Generation of [2X2] grid metallosupramolecular architectures from preformed ditopic bis(acylhydrazone) ligands and through component self-assembly

Ditopic bis(acylhydrazone) ligands, derived from the reactions of carbohydrazides with 2-phenylpyrimidine-4,6-dicarbaldehyde and designed for grid formation with octahedrally coordinating transition-metal ions, exhibit a varied coordination chemistry depending upon the degree of their deprotonation. The neutral acylhydrazones are relatively poor ligands and are seemingly involved in multiple, labile complexation equilibria varying with the solvent and the particular metal salt in solution; nevertheless, grid complexes of different forms can be isolated in the solid state. Although only limited study has been made of the singly deprotonated ligands, grid species appear to be much more readily isolated. With the doubly deprotonated ligands, grid formation is strongly favoured in both the solution and solid states. As a consequence, the grid structures form spontaneously in the presence of a base by self-assembly from their components without need to preform the ditopic ligands. Extensive structural studies have been carried out both to establish the grid structures and to analyse the nature of the supramolecular interactions possible for neutral and charged grid species. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).