Highly and Deep Red-Luminescent Bisphenylamine-Appended Benzocarcogendiazole Fluorophores

Benzocarcogendiazole units have been frequently utilized for optoelectronics such as organic solar cells because of their robustness, rigidity, and band-gap tunability based on their strong electron-withdrawing properties. Focusing on the luminescent characteristics, these molecules have been utilized to demonstrate highly sensitive chromisms because of the potential of charge transfer. Here, we demonstrate deep red-emissions in bis(4-tert-butylphenyl)amine-appended benzocarcogendiazole-based donor-acceptor-donor (D-A-D) fluorophores, namely 1 and 2. Because benzocarcogendiazole and bis(4-tert-butylphenyl)amine serve as strong electron acceptor and donor, respectively, strong intramolecular charge transfer (ICT) enables long wavelength of photoluminescence (PL) even in the small molecular weight. Although photoluminescence (PL) in long wavelength tends to exhibit quite low absolute PL quantum efficiency (Φ_PL), the values of solutions 1 and 2 are quite high (up to 50 %). According to X-ray crystallographic characterizations and DFT calculations, these high Φ_PL values are attributable to the segregated π-planes of benzocarcogendiazole units, which is induced by the bulky substituents of bis(4-tert-butylphenyl)amines.