Motivated by the use of chitosan (Ch), and cellulose acetate (AC) as organic matrices in several therapeutic drugs, a theoretical study has been elaborated through density functional theory method (DFT) to investigate interaction mechanism between two essential ions for human body Ca2+, K+ (AC). Many physical chemical aspects have carried out after achievement structural optimization. This invo...

The recent synthesis of a crystalline compound containing Ti bonded to cyclopentadienyl and a substituted dienyl fragment prompted the question of whether Ti-C contacts that were found to be shorter than other such bonded contacts in the same molecule should be considered as short nonbonded contacts or "nonclassical metal-to-saturated-carbon atom interactions", fitting the description of agosti...

a quantum chemical investigation was carried out to study the properties of intermolecular f•••f, br•••br and br•••o interactions in crystalline 1-bromo-2,3,5,6-tetrafluoro-nitrobenzene (bfnb). this system was selected to mimic the halogen-halogen as well as halogen bonding interactions found within crystal structures as well as within biological systems. we found that fluorine atoms have weak ...

the influence of cation-π interactions on the strength and nature of intramolecular o...h hydrogen bond has been investigated by quantum chemical calculations in orthohydroxy benzaldehyde (hba) compound. ab initio calculations have been performed at mp2/6-311++g** level of theory. vibrational frequencies and physical properties such as chemical potential and chemical hardness of these compounds...

The nature of the E-E' bonds (E, E' = S and Se) in glutathione disulfide (1) and derivatives 2-3, respectively, was elucidated by applying quantum theory of atoms-in-molecules (QTAIM) dual functional analysis (QTAIM-DFA), to clarify the basic contribution of E-E' in the biological redox process, such as the glutathione peroxidase process. Five most stable conformers a-e were obtained, after app...

The conformational preferences of benznidazole were examined through the application of DFT, PCM and QTAIM calculations, whose results were compared with crystallography data. The geometries were fully optimized with minimum potential energy surface by means of the Relaxed Potential Energy Surface Scan (RPESS) at AM1, followed by the B3LYP/6-311++G(d,p) theoretical level. As a result, the s-cis...

We show that the use of the quantum theory of atoms in molecules (QTAIM) in electronically excited states allows expanding the knowledge that the molecular orbital (MO) framework provides about electronic rearrangements. Despite that historical prejudice seemed to preclude the use of QTAIM beyond the electronic ground state, this paper evidences that QTAIM is versatile enough to deal with excit...

A theoretical study of the structural and electronic properties of the chloride ion and water molecules in the first hydration shell is presented. The calculations are performed on an ensemble of configurations obtained from molecular dynamics simulations of a single chloride ion in bulk water. The simulations utilize the polarizable AMOEBA force field for trajectory generation and MP2-level ca...

Vibrational modes ascribed to the stretching of X-H bonds from donor monomers (HXdonor) in complexes presenting hydrogen bonds (HF···HF, HCl···HCl, HCN···HCN, HNC···HNC, HCN···HF, HF···HCl and H2O···HF) exhibit large (4 to 7 times) infrared intensity increments during complexation according to CCSD/cc-pVQZ-mod calculations. These intensity increases are explained by the charge-charge flux-dipol...