Progressive decoration of pentanuclear Cu(II) 12-metallacrown-4 nodes towards targeted 1-and 2D extended networks

The synthesis, structures and magnetic characterisation of a family of discrete planar pentanuclear Cu(II) 12-MC-4 metallacrowns of formulae [Cu-5(L-1)(4)(MeOH)(4)](ClO4)(2) (1), [Cu-5(L-1)(4)(py)(2)](ClO4)(2)center dot py (2), [Cu-5(L-1)(4)(py)(6)](ClO4)(2) (3) and [Cu-5(L-2)(4)(MeOH)(4)](ClO4)(2)center dot 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 {Cu-5(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 {Cu-5} metallacrown nodes to afford the extended networks {[Cu-5(L-1)(4)(4,4'-bipy)(3)](ClO4)(2)center dot(H2O)}(n) (4), {[Cu-5(L-1)(4)(4,4'-azp)(2)(MeOH)(2)](ClO4)(2)}(n) (5) and {[Cu-5(L-2)(4)(pz)(2)(MeOH)(3)](ClO4)(2)center dot MeOH}(n) (6).