Synthetic, Structural, Photophysical and Computational Studies on π‐Conjugated 1,3,2‐Benzodiazaboroles with Carbazole Building Blocks

Abstract

AbstractThe reaction of the N‐lithiated 3,6‐di‐tert‐butyl‐carbazole (2) with 2‐bromo‐1,3‐diethyl‐1,3,2‐benzodiazaborole (1a) and 2‐bromo‐1,3‐diphenyl‐1,3,2‐benzodiazaborole (1b) afforded the 2‐N‐carbazolyl‐functionalized benzodiazaboroles 3a and 3b as colourless solids in 77 and 73 % yield, respectively.Synthesis of 2[5′‐N‐carbazolyl‐2′‐thienyl]‐1,3‐diethyl‐1,3,2‐benzodiazaborole (5a) was effected by lithiation of N‐(2‐thienyl)carbazole (4) and subsequent reaction with equimolar amounts of 1a, and 5a was obtained in 68 % yield. Similarly,2[5′‐N‐carbazolyl‐2′‐thienyl]‐1,3‐diphenyl‐1,3,2‐benzodiazaborole (5b) was prepared from lithiated 4 and 1b in 62 % yield. Compounds 3a,b and 5a,b are characterized by elemental analyses, IR and NMR spectroscopy (1H, 11B, 13C) and mass spectrometry. The molecular structures of 3a and 5a were elucidated by X‐ray diffraction analysis. These borylated systems show intense blue luminescence. The spectroscopic results were reproduced by TD‐DFT calculations at the [B3LYP/6‐311G (d,p)] level of theory.