Synthesis, characterization and LB films construction of a ruthenium complex with a new methyl 9-hydroxyphenalene-5-carboxylate ligand

Ruthenium complexes with pyridine ligands have been extensively studied for decades because of their photochemistry and electronic properties. To modulate these properties, several ligands have been combined with the [Ru(bpy)2]2+ fragment to form new coordination compounds. One class that captured attention of our group is the polycyclic aromatic ligands like the phenalenyl unit. These multicyclical systems have interesting electronic properties that can be exploited in catalysis 1, spin memory devices 2, molecular electronics and in thin films. In the present study a ruthenium 2,2'-bipyridine complex was synthetized with a new ligand named methyl 9-hydroxy-1-oxo-1H-phenalene-5-carboxylate (L). The complex [Ru(bpy)2L][PF6] was characterized by 1H NMR, 13C NMR, UV-vis and FTIR spectroscopies. The cyclic voltammetry (CV) of the complex revealed three electrochemical processes. Langmuir-Blodgett films were obtained from a mix of the complex [Ru(bpy)2L][PF6] with stearic acid. The PA curves revealed stable monolayer with collapse pressure above 50 mN.m-1. The UV-vis spectrum of the film show 3-nm bathochromic shift of the π–π* band compared to solution. The CV of the film revealed a reversible process with E1/2=0.76 V attributed to the RuII/III pair. In the next step, a new ligand containing long aliphatic chains is going to be prepared.