Geometry optimizations of all cluster models were carried out in solution with Integral Equation Formalism Polarizable Continuum Model (IEFPCM) as implemented in Gaussian09. The B3LYP functional in conjunction with the 6-31+g(d) basis set was employed to optimize the geometries. Frequency calculations at the same level of theory were carried out to verify the nature of the stationary points enc...

Electronic circular dichroism (ECD) parameters of the disulphide chromophore have been calculated for dihydrogen disulphide, dimethyl disulphide, and cystine using density-functional theory, coupled-cluster theory, and multiconfigurational self-consistent field theory. The objective is twofold: first, to examine the performance of the Coulomb-attenuated CAM-B3LYP functional for the calculation ...

Formamide harmonic and anharmonic frequencies of fundamental vibrations in the gas phase and in several solvents were successfully estimated in the B3LYP Kohn-Sham complete basis set limit (KS CBS). CBS results were obtained by extrapolating a power function (two-parameter formula) to the results calculated with polarization-consistent basis sets. Anharmonic corrections using the second order p...

Fourier transform Raman and infrared spectra of 4-hydroxy-2,6-dimethyl pyrimidine (HDMP) were recorded and interpreted by comparison with respective theoretical spectra calculated using HF and B3LYP methods. The HDMP equilibrium geometry with Cs symmetry, harmonic vibrational frequencies, infrared and Raman intensities were determined using HF/6-311G and B3LYP/6-311G level of theories. The band...

Ab initio molecular orbital calculations on the interaction between Copper(I) and 5-nitrotetrazolate anion were done using different basis sets, at the HF, B3LYP and MP2 levels of theory. Three minima were found to 1A, 1B and IC structures of Cu(I)-5-NTz complex. At the B3LYP/LanL2DZ level, the energy difference between 1A and 1B was computed to be 8.18 kcal/mol, while that between 1A and 1C is...

The specific optical rotation of (S)-fluoro-oxirane in gas phase and solution is predicted using time-dependent density functional theory (B3LYP functional) and coupled cluster linear response theory. Upon vibrational averaging, the coupled cluster singles and doubles model predicts the gas phase specific optical rotation to be 8.1 degrees (dm g/cm(3))(-1) at 355 nm at room temperature. This is...

Tripeptide Tyr-Aaa-Gly (1a, 2b) is methionine-enkephalin analogues [Aaa = (R,S)-(1adamantyl)glycine]. The unique structure of adamantane is reflected in its highly unusual physical and chemical properties, which can have many applications including drug design and drug delivery. In this research, Quantum-mechanical calculations were performed at the HF/6-31G, HF/6-31G*, B3LYP/6-31G, B3LYP/6-31+...

Employing introductory (3-21G RHF) and medium-size (6-311++G∗∗ B3LYP) ab initio calculations, complete conformational libraries, containing as many as 27 conformers, have been determined for diamide model systems incorporating the amino acids valine (Val) and phenylalanine (Phe). Conformational and energetic properties of these libraries were analyzed. For example, significant correlation was f...