Weber, Lothar published the artcileSynthetic, structural, photophysical and computational studies of π-conjugated bis- and tris-1,3,2-benzodiazaboroles and related bis(boryl) dithiophenes, Safety of 5,5′-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2,2′-bithiophene, the publication is Dalton Transactions (2009), 1339-1351, database is CAplus and MEDLINE.
π-Conjugated systems with two and three 1,3-diethyl-1,3,2-benzodiazaborolyl end-groups were synthesized in 58-91% yields using established 1,3,2-diazaborole methodologies. The bis(diazaborolyl) compounds contain thiophene -2,5-C4H2S- (2a), dithiophene -5,5′-(2,2′-C4H2S)2– (2b), phenylene -1,4-C6H4– (2c), biphenylene -4,4′-(1,1′-(C6H4)2)- (2d) and dioctylfluorene -2,7-(9,9-(C8H7)2C11H6)- (2e) bridges. The three-way linkers in the tris(diazaborolyl) assemblies contain a central phenylene unit -1,3,5-C6H3– linked to the borolyl end groups via thiophene -2,5-C4H2S- (3a), directly bonded (3b) or via phenylene -1,4-C6H4– (3c) units. Mol. structures of 2a, 2b, 2c, 3a, 3b and 3c were determined by x-ray crystallog. studies. These borolylated systems show intense blue/violet luminescence with Stokes shifts of 6200-9500 cm-1 and quantum yields of 0.33 to 0.98. The absorption maxima (296-351 nm) of these assemblies are reproduced well by TD-DFT computations (B3LYP/6-31G*), and arise from strong, low energy HOMO-LUMO transitions. From MO computations on optimized geometries of these diazaborolyl systems, the LUMO is located mainly on the thiophene/benzene bridge (66-92%) while the HOMO is largely benzodiazaborolyl in character (53-83%). The S1←S0 absorption bands are thus assigned to π(diazaborolyl)-π*(thiophene/benzene) transitions. Computations on related bis(boryl) dithiophenes [with diarylboryl e.g. Ph2B, Mes2B, (C6F5)2B and FMes2B (Mes = 2,4,6-Me3C6H2; FMes = 2,4,6-(CF3)3C6H2), dioxaborolyl and other diazaborolyl groups] reveal strong, low energy UV-visible absorption bands arising from π(thiophene)-π*(thiophene) transitions, with increasing B participation in the LUMO of the diarylboryl and especially the highly fluorinated systems.
Dalton Transactions published new progress about 239075-02-6. 239075-02-6 belongs to alcohols-buliding-blocks, auxiliary class Thiophene,Boronic acid and ester,Boronate Esters, name is 5,5′-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2,2′-bithiophene, and the molecular formula is C5H9IO2, Safety of 5,5′-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2,2′-bithiophene.
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