Synthesis and Properties of Benzothieno[b]‑Fused BODIPY Dyes

• Published in: Journal of organic chemistry Vol. 81; no. 1; pp. 229 - 237
• Main Authors: Sun, Zuo-Bang, Guo, Man, Zhao, Cui-Hua
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 04.01.2016; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Organic; Physical Sciences; Science & Technology; AZA-BODIPY; SOLAR-CELLS; PHOTODYNAMIC THERAPY; BORON DIPYRROMETHENES; SPECTROSCOPIC PROPERTIES; SINGLET OXYGEN GENERATION; PHOTOPHYSICAL PROPERTIES; FUSED BODIPY; TUNABLE FLUORESCENT DYES; FIELD-EFFECT TRANSISTORS
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/acs.joc.5b02531

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.