Synthesis and characterization of complexes of Fe(III), Co(III), Ni(II), Cu(II), Zn(II) and UO₂²⁺ with p-tert-butylcalix[4]arene bearing two imine pendants linked through salicylyl moiety at the lower rim

Abstract

Metal ion complexes of the double-armed p-tert-butylcalix[4]arene derivative possessing imine functionality linked through salicylyl moiety  at the lower rim has been synthesized for the first time and characterized by analytical, spectral and magnetic methods. The 1, 3- di-calix[4]arene-imine conjugate exhibits variable coordination behavior, from tetradentate to hexadentate, depending upon the metal ion to which it is bound, by always acting as di-anionic. While it uses both the ether oxygens of the pendants to coordinate in the case of Fe(III), Co(III) and Ni(II) complexes, it uses only the pendant salicylidene moieties in the case of Cu(II) and Zn(II) complexes. The Zn(II) complex catalysis ester hydrolysis through the formation of Zn(II)-hydroxo species.