Synthesis and characterization of New Mononuclear Ru (II) Polypyridine Complexes with Catalytic Activity

In this work we report the synthesis and physicochemical characterization of new chloro and aqua mononuclear Ru (II) complexes of formula [Ru(LLL)(dpp)Cl]PF6 and [Ru(LLL)(dpp)OH2](PF6)2 (with LLL= tpy =2,2’:6’,2’’-terpyridine; tptz=2,4,6-tris(2-pyridyl)-1,3,5-triazine and dpp=2,3-bis(2-pyridil)pyrazine). For complex [Ru(tptz)(dpp)Cl]PF6 was determined the complete structure by X-ray diffraction. Catalytic studies of aqua-complexes revealed that they are active against the water oxidation reaction at pH=1 using cerium ammonium nitrate (CAN) as sacrificial oxidant. Also, we were able to establish reaction mechanism and rate constants of each stage of the catalytic cycle, turnover frequency (TOF) and turnover number (TON). The experimental TON value for the aqua complexes was very close to theoretical value of 7.5, indicating a high degree of recovery. DFT and TD-DFT calculations of complexes were consistent with experimental results and allowed the complete assignment of its UV–Visible bands, and redox states.