Cages on a plane: a structural matrix for molecular 'sheets'.

A family of heterometallic Anderson-type 'wheels' of general formula [MM(hmp)] (M = Cr or Al and M = Ni or Zn, Hhmp = 2-pyridinemethanol) has been extended to include M = Cr or Al and M = Co, Fe, Mn or Cu, affording five new species of formulae [CrCo(hmp)](ClO) (1), [CrFe(hmp)](ClO) (2), [CrMn(hmp)](ClO) (3), [CrCu(hmp)](ClO)(NO) (4) and [AlCo(hmp)](ClO) (5). As per previous family members, the metallic skeleton common to the cations of 1-5 describes a centred hexagon with the two M sites disordered around the outer wheel, with the exception of compound 4 where the Cu sites are localised. A structurally related, but enlarged planar disc possessing a [MM] hexagon capped on each edge by a Cu ion can be formed, but only when M = Al and M = Cu. In [AlCu(OH)(hmp)](ClO)(NO) (6) the Anderson moiety contains a central, symmetry-imposed octahedral Cu ion surrounded by a wheel of Al ions. Solid-state dc susceptibility and magnetisation measurements reveal the presence of competing exchange interactions in 1-5, and very weak antiferromagnetic exchange between the Cu ions in 6 which may be intra- and/or intermolecular in nature.