1,3,4-Oxadiazole based ruthenium amphiphile for Langmuir-Blodgett films and photo-responsive logic gate construction

Abstract

Amphiphilic ruthenium bipyridine complexes based on 1,3,4-oxadiazole-pyridine ligands (L1, L2) were synthesized and characterized by 1H NMR, UV–Vis spectroscopy, electrochemistry and UV–Vis spectroelectrochemistry. The free ligands and the respective ruthenium(II) complexes exhibit an intraligand π−π∗ absorption band in the UV region that overlaps with the MLCT bands. The [Ru(bpy)2(L2)](PF6)2 complex with a bidentated L2 ligand did not form a stable monolayer in water-air interface demonstrating the relevance of coordination geometry on the molecular packing properties. In contrast, stable Langmuir-Blodgett films of the [Ru(bpy)2(L1)Cl]PF6 complex (RuL1) exhibiting reversible and fast spectroelectrochemical properties associated with the Ru(III/II) redox couple were obtained, where redox site inactivation become relevant above 20 monolayers where the current leveled up. Thin LB films were deposited on poly(bithiophene) to enhance its photoelectrochemical properties and realize photoresponsive AND and OR logic gate devices.