Direct observation of the intermolecular triplet–triplet energy transfer from UV-A absorber 4-tert-butyl-4′-methoxydibenzoylmethane to UV-B absorber octyl methoxycinnamate

Triplet energy transfer (TET) is an important photostabilization process for organic UV absorbers, such as 4-tert-butyl-4′-methoxydibenzoylmethane (BM-DBM) and octyl methoxycinnamate (OMC). To characterize interactions between UV absorbers as TET the interactions between BM-DBM and OMC have been studied through measurements of EPR and time-resolved phosphorescence spectra. The EPR Bmin signals and the phosphorescence of OMC were observed through the selective excitation of BM-DBM at 365 nm in EtOH at 77 K. These results indicate that the intermolecular TET occurs from BM-DBM to OMC. This is the first report of the experimental evidence of the TET between the organic UV absorbers.