Imidazoanthraquinone Derivatives for the Chromofluorogenic Sensing of Basic Anions and Trivalent Metal Cations

Four imidazoanthraquinone derivatives (2a-d) were synthesized and characterized and their coordination behavior against selected anions and cations tested. Acetonitrile solutions of probes showed charge-transfer absorptions in the 407-465 nm range. The four probes emitted in the 533-571 nm interval. The recognition ability of 2a-d was evaluated in the presence of F-, Cl-, Br-, I-, OCN-, BzO-, ClO4-, AcO-, HSO4-, H2PO4-, and CN-. Only F-, AcO-, and H2PO4- induced a new red-shifted absorption band that was attributed to a deprotonation process involving the amine moiety of the imidazole ring. Moreover, upon increasing quantities of F-, AcO-, and H2PO4-, moderate quenching was induced in the emission of 2a-d together with the appearance of a new red-shifted band. The UV-visible and emission behavior of the four probes in the presence of Cu2+, Co2+, Mg2+, Fe3+, Ba2+, Fe2+, Ni2+, Ca2+, Zn2+, Pb2+, Cd2+, Cr3+, Al3+, K+, and Li+ was also assessed. Only addition of Fe3+, Cr3+, and Al3+ caused a new blue-shifted band in 2a-d that was ascribed to a preferential coordination with the acceptor part of the probes. Moreover, an important quenching of the emission was observed which was ascribed to the interaction between these trivalent cations and 2a-d. © 2014 American Chemical Society.