Fullerene-porphyrin dyads

Kuciauskas D, Lin S, Seely G R, Moore A L, Moore T A, Gust D, Drovetskaya T, Reed C A and Boyd P D W 1996 Energy and photoinduced electron transfer in porphyrin-fullerene dyads J. Phys. Chem. 100 15 926-32... 

Imahori H, Tkachenko NV, Vehmanen V et al (2001) An extremely small reorganization energy of electron transfer in porphyrin—fullerene dyad. J Phys Chem A 105 1750-1756... 

Schuster DI, Li K, Guldi DM et al (2007) Azohenzene-linked porphyrin-fullerene dyads. J Am Chem Soc 129 15973-15982... 

Novel triads that contained tetrathiafulvalenes as electron donors and porphyrin chromophores (refer to previous section for porphyrin-fullerene dyads) as donor units have been recently reported [246] (Scheme 12). Improved analogs of the latter triads were soon considered by connecting the tetrathiafulvalene unit to a 7r-extended conjugated network [247]. 

As a leading example for short-spaced dyads, a n-n stacked porphyrin-fullerene dyad (ZnP-Ceo) 21 should be mentioned, which was probed in light of their electron transfer and back electron transfer dynamics [361, 362], The close van der Waals contact ( 3.0A) is responsible for pronounced electronic interactions in the ground state between the two 7t-chromophores. For example, the ZnP Soret-and Q-bands in the n-n stacked dyad 21 show a bathochromic shift and lower extinction coefficients compared to free ZnP [361], In the n-n stacked dyad 21 the linkage of the two bridging units occurs in the trans-2 position at the fullerene. A charge-separated radical pair evolves from a rapid intramolecular electron transfer k 35 ps) between the photoexcited metalloporphyrin and the fullerene core in a variety of solvents (i.e., ranging from toluene to benzonitrile). Remarkably, the lifetimes in tetrahydrofuran (t = 385 ps) and DCM (t = 122 ps) are markedly increased relative to the more polar solvents dichloromethane (r = 61 ps) and benzonitrile (t = 38 ps) [362]. This dependency prompts to an important conclusion ... 

The rates of the back electron transfer processes, from the ZnP +-C6o state to the ground state, are clearly in the Marcus-inverted region. This is one of the important examples that provide experimental support to electron transfer kinetics clearly occurring in the inverted region. Using the same synthetic methodology, a similar family of n-n stacked porphyrin fullerene dyads (i.e., ZnP-Ceo and H2P-C60), in which the porphyrin chromophore is attached by a malonate bridge to the trans- position of the fullerene sphere, has been reported [363]. 

We reported the first example of such a compound, porphyrin-fullerene dyad 23, in 1994 [134, 135]. Since that paper, a number of examples of dyads consisting of fullerenes linked to porphyrins or phthalocyanines have been prepared [136, 137-159]. Some of these, such as 24, use amide linkages related to those employed in some porphyrin-quinone systems [137, 149, 152]. In dyad 25, the moieties are linked by an extended, rigid bridge, of the type that has been shown to facilitate rapid long-range electron transfer in other systems [146, 147]. A number of dyads feature pyrrolidine-functionalized fullerenes, as in 26 and 27 [90, 139, 145, 148]. 

Figure 4. Transient states and interconversion pathways for porphyrin-futlerene dyads. The solid bars represent energies for free-base porphyrin-fullerene dyad 26, and the dashed bars represent energies for the zinc-porphyrin-fullerene dyad. Solid bars represent singlet or charge-separated states, and hollow bars stand for triplet states. The energies of the charge-separated states refer to polar solvents.

Imahori, Sakata and coworkers have bound porphyrin-fullerene dyad 27 to a... 

Both simple porphyrin-fullerene dyads and more complex systems may be very useful in artificial photosynthetic or molecular-scale electronie applications, due espeeially to the low reorganization energy of fullerenes and their low sensitivity to solvent parameters. 

Multiredox-Arrays Cobalt(II)Porphyrin-Fullerene Dyads... 

Imahori, H., T. Hasobe, H. Yamada, P.V. Kamat, S. Barazzouk, M. Fujitsuka, O. Ito, and S. Fukuzumi (2001). Spectroscopy and photocurrent generation in nanostruc-tured thin films of porphyrin-fullerene dyad clusters. Chem. Lett. 784-785. 

An interesting triad has been reported by Ito and D Souza, who have combined a covalent free base porphyrin-fullerene dyad bearing a pyridine substituent. 

Figure 13.88. Self-assembled porphyrin-fullerene dyad in LB films.

Tkachenko, N.V., V. Vehmanen, J.-P. Nikkanen, H. Yamada, H. Imahori, S. Fukuzumi, and H. Lemmetyinen (2002). Porphyrin-fullerene dyad with a long linker Formation of charge transfer conformer in Langmuir-Blodgett film. Chem. Phys. Lett. 366(3-4), 245-252. 

A first report was pnblished in 2011 by Song et al. claiming the synthesis and characterization of porphyrin-fullerene dyads and the application of such compounds in the photoinduced H2 evolution [268]. As an example, the reaction pathway to one the dyads nsed in the experiments is shown in Scheme 14.13. 

Song L-C, Liu X-F, Xie Z-J, Luo F-X, Song H-B. Synthesis and structural characterization of some new porphyrin-fullerene dyads and their appUcation in photoinduced H2 evolution. Inorg Chem 2011 50 11162-72. 

Ostrowski (Siedlce, Poland) applied 6 in preparation of some porphyrin budding blocks, including a porphyrin-fullerene dyad, being a new artificial photos)mthetic model (Figure 12). ... 

D Souza, R, Rath, N. R, Deviprasad, G. R. and Zandler, M. E. Structural studies of a non-covalently linked porphyrin-fullerene dyad. Chem. Commun. 3, 267-268, 2001. 

Hydrogen bonding is also important to construct supramolecular architectures of porphyrins, which is well summarized in the review by Satake and Kobuke [14]. For example, self-assembly of a porphyrin-fullerene dyad through Watson-Click hydrogen bonding offers a good model of photoin-duced electron transfer in supramolecular assembly (Fig. 9) [25]. Shirakawa... 

Gervaldo M, Liddell PA, Kodis G, Brennan BJ, Johnson CR, Bridgewater JW, Moore AL, Moore TA, Gust D (2010) A photo- and electrochemically-active porphyrin-fullerene dyad electropolymer. Photochem Photobiol Sci 9 890-900... 

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