CROWN-ETHER STYRYL DYES - 23 - SYNTHESIS AND COMPLEXATION OF CIS-ISOMERS OF PHOTOCHROMIC DITHIA-15(18)-CROWN-5(6) ETHERS

A novel styryl dye containing benzodithia-18-crown-6 and N-(4-sulfobut yl)benzothiazolium fragments was synthesized. The complex formation of the cis-isomers of several photochromic styryl dyes containing dithia -15(18)-crown-5(6) fragments with Hg2+ and Mg2+ ions was studied. The stability constants of the complexes with Mg2+ and the relative stabil ity constants of the complexes with Hg2+ (with respect to benzo-1,10-d ithia-18-crown-6 ether) were measured. The fact that the stability con stant increases 11-fold on going from the trans- to the corresponding cis-isomer was attributed to the formation of an anion-''capped'' comp lex.