Inter-metal electron transfer

Figure 13 Scheme of the influence of the dose rate on the competition between the inter-metal electron transfer and the coalescence processes during the radiolytic reduction of mixed metal ion solutions. Sudden irradiation at high dose rates favor alloying, whereas low dose rates favor coreshell segregation of the metals because of metal displacement in the clusters. 

Due to a kinetic competition between inter-metallic electron transfer and radiation-induced reduction of mixed metal ions, it was shown, thanks to radiolysis, that the core-shell or alloyed structure of a bimetallic nanoparticle depends not only on the redox potentials of the mixed systems but also on the metal ions reduction rate which is controlled by the dose rate. 

While 7-radiolysis at relatively low dose rates enabled the synthesis of a few alloyed clusters such as Ag-Pd nanoparticles (also chemically synthesized), radiolysis at very high dose rates (by electron beams) led to the synthesis, at room temperature, of a lot of new alloys such as Au-Pd bimetallic nanoparticles/ Like in the case of Ag-Au system, at low dose rate (7-irradiation), bilayered Au -Pd.i,ii nanoparticles were obtained. However, at high dose rates (electron beams), the reduction is faster than the possible inter-metal electron transfer, then alloyed clusters were prepared. Moreover, since the radio-induced reduction of metal ions is faster at high dose rates, the synthesized particles are, in these conditions, always smaller with a narrow distribution in size. 

An electronic excited state of a metal complex is both a stronger reductant and oxidant than the ground state. Therefore, complexes with relatively long-lived excited states can participate in inter-molecular electron transfer reactions that are uphill for the corresponding ground state species. Such excited state electron transfer reactions often play key roles in multistep schemes for the conversion of light to chemical energy ( 1). 

As a result of the same intra-chain rr-bonding and the relatively strong inter-chain electron transfer interaction, the mechanical properties (Young s modulus and tensile strength) of conjugated polymer are potentially superior to those of saturated polymers. Thus, metallic polymers offer the promise of truly high performance high conductivity plus superior mechanical properties. 

B. Shanghavi P. V. Kamat, Inter-partide electron transfer in metal/... 

This behaviour is explained in terms of a dynamic process in which inter-molecular electron transfer between (UO2 ) and metal complexes occurs. Other pertinent results are i) The quenching is highly efficient (approaching the diffusion controlled rate) with metallocenes or metal carbonyls which do not possess optically detectable electronic excited states... 

The Cd-Na phase diagram, established with 5-85 wt% Na, shows two inter-metallic phases, NaCdj and Na2Cd,. The latter was earlier reported as either NaCds or NaCdg, but more recent work indicates a cubic structure isomorphous with MgjZn,] in which some electron transfer occurs between the two types of atom . ... 

Contents Formal Oxidation Numbers. Configurations in Atomic Spectroscopy. Characteristics of Transition Group Ions. Internal Transitions in Partly Filled Shells. Inter-Shell Transitions. Electron Transfer Spectra and Collectively Oxidized Ligands. Oxidation States in Metals and Black Semi-Conductors. Closed-Shell Systems, Hydrides and Back-Bonding. Homopolar Bonds and Catenation. Quanticule Oxidation States. Taxological Quantum Chemistry. 

A second way to overcome this spin conservation obstacle is via reaction of 302 with a paramagnetic (transition) metal ion, affording a superoxometal complex (Fig. 4.1, Reaction (3)). Subsequent inter- or intramolecular electron-transfer processes can lead to the formation of a variety of metal-oxygen species (Fig. 4.2) which may play a role in the oxidation of organic substrates. 

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