Highly Emissive Organic Solids Containing 2,5-Diboryl-1,4-phenylene Unit

We disclosed a series of π-conjugated systems containing 2,5-bis(dimesitylboryl)-1,4-phenylene as the core unit and electron-donating amino groups at the terminal positions. The extension of the pπ−π* conjugation in the diborylphenylene moiety along the short axis of the π-conjugated framework as well as the incorporation of two bulky dimesitylboryl groups at the para-positions makes this moiety act as a unique bulky π-electron-accepting unit. As a consequence, these systems behave like donor−acceptor−donor quadrupolar π-electron systems and show a large solvatochromism in the fluorescence spectra. Moreover, these organoboron π systems exhibit intense fluorescence even in the solid state with the quantum yields of 0.73−0.90.