New dithiacrown–ether butadienyl dyes: synthesis, structure, and complex formation with heavy metal cations

摘要

Benzothiazole type butadienyl dyes containing a dithia-15-crown-5 (2a) or dithia-18-crown-6 ether (2b) moieties were synthesized. The structures of dyes 2a,b and their complexes with AgR and Pb2R were studied by an X-ray crystallography. It was found that the conformations of dithiacrown–ether moieties of dyes 2a,b are unfavorable for complex formation and change significantly upon binding of AgR or Pb2R. The complexation of 2a,b with AgR, Cd2R, Pb2R, and Hg2R in water–acetonitrile mixtures with different contents of water (PW%0–75%, v/v) was studied by 1H NMR, UV–Vis spectroscopy, and polarography. In anhydrous acetonitrile, the stability constants of 1:1 complexes change in the sequence Cd2R 104). The complexation of 2a,b with Hg2R at PW - 50% is accompanied by a substantial hypsochromic effect. This allows dithiacrown-containing butadienyl dyes to be used as selective optical molecular sensors for heavy metal ions, in particular, in aqueous solutions.