Regioselective β-acylation of BODIPY dyes with acyl chlorides via electrophilic substitution

A series of β-acyl and β,β'-diacyl BODIPY dyes were efficiently synthesized via electrophilic substitution reactions employing acyl chlorides as acylating agents. This synthetic protocol proceeds under mild conditions with good conversion and complete regioselectivity for the β-position of the BODIPY core. All target compounds were fully characterized by 1 H NMR, 13 C NMR, and HRMS, with compounds 3b and 4a further verified by single-crystal X-ray diffraction. These β-acylated BODIPYs exhibit intense absorption (ε up to 74 000 M -1 · cm -1 ) and strong fluorescence (quantum yields up to 0.89) with slightly blue-shifted emission relative to the parent BODIPYs. DFT calculations reveal that incorporation of electron-deficient carbonyl groups lowers both the HOMO and LUMO energies of 3a and 4a (-6.23/-3.09 eV and -6.39/-3.29 eV, respectively) relative to the parent BODIPY 1a. Notably, the calculated HOMO-LUMO gaps remain nearly unchanged (3.13, 3.14, and 3.10 eV for 1a, 3a, and 4a), in excellent agreement with the experimentally observed optical properties.