Crystal and molecular structure, electron spin resonance, and electronic spectrum of hexakis(imidazole)copper(II) nitrate

Abstract

The structure of the title compound has been established by three-dimensional X-ray crystal-structure analysis from diffractometer data. Crystals are monoclinic, space group P2₁/c, with a= 8·65(1), b= 17·64(1), c= 8·38(1)Å, β= 93·20(10)°, Z= 2. The structure was solved by the heavy-atom approach and molecular parameters were refined by full-matrix least-squares calculations to R 0·043 for 2137 independent reflections. The copper atom co-ordination in the centrosymmetric cation is distorted octahedral with Cu–N 2·012(2), 2·049(2), and 2·593(3)Å. In the crystal the nitrate ions bridge the complex cations through N–H ⋯ O hydrogen bonds, with N ⋯ O 2·815, 2·897, 3·073, and 3·086 Å. The single-crystal e.s.r. and polarised electronic spectra are also reported and the electronic structure of the chromophore discussed with reference to these and the crystallographic data.