BODIPY‐Pyrene and Perylene Dyads as Heavy‐Atom‐Free Singlet Oxygen Sensitizers

Abstract

, et al. (2018) BODIPY-pyrene and perylene dyads as heavy atom-free singlet oxygen sensitizers. ChemPhotoChem.

Spin–Orbit Charge‐Transfer Intersystem Crossing (ISC) in Compact Electron Donor–Acceptor Dyads: ISC Mechanism and Application as Novel and Potent Photodynamic Therapy Reagents

“…Molecular structure design and synthesis of the compact electron donor/acceptor dyads Recently,aperylene-Bodipy dyad was reported to show charge transfer inducedI SC, [51,53] but the photophysical properties were not studied in detail, and the ISC mechanism wasn ot confirmed with TREPR spectroscopy.T hese resultsi nspired us to prepare perylene-Bodipy compactd yads with orthogonal and non-orthogonal geometry to study the possibility of SOCT-ISC and the relationship betweens tructure and ISC efficiency in these molecular systems (Scheme 1).…”

“…Although different studies have recently emerged concerning this mechanism, SOCT‐ISC is still in its infancy. First, although a few electron donor/acceptor dyads that are able to undergo SOCT‐ISC have been reported, the interplay among different ISC mechanisms (e.g., SOCT‐ISC, RP‐ISC and others) remains unclear. Pulsed laser excited time‐resolved electron paramagnetic resonance (TREPR) spectroscopy, a powerful method to distinguish the different ISC mechanisms by studying the electron spin polarization (ESP) of the triplet state, was not applied to the recently reported Bodipy electron donor/acceptor dyads .…”

Heavy-atom-free BODIPY photosensitizers with intersystem crossing mediated by intramolecular photoinduced electron transfer

“…Compounds 35-38 ( Figure 8) were shown to generate singlet oxygen in polar solvents (Table 2) with ΦΔ values depending on the number of alkyl substituents in the BODIPY subunit (Table 2). 64 All dyads of this series have close to orthogonal geometries (dihedral angles 81-89°). Highly efficient sensitization was observed for alkylunsubstituted 35 (ΦΔ = 0.75 in ethanol), which exhibited an ultrafast electron transfer (k -1 = 0.49 ps) from the pyrene to the BODIPY subunit.…”

“…Phenylene-separated BODIPY-anthracene and pyrene dyads 54 and 55 were reported to undergo PET in polar solvents, however both exhibit very low singlet oxygen quantum yields ( ≈ 0.01), evidencing low efficiency of the triplet state formation. 59,64 The dihedral angle between the subunits in 54 is approximately 53°, suggesting that SOCT-ISC is not operative in this system. Majima and co-workers described structurally similar BODIPYanthracene dyads 56a-b, which do not exhibit PET in dimethyl sulfoxide and methanol.…”

“…BODIPY-perylene dyad 41 was reported to have rather low sensitization efficiency in ethanol ( = 0.13). 64 Mani and coworkers showed that the electron transfer from perylene to the BODIPY subunit in 41 is thermodynamically favourable in polar solvents (e.g. GPET = -0.031 eV in acetonitrile).…”