Fluorescence from 3,5-diphenyl-8-CF-BODIPYs with amino substituents on the phenyl rings: Quenching by aromatic molecules.

The photoluminescence from n-hexane solutions of the dyes obtained by the introduction of amino groups into the meta position of the phenyl rings of 3,5-diphenyl-8-CF-BODIPY was found to be strongly quenched by some aromatic molecules (benzene and toluene). On the contrary, the introduction of an amino group into the para position does not lead to significant quenching. The quenching of photoluminescence from the meta derivatives obeys the mixed static + dynamic mechanism. Temperature-dependent time-resolved fluorescence measurements were performed to determine the Stern-Volmer constants of the static and dynamic components of quenching. It follows from these data that the binding energy between luminophore and toluene molecules is about 5.0 kcal/mol in the ground state and larger than 3.4 kcal/mol in the excited state. Complexation with toluene facilitates the intramolecular charge transfer in the BODIPY derivatives with the meta position of the amino groups, resulting in photoluminescence quenching.