Fluorescence spectra of complexes of hypericin with s2 metal cations

Abstract

The chlorides of s(2) metal cations including Sn2+, Sb3+, Bi3+ and Te4+ form complexes with hypericin as indicated by a blue shift of the absorption and fluorescence of hypericin. It is suggested that this is caused by a stabilization of the aromatic HOMO of hypericin by the s(2) metal centers. This, in turn, increases the HOMO/LUMO gap of hypericin. A concomitant decrease of the fluorescence intensity occurs, probably due to a heavy-atom effect. (C) 2015 Elsevier B.V. All rights reserved.