Emission spectroscopy of a ruthenium(ii) polypyridyl complex adsorbed on calcium niobate lamellar solids and nanosheets.

Ru(ii) tris-diimine complexes are known to exhibit emission at around 630 nm as a result of (1)MLCT photoexcitation. The emission is quenched in the presence of a suitable semiconductor solid due to electron injection from the excited state of a Ru(ii) complex to the conduction band of the adjacent semiconductor. Here we investigated emission quenching behaviour of Ru(II){(4,4'-(CH3)2-bpy)2(4,4'-(CH2PO3H2)2-bpy)} (bpy = 2,2'-bipryridine) adsorbed on HCa2Nb3O10 solids having an ordered lamellar structure or a disordered nanostructure. Even though electron injection from the excited state of the Ru complex to the conduction band of nanostructured HCa2Nb3O10 is thermodynamically less favorable than that of layered HCa2Nb3O10, faster electron injection was observed using nanostructured HCa2Nb3O10. Experimental results highlighted that electron injection from the excited Ru complex takes place not only in the conduction band of HCa2Nb3O10 but also mid-gap states whose density is strongly dependent on both the morphological feature and the preparation method of HCa2Nb3O10.