We next selected the pinacol coupling of benzaldehyde as a model reductive quenching reaction, which involves PET from the sacrificial reductant, diisopropylethylamine (DIPEA), to the of PC* to form PC -• , which then reduces benzaldehyde with the assistance of DIPEA +• (Figure ). Table Under air, the delayed fluorescence is completely quenched in both compounds while the tp decrease modestly 7.0 and 6.2 ns for DABNA-1 and CzBN, respectively. Thus, there seems to be no correlation between competitive quenching of the excited state of these two PCs by O2 and reaction yield, and it is at present unclear where there is such a divergence in reactivity between these two PCs under air other than the general photoinstability of CzBN.