A pyrene-based fluorescent sensor for Zn2+ ions: a molecular 'butterfly'

A simple pyrene-based triazole receptor has been synthesised and shown to self-assemble in the presence of ZnCl2 in an exclusively 2 : 1 ratio, whereas a mixture of 2 : 1 and 1 : 1 ratios are observed for other Zn2+ salts. The pyrene units are syn in orientation; this is supported by a strong excimer signal observed at 410 nm in the presence of ZnCl2 in acetonitrile. DFT calculations and 2D NMR support the proposed structure.