Synthesis and Characterization of New Mononuclear Ru (II) PolypyridylComplexes with Catalytic Activity

New chloro and aqua mononuclear Ru(II) complexes of formula [Ru(tpy/tptz)(dpp)Cl]PF₆ and [Ru(tpy/tptz)(dpp)H₂O](PF₆)₂ ( 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) were synthesized and characterized. They are active for water oxidation catalysts at pH=1 using Ce(IV) sacrificial oxidant.

Abstract

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 (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 the complex [Ru(tptz)(dpp)Cl]PF₆, the complete structure was determined by X-ray diffraction. Catalytic studies of aqua-complexes revealed that they are active for the water oxidation reaction at pH 1 using cerium ammonium nitrate (CAN) as a sacrificial oxidant. Also, we were able to establish the reaction mechanism and rate constants of each stage of the catalytic cycle, turnover frequencies (TOFs), and turnover numberes (TONs). The experimental TON values for the aqua complexes were very close to the theoretical value of 7.5, indicating a high degree of recovery. DFT and TD-DFT calculations of electronic states for all complexes were consistent with experimental results and allowed the complete assignment of their UV-Visible bands and redox states.

Zum Volltext