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-hydroxy-3-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(L₁)₄(2-aph)₂(H₂O)₂](ClO₄)₄·5MeOH (1), [Cu(II)₁₄(L₁)₈(MeOH)_2.5(H₂O)_7.5](NO₃)₄·3MeOH·7H₂O (2), [Cu(II)₁₄(L₂)₈(MeOH)₄(H₂O)₆](NO₃)₄·6H₂O (3), [Cu(II)₁₄(L₃)₈(MeOH)₆(H₂O)₂](NO₃)₄·4MeOH·8H₂O (4) and [Cu(II)₃₀O(OH)₄(OMe)₂(L₁)₁₆(MeOH)₄(H₂O)₂](ClO₄)₄·2MeOH·30H₂O (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)(L₄)]·H₂O}_n (6) comprising the pseudo macrocyclic ligand [[2-[(E)-(2-hydroxy-3-methoxy-phenyl)methyleneamino]benzoyl]amino]ethanimidate (L₄H₂), which is formed upon the incorporation of an MeCN unit at the hydroxamate group of precursor ligand L₁H₃.