Manganese compounds with phthalate and terephthalate ligands: Synthesis, crystal structure, magnetic properties and catalase activity

Abstract

The reactivity of carboxybenzoic acids substituted in ortho, meta and para positions (phthalic, isophthalic and terephthalic acids) has been explored. These acids have been used for the synthesis of dinuclear MnIII and polynuclear MnII compounds, obtaining unexpected results. From all the reactions, one dinuclear MnIII compound, [{Mn(H2O)(phen)}2(l-2-COOHC6H4COO)2(l-O)](ClO4)2 (1), one mixed valence compound, [{Mn(phen)2}2(l-O)2](NO3)3 (2), and four MnII compounds, [{Mn(H2O)(phen)2}2(l-4-COOC6H4- COO)](NO3)2 (3), [Mn3(l-4-COOC6H4COO)3(bpy)2]n (4), [{Mn(phen)2}2(l-2-COOHC6H4COO)2](ClO4)2 (5) and [Mn(l-2-COOC6H4COO)(H2O)2(phen)]n (6), (phen = 1,10-phenanthroline, bpy = 2,20-bipyridine) have been obtained and characterised by X-ray diffraction, showing different coordination modes for the carboxylate ligand: a bidentate bridge in a syn syn, syn-anti or anti-anti mode, a bis-monodentate bridge and a bis-bidentate bridge. The six compounds show antiferromagnetic coupling, with magnetic interaction constants of 3.7 and 332.5 cm 1 for the dinuclear MnIII (1) and MnIIIMnIV (2) compounds and 0.04, 4.5, 1.5 and 0.55 cm 1 for MnII compounds 4-6. Each MnII compound shows a different EPR spectrum at 4 K, which has been simulated including the ZFS parameters. The catalase activity of the compounds with phthalate and terephthalate ligands has been studied, the former being less active than the latter.