Electrochemical and spectroelectrochemical studies of bis(diketonate) thorium(IV) and uranium(IV) porphyrins

Abstract

The synthesis, characterization and chemical properties of actinide and lanthanide metalloporphyrin complexes have been the subject of several recent reports [l-6]. A combination of the coordination properties of actinide metals [7] with the ligation properties of metalloporphyrins has resulted in the generation of several distinct sets of molecular structures. These include monomeric species, trimeric species and triple decker type species. The monomeric [2-41 complexes are represented by dichloro and bis(acetylacetonato) porphyrins of the form (P)MC12L2 and (P)M(acac)* where L is the solvent molecule, acac is acetylacetonate, P is the dianion of a given porphyrin macrocycle and M is Th or U. Other structures include ‘triple decker’ complexes of the form (P),M, [5], where M is one of 12 different metal ions and a trimeric complex of the form [(P)Th(OH)*] a [6]. In each case, crystallographic determinations [4-61 have been reported. have recently been reported [6]. All electrode reactions of the porphyrin or phthalocyanine species were found to occur on the macrocyclic ligand and, for the case of trimeric [(P)Th(OH),],, up to six electrons could be either reversibly abstracted or added to the molecular unit at low temperature on the electrochemical time scale. A three electron oxidation step was also observed for this trimeric complex.