Trinuclear Metallacycles: Metallatriangles and Much More

The geometry of trinuclear metallacrycles, obtained according to the principles of self-assembly, which includes the combination of metal fragments with two labile ligands and ditopic linkers, is studied. The directional-bonding approach shows that the design of molecular triangular metallacrycles require that six rigid ditopic components, the angular, and three linear, are assembled in a cyclic manner. Diffusion-ordered NMR spectroscopy (DOSY), based on pulse-gradient spin-echo (PGSE) NMR experiments, is a tool to distinguish the different nuclearity of metallacycles. A square planar metal center obtains a homoleptic trinuclear metallacrycles in which each corner is composed by a pair of angular linkers with monodentate binding units and coordinated vectors. X-ray structure show that, in the solid state, the flexible bmpze linkers assume a conformation in which the two coordinate vectors make a ca. 60° angle, representing the vertexes of metallacrycles.