Silver Coordination Research Articles

Silver(I) coordination polymers assembled from flexible cyclotriphosphazene ligand: structures, topologies and investigation of the counteranion effects.

The reactions of a flexible ligand hexakis(3-pyridyloxy)cyclotriphosphazene (HPCP) with a variety of silver(I) salts (AgX; X = NO3(-), PF6(-), ClO4(-), CH3PhSO3(-), BF4(-) and CF3SO3(-)) afforded six silver(I) coordination polymers, namely {[Ag2(HPCP)]·(NO3)2·H2O}n (1), {[Ag2(HPCP)(CH3CN)]·(PF6)2}n (2), {[Ag2(HPCP)(CH3CN)]·(ClO4)2}n (3), [Ag3(HPCP)(CH3PhSO3)3]n (4), [Ag2(HPCP)(CH3CN)(BF4)2]n (5) and {[Ag(HPCP)]·(CF3SO3)}n (6). All of the isolated crystalline compounds were structurally determined by X-ray crystallography. Changing the counteranions in the reactions, which were conducted under similar conditions of M/L ratio (1:1), temperature and solvent, resulted in structures with different types of topologies. In complexes (1)-(6), the ligand HPCP shows different coordination modes with Ag(I) ions giving two-dimensional layered structures and three-dimensional frameworks with different topologies. Complex (1) displays a new three-dimensional framework adopting a (3,3,6)-connected 3-nodal net with point symbol {4.6(2)}2{4(2).6(10).8(3)}. Complexes (2) and (3) are isomorphous and have a two-dimensional layered structure showing the same 3,6L60 topology with point symbol {4.2(6)}2{4(8).6(6).8}. Complex (4) is a two-dimensional structure incorporating short Ag...Ag argentophilic interactions and has a uninodal 4-connected sql/Shubnikov tetragonal plane net with {4(4).6(2)} topology. Complex (5) exhibits a novel three-dimensional framework and more suprisingly contains twofold interpenetrated honeycomb-like networks, in which the single net has a trinodal (2,3,5)-connected 3-nodal net with point symbol {6(3).8(6).12}{6(3)}{8}. Complex (6) crystallizes in a trigonal crystal system with the space group R\bar 3 and possesses a three-dimensional polymeric structure showing a binodal (4,6)-connected fsh net with the point symbol (4(3).6(3))2.(4(6).6(6).8(3)). The effect of the counteranions on the formation of coordination polymers is discussed in this study.

Cobalt(II)/silver(I) coordination polymers with bis(2-methylbenzimidazole) and polycarboxylate ligands

Three coordination polymers, [Co(L)(tbta)]n (1), [Ag(L)(H2O)·(Hhpht)]n (2) and [Ag2(L)1.5(oba)]n (3) (L = 1,4-bis(2-methylbenzimidazol-1-ylmethyl)benzene, H2tbta = tetrabromoterephthalic acid, H2hpht = homophthalic acid, H2oba = 4,4′-oxybis(benzoic acid)), have been hydrothermally synthesized and structurally characterized. Complex 1 displays a 2-D uninodal 4-connected sql network, 2 and 3 feature chain structures, which further generate 2D supramolecular networks through hydrogen bonding interactions. The thermal and fluorescence properties of 1–3 have been carried out and discussed.

Influence of Flexible Bis(benzimidazole) Derivatives on the Self‐assembly of Three Mixed Ligands Silver(I) Coordination Polymers

AbstractThree silver(I) coordination polymers namely, [Ag4(L1)2(1, 4‐ndc)2]n (1) {[Ag(L2)]·(1, 4‐Hndc)·H2O}n (2), and {[Ag(L3)(H2O)]·(1, 4‐Hndc)}n (3) [L1 = 1, 3‐bis(benzimidazol‐1‐ylmethyl)benzene, 1, 4‐H2ndc = 1, 4‐naphthalenedicarboxylic acid, L2 = 1, 3‐bis(5, 6‐dimethylbenzimidazole‐1‐ylmethyl)benzene, L3 = 1, 4‐bis(5, 6‐dimethylbenzimidazole)butane], were hydrothermally synthesized and characterized by single‐crystal X‐ray diffraction analysis, elemental analysis, IR spectroscopy, thermogravimetric and XRPD analysis. Complex 1 displays a 1D tube‐like chain, which is packed into a 3D supramolecular network by π–π stacking interactions. Complex 2 features an infinite 1D linear chain. Complex 3 contains a 1D wave‐like chain, which is extended into a 3D supramolecular network through O–H···O hydrogen bonding interactions. Moreover, these coordination polymers exhibit catalytic properties for degradation of methyl orange in Fenton‐like processes.

Silver Coordination Polymers Based on Newly Designed Bis(cyanobenzyl)bipiperidine Ligand: Synthesis, Anion Exchange, Guest Inclusion, Electrochemical, and Photoluminescence Properties

A new flexible ligand, bis(cyanobenzyl)bipiperidine (L), has been synthesized and structurally characterized. Nine novel silver(I) coordination polymers (CPs), the dimensionality of which depends on the counteranion, [Ag2(L)(NO3)2]n (1), [Ag2(L)(NO3)2]n (2), {[Ag2(L)(NO3)2)](C16H10)}n (3), {[Ag2(L)(NO3)2)](C20H12)}n (4), [Ag2(L)(ClO4)2]n (5), [Ag2(L)(CF3SO3)2(C4H8O)2]n (6), [Ag2(L)(CF3SO3)2(C3H6O)2]n (7), {[Ag2(L)2]·(BF4)·2(C3H6O)}n (8), and [Ag2(L)3(PF6)2]·x(C3H6O) (9), have been prepared by self-assembly of L with AgX (X = NO3–, ClO4–, CF3SO3–, BF4–, and PF6–) and aromatic guest molecules. Reactions of L with AgNO3 in acetone in either 1:2 or 1:1 stoichiometric ratio occurred rapidly at room temperature, yielding topologically different structural isomers of the three-dimensional (3D) CPs 1 and 2. Additional reactions of linker L with AgNO3 in the presence of aromatic guest molecules (pyrene, perylene) formed CPs of 3 and 4 with the inclusion of the corresponding guest in the crystal lattice associated ...

Synthesis, crystal structures and photoluminescences of silver(I) complexes with chelating carboxylic and pyrazine derivatives

Four mixed-ligand silver(I) coordination polymers (CPs) {Ag2(tpyz)(L)}_n (1), {Ag4(tpyz)2(L)2}_n (2), {Ag2(mpyz)(L)}_n (3) as well as its isomer (4), (tpyz-2,3,5-trimethylpyrazine, mpyz=2,3,5,6-tetramethylpyrazine, H2L=(+)-camphoric acid), were synthesized with reactions of L and pyrazine derivatives with silver nitrate in different solvent systems. Systematic characterizations with single-crystal X-ray diffraction indicate that, 1 and 3 show a 3D framework which constructed by silver(I) and L anion, the pyrazine derivatives only give one N to connect to metal, which may be due to the disorder of the methyl which shares the same carbon with carboxylate; 2 and 4 demonstrate a 2D 44–sql network. The difference between two: one structure is single layer and the other is double layer. Furthermore, 4 contains a 1D helical chains which connected by Ag(I) and mpyz ligand. Meanwhile, the L anion exhibits different coordination modes in 1–4. 1–4 spanning from two-dimensional network to three-dimensional framework suggest that the kinds of pyrazine derivatives and solvents play significant roles in the formation of such coordination architectures. The thermogravimetric analyses (TGA), IR, and photoluminescence were also measured.

Structural variability of Ag(I) metal–organic networks: C–H⋯π and metal⋯π interactions

The synthesis and X-ray structural characterization of two silver(I) coordination polymers, [Ag2(bpp)2(Phdac)]·5H2O (1) and [Ag2(bpp)(HSSal)] (2), are reported, where bpp = 4,4′-trimethylene dipyridine, H2Phdac = 1,4-phenylenediacetic acid, and H3SSal = 5-sulfosalicylic acid. X-ray crystallography reveals that the structures are stabilized through hydrogen bonding interactions. The C–H⋯π and metal⋯π interactions of aromatic molecules play a crucial role in building a layered framework. Intricate combinations of the weak non-covalent interactions have been analyzed to explore cooperativity and competitiveness in the solid-state structures.

A silver coordination cage assembled from [Ag2(bis(isoxazolyl))3]: DFT approach to the binding forces within the host–guest interactions

The storage and detection of different types of molecules using porous materials such as metal–organic frameworks (MOFs) have currently become an area of interest in chemistry.

Inverted molecular cups: 1-D and 2-D Ag(i) coordination polymers from resorcinarene bis-thiacrowns

Exo-cavity binding into resorcinarene based inverted molecular cups creates 1-D and 2-D silver coordination polymers with argentophilic interactions.

Molecular tectonics: dimensionality and geometry control of silver coordination networks based on pyrazolyl appended thiacalixarenes

Combinations of six new tetrakis-pyrazolyl appended calix[4]arenes derivatives, blocked in 1,3-A conformation as coordinating tectons, with AgX salts (X = NO3−, BF4−, XF6−(X = P, As and Sb)) lead to nine new silver coordination networks.

Antibacterial activity of silver camphorimine coordination polymers.

Five new silver camphorimine complexes of general formula [Ag(NO3)(Y)L] were synthesized and fully characterized using spectroscopic and analytical techniques. The structure of [Ag(NO3)(OC10H14NC6H4NC10H14O)] () was analyzed using single crystal X-ray diffraction, showing that it arranges as a coordination polymer formed by sequential Ag(NO3) units bridged by the bi-camphor ligand (). The antimicrobial properties of the new complexes were screened using the disk diffusion method and their Minimal Inhibitory Concentrations (MIC) were assessed against selected bacterial strains of the Gram-positive Staphylococcus aureus and the Gram-negative Escherichia coli, Pseudomonas aeruginosa, and Burkholderia contaminans. The lowest MICs were observed for , with estimated values of 72, 20, 32 and 19 μg mL(-1) for S. aureus, E. coli, B. contaminans, and P. aeruginosa, respectively. In the case of S. aureus, similar MIC values were obtained for silver nitrate and compound . All five compounds were bactericidal when used in concentrations equal or above the MIC value, as found by enumerating the total colony forming units (CFUs) after incubation in their presence.

Self‐Assembly and Characterization of Three‐Dimensional Silver(I) Coordination Polymers Containing N,N,N′,N′‐Tetrakis(pyridin‐4‐yl)methanediamine

Silver(I) coordination polymers, [Ag(tpmd)](NO3 )·2CH3OH (1), [Ag(tpmd)](CF3SO3 ) (2), and [Ag(tpmd)](CF3CO2 )·0.5CH3OH (3), have been obtained by the self‐assembly of AgX (X = NO3 −, CF3SO3 −, CF3CO2 −) and N,N,N′,N′‐tetrakis(pyridin‐4‐yl)methanediamine (tpmd) in MeOH/MeCN. The coordination geometries of silver(I) ions in 1 and 2 are distorted tetrahedral structures, while that of 3 is a distorted trigonal bipyramid. 1 and 2 feature three‐dimensional coordination polymers formed by coordination of the silver(I) ions to the tpmd ligands. 3 shows two‐dimensional network basically. However, the network of 3 can be considered three‐dimensional structure by the weak axial bonding of the fourth pyridine group from another tpmd ligand. 1–3 display strong emissions at 331, 342, and 326 nm, respectively.

XAS Investigation of Silver(I) Coordination in Copper(I) Biological Binding Sites.

Silver(I) is an unphysiological ion that, as the physiological copper(I) ion, shows high binding affinity for thiolate ligands; its toxicity has been proposed to be due to its capability to replace Cu(I) in the thiolate binding sites of proteins involved in copper homeostasis. Nevertheless, the nature of the Ag(I)-thiolate complexes formed within cells is poorly understood, and the details of Ag(I) coordination in such complexes in physiologically relevant conditions are mostly unknown. By making use of X-ray absorption spectroscopy (XAS), we characterized the Ag(I) binding sites in proteins related to copper homeostasis, such as the chaperone Atox1 and metallothioneins (MTs), as well as in bioinspired thiolate Cu(I) chelators mimicking these proteins, in solution and at physiological pH. Different Ag(I) coordination environments were revealed: the Ag-S bond length was found to correlate to the Ag(I) coordination number, with characteristic values of 2.40 and 2.49 Å in AgS2 and AgS3 sites, respectively, comparable to the values reported for crystalline Ag(I)-thiolate compounds. The bioinspired Cu(I) chelator L(1) is proven to promote the unusual trigonal AgS3 coordination and, therefore, can serve as a reference compound for this environment. In the Cu(I)-chaperone Atox1, Ag(I) binds in digonal coordination to the two Cys residues of the Cu(I) binding loop, with the AgS2 characteristic bond length of 2.40 ± 0.01 Å. In the multinuclear Ag(I) clusters of rabbit and yeast metallothionein, the average Ag-S bond lengths are 2.48 ± 0.01 Å and 2.47 ± 0.01 Å, respectively, both indicative of the predominance of trigonal AgS3 sites. This work lends insight into the coordination chemistry of silver in its most probable intracellular targets and might help in elucidating the mechanistic aspects of Ag(I) toxicity.

Anion-directed assembly of two AgI complexes based on 2,2'-(4H-1,2,4-triazole-3,4-diyl)dipyridine

Reaction of the Ag+ ions with 2,2'-(4H-1,2,4-triazole-3,4-diyl)dipyridine (L22) in the presence of NO3- and CH3SO3-, respectively, affords two silver(I) coordination compounds, namely {[Ag3(NO3)2(C12H9N5)2](NO3)]}n (I) and [Ag(CH3SO3)(C12H9N5)]2 (II). Both complexes have been characterized by single-crystal X-ray diffraction (CIF file CCDC nos. 1051589 (I) and 1051590 (II)). In complex I, the adjacent metal centers are interconnected via L22 ligands to afford a 1D coordination chain. Complex II shows the discrete cage-like binuclear coordination pattern with the Ag···Ag distance of 4.358(1) A.

Silver coordination complexes of 2-(diphenylphosphinomethyl)aminopyridine with weakly interacting counterions

A tri-functional ligand (Ph2PCH2)NH(2-C5H4N), DPAP-2, has been synthesized via the Mannich condensation reaction and its coordination behavior has been studied with various Ag(I) salts. The ligand is capable of P-coordination, P,N-chelation, and P,N-bridging to form Ag(I) complexes that range from discrete to 1-dimensional polymeric structures. In the 1:2 reaction of AgBF4 with DPAP-2, a 4-coordinate Ag(I) structure with P,N′-chelation is isolated (1). A counterion effect is observed in the equimolar reactions of AgX (2: X=BF4− and 3: X=tfa−) with DPAP-2, where the structures isolated are a dimer and a 1-dimensional polymer, respectively. When an equivalent of 5,5′-dimethyl-2,2′-dipyridyl (5,5′-dmbpy) was incorporated to the equimolar reaction of AgX and DPAP-2, three isostructural complexes resulted (4: X=BF4−, and supplementary structures S1: X=tfa−, and S2: X=OTf−). In the 2:1:2 reaction of AgX (5: X=BF4− and 6: X=tfa−) with DPAP-2 and 5,5′-dmbpy, two distinct complexes are isolated where DPAP-2 adopts a syn- and anti-arrangement, respectively.

Directional Energy Transfer in Mixed-Metallic Copper(I)–Silver(I) Coordination Polymers with Strong Luminescence

Strongly luminescent mixed-metallic copper(I)-silver(I) coordination polymers with various Cu/Ag ratio were prepared by utilizing the isomorphous relationship of the luminescent parent homometallic coordination polymers (Φ(em) = 0.65 and 0.72 for the solid Cu and Ag polymers, respectively, at room temperature). The mixed-metallic polymer with the mole fraction of copper even as low as 0.005 exhibits a strong emission (Φ(em) = 0.75) from only the copper sites as the result of the efficient energy migration from the silver to the copper sites. The migration rates between the two sites were evaluated from the dependence of emission decays upon the mole fraction of copper.

Assembly of three new POM-based Ag(I) coordination polymers with antibacterial and photocatalytic properties

Three new silver coordination polymers, namely, {Ag3(bpy)6[PW12O40]} (1), {Ag5(H2biim)2(Hbiim-NO2)2[PW12O40]} (2), {Ag7(pytz)4[PW12O40]} (3) (bpy=2,2′-bipyridine, H2biim=2,2′-biimidazole, pytz=4-(1H-tetrazol-5-yl)pyridine), have been synthesized under hydrothermal condition. Compound 1 shows a 3D supramolecular framework based on 0D moieties. Compound 2 exhibits an attractive 2D biologic screw axis. Compound 3 displays a 3D structure, which consists of Ag(I)···π interactions, π···π stacking and weak Ag···Ag interactions. It is noteworthy that nitration happens to compound 2 during the hydrothermal condition, which is quite rare. Through contrasting the antibacterial activities of gram negative and gram positive bacteria, we find compounds 1–3 have better antibacterial property in gram negative bacteria than gram positive bacteria. In addition, compounds 1–3 also exhibit efficiency of photocatalytic decomposition of organic dyes. Those compounds may be used as potential multifunctional materials in wastewater treatment, because they not only can kill bacteria but also degrade organic pollutants.

Syntheses, Structures and Catalytic Properties of Cobalt(II) and Silver(I) Coordination Polymers Based on Flexible Bis(2-methyl benzimidazole) and Dicarboxylic Acids

Two coordination polymers formulated as [Co2(2,6-ndc)2(L)]n (1) and [Ag(L)(1,4-Hndc)]n (2) (L = 1,1′-(1,4-butanediyl)bis(2-methylbenzimidazole), 2,6-H2ndc = 2,6-naphthalenedicarboxylic acid, 1,4-H2ndc = 1,4-naphthalenedicarboxylic acid) were synthesized under hydrothermal conditions and characterized by IR, elemental analysis, and single-crystal X-ray diffraction. The structural analysis reveals that complex 1 exhibits an unprecedented 3D framework with threefold interpenetrating xah topology. Complex 2 shows a 1D “Ω”-like chains bridged by L ligands, which is further extended via O–H···O hydrogen bonding interactions into a 2D (4,4) supramolecular layer. The thermal stability and catalytic properties of two complexes for the degradation of Congo red dye in a Fenton-like process was also investigated.

In vitro and in vivo anticancer effects of singly protonated dehydronorcantharidin silver coordination polymer in CT-26 murine colon carcinoma model.

Silver complexes are active constituents of the metal-based compounds; several studies suggest that silver complexes possess antimicrobial and anticancer properties. We have recently reported that Ag-SP-DNC, a novel silver and singly protonated dehydronorcantharidin complex, triggers oxidative stress-mediated apoptosis of lung cancer cells. In this study, we investigated the anticancer effects of Ag-SP-DNC in CT-26 murine colon carcinoma model. Ag-SP-DNC induced apoptosis of CT-26 cells, together with inhibition of cell proliferation; treatment of CT-26 tumor-bearing mice with Ag-SP-DNC delayed tumor growth. We also explored the mechanism of action of Ag-SP-DNC and found that Ag-SP-DNC treatment of CT-26 cells was associated with high levels of intracellular reactive oxygen species. The further experiments revealed that Ag-SP-DNC-treated cells underwent loss of mitochondrial membrane potential concomitant with intracellular calcium overload and caspase-3 activation. Taken together, our study demonstrates the potent anticancer effects of Ag-SP-DNC to colorectal cancer.

Structural modulation and properties of silver(I) coordination polymers from 2,6-naphthalenedicarboxylic acid and flexible N-donor linkers

Based on the N-donor auxiliary ligand effect, four new silver(I) coordination polymers derived from 2,6-naphthalenedicarboxylic acid (H2ndc), namely [Ag(L1)(ndc)0.5] n (1), [Ag(L2)(ndc)0.5] n (2), {[Ag(L3)(ndc)0.5]·0.5(H2ndc)} n (3), and [Ag(L4)(H2O)·Hndc] n (4) (L1 = 1,3-bis(thiabendazole)butane, L2 = 4,4′-bis(pyrazole-1-ylmethyl)-biphenyl, L3 = 1,4-bis(benzimidazole)butane, L4 = 4,4′-dipyridylamine), have been synthesized by solvothermal reactions. Complex 1 possesses a 1D infinite loop and chain, which is further extended into a 3D supramolecular framework by π–π stacking interactions. Complex 2 presents an unprecedented 3D (3,4)-connected lim (baa-e-3,4-Imma) topology with the Schlafli symbol of (4.102)2(42.104). Complex 3 exhibits a 2D three-connected hcb (Shubnikov hexagonal plane) network and the Schlafli symbol is (63). Complex 4 shows a 1D linear chain, which generates a 2D supramolecular layer via hydrogen bonding interactions. Solid-state properties of 1–4 have also been investigated, which display high thermal stability and intense fluorescent emission in solid state. Moreover, the complexes manifest excellent catalytic activities for the decomposition of Congo red azo dye by hydrogen peroxide in a Fenton-like process.

A bimodal 2D silver coordination polymer: Turn-on sensing of CdII and sensitization of lanthanide ions

The new transition metal coordination polymer, namely [Ag(Hcpna)]n (1) (H2cpna5-(4-carboxyphenyl) nicotinic acid) has been synthesized under hydrothermal conditions and characterized. Interestingly, when this compound was immersed in the different metal ion solutions, it shows highly selective sensing for Cd2+ based on significant luminescence enhancement. What's more, the compound 1 can serve as an antenna for sensitizing the visible-emitting of the lanthanide cations to exhibit their characteristic emissions in solution.