Silver clusters anionic

Kaplan IG, Santamaria R, Novaro O (1995) Nonadditive interactions and the relative stability of neutral and anionic silver clusters. Int J Quantum Chem 55 237-243... 

An analogous mechanism is proposed for the activation of molecular oxygen and the cooperative binding of two oxygen molecules on the anionic silver clusters in which the first adsorbed O2 serves as an activator [351]. Since anionic silver clusters have generally lower VDE values than gold clusters, weaker electron acceptors such as O2 can already induce electron transfer and activate them, which is not possible in the case of Au . The first oxygen... 

Hence, experimental rate constant measurements in combination with theoretical simulations show a pronounced size and structure selective activity of anionic silver clusters toward molecular oxygen due to cooperative effects. In particular, for Ag clusters with odd n, a weakly bound first O2 promotes the adsorption of a second O2 molecule which is then (for n = 3, 5) differently bound with the O2 bond elongated to 1.32 A and thus potentially activated for further oxidation reactions such as CO combustion, which have indeed been observed for larger cluster sizes [361]. 

As evident from Table 1, the difference between the calculated and the experimental v alues of VDE and T for the most stable isomers of anionic silver clusters does not exceed 0.1 eV. In the case of neutral clusters, the best agreement between the theoretical and the experimental IPy values is also observed for the most stable isomers. 

Gold is one of the least reactive metals in bulk form. However, in recent years a considerable amount of theoretical and experimental works have studied the reactivity of small neutral and charged Au clusters towards different molecules, like H2, O2, CO, and organic radicals " . The reactivity depends on the size and charge state of the cluster. In the previous section we have studied the reactivity towards oxygen adsorption of anionic silver and gold clusters. In this section we study the reactivity of neutral gold clusters towards molecular O2 (subsection 6.1) and CO (subsection 6.2). 

The iron analog of (86) has been obtained by oxidative degradation of the anionic carbido cluster [Fe4(//4-C)(CO)12]2- with silver(I) ion (133). 

Mostafavi et al. [92] generate very small silver aggregates by a pulse radiolysis method and follow their aggregation and growth in the presence of an electron donor, the radical anion of sulfonatopropyl viologen (SPV) generated in the same pulse. They use this method to study the size dependence of the electrochemical potential of small silver clusters and conclude that a critical silver aggregate is Ag5+/Ag5, which has E° = —410 mV (NHE). 

Adsorption of two O2 molecules as observed in this experiment for Ag had been predicted before for the gold cluster anions [356] however, it was never observed experimentally which lead to further discussion in the literature [357,358]. In combination with a systematic theoretical study performed by the group of Bonacic-Koutecky [351] an understanding of the measured rate constant evolution with cluster size depicted in Fig. 1.58a emerges and reasons for the distinct behavior of silver cluster anions can be given [351]. 

On the basis of systematical comparative DFT investigations of silver clusters, a novel functional has been developed the use of which provides the results close to the experimental data. Structures of anions Ag7 , Ag9 and Agio have been reliably identified for the first time. 

Here, we report on the elaboration of original functional the use of which with moderate basis set provides sufficiently high accuracy of c alculations of different characteristics of silver clusters and on the reliable identification of structures of anions Agi, Agg and Agio. ... 

Fig. 5.2. Mass spectra of cationic silver clusters produced from mass-selected Ag anions using (a) a single laser pulse, (b) two laser pulses with At = 0, and (c) two subsequent laser pulses with At = 650 fs (A = 415nm). The structure in (b) is due to interference between the pump and probe pulses, and demonstrates that the timing assignment At = 0 is correct (taken from [418])...

The 3 + 1 condensation of 7 with 2 gives the iodide salt 8. Anion exchange on 8 (X=I) with hfflU Fs gives 8 as the hexafluorophosphate salt. The combination of 8 (X=PF ) with four equivalents of AgaO gives the tetranuclear biscarbene dimer 9 (P). Compound 9 is a dimer con sed of a silver cluster that is stabilized by two cyclophanes. The structural bonding of 9 is similar to 6... 

The preparation and reactions of metal cluster ions containing three or more different elements is an area with a paucity of results. The metal cyanides of Zn, Cd (258), Cu, and Ag (259) have been subjected to a LA-FT-ICR study and the Cu and Ag complex ions reacted with various reagents (2,256). The [M (CN) ]+ and [M (CN) +11 ions of copper, where n = 1-5, were calculated to be linear using the density functional method. The silver ions were assumed to have similar structures. The anions [M (CN) +1 of both copper and silver were unreactive to a variety of donor molecules but the cations M (CN) H + reacted with various donor molecules. In each case, where reactions took place, the maximum number of ligands added to the cation was three and this only occurred for the reactions of ammonia with [Cu2(CN)]+, [Cu3(CN)2]+, [Ag3(CN)2]+, and [ Ag4(CN)3]+. Most of the ions reacted sequentially with two molecules of the donor with the order of reactivity being Cu > Ag and NH3 > H2S > CO. 

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