Cyclometalated N,N-dimethylbenzylamine ruthenium(II) complexes [Ru(C6HRRR-o-CH2NMe2)(bpy)(RCN)2]PF6 for bioapplications: synthesis, characterization, crystal structures, redox properties, and reactivity toward PQQ-dependent glucose dehydrogenase |
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Authors: | Ronan Le Lagadec Laura Rubio Rubén A Toscano Rolandas Meškys Michel Pfeffer |
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Institution: | a Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Coyoacán, 04511 México DF, Mexico b Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Coyoacán, 04511 México DF, Mexico c Department of Chemistry, Moscow State University, 119899 Moscow, Russia d Laboratory of Bioanalysis, Institute of Biochemistry, Mokslininku 12, Vilnius 2600, Lithuania e UMR 7513, Laboratoire de Synthèses Métallo-Induites, Université Louis Pasteur, 4, rue Blaise Pascal, 67000 Strasbourg, France f Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA |
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Abstract: | Cyclometalated derivatives of ring-substituted N,N-dimethylbenzylamines with controlled redox potentials as potent mediators of bioelectrochemical electron transport are reported. The cycloruthenation of R1R2R3C6H2CH2NMe2 (R1, R2, R3 = H, Me, tBuO, MeO, NMe2, F, CF3, CN, NO2) by (η6-C6H6)RuCl(μ-Cl)]2 in the presence of NaOH/KPF6 in acetonitrile or pivalonitrile affords cyclometalated complexes (η6-C6H6)Ru(C6HR1R2R3-o-CH2NMe2)(RCN)]PF6 R = Me (1) and R = CMe3 (2)] in good yields. Reactions of complexes 1 and 2 with 2,2′-bipyridine (bpy) in acetonitrile or pivalonitrile result in dissociation of η6-bound benzene and the formation of Ru(C6HR1R2R3-o-CH2NMe2)(bpy)(RCN)2]PF6 R = Me (3) and R = CMe3 (4)]. All new compounds have been fully characterized by mass spectrometry, 1H/13C NMR, and IR spectroscopy. An X-ray crystal structural investigation of complex 1 (R1/R2/R3 = H/H/H) and two complexes of type 3 (R1/R2/R3 = MeO/H/H, MeO/MeO/H) has been performed. Acetonitrile ligands of 3 are mutually cis and the σ-bound carbon is trans to one of the bpy nitrogens. Measured by the cyclic voltammetry in MeOH as solvent, the redox potentials of complexes 3 for the RuII/III feature cover the range 320-720 mV (versus Ag/AgCl) and correlate linearly with the Hammett constants. Complexes 3 mediate efficiently the electron transport between the active site of PQQ-dependent glucose dehydrogenase (PQQ = pyrroloquinoline quinone) and a glassy carbon electrode. Determined by cyclic voltammetry the second order rate constant for the oxidation of the reduced (by d-glucose) enzyme active site by RuIII derivative of 3 (R1/R2/R3 = H) (generated electrochemically) is as high as 4.8 × 107 M−1 s−1 at 25 °C and pH 7. |
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Keywords: | Cyclometalation Ruthenium complexes Electrochemistry Electron transfer Kinetics PQQ-dependent glucose dehydrogenase |
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