NICKEL(II) COMPLEXES OF IMIDAZOLE-DERIVED LIGANDS WITH AN AMIDE GROUP: SOME COMPOUNDS WITH COMPLEX MAGNETIC BEHAVIOUR

ABSTRACT

NiL₄X₂·xH₂O compounds [L=1-(2-carbamoylethyl)-4-methylimidazole (C4MIm), 1-(2-carbamoylethyl)benzimidazole (CBIm) or 1-(2-carbamoylethyl)-5,6-dimethylbenzimidazole (CMMBIm)] have been prepared and characterised and the effect of different axial ligands, X, on the magnetic properties of the complexes has been examined. Diamagnetic and paramagnetic complexes with CMMBIm have been obtained. With C4MIm and CBIm, only paramagnetic compounds could be isolated. The CBIm ligand afforded complexes with unusual magnetic behaviour: NiCl₂(CBIm)₄ is believed to exhibit a spin-singlet ground state with a low-lying spin triplet state and NiBr₂(CBIm)₄ shows magnetic properties indicating structural changes over the temperature range studied. Structures of the compounds have been proposed based on spectroscopic and magnetic data and on powder X-ray diffraction patterns.

ACKNOWLEDGMENTS

Gabriela Silva thanks the Junta Nacional de Investigação Científica e Tecnológica (Lisbon) for a M.Sc. grant under Programa Ciência. Financial support by Fundação para a Ciência e a Tecnologia, Lisbon, to Laboratório de Química Inorgânica Pura e de Apliçãao Interdisciplinar (LAQUIPAI) is gratefully acknowledged. The authors thank the Instituto Geológico e Mineiro (S. Mamede de Infesta, Portugal) and the Researcher M. Lurdes Reis for the powder X-ray diffraction pattern determinations.