Synthesis of pyrrolyl-BODIPY dyes through regioselective SN Ar reactions and application as a fluorescent sensor for fluoride anion

Abstract

Two pyrrolyl-BODIPY dyes with 3,5-di-[Formula: see text]-butyl-4-hydroxyphenyl group were synthesized through stepwise S[Formula: see text]Ar reactions of 3,5-dibromoBODIPYs, which were used as a fluorescent sensor for basic anions. The intermediate pyrrolyl-BODIPYs 2a–2b were regioselectively synthesized through an efficient S[Formula: see text]Ar reaction between 3,5-dibromoBODIPY 1a and pyrroles. The target pyrrolyl-BODIPYs 3a–3b with a 3,5-di-[Formula: see text]-butyl-4-hydroxyphenyl group at 3-position and a pyrrole substituent at 5-position were obtained through a second S[Formula: see text]Ar reaction between pyrrolyl-BODIPYs 2a–2b and high steric hindrance 2,6-dibutylphenol in 90% and 88% yields, respectively. In contrast, the reaction between pyrrolyl-BODIPYs 2a–2b and phenol gave pyrrolyl-BODIPYs 3c–3d with phenoxy substituent at 3-position. These pyrrolyl-BODIPYs 3a–2d show strong, sharp absorptions (551–604 nm) and emissions (564–634 nm) with high fluorescence quantum yields up to 0.86 in dichloromethane. Importantly, the 3,5-di-[Formula: see text]-butyl-4-hydroxyphenyl group of pyrrolyl-BODIPY 3a showed a turn-off fluorescent response toward fluoride anion.