Triarylmethane dye-conjugated hexanuclear zinc complexes: Photophysical properties and cyanide anion-binding behavior

• Triarylmethane dye–conjugated hexanuclear zinc complexes were synthesized.
• Crystal structures of the leuco- and dye-form complexes were compared.
• Photophysical properties of the complexes were determined.
• The complexes showed cyanide-selective anion-sensing ability.

Hexanuclear zinc complexes conjugated with a triarylmethane (TAM) dye were prepared by chemically oxidizing the corresponding leuco-form complexes. The dye-form complexes exhibited an intense absorption band around 542 nm, which is typical of TAM dyes. The molecular structures of the leuco- and dye-form complexes were compared on the basis of X-ray crystal structure data. Adding a stoichiometric amount of cyanide anion to a solution of one of the dye-form complexes resulted in discoloration, suggesting the formation of a leuconitrile. Halide anions showed similar discoloration activity, but the stoichiometry was not simple for Cl–, Br–, and I–. The formation of covalent bond between cyanide anion and the dye moiety was also confirmed by cyclic voltammetry.

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