Crystal structures, electronic properties and structural pathways of thirty [Cu(bipy)2X][Y] complexes, where X = Cl–, Br– or I–†

Abstract

The crystal structures of ten distortion isomers of the [Cu(bipy)₂X]⁺ cation have been determined, where X = Cl^– (2), Br^– (5) or I^– (3), and compared by scatter plot analysis with twenty [Cu(bipy)₂X]Y complexes of known crystal structure. In the ten new structures two involve a near regular trigonal bipyramidal stereochemistry (τ = 0.94–0.90) and eight show a square based pyramidal distorted trigonal bipyramidal stereochemistry (τ = 0.89–0.49), where τ = (α₈ – α₁)/60 [where α₁ = N(2)–Cu–Cl, α₈ = N(1)–Cu–N(3)]. Scatter plots of the eighteen cation distortion isomers of the [Cu(bipy)₂Cl][Y] series of complexes suggest that all eighteen complexes lie on a common structural pathway, involving a mixture of the symmetric, C₂, and the asymmetric, non-C₂, in-plane modes of vibration of the CuN₄Cl chromophore. The resulting structural pathways are consistent with the direct observation of the effect of the modes of vibration on the stereochemistries of the complexes. A comparison of the trends in the bipy/Cl, Br and I data suggests a size effect of the Br^– and I^– ligands.