文摘
Three consecutive bimolecular reactions are employed to photocatalyze bromide oxidation to bromine. The system consists of a ruthenium(II) complex, [Ru(deeb)b>2b>(dmbpy)]2+ (deeb = 4,4′-diethylester-2,2′-bipyridine; dmbpy = 4,4′-dimethyl-2,2′-bipyridine), 4-bromobenzenediazonium tetrafluoroborate (ArNb>2b>BFb>4b>), and Br–. Varying reagent concentrations allowed us to optimize the sequence of reactions for product formation. The electronically excited ruthenium complex (*Ru) reacts first with ArNb>2b>BFb>4b> to produce a ruthenium(III) (RuIII) intermediate, triggering a subsequent reaction with Br–. Transient absorption measured at 486 and 380 nm provides insight into the time-dependent concentrations of *Ru, RuIII, and Brb>2b>•–. Without interference of back-electron transfer, the rate constant for an equal concentration bimolecular reaction of Brb>2b>•– was determined to be 5 × 109 M–1 s–1. The final products, bromine and tribromide, were spectroscopically characterized, and the turnover number (TON) was 230.