Crystal structure of bis(2-aminoethyl)amine(di-2-pyridylamine)zinc(II) nitrate and the electronic properties of the copper(II)-doped system

Abstract

The crystal structure of the title compound [Zn(dien)(bipyam)][NO₃]₂ has been determined by X-ray crystallographic analysis using photographic data. The complex crystallises in the monoclinic space group P2₁/c, with a= 12.34(5), b= 16.26(5), c= 9.92(5)Å, β= 92.0(5)°, and Z= 4. The zinc(II) ion is five-co-ordinate with a distorted trigonal-bipyramidal stereochemistry, the mean out-of-plane and in-plane Zn–N bond distances being 2.20 and 2.09 Å respectively. The e.s.r. and electronic spectra of 1% copper-doped [Zn(dien)(bipyam)][NO₃]₂ have been determined using polycrystalline samples and single-crystal techniques and the results interpreted to suggest that the stereochemistry of the doped CuN₅ chromophore corresponds closely to that observed in the isomorphous [Cu(dien)(bipyam)][NO₃]₂ complex, rather than to the stereochemistry of the ZnN₅ chromophore of the host lattice. Caution is expressed over the use of the Zn–N distances and N–Zn–N angles to describe the stereochemistry of the CuN_x chromophore when doped into isomorphous zinc(II) complexes as host lattices and the use of the electronic reflectance spectra of copper(II)-doped zinc(II) complexes as a criterion for comparable stereochemistries is advocated. A comparison of the g and A factors and one-electron orbital energies is made with other very distorted copper(II) systems.