PREPARATION AND PHOTOPHYSICAL STUDIES OF PORPHYRIN‐C₆₀ DYADS

Abstract

Porphyrin‐C60 dyads in which the two chromophores are linked by a bicyclic bridge have been synthesized using the Diels‐Alder reaction. The porphyin singlet lifetimes of both the zinc (Pzn‐C60) and free base (P‐C60) dyads, determined by time‐resolved fluorescence measurements, are ≦17 ps in toluene. This substantial quenching is due to singlet‐singlet energy transfer to C60 The lifetime of Pzn‐1C60 is ‐5 ps in toluene, whereas the singlet lifetime of an appropriate C60 model compound is 1.2 ns. This quenching is attributed to electron transfer to yield Pznbull;+‐C60bull;‐. In toluene, P‐1C60 is unquenched; the lack of electron transfer is due to unfavorable thermodynamics. In this solvent, a transient state with an absorption maximum at 700 ran and a lifetime of‐10 μs was detected using transient absorption methods. This state was quenched by oxygen, and is assigned to the C60 triplet. In the more polar benzonitrile, P‐1C60 underoes photoinduced electron transfer to give P•+‐C60bull;‐. The electron transfer rate constant is −2 × 1011 s−1.

Synthesis and electronic properties of donor-linked fullerenes

“…Fullerene-substituted porphyrins desired tetraphenylporphyrin 2 was subsequently isolated in 12% yield by tedious chromatographic separations. All Since the first reported preparation of a C -linked of the spectroscopic studies and elemental analysis results 60 porphyrin by Gust et al [23], several other fullerenewere consistent with the proposed molecular structures. 1 porphyrin hybrids have been described and inThe H-NMR spectra of 1 depicted at room temperature tramolecular processes such as electron and energy transfer the presence of two conformers in a 1:1 ratio.…”

Metal-chelating capacities attached to fullerenes

“…In 1994, the first example of [60]fullerene anchored to zinc porphyrin was presented by Gust and coworkers [11]. Nowadays, it is established that the combination of a porphyrin unit and C 60 leads to a photoactive compound, capable of electron or energy transfer upon photoexcitation.…”

“…2) [11]. The influence of the C 60 moiety upon the photophysical behavior of the porphyrin unit was studied in more detail.…”

Creation of Fullerene-Based Artificial Photosynthetic Systems

“…Although occurrence of ultrafast photoinduced ET and metastability of the resulting charge-separated state at low temperature have been reported for the composite films, [37][38][39][40] the underlying ET properties of 44 and based on fluorescence lifetime measurements and energy level diagram, they have indicated that ET from the porphyrin excited singlet state to the C 60 and/or from the porphyrin to the C 60 excited singlet state is involved. 44 Verhoeven et al have reported the synthesis and photophysical properties of aniline-C 60 -linked dyad. 45 The fluorescence decay data show the occurrence of photoinduced ET from the aniline to the C 60 .…”