Synthesis and metal extraction studies of a novel chromogenic 5,17-bisazocalix[4]arenes

Abstract

Three novel chromogenic cone azocalix[4]arenes 5a-c, which have cavity and the azo groups as metalbinding sites and as coloration sites were synthesized. They were studied by the liquid-liquid extraction of selected metal cations (Sr2+, Ag+, Hg+, Hg2+, Co2+, Ni2+, Cu2+, Zn2+, Cr3+, Al3+). Through examination of the extraction, a novel selectivity of these compounds toward Hg2+ cations has been determined. Besides, it has been also found that azocalix[4]arene 5c is highly sensitive to acid-base titration, which can be detected by the naked eye. © Springer Science+Business Media Dordrecht 2014.