Search

The efficiency of the designed dye-sensitized solar cells (DSSCs) containing phenothiazine phenoxazine, and 5,10-dimethylphenazine as donors and triazine, phenyl with D-A'-(π-A) 2 architecture has been examined utilizing Time-dependent (TD-DFT) and Density Functional Theory (DFT) techniques. The geometrical structures, electrical characteristics, absorption, and photovoltaic characteristics were studied using these techniques. Additionally, the computed findings show that various layouts can alter the HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) energy levels and reduce the energy gap between 1.63 and 2.30 eV. The absorption undergoes a redshift displacement. These bands are between 300 and 400 nm. This work aims at calculating the structural geometries and the electronic and optical properties of the designed dyes. In order to shed light on the bridging influence on geometric and TD-BHandH/6-31G(d) for optoelectronic properties, the density functional theory (DFT) and time-dependent TD-DFT at the B3LYP/6-31G(d) level were examined. Additionally, the complex dye@TiO2 cluster's binding energies have been investigated. [ABSTRACT FROM AUTHOR]

Abstract: In this study, nano-sized powder of cerium (IV) oxide was prepared through the thermal decomposition reaction of Ce2(C2O4)3⋅10H2O. The thermal decomposition course was followed using differential thermal analysis–thermogravimetry (DTA–TG) techniques. Kinetic analysis of the dynamic TG curves was carried out, to obtain kinetic parameters for the decomposition of cerium oxalate into ceria, using three integral methods: Ozawa, Coats–Redfern, and Diefallah composite method. The produced ceria as well as calcined samples at different temperatures up to 950°C were characterized using X-ray diffraction (XRD), Fourier transform infra-red (FT-IR) and transmission electron microscopy (TEM) techniques. The change in the structural and morphological properties with heat treatment was studied. Surface area measurement was carried out for the calcined samples at different temperatures to characterize the surface properties of the investigated samples. Electrical property as a function of temperature and frequency was measured to determine the conductivity as well as the conduction activation energy and to describe the conduction mechanism. The density functional theory (DFT) was used to describe the chemical bonding characteristics of the prepared compound. The obtained results were discussed to show the effect of heat treatment on the structural, morphological, superficial and electrical properties of ceria. [Copyright &y& Elsevier]

Abstract: N-Bromosuccinimide (NBS) is a brominating and oxidizing agent that is used as a source of bromine. The proton affinities, the tautomeric forms and Nissociation of NBS have been computed using the B3LYP functional as implemented in the density functional approach. The electronic structures of all possible tautomeric forms of NBS have been thoroughly investigated. The keto form of NBS has been shown to be more stable than any other tautomeric forms. The geometries and relative energies for various stationary structures were determined. The results indicate clearly that O-site protonation is strongly favored over N-site protonation for the studied compound in case of mono- and di-protonation. The bond dissociation energies (BDEs), involving the formation of the bromine radical, cation, and anion, of the Nave been investigated. The N the Br radical formation is lower than that of the Br anion or cation. These conclusions are in good agreement with the experimental results. [Copyright &y& Elsevier]

Abstract: The optimized geometries and energies of the four cyclic structures of the orotic acid–water complex are computed using density functional theory (B3LYP) combined with the 6-31++G(d,p) basis set. In the three most stable cyclic structures, the water molecule accepts the NH proton and donates a proton to the carbonyl oxygen atoms. Less stable cyclic complexes involving the C5H bond also formed. The proton affinity of the oxygen atoms and the deprotonation enthalpy of the NH bonds of orotic acid are computed at the same level and compared with reported data on uracil and thymine. The most stable cyclic complex is formed at the oxygen lone pair characterized by the lowest basicity and at the NH bond characterized by the highest acidity. Although intrinsic acidities are lower in orotic acid than in uracil and thymine, the binding energies with one water molecule do not differ markedly for uracil and orotic acid. Substituent of carboxylic group at the 6-position, however do not seem to have much effect on the proton affinities and the deprotonation enthalpy of uracil. [Copyright &y& Elsevier]

A density functional theory study of the behavior of hemispherands toward alkali metal ions (Li+, Na+, and K+) is performed. The effect of the replacement of the rigid anisyl group(s) by the mobile ether group(s) on the binding energy of hemispherands with alkali metal ions is investigated. The results indicated that the binding energies are inversely proportional to the ionic radius of the cations. Moreover, increasing the flexibility of the ligand results in decreasing the binding toward small ions. The structures of the hosts and the guests are correlated to the binding energies, and the correlations are interpreted in terms of the principle of preorganization. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [ABSTRACT FROM AUTHOR]

Abstract: The complexes of orotic acid with Co(II), Ni(II), Fe(III), Cu(II), and Cd(II) were prepared and their stoichiometry were determined by elemental analysis. Co(II) and Ni(II) give complexes with orotic acid of 1:1 ratio whereas that of the remaining transition metals give complexes of 1:2 ratio. The stereochemistry of the studied metal complexes has been established by analyses of their electronic spectra and magnetic susceptibilities. The mode of bonding in the studied series of metal complexes was established via, analysis of their infrared spectra. The present analysis leads to the conclusion that all metal ions studied coordinate to orotic acid via N1 and the adjacent carboxylate group. Thermal decomposition studies of orotic acid complexes have been carried out as to understand the status of water molecules present in these complexes as well as to know their general decomposition pattern. Theoretical investigation of the electronic structure of the studied metal complexes has been carried out. MO computations at the HF-level were performed. Charge density distribution, extent of distortion from regular geometry, dipole moment, and orientation were computed and discussed. [Copyright &y& Elsevier]

Abstract: Ab initio molecular orbital computation has been performed to study the electronic structure, substituent and solvent effects on the singlet–triplet gaps of a series of nitrenium ions. DFT calculations at the B3LYP/6-311++G** level of theory predict that, the nitrenium ions derived from the metabolism of the antitumor 2-(4-aminophenyl)benzothiazoles exist in the ground singlet state. The preferential stabilization of the singlet state relative to the triplet is due to the transfer of charge density from the phenyl ring to formally electron deficient nitrogen atom. Calculations in solution were carried out using the PCM model. Solvent–solute interaction energies were estimated and reflect a considerable net stabilization of the triplet species at the PCM model. Fourier transform analysis of the internal rotation potential energy function, around the exocyclic bond (C4–N), has been performed for niternium ions studied. The magnitudes and origin of the potential energy barriers have been discussed. [Copyright &y& Elsevier]

The molecular geometry of orotic acid was fully optimized using the gradient minimization technique. The computed geometrical parameters at the B3LYP/6-311G** level correspond well to those determined experimentally by X-ray diffraction.The relative stability of both the syn and anti conformations was investigated at the B3LYP/6-311G** level, where the syn-form was shown to be slightly more stable by 1.58 kcal/mol. The barrier to internal rotation about the C6–C12 bond was computed and this low barrier (7.655 kcal/mol) was shown to be associated with the θ=90° conformation. The results of the present work indicate that orotic acid behaves as a free rotor in the C6–C12 bond region and both the syn- and anti conformations were equally probable. Fourier analysis of the internal rotation function was carried out. The results indicate that the stability of the syn- over the anti-form was not due to increased or tight conjugative interaction, but rather due to decreased dipole–dipole repulsion and bond moment''s interactions that is of electrostatic nature. The electronic structures of all possible tautomeric forms of orotic acid and that of its zwitterion have been thoroughly investigated. Equilibrium geometries were determined and compared to that of orotic acid. Solvent effects were taken in consideration. The self-consistent reaction field model (SCRF) was adopted to estimate gross solvent effects. The keto-form of orotic acid has been shown to be more stable than any other tautomeric forms. [Copyright &y& Elsevier]

Microwave assisted condensation of 3-acetyl-2,5-dimethylthiophene (1) and 9-ethyl-9 H -carbazole-3-carbaldehyde (2) gave 1-(2,5-Dimethylthiophen-3-yl)-3-(9-ethyl-9 H -carbazol-3-yl)prop-2-en-1-one (chalcone) (1.1) which was cyclized to pyrazoline (1.2, 1.3), and pyrimidine (1.4, 1.5) derivatives. All the synthesized compounds were subjected to antibacterial activity evaluation using two Gram + ve and two Gram-ve bacterial strains and were tested for any possible toxic effect to the mammalian cells. Density functional theory was used to understand the electronic structure of the studied molecules. All the molecules were modeled and optimized using B3LYP/6-311 + G** level of theory. The relationship between activities and Frontier Molecular orbital (HOMO and LUMO orbitals) of the compounds is also discussed. Docking studies were also performed. The observed results revealed that the pyrazoline skeleton is a promising lead structure, which displays higher in vitro antibacterial efficacy, probably by interacting and inhibiting the glucosamine-6-phosphate synthetase enzyme (GlmS). Theoretical calculations are in good agreement with the in vitro and in silico findings. Image 1 • Microwave assisted synthesis of chalcone and its polycyclic heterocyclic analogues. • The structural details were elucidated by spectroscopic techniques. • In vitro , in silico and DFT studies of the polycyclic heterocyclic compounds. • Compounds showed promising broad spectrum antibacterial activity. [ABSTRACT FROM AUTHOR]