Effects of substitution position on luminescence properties of carbazole-containing monoradicals

Luminescence properties of two regioisomers of carbazole-incorporated triarylmethyl radicals were compared. These radicals exhibited distinct emission wavelengths, photoluminescence efficiencies, and degrees of charge-transfer character. Density functional theory (DFT) and time-dependent DFT calculations revealed that these differences originate from the presence or absence of orbital coefficients at the carbon atom of the carbazole skeleton that covalently links to the triarylmethyl radical framework. Thus, the bonding position plays a crucial role in modulating the luminescence properties of organic radicals.