Ruthenium(II) trisbipyridyl complexes were utilized as catalysts to convert solar energy into halogen formation from halides. Consecutive bimolecular reactions are employed to photocatalyze halide oxidation to halogen. Besides ruthenium catalysts, the system integrates an irreversible electron acceptor, and halide. For bromide oxidation the reaction was performed in acetonitrile solution and ArN2+ was utilized as the quencher. For iodide oxidation, aqueous solution was employed and Co(NH3)5Cl2+ was the quencher. The electronically excited ruthenium complex (*Ru) reacts first with quencher to produce a Ru(III) intermediate. Subsequently Ru(III) intermediate reacts with X- and produces X2-. which leads to the final product of X3- and/or X2. Time-resolved absorptions measured at 453 and 380 nm provide detail information of the concentrations of *Ru, Ru(III), and X2-.. Without the interference of back-electron transfer, the rate constant for equal concentration bimolecular reaction of Br2-. and I2-. were determined as 5 x 109 and ~5 x 108 M-1 s-1, respectively. Final products were identified spectroscopically. The catalytic turn-over numbers for bromide and iodide are 230 and 1325, respectively.

Photoinitiated oxidation of halides to halogen using ruthenium trisbipyridyl complexes as catalysts

2019 Fall National Meeting

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