Ag Separation Research Articles

Di-, tri-, and tetranuclear silver(I) complexes of phenanthroline-functionalized NHC ligands

A few polynuclear silver(I)–NHC complexes have been synthesized via the reactions of phenanthroline-functionalized imidazolium salts with Ag2O at room temperature. The structures of di-, tri-, and tetranuclear silver complexes were fully characterized. The two N-phenanthrolinylimidazolylidene ligands in [Ag4(L1)4](PF6)4 (1), [Ag2(L2)2](PF6)2 (2), and [Ag2(L3)2](PF6)2 (3) are head-to-head arranged. Complex 1 contains a short ligand-unsupported Ag–Ag bond being 3.152(1) Å representing the first example of strictly linear Ag4 cluster stabilized by NHCs. Trinuclear [Ag3(L4)2](PF6)3 (4) of phenanthroline-bridged biscarbene ligands contains a linearly arranged Ag3 core. [Ag3(L5)2](PF6)3 (5) and [Ag3(L4)2](PF6)3 (7) are also trinulear Ag(I) complexes. Binuclear [Ag2(L6)2](PF6)2 (6) exhibits a twisted macrocyclic structure with the Ag–Ag separation at 3.162(1) Å. In 1–4, the silver ions are held together by two ligands in close proximity with the Ag–Ag distances between 2.810(1) and 2.922(1) Å. The fluorescent properties of these silver complexes have also been briefly studied.

Synthesis and characterization of plasmonic visible active Ag/ZnO photocatalyst

Ag deposited ZnO nanoparticles (NPs) have been synthesized by simple sol–gel method for visible light active photocatalytic application. X-ray diffraction (XRD), TEM, UV–DRS and PL studies have been used to characterize the photocatalyst. The results show that Ag/ZnO NPs are wurtzite phase (WZ) of ZnO with Ag NPs in the surface region forming a hetero-interface of Ag–WZ (ZnO). Visible light activity of the material has been studied using photocatalytic degradation kinetics of methylene blue as a probe pollutant. Ag/ZnO NPs exhibit five times higher visible-light driven photocatalytic activity than pristine ZnO and four times than the reference Degussa P-25, under identical conditions. The high visible activity of Ag/ZnO may be attributed to the surface plasmon effect complemented sensitization in the presence of metallic Ag and effective charge separation through Ag–WZ hetero-interfaces.

Two Ag(I) Complexes Constructed From the Flexible Tripodal Pyridyl-Benzimidazole-Based Connector

Two new complexes {Ag2(TPBT)(NO3)2}n (1) and Ag2(TPBT)4 (ClO4)2 (2) were constructed by the reaction of tripodal connector 1,3,5-[(2-pyridyl)-1H-benzoimidazol- 1-methyl)-2,4,6-trimethylbenzene (TPBT) and corresponding silver salts under solvothermal conditions. The synergistic effect of the flexible tripodal ligand and anions has led to different complexes 1 and 2. Complex 1 is a 2D layer with the binuclear units with the Ag···Ag distance of 2.9054 Å, whereas 2 is a binuclear motif with Ag···Ag separation of 10.526 Å. Both 1 and 2 are further extended into 3D supramolecular architectures by hydrogen bonds and π···π interactions, which exhibit weak luminescence emission in the solid state at room temperature. Supplementary material is available for this article. Go to the publisher's online edition of Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry to view the supplemental file.

Synthesis, crystal structures, in vitro anticancer, and in vivo acute oral toxicity studies of bis-imidazolium/benzimidazolium salts and respective dinuclear Ag(I)-N-heterocyclic carbene complexes

The synthesis, spectral (FT-IR and NMR), and structural studies of 1,1′-methylene linked 3,3′-2-cyanobenzyl bis-imidazolium salt (L1) and respective dinuclear Ag(I)-NHC complex (C1) are reported. The structures of both compounds were established through single-crystal X-ray diffraction. C1 has a short Ag–Ag separation of 3.16 Å. Both L1 and C1 were tested for potential against leukemia (k562) cell line. For comparison, para-xylyl linked bis-benzimidazolium salts (L2–L4) and their dinuclear Ag(I)-NHC complexes (C2–C4) were synthesized and tested against the same cell line (K562). The IC50 values proved that L2–L4 and C2–C4 are many fold more active than L1 and C1. The mechanism of action and structure activity relationship are discussed. In vivo oral acute toxicity study (sighting study) was carried out which depicts that 2000 mg/kg dose of selected compounds is an appropriate and safe dose for conducting main study on animals.

A New Photoluminescent and Antibacterial Polymeric Silver(I) Complex Generated from Pyridine-2,3-dicarboxylic Acid

A new two-dimensional polymeric [Ag2(μ-Hpydc)2(μ-pyz)]n (1) (H 2 pydc = pyridine-2,3-dicarboxylic acid, pyz = pyrazine), has been synthesized and characterized by elemental analysis, IR spectroscopy, thermal analysis and single crystal X-ray diffraction. X-ray diffraction analyses show that Hpydc exhibits novel coordination mode in 1, acts as a bridging ligand between two Ag(I) centers via deprotonated carboxylate μ-O1 atoms, forming binuclear [Ag2(μ-Hpydc)2] units (Ag···Ag separation is 2.9482(4) A). These units are connected to each other through pyz and Hpydc ligands, leading to two-dimensional polymeric structure. The coordination geometry around the silver(I) ions in the complex is a highly distorted square-pyramidal (τ = 0.229) with an AgN2O3 chromospheres. The solid state photoluminescence properties of 1 and H 2 pydc have been studied at room temperature. Furthermore, the complex has been tested for its in vitro antibacterial activity and is determined to be highly effective for antibacterial activity against Gram-positive and Gram-negative pathogenic bacteria cells. A new polymeric 2D silver(I) complex [Ag2(μ-Hpydc)2(μ-pyz)]n (1) (H 2 pydc = pyridine-2,3-dicarboxylic acid, pyz = pyrazine) has been synthesized and characterized by elemental analysis, IR spectroscopy, thermal analysis and single crystal X-ray diffraction. The solid state photoluminescence properties of 1 and H 2 pydc have been studied at room temperature and also it has been tested for its in vitro antibacterial activity.

Di-μ-thiosemicarbazide-κ4S:S-bis[chloridobis(triphenylphosphane-κP)silver(I)

The dinuclear title complex, [Ag2Cl2(CH5N3S)2(C18H15P)2], lies across an inversion center. The AgI ion exhibits a slightly distorted tetra­hedral coordination geometry formed by a P atom from a triphenyl­phosphane ligand, two metal-bridging S atoms from thio­semicabazide ligands and one chloride ion. The S atoms bridge two symmetry-related AgI ions, forming a strictly planar Ag2S2 core with an Ag⋯Ag separation of 2.7802 (7) Å. There is an intra­molecular N—H⋯Cl hydrogen bond. In the crystal, N—H⋯Cl and N—H⋯S hydrogen bonds link complex mol­ecules, forming layers parallel to (001). These layers are connected through π–π stacking inter­actions [centroid–centroid distance = 3.665 (2) Å], leading to the formation of a three-dimensional network.

Syntheses and Structures of Mononuclear, Dinuclear and Polynuclear Silver(I) Complexes of 2-Pyrazole-Substituted 1,10-Phenanthroline Ligands

A series of mononuclear, dinuclear and polynuclear silver(I) complexes (1–6) bearing 2-pyrazole-substituted 1,10-phenanthroline derivatives (L1, FL1, L2) have been synthesized and characterized by 1H and 13C NMR, IR spectroscopy, elemental analysis, and single crystal X-ray diffraction. Reaction of L1 (L1 = 2-(3,5-dimethylpyrazol-1-yl)-1,10-phenanthroline) with AgClO4 or AgBF4 afforded two dinuclear silver(I) complexes [Ag2(L1)2(CH3CN)2](ClO4)2 (1) and [Ag2(L1)2(CH3CN)2](BF4)2 (2), in which two [AgL1(CH3CN)]+ units are linked by Ag···Ag interaction (Ag···Ag separation: 3.208(2) and 3.248(1) Å, respectively). A one-dimensional polymer {[AgL1](BF4)}∞ (3) consisting of an infinite ···Ag···Ag···Ag··· chain (Ag···Ag separation: 3.059(1) Å), as well as a dinuclear complex [Ag2(ClO4)2(L1)2] (4) in which the perchlorate anions instead of solvents are involved in the metal coordination, have also been obtained. The mononuclear complex [Ag(FL1)2](BF4) (5) was synthesized from FL1 (FL1 = 2-(3,5-bis(trifluoromethyl)pyrazol-1-yl)-1,10-phenanthroline) and AgBF4, while the dinuclear [Ag2(BF4)2(L2)2] (6) was isolated from L2 (L2 = 2-[N-(3-methyl-5-phenylpyrazole)]-1,10-phenanthroline). The photoluminescence properties of the ligands and complexes 1–6 have been studied both in the solid state and in solution.

Bis(μ-4,6-dimethylpyrimidine-2-thiolato)-κ3N,S:S;κ3S:N,S-bis[(triphenylphosphane-κP)silver(I)

The dinuclear title complex, [Ag2(C6H7N2S)2(C18H15P)2], comprises two inversion-related [Ag(C6H7N2S)(C18H15P)] units. The pyrimidine­thiol­ate anion acts both as a bridging and a chelating ligand. The AgI ions are linked via two μ 2-S donor atoms, which generate a strictly planar Ag2S2 core with an Ag⋯Ag separation of 2.9569 (4) Å. The AgI ion presents a distorted tetra­hedral coordination geometry. In the crystal, weak C—H⋯N and C—H⋯S hydrogen bonds link the complex mol­ecules into a two-dimensional network parallel to (010).

Bis[μ-bis(diphenylphosphino)methane-1:2κ2P:P′]-bis(nitrito-κ2O,O′)]disilver(I) acetonitrile disolvate

The title complex, [Ag2(NO2)2(C25H22P2)2]·2CH3CN, is a centrosymmetric dimer in which two bis(diphenylphosphino)methane ligands bridge two Ag+ ions, forming an eight-membered ring with a short Ag⋯Ag separation of 3.1809 (5) Å. The distorted P2O2 coordination of the cation is completed by two O-donors from a symmetric bidentate chelate NO2 − anion [Ag—O = 2.550 (3) and 2.567 (3) Å].

Synthesis, crystal structures, spectroscopic and thermal properties of silver(I) saccharinate complexes with N-donor ligands

The synthesis, spectroscopic and thermal properties and X-ray structures of four silver(I) saccharinate complexes with N-donor ligands, [Ag(sac)(edmen)] (1), [Ag(sac)(teten)] (2), [Ag2(sac)2(o-bix)2] (3) and [Ag(sac)(dpa)] (4) (edmen=N-ethyl-N′,N′-dimethylethylenediamine, teten=N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine, o-bix=1,2-bis(imidazole-1-ylmethyl)benzene and dpa=2,2′-dipyridylamine) are described. In complex 1, the Ag(I) ion is coordinated by two N atoms from edmen and one N atom from sac ligand, forming a slightly distorted Y-shaped AgN3 arrangement. In complex 2, the Ag(I) is four coordinated by N-bonded sac and tridentate teten ligands, exhibiting a seesaw AgN3O geometry. A crystallographically independent Ag(I) ion in 3 is surrounded with a T-shaped geometry by two N atoms from o-bix ligand and one N atom from one sac ligand, and the Ag⋯Ag separation is 3.338Å. In complex 4, the Ag1 ion is coordinated by three nitrogen atoms from sac and dpa ligands to form a distorted Y-shaped geometry. The dpa ligand behaves as a bidentate ligand, forming a six-membered chelate ring, while the sac ligand is N-coordinated. The most striking feature of complexes 1 and 2 is the presence of both intra- and intermolecular C–H⋯Ag hydrogen-bonding interactions. Crystal packing of complexes is achieved by the hydrogen bonds, intra- and/or intermolecular C–H⋯π, weak π⋯π and Ag⋯π interactions to generate a three-dimensional supramolecular network. The photoluminescence spectrum shows that 4 displays a red-shift emission in the solid state at room temperature.

Poly[(μ4-5-bromopyridine-3-sulfonato)silver(I)

The silver(I) complex, [Ag(C5H3BrNO3S)]n, was obtained by reaction of AgNO3 and 5-bromopyridine-3-sulfonic acid. The AgI ion is coordinated by an O3N donor set in a slightly distorted tetra­hedral geometry. The AgI ions are linked by μ4-5-bromo­pyridine-3-sulfonate ligands, forming a layer parallel to (100). The layers are further connected via C—H⋯Br hydrogen-bonding inter­actions into a three-dimensional supra­molecular network. The Ag⋯Ag separation is 3.0159 (6) Å, indicating the presence of argentophilic inter­actions.

Argentophilic interactions in multinuclear Ag complexes of imidazole containing Schiff bases

The reactions of imidazole groups containing Schiff bases, 1,2-bis[(1-methyl-2-imidazolyl)-methyleneamino]ethane (bmimen) and 1,3-bis[(1-methyl-2-imidazolyl)-methyleneamino]propane (bmimpn), with silver salts AgCF3SO3 and AgClO3 were studied. Five new silver complexes, [Ag2(bmimen)2][CF3SO3]2·CH3OH·CH3CN (1), [Ag2(bmimen)2][CF3SO3]2 ·0.5H2O (2), [Ag2(bmimen)2][ClO3]2·CH3OH (3), [Ag3(bmimen)2(μ-CF3SO3)2]2[CF3SO3]4 (4) and [Ag(bmimpn)]n[CF3SO3]n (5), were synthesized and characterized. The Ag⋯Ag distances in compounds 1–5 depend on the length of the alkyl chain separating the imidazole ends of the ligand and the coordination mode of the bmimen and bmimpn. The shortest Ag⋯Ag distance of 2.7842(2) A was found in 4. Such a short distance indicates a strong argentophilic interaction. Argentophilic interactions exist in each of the dinuclear structures 1–3 (Ag⋯Ag distances are 3.3348(5), 3.1873(3) and 3.0680(2) A, respectively). The distance depends on crystal packing, which is determined by the counter ion and solvent molecules in the structure. In polymeric structure 5, the longer alkyl chain between the imidazole end units of the ligand pushes the metal centres further apart, the Ag⋯Ag separations being 3.6088(4) and 3.5279(4) A. The results show that imidazole-based Schiff bases can be used to build multinuclear Ag compounds with variable silver–silver interactions.

Crystal structures of two new dinuclear Ag(I) complexes constructed from 4,4′-biphenyldicarboxylic acid and N-containing ligands

The reaction of silver 4,4′-biphenyldicarboxylate with 1,3-diaminopropane (DAP) and 2-amino-5-methylpyridine (AMP) respectively results in the formation of two dinuclear silver(I) complexes: [Ag2(DAP)2](BPC)·2H2O (1) and [Ag2(BPC)(AMP)4]·2H2O (2), where BPC is 4,4′-biphenyldicarboxylate. The complexes are characterized by elemental analysis and X-ray crystallography. Complex 1 crystallizes in the triclinic system, P-1 space group, a = 8.585(2) A, b = 8.849(2) A, c = 9.890(3) A, α = 107.893(3)°, β = 94.139(3)°, γ = 113.202(3)°, V = 640.9(3) A3, Z = 1. Complex 2 crystallizes in the triclinic system, P-1 space group, a = 11.818(3) A, b = 13.132(4) A, c = 13.281(4) A, α = 92.571(4)°, β = 96.425(3)°, γ = 102.142(4)°, V = 1997.5(10) A3, Z = 2. Complex 1 consists of a macrocyclic dinuclear silver(I) dication, a 4,4′-biphenyldicarboxylate anion, and two water molecules of crystallization. Each Ag atom is in a linear coordination. Complex 2 consists of a dinuclear silver(I) complex molecule and two water molecules of crystallization. Each Ag atom is in a T-shaped coordination. The Ag...Ag separations are 5.127(2) A in 1 and 3.172(2) A in 2.

Poly[bis[μ-1,3-bis(diphenylphosphanyl)propane-κ2P:P′]-di-μ-thiocyanato-κ2S:N;κ2N:S-disilver(I)

In the title coordination polymer, [Ag2(NCS)2(C27H26P2)2]n, two centrosymmetrically related Ag+ cations are linked by two thio­cyanate anions into binuclear eight-membered macrocycles. The Ag⋯Ag separation within the macrocycle is 5.4400 (6) Å. The distorted tetra­hedral coordination about each metal atom is completed by the P atoms of two bridging 1,3-bis­(diphenyl­phosphan­yl)propane ligands, forming polymeric ribbons parallel to the a axis.

Catena-Poly[[silver(I)-μ-bis{2-[(E)-phenyldiazenyl]-1H-imidazol-1-yl}methane] trifluoromethanesulfonate

The title compound, {[Ag(C19H16N8)](CF3SO3)}n, is a coordin­ation polymer with cationic chain motif. The Ag+ cation is coordinated by two unsubstituted imidazolyl N atoms of two independent 2-paBIM ligands [2-paBIM is bis­{2-[(E)-phenyl­diazen­yl]-1H-imidazol-1-yl}methane]. The shortest Ag⋯Ag separation in a cationic chain is 8.841 (2) Å and the dihedral angle between two 2-phenyl­diazenyl-imidazole planes in the same ligand is 74.7 (3)°. Weak C—H⋯O interactions are seen in the crystal.

Synthesis, characterization, and antibacterial activity of two silver(I) compounds with 4-dimethylaminopyridine

Two new silver(I) compounds, [Ag(4-dmapy)2(p-bromophenylacetate)] · H2O (1) and [Ag(4-dmapy)2(p-hydroxyphenylacetate)]·2H2O (2) (4-dmapy = 4-dimethylaminopyridine), have been synthesized and characterized. X-ray crystallographic analysis reveals that 1 and 2 contain a linear Ag(4-dmapy)2 chromophore, which further forms dimeric silver(I) units via weak silver–silver interaction. The short Ag ··· Ag separations in 1 and 2 are 3.0395(12) and 3.2697(10) Å, respectively. Compounds 1 and 2 have good anti-Bacillus subtilis activity in vitro (minimum inhibitory concentration, MIC = 12.5 µg mL−1) but were inactive against Staphylococcus aureus and Escherichia coli (MIC > 50 µg mL−1).

Catena-Poly[bis(μ3-2-methylbenzoato)disilver(I)

The crystal structure of the title compound, [Ag2(C8H7O2)2]n, features polymeric chains extending along the a axis, with the two Ag+ cations in a distorted trigonal coordination. The range of Ag—O bond lengths is 2.169 (2)–2.433 (2) Å, whereas the Ag⋯Ag separations are in the range 2.8674 (4)–3.6256 (5) Å. The 2-methyl­benzoate groups are oriented at a dihedral angle of 60.7 (1)° with respect to each other.

Crystal structure of a silver(I) complex {[Ag(N-methylthiourea)2]NO3} n exhibiting infinite chains of AgS4 tetrahedra

A polymeric silver(I) complex, bis(N-methylthiourea)silver(I) nitrate, {[Ag(Metu)2]NO3} n is prepared and its crystal structure is determined. The compound crystallizes in the monoclinic C2/c space group. In the structure, distorted AgS4 tetrahedra are linked through the sulfur atoms of the Metu ligand to form isolated infinite chains of the type [Ag(SR)2] n n+ . The cationic chains are separated from each other by nitrate ions that do not coordinate to the metal ion. The chains are bridged via N-H...O hydrogen bonds involving the nitrate ions. The complex exhibits an Ag—Ag separation of ∼3.21 A indicating the existence of significant argentophilic interactions. An upfield shift in the >C=S resonance of Metu in 13C NMR and downfield shift in the N-H resonance in 1H NMR are consistent with sulfur coordination to silver(I).

Homo- and heterochiral coordination polymers of silver with diaminocyclohexane as bridging ligand: Trends in alkylbenzoates

Reaction of Ag 2CO 3 with four methyl-substituted derivatives of benzoic acid afforded silver benzoates; no additional anions are involved in these solids. One of the silver carboxylates was studied by X-ray diffraction: in the crystal, silver 3,5-dimethylbenzoate monohydrate consists of carboxylato-bridged discrete dinuclear molecules with a short Ag⋯Ag separation of 2.7719(5) Å and one weakly bonded hydrate water molecule per cation. The binary silver carboxylates were combined with either racemic or enantiopure trans-1,2-diaminocyclohexane and resulted in four homochiral and four heterochiral crystalline solids. All eight structures feature cationic chain polymers, carboxylate anions and hydrate water. In three of the solids derived from the racemic ligand, the individual cationic chains are homochiral. In all structures, the primary coordination of the Ag(I) centers by nitrogen is essentially linear. Despite the chemical similarity in the anions, the backbone of the polymers proved to be conformationally soft with variable Ag–N–C–C torsion angles. In the resulting structures, the diamine ligand may bridge two cations in a wide distance range between ca. 3.0 and ca. 7.2 Å. Both the chirality of the trans-1,2-diaminocyclohexane ligand and the substitution pattern of the benzoate anion have strong impact on the nature of secondary interactions perpendicular to the polymer strands: either weak coordination by carboxylato or hydrate water oxygen atoms or argentophilic interactions are encountered. The Ag⋯Ag contacts increase the dimensionality of the solids from chain polymers to layer structures.

Poly[(μ(2)-4,4'-bipyridine)(μ(2)-3,5-dicarboxybenzenesulfonato)silver(I)

In the title compound, [Ag(C8H5O7S)(C10H8N2)]n, the Ag atom is tetra­coordinated by two 4,4′-bipydidine (4,4′-bipy) N atoms and two monodentate sulfonate O atoms of the 5-sulfoisophthalic acid (H3 sip) ligands. Adjacent Ag atoms are bonded through four sulfonate O atoms, forming a dinuclear unit with an Ag⋯Ag separation of 3.384 (5) Å; they are further linked together by the 4,4′-bipy lignds into a chain. Classical inter­molecular O—H⋯O and non-classical intra­molecular C—H⋯O hydrogen bonds are also observed in the two-dimensional supra­molecuar structure.