Copper(II) complexes of isomeric aminophenylhydroxamic acids. A novel ‘clam-like’ dimeric metallacrown and polymeric helical structure containing interlinked unique copper(II) sites

The reaction of 3-aminophenylhydroxamic acid with CuSO4·5H2O in aqueous solution gives the novel helical polymer [Cu3(3-Apha)4(H2O)SO4]n·8H2O 1 the structure of which contains interlinked repeating units having three unique neutral, anionic and cationic copper(II) sites. In this complex the copper(II) sites are magnetically non-interacting. A similar reaction with 2-aminophenylhydroxamic acid gives the novel dimeric ‘metallacrown’ [Cu5(2-AphaH−1)4(μ-SO4)(H2O)2]2·10H2O 2 which has a ‘clam-like’ structure showing strong antiferromagnetic behaviour. In contrast to the above ligands, 4-aminophenylhydroxamic acid gives the monomeric square planar complex Cu(4-Apha)2·H2O 3 which exhibits paramagnetic behaviour. Crystal structures of all three complexes are reported.