Aggregation-Induced Singlet Oxygen Generation: Functional Fluorophore and Anthrylphenylene Dyad Self-Assemblies

Sooyeon Kim; Yang Zhou; Norimitsu Tohnai; Hirotaka Nakatsuji; Michiya Matsusaki; Mamoru Fujitsuka; Mikiji Miyata; Tetsuro Majima

doi:10.1002/chem.201703686

Aggregation-Induced Singlet Oxygen Generation: Functional Fluorophore and Anthrylphenylene Dyad Self-Assemblies

Chemistry. 2018 Jan 12;24(3):636-645. doi: 10.1002/chem.201703686. Epub 2017 Dec 11.

Authors

Sooyeon Kim¹, Yang Zhou¹, Norimitsu Tohnai², Hirotaka Nakatsuji³, Michiya Matsusaki³, Mamoru Fujitsuka¹, Mikiji Miyata¹, Tetsuro Majima¹

Affiliations

¹ The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka, 567-0047, Japan.
² Department of Material and Life Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
³ Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.

PMID: 29105156
DOI: 10.1002/chem.201703686

Abstract

The assembly of monomeric building blocks can manifest the display of new properties, including optical, mechanical, and electrochemical functionalities. In this study, we sought to develop a functional fluorophore self-assembly that can generate reactive oxygen species only when aggregated. With an anthrylphenylene (AP) group, negatively charged and neutral fluorescein units form non-fluorescent H-aggregates in aqueous solution because of the weak intermolecular interaction between the anthracene and fluorescein moieties. In stark contrast, a boron dipyrromethene (BODIPY) and AP dyad produces two-color-emissive aggregates through the formation of an intermolecular charge-transfer (CT) complex between the electron-rich anthracene and electron-deficient BODIPY moieties. Furthermore, to our surprise, the BODIPY and AP dyad aggregates generate singlet oxygen (¹ O₂ ) and photocytotoxicity upon excitation, indicating that the BODIPY-anthracene CT state favors an intersystem crossing process. Based on X-ray crystallographic analysis, the lattice-like molecular packing between the BODIPY and AP moieties was determined to bring about the unprecedented aggregation-induced ¹ O₂ generation (AISG).

Keywords: aggregation; fluorophores; photodynamic therapy; self-assembly; singlet oxygen.