Effect of metal complexation on the nonlinear optical response in conjugated ligands

Organic nonlinear optical materials are widely investigated materials for fabricating optoelectronic devices. Particularly organic π-conjugated systems as well as transition metal complex compounds are studied in this direction because of the strong electronic coupling between the ligand and the metal, their excellent chemical stability, and their rich photochemical and photophysical properties. In this work, comparative studies of the third-order nonlinear optical susceptibilities of a bipyridine ligand (4-(N,N-dibutylamino)-4′-(5-ethynyl-2,2′-bipyridine)-azobenzene (A) and of the corresponding heteroleptic ruthenium complex (Ru(bpy)2(La)(PF6)2 (B) (La signifies the ligand) are presented. The NLO properties were investigated by means of the Z-scan technique using a 30 ps mode-locked Nd-YVO4 laser at 532 nm with a repetition rate of 10 Hz. Our results show that the introduction of the metal in the organic complex results in a significant modification of the third-order nonlinear optical response.