pH-driven variation of the outer-sphere binding mode of cis-[Co(Ad)(en)2Cl]Cl (en-ethylendiamine, ad-adeninate) with p-sulfonatothiacalix[4]arene

Abstract

The non-symmetrical cobalt (III) complex cis-[Co(Ad)(en)2Cl]Cl (1Cl), possessing two flexible ethylendiaminate chelate rings (en) and monodentate N(9)-bound adeninate (Ad-) was chosen as the guest of p-sulfonatothiacalix[4]arene (STCA) to study the inclusion complex formation at wide range of pH 2-10. It was shown by 1H, NOE NMR methods and pH-metric procedure, that pH-driven variation of the inclusion mode of 1 + into calixarene cavity is the result of the protonation of 1 + via adeninate moiety. © 2006 Springer Science+Business Media, Inc.