Low-Temperature Infrared Spectra and Ultraviolet-Induced Rotamerization of 5-Chlorosalicylaldehyde.

5-Chlorosalicylaldehyde (abbreviated as 5CSA) is an important chemical used in the synthesis of fragrances, dyes, and pharmaceuticals. In this investigation, 5CSA isolated in solid N, at 10 K, and in its neat amorphous and crystalline phases, at 50 and 190 K, respectively, were investigated by infrared spectroscopy and DFT(B3LYP)/6-311++G(d,p) calculations. The systematic theoretical analysis of the 5CSA conformational landscape showed that the compound exhibits four different conformers, which were structurally characterized in detail.

UV-induced -OCH rotamerization in a matrix-isolated methoxy-substituted ortho-hydroxyaryl Schiff base.

A new methoxy-substituted ortho-hydroxyaryl Schiff base, 4-(3-methoxy-2-hydroxybenzylidene-amino) phenol was synthesized from 4-aminophenol and 2-hydroxy-3-methoxybenzaldehyde in methanol solution and characterized by H-NMR, C-NMR and infrared spectroscopies and elemental analysis. The compound was isolated in a cryogenic (10 K) argon matrix, and the analysis of the infrared spectrum of the matrix-isolated compound revealed that it corresponds to the E-enol-imine isomeric form, with 3 different conformers being present in the matrix. These conformers share as common structural features the conformation of the free hydroxyl group (trans relatively to the para-substituent of the ring) and the presence of an OHN intramolecular H-bond involving the methoxy-substituted phenol ring and the azomethine bridge, while they differ in the orientation of the methoxy-substituent group.

Theoretical investigation on π-spacer effect of the D-π-A organic dyes for dye-sensitized solar cell applications: a DFT and TD-BHandH study.

In this paper, we present a series of sensitizers to shed light on the influence of π-spacers on the performance of dye-sensitized solar cells. We have accurately calculated key properties in energy conversion, including sunlight absorption, electron injection, electron/hole reorganization energy, ionization potential (IP) and electronic affinity (EA). We chose a series of donor-π-acceptor dyes based on methyl-indole-carbazole as the electron donor group and cyano-acrylic acid as an acceptor with various π-conjugated systems.

Estimation of ground and excited state dipole moments of Oil Red O by solvatochromic shift methods.

Absorption and fluorescence spectra of Oil Red O (abbreviated as ORO) are recorded in various solvents with different polarity in the range of 250-900 nm, at room temperature. The solvatochromic shift methods have been used to determine the ground state (μg) and excited state (μe) dipole moments depending on dielectric constant and refractive index functions. It is observed that fluorescence spectra show positive solvatochromism whereas absorption spectra do not indicates sensitive behavior to solvent polarity.

Acidity constant determination of novel drug precursor benzothiazolon derivatives including acyl and piperazine moieties.

In this study, protonation and deprotonation behaviors of eight new drug precursor benzothiazolon derivatives in all of acidic and basic scale (super acidic, pH, super basic regions) are analyzed by using UV-visible spectrophotometric technique. Acidity constants (pKa), elucidation of the structure and protonation mechanisms of the studied molecules are obtained. Substituent effect on acidity constant values is discussed.

Solvent effect on the absorption and fluorescence spectra of 7-acetoxy-6-(2,3-dibromopropyl)-4,8-dimethylcoumarin: determination of ground and excited state dipole moments.

The ground state (μ(g)) and excited state (μ(e)) dipole moments of 7-acetoxy-6-(2,3-dibromopropyl)-4,8-dimethylcoumarin (abbreviated as 7ADDC) are estimated from solvatochromic shifts of absorption and fluorescence spectra as a function of the dielectric constant (ε) and refractive index (n). While the ground state dipole moment is determined by using Bilot-Kawski method, the excited state dipole moment is calculated by using Bilot-Kawski, Lippert-Mataga, Bakhshiev, Kawski-Chamma-Viallet and Reichardt correlation methods. Excited state dipole moment is observed as larger than the ground state dipole moment due to substantial π-electron density redistribution.

Dechlorination of chlorinated compounds by Trametes versicolor ATCC 200801 crude laccase and quantitative structure-activity relationship of toxicity.

Chlorinated compounds constitute an important class of xenobiotics. Crude laccase was produced using Trametes versicolor ATCC (200801) in potato dextrose broth, with wheat bran as an inducing medium, and its ability to dechlorinate eight compounds was determined. The compounds were 2-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, 2,6-dichlorophenol, 2,4,5-trichlorophenol, 2,4,6-trichlorophenol, heptachlor and pentachlorophenol.

Conformational stability, the spectroscopic (FT-IR and UV), first order hyperpolarizability, NBO analysis, HOMO and LUMO analysis of 6,8-diphenylimidazo[1,2-α]pyrazine molecule by ab initio HF and density functional methods.

The conformational analysis of 6,8-diphenylimidazo[1,2-α]pyrazine molecule (abbreviated as 68DIP) was performed by using B3LYP/6-31G(d) level of theory to find the most stable form. Two staggered stable conformers were observed on the torsional potential energy surface. The equilibrium geometry, bonding features and vibrational frequencies of 68DIP have been investigated by using the DFT (B3LYP) and HF methods for the lowest energy conformer.

Ground state and excited state dipole moments of 6,8-diphenylimidazo[1,2-α]pyrazine determined from solvatochromic shifts of absorption and fluorescence spectra.

Electronic absorption and dual fluorescence spectra of 6,8-diphenylimidazo[1,2-α]pyrazine (68DIP) was recorded in various solvents with different polarity at room temperature. The ground state (μg) and the excited state (μg) dipole moments of 68DIP were estimated from solvatochromic shifts of absorption and fluorescence spectra as a function of the dielectric constant (ɛ) and refractive index (n). The results show that the value of excited state dipole moment in SE: μeSE=2.

Spectroscopic determination of acid dissociation constants of N-substituted-6-acylbenzothiazolone derivatives.

The acid dissociation constants of twelve novel drug precursor N-substituted-6-acylbenzothiazolone derivatives were determined by using the UV-vis spectroscopic technique. The protonation and deprotonation behaviors of the investigated molecules were researched from the super basic to super acid regions (i.e.

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.

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.