Air- and Water-Stable, Fluorescent Oligomers of 9,10-Dihydro-9,10-diboraanthracene

Air- and water-stable, π-conjugated [−donor–acceptor−] n oligomers containing thiophene fragments as donors and 9,10-dimesityl-9,10-dihydro-9,10-diboraanthracene (DBA(Mes) 2 ) as acceptor units were prepared through Stille-type C–C-coupling protocols. The reaction between 2,6-dibromo-DBA(Mes) 2 ( 1 ), 2,7-dibromo-DBA(Mes) 2 ( 2 ), 2-bromo-6,7-dimethyl-DBA(Mes) 2 ( 3 ), and 2,5-bis(trimethylstannyl)thiophene ( 7 ) furnished monodisperse, short-chain model systems 8 0 (2 × DBA(Mes) 2, 1 × 2,5-thienylene) and 8 1 (3 × DBA(Mes) 2, 2 × 2,5-thienylene) after GPC separation. In the absence of 3, the oligomerization of 1 / 2 with 7 provided analogous longer chain macromolecules 9 (MALDI–MS reveals up to 7 repeating units; GPC indicates also significantly longer chains). UV/vis absorption spectroscopy suggests that the obtained chain lengths of 9 are already sufficient to reach the maximum effective conjugation length (the lower limit of the HOMO–LUMO band gap corresponds to 2.3 eV). 9 gives rise to a dark orange fluorescence, both in C 6 H 6 solution (ϕ f = 47%) and as thin film (ϕ f = 13%).