The (T1) energy of tetracene (1.21 eV) is higher than those of pentacene and molecular oxygen with ca. 0.8 and 0.98 eV, respectively. Hence, diffusive triplet-triplet energy transfer (TTEnT) from tetracene and O2 is thermodynamically feasible. For both mPhTc2 and mAdTc2, all values of ΦΔ exceed 100%, which is an unambiguous indication for intra-SF. Values of ΦΔ are as high as 170% for mAdTc2 and 128%