Cemal Parlak

DFT, FT-Raman and FT-IR investigations of 5-methoxysalicylic acid.

FT-IR and FT-Raman spectra of 5-methoxysalicylic acid (5MeOSA) have been experimentally reported in the region of 4000-10 cm(-1) and 4000-50 cm(-1), respectively. The optimized geometric parameters, conformational equilibria, normal mode frequencies and corresponding vibrational assignments of 5MeOSA (C(8)H(8)O(4)) are theoretically examined by means of B3LYP hybrid density functional theory (DFT) method together with 6-31++G(d,p) basis set. Furthermore, reliable vibrational assignments have made on the basis of potential energy distribution (PED) calculated and the thermodynamics functions, highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of 5MeOSA have been predicted. Calculations are employed for different conformations of 5MeOSA, both in gas phase and in solution. Solvent effects are investigated using chloroform and dimethylsulfoxide. All results indicate that B3LYP method is able to provide satisfactory results for predicting vibrational frequencies and the structural parameters, vibrational frequencies and assignments, IR and Raman intensities of 5MeOSA are solvent dependent.

Vibrational spectroscopic investigation and conformational analysis of 1-heptylamine: A comparative density functional study

The possible stable conformers of 1-pentylamine (1-pa) molecule were experimentally and theoretically studied by FT-IR and Raman spectroscopy in the region of 4000–400 cm-1. The optimized geometric structures concerning the minimum on the potential energy surface were investigated by Becke-3–Lee–Yang–Parr (B3LYP) density functional method together with 6-31G(d) basis set. Based on the energy calculations, 10 possible rotamers of 1-pa (TT, TG, GT, GT1, GG1, GG2, GG3, GG4, GG5 and GG6; T and G denote trans and gauge, respectively) were proposed. Optimized energies of the possible conformers were obtained in the gas phase and within the chloroform, carbon tetrachloride, methanol and water solvent environments all of which have different polarities. Comparison between the experimental and theoretical results based on the correlation graphics and mean absolute error calculations presented in this study indicates that density functional B3LYP method is able to provide satisfactory results for predicting vibrational wavenumbers and TT isomer is the most stable form of 1-pa molecule.

Synthesis, molecular structure, FT-IR, Raman, XRD and theoretical investigations of (2E)-1-(5-chlorothiophen-2-yl)-3-(naphthalen-2-yl)prop-2-en-1-one

A novel (2E)-1-(5-chlorothiophen-2-yl)-3-(naphthalen-2-yl)prop-2-en-1-one [C17H11ClOS] compound has been synthesized and its structure has been characterized by FT-IR, Raman and single-crystal X-ray diffraction techniques. The isomers, optimized geometrical parameters, normal mode frequencies and corresponding vibrational assignments of the compound have been examined by means of the density functional theory method, employing, the Becke-3-Lee-Yang-Parr functional and the 6-311+G(3df,p) basis set. 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 monoclinic space group P2₁/c with the unit cell parameters a=5.7827(8)Å, b=14.590(2)Å, c=16.138(2)Å and β=89.987 (°). The CC bond of the central enone group adopts an E configuration. There is a good agreement between the theoretically predicted structural parameters and vibrational frequencies and those obtained experimentally.

FT-IR and Raman spectroscopic and quantum chemical investigations of some metal halide complexes of 1-phenylpiperazine

New metal halide complexes in the form of M(pp)(2)Cl(2) (where pp=1-phenylpiperazine and M=Pd or Hg) have been prepared for the first time and their FT-IR and FT-Raman spectra are reported in the region of 4000-10 cm(-1) and 4000-50 cm(-1), respectively. The optimized geometric parameters, normal mode frequencies and corresponding vibrational assignments of the present compounds are theoretically examined by means of B3LYP hybrid density functional theory (DFT) method together with Lanl2dz basis set. Furthermore, reliable vibrational assignments made on the basis of potential energy distribution (PED) were calculated and the thermodynamics functions, the highest occupied and the lowest unoccupied molecular orbitals (HOMO and LUMO) of these compounds have been predicted. According to the results, theoretical values have been successfully compared against experimental data.

1H, 13C, 15N NMR and nJ(C, H) coupling constants investigation of 3-piperidino-propylamine: A combined experimental and theoretical study

Proton coupled and decoupled (13)C, (1)H, (15)N, DEPT, COSY, HETCOR and INADEQUATE NMR spectra of 3-piperidino-propylamine (3-pipa) have been reported for the first time. In order to provide a precise structural elucidation, the magnitude of (n)J(C, H) (n=1, 2, 3) coupling constants of 3-pipa (C(8)H(18)N(2)) have been determined. Solvent effects on chemical shifts have been investigated by using CDCl(3) and DMSO. Molecular mobility of the title molecule has also been investigated by performing (13)C NMR spin-lattice relaxation time (T(1)) measurements. (13)C, (1)H and (15)N NMR chemical shifts and (1-3)J(C, H) coupling constants of 3-pipa have been calculated by means of B3LYP density functional method with 6-311++G(d,p) basis set. Comparison between the experimental and the theoretical results indicates that density functional B3LYP method is able to provide satisfactory results for predicting NMR properties.

Different Response of Carbonyl Carotenoids to Solvent Proticity Helps To Estimate Structure of the Unknown Carotenoid from Chromera velia

In order to estimate the possible structure of the unknown carbonyl carotenoid related to isofucoxanthin from Chromera velia denoted as isofucoxanthin-like carotenoid (Ifx-l), we employed steady-state and ultrafast time-resolved spectroscopic techniques to investigate spectroscopic properties of Ifx-l in various solvents. The results were compared with those measured for related carotenoids with known structure: fucoxanthin (Fx) and isofucoxanthin (Ifx). The experimental data were complemented by quantum chemistry calculations and molecular modeling. The data show that Ifx-l must have longer effective conjugation length than Ifx. Yet, the magnitude of polarity-dependent changes in Ifx-l is larger than for Ifx, suggesting significant differences in structure of these two carotenoids. The most interesting spectroscopic feature of Ifx-l is its response to solvent proticity. The transient absorption data show that (1) the magnitude of the ICT-like band of Ifx-l in acetonitrile is larger than in methanol and (2) the S1/ICT lifetime of Ifx-l in acetonitrile, 4 ps, is markedly shorter than in methanol (10 ps). This is opposite behavior than for Fx and Ifx whose S1/ICT lifetimes are always shorter in protic solvent methanol (20 and 13 ps) than in aprotic acetonitrile (30 and 17 ps). Comparison with other carbonyl carotenoids reported earlier showed that proticity response of Ifx-l is consistent with presence of a conjugated lactone ring. Combining the experimental data and quantum chemistry calculations, we estimated a possible structure of Ifx-l.

FT-IR and Raman spectroscopic analysis of some Hofmann type complexes.

Some new Hofmann type complexes with chemical formula of M(4 pypp)(2)Ni(CN)(4) (where 4 py pp=4-(1-pyrrolidinyl)piperidine and MNi or Co) were prepared and their FT-IR and Raman spectra were reported in the region of 4000-200 cm(-1) and 4000-100 cm(-1), respectively. The ligand molecule, polymeric sheet and metal-ligand bands of the compounds were assigned in detail. Vibrational spectra together with assignments of 4 pypp (C(9)H(18)N(2)) were experimentally and theoretically studied in the region of 400-100 cm(-1). Normal mode frequencies and corresponding vibrational assignments of Ni(CN)(4)(2-) were theoretically examined by standard quantum chemical technique. Reliable vibrational assignments were made on the basis of potential energy distribution (PED) analysis. The results suggest that these compounds are similar in structure to the Hofmann type complexes and the 4 phpy ligand molecule bonds to the metal (M) atom of |M-Ni(CN)(4)|(∞) polymeric layers.

Experimental and theoretical FT-IR, Raman and XRD study of 2-acetyl-5-chlorothiophene.

The structure of 2-acetyl-5-chlorothiophene (ACT) has been characterized by FT-IR, Raman and single-crystal X-ray diffraction techniques. The isomers, optimized geometric parameters, normal mode frequencies and corresponding vibrational assignments of ACT (C6H5ClOS) have been examined by the density functional theory, with the Becke-3-Lee-Yang-Parr functional and the 6-311+G(3df,p) basis set. Reliable vibrational assignments have been investigated by the potential energy distribution analysis. ACT crystallizes in monoclinic space group C2/c with the O,S-cis isomer. There is a good agreement between the theoretically predicted structural parameters and vibrational frequencies and those obtained experimentally.

Synthesis, molecular structure, FT-IR and XRD investigations of 2-(4-chlorophenyl)-2-oxoethyl 2-chlorobenzoate: a comparative DFT study

2-(4-Chlorophenyl)-2-oxoethyl 2-chlorobenzoate has been synthesized, its structural and vibrational properties have been reported using FT-IR and single-crystal X-ray diffraction (XRD) studies. The conformational analysis, optimized geometric parameters, normal mode frequencies and corresponding vibrational assignments of the synthesized compound (C15H10Cl2O3) have been examined by means of Becke-3-Lee-Yang-Parr (B3LYP) density functional theory (DFT) method together with 6-31++G(d,p) basis set. Furthermore, reliable conformational investigation and vibrational assignments have been made by the potential energy surface (PES) and potential energy distribution (PED) analyses, respectively. Calculations are performed with two possible conformations. The title compound crystallizes in orthorhombic space group Pbca with the unit cell dimensions a=12.312(5) Å, b=8.103(3) Å, c=27.565(11) Å, V=2750.0(19) Å(3). B3LYP method provides satisfactory evidence for the prediction of vibrational wavenumbers and structural parameters.

Conformation stability, halogen and solvent effects on CO stretching of 4-chloro-3-halogenobenzaldehydes.

The effects of halogen and solvent on the conformation and carbonyl stretching of 4-chloro-3-halogenobenzaldehydes [C7H4ClXO; X=F (CFB), Cl (CCB) or Br (CBB)] were investigated using the density functional theory (DFT) method. The B3LYP functional was used by the 6-311+G(3df,p) basis set in combination with the polarizable continuum model (PCM). Computations were focused on the cis and trans isomers of the compounds in 18 different polar or non-polar organic solvents. The theoretical frequencies of the solvent-induced CO stretching vibrations were correlated with the empirical solvent parameters such as the Kirkwood-Bauer-Magat (KBM) equation, the solvent acceptor number (AN), Swain parameters and the linear solvation energy relationships (LSER). The present work explores the effect of both the halogen and medium on the conformational preference and CO vibrational frequency. The findings of this work can be useful to those systems involving changes in the conformations analogous to the compounds studied.