional (DFT/B3LYP) method with 6-31++G(dp) basis set. The calculated geometric parameters of 8-HQP are presented. A detailed interpretation of the infrared spectra of 8-hydroxyquinolinium picrate (8-HQP) are also reported. Theoretical molecular frontier orbital energies of the title compound have been calculated using the method mentioned above in order to understand this phenomenon in the context of molecular orbital picture. The molecular HOMOs and LUMOs generated via HF and B3LYP method have been outlined. (C) 2011 Elsevier B.V. All rights reserved. Sapanca MunicipalityBelediyeler Authors would like to thank to Ibrahim USLU, major of Sapanca Municipality, for financial support.

The calculation of molecular hyperpolarizability, molecular frontier orbital energies of some donor-acceptor oxadiazoles (5a-f, 8a-f, and 9a-f) have been investigated using ab initio methods and different basis sets. Ab initio optimizations were performed at the Hartree-Fock (HF) and density functional (Beckee-3-Lee-Yang-Parr; B3LYP) levels of theory with 6-31G basis set. The polarizability (), anisotropy of polarizability (Delta alpha), and ground-state dipole moment (mu), first hyperpolarizability (beta), and molecular frontier orbital (HOMO, highest occupied molecular orbital and LUMO, lowest unoccupied molecular orbital) energies of 5a-f, 8a-f, and 9a-f have been calculated at the HF and B3LYP methods with 6-31G, 6-31G(d), 6-31+G(d), 631++G(d,p), 6-311G, 6-311G(d), 6-311+G(d), and 6-311++G(d,p) basis sets. Also, the molecular hardness (eta) and electronegativity (chi) parameters have been obtained using molecular frontier orbital energies. The , Delta alpha, mu, beta, HOMO, LUMO energies, eta and chi parameters have been investigated as dependence on the choice of method and basis set. The variation graphics of , Delta alpha, mu, beta, eta, and chi parameters using HF and B3LYP methods with different basis sets are presented. We have examined the frontier molecular orbital pictures of 5a-f, 8a-f, and 9a-f using B3LYP/6-31++G(d,p) level. The 5a-f, 8a-f, and 9a-f display significant linear, second-order molecular nonlinearity, and molecular parameters and provide the basis for future design of efficient nonlinear optical materials having the 1,3,4-oxadiazole core. (C) 2009 Wiley Periodicals, Inc. Int J Quantum Chem 111: 130-147, 2011 https://doi.org/10.1002/qua.22416

The molecular geometry and vibrational frequencies of melaminium acetate acetic acid solvate monohydrate in the ground state have been calculated by using the Hartree-Fock (HF) and density functional method (B3LYP) with 6-31++G(d,p) basis set. The results of the optimized molecular structure are presented and compared with the experimental X-ray diffraction. The molecule contains the weak hydrogen bonds of N-H ... O and O-H ... O types, and those bonds are calculated with HF and DFT method. The computed vibrational frequencies were used to determine the types of molecular motions associated with each of the experimental bands observed. In addition, calculated results are related to the linear correlation plot of computed data versus experimental geometric parameters and IR data. (C) 2010 Elsevier B.V. All rights reserved.

The molecular geometry, vibrational frequencies, gauge-including atomic orbital (CIAO) H-1 and C-13 chemical shift values of 4-cyanobenzaldehyde isonicotinoyl-hydrazone monohydrate in the ground state have been calculated by using the Hartree-Fock (HF) and density functional method (DFT/B3LYP) with 6-31++G(d,p) basis set. Furthermore, this structure has been confirmed by IR, C-13 and H-1 spectroscopy. The results of the optimized molecular structure are presented and compared with the experimental X-ray diffraction. The computed vibration frequencies are used to determine the types of molecular motions associated with each of the experimental bands observed. C-13 and H-1 NMR data were calculated by means of the methods of GIAO, CSGT, and IGAIM. Calculated chemical shift values are compared with the experimental 4-cyanobenzaldehyde isonicotinoyl-hydrazone monohydrate. (C) 2010 Elsevier B.V. All rights reserved.

The direct molecular structure implementations of the gage-including atomic orbital (GIAO), individual gages for atoms in molecules (IGAIM) and continuous set of gage transformations (CSGT) methods for calculating nuclear magnetic shielding tensors at both the Hartree-Fock (HF) and density functional (B3LYP) levels of theory with 6-31G(d), 6-311G(d), 6-31++G(d,p), 6-311++G(d,p), and 6-311++G(df,pd) basis sets are presented. Dependence on the H-1 and C-13 NMR chemical shifts on the choice of method and basis set have been investigated. Also, these chemical shifts of 2-aryl-1,3,4-oxadiazoles 5a-g have been performed related to dihedral angles (C4-C3-C2-O) of two conformers. The optimized molecular geometries and H-1 and C-13 chemical shift values of 2-aryl-1,3,4-oxadiazoles 5a-g in the ground state have been obtained. The linear correlation coefficients of C-13 NMR chemical shifts for these molecules were given. The new nuclear magnetic shielding tensors of tetramethylsilane (TMS) were calculated. The data of 2-aryl-1,3,4-oxadiazole derivatives display significant molecular structure and NMR analysis. Also, these provide the basis for future design of efficient materials having the 1,3,4-oxadiazole core.

The H-1 and C-13 NMR chemical shifts of the 2,4-difluorobenzaldehyde isonicotinoylhydrazone (I) and 2,3-dichlorobenzaidehyde isonicotinoylhydrazone (II) were determined with the help of full spectral analysis. The geometry and electronic structure of the title compounds were investigated at both the ab initio Hartree-Fock and the B3LYP levels with 6-31+G(d,p) basis set. The NMR data were calculated by means of the CIAO, CSGT, and IGAIM methods. All quantum-chemical calculations, including those of NMR data, were performed by ab initio level HF and DFT methods. Excellent agreement between the theoretical and experimental results was found for the HF level H-1 and C-13 chemical shifts. The parameters of molecular geometry and H-1 and C-13 chemical shift values of the title compounds (I, II) in the ground state have been calculated and and compared with corresponding experimental result. (C) 2009 Wiley Periodicals, Inc, Concepts Magn Reson Part A 34A: 297-304, 2009.

Theoretical calculations were performed using density functional theory for studying the molecular structure and vibrational spectra of the asymmetric squaraine [(2-dimethylamino-4-anilino) squaraine] (ADTCH3) in the ground state. The influence of intermolecular interactions effects on molecular properties have been considered by calculation performed on (ADTCH3) dimer. The optimized geometric bond lengths and bond angles obtained by using B3LYP/6-31G(d) show a good agreement with the experimental data. As compared to theoretical frequencies of the monomer, the calculated values obtained for (ADTCH3) dimer are in much better agreement with the experiment. All the experimental vibrational bands have been discussed and assigned to normal modes on the basis of our calculations. With respect to the study of Silva et al., some modes have been reassigned in the light of present theoretical results. In virtue of time dependent density functional theories (TD-DFT), the low-lying excited states of (ADTCH3) are determined using 6-31G(d) basis set. The calculations show that using TD-B3LYP/6-31G(d) approach, experimental absorption spectrum has been well reproduced. It has been concluded that the lowest singlet excited state (S1) of the title compound is mainly derived from the (HOMO → LUMO) (π → π∗) electron transition located on oxocarbon ring.

The molecular geometry and vibrational frequencies of melaminium citrate in the ground state have been calculated using the Hartree-Fock (HF) and density functional method (B3LYP) with 6-31G(d) basis set. The optimized geometric bond lengths and bond angles obtained by using HF and density functional theory (DFT, B3LYP) show the best agreement with the experimental data. Comparison of the observed fundamental vibrational frequencies of melaminium citrate and calculated results by density functional B3LYP and Hartree-Fock methods indicate that B3LYP is superior to the scaled Hartree-Fock approach for molecular vibrational problems. (C) 2006 Elsevier B.V. All rights reserved.

The molecular geometry and vibrational frequencies of 2-amino-5-phenyl-1,3,4-thiadiazole (C8H7N3S) in the ground state has been calculated using the Hartree-Fock and density functional method (B3LYP) with 6-31G(d) basis set. The optimized geometric bond lengths and bond angles obtained by using HF and DFT (B3LYP) show the best agreement with the experimental data. Comparison of the observed fundamental vibrational frequencies of 2-amino-5-phenyl-1,3,4-thiadiazole (C8H7N3S) and calculated results by density functional B3LYP and Hartree-Fock methods indicate that B3LYP is superior to the scaled Hartree-Fock approach for molecular vibrational problems. (c) 2005 Elsevier B.V. All rights reserved.

The molecular structure and vibrational spectra of 1-amino-5-benzoyl-4-phenylpyrimidin-2(1H) (C17H13N3O2) have been investigated by Hartree-Fock and density functional method using standard B3LYP with 6-31G(d) basis set. The calculated results of the geometric bond lengths and bond angles obtained by using HF and DFT (B3LYP) are in very good agreement with the experimental values. Comparison of the observed fundamental vibrational frequencies of 1-amino-5-benzoyl-4-phenylpyrimidin-2(1H) (C17H13N3O2) and calculated results by density functional B3LYP and Hartree-Fock methods indicate that B3LYP is superior to the scaled Hartree-Fock approach for molecular vibrational problems. (c) 2006 Elsevier B.V.. All rights reserved.

The molecular geometry and vibrational frequencies of 1-(thiophen-2-yl-methyl)-2-(thiophen-2-yl)-1H-benzimidazole (C16H12N2S2) in the ground state has been calculated using the Hartree-Fock (HF) and density functional method (B3LYP) with 6-31G(d) basis set. The optimized geometric bond lengths and bond angles obtained by using HF and DFT (B3LYP) show the best agreement with the experimental data. Comparison of the observed fundamental vibrational frequencies of 1-(thiophen-2-yl-methyl)-2-(thiophen-2-yl)-1H-benzimidazole (C16H12N2S2) and calculated results by density functional B3LYP and Hartree-Fock methods indicate that B3LYP is superior to the scaled Hartree-Fock approach for molecular vibrational problems. (C) 2006 Elsevier B.V. All rights reserved.

The molecular geometry-and vibrational frequencies of melamine diborate in the ground state have been calculated using the Hartree-Fock and density functional methods (B3LYP) with 6-31G(d) basis set. The optimized geometric band lengths and bond angles obtained by using HF and DFT (B3LYP) show the best agreement with the experimental data. Comparison of the observed fundamental vibrational frequencies of melamine diborate with calculated results by density functional B3LYP and Hatree-Fock methods indicates that B3LYP is superior to the scaled Hatree-Fock approach for molecular vibrational problems. (C) 2004 Elsevier B.V. All rights reserved.

The molecular geometry and vibrational frequencies of the title (C10H8N4S4) compound in the ground state have been calculated using the Hartree-Fock (HF) and density functional method (B3LYP) with 6-31 G(d) basis set. Comparison of the observed fundamental vibrational frequencies of the title compound and calculated results by density functional B3LYP and HF methods indicate that B3LYP is superior to the scaled HF approach for molecular vibrational problems. (c) 2006 Elsevier B.V. All rights reserved.

The molecular geometry optimization, vibrational frequencies and gauge including atomic orbital (GIAO) 1H and 13C chemical shift values of thiazolylazopyrimidine chromophores have been investigated by using density functional theories (DFT/B3LYP, PBE1PBE and BHand-HLYP) and Hartree–Fock (HF) methods with 6–31++G(d,p) basis set. The computed IR and NMR spectra are used to determine the types of the experimental bands observed. Also, the vibrational frequencies are supported on the basis of the potential energy distribution (PED) analysis calculated by using PBE1PBE method. The UV-vis spectrum has been obtained by TD-DFT and TD-HF methods. Total static dipole moment (μ), the mean polarizability (〈α〉), the anisotropy of the polarizability (Δα), the mean first-order hyperpolarizability (〈β〉), highest occupied molecular orbital (HOMO), and lowest occupied molecular orbital (LUMO) energies of thiazolylazopyrimidine chromophores also have been investigated with quantum chemical calculations. Obtained nonlinear optical (NLO) parameters are compared with experimental ones. Additionally, the molecular hardness (η) and electronegativity (χ) parameters have been obtained by using the frontier molecular orbital energies. Obtained data from thiazolylazopyrimidine chromophores are important for associating the experimental and theoretical spectra with molecular structure and their properties.