1,3,2‐Benzodiazaboroles with 1,3‐Pentafluorophenyl and Tetrafluoropyridyl Substituents as Building Blocks in Luminescent Compounds

Abstract

Keywords: Boron / Diazaboroles / Perfluoroaryls / Photophysics / LuminescenceThe reaction of N- 4Ј-trimethylsilylphenyl-3,6-di-tert-butylcarbazole (3) or N-5Ј-trimethylsilylthien-2Ј-yl-3,6-di-tert-butylcarbazole (4) with boron tribromide and subsequently with triphenylphosphane afforded the dibromoborylphenylcarbazole-phosphane adduct 5 or its thiophene derivative 6 as colorless solids. These adducts were converted into the new benzodiazaborole derivatives 7 and 8 by treatment with N,NЈ-bis(pentafluorophenyl)-o-phenylenediamine (1) and 2,2,6,6-tetramethylpiperidine in hot toluene (52 or 45 % [a]4268 yield). The analogous compounds 9 and 10 were obtained by condensing precursors 5 and 6 with bis(N,NЈ-2,3,5,6-tetrafluoropyrid-4-yl)-o-phenylenediamine (2) in the presence of the piperidine derivative in 35 and 16 % yield. Compounds 7-10 were characterized by NMR spectroscopy ( 1 H, 11 B, 13 C, 19 F) and mass spectrometry. The molecular structure of 8 was elucidated by X-ray diffraction analysis. The borylated systems show intense blue luminescence upon UV irradiation. 4269Scheme 2. Syntheses of o-phenylenediamines 1 and 2.Scheme 3. Syntheses of 5 and 6.

The role of 2,3-dihydro-1-H-1,3,2-diazaboroles in luminescent molecules

“…As a result an "umpolung" of the benzodiazaborolyl unit from a -donor to a -acceptor similar to the dimesitylboryl group was anticipated [55]. For the synthesis of the targeted systems a protocol according to Scheme 5 proved to be of advantage.…”

“…These adducts react with one equivalent of o-phenylene diamine 72 [56] and two equivalents of 2,2,6,6-tetramethylpiperidine (TMP) in hot toluene to afford the benzodiazaborole derivatives 73 and 74, respectively (Scheme 16) [55].…”

“…The synthesis of the phenylene-bridged derivative 65 was based on a magnesium assisted coupling precursor 64 with 20 in the presence of LiCl [54], whereas the N,N -diphenyl analog 66 was accessible from 64 via lithiation and the subsequent quenching with 61 [55]. Compounds 68 and 69 featuring a 2,5-thiophene-diyl linker between the benzodiazaborolyl-and the carbazolyl-units were prepared similarly [53] (Scheme 15).…”

“…Similarly, adducts 70 and 71 were converted into the corresponding benzodiaza-boroles 76 and 77 when reacted with o-phenylene diamine 75 in the presence of two equivalents of the base (Scheme 16) [55]. To understand the interaction of the The next logical step in the quest for novel push-pull molecules with tunable photophysical properties would be the construction of -conducting scaffolds with both the electronwithdrawing fluoroaryl-functionalized benzodiazaborolyl groups and the familiar 1,3-diethyl-1,3,2-benzodiazaborolyl donor as terminal substituents.…”

“…Various donor-and acceptor groups are employed. Bond lengths and interplanar angles of interest of compounds 22 [33], 24, 26 [33], 51-56 [51], 83, 84 [30] with phenyl-based linkers, 27, 28, 30-33 with diphenylacetylene substituents at boron [39], 35, 36, 38-40, 42 with arylacetylide groups [41][42][43] and 44, 45, 46 [33], 49, 50 [46], 57, 58, 60 [51], 68 [53], 74 [55] and 86 [30] with thiophene-derived spacers are listed in Table S1 (Supporting information).…”