Optical electron transfer

The main spectroscopic consequence of the combined action of electron transfer and vibronic interaction is the occurrence of the so-called electron transfer optical absorption (intervalence band), which is shown by the arrows in Fig. 10. The shape and intensity of the intervalence band in the PKS model is defined by the ratio t /(v /cu). In the case of weak transfer the Franck-Condon transitions are almost forbidden, and at the same time, the Stokes shift can be significant. Therefore the MV dimers of Class I are expected to exhibit weak and wide intervalence bands. On the contrary, in the Class III compounds the Franck-Condon transition is allowed, and the Stokes shift is zero. For this reason, intervalence optical bands in delocalized MV dimers are strong and narrow. When the extra electron jumps over the spin cores in a multielecton MV dimer d" — > 1) [85-87] we are dealing with... 

Electromagnetic electron transfer Optical brighteners Photo initiators, synergists UV absorbers Benzoxazoles. Benzophenone, Thioxanthones Hydroxybenzophenones, tetramethyl piperidine. Benztriazoles. Triazines. 

SAMs are generating attention for numerous potential uses ranging from chromatography [SO] to substrates for liquid crystal alignment [SI]. Most attention has been focused on future application as nonlinear optical devices [49] however, their use to control electron transfer at electrochemical surfaces has already been realized [S2], In addition, they provide ideal model surfaces for studies of protein adsorption [S3]. 

Electronic and optical excitations usually occur between the upper valence bands and lowest conduction band. In optical excitations, electrons are transferred from the valence band to the conduction band. This process leaves an empty state in the valence band. These empty states are called holes. Conservation of wavevectors must be obeyed in these transitions + k = k where is the wavevector of the photon, k is the... 

Chemical reactions can be studied at the single-molecule level by measuring the fluorescence lifetime of an excited state that can undergo reaction in competition with fluorescence. Reactions involving electron transfer (section C3.2) are among the most accessible via such teclmiques, and are particularly attractive candidates for study as a means of testing relationships between charge-transfer optical spectra and electron-transfer rates. If the physical parameters that detennine the reaction probability, such as overlap between the donor and acceptor orbitals. 

Elliott C M, Derr D L, Matyushov D V and Newton M D 1998 Direct experimental comparison of the theories of thermal and optical electron-transfer studies of a mixed-valence dinuclear iron polypyridyl complex J. Am. Chem. 

Reorganisation energies of optical electron transfer processes. R. D. Cannon, Adv. Inorg. Chem. Radiochem., 1978, 21 179-230 (155). 

Controlled-potential (potentiostatic) techniques deal with the study of charge-transfer processes at the electrode-solution interface, and are based on dynamic (no zero current) situations. Here, the electrode potential is being used to derive an electron-transfer reaction and the resultant current is measured. The role of the potential is analogous to that of the wavelength in optical measurements. Such a controllable parameter can be viewed as electron pressure, which forces the chemical species to gain or lose an electron (reduction or oxidation, respectively). 

The benzannulation reaction of ethynylferrocene 120 with the diterpenoid chromium alkoxycarbene 119 leads to novel diterpenoid ferrocenyl quinones 121 which, due to their electron-transfer properties, are regarded as potential candidates for non-linear optical materials [71] (Scheme 52). 

Reorganization Energies of Optical Electron Transfer Processes R. D. Cannon... 

Blasse G (1991) Optical Electron Transfer Between Metal Ions and its Consequences. 76 153-188... 

Cluster Fx was also identified via its EPR spectral features in the RCI photosystem from green sulfur bacteria 31, 32) and the cluster binding motif was subsequently found in the gene sequence 34 ) of the (single) subunit of the homodimeric reaction center core (for a review, see 54, 55)). Whereas the same sequence motif is present in the RCI from heliobacteria (50), no EPR evidence for the presence of an iron-sulfur cluster related to Fx has been obtained. There are, however, indications from time-resolved optical spectroscopy for the involvement of an Fx-type center in electron transfer through the heliobacterial RC 56). 

Lantz, J. M. and Corn, R. M. (1994) Electrostatic field measurements and hand fiattening during electron-transfer processes at single-crystal Ti02 electrodes by electric field-induced optical second harmonic generation. J. Phys. Chem., 98, 4899-4905. 

It has been reported that Cgo and its derivatives form optically transparent microscopic clusters in mixed solvents [25, 26]. Photoinduced electron-transfer and photoelectrochemical reactions using the C o clusters have been extensively reported because of the interesting properties of C o clusters [25,26]. The M F Es on the decay of the radical pair between a Cgo cluster anion and a pyrene cation have been observed in a micellar system [63]. However, the MFEs on the photoinduced electron-transfer reactions using the Cgo cluster in mixed solvents have not yet been studied. 

Optical Electron Transfer Between Metal Ions... 

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