Conformational structures, proton affinity of p- tert-butylthiacalix[4]arene and its zinc complex

Abstract

The conformational optimizations were performed on p- tert-butylthiacalix[4]arene and thiacalix[4]arene using the potential energy scan and semi-empirical AM1 methods. The relative energies for all conformations were obtained with the HF/6-31G*//AM1 and B3LYP/6-31G*//AM1 methods. The relative stabilities of the most stable conformation of p- tert-butylthiacalix[4]arene conformers are in the following order: cone>partial cone>1,2-alternate>1,3-alternate. The energy difference between the two most stable conformers of p- tert-butylthiacalix[4]arene (cone 0000-AAAA and partial cone 0001-AAAA) is 9.05 kcal/mol. The reaction energies of proton affinity, deprotonation, preorganization of p- tert-butylthiacalix[4]arene cone conformer and complexation of its zinc complex were obtained with the B3LYP/6-31G* calculations. Both AM1 and B3LYP/6-31G* optimized geometries of p- tert-butylthiacalix[4]arene cone conformer show good agreement with the X-ray crystallographic data. Electrostatic potential surfaces for LH 4, LH 3 − and LH 2 2 − species of p- tert-butylthiacalix[4]arene (LH 4) cone conformer are reported.