Ag Distance Research Articles

Insights into the xenon–silver halide interaction from a rotational spectroscopic study of XeAgF and XeAgCl

XeAgF and XeAgCl have been prepared by laser ablation of Ag metal in the presence of xenon and SF6 or xenon and Cl2, respectively. Rotational spectra for 12 isotopomers of XeAgF and 16 isotopomers of XeAgCl have been recorded. Analysis of the spectra indicates that (i) both chemical systems are unusually strongly bound compared to conventional van der Waals complexes, (ii) significant charge rearrangement occurs at the xenon nucleus upon formation of both XeAgF and XeAgCl as shown by the 131Xe nuclear quadrupole coupling constants and (iii) in both XeAgF and XeAgCl the Xe–Ag distance is small compared to the sum of the Xe van der Waals radius and the Ag+ ionic radius. An ab initio study of the two species has been performed. The combined experimental and theoretical investigations indicate that the Xe–Ag interaction is not easily described, but that there is some evidence for weak chemical bonding.

EXAFS and optical spectroscopy characterisation of reduction products of binary silver-copper ion mixture in mordenite

Ag+, Cu2+ and Ag + - Cu 2 + binary mixtures with different Ag/Cu ratios were supported on mordenite with Si/Al ratio equal to 10 and reduced in the temperature range 323-673 K. Diffuse Reflectance UV-Visible spectra reveal appearance of Ag8 clusters and small copper metal particles. Cu K-edge EXAFS show for Cu-rich non-reduced samples the presence of only oxygen shell; but for the Ag-rich sample, the presence of heavier backscatterer is also indicated producing a different EXAFS envelope. Silver EXAFS analysis suggests that, for the reduced samples, there are both Ag - O and Ag - Ag distances (Ag - Ag and Ag - O coordination numbers of approx 2 and of 1.3 respectively for the Ag/Cu = 3:1 and 1:3 samples). Importantly, for the reduced sample, the EXAFS indicates that Ag appears to promote/stabilise Cu cluster formation whereas Cu appears to impede/destabilise Ag cluster formation.

Synthesis and Structure of Redox‐Active Heterotetranuclear Molecular Polygons by Self‐Assembly of Two Ferrocene‐Bridged Bis(pyridines) with Two Transition Metals

AbstractThe macrocyclic complexes [(η5‐C5H4C2‐4‐py)2Fe]2Ni2(NO3)4 (2), [(η5‐C5H4C2‐3‐py)2Fe]2Ag2(ClO4)2 (4), and [(η5‐C5H4C2‐3‐py)2Fe]2Pd2Cl4 (5) were obtained by reaction of [Ni(H2O)6](NO3)2, AgClO4, and PdCl2(COD) with the ligands (η5‐C5H4C2‐4‐py)2Fe (1) and (η5‐C5H4C2‐3‐py)2Fe (3), respectively, under high dilution conditions (Scheme 1). The molecular motifs of 2, 4, and 5 were studied by single‐crystal X‐ray structural investigations. Elemental analyses and 1H NMR and IR spectra were also used to confirm the structures. Compound 2 represents an unsymmetric paddlewheel, in which the centers of the four Cp rings define a nearly ideal rectangle with dimensions of 20.2 × 3.3 Å. In principle, macrocycles 4 and 5 can also be described as rectangles, however, due to the 3‐positioned nitrogen donors with deformed edges (17.4 × 3.3 Å for 4). In contrast to the offset packing of the molecules in 2, the macrocycles in the crystal of 4 are aligned, with trapped acetonitrile molecules in between. The intra‐ and intermolecular Ag−Ag distances are 3.50 and 3.79 Å, respectively. Cyclovoltammetric studies reveal chemically reversible ferrocene‐based redox reactions of 1−4. Although no electronic communication was observed between the two identical ferrocene units, a weak through‐bond electronic interaction between ferrocene and nickel, or silver, was established. In 2 a weak antiferromagnetic interaction between the nickel atoms was also found. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Formation of novel discrete silver(i) coordination architectures with quinoline-based monothioethers: adjusting the intramolecular Ag⋯Ag distances and complex structures by ligands modifications and variations of counter anions

In our efforts to design discrete polynuclear metal complexes with tailored structures, four structurally related quinoline-based new monothioether ligands, 8-(2-pyridylsulfanylmethyl)quinoline (L1), 8-(4-pyridyl- sulfanylmethyl)quinoline (L2), 8-(2-pyrimidylsulfanylmethyl)quinoline (L3), 5-methyl-2-(8-quinolylmethyl- sulfanyl)-1,3,4-thiadiazole (L4) have been designed, and six new AgI complexes with these ligands, {[AgL1](ClO4)(CHCl3)}21, [Ag2L1(NO3)2]22, {[AgL1(CH3CN)](PF6)}23, [AgL2(NO3)]24, {[AgL3(CH3OH)](ClO4)}25 and {[AgL4](ClO4)}26 have been synthesized and characterized by single-crystal X-ray diffraction analysis. All six complexes adopt discrete structures, with 1,3,4,5 and 6 being dinuclear and 2 being tetranuclear, and Ag–Ag interactions were found to exist in complexes 1,2,3 and 6, as well as π–π stacking in 1–4. Furthermore, the Ag⋯Ag distances in 1–6 were compared. In the six complexes, the sulfur atoms of the ligands adopt quite different coordination modes: bridging in 1,2 and 3, chelating in 5 and non-coordination in 4 and 6. In addition, the structural differences of 1,2 and 3 indicate that the change in the counter anion greatly influences the coordination modes of the ligands and the coordination geometries of AgI ion, which consequently affects the resulting frameworks of such complexes.

Low-dimensional compounds containing cyano groups. III: a structural, spectral and thermal study of dicyanoargentates containing 4-methylpyridine

The complexes CuII(4-Mepy)2Ag2(CN)4(1) and CuII(4-Mepy)3Ag2−xCuIx(CN)4(2) (4-Mepy = 4-methylpyridine, x = 0.07) were isolated from a reaction mixture containing 4-Mepy, K[Ag(CN)2] and CuSO4. I.r. spectra indicated the presence of both monodentate and bridging cyano groups in (1) and (2), confirmed by their known structures, both consisting of neutral zigzag chains. Two neighbouring chains in (2) are linked by argentophilic interactions between Ag atoms of bridging dicyanoargentate anions, whose positions are partly occupied by CuI ions to the extent of 7 at.%, with an unusually short Ag...Ag distance of 2.9264(5) A, to form a ladder. Individual ladders are tied together as sheets by weaker argentophilic interactions between silver atoms of interdigitated monodentate dicyanoargentate anions of two different ladders. Thermal decomposition of (2) occurs in two separated stages. In the first stage, three 4-Mepy molecules are liberated from the formula unit and, in the second stage, redox decomposition of the cyano groups occurs. The thermal decomposition of (1) is more complicated as the release of two 4-Mepy molecules is overlapped by decomposition of one cyano group followed by further redox decomposition of the remaining cyano groups.

Bis[μ-bis(diphenylphosphino)amine-κP:P′]bis[acetonitrilesilver(I)] tris(cis-1,2-dicyanoethylene-1,2-dithiolate)molybdate(IV)

The reaction between the metal diphosphine [Ag2(dppa)2](BF4)2 [dppa is bis­(di­phenyl­phosphino)­amine, C24H21N2P2] and the metal thiol­ate [Bu4N]2[Mo(mnt)3] (mnt is cis-1,2-di­cyano­ethyl­ene-1,2-di­thiol­ate, C4N2S2) gave the title compound, [Ag2(dppa)2(MeCN)2][Mo(mnt)3]. The Ag⋯Ag distance of 2.9501 (13) Å is shorter than the sum of van der Waals radii for two Ag atoms, indicating a weak metal–metal contact in the complex. The cation lies on an inversion centre and the anion lies on a twofold axis.

Copper and Silver Triimidosulfites: S(NtBu)32--Bicapped M3-Triangles Connected via Lithium Halide Ladders or Fragments Thereof

Starting from the dilithium triimidosulfite dimer [Li 4 {(N t Bu) 3 S} 2 ], only three of the four lithium cations can be replaced by copper(I) cations in [(thf) 2 Cu 3 Li 2 I{(N t Bu) 3 S} 2 ] (1). In the isomorphous silver complex [(thf) 2 Ag 3 Li 2 Br{(N t Bu) 3 S} 2 ] (2), the cations are arranged in a triangle. Each metal is linearly coordinated by two imido nitrogen atoms, resulting in relatively short Cu...Cu (251.41 pm) and Ag...Ag (278.60 pm) distances. Two lithium cations are additionally coordinated to each S(N t Bu) 3 2 cap. They pincer a single halide anion. [(thf)-Ag 3 Li 2 Br{(N t Bu) 3 S} 2 ] 2 (3) and [(thf) 2 Ag 3 Li 3 Br 2 {(N t Bu) 3 S} 2 ] 2 (4) show an increasing content of lithium bromide. In 3 a two-rung and in 4 a four-rung LiBr ladder is terminated by a LiM 3 {(N t Bu) 3 S} 2 unit. In [(thf) 2 Li 3 Cl{(N t Bu) 3 S}] 2 (5), no LiCl ladder extension is observed presumably because the Li 2 (N t Bu) 3 S terminating moiety meets the requirements of the cubic LiCl solid-state lattice.

Experimental and theoretical study of the MgO/Ag( [formula omitted]) interface

We report on a joint experimental and theoretical investigation of the structure of the MgO/Ag(0 0 1) interface, with emphasis on the determination of the interfacial distance between the Ag surface and the first MgO(0 0 1) plane. Experiments were performed on 1–5 ML thick MgO layers prepared by Mg deposition in a controlled oxygen atmosphere on a sputter-annealed Ag substrate. The intensity angular distribution (IAD) of the Ag LMM Auger emission was measured as a function of the incidence angle of the primary exciting beam, and the interfacial atomic arrangement was determined by modelling the IAD in a single-scattering cluster approximation. The model adopted in theoretical calculations consisted in a two-dimensionally periodic structure composed of a six-layer thick slab of Ag parallel to the (0 0 1) face, covered on both sides by one or two epitaxial MgO MLs. An ab initio density functional theory approach was used with different types of exchange-correlation functionals, and full geometry optimisations were performed. It has been found that MgO accommodates on the substrate with O atoms sitting just on top of the Ag atoms, and that the distance between the Ag surface and the first MgO plane is expanded with respect of both Ag and MgO(0 0 1) interplanar distances. Experimental and theoretical results both indicate for the interfacial distance a value of 2.39±0.06 Å. Significant rumpling occurs in the first ML of MgO, that is removed as the overlayer thickness increases.

Synthesis and Crystal Structure of a Polymeric Heteronuclear Complex of Cadmium(II) and Silver(I)

A polymeric complex of Cd(II) and Ag(I) bridged by thiocyanate and ethylenediamine, [Cd(en)1.5Ag(SCN)3], has been prepared and its structure determined by X-ray diffraction methods. The complex crystallizes in space group P21/n with a =7.456(1), b =9.915(2), c =19.822(2)Å, β =98.94(1)°. The Cd(II) atom is octahedrally coordinated by three SCN- anions and two en molecules, while the Ag(I) atom is tetrahedraly coordinated by four SCN- anions. Both SCN- anions and en molecules act as bridging ligands and link Ag(I) and Cd(II) atoms to form a three-dimensional polymeric structure. The distance between Ag(I) and the atom S of a 1,1,3-µ3-SCN- anion is much longer than that between Ag(I) and the atom S of a 1,3-µ-SCN- anion. The short Ag-Ag distance of 3.133 Å and small Ag-S-Ag angle of 70.92° strongly suggests the existence of an Ag-Ag bonding interaction in the complex.

Coordination networks of Ag(i) and N,N′- bis(3-pyridinecarboxamide)-1,6-hexane: structures and anion exchange

A bidentate ligand N,N′- bis(3-pyridinecarboxamide)-1,6-hexane (L) and its silver complexes have been synthesized and characterized by single crystal X-ray diffraction. Reaction of AgClO4 and L in H2O/EtOH gives rise to a coordination polymer [Ag2L3OH][ClO4]·2.5H2O. The X-ray crystal structure of the compound shows honeycomb-like networks in which four-coordinated Ag ions are linked to three-coordinated Ag ions via three ligands L. The coordination of the long ligands L to the Ag ions creates tube-like structures and the tubes of adjacent honeycomb layers are interlocked, leading to an interpenetrating network. The compound [AgL][ClO4], synthesized from CH3OH, is composed of twisted zigzag coordination polymers in which ligands L are linked by Ag ions. Ligand L displays two different conformations A and B within a single strain of polymer. The two conformers differ in the orientation of the two pyridyl-groups which are arranged periodically in the polymer in the sequence ABBABBA. The polymer chains assemble into 2-D undulating sheets via amide hydrogen bonds. Reaction between AgNO3/AgCF3SO3 and L leads to polymeric compounds [AgL][NO3] and [AgL][CF3SO3]. The compounds are composed of coordination polymers in zigzag conformation and the polymer chains assemble into undulating sheets via inter-chain hydrogen bonds. The inter-sheet Ag–Ag distances of the compounds are in the order [AgL][CF3SO3] > [AgL][ClO4] > [AgL][NO3]. The anion exchange properties of the compounds are monitored by using X-ray powder diffraction, infrared spectroscopy and elemental analysis. Our results show that the anions in [AgL][NO3] and [AgL][CF3SO3] can be totally replaced with ClO4−. However, the exchange is not reversible. In additional, inter-conversion between [AgL][NO3] and [AgL][CF3SO3] by anion exchange is shown to be unfeasible. Anion selectivity could be due to the different hydration energy of the anions and the structural reorganization involved in the conversion.

Synthesis and circular dichroism spectra of silver(I) complexes with R, R-DIOP (4 R,5 R- trans-4,5-bis[(diphenylphosphino)methyl]-2,2-dimethyl-1,3-dioxalane): crystal structures of [AgCl( R, R-DIOP)] 2·2CHCl 3, {[AgBr( R, R-DIOP)] 2} 2·CH 2Cl 2·2H 2O, [AgI( R, R-DIOP)] 2 and [AgSCN( R, R-DIOP)] 2

The title silver(I) complexes as [AgX( R, R-DIOP)] 2 dimers (X=Cl, Br, I or SCN) were synthesized either by the reaction of [Ag(NO 3)( R, R-DIOP)] n with NaX or the reaction of AgX with R, R-DIOP. The complexes were confirmed by elemental analysis, IR, 1H- and 31P-NMR, UV–vis and circular dichroism (CD) spectra, as well as single-crystal X-ray characterization. X-ray analysis showed that the silver atoms are tetrahedral, surrounded by two bridged halides and two phosphorus atoms of the bridged R, R-DIOP ligands. The Ag⋯Ag distances, ranging from 3.065(6) to 3.724(1) Å, are dependent on the polarizability of the halide anions. All of the solid-state structures of the complexes are crystallized in triclinic, space group P1 (no. 1). The CD spectra of these complexes demonstrate their chirality, and their Cotton effects vary according to the different halides, i.e. a negative band (at 241 nm) for 1 (X=Cl), a positive one for 2 (X=Br) and 3 (X=I), and a strong positive band for 4 (X=SCN).

EXAFS studies of the local thermal expansion in borate glasses

Temperature-dependent EXAFS measurements have recently been made on the silver borate glass [Ag 2O·4B 2O 3], and the superionic AgI-doped glass [AgI] 0.75[3Ag 2O·1B 2O 3] 0.25. The Ag–O co-ordination has been studied in the first sample, the I–Ag in the second one. In both cases a significant reduction of the first shell inter-atomic distance has been observed as temperature increases from 15 to 300 K. Here a detailed analysis of the EXAFS results for the AgI-doped glass is presented. The distributions of first shell I–Ag distances reconstructed from EXAFS for the glass and c-AgI, and their leading statistical parameters, are compared and critically discussed. The local negative expansion in the glass is partially attributed to the relaxation of the a-AgI network within the host binary matrix.

Ring-opening polymerisation of silver-diphosphine [M2L3] coordination cages to give [M2L3]infinity coordination polymers.

[M2L3] coordination cages and linear [M2L3]infinity polymers of the rigid, bridging diphosphines bis(diphenylphosphino)acetylene (dppa) and trans-1,2-bis(diphenylphosphino)ethylene (dppet) with silver(I) salts have been investigated in the solution and solid states. Unlike flexible diphosphines, 1:1 dppa/AgX mixtures do not selectively form discrete [Ag2(diphos)2(X)2] macrocycles; instead dynamic mixtures of one-, two- and three-coordinate complexes are formed. However, 3:2 dppa/AgX ratios (X = SbF6. BF4, O3SCF3 or NO3) do lead selectively to new [M2L3] triply bridged cage complexes [Ag2(dppa)3(X)2] 1a-d (X = SbF6 a, BF4 b, O3SCF3 c, NO3 d), which do not exhibit Ag-P bond dissociation at room temperature on the NMR time scale (121 MHz). Complexes la-d were characterised by X-ray crystallography and were found to have small internal cavities, helical conformations and multiple intramolecular aromatic interactions. The nucleophilicity of the anion subtly influences the cage shape: Increasing nucleophilicity from SbF6 (1a) through BF4 (1b) and O3SCF3 (1c) to NO3 (1d) increases the pyramidal distortion at the AgP3 centres, stretching the cage framework (with Ag...Ag distances increasing from 5.48 in 1a to 6.21 A in 1d) and giving thinner internal cavities. Crystal packing strongly affected the size of the helical twist angle, and no correlation between this parameter and the Ag-Ag distance was observed. When crystalline 1c was stored in its supernatant for 16 weeks, conversion occured to the isostoichiometric [M2L3]infinity coordination polymer [Ag(dppa)2Ag(dppa)(O3SCF3)2]infinity (1c'). X-ray crystallography revealed a structure with ten-membered Ag2(dppa)2 rings linked into infinite one-dimensional chains by a third dppa unit. The clear structural relationship between this polymer and the precursor cage 1c suggests a novel example of ring-opening polymerisation. With dppet, evidence for discrete [M2L3] cages was also found in solution, although 31P NMR spectroscopy suggested some Ag-P bond dissociation. On crystallisation, only the corresponding ring-opened polymeric structures [M2L3]infinity could be obtained. This may be because the greater steric bulk of dppet versus dppa destabilises the cage and favours the ring-opening polymerisation.

Local structure of silver clusters in the channels of zeolite 4A.

The Ag K-edge EXAFS measurements have been carried out at 50 K for fully Ag+-exchanged zeolite 4A (Ag-4A) dehydrated at different temperatures under vacuum. In the Fourier transforms of the EXAFS oscillation the two distinct peaks appear around 2.2 A and 3.0 A, and a shoulder around 2.8 A. The structural parameters (distance, coordination number and root mean square displacement) were derived by a three-shell (two Ag-O contacts and Ag-Ag contact) curve-fitting analysis. It is found that a silver cluster is formed with Ag-Ag distance 2.82+/-0.02 A and coordination number 4.9+/-0.2. When the silver cluster is formed 6 Ag0 atoms and 8 Ag+ ions are arranged in a cubic closed-packed manner in the cage of the Ag-4A zeolite. The 8 Ag+ ions and 6 Ag0 atoms are confined in the framework of oxygens at distances of 2.28+/-0.02 and 2.88+/-0.02 A, respectively.

Design and properties of mixed metal multinuclear molecules: Part 1. Molecular structures of [Ag(PR 3) 2] 2[Ni(mnt) 2] type complexes (R=Me, Et, Cy and mnt=maleonitriledithiolate) and [AgL] 2[Ni(mnt) 2] type complexes with chelating diphosphines (L=dppf and dppm)

The trinuclear complexes [Ag(PR 3) 2] 2[Ni(mnt) 2] and [AgL] 2[Ni(mnt) 2] have been prepared by reactions of (NEt 4) 2[Ni(mnt) 2] and Ag 2SO 4 with alkyl phosphines (PR 3=P(CH 3) 3 (PMe 3) for 1, P(C 2H 5) 3 (PEt 3) for 2 and P(C 6H 11) 3 (PCy 3) for 3), or with chelating diphosphines (L=1,1′-bis(diphenylphosphino)ferrocene (dppf) for 4 and bis(diphenylphosphino)methane (dppm) for 5). The structures of all the complexes have been determined by X-ray crystallography. Interactions between the [Ag(PR 3) 2] + and [Ni(mnt) 2] 2− groups occur in compounds 1 and 2 with NiAg distances of 3.063(4) and 2.9311(6) Å, respectively. Only one sulfur atom of each mnt ligand bridged [Ag(PR 3) 2] + cations and [Ni(mnt) 2] 2− anions in compound 1 through 3 with AgS distances of about 2.7 Å. There is no interaction between Ag and Ni in compound 3 due to the flexibility of the cyclohexyl groups. Interactions between [AgL] + and [Ni(mnt) 2] 2− groups also occur in compound 4 with a much shorter AgNi distance of 2.7213(7) Å, while silver atoms and the NiS 4 plane in compound 4 make a chair conformation with AgS distances of about 2.8 Å. In compound 5, dppm bridges two silver atoms, and interaction between silver atoms occurs at a distance of 2.9859(11) Å, and only one sulfur atom of mnt is used to bridge Ni and Ag atoms with AgS distances of 2.582(3) and 2.663(3) Å.

Ni(tn) 2Ag 2(CN) 4 and Cu(tn) 2Ag 2(CN) 4 (tn=1,3-diaminopropane): preparation, crystal structure, magnetic and spectral properties

Two new compounds, Ni(tn) 2Ag 2(CN) 4 (tn=1,3-diaminopropane) (NTAC) and Cu(tn) 2Ag 2(CN) 4 (CTAC), were prepared, and their structures were determined by single crystal X-ray diffraction. The structure of NTAC consists of individual centrosymmetric trinuclear molecules, in which the nickel atom is coordinated by two chelate-bonded tn molecules placed in the equatorial plane and two diacyanoargentate anions bonded via one μ-CN group. The trinuclear molecules interact together via short Ag⋯Ag contacts (3.2627(3) Å) forming a chain-like arrangement of molecules. The structure of CTAC is ionic and consists of [(tn) 2Cuμ-NCAgCN] + binuclear complex cations and two free crystallographically independent [Ag(CN) 2] − anions. In CTAC, the silver atoms are close to each other, forming a bent chain-like Ag⋯Ag⋯Ag arrangement with alternating Ag⋯Ag distances of 3.2270(3) and 3.4166(3) Å. Experimental studies of the susceptibility and magnetization support the assumption about extremely weak magnetic correlations in both systems. The analysis of the NTAC susceptibility has revealed the significant effect of single ion anisotropy, ∣ D∣/ k B≈3 K, which governs the magnetic behavior of this material below 6 K.

The ligand [Cp 2MoH 2] in complexes with AgS bonds

The reaction of [Cp 2MoH 2] and AgBF 4 with the dithio-ligands Na(S 2CNR 2) (R=Et, Ph), Na(S 2CMe), NH 4(S 2P(OEt) 2) and K(S 2CO i Pr) gives the complexes [(Cp 2MoH 2AgS 2CNR 2) 2] (R=Et 1, Ph 2), [(Cp 2MoH 2AgS 2CMe) 2] ( 3), [(Cp 2MoH 2AgS 2P(OEt) 2) 2] ( 4) and [(Cp 2MoH 2AgS 2CO i Pr) n ] ( 6) with probably n=2, all with a [Cp 2MoH 2]:Ag:dithio-ligand stoichiometry of 1:1:1. 1– 4 form dimers in which two dithio-ligands bridge two silver atoms. In 1 and 2 one sulphur atom is coordinated to one silver atom, whereas the other is coordinated to both silver atoms. In 3 and 4 each sulphur atom is bonded to one silver atom only. In 1– 3 there is a silversilver bond. However, in 4 the Ag⋯Ag distance is too long for an AgAg bond. Crystallization of the compound 6 afforded a polymer [(Cp 2MoH 2Ag 4(S 2CO i Pr) 4) n ] ( 7) with a stoichiometry [Cp 2MoH 2]:Ag:dithio-ligand=1:4:4. The polymer forms sheets with rings surrounding a [Cp 2MoH 2] ligand bonded to one of the four silver atoms. The monomer [(Cp 2MoH 2) 2AgS 2COEt] ( 5) with a stoichiometry [Cp 2MoH 2]:Ag:dithio-ligand=2:1:1 was prepared by addition of Na(S 2COEt) to [Cp 2MoH 2] and AgBF 4. In 5 the xanthogenate ligand is bonded with both sulphur atoms to the silver atom. The compounds 1– 6 were characterized analytically and spectroscopically. The structures of 1– 5 and 7 were determined by single crystal X-ray analyses.

Synthesis and characterization of water-soluble silver(I) complexes with L-histidine (H2his) and (S)-(-)-2-pyrrolidone-5-carboxylic acid (H2pyrrld) showing a wide spectrum of effective antibacterial and antifungal activities. Crystal structures of chiral helical polymers [Ag(Hhis)]n and ([Ag(Hpyrrld)]2)n in the solid state.

Two water-soluble, silver(I) complexes showing a wide spectrum of effective antibacterial and antifungal activities, i.e., ([Ag(Hhis)].0.2EtOH)2 (1; H2his = L-histidine) and [Ag(Hpyrrld)]2 (3; H2pyrrld = (S)-(-)-2-pyrrolidone-5-carboxylic acid) were prepared. In aqueous solution 1 and 3 were present as dimers, whereas in the solid state they were polymers. Crystallization of 1 by slow evaporation and/or vapor diffusion gave water-insoluble crystals of [Ag(Hhis)]n (2) showing modest antimicrobial activities. The complex 1 in the solid state is a polymer formed by intermolecular hydrogen-bonding interactions between dimeric [Ag(Hhis)]2 cores, while 2 is a different polymer without a core complex. X-ray crystallography revealed that 2 was a left-handed helical polymer consisting of a bent, 2-coordinate silver(I) atom bonding to the Namino atom of one Hhis- ligand and the N pi atom of a different Hhis- ligand. Of particular note is the fact that Ocarboxyl atoms do not participate in the coordination. X-ray crystallography also revealed that 3 was a left-handed helical polymer formed by self-assembly of dimeric [Ag(Hpyrrld)]2 cores with an intramolecular metal(I)-metal(I) interaction (Ag-Ag distance, 2.9022(7) A). The FT-IR and the solid-state 13C and 15N NMR spectra showed that the dimeric core of 1 was formed through Ag-N bonds, while that of 3 was formed through Ag-O bonds. The molecular ions of 1 and 3 were detected by the positive-ion electrospray ionization (ESI) mass spectrometry. For 1-3, characterization by elemental analysis, TG/DTA, FT-IR, and variable-temperature solid-state 13C NMR and room-temperature 15N NMR measurements was performed, and for 1 and 3, that by solution molecular weight measurements and solution (109Ag, 1H, and 13C) NMR spectroscopies was also carried out. The antibacterial and antifungal activities of 1 and 3 were remarkable and comparable to those of the previous silver(I)-N-heterocycle complexes.

Synthesis and Structure of Dimeric Silver Azooximates. Hydrogen Bonding and Nonbonded Ag···Ag Interaction

The title azooximes PhNNC(R)NOH, HRL (R = Me, Ph), 1, have afforded [Ag(MeL)(HMeL)2]2, 2, and [Ag(PhL)(HPhL)]2, 3. In 2, only oxime N is coordinated and the AgN3 fragment has a distorted-T shape. In 3, the ligand is chelating, the AgN4 tetrahedron being highly squashed. Strong O···O hydrogen bonds characterize the species. The Ag···Ag distances are, respectively, shorter and longer than the van der Waals sum in 3 and 2.

Cs3AgAs4Se8 and CsAgAs2Se4: selenoarsenates with infinite 1 infinity[AsSe2]- chains in different Ag+ coordination environments.

Two quaternary silver selenoarsenates Cs3AgAs4Se8 (I) and CsAgAs2Se4 (II) have been discovered by methanothermal reaction of Li3AsSe3 with AgBF4 in the presence of the respective alkali metal sources Cs2CO3 and CsCl. Orange crystals of Cs3AgAs4Se8 (I) were formed after reaction at 120 degrees C for 72 h, whereas red CsAgAs2Se4 (II) was obtained under slightly different conditions at 140 degrees C for 70 h. Both compounds possess novel two-dimensional (2D) polyanions consisting of infinite 1 infinity[AsSe2]- chains that are interconnected by Ag+ ions in different coordination patterns. In I, a double layer of 1 infinity[AsSe2]- chains is bridged by distorted trigonal planar coordinated Ag+ atoms to form a 2 infinity[AgAs4Se8]3- layer with a thickness of about 11.3 A. The nonbonding Ag...Ag distances are about 4.220 A, and large cavities within the layers accommodate for three of the four crystallographic Cs+ cations. The double amount of Ag+ atoms per AsSe2 chain unit in II leads to simple layers 2 infinity[AgAs2Se4]- [=[Ag2As4Se8]2-] in which the Ag+ atoms are arranged in rows between the 1 infinity[AsSe2]- chains, with alternating Ag...Ag distances of 3.053(3) and 3.488(3) A. Hereby the 1 infinity[AsSe2]- polyanions show a disorder within the central (-As-Seb)- chain (b = bridging), while the positions of the terminal Se atoms (Set) remain unaffected. The thermal, optical, and spectroscopic properties of the compounds are reported. Both I and II melt with decomposition and are wide band gap semiconductors with values of 2.07 and 1.79 eV, respectively. Raman spectroscopic data show typical band patterns expected for infinite [AsSe2]- chains. Crystal Data: Cs3AgAs4Se8 (I), monoclinic, C2/c, a = 25.212(2) A, b = 8.0748(7) A, c = 22.803(2) A, beta = 116.272(2) degrees, Z = 8; CsAgAs2Se4 (II), monoclinic, P2(1)/n, a = 10.9211(1) A, b = 6.5188(2) A, c = 13.7553(3) A, beta = 108.956(1) degrees, Z = 4.