Molecular engineering of octupolar tris(bipyridyl) metal complexes

Abstract Metal complexes of nitrogen-heterocyclic ligands, such as bipyridines, represent an important class of nonlinear optical (NLO) chromophores. They are associated with low-energy intraligand charge-transfer (ILCT) and/or metal to ligand charge-transfer (MLCT) excitations. These ligands are excellent building blocks for the construction of octupolar metal complexes of D 3 symmetry. To design tris(bipyridyl) metal complexes with enhanced optical nonlinearities, we have developed the synthesis of a series of 4,4′-dialkenyl-2,2′-bipyridines bearing π-donor substituents. The influence of the metal on the linear and nonlinear optical properties has been investigated. This study shows that the NLO response can be fine-tuned by changing either the donor group or the metal centre.