Synthesis and fungitoxic activity of manganese(II) complexes of fumaric acid: X-ray crystal structures of [Mn(fum)(bipy)(H 2O)] and [Mn(Phen) 2(H 2O) 2](fum)·4H 2O (fumH 2=fumaric acid; bipy=2,2′-bipyridine; phen=1,10-phenanthroline)

Abstract

The reaction of fumaric acid with Mn(CH 3COO) 2·4H 2O gives the polymeric complex {Mn(fum)} n ( 1). Complex 1 reacts with 2,2′-bipyridine in ethanol to yield [Mn(fum)(bipy)(H 2O)] n ( 2). Reaction of 1 with 2 equiv. of 1,10-phenanthroline produces [Mn 2(fum) 2(phen) 2.5]·3H 2O ( 3) and [Mn(phen) 2(H 2O) 2](fum)·4H 2O ( 4). The molecular structures of 2 and 4 were determined by X-ray crystallography. In 2 the fumarate anions link the manganese ions so that each is seven coordinate, being bonded to a bidentate bipyridine, two bidentate carboxylates and one H 2O molecule. In 4 the asymmetric unit contains a [Mn(phen) 2(H 2O) 2] 2+ cation, half of each of two independent fumarate anions and four lattice H 2O molecules. The cations and anions are interconnected by water molecules hydrogen bonded to both coordinated water molecules and fumarate oxygens. The fumarate complexes, the metal free ligands and a number of simple manganese salts were each tested for their ability to inhibit the growth of Candida albicans. Only the ‘metal free’ 1,10-phenanthroline and its fumarate complexes exhibit fungitoxic activity