Derivatives of carbazole and chloropyridine exhibiting aggregation induced emission enhancement and deep-blue delayed fluorescence

New carbazole-chloropyridine donor-acceptor compounds were obtained with the yields of 49-77% by a one-step catalyst-free nucleophilic substitution reaction of pentachloropyridine and carbazole. The structures of the compounds were confirmed by H-1, C-13 NMR and IR spectroscopy and mass spectrometry. X-ray single crystal diffraction analysis was performed for monosubstituted derivative of pentachloropyridine. Computational studies revealed high theoretic triplet energy levels with small singlet-triplet energy gaps. Electrochemical, thermal and photophysical properties of the compounds were studied. The solid films of the compounds exhibited fluorescence in the range of 435-465 nm. Disubstituted and trisubstituted derivatives formed molecular glasses with glass transition temperatures of 93 degrees C and 134 degrees C, respectively. Singlet-triplet energy splitting of the obtained compounds were in the range from 0.06 eV to 0.31 eV depending on the number of attached carbazolyl moieties. Triplet energy levels of the compounds were estimated to be in the range from 3.05 eV to 3.08 eV. The mono-substituted derivative exhibited aggregation induced emission enhancement and thermally-activated delayed fluorescence. It exhibited deep blue emission with chromaticity coordinates of (0.17, 0.13) and 16% photoluminescence quantum yield in the solid state.