The molecular orbital calculations have been carried out to investigate the structure and stability of (E) / (Z) isomers of some azobenzene derivatives containing maleimide groups. A special attention has been devoted to the compound (E)-1, (E)-1-(4-(phenyldiazenyl)phenyl)-1H-pyrrole-2,5-dione, for which the available crystallographic experimental data have been used to validate the modeling st...

Semi-empirical (AM1) electronic structure calculations are reported on a pH-switchable [2] rotaxane whose synthesis was reported in [Angew. Chem. Int. Ed., 36 (1997) 1904]. The [2] rotaxane possesses two cationic binding sites, with different affinities toward dibenzo [24] crown-8 (the ring component of the [2] rotaxane) depending upon the pH of the system. The computational results capture thi...

In this work we propose the synthesis of thiazolidine and bisthiazolidine derivatives, and the structure of these compounds were studied using elemental analysis, IR, H-NMR and C-NMR spectroscopy. Tautomeric properties and conformations were investigated by semi-empirical AM1, MNDO and PM3, and ab initio calculations to illustrate the conformational analysis. All calculations lead to the same r...

The article presents extended computer investigations of various sulfate derivatives of riboflavin. A number of physicochemical parameters such as total energy, binding energy and formation heat were calculated via semi-empirical methods AM1 and PM3 for the different derivatives of riboflavin. Their analysis made it possible to determine the sequence of formation of sulfate derivatives--esterif...

In this paper we investigate (using AM1 semi-empirical as well as HF methods at the STO-3G, 3-21G, 6-31G, 6-31G* and 6-31+G** level) the conformations, geometrical parameters, Mulliken charges, and solvation effects of the triphosphate form of AZT (AZTTP), as well as the thymidine nucleotide (dTTP) structure. Our calculated geometrical parameters and Mulliken charges, with and without solvation...

A number of physicochemical parameters were calculated via semi-empirical methods AM1 and PM3 for the molecule of riboflavin at various protonation states. Their analysis made it possible to determine the acidicity of appropriate groups of this compound. The sequence of protons dissociation and accepting by the neutral molecule of riboflavin was determined. This methodology may be used to study...

Objective(s): The structure- activity relationship of a series of 36 molecules, showing L-type calcium channel blocking was studied using a QSAR (quantitative structure–activity relationship) method. Materials and Methods: Structures were optimized by the semi-empirical AM1 quantum-chemical method which was also used to find structure-calcium channel blocking activity trends. Several types of ...

L-phenylalanine (Phe), an essential amino acid, is necessary for the synthesis of proteins such as catecholamine and melanin, also precursor acid L-tyrosine (Tyr). In this paper, optimized structures Phe, were calculated by using semi-empirical models AM1, PM3 MNDO; Density Functional (DFT) at B3LYP Hartreefock methods (HF) with 6-311++G (d,p) level. The energies geometric parameters Kaempferol...

A common practice to compute ligand conformations of compounds with various degrees of freedom to be used in molecular modeling (QSAR and docking studies) is to perform a conformational distribution based on repeated random sampling, such as Monte-Carlo methods. Further calculations are often required. This short review describes some methods used for conformational analysis and the implication...