New [2 × 2] cyclic framework that induces distortions from square planar to tetrahedral around the copper(II) centers

A new tetracopper(II) complex [Cu4(bsbd)4] (bsbd = bis(N-salicylidene)benzene-1,4-diamine) has been prepared and structurally characterized. The complex constructs a [2 × 2] cyclic coordination framework, which inhibits formation of square planar copper(II) centers, and induces distortion to a tetrahedral structure. The effects of the distortions on the absorption spectra are characterized.