Synthesis and Structural Analysis of a Helical Coordination Polymer Formed by the Self-Assembly of a 2,2′-Bipyridine-Based exo-Ditopic Macrocyclic Ligand and Silver Cations

The overall topology of coordination polymers can be controlled by means of the coordination preferences of the metal center and the structure of the bridging ligand. This is demonstrated here by the synthesis of a single-stranded helical coordination polymer by the self-assembly of the exo-ditopic ligand 1 and silver ions.     

Anion control of the self-assembly of 2,3-diarylpyrazines with silver(I) salts

The synthesis and characterization of three one-dimensional coordination polymers formed on self-assembly of 2,3-diarylpyrazines with silver(I) salts are presented. A linear double-stranded coordination polymer was formed on self-assembly of 2,3-bis(3'5'-dimethylphenyl)pyrazine with silver(I) tetrafluoroborate. An essentially linear double-strand coordination polymer was formed on self-assembly of 2,3-bis(3'5'-dimethylphenyl)pyrazine with silver(I) trifluoromethanesulfonate. In contrast a helical silver-pyrazine coordination polymer with extensive intrastrand pi-stacking was formed on self-assembly of 2,3-diphenylpyrazine with silver(I) trifluoroacetate.     

Chiral Heterocyclic Ligands. XI. Self-assembly and X-ray Crystal Structures of Chiral Silver Coordination Polymers of (S)-(–)-Nicotine

Three chiral coordination polymers have been prepared by reaction of (S)-(–)-nicotine with silver(I) salts. X-Ray crystal structure determinations revealed that these all contain polymer chains in which the nicotine molecule acts as a bridging ligand between four-coordinate silver atoms. In one case additional bridging by nitrate anions leads to a three-dimensional network structure.     

Helical (isotactic) and syndiotactic silver(I) metallo-supramolecular coordination polymers assembled from a readily prepared bis-pyridylimine ligand containing a 1,5-naphthalene spacer

A ligand in which two pyridylimine binding units are linked by a 1,5-naphthalene spacer is prepared and its silver(I) coordination chemistry investigated. In the solid state, a pair of C-H triplebond N interactions between pyridylimine units link the free ligands into chain structures, with further C-H triplebond N and some -stacking interactions linking these chains into a three-dimensional structure. The spacer constrains the ligand to dinucleate, and with silver(I) the metal coordinates to two pyridylimine units from two separate ligands and this leads to the formation of coordination polymers with a range of different anions. Different twisting motifs within the ligand control the tacticity of these coordination polymers and both isotactic, helical polymers and syndiotactic (achiral) polymers result. The core of the isotactic polymer strands contains two metallo-vectors and results in long-range ordering of the metal centres into a 2 x n grid arrangement. The solution behaviour indicates that exchange between the diastereomeric forms occurs. Since this must involve inversion at the metal centres, atactic species may also form a component of the solution library.     

Novel silver(I)-organic coordination polymers: conversion of extended structures in the solid state as driven by argentophilic interactions

Structurally distinct coordination polymers [Ag(bpp)]ClO4 1 and [Ag(bpp)]PF6 2 [bpp = 1,3-bis(4-pyridyl)propane] have been assembled; the conversion of 1 into 2 on treatment with NaPF6 is driven by argentophilic interactions and is the first such transformation reported for silver(I)-organic coordination polymers.     

A Robust Microfluidic Device for the Synthesis and Crystal Growth of Organometallic Polymers with Highly Organized Structures

A simple and robust microfluidic device was developed to synthesize organometallic polymers with highly organized structures. The device is compatible with organic solvents. Reactants are loaded into pairs of reservoirs connected by a 15 cm long microchannel prefilled with solvents, thus allowing long‐term counter diffusion for self‐assembly of organometallic polymers. The process can be monitored, and the resulting crystalline polymers are harvested without damage. The device was used to synthesize three insoluble silver acetylides as single crystals of X‐ray diffraction quality. Importantly, for the first time, the single‐crystal structure of silver phenylacetylide was determined. The reported approach may have wide applications, such as crystallization of membrane proteins, synthesis and crystal growth of organic, inorganic, and polymeric coordination compounds, whose single crystals cannot be obtained using traditional methods.     

Tube-type coordination polymers: two- and four-silver(I)-mediated linear networking of calix[4]arene tetracarboxylates

Two calix[4]arene tetracarboxylates, [calix[4]arene tetraacetate (K(4)CTA) and calix[4]arene tetrabenzoate (K(4)CTB)] as their potassium salts, have been prepared. Employing these as precursors, two Ag(I) coordination polymers incorporating calix[4]arene units have been successfully prepared and their X-ray crystal structures have been determined. In these, the CTA and CTB derivatives are linearly bound to two and four silver atoms, respectively, to generate unusual tubular nanostructures. A comparative NMR study was undertaken to investigate the nature of the metal ion blocking of the tube as observed in the CTA-derived structure. The thermal properties for both coordination polymers were also examined.     

Impact of ionic liquids on silver thermoplastic polyurethane composite membranes for propane/propylene separation

This work describes newly synthesized composite polymeric membranes and their utilization in propane/propylene separation in a gas mixture. The nonporous composite polymers were successfully synthesized by using thermoplastic polyurethane (TPU) and several silver salts/silver salts with ionic liquids (ILs). Our studies showed that silver bis(trifluoromethanesulfonyl)imide (Ag[Tf₂N]) containing membranes outperformed other silver salt containing membranes in terms of selectivity. In addition, to this finding, ILs, as additives for the membranes, enhanced the selectivity by facilitating improved coordination of the olefin with the silver ions in the dense composite polymers.     

Direction of topological isomers of silver(I) coordination polymers induced by solvent, and selective anion-exchange of a class of PtS-type host frameworks

The construction of two types of coordination polymers with closely related 4-connected topologies [PtS and lvt (4(2).8(4))] were achieved based on a well-designed bent dipyrazine linker, and the topological differences only result from the stereochemistry of silver(I) coordination sphere with the same coordination donors. Selective anion-exchange functions of the series of PtS-type coordination networks containing different counter anions (from small BF4- to very large SbF6-) were identified.     

Coordination polymers from silver(I) and bifunctional pyridyl ligands

Coordination polymers and a macrocycle formed from the reactions between flexible bis(2-pyridyl) ligands and AgCF(3)SO(3) are reported. The type of structure formed depends on the choice of ligand and the stoichiometry of the reaction. When 1 equiv of 1,4-bis(pyridin-2-ylmethoxy)benzene (L2), 4,4'-bis(pyridin-2-ylmethoxy)biphenyl (L4), or bis((4-pyridin-2-ylmethoxy)phenyl)methane (L5) is used, 1D chain coordination polymers held together via Ag-N bonds are generated. When a 2:1 ratio of L2 and silver ion is used, a 2D porous network is formed. The reaction between silver ions with a mixture of ligands (L1 and L2 in 1:1 ratio, L1 = 1,4-bis((pyridin-2-yl-methyl)thio)benzene) results in a novel 1D ABAB type coordination copolymer where L1 and L2 act as a bis-bidentate and a bis-monodentate ligand, respectively. The reaction of 1-(pyridin-2-ylmethoxy)-4-((pyridin-2-yl-methyl)thio)benzene (L3) with silver ions in a 1:1 ratio gives a bimetallic macrocycle rather than a polymeric species. Structural analyses of the polymeric compounds suggest that interactions between the aromatic rings play a significant role in stabilizing the polymeric structures.     

Solution state coordination polymers featuring wormlike macroscopic structures and cage-polymer interconversions

In the absence of coordinating solvents and anions, silver salts and triphosphines form viscous, thixotropic coordination polymers in solution, which aggregate into unusual wormlike macroscopic structures and undergo cage-polymer interconversions depending on the stoichiometry and presence of templating anions.     

Metallogels Derived from Silver Coordination Polymers of C3‐Symmetric Tris(pyridylamide) Tripodal Ligands: Synthesis of Ag Nanoparticles and Catalysis

By applying a recently developed crystal engineering rationale, four C₃ symmetric tris(pyridylamide) ligands namely 1,3,5‐tris(nicotinamidomethyl)‐2,4,6‐triethylbenzene, 1,3,5‐tris(isonicotinamidomethyl)‐2,4,6‐triethylbenzene, 1,3,5‐tris(nicotinamidomethyl)‐2,4,6‐trimethylbenzene, and 1,3,5‐tris(isonicotinamidomethyl)‐2,4,6‐trimethylbenzene, which contain potential hydrogen‐bonding sites, were designed and synthesized for generating Ag^I coordination polymers and coordination‐polymer‐based gels. The coordination polymers thus obtained were characterized by single‐crystal X‐ray diffraction. The silver metallogels were characterized by transmission electron microscopy (TEM) and dynamic rheology. Upon exposure to visible light, these silver metallogels produced silver nanoparticles (AgNPs), which were characterized by TEM, powder X‐ray diffraction, energy dispersive X‐ray and X‐ray photoelectron spectroscopy. These NPs were found to be effectively catalyzed the reduction of 4‐nitrophenolate to 4‐aminophenolate without the use of any exogenous reducing agent.     

Photoluminescent supramolecular networks from metal-mediated assembly of polythia conjugated dieneyne

Polythia conjugated dieneyne 1,1,2,5,6,6-hexakis(phenylthio)-1,5-diene-3-yne and its one- and two-dimensional silver(I) coordination polymers, which exhibited fluorescence and redox properties, were prepared and investigated.     

Chiral heterocyclic ligands. XIV. Control of directionality in silver coordination polymers through ligand design

Four C(2)-symmetric homochiral ligands derived from (+)-camphor are shown to produce linear chain and ladder silver coordination polymers wherein the directionality and polarisation can be controlled by subtle differences in ligand design.     

Benzenepolycarboxylate-templated assembly of silver coordination polymers exhibiting argentophilic honeycomb layer and tubular motifs

Organic anion template-controlled reactions of benzenepolycarboxylic acids with silver(I) salts resulted in two coordination polymers with distinct structural features based on the argentophilic interaction, one exhibiting a honeycomb layer formed by the fusion of macrocyclic Ag(16) rings and the other furnishing the first example of a Ag(∞) tubular motif.     

Silver(I) Complexes of Two Flexible Bis-phospholane Ligands: Metallamacrocycles,Polymeric Chains,and Metallacryptands

In a 2:2 reaction with silver(I) chloride or bromide, 1,5-bis(1-phospholano)pentane ( 1a ) afforded frame-like macrocyclic structures, with intra- ( 2 , Cl) or intermolecular ( 3 , Br) halido bridges. In contrast, 1,7-bis(1-phospholano)heptane ( 1b ) formed coordination polymers 4a (Cl) and 4b (Br) with bridging bis-phospholane and halido ligands. A unique paddle wheel-type metallacryptand structure 5 was obtained from 1a and silver(I) bromide in a 2:3 reaction (M:L). All complexes were fully characterized by NMR, IR spectroscopy, mass spectrometry, and X-ray crystallography.     

Heterometallic architectures based on the combination of heteroleptic copper and cobalt complexes with silver salts

A strategy for the formation of heterometallic coordination polymers based on novel copper(II) and cobalt(III) heteroleptic complexes (acacCN)Cu(dpm) and (acacCN)Co(dpm)(2) (acacCN = 3-cyanoacetylacetonate; dpm = dipyrrin) is presented. Using dipyrrins appended with a p- or m-pyridyl group, dpm-4py and dpm-3py, four novel copper and cobalt complexes were prepared and characterized both in solution and in the solid state. These two classes of complexes show different electrochemical properties upon investigation by cyclic voltammetry in CH(2)Cl(2). While the copper complexes show only irreversible reduction processes, the voltammogram of the cobalt species reveals the presence of two quasi-reversible reductions. In the solid state, the copper(II) compounds self-assemble to form one-dimensional architectures upon coordination of the peripheral pyridyl group to the copper center, as characterized by single-crystal X-ray diffraction. Owing to the filled coordination sphere of the octahedral cobalt centers, the (acacCN)Co(dpm-py)(2) compounds crystallize as isolated molecules. Upon reaction with silver salts, these complexes form crystalline heterometallic architectures with different organization and dimensionality, depending on the nature of the metal center and the position of the nitrogen atom in the pyridyl group. The two copper complexes lead to the formation of trinuclear species, {[(acacCN)Cu(dpm-py)](2)Ag}(+), resulting from coordination of the pyridyl groups to the silver cations. However, while meta-functionalized complexes self-assemble into an extended architecture via weak interaction of the peripheral nitrile of the acacCN ligand to the Ag(+) cation, this interaction is not present in the para-functionalized analogue. In both networks based on the Ag(BF(4)) salt, coordination of the tetrafluoroborate anion to the silver center in the rather rare chelate mode is observed. Upon assembly of the cobalt metallatectons with silver salts, two-dimensional (2D) coordination polymers are obtained in crystalline form, resulting, however, from different sets of interactions. Indeed, no coordination of the peripheral nitrile of the acacCN ligand is observed in the network incorporating the m-pyridyl-appended dpm; coordination of the pyridyl groups to the silver center and d(10)-d(10) interactions lead to a 2D architecture. In the case of the para analogue, a 2D honeycomb network is observed owing to coordination of the Ag(I) ion to two pyridyl nitrogen atoms and to one peripheral nitrile group of a acacCN ligand. This latter polymer represents a geometrical hybrid of the networks reported in the literature based on homoleptic Co(dpm-4py)(3) and Cr(acacCN)(3) complexes.     

Silver coordination compounds with antimicrobial properties

Silver and its compounds have long been known to possess antimicrobial properties. We report here on our observations in this field of research, namely on silver coordination compounds, and in particular polymers, which can be used in the medical field. An overview of the structural diversity of coordination compounds with a particular class of organic ligands is given, together with their properties, with a special focus on antimicrobial activity, solubility and light stability. Copyright © 2013 John Wiley & Sons, Ltd.     

Coordination polymers of silver(I) with bis(N-heterocyclic carbene): Structural characterization and carbene transfer

Reactions of the ethylene- and methylene-bridged bis(imidazolium) salts with an equivalent amount of silver oxide in dichloromethane at room temperature produced readily the silver NHC compounds [Ag₂LBr₂]. These compounds are partially soluble in DMF. The X-ray structure determination on 3d (L = 1,1′-dibenzyl-3,3′-ethylenediimidazolin-2,2′-diylidene) reveals the formation of bromide bibridged (Ag₂LBr₂)_n chains and a unique supramolecular motif with weak Ag?Ag interactions of 3.429 Å. Similar to monomeric silver(I) NHC complexes, the silver coordination polymers can also act as carbene transfer reagents for the formation of chelating palladium NHC complexes in excellent yields.     

Preferential deposition of cyanometallate coordination polymer nanoplates through evaporation of droplets

We reported a room-temperature method to deposit self-adhesive coordination polymers nanoplates on glass slides preferentially.