Designed Topology and Site-Selective Metal Composition in Tetranuclear [MM′...M′M] Linear Complexes

The ligand 1,3-bis[3-oxo-3-(2-hydroxyphe nyl)propionyl] benzene (H,L), designed to align transition metals into tetranuclear linear molecules, reacts with W salts (M = Ni, Co, Cu) to yield complexes with the expected [MM...MM] topology. The novel complexes [Co4L2(py)(6)] (2; py = pyridine) and [Na(py)(2)][Cu4L2(py)(4)](ClO4) (3) have been crystallographically characterised. The metal sites in complexes 2 and 3, together with previously characterised [Ni4L2(py)(6)] (1), favour different coordination geometries. These have been exploited for the deliberate synthesis of the heterometalic complex [Cu2Ni2L2(py)(6)] (4). Complexes 1, 2, 3 and 4 exhibit antiferro-magnetic interactions between pairs of metals within each cluster, leading to S=0 spin ground states, except for the latter cluster, which features two quasi-independent S=1/2, moieties within the molecule. Complex 4 gathers the structural and physical conditions, thus allowing it to be considered as prototype of a two-qbit quantum gate.