Title
Donor Influence on the Optoelectronic Properties of N-Substituted Tetraphenylimidazole Derivatives
Author
Matulaitis, Tomas, Paloma L. dos Santos, Youichi Tsuchiya, David B. Cordes, Alexandra M. Z. Slawin, Chihaya Adachi, Ifor D. W. Samuel, and Eli Zysman-Colman
Year
2023
Journal
ChemistrySelect
Abstract
Three new 1,2,4,5-tetraphenylimidazole derivatives, 9,9-dimethyl-10-(4-(2,4,5-triphenyl-1H-imidazol-1-yl)phenyl)-9,10-dihydroacridine (DMAC-TPI), 10-(4-(2,4,5-triphenyl-1H-imidazol-1-yl)phenyl)-10H-phenoxazine (PXZ-TPI), and 10-(4-(2,4,5-triphenyl-1H-imidazol-1-yl)phenyl)-10H-phenothiazine (PTZ-TPI), bearing different electron donors at the N1 position of the imidazole were synthesised and characterised. DMAC-TPI and PXZ-TPI showed narrow emission at ?PL of 388 and 418?nm in toluene, and in doped films in Zeonex polymer (1?wt.%) at ?PL 381 and 407?nm, respectively, with a full width at half maximum (FWHM) ranging 0.42-0.44?eV. DMAC-TPI and PXZ-TPI are predicted to show very low oscillator strength for the low-energy transitions, which aligns to the observed low photoluminescence quantum yields. Both molecules showed a singlet-triplet energy gap (?EST of around 1.2?eV) that is much too large to enable reverse intersystem crossing and thermally activated delayed fluorescence. Connecting a donor group to TPI at the N1 position can lead to room temperature phosphorescence (RTP), as the example of PTZ-TPI showed.
Instrument
FP-8600
Keywords
Organic Semiconductor, Blue-emitting compound