FT-IR, HF and DFT structural, vibrational analysis of 5-chloro-3-(2-(4-ethylpiperazin-1-yl)-2-oxoethyl)benzo[d]thiazol-2(3H)-one molecule.

The optimized molecular geometry, vibrational frequencies, atomic charges, dipole moment, rotational constants and several thermodynamic parameters of 5-chloro-3-(2-(4-ethylpiperazin-1-yl)-2-oxoethyl)benzo[d]thiazol-2(3H)-one (abbreviated as CEOT) molecule in the ground state were calculated using ab initio Hartree-Fock (HF) and Density Functional B3LYP methods (DFT) with 6-311++G(d,p), 6-311G(d,p), 6-31++G(d,p) and 6-31G(d,p) basis sets. The Fourier-transform infrared (FT-IR) spectrum of CEOT has been recorded in the region 4000-400 cm(-1). The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FT-IR spectrum. Energy gap of the molecule was found using HOMO and LUMO calculation, hence the less band gap, which seems to be more stable. The observed and calculated vibrational frequencies are found to be in good agreement.

Ab initio HF, DFT and experimental (FT-IR) investigation of vibrational spectroscopy of 3-(2-(4-isopropylpiperazin-1-yl)-2-oxoethyl)-6-(4-methoxybenzoyl)benzo[d]thiazol-2(3H)-one.

FT-IR spectra was recorded for 3-(2-(4-isopropylpiperazin-1-yl)-2-oxoethyl)-6-(4-methoxybenzoyl)benzo[d]thiazol-2(3H)-one molecule (abbreviated as IOMBT) sample in solid state. Conformational analysis of IOMBT was performed to determine the most stable conformer. Potential energy curves of IOMBT were obtained performing a relaxed scan of D1-7 dihedral angels at B3LYP/6-311++G(d,p) level of theory. Geometrical parameters of these structures were optimized by using the same method. The molecular geometry of IOMBT was reoptimized at DFT(B3LYP) and HF methods using 6-311++G(d,p), 6-311+G(d), 6-311G(d,p), 6-311G(d) and 6-31++G(d,p) basis sets for the lowest energy conformer. The vibrational frequencies, IR intensities were calculated at DFT(B3LYP) and HF methods. The thermodynamic parameters (such as zero-point vibrational energy, EHOMO, ELUMO, thermal corrections to energy, enthalpy and Gibbs free energy, and entropy) have also been computed. The LUMO-HOMO energy gap of IOMBT shows that the energy gap reflects the chemical reactivity and the level of conductivity of the molecule.

Structure and vibrational spectra of 6-(4-fluorobenzoyl)-3-(2-(4-methylpiperazin-1-yl)-2-oxoethyl)benzo[d]thiazol-2(3H)-one molecule.

The molecular structure, conformational stability and vibrational frequencies of 6-(4-fluorobenzoyl)-3-(2-(4-methylpiperazin-1-yl)-2-oxoethyl)benzo[d]thiazol-2(3H)-one (abbreviated as FMOT) molecule in the ground state were calculated by DFT (B3LYP) and HF methods using different basis sets. The solid-state FT-IR spectrum was measured and compared with calculated values. FMOT was found to have four different stable conformations. The comparison of the theoretical and experimental geometries of the title compound indicated that the X-ray parameters fairly well agree with the theoretically obtained values for the most stable conformer. Energy gap of the molecule was found using HOMO and LUMO calculation, hence the less band gap, which seems to be more stable. The observed and calculated vibrational frequencies are found to be in good agreement.

Ab initio Hartree-Fock and density functional theory investigations on the conformational stability, molecular structure and vibrational spectra of 5-chloro-3-(2-(4-methylpiperazin-1-yl)-2-oxoethyl)benzo[d]thiazol-2(3H)-one drug molecule.

In this work, the experimental and theoretical spectra of 5-chloro-3-(2-(4-methylpiperazin-1-yl)-2-oxoethyl)benzo[d]thiazol-2(3H)-one molecule (abbreviated as 5CMOT) are studied. The molecular geometry and vibrational frequencies are calculated in the ground state of molecule using ab initio Hartree-Fock (HF) and Density Function Theory (DFT) methods with 6-311++G(d,p), 6-31G++(d,p), 6-31G(d,p), 6-31G(d) and 6-31G basis sets. Three staggered stable conformers were observed on the torsional potential energy surfaces. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes calculated. The comparison of the theoretical and experimental geometries of the title compound indicated that the X-ray parameters fairly well agree with the theoretically obtained values for the most stable conformer. The theoretical results showed an excellent agreement with the experimental values. The calculated HOMO and LUMO energies show that the charge transfer occurs within the molecule.

Studies on the electronic absorption spectra of some monoazo derivatives.

The electronic absorption spectra of a series of azo dye compounds containing -Cl, -SO3H and -OH groups were recorded in twenty one solvents with different polarities. The solvents were selected to cover a wide range of parameters (refractive index, dielectric constant and hydrogen bonding ability). Solvent-induced effect on the maximum absorption band frequencies of azo dye compounds are described in terms of solute-solvent interactions. Multiple linear regression equation for νmax was performed using polarizability-polarity parameters and Kamlet-Taft solvatochromic parameters. The results help to assign the solvent-solute interactions and the solvatochromic potential of the investigated compounds. It is concluded that the electronic of the substituent and hydrogen bonding acceptor ability of the solvents are the major factors to the interaction in solutions.

Experimental and density functional theory and ab initio Hartree-Fock study on the vibrational spectra of 5-chloro-6-(4-chlorobenzoyl)-2-benzothiazolinone molecule.

The vibrational frequencies and infrared intensities of 5-chloro-6-(4-chlorobenzoyl)-2-benzothiazolinone (abbreviated as CCB) molecule in the ground state were calculated by HF and DFT (B3LYP and BLYP) methods using different basis sets to elucidate the molecular structure. The solid-state FT-IR spectrum was measured and compared with calculated values. CCB was found to have two different stable conformations. The dihedral angles alpha and beta (i.e. C9-C8-C12-C18 and C8-C12-C18-C17, respectively) were computed as -59.6 degrees and -14.5 degrees for the most stable conformer. The comparison of the theoretical and experimental geometries of the title compound indicated that the X-ray parameters fairly well agree with the theoretically obtained values for the most stable conformer. The calculated vibrational frequencies are also in good agreement with the experimental results.

FTIR spectroscopic and theoretical study of the photochemistry of matrix-isolated coumarin.

The infrared spectrum of monomeric unsubstituted coumarin (C9H6O2; 2H-1-benzopyran-2-one), isolated in solid argon at 10 K is presented and assigned. The UV-induced (lambda>200 nm) unimolecular photochemistry of the matrix-isolated compound was studied experimentally. Three main photoreactions were observed: (a) decarboxylation of the compound and formation of benzocyclobutadiene and CO2, with the Dewar form of coumarin as intermediate; (b) isomerization of the compound, leading to production of a conjugated ketene; and (c) decarbonylation, leading to formation of CO and benzofuran complex. Further decomposition of benzofuran to produce ethynol is suggested. Photochannels (a) and (b) correspond to those previously observed for matrix-isolated alpha-pyrone and its sulfur analogs (Phys. Chem. Chem. Phys. 2004, 6, 929; J. Phys. Chem. A 2006, 110, 6415), while route (c) is similar to the UV-induced photochemistry of coumarin in the gaseous phase (J. Phys. Chem. A 2000, 104, 1095). Interpretation of the experimental data is supported by extensive calculations performed at the B3LYP/6-311++G(d,p), MP2/6-31G(d,p) and MP2/6-311++G(d,p) levels.