Basicity of triaza benzo crown-p-tert-butylcalix [4] arene and stability of its metal complexes in methanol

Abstract

Basicity study of 25,27-{2,2'-[2,2'-((2,5,8 triaza)nonyl)diphenoxy]diethyl}-p-tert-butylcalix[4]arene (L) and stability of its complexes with transition metal ions (M2+), including Co2+, Ni2+, Cu2+ and Zn2+ were investigated at 25°c by potentiometric titration method. Three protonation constants of the ligand L, in the methanolic solution of 5.0 x 10-2 M Et4NCIO4 and 5.0 X 10-2 M BU4NCF3SO3 were obtained. The three protonation constants in the methanolic solution of 5.0 X 10-2 M Et4NCIO4 were larger than those in the methanolic solution of 5.0 x 10-2 M BU4NCF3SO3. The order of magnitude of the stability of the ligand L complexes with the Co2-, Ni2+, Cu2+ and Zn2+ in the methanolic solution of 5.0 x 10-2 M BU4NCF3SO3 found as ML2+ species, decreases from Cu2+ > Ni2+ > CO2+ > Zn2+. The complex species with the Cu2+ and Zn2+ were formed as CuL(OCH3)+ and Zn2L4+ respectively.