Correlation Within Paramagnetic Shifts of 1hnmr of 3-Imidazline Nitroxyl free Radical Transition Metal Complexes

E.M.R. Kiremire¹, G. Kumar², K. Chibale³, J.C.A. Boeyens⁴, J. Makhubela⁴ and E. Matabane⁴

¹Department of Chemistry, University of Namibia, Windhoek (Namibia) ²Department of Chemistry, University of Zambia, P.O. Box 32379, Lusaka (Zambia) ³Department of Chemistry, University of Cape Town, Rondebosch-7701 (South Africa) ⁴Department of Chemistry, University of Witwatersrand, Private Bag 3, WITS 2050 (South Africa)

The 1HNMR paramagnetic shifts of NiL2 phen, NiL2 Im2 and ML2 complexes where M=Co(II), Ni(II), Cu(II) and Zn(II) and L is the deprotonated Imidazolidine Nitroxyl free radical ligand have been synthesised and investigated. The paramagnetic shifts of the phenyl proton were found to increase in order Zn(II) < Cu(II) < Ni(II) < Co(II) in congruence with increase in the magnetic moment of the metal ion. The Ni(II) ion showed a unique anomalour behaviour with respect to the paamagnetic shifts of the methyl and -CH= protons. The phenyl proton signals appeared in the positive region relative to TMS. The proton signals were found to be characteristic of particular metal ion. There is strong evidence that the paramagnetic shifts are greatly influenced by electronic and geometric factors as wells as the nature of co-ligand.

HNMR; Imidazoidine nitroxyl free radical; metal complexes