Theoretical Study on Optoelectronic Properties of 1,4-Dithiazole-5,10-dihydrophenazine and Its B ← N-Fused...

Recently, Liu et al. reported 1,4-dithiazole-5,10-dihydrophenazine (DTDHP) and its B ← N-fused derivative (DTHDHP-BF), which were expected to show excellent optoelectronic properties (Angew. Chem. Int. Ed. 2022, 61, e202205893). However, their charge-transport performance and luminescence emission mechanisms have not been revealed. In this work, we used density functional theory (DFT) calculations to investigate the optoelectronic properties of DTDHP and DTHDHP-BF and analyzed the influence of the introduction of -BF₂ on the basic parameters governing charge transport and injection in detail. Our calculation results showed that adding -BF₂ could stabilize the frontier molecular orbitals and decrease the reorganization energies associated with electron transport due to the formation of B ← N bonds, and the intermolecular electronic couplings are greatly enhanced owing to the strong intermolecular F···H interactions. Based on the master equation coupled with the Marcus-Hush electron transfer theory, we theoretically predicted the charge transport properties of DTDHP and DTHDHP-BF. The optimum hole mobility (3.87 cm² V^-1 S^-1) and electron mobility (1.52 cm² V^-1 S^-1) of DTHDHP-BF are, respectively, 3 and 9 times as high as the corresponding optimum values of compound DTDHP. Moreover, the assignments of multiple fluorescence bands in the experiment were confirmed by time-dependent density functional theory (TDDFT) calculations. The simulated emission spectra indicate that the experimental fluorescence maxima at 687 nm originates from the S₁ → S₀ transition of the double proton transfer phototautomer (T) of DTDHP, and the shoulder peak at ∼660 nm may be related to the excited-state single-proton transfer phototautomer (T); for DTHDHP-BF, the experimental fluorescence maxima at 687 nm should be attributed to normal Stokes shifted emission, and the shifted fluorescence with a peak at 751 nm originates from the emission of the photodissociation product of DTHDHP-BF.