Study of Carboxylate and Hydroxamate of Some Transition Metal Complexes as MRI Contrast Agents

Abstract

In this work the synthesis and characterization of carboxylate and hydroxamate complexes of some transition metals were investigated. This work is divided into two parts. In part one the ligands were synthesized by direct and indirect method.Complexes of the isolable ligands with MnII and GdIII as potential MRI contrast agents, were studied and characterized using various method of analysis e.g. IR, NMR, MS and elemental analysis. In the second part twenty four complexes of EDTA and CyDTA-lanthanide with different counter cations, e.g. NH4(LnIII)(L), Na(LnIII)(L), Li(LnIII)(L), (CH6N3)+ (LnIII)(L),where (LnIII = EuIII,GdIII, ErIII, and L= EDTA, CyDTA)have been prepared and characterized by IR to investigate the variation of coordination number from eight to nine both in solid state and solution. It was found that in most cases CN9 is more acceptable in solution. Two of these complexes GdIII-EDTA and GdIII-Cydta were studied using 17O NMR water exchange and compared with previous results of similar compounds depending on their water exchange rates in order to measure their value as MRI contrast agents. It was found that EDTA complexes have fast water exchange rate and the reaction proceed via a dissociative mechanism, comparing with CyDTA, with slower water exchange rate and slightly associative mechanism. This indicates that the EDTA complexes would have better potential to act as MRI contrast agents.