Investigation of basicity of Calix[4]-Cyclen-Benzo-Crown-6 and stability of its complexes with metal ions by potentiometric method

Abstract

Protonation constants of calix[4]-cyclen-benzo-crown-6, L in 1 x 10[superscript -2] M Bu[subscript 4]NCF[subscript 3]SO[subscript 3] in 40% CH[subscript 2]Cl[subscript 2]/CH[subscript 3]OH at 25 ํC determined by potentiometric titration are log K[subscript 1] = 10.91+-0.13, log K[subscript 2] = 10.30+-0.25, log K[subscript 3] = 6.24+-0.26 and log K[subscript 4] = 2.55+-0.28. Stability constants for the ligand L complexes with Cu(II) and Zn(II) in 1 x 10[superscript 2]M Bu[subscript 4]NCF[subscript 3]SO[subscript 3] in 40% CH[subscript 2]Cl[subscript 2]/CH[subscript 3]OH at 25 ํC were determined by UV-VIS spectrophotometric titration. The stability constants of the Cu(II)/L and Zn(II)/L complexes as log beta are 4.37 and 3.45, respectively. Stabilization energies for protonations of the ligand L form the calculation by ab initio Harthree-Fock with 6-31G basis set are delta E[subscript 1] = -290.1 kcal/mol, delta E[subscript 2] = -205.0 kcal/mol, delta E[subscript 3] = -124.9 kcal/mol and delta E[subscript 4] = -26.9 kcal/mol and complexation energies of Zn(II) complexes with ligand L are -370.3 kcal/mol.