Leeland J.W.,University of Edinburgh |
Finn C.,University of Edinburgh |
Escuyer B.,Ecole Nationale de Chimie |
Kawaguchi H.,Tokyo Institute of Technology |
And 3 more authors.
Dalton Transactions | Year: 2012
A series of polydentate dual-compartment, Schiff-base pyrrole macrocycles has been prepared through the straightforward Lewis acid catalysed [1 + 1] condensation reactions between ONO or O5-linked aryldiamines and dipyrromethane dialdehydes. These macrocycles display hydrogen-bond acceptor and donor properties and provide distinct N4 and O5/ONO donor sets for metallation reactions, so forming alkali, alkaline earth, and transition metal complexes that were characterised spectroscopically and crystallographically. While the conformationally flexible O5 donor set allows the formation of helical potassium salt structures, the transition metal complexes of all variants of these macrocycles invariably adopt wedged, Pacman-shaped structures in which the metal is bound in the pyrrole-imine N 4 donor set, so leaving the ONO/O5 donor set pendant and apical. In some cases (V, Cr, and Co), this proximate combination of Lewis acid binding site and hydrogen bond acceptor facilitates the coordination of water within the molecular cleft; alternatively, direct interaction between the pendant arm and the metal is seen (e.g. Ti). Higher order [2 + 2] macrocycles were also prepared as minor, inseparable by-products of cyclisation, and Fe 2, Mn2, and Co2 complexes of these larger macrocycles were found to adopt binuclear helical structures by X-ray crystallography. © 2012 The Royal Society of Chemistry. Source