J-Aggregates of BODIPYs: Heat-Induced Fluorescence Enhancement via Polarity-Modulated Photoinduced Electron Transfer

Year: 2026

Authors: Bertocchi F., Ricci A., Patalag LJ., Rottger SH., Huu DKAP., Iagatti A., Werz DB., Lapini A., Di Donato M.

Autors Affiliation: Univ Parma, Dipartimento Sci Chim, Sci Vita & Sostenibil Ambientale, I-43121 Parma, Italy; Albert Ludwigs Univ Freiburg, Inst Organ Chem, D-79104 Freiburg, Germany; European Lab Nonlinear Spect LENS, I-50019 Florence, FI, Italy; CNR INO, I-50019 Florence, FI, Italy; CNR ICCOM, I-50019 Florence, FI, Italy.

Abstract: The ability to switch emission between bright and dark states through external stimuli is a key requirement for the design of adaptive optoelectronic materials. Here we demonstrate that covalently linked oligo-BODIPYs exhibit an unusual competition between exciton delocalization and polarity-driven reductive photoelectron transfer (rPET). While the nonfluorescent monomer dissipates excitation energy through rPET between the BODIPY core and a meso aniline substituent, J-aggregation in the oligomers enhances radiative decay in nonpolar environments. Using temperature-dependent fluorescence and ultrafast transient absorption spectroscopy, we show that solvent polarity and temperature finely regulate the population transfer between the bright exciton state and the dark charge-transfer (CT) state, with a pronounced dependence on oligomer chain length. Remarkably, lowering the temperature in moderately polar solvents leads to a dramatic decrease in emission intensity as the concomitantly increasing dielectric constant stabilizes the CT state. Our findings establish a general design principle for developing new environment-responsive chromophoric assemblies.

Journal/Review: JOURNAL OF PHYSICAL CHEMISTRY LETTERS

More Information: M.D.D., A.L. and A.I. gratefully acknowledge support from the European Union’s Next Generation EU Program with the I-PHOQS Infrastructure [Nos. IR0000016, ID D2B8D520, and CUP B53C22001750006] Integrated infrastructure initiative in Photonic and Quantum Sciences. A.I., M.D.D., F.B. and A.L. gratefully acknowledge the National Recovery and Resilience Plan (NRRP), Mission 4, Component 2, Investment 1.1, funded by the European Union – NextGenerationEU (Pr oject VISIO – CUP B53D23025290001 – Grant assignment Decree No. P2022ALSMP). A.L. acknowledges support from Ministero dell’Istruzione dell’Universita e della Ricerca Italiano, project LANTERN (PRIN2022-20225NPY8P) and the financial support of University of Parma through the project SFM-CARS, codice MUR_DM737_2022_FIL_PROGETTI_A_LAPINI. This research benefits from the High Performance Computing facility of the University of Parma, Italy.
KeyWords: Triplet Excited-state; Induced Emission; Energy-transfer; Absorption; Frenkel; Dye
DOI: 10.1021/acs.jpclett.6c01387