Muharrem Dinçer

Experimental and ab initio computational studies on 4-(1H-benzo[d]imidazol-2-yl)-N,N-dimethylaniline

The title molecule, 4-(1H-benzo[d]imidazol-2-yl)-N,N-dimethylaniline (C15H15N3), was prepared and characterised by 1H-NMR, 13C-NMR, IR and single-crystal X-ray diffraction. The molecular geometry, vibrational frequencies and gauge including atomic orbital (GIAO) 1H- and 13C-NMR chemical shift values of the title compound in the ground state have been calculated using the Hartree–Fock (HF) and density functional theory (DFT) methods with 6–31G(d) basis sets, and compared with the experimental data. The calculated results show that the optimised geometries can well reproduce the crystal structural parameters and the theoretical vibrational frequencies, and 1H- and 13C-NMR chemical shift values show good agreement with experimental data. To determine conformational flexibility, the molecular energy profile of the title compound was obtained by semi-empirical (AM1) calculations with respect to the selected torsion angle, which was varied from −180° to +180° in steps of 5°. The energetic behaviour of the title compound in solvent media was examined using the B3LYP method with the 6–31G(d) basis set by applying the Onsager and the Polarizable Continuum Model (PCM). In addition, the molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis and thermodynamic properties of the title compound were investigated using theoretical calculations.

Molecular structure and vibrational bands and chemical shift assignments of 4-allyl-5-(2-hydroxyphenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione by DFT and ab initio HF calculations

The title molecule, 4-allyl-5-(2-hydroxyphenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (C(11)H(11)N(3)OS), was synthesized and characterized by IR-NMR spectroscopy and single-crystal X-ray diffraction. The compound crystallizes in the monoclinic space group is P2(1)/c, a=9.0907(5)A, b=9.1288(7)A, c=13.6222(7)A, alpha=90 degrees , beta=98.442 (4), gamma=90 degrees and V=2683.7(6)A(3), F(000)=488, D(x)=1.386 g/cm(3). In addition to the molecular geometry from X-ray experiment, the molecular geometry, vibrational frequencies, gauge including atomic orbital (GIAO) (1)H and (13)C chemical shift values of the title compound in the ground state have been calculated using the Hartree-Fock (HF) and density functional method (DFT/BLYP and DFT/B3LYP) with 6-31G(d) basis set. To determine conformational flexibility, molecular energy profile of the title compound was obtained by HF/6-31G(d) calculations with respect to selected degree of torsional freedom, which was varied from -180 degrees to +180 degrees in steps of 10 degrees . Besides, molecular electrostatic potential (MEP), frontier molecular orbitals (FMO), and several thermodynamic properties were performed by the HF and DFT methods.

Molecular structure and vibrational and chemical shift assignments of 3-(2-hydroxyphenyl)-4-phenyl-1H-1,2,4-triazole-5-(4H)-thione by DFT and ab initio HF calculations.

The molecular geometry, vibrational frequencies, gauge including atomic orbital (GIAO) 1H and 13C 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...N and one C-H...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 1H chemical shift values compared with the experimental ones.

Molecular structure and vibrational and chemical shift assignments of 5-(2-Hydroxyphenyl)-4-(p-tolyl)-2,4-dihydro-1,2,4-triazole-3-thione by DFT and ab initio HF calculations

The molecular geometry, vibrational frequencies, gauge including atomic orbital (GIAO) 1H and 13C chemical shift values and several thermodynamic parameters of 5-(2-Hydroxyphenyl)-4-(p-tolyl)-2,4-dihydro-1,2,4-triazole-3-thione in the ground state have been calculated by using the Hartree-Fock (HF) and density functional method (DFT/B3LYP) with 6–31G(d), 6–31 + G(d,p) and LANL2DZ basis sets. 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 1H chemical shift values compared with the experimental ones. The data of the title compound display significant molecular structure and IR, NMR analysis provide the basis for future design of efficient materials having the of 1,2,4-triazole core.

Experimental and molecular modeling investigation of (E)-N-{2-[(2-hydroxybenzylidene)amino]phenyl}benzenesulfonamide

The Schiff base compound (E)-N-{2-[(2-hydroxybenzylidene)amino]phenyl}benzenesulfonamide has been synthesized and characterized by IR, NMR and Uv-vis spectroscopies, and single-crystal X-ray diffraction technique. In addition, quantum chemical calculations employing density functional theory (DFT) method with the 6–311++G(d,p) basis set were performed to study the molecular, spectroscopic and some electronic structure properties of the title compound, and the results were compared with the experimental findings. There exists a good correlation between experimental and theoretical data. Enol-imine/keto-amine tautomerization mechanism was investigated in the gas phase and in solution phase using the polarizable continuum model (PCM) approximation. The energetic and thermodynamic parameters of the enol-imine → keto-amine transfer process show that the single proton exchange is thermodynamically unfavored both in the gas phase and in solution phase. However, the reverse reaction seems to be feasible with a low barrier height and is supported by negative values in enthalpy and free energy changes both in the gas phase and in solution phase. The solvent effect is found to be sizable with increasing polarity of the solvents for the reverse reaction. The predicted nonlinear optical properties of the compound are found to be much greater than those of urea.

Experimental and theoretical investigation of the molecular and electronic structure of 5-(4-aminophenyl)-4-(3-methyl-3-phenylcyclobutyl)thiazol-2-amine

The title molecule, 5-(4-aminophenyl)-4-(3-methyl-3-phenylcyclobutyl)thiazol-2-amine (C20H21N3S), was prepared and characterized by 1H-NMR, 13C-NMR, IR and single-crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P21/c with a = 9.4350(5) Å, b = 11.2796(6) Å, c = 18.4170(8) Å and β = 113.378(3)°. In addition to the molecular geometry from X-ray experiment, the molecular geometry, vibrational frequencies, gauge including atomic orbital (GIAO) 1H- and 13C-NMR chemical shift values and atomic charges distribution of the title compound in the ground state have been calculated using the Hartree–Fock (HF) and density functional method (DFT) (B3LYP) with 6-31G(d) basis set. To determine conformational flexibility, molecular energy profile of the title compound was obtained by semi-empirical (AM1) calculations with respect to two selected degrees of torsional freedom, which were varied from −180° to +180° in steps of 10°. Besides, frontier molecular orbitals (FMO) analysis was performed by the B3LYP/6-31G(d) method.

1-(3-methyl-3-mesityl)-cyclobutyl-2-(5-pyridin-4-yl-2H-[1,2,4]triazol-3-ylsulfanyl)-ethanone: X-ray structure, spectroscopic characterization and DFT studies.

The triazole compound 1-(3-Methyl-3-mesityl)-cyclobutyl-2-(5-pyridin-4-yl-2H-[1,2,4]triazol-3-ylsulfanyl)-ethanone, (C23H26N4OS), was characterized by X-ray single crystal diffraction technique, IR NMR spectroscopy and quantum chemical computational methods as both experimental and theoretically. The compound crystallizes in the monoclinic space group P2(1)/c with Z=4. The molecular geometry was also optimized using density functional theory (DFT/B3LYP) method with the 6-311G(d,p) basis set in ground state and compared with the experimental data. The computed vibrational frequencies are used to determine the types of molecular motions associated with each of the experimental bands observed. The results of the calculations were applied to simulate spectra of the title compound, which show excellent agreement with observed spectra. 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. From the optimized geometry of the molecule, vibrational frequencies, gauge-independent atomic orbital (GIAO) 1H and 13C NMR chemical shift values, molecular electrostatic potential (MEP) distribution, non-linear optical properties and frontier molecular orbitals (FMOs) of the title compound were performed at B3LYP/6-311G(d,p). On the basis of theoretical vibrational analyses, the thermodynamic properties (standard heat capacities, standard entropies, and standard enthalpy changes) of the title compound at different temperatures have been calculated, revealing the correlations between Cp,m0, Sm0, ΔHm0 and temperatures. The predicted non-linear optical properties of the title compound are much greater than those of urea. 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.

4‐Benzoyl‐1,5‐diphenyl‐1H‐pyrazole‐3‐carboxylic acid methanol solvate

In the title compound, C23H16N2O3·CH4O, the N—N bond distance in the pyrazole ring, which is planar within 0.008 A, is 1.3634 (18) A. The crystal packing is stabilized by O—H⋯O, O—H⋯N and C—H⋯O intermolecular hydrogen bonds.

An experimental and theoretical approach to the molecular structure of 2-(4-[3-(2,5-dimethylphenyl)-3-methylcyclobutyl]thiazol-2-yl)isoindoline-1,3-dione.

The title compound, 2-{4-[3-(2,5-dimethylphenyl)-3-methylcyclobutyl]thiazol-2-yl}isoindoline-1,3-dione (C24H22N2O2S), was synthesized and characterized by IR-NMR spectroscopy and single-crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P21/c with a = 19.7799(13) Å, b = 6.7473(4) Å, c = 15.7259(9) Å and β = 103.416(5)°. In addition, the molecular geometry, vibrational frequencies and gauge including atomic orbital (GIAO) 1H and 13C chemical shift values of the title compound in the ground state have been calculated by using the Hartree-Fock (HF) and density functional method (DFT/B3LYP) with 6–31G(d), 6–31 + G(d,p) and LANL2DZ basis sets, and compared with the experimental data. To determine conformational flexibility, molecular energy profile of the title compound was obtained by semi-empirical (AM1) calculations with respect to two selected degrees of torsional freedom, which were varied from −180° to +180° in steps of 5°. Besides, molecular electrostatic potential, frontier molecular orbitals (FMO) analysis and thermodynamic properties of the title compound were investigated by theoretical calculations.

Synthesis, spectroscopic characterization, X-ray structure and DFT studies on 2,6-bis(1-benzyl-1H-benzo[d]imidazol-2-yl)pyridine

The title molecule, 2,6-bis(1-benzyl-1H-benzo[d]imidazol-2-yl)pyridine (C(33)H(25)N(5)), was synthesized and characterized by elemental analysis, FT-IR spectroscopy, one- and two-dimensional NMR spectroscopies, and single-crystal X-ray diffraction. In addition, the molecular geometry, vibrational frequencies and gauge-independent atomic orbital (GIAO) (1)H and (13)C NMR chemical shift values of the title compound in the ground state have been calculated using the density functional theory at the B3LYP/6-311G(d,p) level, and compared with the experimental data. The complete assignments of all vibrational modes were performed by potential energy distributions using VEDA 4 program. The geometrical parameters of the optimized structure are in good agreement with the X-ray crystallographic data, and the theoretical vibrational frequencies and GIAO (1)H and (13)C NMR chemical shifts show good agreement with experimental values. Besides, molecular electrostatic potential (MEP) distribution, frontier molecular orbitals (FMO) and non-linear optical properties of the title compound were investigated by theoretical calculations at the B3LYP/6-311G(d,p) level. The linear polarizabilities and first hyper polarizabilities of the molecule indicate that the compound is a good candidate of nonlinear optical materials. The thermodynamic properties of the compound at different temperatures were calculated, revealing the correlations between standard heat capacity, standard entropy, standard enthalpy changes and temperatures.