Light-induced electron transfer

The excited-state redox reaction, equation (8.12), is thermodynamically favorable (E° > 0) while ground-state reaction, equation (8.13) is not (E° < 0). Therefore, a mixture of [Cr(phen)3]3+ and such a substrate will only undergo a redox reaction after the chromium complex has been excited. This is the process of photo-induced electron transfer light initiates an electron-transfer reaction. This experiment will explore how substrates such as DNA may be oxidized by the excited-state [Cr(phen)3]3+ complex. Because the electron-transfer reaction competes kinetically with luminescence, the presence of such a suitable substrate leads to a decrease in the intensity of luminescence. For this reason, the substrate is termed a quencher. 

As a result of the very efficient primary charge separation within the CdS/Ti02 sandwich, certain electron transfer reactions induced by light excitation within CdS, are expected to occur at a much higher yield when combined within a CdS/Ti02 sand-... 

Photoinduced electron and energy transfer are fundamental processes m nature In photosynthetic organisms, photoinduced electron transfer that induces conversion of light into chemical energy begins when photonic excitation reaches the so-called reaction center (RC) Usually. 

WA -Disuccinitnidyl carbonate reacted with the ribose derivative 77 to give the mixed active carbonate 78, which was used to alkoxycarbonylate amines. The resulting carbamates, e.g., compound 79 from ephedrine, are of interest in medicinal chemistry. The xanthate 80 underwent an unusual radical rearrangement, as outlined in Scheme 8, as the result of an electron transfer process induced by (p-BrCjH4)3NSbCl6 in the presence of light. The end product was the 3,6-anhydrofuranose derivative 81. ° ... 

Calculations within tire framework of a reaction coordinate degrees of freedom coupled to a batli of oscillators (solvent) suggest tliat coherent oscillations in the electronic-state populations of an electron-transfer reaction in a polar solvent can be induced by subjecting tire system to a sequence of monocliromatic laser pulses on tire picosecond time scale. The ability to tailor electron transfer by such light fields is an ongoing area of interest [511 (figure C3.2.14). 

Evans D G, Coalson R D, Kim H J and Dakhnovskii Y 1995 Inducing coherent oscillations in an electron transfer dynamics of a strongly dissipative system with pulsed monochromatic light Phys. Rev. Lett. 75 3649... 

Various light-induced reactions including hydrogen atom abstraction, electron transfer and (3-scission occur under the influence of UV light. Certain... 

Willner, I and Willner, B. Artifical Photosynthetic Model Systems Using Light-Induced Electron Transfer Reactions in Catalytic and Biocatalytic Assemblies. 159, 153-218... 

The single-electron transfer from one excited component to the other component acceptor, as the critical step prior to cycloaddition of photo-induced Diels Alder reactions, has been demonstrated [43] for the reaction of anthracene with maleic anhydride and various maleimides carried out in chloroform under irradiation by a medium-pressure mercury lamp (500 W). The (singlet) excited anthracene ( AN ), generated by the actinic light, is quenched by dienophile... 

Another class of photochemically relevant polyphosphazenes is formed by macromolecules having chromophores able to absorb light in a selective way and to transfer it to external species, thus inducing different reactions by energy transfer processes. In some cases electron transfer processes are also involved. These situations are described by Formula below and the corresponding polymers and external reagents are reported in Table 26. 

It is interesting to compare the thermal-treatment effect on the secondary structure of two proteins, namely, bacteriorhodopsin (BR) and photosynthetic reaction centers from Rhodopseudomonas viridis (RC). The investigation was done for three types of samples for each object-solution, LB film, and self-assembled film. Both proteins are membrane ones and are objects of numerous studies, for they play a key role in photosynthesis, providing a light-induced charge transfer through membranes—electrons in the case of RC and protons in the case of BR. 

Ennaoui A, Tributsch H (1986) Light-induced electron transfer and photoelectrocatalysis of... 

The cationie dye was assoeiated with the anion (7,8,9,10,11,12 Brg-l-CBnHg) in order to dissolve it in the organie phase. The polarizable window available for photoinduced electron transfer in this system extended over 100 mV for the eonditions specified in Fig. 13. The photoeurrent responses were measured under ehopped light and lock-in detection at 8.4 Hz. Figure 13(b) shows that some photoresponses oeeur only in the presence of the dye speeies, whieh the authors attributed to the transfer of Ru(bpy)3" to the aqueous phase as a result of interfaeial polarization induced by the ehopped light [130]. Upon addition of in the aqueous phase, an inerease in the amplitude of the photo-... 

Photocatalytic oxidation is a novel approach for the selective synthesis of aldehyde and acid from alcohol because the synthesis reaction can take place at mild conditions. These reactions are characterized by the transfer of light-induced charge carriers (i.e., photogenerated electron and hole pairs) to the electron donors and acceptors adsorbed on the semiconductor catalyst surface (1-4). Infrared (IR) spectroscopy is a useful technique for determining the dynamic behavior of adsorbed species and photogenerated electrons (5-7). 

Scheme 6 a Incorporation of a silyl-spaced dimer into DNA, and treatment of the DNA strand with fluoride furnished DNA strand containing a dimer-unit with an open backbone. b Schematic representation of the light (ho) induced excess electron transfer (ET) from the reduced flavin to the dimer, followed by cycloreversion (CR). c The five DNA duplexes 13-17 containing the flavin donor and the dimer acceptor at increasing distances, together with the measured repair yields after irradiation for 1 min... 

Kaim, W. Thermal and Light Induced Electron Transfer Reactions of Main Group Metal Hydrides and Organometallics. 169, 231-252 (1994). 

Fugimori, E. and M. Talva. 1966. Light-induced electron transfer between chlorophyll and hydroquinone and the effect of oxygen and beta-carotene. Photochem. Photobiol. 5 877-887. 

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