Photocatalytic Oxidation of Bromide to Bromine.
Three consecutive bimolecular reactions are employed to photocatalyze bromide oxidation to bromine. The system consists of a ruthenium(II) complex, [Ru(deeb)2(dmbpy)]2+(deeb = 4,4'-diethylester-2,2'-bipyridine; dmbpy = 4,4'-dimethyl-2,2'-bipyridine), 4-bromobenzenediazonium tetrafluoroborate (ArN2BF4), 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 ArN2BF4to 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 Br2•-. Without interference of back-electron transfer, the rate constant for an equal concentration bimolecular reaction of Br2•-was determined to be 5 × 109M-1s-1. The final products, bromine and tribromide, were spectroscopically characterized, and the turnover number (TON) was 230.
Department of Chemistry, National Taiwan Normal University , 88 Tingchow Road, Section 4, Taipei 11677, Taiwan.
Kelvin Yun-Da
KY
Tsai
Department of Chemistry, National Taiwan Normal University , 88 Tingchow Road, Section 4, Taipei 11677, Taiwan.
I-Jy
IJ
Chang