Imidazole-based excited-state intramolecular proton-transfer (ESIPT) materials: observation of thermally activated delayed fluorescence (TDF).
We report the first observation of thermally activated delayed fluorescence (TDF) from an excited-state intramolecular proton-transfer (ESIPT) molecule, a hydroxyl-substituted tetraphenyl imidazole derivative (HPI-Ac), in degassed solutions as well as in low-temperature organic matrixes. In the absence of oxygen, the blue emission of an identical spectral feature was observed in the nanosecond ( approximately 4.4 ns) and microsecond ( approximately 25 micros) time domains, and the fluorescence intensity increased with temperature. From the temperature dependence of the time-resolved spectra of HPI-Ac, the energy gap between the first-excited singlet state and the lowest triplet state was determined to be 7.6 +/- 0.3 kJ/mol (630 +/- 25 cm-1), and the limiting rate constant of intrinsic reverse intersystem crossing was estimated to be 1.3 (+/-0.5) x 107 s-1.
Park
Sanghyuk
S
Department of Materials Science and Engineering, Seoul National University, ENG 445, Seoul 151-744, Korea.
Kwon
Oh-Hoon
OH
Lee
Young-Shin
YS
Jang
Du-Jeon
DJ
Park
Soo Young
SY
D002627:Chemistry, Physical / Q000379:methods; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000494:pharmacology; D006358:Hot Temperature; D007093:Imidazoles / Q000737:chemistry* / Q000494:pharmacology; D007700:Kinetics; D008956:Models, Chemical; D011522:Protons; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013053:Spectrophotometry / Q000379:methods; D013696:Temperature; D013816:Thermodynamics; D013997:Time Factors
D004791:Enzyme Inhibitors; D007093:Imidazoles; D011522:Protons; C029899:imidazole