pi* level tuning in a series of diimine ligands based on density functional theory: Application to photonic devices

Energy- and electron-transfer processes are very important for artificial p hotosynthesis and a variety of other applications. [(bpy)(2)Ru(PAP)Os(bpy)( 2)](4+) and its oxidized form [(bpy)(2)Ru(PAP)Os(bpy)(2)](5+) perform effic ient photoinduced energy- and electron-transfer processes, respectively (k( en) = 5.2 x 10(7) s(-1), k(et) = 7.2 x 10(6) s(-1)). The introduction of ap propriate donor and acceptor units on the Ru2+ center can improve the lifet ime of the excited state, resulting in a much longer and efficient storage of energy. Nonempirical (density functional) calculations and experimental data are used to predict the best donor and acceptor ligands for improving electron-and energy-transfer processes. Such a result can be extended to al l polynuclear complexes where electronic coupling between the metal centers is very weak.