Complexes of Schiff base of gossypol with 5-hydroxy-3-oxapentylamine and Ca 2+, Ba 2+ or Pb 2+ cations studied by NMR, FT-IR, ESI MS as well as PM5 semiempirical methods

Abstract

A new Schiff base of gossypol with 5-hydroxy-3-oxapentylamine (GSBH) has been found to complex bivalent metal cations, in particular Ca 2+, Ba 2+ and Pb 2+. This process of complex formation has been studied by ESI mass spectrometry, 1H, 13C NMR and FT-IR spectroscopy as well as by PM5 semiempirical method. It has been established that GSBH forms stable 1:1 complexes with all these cations. In all complexes the Schiff base of gossypol exists as the enamine–enamine tautomer. The Ca 2+, Ba 2+ cations are coordinated through oxygen atoms from the four hydroxyl groups, and Pb 2+ cation additionally also by two oxygen atoms from oxaalkyl chains. The structures of these complexes have been calculated by PM5 semiempirical method and discussed.