A mixed valence manganese triangle in a trigonal lattice: structure and magnetism.

The synthesis, structural and magnetic characterisation of trinuclear manganese cluster, [Mn(3)O(O(2)C-anth)(6)(HOCH(3))(3)] 1 (where O(2)C-anth = 9-anthracenecarboxylate), with crystallographic three-fold (C(3)) symmetry, are described. The cluster was prepared by a carboxylate exchange reaction between HO(2)C-anth and [Mn(12)O(12)(O(2)CMe)(16)(H(2)O)(4)] with concomitant fragmentation of the dodecanuclear Mn core of the starting material to form a trinuclear Mn(3)(μ(3)-O) cluster capped by six carboxylate ligands. Bond valence sum calculations and SQUID magnetometric measurements establish the oxidation states of the metal ions as Mn(II)·2 Mn(III) which are antiferromagnetically coupled.