Copper(II) and cobalt(II) complexes of 2,6-diacetylpyridine bis(<Emphasis Type="Italic">O</Emphasis>-methyloxime): A theoretical investigation

The molecular geometries and vibrational frequencies of the title compounds in the ground state are calculated using the Hartree-Fock (HF) and density functional theory (DFT/B3LYP) methods with the LANL2DZ basis set and compared with the experimental data. The calculated results show that the optimized geometries can well reproduce the crystal structural parameters, and the theoretical vibrational frequencies show good agreement with the experimental values. The energetic behavior of the title compounds in solvent media is examined using the B3LYP method with the LANL2DZ basis set by applying the Onsager and polarizable continuum model (PCM). In addition, molecular electrostatic potential (MEP) and frontier molecular orbital (FMO) analyses of the title compounds are investigated by theoretical calculations.     

The molecular structure and vibrational spectra of 3-acetyl-4-[N-(2'-aminopyridinyl)-3-amino]-3-buten-2-one by Hartree-Fock and density functional theory calculations

The molecular structure and vibrational spectra of 3-acetyl-4-[N-(2'-aminopyridinyl)-3-amino]-3-buten-2-one (C(11)H(13)N(3)O(2)) in the ground state have been investigated by Hartree-Fock and density functional method (B3LYP and BLYP) with 6-31G(d) basis set. The optimized geometric bond lengths and bond angles obtained by using HF and DFT show the best agreement with the experimental data. Comparison of the observed fundamental vibrational frequencies of title compound and calculated results by HF and DFT methods indicate that B3LYP is superior to the scaled HF approach for molecular problems.     

Investigation of structural and biological properties of N-heterocyclic carbene silver(I) and palladium(II) complexes

abstract

Computational investigations were done on bis(1-allyl-3-benzyl-2,3-dihydro-1H-benzo[d]imidazol-2-yl)silver(I), bis(1-benzyl-3-butyl-2,3-dihydro-1H-benzo[d]imidazol-2-yl)silver(I), bis(1-allyl-3-benzyl-2,3-dihydro-1H-benzo[d]imidazol-2-yl)dibromidepalladium(II), and bis(1-benzyl-3-butyl-2,3-dihydro-1H-benzo[d]imidazol-2-yl)dibromidepalladium(II) complexes. Related complexes were optimized at different six calculation levels which are HF/6-31G(LANL2DZ), HF/6-31G(d,p)(LANL2DZ), B3LYP/6-31G(LANL2DZ), B3LYP/6-31G(d,p)(LANL2DZ), M062X/6-31G(LANL2DZ) and M062X/6-31G(d,p)(LANL2DZ) levels in vacuo. IR and NMR spectrum are calculated and examined in detail. Energy diagram of molecular orbitals, contour diagram of frontier molecular orbitals, molecular electrostatic potential maps and the harmonic surface of related molecules are examined in detail. Finally, interactions between mentioned complexes and related proteins (1BNA, 1JNX, and 2ING) are investigated in detail. As a result, it is found that biological and anti-cancer properties of silver N-heterocyclic carbene complexes are higher than those of palladium complexes.     

Molecular structure, vibrational spectra and NBO analysis of phenylisothiocyanate by density functional method

The molecular geometry, vibrational frequencies and NBO analysis of phenylisothiocyanate (PITC) in the ground state have been calculated by using density functional theory calculation (B3LYP) with 6-311++G(d,p) basis set. The optimized geometrical parameters obtained by DFT calculations are in good agreement with experimental values. Comparison of the observed fundamental vibrational frequencies of the PITC and calculated result by density functional theory (B3LYP) indicates B3LYP is superior for molecular vibrational problems. The entropy of the title compound was also performed at HF/B3LYP/6-311++G(d,p) levels of theory. Natural bond orbital (NBO) analysis of title molecule is also carried out. A detailed interpretation of the IR and Raman spectra of PITC is reported on the basis of the calculated potential energy distribution (PED). The theoretical spectrogram for IR spectrum of the title molecule has been constructed.     

Tert-butyl N-(2-bromocyclohex-2-enyl)-N-(2-furylmethyl)carbamate的结构和振动光谱

The molecular structure, conformafional stability, and vibrational frequencies of ten-butyl N-（2- bromocyclohex-2-enyl）-N-（2-furylmethyl）carbamate （TBBFC） were investigated by utilizing the Hartree-Fock （HF） and density functional theory （DFT） ab initio calculations with 6-31G ^＊ and 6-31G^＊ ＊ basis sets. The optimized bond length and angle values obtained by HF method showed the best agreement with the experimental values. Comparison of the observed and calculated fundamental vibrational frequencies indicated that B3LYP was superior to the scaled HF approach for molecular problems. Optimal uniform scaling factors calculated for the title compound are 0.899/0.904, 0.958/0.961, and 0.988/0.989 for HF, B3LYP, and BLYP （6-31G ^＊/6-31G ^＊ ＊）, respectively.     

FT-IR, FT-Raman spectra and ab initio HF and DFT calculations of 4-N,N'-dimethylamino pyridine

In this work, we will report a combined experimental and theoretical study on molecular and vibrational structure of 4-N,N'-dimethylamino pyridine (4NN'DMAP). The Fourier transform infrared and Fourier transform Raman spectra of 4NN'DMAP was recorded in the solid phase. The optimized geometry was calculated by HF and B3LYP methods with 6-31G(d,p) and 6-311++G(d,p) basis sets. The harmonic vibrational frequencies, infrared intensities and Raman scattering activities of the title compound were performed at same level of theories. The scaled theoretical wavenumber showed very good agreement with the experimental values. The thermodynamic functions of the title compound was also performed at HF/6-31G(d,p) and B3LYP/6-311++G(d,p) level of theories. A detailed interpretation of the infrared and Raman spectra of 4NN'DMAP was reported. The theoretical spectrograms for FT-IR and FT-Raman spectra of the title molecule have been constructed.     

Spectroscopic investigations and ab initio computations of the dye Chromotrope 2R

Detailed analysis of the NIR FT-Raman, FT-IR and UV–visible spectra of the dye Chromotrope 2R (C2R) has been performed. The optimized geometry of the dye is theoretically computed with the HF and DFT levels using the standard 6-31G(d) and LANL2DZ basis sets. Optimized geometry and vibrational spectra indicate that the major species in the solid state are the trans form of hydrogen bonded hydrazone tautomer. The effect of H-bonding in stabilizing a particular type of structure is also discussed. The most preferred trans-configuration for its photochemical activity has been demonstrated on the basis of torsional potential energy surface (PES) scan studies. The optimized geometries and calculated vibrational wavenumbers are evaluated via comparison with experimental values. Electronic spectra are in accordance with the nature of the electronic transitions predicted by time-dependent B3LYP/DZ calculations.     

Quantum-chemical,spectroscopic and X-ray diffraction studies on nickel complex of 2-hydroxyacetophenone thiosemicarbazone with triphenylphospine

Reaction of 2-hydroxyacetophenone thiosemicarbazone with [Ni(PPh₃)₂Cl₂] in optimized conditions afforded a mixed ligand complex with an isolated triphenylphosphine molecule. The structure was characterized by elemental analysis, IR, NMR and UV–Vis. spectroscopies and single crystal X-ray diffraction technique. In addition, 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 density functional theory (DFT/B3LYP) method with the 6-31G(d,p) basis set for the C, N, O, S, P, H atoms and LANL2DZ pseudo-potential for the Ni atom, and compared with the experimental data. Besides, atomic charge distributions, molecular electrostatic potential and frontier molecular orbitals (FMO) analysis of the title compound were investigated by theoretical calculations. The thermodynamic properties of the compound at different temperatures have been calculated and corresponding relations between the properties and temperature have also been obtained. Atomic charge distributions indicate that during forming the title compound, the free ligand of thiosemicarbazone ion transfers their negative charges to central Ni(II) ion. The effect of different solvents (chloroform, methanol and water) on the geometry, vibrational frequencies, total energies and dipole moments was studied using the density functional theory (DFT/B3LYP) method by applying the Onsager and the Polarizable Continuum Model (PCM).     

A theoretical study on 1-(thiophen-2-yl-methyl)-2-(thiophen-2-yl)-1H-benzimidazole

The molecular geometry and vibrational frequencies of 1-(thiophen-2-yl-methyl)-2-(thiophen-2-yl)-1H-benzimidazole (C(16)H(12)N(2)S(2)) 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 (C(16)H(12)N(2)S(2)) 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.     

A theoretical study on N-phenyl-N'-(2-thienylmethylene)hydrazine

The molecular geometry and vibrational frequencies of N-phenyl-N'-(2-thienylmethylene)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 DFT (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.     

Vibrational spectrum and assignments of 2-(4-methoxyphenyl)-1H-benzo[d]imidazole by ab initio Hartree-Fock and density functional methods

The room temperature attenuated total reflection Fourier transform infrared spectrum of the 2-(4-methoxyphenyl)-1H-benzo[d]imidazole has been recorded with diamond/ZnSe prism. The conformational behaviour, structural stability of optimized geometry, frequency and intensity of the vibrational bands of the title compound were investigated by utilizing ab initio calculations with 6-311G** basis set at HF, B3LYP, BLYP, B3PW91 and mPW1PW91 levels. The harmonic vibrational frequencies were calculated and scaled values have been compared with experimental IR spectrum. The observed and the calculated frequencies are found to be in good agreement. The theoretical vibrational spectra of the title compound were interpreted by means of potential energy distributions using VEDA 4 program. Furthermore, the optimal uniform scaling factors calculated for the title compound are 0.9120, 0.9596, 0.9660, 0.9699, and 0.9993 for HF, mPW1PW91, B3PW91, B3LYP and BLYP methods, respectively.     

FT-IR and FT-Raman investigation, computed vibrational intensity analysis and computed vibrational frequency analysis on m-Xylol using ab-initio HF and DFT calculations

The FT-IR and FT-Raman spectra of m-Xylol molecule have been recorded using Bruker IFS 66V spectrometer in the range 4000-100cm(-1). The molecular geometry and vibrational frequencies in the ground state are evaluated using the Hartree-fock (HF) and B3LYP with 6-31+G (d, p), 6-31++G (d, p) and 6-311++G (d, p) basis sets. The computed frequencies are scaled using a suitable scale factors to yield good agreement with the observed values. The HF and DFT analysis agree well with experimental observations. Comparison of the fundamental vibrational frequencies with calculated results by HF and B3LYP methods indicate that B3LYP/6-311++G (d, p) is superior to HF/6-31+G (d, p) for molecular vibrational problems. The complete data of this title compound provide some useful information for the study of substituted benzenes. The influences of Methyl groups on the geometry of benzene and its normal modes of vibrations have also been discussed.     

Vibrational spectra and assignments of 2-amino-5-iodopyridine by ab initio Hartree-Fock and density functional methods

The Fourier transform Raman and Fourier transform infrared spectra of 2-amino-5-iodopyridine were recorded in the solid phase. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities were calculated by HF and DFT (B3LYP) methods with the 6-31G(d,p) basis set for C, N, H and LANL2DZ pseudopotential for I. The scaled theoretical wavenumbers showed very good agreement with the experimental ones. A detailed interpretation of the infrared and Raman spectra of 2-amino-5-iodopyridine is reported on the basis of the calculated potential energy distribution. The theoretical spectrograms for the IR spectrum of the title molecule have been constructed.     

Vibrational spectroscopy investigation using ab initio and density functional theory analysis on the structure of 3-(6-benzoyl-2-oxobenzo[d]oxazol-3(2H)-yl)propanoic acid

The molecular structure, vibrational frequencies and infrared intensities of the 3-(6-benzoyl-2-oxobenzo[d]oxazol-3(2H)-yl)propanoic acid were calculated by the HF and DFT methods using 6-31G(d) basis set. The FT-infrared spectra have been measured for the title compound in the solid state. We obtained 11 stable conformers for the title compound, however the Conformer 1 is approximately 3.88 kcal/mol more stable than the Conformer 11. The comparison of the theoretical and experimental geometry of the title compound shows that the X-ray parameters fairly well reproduce the geometry of the Conformer 1. The harmonic vibrations computed of this compound by the B3LYP/6-31G(d) method are in a good agreement with the observed IR spectral data. Theoretical vibrational spectra of the title compound were interpreted by means of PEDs using VEDA 4 program.     

Experimental and computational studies on zwitterionic (E)-2-(1-(2-(4-methylphenylsulfonamido)ethyliminio)ethyl) phenolate

The Schiff base compound (E)-2-(1-(2-(4-methylphenylsulfonamido)ethyliminio)ethyl) phenolate has been synthesised and characterized by IR, UV–Vis, and X-ray single-crystal determination. Ab initio calculations have been carried out for the title compound using the density functional theory (DFT) and Hartree–Fock (HF) methods at 6-31G(d) basis set. The calculated results show that the DFT/B3LYP and HF can well reproduce the structure of the title compound. Using the TD-DFT and TD-HF methods, electronic absorption spectra of the title compound have been predicted and a good agreement with the TD-DFT method and the experimental ones is determined. Molecular orbital coefficient analyses reveal that the electronic transitions are mainly assigned to n → π* and π → π* electronic transitions. To investigate the tautomeric stability, optimization calculations at B3LYP/6-31G(d) level were performed for the NH and OH forms of the title compound. Calculated results reveal that the OH form is more stable than NH form. In addition, molecular electrostatic potential and NBO analysis of the title compound were performed at B3LYP/6-31G(d) level of theory.     

Vibrational spectra and molecular structure of chiral and racemic 4-phenyl-1,3-oxazolidin-2-one by density functional theory and ab initio Hartree-Fock calculations

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.     

NMR Parameters and Vibrational Investigation of 2-Dicyanovinyl-5-（4-ethoxyphenyl） thiophene by ab initio HF and DFT Calculations

Optimized geometry and harmonic vibrational frequency of 2-dicyanovinyl-5-(4- ethoxyphenyl)thiophene (C16H12N2OS) are calculated at the HF/6-31++G(d,p) and B3LYP/6- 311++G(d,p) levels. Mulliken charges in the ground state are also calculated. The research shows the presence of intermolecular interaction in the title compound. The scaled harmonic vibrational frequencies have been compared with experimental FT-IR spectra. A detailed interpretation of the infrared spectra of the title compound is reported. The theoretical spectrograms for IR spectra of the title compound have been constructed. The isotropic chemical shift computed by 13C and 1H NMR analyses also shows good agreement with the experimental observations.     

FT-IR, FT-Raman spectra and quantum chemical calculations of 3,4-dimethoxyaniline

In this work, we will report a combined experimental and theoretical study on molecular and vibrational structure of 3,4-dimethoxyaniline (3,4-DMA). The Fourier transform infrared and Fourier transform Raman spectra of 3,4-DMA was recorded in the solid phase. The optimized geometry was calculated by HF and B3LYP methods using 6-31G(d,p) and 6-311++G(d,p) basis sets. The harmonic vibrational frequencies, infrared intensities, Raman scattering activities and the thermodynamic functions of the title compound were performed at and HF/B3LYP/6-311++G(d,p) level of theories. The scaled theoretical wavenumber showed very good agreement with the experimental values. A detailed interpretation of the infrared and Raman spectra of 3,4-DMA was reported. The theoretical spectrograms for IR and Raman spectra of the title molecule have been constructed.     

Theoretical studies of molecular structure and vibrational spectra of melaminium citrate

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.     

Vibrational spectroscopy investigation using ab initio and density functional theory analysis on the structure of 3-aminobenzotrifluoride

In this work, we will report a combined experimental and theoretical study on molecular and vibrational structure of 3-aminobenzotrifluoride. The FT-Raman and Fourier transform infrared spectra of 3-aminobenzotrifluoride (3ABTF) were recorded in the liquid phase. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities, depolarization ratios, reduced masses were calculated by HF and density functional B3LYP method with the 6-31G(d,p) and 6-311G(d,p) basis sets. The scaled theoretical wavenumbers showed very good agreement with the experimental values. The thermodynamic functions of the title compound were also performed at HF/6-31G(d,p)/6-311G(d,p) and B3LYP/6-31G(d,p)/6-311G(d,p) levels of theory. A detailed interpretations of the infrared and Raman spectra of 3ABTF is reported. The theoretical spectrograms for FT-IR spectra of the title molecule have been constructed.