Tuning Electron density at Ruthenium Amine/Amido complexes

CATTANEO, MAURICIO

Blowing Rock

Congreso; 3rd International Conference on Proton Coupled Electron Transfer; 2018

University of Noth Carolina at Chapel Hill

Managing several electron equivalents is relevant to both biological systems and technological applications. Reactions with even number of proton and electrons are necessary to avoid high energy intermediate and radicals. Ruthenium complexes have a broad chemistry for multiple redox reactions as water oxidation catalysts. Ruthenium amine/amido systems show a rich chemistry including several oxidation states.1-3 Proton coupled electron transfer reactions between oxidation state II and IV1,3,4 and at higher oxidation states showed to form nitroso-ruthenium complexes by higher reactivity at amido group,1-3 but few systems were studied. A family of compounds from these parent structures is proposed to reveal new aspects of reactivity, stability and energetics of all oxidation states available and reactivity.Synthesis of complexes [RuII(L)(en*)2](PF6)2 and [RuIV(L)(en*-H)2](PF6)2 with L = 1,10-phenanthroline (phen) , 4,4?-dimethyl-2,2?-bipyridine (DMB) and 4,4?-domethoxy-2,2?-bipyridine (DMOB) is reported together with spectroscopic and analytical characterization. UV-vis spectra of complexes in with 4,4?-disubstitued bpy ligands shows two low absorption bands at ~520 nm and ~380nm in RuII and ~420nm in RuIV, as it was reported for bpy.1,4 Instead, complex with phen shows a distinct pattern with absorption maxima at 500 nm in RuII state and 410nm in RuIV state. NMR spectra show a distinct resonance for amine/amido proton showing effects of electron donating groups at X2-bpy and phen. Cyclic voltammetry for these series of compounds shows a main process of 2e-/2H+ transfer couple in water solutions. These compounds provide new insights in controlling 2e-/2H+ transfer reactions. References1a) Wong, K.Y.; Che, C. M.; Li, C. K.; Chiu, W. H.; Zhou, Z. Y.; Mak, T. C. W. J. Chem. Soc. Chem. Commun. 1992, 161. b) Chiu, W. H.; Cheung, K. K.; Che, C. M. J. Chem. Soc. Chem. Commun. 1995, 441. c) Chiu, W.-H.; Peng, S.-M.; Che, C.-M. Inorg. Chem. 1996, 35, 3369.2Neill, J.; Nam, A. S.; Barley, K. M.; Meza, B.; Blauch, D. N. Inorg. Chem. 2008, 47, 5314.3Guan, X.; Law, S.-M.; Tse, C.-W.; Huang, J.-S.; Che, C.-M. Chem. Eur. J. 2014, 20, 15122.4Cattaneo, M.; Ryken, S. A.; Mayer, J. M. Angew. Chem. Int. Ed. 2017, 56, 3675.