Linear bridging ligands, supramolecular complexes

Unfortunately, despite its poor luminescent properties, tpy is a desirable ligand from a structural point of view in the design of supramolecular photochemical devices. Metal bis(tpy) complexes are achiral, which means that they do not give rise to undesirable mixtures of diastereoisomers when more than one metal centre is present, and as a bridging ligand, substituted tpy compounds are easier to make into rigid linear connectors than bpy or phen derivatives. Furthermore, substituted tpy compounds do not exhibit facimer isomerism as do their bidentate counterparts (Figure 11.9). 

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