Silver centers

Fig. 12. A possible mechanism for the dye-induced photooxidation of a silver center, x represents the distance across a silver haUde surface to which aggregated dye molecules are adsorbed. Steps 1, 4, and 5 represent the photohole (Q) formation, photohole migration, and silver oxidation processes which can ultimately lead to the total regression of the silver aggregate ( ) represents an energy state occupied by an electron.

If n — 1 photons are absorbed as in equation 8, then the complete annihilation of the -atom silver center can occur as shown in equations 12 and 13 ... 

This difference is a measure of the free-energy driving force for the development reaction. If the development mechanism is treated as an electrode reaction such that the developing silver center functions as an electrode, then the electron-transfer step is first order in the concentration of D and first order in the surface area of the developing silver center (280) (Fig. 13). Phenomenologically, the rate of formation of metallic silver is given in equation 17,... 

The dinuclear 2 3 species have been characterized in [Ag20u-dppm)3](OTf)2 and [Ag2(p-dppm)3](N03)2 (92), with the silver centers three coordinate by three phosphorus atoms of different dppm ligands.761,768 A tetranuclear species [Ag2(p-02CMe-0,0 )(p-02CMe-0)(p-dppm)]2 has been obtained by reaction of dppm with two equivalents of AgOAc. 762 The reaction of [Ag(Mes)]4 with dppm gives a trinuclear compound [Ag3(dppm-H)3] (93) in which the dppm ligand has been deprotonated with the formation of mesithylene. In the structure, two of the silver centers are three coordinate to three different phosphorus atoms and the other silver atoms is bonded to two carbon atoms.291,292... 

The crystal structure for 179b was determined which showed a planar geometry for the silver center and the carbaporphyrin ligand. A small tilt angle of 5.09° for the indene unit relative to the mean macrocyclic plane was determined, and the Ag-C bond length was 2.015(4) A. Extension of the work to the benzocarba-, benzi-, oxybenzi-,... 

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