Preparation and electrochemical and photoelectrochemical properties of a covalently self-assembled monolayer film based on a bis-terpyridyl ruthenium(II) complex

A bis-terpyridyl Ru(II) complex of RuII(IPTP)2(ClO4)2 (in which IPTP = 4′-(4-(imidazol-1-yl)phenyl)-2,2′:6′,2″-terpyridine) has been synthesized using a microwave irradiation method, and characterized by elementary analysis, and proton nuclear magnetic resonance, and mass spectroscopy. A RuII(IPTP)2(ClO4)2 based covalently self-assembled monolayer film was prepared and characterized by UV-Vis spectroscopy and cyclic voltammetry. The cyclic voltammograms demonstrated that RuII(IPTP)2(ClO4)2 assembled in the film was redox active with surface-confined characteristics. The photoelectrochemical properties and electron-transfer mechanism of the film were studied. It was found that the RuII(IPTP)2(ClO4)2/ITO electrode film exhibited a large cathodic photocurrent density of 2.72 μA/cm2 while irradiated with polychromatic light (325 nm < λ < 730 nm) at an applied potential of − 0.4 V versus saturated calomel electrode. The photocurrent action spectrum was in agreement with the metal-to-ligand charge-transfer (MLCT) absorption band of RuII(IPTP)2(ClO4)2, indicating that the photocurrent was generated based on MLCT excitation of the RuII(IPTP)2(ClO4)2 in the film. An incident monochromatic photon-to-current conversion efficiency of this monolayer film was calculated to be 1.8% at 500 nm.