Energy transfer redox potential

The potential of the Bk(III)—Bk(0) couple has been investigated, using radiopolarography (229,230) and theoretical calculations (231), as well as by correlation with enthalpy of formation data (132, 133). Estimates of the potentials of berkelium redox couples have also been made from correlation plots of electron-transfer and f-d absorption band energies versus redox potential and by theoretical calculations (215, 221, 232, 233). 

V and [Tb4+/Tb3+] = 3.1 V. The important point involved in this method is the linear relationship between charge transfer band energies and redox potentials. Some data obtained in this way are given in Table 2.9. 

Establishment of the mechanism and practical applications of excited state energy- and electron transfer processes require precise information on the energies and redox potentials for oxidation and reduction processes in the ground and excited state. Onset of the luminescence is a direct way of determining the excited state energies. Due to possible solvent-induced excited state relaxation effects that can occur at ambient temperature. 

ZnO (suspension) sensitizes the photoreduction of Ag" by xanthene dyes such as uranin and rhodamine B. In this reaction, ZnO plays the role of a medium to facilitate the efficient electron transfer from excited dye molecules to Ag" adsortei on the surface. The electron is transferred into the conduction band of ZnO and from there it reacts with Ag. In homogeneous solution, the transfer of an electron from the excited dye has little driving force as the potential of the Ag /Ag system is —1.8 V (Sect. 2.3). It seems that sufficient binding energy of the silver atom formed is available in the reduction of adsorbed Ag" ions, i.e. the redox potential of the silver couple is more positive under these circumstances. 

Requirements for redox potential matching and high transfer energy have limited the choice for the aqueous redox species to [Fe(CN)6] [43,56,62,63,70,71,74,76,81,82,86],... 

Studies of ferredoxin [152] and a photosynthetic reaction center [151] have analyzed further the protein s dielectric response to electron transfer, and the protein s role in reducing the reorganization free energy so as to accelerate electron transfer [152], Different force fields were compared, including a polarizable and a non-polarizable force field [151]. One very recent study considered the effect of point mutations on the redox potential of the protein azurin [56]. Structural relaxation along the simulated reaction pathway was analyzed in detail. Similar to the Cyt c study above, several slow relaxation channels were found, which limited the ability to obtain very precise free energy estimates. Only semiquantitative values were... 

The excited state redox potential of a sensitizer plays an important process. An approximate value of the excited state redox potential potentials of the ground state couples and the zero-zero excitation Equations (13) and (14). The zero-zero energy can be obtained from of the sensitizer 38 role in the electron transfer can be extracted from the energy (E0 0) according to the 77 K emission spectrum... 

There are other cases in which triplet-mediated energy transfer might compete with LMCT-mediated energy transfer, particularly where the metal ion is either europium or samarium. In these cases, the redox potentials of the metal ions are such that LMCT is feasible, although the LMCT state will be lower in energy than the emissive state of the metal, precluding luminescence.65... 

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