Progressive Decoration of a Pentanuclear Cu(II) 12-Metallocrown-4 Towards Targeted 1- and 2-D Extended Networks

The synthesis, structures and magnetic characterisation of a family of discrete planar pentanuclear Cu(II) 12-MC-4 metallacrowns of formulae [Cu5(L1)4(MeOH)4](ClO4)2 (1), [Cu5(L1)4(py)2](ClO4)2·py (2), [Cu5(L1)4(py)6](ClO4)2 (3) and [Cu5(L2)4(MeOH)4](ClO4)2·H2O (7) (where L1H2 = 2-(dimethylamino)phenylhydroxamic acid and L2H2 = 2-(amino)phenylhydroxamic acid) are reported. UV-vis and Electrospray MS studies indicate solution stability with respect to their {Cu5(L)4}2+ cores. Magnetic susceptibility measurements confirm strong antiferromagnetic exchange between the Cu(II) ions resulting in isolated S = 1/2 ground spin states. The introduction of ditopic co-ligands such as 4,4¿-bipyridine (4,4¿-bipy), pyrazine (pz) and 4,4¿-azopyridine (4,4¿-azp) results in their coordination at a number of axial Cu(II) sites within the {Cu5} metallacrown nodes to afford the extended networks {[Cu5(L1)4(4,4¿-bipy)3](ClO4)2·(H2O)}n (4), {[Cu5(L1)4(4,4¿-azp)2(MeOH)2](ClO4)2}n (5) and {[Cu5(L2)4(pz)2(MeOH)3](ClO4)2·MeOH}n (6).