Crystal structure of an infinite stair-type chain compound [{Cu2(tc)2(ClO4)2}n](tc = thiochrome)

Abstract

The infinite stair-type chain compound [{Cu₂(tc)₂(ClO₄)₂}_n](tc = thiochrome) crystallizes in the monoclinic space group P2₁/c with a= 9.50(1), b= 22.79(1), c= 7.889(6)Å, β= 111.06(8)° and Z= 2 (R= 0.068, R′= 0.070). The dimeric units are mutually linked by the 2-hydroxyl group of the co-ordinated thiochrome, just like one step in a stairs. Each copper(I) atom in the unit has a three-co-ordinate T-shaped geometry with two nitrogen and one oxygen donor, providing a unique dimetal structure having a short Cu ⋯ Cu contact [2.476(3)Å]. Proton NMR spectra and cyclic voltammograms demonstrate that the species formed in solution is not polymeric but a low-molecular-weight dicopper complex, in which the 2-hydroxyethyl group is not co-ordinated. The cyclic voltammogram in the solid state gives a single quasi-reversible wave, indicating that the dicopper site undergoes redox reactions, whose stability is associated with the three-co-ordinate geometry and/or co-ordination of the alcohol group.