Photoswitchable azobenzene functionalized anthraquinone and benzimidazole Ru(II)-p-cymene organometallic complexes

Abstract

A series of five new Ru(II) (η6-p-cymene) organometallic complexes with the incorporation of modified azobenzimidazole and anthraquinone based ligands were synthesized and found to be an excellent photoswitching property in different solvents. The push-pull effect affects the lifetime of the complexes during photoisomerization processes. Upon irradiation at 254 nm UV light, these complexes efficiently undergo the trans ↔ cis isomerization, which is dependant on solvent polarity as well as substituent pattern. In DCM (dichloromethane), two states stable isomers have been found, but in a higher polar solvent (CH3CN), the fast conversion of trans isomer to the cis isomer takes place. However, the cis isomer proceeds slower thermal isomerization to its original trans isomer in dark condition at room temperature with a higher half-life of the complexes. The photoisomerization study has been monitored by using the UV–vis absorption and 1H NMR studies, which indicates that the successful trans ↔ cis isomerization takes place. The coordination of the ruthenium ion successfully alters the electronic properties of ligands. The excellent photoswitching properties and higher half-life of these organometallic complexes are exciting candidates for their applications in catalytic, photonic devices, and medicinal purposes.