Structural elucidation of transition metal complex by single crystal EPR study

Abstract

Single crystal EPR studies of Mn(II) doped hexaaquazincdiaquabis(malonato) zincate [Zn(H 2O) 6][Zn(mal) 2(H 2O) 2] have been carried out at room temperature using X-band spectrometer to identify the location of the dopant. Single crystal rotations along the three orthogonal axes show more than 30 line pattern EPR spectra indicating the presence of two types of dopant ions in the host lattice, with intensity ratio of 6:1. However, the latter could not be followed due to its low intensity during crystal rotations. The spin-Hamiltonian parameters, estimated from the three mutually orthogonal crystal rotations are: g xx = 1.972, g yy = 2.000, g zz = 2.023, A xx = 8.95, A yy = 9.48, A zz = 9.93 mT, D xx = −34.49, D yy = −3.26, D zz = 37.74 mT and E = 15.6 mT. The direction cosines of one of the principal values of g match with that of Zn–O bond in the host lattice, suggesting that the Mn(II) ion entered the lattice substitutionally. The large value of E is indicative of low symmetry of the substitutional site, in accordance with the crystal structure of the isomorphous [Zn(H 2O) 6][Cu(mal) 2(H 2O) 2]. Covalency of Mn–O bond, estimated from Matamura’s plot, is 9%. Various admixture coefficients, bonding and optical parameters have also been calculated.