Molecular pac-man and tacos: layered cu(ii) cages from ligands with high binding site concentrations

Abstract

The in situ formation and subsequent Cu(II) ligation of the polydentate pro-ligands o-[(E)-(2-hydroxy3- methoxyphenyl) methylideneamino] benzohydroxamic acid (L1H3), o-[(E)-(2-hydroxy-3-methoxy-5-bromophenyl) methylideneamino] benzohydroxamic acid (L2H3) and o-[(E)-(2-hydroxyphenyl) methylideneamino] benzohydroxamic acid (L3H3), leads to the self-assembly of the cages [Cu(II)(10)(L-1)(4)(2-aph)(2)(H2O)(2)](ClO4)(4)center dot 5MeOH (1), [Cu(II)(14)(L-1)(8)(MeOH)(2.5)(H2O)(7.5)](NO3)(4)center dot 3MeOH center dot 7H(2)O (2), [Cu(II)(14)(L-2)(8)(MeOH)(4)(H2O)(6)](NO3)(4)center dot 6H(2)O (3), [Cu(II)(14)(L-3)(8)(MeOH)(6)(H2O)(2)](NO3)(4)center dot 4MeOH center dot 8H(2)O (4) and [Cu(II)(30)O(OH)(4)(OMe)(2)(L-1)(16)(MeOH)4(H2O)(2)](ClO4)(4)center dot 2MeOH center dot 30H(2)O (5). Each member comprises a highly unusual topology derived from off-set, stacked, near planar layers of polynuclear subunits connected through long Cu(II)-O contacts. The exact topology observed is dependent on the specific reaction conditions and methodologies employed. Dc magnetic susceptibility studies on 1, 2, 4 and 5 reveals strong antiferromagnetic exchange between the Cu(II) centres in all siblings. We also present the 1D coordination polymer {[Cu(II)(L-4)]center dot H2O}(n) (6) comprising the pseudo macrocyclic ligand [[2-[(E)-(2-hydroxy-3-methoxyphenyl) methyleneamino] benzoyl] amino] ethanimidate (L4H2), which is formed upon the incorporation of an MeCN unit at the hydroxamate group of precursor ligand L1H3.