The decay kinetics were calculated following the method of Tsuchiya et al. (Table ). All materials possess kF and a kISC of the order of 10 7 -10 8 s -1 . The kRISC were estimated to be 9.2 × 10 5 s -1 and 7.8 × 10 5 s -1 for t BuPh-DMAC-TRZ and OMePh-DMAC-TRZ, respectively. These rates are four times faster compared to that of DMAC-TRZ (kRISC = 2.2 × 10 5 s -1 ), and one order of magnitude faster than the kRISC of CF3Ph-DMAC-TRZ, dPh-DMAC-TRZ; the slowest kRISC was observed for CNPh-DMAC-TRZ (Table ). The trend in estimated kRISC values aligns well with the relative magnitude of the ΔEST (Figure ).