Metin Bilge

A joint theoretical and experimental study of 1-acetylpiperazine: Conformational stability, infrared and Raman spectra

Infrared and Raman spectra of 1-acetylpiperazine (1-ap) have been recorded in the region of 4000-40cm(-1). The conformational isomers, optimized geometric parameters, normal mode frequencies and corresponding vibrational assignments of 1-ap (C6H12N2O) have been examined by density functional theory (DFT), with the Becke-3-Lee-Yang-Parr (B3LYP) functional and the 6-31++G(d,p) basis set. Reliable conformational investigation and vibrational assignments have been performed by the potential energy surface (PES) and potential energy distribution (PED) analyses, respectively. Computations are carried out in both gas phase and solution using benzene and methanol. There is a good agreement between the theoretically predicted structural parameters and vibrational frequencies and those obtained experimentally. The normal chair conformation with equatorial substituents is not preferred due to the steric interaction.

Vibrational Spectroscopic Investigation and Conformational Analysis of Methacrylamidoantipyrine: A Comparative Density Functional Study

FT-IR and Raman spectra of methacrylamidoantipyrine (MAAP) have been reported in the region of 4000–10 cm−1 and 4000–100 cm−1, respectively. The optimized geometric parameters, conformational analysis, normal mode frequencies, and corresponding vibrational assignments of MAAP (C15H17N3O2) have been examined by means of density functional theory (DFT) method using the Becke-3-Lee-Yang-Parr (B3LYP) exchange-correlation functional and the 6-31G

(2E)-1-(5-Chlorothiophen-2-yl)-3-{4-[(E)-2-phenylethenyl]phenyl}prop-2-en-1-one: Synthesis, XRD, FT-IR, Raman and DFT studies.

A novel (2E)-1-(5-chlorothiophen-2-yl)-3-{4-[(E)-2-phenylethenyl]phenyl}prop-2-en-1-one [C21H15ClOS] compound has been synthesized and its structure has been characterized by FT-IR, Raman and single-crystal X-ray diffraction techniques. The conformational isomers, optimized geometric parameters, normal mode frequencies and corresponding vibrational assignments of the compound have been examined by means of HF, MP2, BP86, BLYP, BMK, B3LYP, B3PW91, B3P86 and M06-2X functionals. Reliable vibrational assignments and molecular orbitals have been investigated by the potential energy distribution and natural bonding orbital analyses, respectively. The compound crystallizes in the triclinic space group P-1 with the cis-trans-trans form. There is a good agreement between the experimentally determined structural parameters and vibrational frequencies of the compound and those predicted theoretically using the density functional theory with the BLYP and BP86 functionals.

Crystal structure, vibrational spectra and DFT simulations of 2-fluoro-4-bromobenzaldehyde

Molecular structure and properties of 2-fluoro-4-bromobenzaldehyde (FBB, C7H4BrFO) was experimentally investigated by X-ray diffraction technique and vibrational spectroscopy. Experimental results on the molecular structure of FBB were supported with computational studies using the density functional theory, with the Becke-3-Lee-Yang-Parr functional and the 6-311+G(3df,p) basis set. Molecular dimer formed by the intermolecular hydrogen bonding was investigated. Potential energy distribution analysis of normal modes was performed to identify characteristic frequencies. FBB crystallizes in orthorhombic space group P2(1)2(1)2(1) with the O-trans conformation. In order to investigate halogen effect, the chloro- (CBB) and bromo- (BBB) analogs of FBB have also been studied theoretically. It is observed that all compounds prefer the stable O-trans conformation. Although the free energy difference between the O-cis and O-trans conformers is less than 2.5 kcal/mol, the free energy rotational barrier is at least 7.4 kcal/mol. There is a good agreement between the experimentally determined structural parameters, and vibrational frequencies of FBB and those predicted theoretically.

Crystallographic, vibrational and DFT studies of 1-(2-hydroxy-4,5-dimethylphenyl)ethanone.

Molecular structure and properties of 1-(2-hydroxy-4,5-dimethylphenyl)ethanone were experimentally investigated by X-ray diffraction technique and vibrational spectroscopy. Experimental results on the molecular structure of the reported compound were supported with computational studies using the density functional theory (DFT), with the Becke-3-Lee-Yang-Parr (B3LYP) functional and the 6-311+G(3df,p) basis set. Potential energy distribution (PED) and potential energy surface (PES) analyses were performed to identify characteristic frequencies and reliable conformational analysis correspondingly. The compound crystallizes in monoclinic space group C2/c with the CO up-OH down conformation. There is a good agreement between the experimentally determined geometrical parameters and vibrational frequencies of the compound to those predicted theoretically.

DFT, FT-Raman, and FT-IR investigations of 1-cyclopropylpiperazine

FT-IR and FT-Raman spectra of 1-cyclopropylpiperazine (1cppp) are experimentally examined in the range 4000-200 cm−1. The optimized geometric parameters, conformational equilibria, normal mode frequencies and corresponding vibrational assignments of 1cppp C7H14N2 are theoretically examined by means of B3LYP hybrid density functional theory (DFT) with the 6–31++G(d,p) basis set. Based on the potential energy distribution (PED) reliable vibrational assignments are made and the thermodynamics functions, highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of 1cppp are predicted. Calculations are performed for four different conformations in two point groups of 1cppp in the gas phase. A comparison between the experimental and theoretical results indicates that the B3LYP method is able to provide satisfactory results for the prediction of vibrational frequencies, structural parameters, and assignments. Furthermore, the Cs (equatorial-equatorial) point group is found as the most stable conformer of 1cppp.

Molecular, vibrational and electronic structure of 4-bromo-2-halogenobenzaldehydes: Halogen and solvent effects

Abstract The halogen and solvent effects on the structure of 4-bromo-2-halogenobenzaldehydes [C7H4BrXO; X = F (BFB), Cl (BCB) or Br (BBB)] were investigated by the density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. The B3LYP functional and HF and MP2 levels of theory were used with the 6-311+G(3df,p) or aug-cc-pVDZ basis sets. Computations were focused on the cis and trans conformers of the investigated compounds in the gas phase and solutions of 18 different polar or non-polar organic solvents. The computed frequencies of the C=O stretching vibration of the compounds were correlated with some empirical solvent parameters such as the Kirkwood–Bauer–Magat (KBM) equation, solvent acceptor number (AN), Swain parameters and linear solvation energy relationships (LSERs). The electronic properties of the compounds were also examined. The present work explores the effects of the medium and halogen on the conformation, geometrical parameters, dipole moment, ν(C=O) vibration, UV data, frontier orbitals and density-of-states diagram of the compounds. The findings of this research can be useful for studies on benzaldehydes.

DFT, FT-IR and Raman investigations of 1-pyrrolidino-1-cyclopentene.

FT-IR and Raman spectra of 1-pyrrolidino-1-cyclopentene (1py1cp) were experimentally reported in the region of 4000-10 cm(-1) and 4000-100 cm(-1), respectively. The optimized geometric parameters, normal mode frequencies and corresponding vibrational assignments of 1py1cp (C9H15N) were theoretically examined by means of the B3LYP hybrid density functional theory (DFT) method together with the 6-31++G(d,p) basis set. Furthermore, reliable vibrational assignments were made on the basis of the potential energy distribution (PED) and the thermodynamics functions, the highest occupied and the lowest unoccupied molecular orbitals (HOMO and LUMO) of 1py1cp were predicted. Calculations were carried out employed for three different conformations of 1py1cp in gas phase. Comparison between the experimental and theoretical results indicates that density functional B3LYP method is able to provide satisfactory results for predicting vibrational wavenumbers and envelope conformer is predicted to be the most stable conformer of 1py1cp.

DFT, FT-Raman and FT-IR investigations of 5-o-tolyl-2-pentene

FT-IR and Raman spectra of 5-o-tolyl-2-pentene (OTP) have been experimentally reported in the region of 4000-10 cm(-1) and 4000-100 cm(-1), respectively. The optimized geometric parameters, normal mode frequencies and corresponding vibrational assignments of cis and trans isomers of OTP (C12H16) have been theoretically examined by means of B3LYP hybrid density functional theory (DFT) method together with 6-31G(d) and 6-31++G(d,p) basis sets. Furthermore, reliable vibrational assignments have made on the basis of potential energy distribution (PED) calculated. Comparison between the experimental and theoretical results indicates that density functional B3LYP method is able to provide satisfactory results for predicting vibrational wavenumbers and trans isomer is supposed to be the most stable form of OTP molecule.

Pt(CN)42- İYONUNUN TİTREŞİM FREKANSLARI VE YAPISAL İNCELEMESİ

The normal mode frequencies and corresponding vibrational assignments of Pt(CN)42- ion have been theoretically examined by means of standard quantum chemical techniques. All normal modes have been assigned to one of six types of motion (CN and Pt-C stretching, Pt-CN in plane and out of plane bending, C-Pt-C in plane and out of plane bending) utilizing the D4h symmetry of Pt(CN)42- ion. Calculations have been performed at HF, BLYP and B3LYP levels of theory using the Lanl2dz effective core basis set. Infrared intensities and Raman activities of vibrational frequencies have also been calculated. Theoretical results have been successfully compared against available experimental data.