Manipulating Charge‐Transfer States in BODIPYs: A Model Strategy to Rapidly Develop Photodynamic Theragnostic Agents

Abstract

On the basis of af amily of BINOL (1,1'-bi-2naphthol)-based O-BODIPY (dioxyboron dipyrromethene) dyes, it is demonstrated that chemical manipulation of the chromophoric push-pull character,b yp laying with the electron-donating capability of the BINOL moiety (BINOL versus 3,3'-dibromoBINOL) and with the electron-acceptor ability of the BODIPY core (alkyl substitution degree),i sa workable strategy to finely balance fluorescence( singletstate emitting action) versust he capability to photogenerate cytotoxic reactive oxygen species( triplet-state photosensitizing action). It is also shown that the promotiono f as uitable charge-transfer character in the involved chromophore upon excitation enhances the probability of an intersystem crossing phenomenon, whichi sr equired to populate the triple state enabling singlet oxygen production. The reported strategy opens up new perspectivesf or rapid development of smartera gentsf or photodynamic theragnosis, including heavy-atom-freea gents, from as elected organic fluorophore precursor.

Recent Strategies to Develop Innovative Photosensitizers for Enhanced Photodynamic Therapy

“…Ortiz et al. also developed several push–pull PSs ( 242 ) based on 3,3′-dibromo BINOL as an electron donor and a BODIPY core as an electron acceptor with a 1 O 2 quantum yield ranging from 0.11–0.32, which has the potential for the development of a PDT agent from selected organic fluorophore precursors …”

Halogen-free photosensitizers based on meso-enamine-BODIPYs for bioimaging and photodynamic therapy

“…To address these drawbacks, the design of heavy atom-free photosensitizers is currently a very active research field. 40–53 One of the strategies relies on the combination of electron donor (D) and acceptor (A) moieties to induce charge transfer (CT) states, which can act as mediators between singlet and triplet excited states by two different pathways: radical pair intersystem crossing (RP-ISC) 54,55 or spin–orbit charge transfer intersystem crossing (SOCT-ISC), 56–59 Fig. 1B.…”

Near-infrared absorbing aza-BODIPYs with 1,7-di-tert-butyl groups by low-barrier rotation for photothermal application

“…[4][5][6][7][8][9][10] These applications all directly reflect one or more of three pathways to return to the ground state from the excited state, that is, emitting photon (fluorescence), following non-radiative relaxation pathways (heat generation), or exiting from the singlet to the triplet state (T1) via intersystem crossing (ISC) to generate singlet oxygen with oxygen. [11][12][13][14][15] Recently, PTT and PDT, which correspond to the latter two pathways, have aroused widespread interest in phototherapeutic field. Therefore, the closing of the fluorescent channel is a key to establish the application for PTT and/or PDT.…”