Silver complexes clusters

The final silver cluster diameter increases, at given initial Ag and PVA concentrations, for example from 15 to 50 nm (n 50 times larger), when the part of reduction is increasingly achieved by the donor SPV, rather than by radiolytic radicals [31]. A red shift correlates with the growth in size in the final optical surface plasmon band. Nonirradiated solutions of EDTA silver complex are stable because EDTA does not reduce the ions directly. However, after the appearance of the 400-nm spectrum of silver... 

The preparative route was also soon adapted for the synthesis of copper-and silver-containing clusters by using the complexes [MI(PEt3)J (M = Cu or Ag) instead of [AuC1(PR3)J [Eq. (3)] (25). The versatility of the... 

In terms of its coordination chemistry, the silver(I) ion is typically characterized as soft . Although originally believed to only bind ligands in a linear arrangement, it was soon shown that it can adopt a variety of coordination environments, the most common one being a four-coordinate tetrahedral geometry. Square-planar complexes are not rare, and various silver(I) cluster complexes also contain three-and five-coordinate sUver(I) ions. 

Unlike the copper telluride clusters, it has not yet proven possible to generate large silver telluride cluster complexes using a combination of R3P, Ag-X and Te(SiMe3)2. This suggests that the phosphine ligands are unable to kinetically... 

Bimetallic gold-silver complexes may be prepared from gold bis(ylide) species such as [Au(CH2PPh3)2]ClC>4 and AgC104 (leading to neutral clusters, equation 54) or... 

For silver complexed by CN , the surface plasmon spectrum of clusters develops with a maximum close to 395 nm, similar to that of hydrated clusters without ligand, but with a higher extinction coefficient per atom 395 (Ag cn") =... 

The anionic nature of 5 results in excellent solubility in ether solvents compared with that of the neutral, silver complex 3. Although we have isolated several silver tellurium eomplexes 3 with different phosphine ligands (PEt3, PEtaPh, PPr"3), the same cannot be said for 5 for which, to date, only the PEt3 derivative has been isolated and characterized via the condensation reaction outlined in Scheme 4. One distinct advantage this route does offer is, however, the possibility of synthesizing ternary and quaternary phase nanoclusters by promoting condensation of different cluster molecules. 

To date the largest silver-tellurium cluster isolated and structurally characterized, albeit in moderate yields, is the complex [Ag48(ya3-TeBu")24Tei2(PEt3)i4] 6. Cluster 6 is obtained as the only crystalline product from the reaction of AgCl/PEt3/Te(Bu")SiMe3 (1 2 1) it is isolated as dark red crystals after several days (Scheme 2, Fig. 9). ... 

This section includes selected examples of electrochemistry of gold and silver complexes with other ligands and structural types that were not included in previous sections. We have also included a list of references divided into the following areas that can be consulted for additional information sulfur- and nitrogen-containing macrocycles , porphyrins " and clusters . 

The assignment that the emissions arise from a LMCT [E M4] excited state with mixing of a metal-centered d sjd p) state has been substantiated by ab initio and Fenske-Hall molecular orbital calculations performed for the silver(I) clusters. These results revealed that the HOMOs of the clusters are principally Ag—E bonding orbitals, while the LUMOs are metal-localized orbitals with predominantly 55 and 5p character. Furthermore, the calculated HOMO-LUMO energy gaps decrease in the order (13a) > (13b) > (13c), consistent with the observed trend for the emission energies of the complexes. 

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