Photoinduced intramolecular electron

Williams R M, Zwier J M and Verhoeven J W 1995 Photoinduced intramolecular electron transfer in a bridged Cgg (acceptor)-aniline (donor) system. Photophysical properties of the first active fullerene diad J. Am. Chem. See. 117 4093-9... 

Yonemura, H., Noda, M., Hayashi, K, Tokudome, H., Moribe, S. andYamada, S. (2002) Photoinduced intramolecular electron transfer reactions in fiillerene-phenothiazine linked compounds effects of magnetic field and spacer chain length. Mol. Phys., 100, 1395-1403. 

E. Galoppini, M. A. Fox, Effect of the Electric Field Generated by the Helix Dipole on Photoinduced Intramolecular Electron Transfer in Dichromophoric Alpha-Hdical Peptides , J. Am. Chem. Soc 1996, 118, 2299-2300. 

Similar experimental studies were carried out on molecules in which the bridge is constituted by conjugated groups [83, 84]. General references on photoinduced intramolecular electron transfers may also be found in two recent reviews [85, 86]. 

Photoinduced intramolecular electron transfer in the donor-acceptor complex 87 (R = H) generates transient charge-separated open-shell species with the remarkably long lifetime of about 75 ps [89]. Dyads that contain Tt-extended tetrathiafulvalene units also form stable cationic species upon oxidation [90]. The dumbbell shaped triad 91 [91-93] (Scheme 4.13) was obtained by carrying out the reaction with the in situ generated bis-diene at room temperature, in the dark and in o-dichlorobenzene as a solvent in 50% yield. The product is thermally unstable and easily undergoes a retro-Diels-Alder reaction [91]. 

Studies of fluorescence quenching in 8-bond pairs in solvents such as diethylether and acetonitrile, allowed a rate of the photoinduced intramolecular electron transfer of the order of 109s 1 to be estimated, showing that very rapid intramolecular transfer can also occur in the excited bifunctional molecule. 

Photoinduced Intramolecular Electron Transfer Within Porphyrinic Rotaxanes... 

Photoinduced intramolecular electron tunneling was observed also in some other porphyrin containing bridge molecules, such as porphyrin covalently linked to phenolphthalein [308], dimethylaniline — mesoporphyrin II — quinone triad [309], Zn porphyrin-viologen-quinone triad [310], carotenoid — porphyrin -diquinone tetrad [311]. The influence of conformational state of porphyrin-viologen bridge molecules on the rate of PET reactions was studied in Ref. [312]. 

VI. PHOTOINDUCED INTRAMOLECULAR ELECTRON TRANSFER IN METAL-ORGANIC DYADS ... 

Wasielewski, M.R., Niemczyk, M.P. and Svec, W.A., 1982. Selectively metalated doubly cofacial porphyrin trimers. New models for the study of photoinduced intramolecular electron transfer, Tetrahedron Lett.. 3215-3218. 

A much more deep-seated photorearrangement than in the dibenzo[2.2.2] systems occurs in the dibenzo[3.2.1] compound 55 with chloride or bromine as nucleofugal group at C-8 (equation 49)229. 9-Functionalized phenanthrenes are formed, supposedly also by way of photoinduced intramolecular electron transfer in the (triplet) excited state. 

Takashima H,Tara C, Namikawa S, Kato T, Araki Y, Ito O, Tsukahara K. Photoinduced intramolecular electron-transfer reactions of reconstituted met- and zinc-myoglobins appending acridine and methylacridinium ion as DNA-binders. J Phys Chem B 2006 110 26413-23. 

M. Fujihira, M. Sakomura, Photoinduced Intramolecular Electron-Transfer Across Monolayers Consisting of Linear A-S-D Triad Amphiphilic Molecules , Thin Solid Films, 179,471 (1989)... 

Finally, it is important to note (Section 5.3.6) that electrochemistry and UV-Vis absorption spectra of molecular dyads or triads based on metal polypyridines show that electronic interactions between the components of the systems discussed above are too small to influence ground-state behavior. Nevertheless, they are sufficient to allow for very fast intramolecular electron transfer when electronically excited. In fact electronic coupling of 0.002-0.005 eV would be quite enough, but hardly detectable electrochemically. Detailed studies of electrochemistry and spectroscopy of these supramolecular systems and their components are, nevertheless, essential for the understanding of the energetics of photoinduced intramolecular electron and energy transfer reactions. 

The first investigation on photoinduced intramolecular electron transfer between units covalently attached to a dendritic framework was performed on a series of... 

Photoinduced intramolecular electron transfer reactions in triad assemblies have been extensively examined with regard to mimicking the photosynthetic center. Novel bridging ligands L25a and L25b were prepared, in which the naphthalene bis(dicarboximide) unit is linked by two bidentate (2-pyridyl)benzimidazole (Ll).55 Under photoirradiation, photoinduced electron transfer from the Ru(bpy)2 moiety to the diimide site takes place. 

Irradiation of a system consisting of 2-methyl-1,4-dihydroxynaphthalene and benzophenone leads to formation of benzophenone ketyl radical and 2-methyl-naphthosemiquinone, and 1 a,7a-dihydro-1 a-methyl-1,1 -diphenyl-1 H-cyclopropa-[b]naphthalene-2,7-dione derivatives (4) in the presence of Mg(C104)2 give indenonaphthoquinones (5) (Scheme 1), by photoinduced intramolecular electron transfer in almost quantitative yield. In agreement with Rehm-Weller predictions, the rate constants for electron transfer between the triplet states of various substituted naphthoquinones and N,N-dimethylaniline (DMA) in acetonitrile solution were found to be diffusion controlled. " Using this information, it has been shown that the efficiencies of formation of naphthalene " and DMA are unity. 

Irradiation of 1,4,8,11,15,18,22,25-octabutoxyphthalocyanine or its copper derivatives in degassed ethanol containing triethanolamine causes its reduction by a mechanism which involves a higher excited state of the substrate,and a plot of the log of the rate constants for the photoinduced intramolecular electron transfer in a supramolecular assembly of Zn and Au porphyrins bridged by diphenylphenanthroline has been found to decrease linearly with diminishing energy difference between the HOMO and LUMO of the participating orbitals. ... 

Photoinduced intramolecular electron transfer in porphyrin triads of 4he type [zinc octaethylporphyrin-4,4 -bipyridinium-tetraphenylporphyrin] occurs either from the singlet state of the zinc porphyrin ( A) or from the corresponding free base ( B) with formation of or An... 

More recently, pulse radiolysis started to play a major role in the characterization of photolytically generated (A —D ) radical pairs in a variety of fullerene containing donor-bridge-acceptor dyads (68,69). While the latter evolve from photoinduced intramolecular electron transfer reactions complementary employment of pulse radiolysis allowed to generate the reduced and oxidized entities in separate experiments and to superimpose the features of the two reactive moieties. In this context, it should be noted that conventional methods, such as cyclic voltammetry, due to their unfavorable time resolution, fail to contribute to the radical pair characterization. 

The photoinduced intramolecular electron transfer reactions of some poly-(ethylene glycol)-linked 9-aminoacridine-benzoate electron donor-acceptor systems have been described. Photosensitized oxidation of 5-methyl-2 -deoxy-cytidine using menadione (2-methylnaphthalene-l,4-dione) gives 5,6-dihydroxy-5,6-dihydro-5-methyl-2 -deoxycytidine in what is thought to be an electron... 

From Electron Acceptor Molecules to Photoinduced Intramolecular Electron-Transfer Systems N. Martin and C. Seoane... 

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