Silver cation

For simplicity a cell consisting of two identical electrodes of silver immersed in silver nitrate solution will be considered first (Fig. 1.20a), i.e. Agi/AgNOj/Ag,. On open circuit each electrode will be at equilibrium, and the rate of transfer of silver ions from the metal lattice to the solution and from the solution to the metal lattice will be equal, i.e. the electrodes will be in a state of dynamic equilibrium. The rate of charge transfer, which may be regarded as either the rate of transfer of silver cations (positive charge) in one direction, or the transfer of electrons (negative charge) in the opposite direction, in an electrochemical reaction is the current I, so that for the equilibrium at electrode I... 

It is apparent (Fig. 1.21) that at potentials removed from the equilibrium potential see equation 1.30) the rate of charge transfer of (a) silver cations from the metal to the solution (anodic reaction), (b) silver aquo cations from the solution to the metal (cathodic reaction) and (c) electrons through the metallic circuit from anode to cathode, are equal, so that any one may be used to evaluate the rates of the others. The rate is most conveniently determined from the rate of transfer of electrons in the metallic circuit (the current 1) by means of an ammeter, and if / is maintained constant it can eilso be used to eveduate the extent. A more precise method of determining the quantity of charge transferred is the coulometer, in which the extent of a single well-defined reaction is determined accurately, e.g. by the quantity of metal electrodeposited, by the volume of gas evolved, etc. The reaction Ag (aq.) -t- e = Ag is utilised in the silver coulometer, and provides one of the most accurate methods of determining the extent of charge transfer. 

Metal cations in aqueous solution often form chemical bonds to anions or neutral molecules that have lone pairs of electrons. A silver cation, for example, can associate with two ammonia molecules to form a silver-ammonia complex ... 

Rinsing with water removes all the remaining silver cations from the film, leaving islands of black clumps of Ag atoms wherever photons were absorbed. 

The shape of the complex of benzene and silver cation is also explicable in a similar manner. The HO MO s of benzene are degenerate (ci ) and have the symmetry as follows ... 

Polynuclear complexes associated with transition metal polyhydrides and silver cations have been described those which present silver—metal bonds are more numerous and they will be... 

They have also examined the formation of the ir-complex between the silacalixarenes and silver cation by FAB mass spectrometry. Similar 77-complex formation with silver cation was observed for hexasila [2,2,2]paracyclophanes 37 (41). 

The Cu+ ion and the copper cluster cations were more reactive than the similar silver cations. Methanol was unreactive to Cu and Ag (n = 1-5). Ethanol was unreactive to CU5 and Ag+ (n = 3-5). The general reactions are shown as equations with examples given after the equation (see Eqs. 44-48). 

Fig. 2 (a) Schematic of the formation of silver clusters using DNA oligonucleotide as scaffold. After complexation of DNA with silver cations, the mixture is reduced with NaBtL, and the fluorescent cluster is formed, (b) Absorption spectra of silver clusters acquired every 30 min using [5 -AGGTCGCCGCCC-3 ] = 10 uM. [Ag+] = 60 uM. and [BfLj-] = 60 pM. The foremost spectrum was acquired 9 min after adding the BH4, and it has at 426 nm. The inset spectrum shows the last spectmm in the series (692 min), with peaks at 424 and 520 nm. (c) Induced circular dichroism spectra. The cell path length was 5 cm. The spectra were collected 2 min (A, dashed-dotted line), 20 min (B, dotted line), 40 min (C,fine dashed line), 60 min (D, coarse dotted line), and 150 min (E, solid line) after adding the BH [32]... 

The silver cation accepts a pair of electron from the ammonia, making the silver ion the Lewis acid. 

Interestingly Gokel has demonstrated the existence of a direct coordination coupling pathway between this ferrocene cryptand and a silver cation. Complexation studies were carried out with [24] and [25] (as well as other ferrocene cryptand-type species) by X-ray crystallography, FAB mass spectral analysis, nmr and UV/Vis spectroscopy. 

Compound [25] was thus shown to have an unusual affinity for Ag+ cations. X-ray crystallographic determination of the structures of the free ligand, sodium and silver complexes were carried out and are shown in Fig. 17. The Ag-Fe distance in the silver complex of [25] is only 3.37 A, whereas the Na-Fe distance in the sodium complex is 4.39 A. This evidence together with the FAB MS data and UV spectroscopic data suggests that there may be an interaction between the silver cation and the iron present in the ferrocene moiety. 

Fig. 17 The crystal structures of [25] H20 (left), [25] Na+ (right) and [25] Ag+ (facing page) illustrating the close proximity of the silver cation to the iron centre of... 

Fig. 6.1. Frenkel s scheme for the transport of silver ions in the AgBr crystal lattice. The silver cations are in interstitial portions in the crystal lattice and the same number of unoccupied lattice positions are in the cation part of the lattice.

The same way was used by Yoon and Kim (2005) for the preparation of 5-(p-methoxyphenyl)thian threnium ion incorporated in a calyx[4]arene. Namely, the ratio of starting materials, methoxycal-ixarene to the thianthrene cation-radical perchorate, was 1 10. The product of such 5-anisylation of thianthrene was further transformed into a calixarene bearing an additional o-phenylene thio-macrocycle. This macrocylization is beyond the scope of this book the original paper by Yoon and Kim (2005) could be recommended for those who interested in. It is worth noting only one practical importance of the calixarene-phenylene thiomacrocycle here It selectively extracts silver(l-l-) by both calixarene and thiomacrocycle. Each molecule of this combined complexon takes up two silver cations, so that extractability achieves 165%. 

As described above, cavitand 13 is able to extract efficiently silver(I) ion. For a guest to host ratio G/H>2 a new species was formed and recovered in quantitative yield and was identified as the 2 4 complex 132-(AgPic)4. The X-ray crystal structure of the 132-(AgPic)4 complex showed a supramolecular assembly made of two cavitands linked by their upper rim with four silver cations through P=S...Ag...S=P coordination (Fig. 9) [70]. 

Lithium and silver cationized loganin, ep/-loganin and ketologanin also fragment differently, as has been shown by Madhusudanan and coworkers . They also compared... 

Figure 1 Arrhenius plot of the rate constant of the hydrated electron with silver cation Ag. (From Ref. 50.)...

Fig. 6 compares the nuclearity effect on the redox potentials [19,31,63] of hydrated Ag+ clusters E°(Ag /Ag )aq together with the effect on ionization potentials IPg (Ag ) of bare silver clusters in the gas phase [67,68]. The asymptotic value of the redox potential is reached at the nuclearity around n = 500 (diameter == 2 nm), which thus represents, for the system, the transition between the mesoscopic and the macroscopic phase of the bulk metal. The density of values available so far is not sufficient to prove the existence of odd-even oscillations as for IPg. However, it is obvious from this figure that the variation of E° and IPg do exhibit opposite trends vs. n, for the solution (Table 5) and the gas phase, respectively. The difference between ionization potentials of bare and solvated clusters decreases with increasing n as which corresponds fairly well to the solvation free energy of the cation deduced from the Born solvation model [45] (for the single atom, the difference of 5 eV represents the solvation energy of the silver cation) [31]. 

Cyclopentane-1,3-diones 3 and 4 were prepared via a silver cation induced solvolysis of 2-bro-momethyl-2-hydroxycyclobutanones. This procedure represents a simple pathway to many 4-substituted and 4,5-disubstituled cyclopentane-1,3-diones.33 In particular, the reaction of 2-bromomethyl-2-hydroxy-3,3-dimethylcyclobutanone with silver nitrate gave 4,4-dimethylcy-clopentane-1,3-dione (3a) in 72% yield.33... 

In Ag[cis-Pt(NH3)2(l-methylthymine)2]2N03 5H20, the molecular cation (10) consisted of two units connected by a silver cation via the exocyclic 0-4 atoms. The Ag—O bond distances were in the range 235.3-256.3 pm.97... 

During irradiation of the emulsion (exposure) those silver halide grains which have absorbed some light have one or a few silver cations reduced to metallic silver. These form a latent image on the emulsion, so called because it cannot be seen by the human eye on account of the very low concentration of metallic silver atoms. At this stage the photochemical process itself is over, the next steps in the processing of the exposed emulsion being dark (thermal) chemical reactions. 

The oxidation proceeds via a highly symmetric transition state whereby the oxygen from the alcohol complexes with a silver cation, while another silver cation interacts with the hydrogen at the a-position of the alcohol (see below). 

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