Synthesis, Characterization, Langmuir−Blodgett Film-Forming Property, and Second-Order Nonlinear Optical Study of Rhenium(I) and Ruthenium(II) Diimine Complexes

A series of rhenium(I) and ruthenium(II) complexes of general formulas fac-[Re(CO)3ClL] and [Ru(bpy)2L](PF6)2 (L = N-(4-biphenyl)pyridine-2-carbaldimine (L1), N-[4-(4‘-octadecyloxy)biphenyl]pyridine-2-carbaldimine (L2), (5-octadecyloxy)-2-pyridine-N-(4-biphenyl)carbaldimine (L3), and (5-octadecyloxy)-2-pyridine-N-[4-(4‘-octadecyloxy)biphenyl]carbaldimine (L4)) were synthesized and characterized, and their photophysical properties were also studied. The X-ray crystal structures of fac-[Re(CO)3ClL1] and [Ru(bpy)2L1](PF6)2 have been determined. These complexes were capable of forming stable Langmuir−Blodgett (LB) films, as revealed by the study of their surface pressure−area (π−A) isotherms, and their second-harmonic generation (SHG) properties were also investigated.