Enhancement of two-photon absorption cross section and singlet-oxygen generation in porphyrin-cored star polymers

Abstract

We report a newly synthesized polymer of a star-shaped porphyrin compound (TPA-FxP) with four oligofluorene arms at its meso positions with the pronounced enhancement of the two-photon properties and the generation of singlet oxygen by utilizing the two-photon excited fluorescence resonance energy transfer. The steady-state spectra and transient triplet-triplet absorption spectra give evidence that the enhanced two-photon absorption cross section results from not only the through-space energy transfer (Förster) but also the through-bond energy transfer between conjugated peripheral oligofluorene arms and the porphyrin core. The two-photon absorption cross section at 780 nm up to 3360 GM (1 GM = 10 −50 cm 4 ⋅s/photon) of TPA-FxP was obtained, which is comparable to the highest values reported from other similar chemically modified porphyrin core compounds. Furthermore, the enhanced production of singlet oxygen under two-photon absorption conditions is also reported.porphyrin-cored star polymer, two-photon excitation, energy transfer

Photoinduced charge transfer in porphyrin-C60 oligomer

“…Such energy transfer/charge transfer was also observed in other dyads of porphyrin and C 60 complexes, where the porphyrin functioned as an electron donor and C 60 as an acceptor [24][25][26][27][28][29][30]. Furthermore, the transient absorption spectra of P1P2F1 with peaks at 440 nm and 460 nm respectively belonged to the ground state bleach and triplet state absorption of porphyrin [31]. The decay at 440 nm was well fitted with the monoexponential model (  = 432 ns).…”

Organic near‐infrared photodetectors with photoconductivity‐enhanced performance

“…As shown in Figure 4, in the 2TT‐oC6B and PCBM binary films, relatively strong absorption appears at about 500 and 1030 nm. Among them, 520 nm is caused by terephthalic acid (TPA) radicals, [ 41 ] and 1030 nm is due to the absorption of PCBM radicals. [ 42 ] The attenuation of the absorption peak is related to the separation and coincidence of excitons.…”

Giant Star‐shaped meso‐substituted Fluorescent Porphyrins with Fluorenyl‐containing Arms Designed for Two‐photon Oxygen Photosensitization

“…[43] To the best of our knowledge, apart for some asymmetric derivatives presenting one extended meso-aryl group, such as A 1 or A 1 -Zn for instance, [44] no discrete and well defined meso-tetraaryl porphyrins, such as A' n or A" n , [3d, [14][15]45] were ever tested as photosensitizers for 2PA-PDT, although related Pt(II) complexes (A' n -Pt) were recently used for one-photon PDT and oxygen quantification. [14,15] Apart from these few examples, most of the active porphyrin-based 2PA photosensitizers are Zn(II) complexes, for which one (B) or two (C) meso-aryl ring(s) have been replaced by extended arylalkynyl ligand(s), [42,46] a structural modification which allows better conjugation of the central π-manifold with the peripheral arms, because not disrupted by any tilt angle. The net result of [36] Note that this number is presently not changed by metallation, in line with the assumption that the Zn(II) does not contribute to increase the number of effective electrons.…”

“…Interestingly, based on relevant figures of merit, [5e] it appeared from these studies that star‐shaped architectures were the most suited for 2PEF and 2POS [13a] . Actually, to the best of our knowledge, apart from the seminal work of Bo and co‐workers, [3c,d] very few subsequent studies have been conducted on the photosensitizing properties of well‐defined star‐shaped porphyrins incorporating 2,7‐fluorenyl groups at their periphery [14] and virtually none on their 2PA properties [15] . Thus, only few structure‐property relationship emerged for identifying key structural features allowing to optimize 2PEF and 2P‐PDT.…”