Semiha Bahçeli

A study on quantum chemical calculations of 3-, 4-nitrobenzaldehyde oximes

The molecular geometry, vibrational frequencies, 1H and 13C NMR chemical shifts, UV-vis spectra, HOMO-LUMO analyses, molecular electrostatic potentials (MEPs), , thermodynamic properties and atomic charges of 3- and 4-Nitrobenzaldehyde oxime (C7H6N2O3) molecules have been investigated by using Hartree-Fock (HF) and density functional theory (DFT/B3LYP) methods with the 6-311++G(d, p) basis set. The calculated optimized geometric parameters (bond lengths and bond angles), the vibrational frequencies calculated and 13C and 1H NMR chemical shifts values for the mentioned compounds are in a very good agreement with the experimental data. Furthermore, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) have been simulated and the transition states, energy band gaps and molecular electrostatic potential (MEP) maps for each oxime compound have been determined. Additionally, we also report the infrared intensities and Raman activities for the compounds under study.

Quantum chemical computations of 1,3-phenylenediacetic acid.

Molecular geometry, vibrational wavenumbers and gauge including atomic orbital (GIAO) 13C NMR and 1H NMR chemical shift values of 1,3-phenylenediacetic acid (C10H10O4), in the ground state have been calculated by using ab initio Hartree-Fock (HF) and density functional theory (DFT/B3LYP) methods with 6-311++G(d,p) basis set for the first time. Comparison of the observed fundamental vibrational modes of 1,3-phenylenediacetic acid and calculated results by density functional B3LYP and Hartree-Fock methods indicate that B3LYP is superior to the scaled Hartree-Fock approach for quantum chemical studies. Geometric parameters (bond lengths and bond angles) and vibrational wavenumbers obtained by the HF and DFT/B3LYP methods are in good agreement with the experimental data. Furthermore, this is the first time the results of the calculated JCH and JCC coupling constants of the C10H10O4 molecule are presented in this study.

Analysis of molecular structure, spectroscopic properties (FT-IR, micro-Raman and UV–vis) and quantum chemical calculations of free and ligand 2-thiopheneglyoxylic acid in metal halides (Cd, Co, Cu, Ni and Zn)

In this study, molecular geometries, experimental vibrational wavenumbers, electronic properties and quantum chemical calculations of 2-thiopheneglyoxylic acid molecule, (C6H4O3S), and its metal halides (Cd, Co, Cu, Ni and Zn) which are used as pharmacologic agents have been investigated experimentally by FT-IR, micro-Raman and UV-visible spectroscopies and elemental analysis. Meanwhile the vibrational calculations were verified by DFT/B3LYP method with 6-311++G(d,p) and LANL2DZ basis sets in the ground state, for free TPGA molecule and its metal halide complexes, respectively, for the first time. The calculated fundamental vibrational frequencies for the title compounds are in a good agreement with the experimental data.

Spectroscopic and quantum chemical studies on bromopyrazone

In this study, the FT-IR, micro-Raman and UV-vis. spectra of bromopyrazone molecule, C10H8BrN3O, (with synonym,1-phenyl-4-amino-5-bromopyridazon-(6) or 5-amino-4-bromo-2-phenyl-3(2H)-pyridazinone) were recorded experimentally. The molecular structure, vibrational wavenumbers, electronic transition absorption wavelengths in ethanol solvent, HOMOs and LUMOs analyses, molecular electrostatic potential (MEP), natural bond orbitals (NBO), nonlinear optical (NLO) properties and atomic charges of bromopyrazone molecule have been calculated by using DFT/B3LYP method with 6-311++G(d,p) basis set in ground state. The obtained results show that the calculated vibrational frequencies and UV-vis. values are in a good agreement with experimental data.

The molecular structures, vibrational spectroscopies (FT-IR and Raman) and quantum chemical calculations of n-alkyltrimethylammonium bromides

The FT-IR and micro-Raman spectra of three n-alkyltrimethylammonium bromides (dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB) and hexadecyl(cetyl)trimethylammonium bromide (CTAB)) in powder form were recorded in the regions 4000–550 cm−1 and 3200–300 cm−1, respectively. The optimized geometries and vibrational frequencies of DTAB, TTAB and CTAB have been carried out with ab initio Hartree-Fock (HF) and density functional theory method B3LYP calculations with the 6–31 G (d, p) basis set in the ground state. The comparison of the observed fundamental vibrational frequencies and calculated results for the fundamental vibrational frequencies of DTAB, TTAB and CTAB indicate that the scaled B3LYP method is superior compared to the scaled HF method.

Quantum chemical computational studies on 5-(4-bromophenylamino)-2-methylsulfanylmethyl-2H-1,2,3-triazol-4-carboxylic acid ethyl ester

The optimized molecular geometry, vibrational frequencies, and gauge including atomic orbital (GIAO) (1)H and (13)C NMR shift values of 5-(4-bromophenylamino)-2-methylsulfanylmethyl-2H-1,2,3-triazol-4-carboxylic acid ethyl ester have been calculated by using Hartree-Fock (HF) and density functional method (DFT/B3LYP) with 6-31G(d), 6-31G(d,p) and LANL2DZ basis sets. The optimized molecular geometric parameters were presented and compared with the data obtained from X-ray diffraction. In order to fit the calculated harmonic wavenumbers to the experimentally observed ones, scaled quantum mechanics force field (SQM FF) methodology was proceeded. Correlation factors between the experimental and calculated (1)H chemical shift values of the title compound in vacuum and in CHCl(3) solution by using the conductor-like screening continuum solvation model (COSMO) were reported. The calculated results showed that the optimized geometry well reproduces the crystal structure. The theoretical vibrational frequencies and chemical shifts are in very good agreement with the experimental data. In solvent media the energetic behavior of the title compound was also examined by using the B3LYP method with the 6-31G(d) basis set, applying the COSMO model. The obtained results indicated that the total energy of the title compound decreases with increasing polarity of the solvent. Furthermore, molecular electrostatic potential (MEP), natural bond orbital (NBO) and frontier molecular orbitals (FMOs) of the title compound were performed by the B3LYP/LANL2DZ method, and also thermodynamic parameters for the title compound were calculated at all the HF and B3LYP levels.

Quantum chemical investigations of a co-crystal of 1,3,5-tris(4-hydroxyphenyl)benzene and 2,4,6-trimethoxy-1,3,5-triazine

In the present study, quantum chemical investigations were carried out on our previously reported co-crystal based on 1,3,5-tris(4-hydroxyphenyl)benzene and 2,4,6-trimethoxy-1,3,5-triazine, which showed CH···π and π···π interactions driven layer-by-layer self-assembly of hydrogen-bonded hexagonal blocks in the solid state. Using the DFT/B3LYP calculation method with 6-311++G(d,p) basis set in the ground state, the optimized molecular geometric parameters, conformational analysis, vibrational wavenumbers and their assignments, the HOMO–LUMO analysis, molecular electrostatic potential, thermodynamic properties, and atomic charges were calculated to understand various structural features that are playing an important role in its packing. Furthermore, the simulated infrared and Raman spectra of the co-crystal are plotted using the calculated results. The calculated results are in a good agreement with experimental data. The study with constructive propositions may be helpful in understanding complex self-assembled systems and in the construction of similar molecular self-assemblies.Graphical abstract

Product operator theory for spin-3/2 nuclei and application to 2D J-resolved NMR spectroscopy

Abstract The detailed description of the product operator formalism for a weakly coupled IS (I=1/2, S=3/2) spin system has been presented and the shorthand notations for the evolutions of Ix, Iy, IxSz and IySz product operators under the spin–spin coupling Hamiltonian have been obtained in a different form. Furthermore, as an application and a verification, the product operator formalism has been used for the analytical description of a 2D J-resolved nuclear magnetic resonance (NMR) experiment for IS (I=1/2, S=3/2) spin systems.

Crystallographic structure and quantum chemical computations of 1-(3,4-dimethylphenyl)-3-phenyl-5-(4-methoxyphenyl)-2-pyrazoline.

In this study the experimental crystallographic structure and the calculated optimized geometric parameters, vibrational wavenumbers, (1)H NMR and (13)C NMR chemical shift values, electronic absorption maximum wavelength values, HOMO-LUMO analysis, and molecular electrostatic potential (MEP) of 1-(3,4-dimethylphenyl)-3-phenyl-5-(4-methoxyphenyl)-2-pyrazoline (in abbreviated 1h), molecule, (C24H24N2O), by using density functional theory (DFT/B3LYP) method with 6-311++G(d,p) basis set in the ground state have been reported for the first time. Furthermore the IR and Raman spectra of title molecule were simulated by using calculated vibrational results. Geometric parameters (bond lengths and bond angles) vibrational wavenumbers and (13)C &(1)H NMR chemical shift values for the mentioned compound calculated at B3LYP/6-311++G(d,p) level are in good agreement with the experimental data.

Adsorption of Cr(VI) from Aqueous Solutions Onto Raw and Acid-Activated Reşadiye and Hançılı Clays

ABSTRACT The adsorption of Cr(VI) from aqueous solutions onto raw and acid-activated clays—namely, Reşadiye region clay (R, raw Reşadiye region clay; R-H2SO4, acid-activated with H2SO4 Reşadiye region clay; R-HCl, acid-activated with HCl Reşadiye region clay) and Hançılı region clay (H, raw Hançılı region clay; H-H2SO4, acid-activated with H2SO4 Hançılı region clay; H-HCl, acid-activated with HCl Hançılı region clay)—was studied in a batch system. For optimization of the Cr(VI) adsorption on raw clays and acid-activated clays, the effect of pH, temperature, initial Cr(VI) concentration, time, and adsorbent dosage were investigated. X-ray diffraction analyses of raw and acid-activated clays were used to determine the effects of acid-activating on the layer structure of the clays. The surface characterizations of clays and modified clays were performed by using FT-IR spectroscopy. The Langmuir and Freundlich adsorption models were employed to describe the equilibrium isotherms, and thus the isotherm constants were determined. The data obtained from our investigations were well described by the Langmuir model. The adsorption capacity of the adsorbents Reşadiye and Hançılı clays were found to be 0.0269, 0.0144, and 0.0170 mmol/g for H, H-HCl, and H-H2SO4 and 0.0356, 0.0276, and 0.0422 mmol/g for R, R-HCl, and R-H2SO4, respectively. The results show that the adsorption was strongly dependent on pH of the medium, initial Cr(VI) concentration and temperature. The removal of Cr(VI) reached saturation in about 120 min, and the adsorption process of Cr(VI) was observed as exothermic. A maximum removal of 73% was noted at 1.0 × 10−4 M concentration of Cr(VI) in solution for H-HCl. Furthermore the enhancement of removal of Cr(VI) was observed from pH 3 to 4. The results are discussed to highlight the influence of acid activation on Cr(VI) adsorption characteristics of the clays.