Synthesis, characterization, and second-harmonic generation studies of rhenium(I) surfactant complexes in Langmuir-Blodgett films

Abstract

A series of rhenium(I) surfactant complexes of general formula fac-[Re(CO)3(bpy)(L)]PF6 (bpy = 2,2′-bipyridine, L = 4-(4′-octadecyloxyphenylazo)pyridine (L1), 4-(4′-octadecyloxyphenylstilbazole)pyridine (L2), 4-(4′-octadecyloxyphenylethynyl)pyridine (L3)) were synthesized and characterized, and their photophysical and photochemical properties studied. The X-ray crystal structure of the complex fac-[Re(CO)3(bpy)(L1)]PF6 has been determined. The formation and optical properties of these complexes in Langmuir - Blodgett (LB) films were studied by surface pressure-area (π-A) isotherms and UV - visible and luminescence spectroscopy. Their second-harmonic generation (SHG) behavior has also been investigated. These Re(I) surfactant complexes were shown to exhibit first-order hyperpolarizabilities comparable to, and in some cases slightly higher than, those of their organic analogues.