Single Crystal EPR and Optical Studies of Vanadyl (II) Doped in Tetra aqua (1, 10-Phenanthroline-k2 N, N’) Magnesium (II) Dinitrate

M. Rajeswari, S. Sivakumar^*, Hema Ramesh, K. Mageswari, A. Rajappa and S. Savithri 
Department of chemistry, Sri Manakula Vinayagar Engineering College, Puducherry, India.
Received: 6 May 2014, Accepted: 1 July 2014, Published Online: 27 July 2014

Abstract
Single crystal EPR and optical investigation of vanadyl doped tetraaqua (1,10-phenanthroline-k² N,N’)magnesium(II)dinitrate (abbreviated a TPMD) have been carried out at room temperature, using X-band frequencies.  TPMD [Mg(C₁₂H₈N₂)(H₂O)₄]-(NO₃)₂, belongs to monoclinic crystal class with space group C2/c having cell parameter a = 1.391, b = 1.048, c = 1.239 nm, a = g = 90° , b =102.17° and  Z = 4 [1].  Magnesium atom coordinates with phenanthroline acting as a bidentate ligand through both N atoms.  Four water molecules complete the environment around the metal atom with octahedral geometries. Single crystal rotations carried out in the three mutually orthogonal crystallographic planes namely ab, bc* and ac* indicate two chemical equivalent sites with different intensity.  However, the second site could not followed due to it’s weaker intensity and overlap with first site, during crystal rotations.  The spin Hamiltonian parameters obtained for the site are:  g_xx = 1.977 g_yy = 1.971 g_zz = 1.939; A_xx= 6.00, A_yy = 6.44, A_zz = 16.86 mT. These values agree well with reported data [2].  From the direction of cosines of principal g and A values, it has been confirmed that the impurity has entered the lattice interstitially.  Admixture coefficients, Fermi contact (k) and dipolar interaction (P) have also been evaluated and the covalence of metal–ligand bond is deduced as 13%.  Optical, IR and powder XRD techniques have been used to characterize the structure of the complex.
Keywords: Single crystal EPR, Octahedral geometries, Fermi contact, dipolar interaction, Hamiltonian parameters.