Sun Zuo-Bang, Guo Man, Zhao Cui-Hua
School of Chemistry and Chemical Engineering, Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, Shandong University , Jinan 250100, People's Republic of China.
J Org Chem. 2016 Jan 4;81(1):229-37. doi: 10.1021/acs.joc.5b02531. Epub 2015 Dec 14.
Two benzothieno[b]-fused BODIPYs, BT-BODIPY and BBT-BODIPY, in which one parent BODIPY core is fused with one and two benzothieno rings, respectively, were synthesized from BODIPYs substituted with 2-(methylsulfinyl)phenyl at the β-position. The first H2SO4-induced cyclization and deborylation afforded benzothieno[b]-fused dipyrrin derivatives, which can easily complex with BF3·OEt2 to form the desired benzothieno[b]-fused BODIPYs. It was revealed that the fusion of the benzothieno ring is more effective at extending conjugation than simple attachment of the 2-(methylthio)phenyl substituent, which presumably results from conformational restriction. Compared with the corresponding unstrained SPh-BODIPY and BSPh-BODIPY, which contain one and two 2-(methylthio)phenyl groups at the β-position, BT-BODIPY and BBT-BODIPY display red shifted absorption, increased absorptivity, and fluorescence efficiency. Furthermore, the ring fusion is also helpful to increase stability of the formed cation in BBT-BODIPY. Thus, BBT-BODIPY exhibits very intriguing properties, such as intense absorption and emission in the red region, very sharp emission spectra, and reversible oxidation and reduction potentials.
合成了两种苯并噻吩并[b]稠合的BODIPY，即BT-BODIPY和BBT-BODIPY，其中一个母体BODIPY核分别与一个和两个苯并噻吩环稠合，它们由在β位被2-(甲基亚磺酰基)苯基取代的BODIPY合成。第一步硫酸诱导的环化和脱硼反应得到苯并噻吩并[b]稠合的二吡咯衍生物，其能很容易地与BF3·OEt2络合形成所需的苯并噻吩并[b]稠合的BODIPY。结果表明，苯并噻吩环的稠合在扩展共轭方面比简单连接2-(甲硫基)苯基取代基更有效，这可能是由于构象限制导致的。与相应的在β位含有一个和两个2-(甲硫基)苯基的非张力SPh-BODIPY和BSPh-BODIPY相比，BT-BODIPY和BBT-BODIPY表现出吸收峰红移、吸光度增加和荧光效率提高。此外，环稠合也有助于提高BBT-BODIPY中形成的阳离子的稳定性。因此，BBT-BODIPY表现出非常有趣的性质，如在红色区域有强烈的吸收和发射、非常尖锐的发射光谱以及可逆的氧化和还原电位。
