a All data was measured in MeCN unless otherwise noted. b Measured in butyronitrile. C FPL in solution were measured using the relative method 18 using fac-Ir(ppy)3 as a standard (Fr = 78% in MeCN). Taken from the onset of the emission spectrum at 77 K. e kr = FPL/taverage. f knr = (1-FPL)/t average.