On the ambiguity of 1,3,2-benzodiazaboroles as donor/acceptor functionalities in luminescent molecules.

A series of 1,3-bis(perfluoroaryl)-2-(hetero)aryl-1,3,2-benzodiazaboroles, 1,3-(F)Ar2-2-Ar-1,3,2-N2BC6H4 (Ar = Ph, (F)Ar = C6F5 5; Ar = Ph, (F)Ar = 4-C5F4N 6; Ar = Ph, (F)Ar = 4-NCC6F4 7; Ar = 2-C4H3S, (F)Ar = C6F5 8; Ar = 2-C4H3S, (F)Ar = 4-C5F4N 9; Ar = 2-C4H3S, (F)Ar = 4-NCC6F4 10), were synthesised by cyclocondensation of the adducts PhBBr2·PPh3 or 2-thienylBBr2·PPh3 with N,N'-bis(perfluoroaryl)-o-phenylenediamines in the presence of 2,2,6,6-tetramethylpiperidine. Similar treatments of the PPh3 adducts of 4-(1',3'-diethyl-1',3',2'-benzodiazaborolyl)-phenyldibromoborane with the corresponding diamines gave rise to the push-pull compounds, C6H4(NEt)2B-1,4-C6H4-B(N(F)Ar)2C6H4 ((F)Ar = C6F5 11; 4-C5F4N 12) and C6H4(NEt)2B-2,5-C4H2S-B(N(F)Ar)2C6H4 ((F)Ar = C6F5 13; 4-C5F4N 14). The X-ray structures of 8, 11, 12 and 13 were determined.

C,C'-bis(benzodiazaborolyl)dicarba-closo-dodecaboranes: synthesis, structures, photophysics and electrochemistry.

Six new C,C'-bis(benzodiazaborolyl)dicarba-closo-dodecaboranes, 1,A-R2-1,A-C2B10H10, where R represents the group 2-(1,3-Et2-1,3,2-N2BC6H4) or 2-(1,3-Ph2-1,3,2-N2BC6H4) and A is 2, 7 or 12, were synthesized from o-, m-, and p-dicarbadodecaboranes (carboranes) by lithiation and subsequent treatment with the respective 2-bromo-1,3,2-benzodiazaboroles. UV-visible and fluorescence spectra of all carboranes display low energy charge transfer emissions. While such emissions with Stokes shifts between 17,330 and 21,290 cm(-1) are typical for C,C'-bis(aryl)-ortho-carboranes, the observed low-energy emissions with Stokes shifts between 8320 and 15,170 cm(-1) for the meta- and para-isomers are unusual as high-energy emissions are typical for meta- and para-dicarbadodecaboranes.