Charge promoted processes

Some salts, particularly of transition metals, are highly colored and absorb in the UV and visible regions. Salts and complexes that have the highest molar absorptivities tend to absorb electromagnetic radiation by a charge-transfer process. In the charge-transfer process, an electron is promoted from one part of a complex to another causing one part of the complex to be oxidized and the other to be reduced as in Eq. (5.11). 

An iron-promoted cobalt molybdate catalyst (Fe0 03Co0.9 7MoO4) was studied by Maksimov et al. [195,196] with respect to the role of iron in the transfer of charge. Iron strongly enhances the catalytic activity and at the same time increases the conductivity by a factor of 100. Mossbauer spectroscopy reveals that 4% of the iron ions are present as Fe2+ impurity . This fraction is doubled at steady state reaction conditions, and indicates participation of iron in the charge transfer process. 

In less acidic (or more basic) solutions, hydroxide or oxide bridges between metal atoms form, the high positive charge promotes more hydrogen ion dissociation, and a large aggregate of hydrated metal hydroxide precipitates. A possible first step in this process is... 

A photoredox reaction is a redox reaction that occurs after electronic excitation of one or several reaction partners. A representative example is given by the charge transfer process that occurs as a consequence of light absorption by a metal-ligand complex. The light absorption promotes an electron from an occupied orbital of the ligand to an unoccupied orbital of the metal ion. Photo-... 

Density functional theory calculations of the localization of the involved molecular wavefunctions predicted a bridging state across the interface of P3HT and fullerene molecules that promotes an adiabatic charge transfer process [89]. In addition, this bridging state was found to have a considerable overlap with LUMO states in the fullerene, thus increasing the separation probability of the charge transfer state. 

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Insoluble 3-methylPT with incorporated copper(II)salt arising from CuCl2 used during chemical polymerization as co-promoter pressed as pellets has been used as both anode and cathode of a very stable battery cell with 0.1M aqueous sodium perchlorate solution with perchloric acid as supporting electrolyte at pH 1.5. The charge-discharge process has an efficiency of 0.31, but it is unknown if the charge capacity is within the copper redox system or within the PT redox system [99]. 

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