Red and blue luminescent metallo-supramolecular coordination polymers assembled through pi-pi interactions

The use of pi-stacking interactions to control the aggregation of photo-active metal centres is explored through the design of bis(2,2';6',2 -terpyridyl) metal complexes functionalised with biphenyl 'tails'. Aryl-aryl interactions control the aggregation of the metal complexes into polymetallic arrays in the solid state. Cobalt(II), ruthenium(II), nickel(II), copper(II), zinc(II) and cadmium(II) bis-ligand complexes and a mixed ligand ruthenium(II) complex have been structurally characterised. The solid-state structures are dependent on which units dominate the pi-stacking. For cobalt, ruthenium, nickel and copper, biphenylene-biphenylene interactions lead to linear rod-like arrays, while for the group 12 d(10) ions zinc and cadmium, biphenylene-pyridyl interactions lead to two-dimensional sheets. The addition of the biphenylene tail has favourable effects on the photophysical-properties of the complexes which exhibit room temperature red (ruthenium) or blue (zinc and cadmium) luminescence, both in solution and the solid state.