Electron Transfer Photoreduction of 5,7-Diiodo-3-Butoxy-6-Fluorone withTetrabutylammonium Triphenylbutylborate and N,N-Dimethyl-2, 6-diisopropylaniline

摘要

The photoreduction of 5,7-diiodo-3-butoxy-6-fluorone (DIBF) in the presence ofthe electron donors, tetrabutylammonium triphenylbutylborate (BORATE) and N,N-dimethyl-2,6 diisopropylaniline (DIDMA) was studied in acetonitrile solution. The electron transfer rates calculated are 6.7x10( exp 7 )/sec and 1.2x10(exp 8)/sec in the BORATE and DIDMA systems respectively. The dye radical anion DIBF* lambda (sub max =420 nm) formed by the electron transfer reaction is the only product obtained in the BORATE case. However, with DIDMA the dye neutral radical DIBF*, lambda (sub max=36O nm) was detected as the only product. DIBF* formed after protonation of DIBF* by proton transfer from the amino cation radical. This implies that the proton transfer is too fast to measure on the nanosecond time scale. This is the first such observation in these systems. Singlet oxygen formed by oxygen quenching of the dye triplet was found to be quenched by the electron donors via an electron transfer process also. No quenching of DIBF triplet