1,3,2-Diazaborolyl-functionalized thiophenes and dithiophenes: synthesis, structure, electrochemistry and luminescence

Abstract

Reaction of 2-bromo-1,3-diethyl-1,3,2-benzodiazaborole (1) with equimolar amounts of thienyl lithium or 2,2-dithienyl lithium led to the generation of benzodiazaboroles 2 and 3 which are functionalized at the boron atom by a 2-thienyl or a 5-(2,2-dithienyl) unit. Similarly 2-bromo-1,3-diethyl-1,3,2-naphthodiazaborole (4) and thienyl lithium or 2,2-dithienyl lithium afforded the naphthoborolyl-substituted thiophene 5 or dithiophene 6. Treatment of 2,5-bis(dibromoboryl)-thiophene 7 with 2 eq. of tBuN=CH-CH=NtBu in n-hexane followed by sodium amalgam reduction of the obtained bis(diazaborolium) salt 8 gave the 2,5-bis(diazaborolyl)thiophene 9. The 2,5-bis(diazaborolidinyl)-thiophene 10 resulted from the cyclocondensation of 7 with 2 eq. of N,N-di-tert-butylethylenediamine in the presence of NEt3. Analogously, cyclocondensation of 7 with N,N-diethylphenylenediamine gave the bis(benzodiazaborolyl) functionalized thiophene 11. The novel compounds were characterized by elemental analysis and spectroscopy (1H-, 11B-, 13C-NMR, MS and UV-VIS). The molecular structure of 3 was elucidated by X-ray diffraction. Cyclovoltammograms show an irreversible oxidation wave at 298-598 vs. Fc/Fc+. The borolylated thiophenes and dithienyls show intense blue luminescence with Stokes shifts of 30-107 nm.

Diazaborolyl-boryl push–pull systems with ethynylene–arylene bridges as ‘turn-on’ fluoride sensors

“…Bond lengths and bond angles within the benzodiazaborole part of 3 are similar to those of numerous diazaboroles studied before. 17,19,22,[25][26][27] The molecule 12 may be described as a benzodiazaborole which is connected with a 2-thienylethynyl unit via the B(1)-C(11) single bond of 1.520(3) Å. Both heterocycles are linked by an essentially linear ethynyl bridge with a triple bond C(11)-C(12) bonds of 1.207(3) Å and angles B(1)-C(11)-C(12) and C(11)-C(12)-C(13) of 176.4(2)° and 178.2(3)°, respectively.…”

“…4j These are looked at here for comparison with the bisdiazaborole 20 to estimate the affinity strengths of the second BMes 2 group towards the fluoride anion. XI [24] XII [24,25] XIII [24] XIV [25] XV [5j]…”

“…For synthetic reasons the 1,3-diethyl-1,3,2-benzodiazaborole unit is the most frequently employed representative, and compounds containing this group as a substituent are moderately air-stable. 16,[22][23][24][25][26][27] As the BMes 2 group is known as an effective acceptor (A) and the benzodiazaborolyl unit has been suggested to be a π-donor (D) 27 the novel "push-pull"-systems [D-bridge-A] with 1,4-phenylene-, 4,4'-biphenylene-, 2,5-thiophene-and 5,5'-dithiophene-scaffolds (I-IV, Chart I) have been investigated recently. 28 Photophysical studies on these compounds reveal blue-green fluorescence and Stokes shifts for the first three representatives of 7820-9760 cm -1 in THF, whereas the Stokes shift for the last compound is significantly smaller (5510 cm -1 in THF).…”

Selective Reduction of Carbonyl Amides: Toward the First Unsymmetrical Bischelating N‐Substituted 1,2‐Diamino‐4,5‐di­amidobenzene

“…Note that only the unsubstituted amino analog was recently described [molecule 5 with R 1 = H and R 2 = C(O)OEt] as an intermediate in the preparation of ligands containing salophen and bis(oxamato) cavities. [18,19] Systems of type 5 combine the structural elements of 6 and 7, which have generated much interest in organic, [20][21][22] organometallic, [23][24][25][26][27][28] and/or supramolecular chemistry [29,30] owing to the ability of the amino and/or amido groups to act as nucleophiles, coordinating moieties, or H-donor sites.…”

Design organischer optoelektronischer Materialien durch laterale Borylsubstitution

“…[ Seit den 1990er Jahren konzentrierte sich die Forschung auf die Einführung von Borylgruppen in organische Strukturen für Anwendungen wie nichtlineare Optik, [12] Zweiphotonenabsorption, [13] Lumineszenz, [14] organische elektronische Bauelemente, [15] Fluoridsensoren [16] und die SaccharidDetektion. [17] Die Einführung in Polymergerüste ergibt Materialien, die lumineszieren und deren Farbe einstellbar ist.…”