Assembly of BF4−, PF6−, ClO4− and F− with trinuclear copper(i) acetylide complexes bearing amide groups: structural diversity, photophysics and anion binding properties

Abstract

Trinuclear copper(I) acetylide complexes 1·BF₄–4·BF₄, 1·PF₆, 1·ClO₄ and 4·F have been synthesized and characterized. Five kinds of discrete or polymeric structures could be found in their crystal structures. Among them, complexes 1·BF₄, 1·PF₆, and 1·ClO₄ form zigzag one-dimensional (1D) anion coordination polymers (ACPs) using anions as nodes and cations 1 as ligands. For complex 2·BF₄, hydrogen bonds between adjacent amide groups afford the zigzag 1D polymeric chains, which are supported by the interaction between dppms and anions. A 1D infinite meso-helical hydrogen bonding polymeric chain with a counter anion bound in each cation can be observed in complex 3·BF₄. Complex 4·BF₄ is unable to form polymeric chains, while complex 4·F that exhibits similar structure with 4·BF₄ could construct infinite 1D polymer via hydrogen bonds between amide groups. The photophysical properties of copper(I) acetylide complexes have been studied. They show luminescence both in the solid state and DMSO solution at 298 K. The anion binding abilities of complexes 1·BF₄–4·BF₄ in DMSO have also been studied by using ¹H NMR and UV-vis titration experiments. Their dramatic color change towards F⁻ in DMSO enables naked eye detection of F⁻.