We report the synthesis and characterization of RuC7, a complex in which a heme is covalently attached to a [Ru(bpy)3]2+ complex through a -(CH2)7- linker. Insertion of RuC7 into horse heart apomyoglobin gives RuC7Mb, a Ru(heme)-protein conjugate in which [Ru(bpy)3]2+ emission is highly quenched. The rate of photoinduced electron transfer (ET) from the resting (Ru2+/Fe 3+) to the transient (Ru3+/Fe2+) state of RuC7Mb is > 108 s-1; the back ET rate (to regenerate Ru2+/Fe3+) is 1.4 × 107 s-1. Irreversible oxidative quenching by [Co(NH3)5Cl] 2+ generates Ru3+/ Fe3+: the Ru3+ complex then oxidizes the porphyrin to a cation radical (P.+); in a subsequent step, P.+ oxidizes both Fe3+ (to give Fe IV=O) and an amino acid residue. The rate of intramolecular reduction of P.+ is 9.8 × 103 s-1; the rate of ferryl formation is 2.9 × 103 s-1. Strong EPR signals attributable to tyrosine and tryptophan radicals were recorded after RuC7MbM3+ (M = Fe, Mn) was flash-quenched/frozen.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry