New Ag(I)-Containing Coordination Polymers Generated from Multidentate Schiff-Base Ligands

On the supramolecular properties of neutral, anionic and cationic cadmium complexes harvested from dithiolate–polyamine binary ligand systems

Three Cd(ii) complexes [Cd(i-mnt)(DMSO)₂]_n (1), {[Cd(i-mnt)pn]·2H₂O} (2), and [Cd(i-mnt)₃][Cd(tren)₂]₂ (3) harvested from 1,1-dicyanoethylene-2,2-dithiolate (i-mnt²⁻) and polyamine ligand systems have been designed, synthesized and structurally characterized.

Role of Pyridine Nitrogen in Palladium-Catalyzed Imine Hydrolysis: A Case Study of (E)-1-(3-bromothiophen-2-yl)-N-(4-methylpyridin-2-yl)methanimine

In the present study, 4-methylpyridin-2-amine was reacted with 3-bromothiophene-2-carbaldehyde and the Schiff base (E)-1-(3-bromothiophen-2-yl)-N-(4-methylpyridin-2-yl)methanimine was obtained in a 79% yield. Coupling of the Schiff base with aryl/het-aryl boronic acids under Suzuki coupling reaction conditions, using Pd(PPh₃)₄ as catalyst, yielded products with the hydrolysis of the imine linkages (5a–5k, 6a–6h) in good to moderate yields. To gain mechanistic insight into the transition metal-catalyzed hydrolysis of the compounds, density functional theory (DFT) calculations were performed. The theoretical calculations strongly supported the experiment and provided an insight into the transition metal-catalyzed hydrolysis of imines.

Marigold Flower-Like Assemblies of Phosphorescent Iridium-Silver Coordination Polymers

Racemic and enantiopure phosphorescent iridium(III)-silver(I) coordination polymers are reported. The polymers rac-, Λ-, and Δ-IrAg were formed, respectively, by the assembly of the chiral iridium metalloligands rac-, Λ-, and Δ-[Ir(mesppy)₂ (qpy)]PF₆ (rac-, Λ- and Δ-Ir) where mesppy is 2-phenyl-4-mesitylpyridinato and qpy is 4,4':2',2'':4'',4'''-quaterpyridine, and Ag⁺ ions through N_py -Ag linear coordination. The polymers have been characterized in MeNO₂ solution by ¹ H and ¹ H DOSY NMR and CD spectroscopies and in the solid-state by scanning electron microscopy (SEM). The crystal structures of the racemic polymer rac-IrAg has been obtained by X-ray diffraction. The polymers rac-, Λ-, and Δ-IrAg exhibited orange/red emission in solution, in films and as crystals, with intensities comparable to those of the corresponding iridium metalloligands rac-, Λ-, and Δ-Ir. The morphology of the enantiopure polymers in the solid-state resembles marigold flower-like nano-porous assemblies while the racemic polymer possesses an irregular morphology formation.

Four Mixed-Ligand Zn(II) Three-Dimensional Metal-Organic Frameworks: Synthesis, Structural Diversity, and Photoluminescent Property

Assemblies of four three-dimensional (3D) mixed-ligand coordination polymers (CPs) having formulas, {[Zn₂(bdc)₂(4-bpdh)]·C₂H₅OH·2H₂O}_n (1), [Zn(bdc)(4-bpdh)]_n (2), {[Zn₂(bdc)₂(4-bpdh)₂]·(4-bpdh)}_n (3), and {[Zn(bdc)(4-bpdh)]·C₂H₅OH}_n (4) (bdc²⁻ = dianion of 1,4-benzenedicarboxylic acid, 4-bpdh = 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene) have been synthesized and structurally characterized by single-crystal X-ray diffraction method. Structural determination reveals that the coordination numbers (geometry) of Zn(II) ions in 1, 2, 3, and 4 are five (distorted square-pyramidal (SP)), six (distorted octahedral (O_h)), five (trigonal-bipyramidal (TBP)), and four (tetrahedral (T_d)), respectively, and are bridged by 4-bpdh with bis-monodentate coordination mode and bdc²⁻ ligands with bis-bidentate in 1, chelating/bidentate in 2, bis-monodentate and bis-bidentate in 3, and bis-monodentate in 4, to generate two-fold interpenetrating 3D cube-like metal-organic framework (MOF) with pcu topology, non-interpenetrating 3D MOF, two-fold interpenetrating 3D rectangular-box-like MOF with pcu topology and five-fold interpenetrating diamondoid-like MOF with dia topology, respectively. These different intriguing architectures indicate that the coordination numbers and geometries of Zn(II) ions, coordination modes of bdc²⁻ ligand, and guest molecules play important roles in the construction of MOFs and the formation of the structural topologies and interpenetrations. Thermal stabilities, and photoluminescence study of 1–4 were also studied in detail. The complexes exhibit ligands based photoluminescence properties at room temperature.

Mononuclear and three-dimensional metal complexes based on a multidentate hydrazone ligand

A potentially pentadentate hydrazone ligand,N′-[1-(pyrazin-2-yl)ethylidene]nicotinohydrazide (HL), was prepared from the condensation reaction of nicotinohydrazide and acetylpyrazine. Reactions of HLwith MnCl2, Mn(CH3COO)2and Cd(CH3COO)2afforded three metal complexes, namely dichlorido{N′-[1-(pyrazin-2-yl-κN1)ethylidene]nicotinohydrazide-κ2N′,O}manganese(II), [MnCl2(C12H11N5O)], (I), bis{N′-[1-(pyrazin-2-yl-κN1)ethylidene]nicotinohydrazidato-κ2N′,O]manganese(II), [Mn(C12H10N5O)2], (II), and poly[[(acetato-κ2O,O′){μ3-N′-[1-(pyrazin-2-yl-κ2N1:N4)ethylidene]nicotinohydrazidato-κ3N′,O:N1}cadmium(II)] chloroform disolvate], {[Cd(C12H10N5O)(CH3COO)]·2CHCl3}n, (III), respectively. Complex (I) has a mononuclear structure, the MnIIcentre adopting a distorted square-pyramidal coordination. Complex (II) also has a mononuclear structure, with the MnIIcentre occupying a special position (C2symmetry) and adopting a distorted octahedral coordination environment, which is defined by two O atoms and four N atoms from twoN′-[1-(pyrazin-2-yl)ethylidene]nicotinohydrazidate (L−) ligands relatedviaa crystallographic twofold axis. Complex (III) features a unique three-dimensional network with rectangular channels, and theL−ligand also serves as a counter-anion. The coordination geometry of the CdIIcentre is pentagonal bipyramidal. This study demonstrates that HL, which can act as either a neutral or a mono-anionic ligand, is useful in the construction of interesting metal–organic compounds.

A nanoporous Ag(i)-MOF showing unique selective adsorption of benzene among its organic analogues

A 3D porous Ag(i)-MOF which is able to reversibly absorb and separate benzene from its six-membered cyclic organic analogues is reported.

Metal‐Containing Polymers

The article provides an overview of the synthesis, properties, and applications of metal‐containing polymers. The past decade has shown an exponential increase in synthetic methods, resulting in metal‐containing polymers, their characterization techniques, and their potential application into a variety of fields, including chemistry, medicine, biotechnology, and more.

C-Methylcalix[4]resorcinarene–1,4-bis(pyridin-3-yl)-2,3-diaza-1,3-butadiene (1/2)

In the title compound, 2C₁₂H₁₀N₄·C₃₂H₃₂O₈, the calixarene adopts a rctt conformation with dihedral angles of 138.40 (1) and 9.10 (1)° between the opposite rings. The dihedral angles between the rings of the pyridine derivative are 8.80 (1) and 9.20 (1)°. In the crystal, adjacent C-methylcalix[4]resorcinarene molecules are connected into columns parallel to [010] by O—H⋯O hydrogen bonds. O—H⋯N hydrogen bonds between the axial phenoxyl groups and bipyridine molecules link the columns into sheets parallel to (011), which are connected by O—H⋯N hydrogen bonds. Further O—H⋯N hydrogen bonds link the bipyridine and C-methylcalix[4]resorcinarene molecules, giving rise to a three-dimensional network.

Aqua-bis[N'-(2-hydroxy-benzyl-idene)isonicotinohydrazide-κN]silver(I) nitrate

In the title compound, [Ag(C₁₃H₁₁N₃O₂)₂(H₂O)]NO₃, two N atoms from two pyridine rings of two N′-(2-hydroxy­benzyl­idene)isonicotinohydrazide ligands coordinate to the Ag^I atom, forming a nearly linear geometry with an N—Ag—N angle of 171.63 (6)°; a water O atom is located at the apical site, completing the T-shaped coordination. The crystal structure is stabilized by extensive O—H⋯O, O—H⋯N and N—H⋯O hydrogen bonding.

Bis[N'-(3-cyano-benzyl-idene)isonicotino-hydrazide-κN]silver(I) trifluoro-methane-sulfonate

In the title compound, [Ag(C(14)H(10)N(4)O)(2)]CF(3)SO(3), two N atoms from two independent pyridyl rings of two N'-3-cyano-benzyl-ideneisonicotinohydrazide ligands coordinate to the unique Ag(I) ion, forming a nearly linear coordination geometry. Adjacent silver complexes are primarily linked together by Ag⋯N inter-actions, with Ag⋯N separations of 2.877 (2) and 3.314 (2) Å. On the other hand, one CF(3)SO(3) (-) anion inter-acts with hydrazone groups of two neighbouring ligands via N-H⋯O hydrogen bonds. These weak inter-molecular inter-actions contribute to the formation of supra-molecular chains. In addition, there are Ag⋯O inter-actions [2.787 (2) Å] between Ag and O atoms from adjacent chains.

Bis[N'-(3-cyano-benzyl-idene)isonicotino-hydrazide]silver(I) trifluoro-acetate

In the title compound, [Ag(C₁₄H₁₀N₄O)₂]CF₃CO₂, the Ag^I ion is coordinated by two N atoms of the pyridine rings of two N′-(3-cyano­benzyl­idene)isonicotinohydrazide ligands in a nearly linear geometry. In the crystal structure, a combination of close contacts formed via Ag⋯N inter­actions [Ag⋯N = 3.098 (2) and 3.261 (2) Å] from symmetry-related mol­ecules and inter­molecular N—H⋯O hydrogen bonds between CF₃CO₂⁻ anions and the hydrazone groups of two ligands give rise to chains. Furthermore, there are Ag⋯O inter­actions with a separation of 2.765 (2) Å between chains. The F atoms of the CF₃CO₂⁻ anion are disordered over two sites with refined occupancies of 0.593 (5) and 0.407 (5).

catena-Poly[[[[N'-(4-cyano-benzyl-idene)nicotinohydrazide]silver(I)]-μ-[N'-4-cyano-benzyl-idene)nicotinohydrazide]] hexa-fluoridoarsenate]

In the title compound, {[Ag(C₁₄H₁₀N₄O)₂]AsF₆}_n, the Ag^I ion is coordinated by two N atoms from two different pyridyl rings and one N atom from one carbonitrile group of three different N′-(4-cyano­benzyl­idene)nicotinohydrazide ligands in a distorted T-shaped geometry. The Ag—N_carbonitrile bond distance is significant longer than those of Ag—N_pyrid­yl. The bond angles around the Ag^I atom are also not in line with those in an ideal T-shaped geometry. One type of ligand acts as the bridge that connects Ag^I atoms into chains along [01]. These chains are linked to each other via N—H⋯O hydrogen bonds and Ag⋯O inter­actions with an Ag⋯O separation of 2.869 (2) Å. In addition, the [AsF₆]⁻ counter-anions are linked to the hydrazone groups through N—H⋯F hydrogen bonds. Four of the F atoms of the [AsF₆]⁻ anion are disordered over two sets of sites with occupancies of 0.732 (9) and 0.268 (9).

catena-Poly[[[N'-(4-cyano-benzyl-idene)nicotinohydrazide)silver(I)]-μ-N'-(4-cyano-benzyl-idene)nicotinohydrazide] hexa-fluorido-phosphate]

In the title polymer, {[Ag(C₁₄H₁₀N₄O)₂]PF₆}_n, each Ag^I ion is coordinated by two N atoms from two pyridyl rings of independent N′-(4-cyano­benzyl­idene)nicotinohydrazide ligands, and one N atom from one carbonitrile group of a symmetry-related ligand in a distorted T-shaped geometry. The ligands exhibit two modes of coordination. One acts as a bridge connecting Ag atoms to form one-dimensional chains along [01]. The other acts as a terminal monodentate ligand, coordinating to Ag through its pyridyl N atom. Two neighbouring anti­parallel chains in the crystal are connected through N—H⋯O hydrogen bonds. Other adjacent chains are packed via Ag⋯O inter­actions, with Ag⋯O separations of 2.876 (2) Å. In addition, PF₆⁻ counter-anions inter­act with the hydrazone groups through N—H⋯F hydrogen bonds. The PF₆⁻ anion is disordered over two sites, with occupancies of 0.773 (8) and 0.227 (8).

Four zinc(II) helical coordination polymers and 78-membered six-node zinc metallacycle assembled from diastereopure N,N'-bis(acetylacetone)cyclohexanediimine

The interaction of the diastereopure N,N'-bis(acetylacetone)cyclohexanediimine ligands, L(1)(1R,2R), L(2)(1S,2S), and their 1:1 mixture, with Zn(II) chloride has been investigated. Four new coordination polymers, [ZnL(1)Cl2 x H2O]n (1), [ZnL(2)Cl2 x H2O]n (2), [ZnL(2)Cl2]n (3), and [Zn6(L(2))6Cl12 x 2 H2O]n (4), each consisting of an infinite single helical chain displaying different pitches and/or handedness have been isolated. The complexed Schiff base ligands are present in their deprotonated enol forms, and the nitrogen atoms, which do not coordinate, are protonated because of proton transfer from the adjacent enol oxygen (coupled with concomitant N-H...O bond formation); each bound ligand is thus pseudo-zwitterionic. The respective zinc centers are bound to two chloro ligands and two oxygen donors from acacH-imine units belonging to different N,N'-bis(acetylacetone)cyclohexanediimine ligands such that the coordination at each zinc is distorted tetrahedral. Compounds 1 and 2, prepared from enantiopure L(1) and L(2), respectively, are enantiomers with similar structures, with the helical pitch in each being 17.0 A. Overall, the structure of 3 may be described as a one-dimensional helical chain with a pitch of 17.3 A, with each period corresponding to two L(2) ligands and two metal centers. The structure of [(Zn6L(2)6Cl12) x 2 H2O]n (4) contains six Zn(II) centers connected via six L(2) ligands to form a "bowed" helical repeat unit, with the pitch of the helix corresponding to 43.5 A. Supramolecular (intra- and intermolecular) aspects of all these unusual polymeric structures are discussed. Finally, the synthesis and characterization of an unprecedented six zinc-node discrete supramolecular assembly, [Zn6(L(1))3(L(2))3Cl12] (5), incorporating a 78-membered metallacycle, is also reported.