No abstract

The optimized structures of all isomers of HBI, HBO, HBT, HPyBI, HPyBO, and HPyBT compounds were obtained using the potential energy surface method at the B3LYP/6-311??G(d,p) level of theory. Four isomers and three transition states of their transformations for each compound of HBO, HBT, HPyBO, and HPyBT and two isomers and one transition state for each HBI and HPyBI compounds were found. Energetics, thermodynamic properties, rate constants, and equilibrium constants of their transformations were determined.

No abstract

A comparative study of the Zn(2+) and Cu(2+) complexation with thiacalix[4]arene is presented using density functional theory methods. The structures and energetics of the possible binding modes of both metal complexes are investigated in detail. Two types of patterns were found in the second deprotonated species, adjacent or opposite phenolate groups, which determine the stability of the different binding modes. The most stable structure for both metal ions was predicted to be a distorted square planar coordination at lower rim with opposite phenolate groups, which has never been referred to in the literature. The results show a higher complexation ability of Cu(2+) than Zn(2+) for all of the binding modes, which is in good agreement with the previous study on liquid-liquid extraction experiments. The analysis of the electrostatic potential surfaces of the metal complexes allows us to conclude that the different complexation features can also be explained by a bigger charge transfer from the metal to the coordinated atoms in the case of the Cu(2+) complex.