Photoinduced intramolecular electron transfer in viologen-linked zinc porphyrins in dimethyl sulfoxide

Abstract

4466system only when the Cr center bears LiL, or stronger ligands but form Cr"P with weaker ligands. The Cr"P products are relatively stable in solution but are sensitive to the presence of 02, which oxidizes them immediately to the Cr'I'P state. The C r l W species, however, are short-lived in protic solvents and undergo disproportionation and protonation to form chlorins in neutral and acid solutions or phloM anions under alkaline conditions. The phlorins are also readily oxidized by O2 to Cr"'P(LIL2). These studies J. Phys. Chem. 1992, 96, 4466-4469 establish the conditions for production of Cr"-porphyrins and permit us to study the reactions of these products with various alkyl radicals that lead to formation of Cr-C bonds. This will be the topic of a future publication.Acknowledgment. This research was supported by the Office of Basic Energy Sciences of the US Department of Energy. We thank Dr. P. Hapiot for helpful discussions.Compounds containing a viologen linked to a zinc porphyrin via methylene groups have been synthesized, and photoinduced intramolecular electron transfer between porphyrin and viologen was observed. The photoexcited singlet state of the porphyrin was quenched by the bonded viologen, the photoexcited triplet state was quenched, and the lifetime of the charge separated species was about 1 ps.

Cyclodextrin-based systems for photoinduced hydrogen evolution

“…[11][12][13][14][15][16][17] Metal complexes have long been explored as photosensitizers for the evolution of hydrogen in combination with different catalysts. [18][19][20][21][22][23][24][25] There is a wide range of molecules that can act as photosensitizers such as organic dyes, inorganic systems as well as organometallic complexes. [26][27][28] In a typical catalytic cycle, the photosensitizer, which has been oxidized by the catalyst, needs to be regenerated by an electron source (sacrificial donor) which is consumed during the hydrogen production.…”

Synthesis and properties of push–pull porphyrins as sensitizers for NiO based dye-sensitized solar cells

“…Expectedly, the uorescence of ZnP-CO 2 H-BV 2+ and ZnP-CO 2 H-eNDI is signicantly quenched, most probably by photoinduced electron transfer from ZnP to the adjacent electron acceptor (BV 2+ or NDI), as previously observed in similar systems. [39][40][41][42]…”

Ligand-Enhanced Electron Transfer from Zinc Tetraphenylporphyrin to Pyridine-Based Anthraquinone

“…The lifetime became shorter for zinc porphyrin with AEAQPy. Therefore, the fluorescence decay may arise from the direct quenching of the photoexcited singlet state of the porphyrin unit to the anthraquinone moiety 14,15 . From the lifetimes obtained from the fluorescence decay profiles, intramolecular electron transfer rate constants (κc) were calculated by the following equation 14 : κc = 1/ψ -1/ψ0, where ψ0 is the fluorescence lifetime of the ZnTPP.…”

“…Therefore, the fluorescence decay may arise from the direct quenching of the photoexcited singlet state of the porphyrin unit to the anthraquinone moiety 14,15 . From the lifetimes obtained from the fluorescence decay profiles, intramolecular electron transfer rate constants (κc) were calculated by the following equation 14 : κc = 1/ψ -1/ψ0, where ψ0 is the fluorescence lifetime of the ZnTPP. From a comparison of κc values between ZnTPP: AEAQPy (κc = 5.7 × 10 9 s -1 ) and ZnTPP: AEAQPh (κc ≈ 0), the κc value of pyridine compound is higher than that of phene compound.…”