Calixarenes as High Temperature Matrices for Thermally Activated Delayed Fluorescence: C(70) in Dihomooxacalix[4]arene.

Thermally activated delayed fluorescence (TADF) of (12)C(70) and (13)C(70) was observed up to 140 °C in a p-tert-butyldihomooxacalix[4]arene solid matrix, a temperature range significantly higher than that of previous TADF quantitative studies. An effective singlet-triplet energy gap of 29 kJ/mol and triplet formation quantum yields of 0.97 and 0.99 were measured for (12)C(70) and (13)C(70), respectively. The photophysical properties of the two fullerenes in this new matrix are comparable to those obtained in polystyrene at a lower temperature range. Calixarenes are proposed to be suitable matrices for high temperature TADF studies and applications.