Structural elucidation of Cu(II) ion doped in hexaaquozincdiaquobis(malonato)zincate host by EPR spectroscopy

In order to understand the structural behaviour of Cu(II) in a variety of ligand environments, single crystal electron paramagnetic resonance studies of Cu(II) doped in hexaaquazincdiaquabis(malonato)zincate [Zn(H2O)6][Zn(mal)2(H2O)2] are carried out at 300 K. Angular variation of copper hyperfine lines in three orthogonal planes shows the presence of single site, with spin Hamiltonian parameters as gxx=2.034, gyy=2.159, gzz=2.388, Axx=3.39 mT, Ayy=4.89 mT and Azz=13.72 mT. The g/A tensor direction cosines are compared with various Zn–O directions in the host lattice, which confirm that Cu(II) enters substitutionally in the lattice. The low value of Azz has been explained by considering admixture of dx2−y2dx2−y2 ground state with dz2dz2 excited state. EPR powder spectra at 300 and 77 K give identical spin Hamiltonian parameters (g∥=2.367, g⊥=2.088, A∥=11.47 mT, A⊥=2.63 mT). IR, UV–vis and powder XRD data confirm the structure and symmetry of the Cu(II) ion in the host lattice.