Ž . ABSTRACT: Density Functional Theory DFT calculations at the B3LYPr631G level have been performed on four bowl-shaped polyaromatic Ž . Ž . Ž . hydrocarbons of C H molecular formula 1]4 showing C 1 , C 2 and 4 , 30 12 3 2 v Ž . and C 3 symmetries. The geometrical and electronic properties of the 2 h compounds studied have been analyzed to explain their relative stability. NMR chemical shifts ...

Recent ab initio calculations of cobalt NMR shielding show that DFT-GIAO calculations using hybrid functionals are found to reproduce experimental values well. This method is used to calculate the variation of the cobalt NMR shielding tensor of sqaure pyramidal nitrosyl complexes with respect to the CoNO geometry and to differing basal ligands. The isotropic shielding is shown to have a large n...

The structural parameters and energies of the protonated compounds c/o5o-[B6H5HtacF]and c/o5o-[B6H5HtacCH3]_ are calculated by MP2/6-31G* optimization, as have the ’H, "B , 13C and i9F NMR shifts using a tzp basis set and the RHF/GIAO method. The results for the octahedral molecule anions confirm the preferred localization of the additional proton in [B6H5HtacX]~ in case of X = CH3 at the upper...

Compound (N,N-bis (salicylidene) 1,2-diaminophenylene) was prepared by condensation of ethanolsolution of 2-Hydroxybanzaldehyde and 1,2-diaminophenylene. The compound was characterized by1H NMR, infrared spectroscopy (FT-IR) data and analytical data. The geometrical parameters andenergies have been obtained from Density Functional Theory (DFT) B3LYP method and Hartree-Fock (HF) method with 3-21...

UNLABELLED BACKGROUND Chalcones are ubiquitous natural compounds with a wide variety of reported biological activities, including antitumoral, antiviral and antimicrobial effects. Furthermore, chalcones are being studied for its potential use in organic electroluminescent devices; therefore the description of their spectroscopic properties is important to elucidate the structure of these mol...

Ring formation in phosphate systems is expected to influence both the magnitude and orientation of the phosphorus (P) nuclear magnetic resonance (NMR) chemical shielding anisotropy (CSA) tensor. Ab initio calculations of the P CSA tensor in both cyclic and acyclic phosphate clusters were performed as a function of the number of phosphate tetrahedral in the system. The calculation of the P CSA t...

Hydrazide-Hydrazone compounds are key species for a range of bioactivities. The first complete density functional theoretical study of Phenoxyacetohydrazide (PAH) is reported. The normal mode frequencies, intensities and the corresponding vibrational assignments were calculated using the GAUSSIAN 09W set of quantum chemistry codes at the DFT/B3LYP levels of theory using the 6-311++G** basis set...

Nuclear magnetic shielding tensors computed by the gauge including atomic orbital ~GIAO! method in the Hartree–Fock self-consistent-field ~HF-SCF! framework are partitioned into magnetic contributions from chemical bonds and lone pairs by means of natural chemical shielding ~NCS! analysis, an extension of natural bond orbital ~NBO! analysis. NCS analysis complements the description provided by ...

The H and C Nuclear Magnetic Resonance (NMR) spectra of the retinyl chromophore in rhodopsin are investigated by using Quantum Mechanics/Molecular Mechanics (QM/MM) hybrid methods at the Density Functional Theory (DFT) B3LYP/631G*:Amber level, in conjunction with the Gauge Independent Atomic Orbital (GIAO) method for the ab initio Self-Consistent-Field (SCF) calculation of NMR chemical shifts. ...