SCHIFF BASE MACROCYCLES: RELIABLE TEMPLATES FOR MULTINUCLEAR METALLOCAVITANDS
Recent studies of polydentate Schiff base macrocycles indicate larger diameter macrocycles often deviate from planarity upon metal complexation, taking on a concave conformation. These bowl shaped complexes are reminiscent of organic cavitands, however, their dependence on metal coordination
rather than C-C bonds for curvature has led us to dub them metallocavitands. In particular, we have prepared a family of soluble [3 + 3] Schiff base macrocycles from the condensation of 3,6-diformylcatechol with 1,2-dialkoxy-4,5-diaminobenzenes and investigated their ability to template
the formation of metallocavitands. When reacted with seven equivalents of Zn(OAc)2 or Cd(OAc)2, hepta-nuclear metallocavitands are formed. Dimerization of these complexes into capsules has been observed and the thermodynamics of self-association has been studied. Tuning the cavity dimensions
and strength of supramolecular self-association is easily achieved by switching metals. Isolation of a tetra-zinc intermediate has provided insight into the template effect our macrocycles exhibit. These results highlight the reliability of Schiff base macrocycles as scaffolds for metallocavitand
formation.
Keywords: Schiff base; macrocycle; metal cluster; metallocavitand; supramolecular chemistry; template
Document Type: Research Article
Affiliations: Department of Chemistry, University of British Columbia, Vancouver, BC, Canada
Publication date: 01 January 2008
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