Site selective 3d heterometallic molecular strings based on bis-β-diketone ligand

Abstract

One of the major challenges of coordination chemistry today is the design and synthesis of molecules with predetermined functions and physicochemical properties. Our research group is addressing this challenge through the preparation of polydentate ligands from the bis-β-diketone family, capable of gathering transition metals within molecular clusters of well-defined nuclearity and topology. Known structural motifs arising from these platforms are weakly coupled cluster pairs as prototypes of 2-qubit quantum gates, and chain-like arrays as potential prototypes of molecular wires. One of the ligands capable to accommodate metal ions into linear chains is trispyridyl/ bis-β-diketone, H2L, (1,3-bis-(3-oxo-3-(2-pyridyl)propionyl)pyridine) as demonstrated with the synthesis of the supramolecular array [Co4L2(MeOH)8](NO3)4 and its analogues. We are now presenting the potential of this ligand for the preparation of new 3d heterometallic molecular strings with site selective metal composition as a direct consequence of crystal field energy effects. Among them, the most interesting cases are tetranuclear and octanuclear Co-Ni systems where two very similar metals are easily differentiated due to the above described selectivity. From the synthetic point of view, it will be shown how small changes in reaction conditions can vary the nature of the obtained system leading from charged species to neutral molecules. The solid state and solution behaviour of those systems will be discussed following crystallographic, spectroscopic, magnetic and redox studies.