Crystal structure, thermal stability and theoretical investigation on four 1,3-bis(1,2,4-triazol-1-yl)propane-based copper(II) complexes

Self-assembly of flexible 1,3-bis(1,2,4-triazol-1-yl)propane (btp), inorganic Cu(II) salt and rigid benzene-based carboxylate coligand generates four complexes, {[Cu(btp)₂(CH₃OH)(H₂O)]·H₂O·2ClO₄}_n (1), {[Cu(btp)(Hbtc)₂]·0.5H₂O}_n (2), [Cu(btp)₂(H₃btea)₂]_n (3), and [Cu(btp)(nb)₂] (4) (H₃btc = 1,3,5-benzenetricarboxylic acid, H₄btea = 1,2,4,5-benzenetetracarboxylic acid, Hnb = p-nitrobenzoic acid), which are fully structural characterized by single-crystal X-ray crystallography, elemental analysis, IR, and TG-DTA techniques. Structural determinations reveal that the polymeric two-dimensional (2D) Cu-btp grid-like layer for 1, 1D linear single- and double-stranded chains for 2 and 3, as well as the discrete binuclear structure for 4, are jointly directed by the coordination polyhedrons of the Cu(II) ion and the exo-bidentate bridging btp core ligand with various conformations. The theoretical calculations suggest that the trans-trans btp is the most stable conformation, and the metal binding site is collectively determined by the electron density of N donors and the spatial orientation of the btp ligand. Unexpectedly, the polycarboxylate anions in 1-4 can only act as terminal coligands not popular bridging connectors. The thermal stability of the resulting complexes is also compared.     

2D Holodirected lead(II) bromide coordination polymers constructed of rigid and flexible ligands

Three new 2D Pb^II coordination polymers containing 4,4′-bipyridine (4,4′-bipy), 1,2-bis(4-pyridyl)ethane (bpa) and 1,2-bis(4-pyridyl)ethene (bpe) with bromide anions, [Pb(μ-4,4′-bipy)(μ-Br)₂]_n (1), [Pb(μ-bpa)(μ-Br)₂]_n (2) and [Pb(μ-bpe)(μ-Br)₂]_n (3) have been synthesized and characterized by elemental analysis, IR spectroscopy and their structures studied by X-ray crystallography. The thermal stability of compounds 1-3 was studied by thermal gravimetric (TG) and differential thermal analyses (DTA). The single-crystal X-ray data shows that the Pb²⁺-ions have coordination numbers of six and contain the rarely holodirected geometries.     

Mercury(II) acetate/thiocyanate coordination polymers with n-donor ligands, spectroscopic, thermal and structural studies

Three new mercury(II) coordination polymers, [Hg₂(μ-bpa)(μ-SCN)₂(μ-CH₃COO)₂]_n (1), [Hg₂(μ-4-bpdb)_1.5(μ-CH₃COO)(μ_1,1- SCN)(μ_1,3-SCN)(SCN)]_n · CH₃CN (2) and [Hg(μ-3-bpdb)(CH₃COO)₂]_n (3) {(bpa = 1,2-bis(4-pyridyl)ethane, 4-bpdb) = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene and 3-bpdb = 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene, have been synthesized and characterized by CHN elemental analysis and IR spectroscopy. The single crystal X-ray data show the compound 1 is two-dimensional coordination polymer as a result of simultaneously bridging 1,2-bis(4-pyridyl)ethane, acetate and thiocyanate ligands. The single-crystal X-ray data of the compound 2 show that the complex to be a two-dimensional polymer, one of Hg atoms has four-coordinate and one of them has seven-coordinate. Three SCN⁻ anions show three different coordination modes with terminal, μ_1,1-bridge and μ_1,3-bridge fashions. The structural studies of compound 3 show the structure may be considered a one-dimensional coordination polymer of mercury(II) consisting of linear chains formed by a bridging 3-bpdb ligand. The thermal stabilities of these compounds were studied by thermal gravimetric (TG) and differential thermal analyses (DTA).     

Two silver(I) coordination solids in a single crystallization: Flexible metallacyclodimer versus helical channel network

Studies on the self-assembly of AgClO₄ with 1,2-bis(dimethyl(4-pyridyl)silyl)ethane (L) were carried out. The slow diffusion of an organic solution of L into an aqueous solution of AgClO₄ affords two different single crystalline solids, block and thin-plate crystals. The block crystal consists of metallacyclodimers of, [Ag(L)]₂(ClO₄)₂ whereas the thin-plate crystal consists of unique ligand-induced helical channel networks, [Ag₂(L)₃](ClO₄)₂. The block and thin-plate crystals form in a ratio of 1:9, respectively, in a mixture of water and ethanol, but the ratio is depending on solvents and concentrations. In addition, the block crystal has two significantly different metallacyclodimeric structures in a unit cell, presumably owing to the flexible 26-membered cyclodimer including a flexible transannular argentophilic interaction. Such subtle effects may be ascribed to the existence of a variety of eclipsed, gauche, or anti-conformers of L.     

Cobalt, nickel, copper and cadmium coordination polymers containing the bis(1,2,4-triazolyl)methane ligand

Co(II), Ni(II), Cu(II) and Cd(II) coordination polymers containing the flexible ditopic bis(1,2,4-triazol-1-yl)methane ligand (Btm) have been prepared by reaction of equimolar quantities of the corresponding cobalt, nickel, copper and cadmium salts in EtOH solution. Structure solution and refinement of polycrystalline materials were performed by powder diffraction technique (XRPD), using conventional laboratory data. The results show that architecturally different coordination polymers were obtained depending on the counter-ion employed. The XRPD results show also that non-covalent interactions are driving forces for the occurrence of different structures.     

A series of 1-D to 3-D metal-organic coordination architectures assembled with V-shaped bis(pyridyl)thiadiazole under co-ligand intervention

Six new coordination polymers based on V-shaped linkage 2,5-bis(4-pyridyl)-1,3,4-thiadiazole (bpt) and transition metal ions, [Co(bpt)(pm)_0.5(H₂O)]_n · 3nH₂O (1), [Cu₂(bpt)(pm)(H₂O)₄]_n (2), [Co(bpt)(pydc)]_n · 2nCHCl₃ · nH₂O (3), [Cu₂(bpt)(pydc)₂(H₂O)₂]_n (4), [Cu₂(bpt)(pydco)₂(H₂O)₂]_n · nH₂O (5) and [Cd(bpt)(pydco)]_n (6) (H₄pm = pyromellitic acid, H₂pydc = pyridine-2,6-dicarboxylic acid, H₂pydco = pyridine-2,6-dicarboxylic acid N-oxide), have been synthesized under the intervention of various polycarboxylate ligands. Complex 1 exhibits a 3-D 4-connected structure with 1-D nanosized open channels encapsulated lots of water molecules. Complex 2 represents a 2-D grid containing two types of rectangular windows. When pydc and pydco instead of pm, complexes 3 and 6 were obtained with highly undulated 2-D layers. The interlayers of 3 are filled with two kinds of solvent molecules, whereas 6 is a double-layered framework without free molecules. Complexes 4 and 5 consist of two distinct 1-D infinite chains held together to form different 2-D supramolecular networks. Importantly, bpt spacer shows changeful conformational geometries and generates complicated crystalline architectures with the introduction of polycarboxylate ligands. Additionally, thermal stability of complexes 1, 3 and 5, fluorescent properties of 6 and X-ray powder diffraction of 1 have also been investigated.     

Synthesis, structure and blue luminescent properties of a new silver(I) triazolate coordination polymer with 810-a topology

A novel 3D coordination polymer [Ag(dmtrz)] (dmtrz = 3,5-dimethyl-1,2,4-triazole) (1) was prepared under solvothermal condition and structurally characterized. The crystal structure reveals that Ag(I) centers are firstly linked via dmtrz anions to form an infinite 2₁ helix, which is further interconnected to four neighboring anti-parallel helices to form a 3D framework with rare non-interpenetrating 8²10-a topology.     

Synthesis and crystal structure determination of 0D-, 1D- and 3D-metal compounds of 4-(pyrid-4-yl)-1,2,4-triazole with zinc(II) and cadmium(II)

The potentially tritopic bridging ligand 4-(pyrid-4-yl)-1,2,4-triazole (pytz) reacts with cadmium(II) nitrate tetrahydrate, Cd(NO₃)₂·4H₂O and sodium dicyanamide (Na-dca) to form the molecular complex [Cd(dca)₂(κN_py-pytz)₂(H₂O)₂] (1). The cadmium atom lies on a center of inversion and is coordinated in a slightly distorted octahedral geometry by the trans-oriented pytz ligands, dicyanamide anions and aqua ligands. The pytz ligand coordinates through the N_pyridin atom to the metal atom. The molecular complexes are connected to a 3D supramolecular network by O-H···N_dca and O-H···N_triazole hydrogen bonds. From zinc(II) bromide and pytz the compound 1D-[ZnBr₂(μ-κN_py,N_tz-pytz)] (2) is obtained where the pytz-ligand bridges between the tetracoordinated zinc(II) atoms through coordination of its N_pyridine- and N_triazole-atoms. Adjacent chains are connected through C-H···Br and C-H···N hydrogen bonds to form a 3D supramolecular structure. Single crystals of 2 crystallize homochiral in the non-centrosymmetric space group P2₁2₁2₁. The origin of the homochirality is the formation of hydrogen-bonded helices around the 2₁ screw axes with the same sense of rotation (left-handed or M in the investigated crystal). Cd(NO₃)₂·4H₂O, pytz and sodium thiocyanate (NaSCN) give the framework 3D-[Cd(μ-SCN)₂(μ-κN_py,N_tz-pytz)] (3). Parallel layers of 2D-{Cd(μ-SCN)₂}-nets with distorted (6,3)-net topology are assembled by the bridging pytz-ligands into a 3D-structure. The pytz-ligand bridges between two cadmium atoms by N_pyridine- and N_triazole-coordination.     

Synthesis,Antifungal Activity,DFT Study and Molecular Dynamics Simulation of Novel 4-(1,2,4-Oxadiazol-3-yl)-N-(4-phenoxyphenyl)benzamide Derivatives

In order to find novel potential antifungal agrochemicals, a series of new 4-(1,2,4-oxadiazol-3-yl)-N-(4-phenoxyphenyl)benzamide derivatives 3a – j were designed, synthesized and characterized by their ¹H - , ¹³C-NMR and HRMS spectra. The preliminary antifungal assay in vitro revealed that compounds 3a – j exhibited moderate to good antifungal activity against five plant pathogenic fungi. Especially, compound 3e presented significant antifungal activity against Alternaria solani, Botrytis cinerea and Sclerotinia sclerotiorum, superior to positive control boscalid. In the in vivo antifungal assay on tomato plants and cucumber leaves, compound 3e presented good inhibition rate against B. cinerea at 200 mg/L. Molecular dynamics simulation revealed that compound 3e could bind with the active site of class II histone deacetylase (HDAC).     

Chemiluminescent determination of H2O2 using 4-(1,2,4-triazol-1-yl)phenol as an enhancer based on the immobilization of horseradish peroxidase onto magnetic beads

This article describes the employment of a novel p-phenol derivative, 4-(1,2,4-triazol-1-yl)phenol (TRP), as a highly potent signal enhancer of the luminol-hydrogen peroxide (H₂O₂)-horseradish peroxidase (HRP) chemiluminescence (CL) system. The CL reaction conditions were optimized, and the enhancement characteristics of TRP were compared with those of p-iodophenol (PIP). TRP produced a strong enhancement of the CL with the effect of prolonging the light emission. The developed system was then applied to the determination of H₂O₂ with immobilized HRP using magnetic beads as a solid support. The linear range for H₂O₂ was 2.0 × 10⁻⁶ to 1.0 × 10⁻³ M. The detection limit for H₂O₂ was 2.0 × 10⁻⁶ M. The proposed sensor was applied successfully to the determination of H₂O₂ in rainwater.     

One-dimensional helical coordination polymers of cobalt(II) and iron(II) ions with 2,2′-bipyridyl-3,3′-dicarboxylate (BPDC)

One-dimensional (1-D) helical coordination polymers, [M^II(H₂O)₃(BPDC)]_n · nH₂O (M = Co (1), Fe (2)), have been prepared by the self-assembly of cobalt(II) and iron(II) ions, respectively, with 2,2′-bipyridyl-3,3′-dicarboxylic acid (H₂BPDC) in an aqueous solution. X-ray crystal structures of compounds 1 and 2 show that each metal ion displays a distorted octahedral coordination geometry including three water oxygen atoms, one oxygen atom of the carboxylate of a BPDC²⁻ belonging to the adjacent metal ion and two nitrogen atoms from the BPDC²⁻ acting as a chelating ligand. In 1 and 2, one carboxylate oxygen atom of coordinated BPDC²⁻ binds to the neighboring metal ion, which give rise to 1-D helical coordination polymers. The helical chains of 1 and 2 are linked by the hydrogen bonding interactions between the carboxylate oxygen atom of the BPDC²⁻ ion belonging to a chain and the water molecule of the adjacent helical chain, which lead to 2-D networks extending along the ab plane. The supramolecules 1 and 2 show isomorphous structures regardless of the metal ions.     

Layered and self-penetrated cadmium isophthalate and 5-methylisophthalate coordination polymers containing bis(4-pyridylformyl)piperazine or bis(4-pyridylmethyl)homopiperazine ligands

Hydrothermal synthesis has afforded divalent cadmium coordination polymers containing isophthalate (ip) or 5-methylisophthalate (mip) dicarboxylate ligands and bis(4-pyridylformyl)piperazine (4-bpfp) or bis(4-pyridylmethyl)homopiperazine (4-bpmh) tethers. {[Cd₂(ip)₂(H₂O)₂(4-bpfp)]·7H₂O}_n (1) displays a (4,4) grid topology based on {Cd₂O₂} dimeric clusters, along with “infinite” water molecule tapes with rare T4(0)A(1) classification. {[Cd(mip)(H₂O)(4-bpfp)]·3H₂O}_n (2) also exhibits (4,4) grid layers but with 2D + 2D → 3D mutual inclined interpenetration instead of parallel stacking. [Cd₄(ip)₄(4-bpmh)₂]_n (3) has tetrameric {Cd₄(ip)₄} cluster units linked by ip and 4-bpmh ligands into a unique self-penetrated 3,5,5,5-connected tetranodal net with (4.8²)(4³6²8⁵)(4⁴6⁴8²)(4.5⁶4⁸) topology. {[Cd₂(mip)₂(H₂O)₂(4-bpmh)]·2H₂O}_n (4) possesses a structure similar to that of 1, without the aggregated water molecule tapes. All four materials emit visible light upon ultraviolet excitation, ascribed to ligand-based electronic transitions.     

Zinc coordination polymers with 1-(3-aminopropyl)-imidazole as bridging bidentate unit

The reaction of Zn(SCN)₂ with one or two equivalents of 1-(3-aminopropyl)-imidazole (api) yields the coordination polymers [Zn(SCN)₂(api)]_n (1) and [Zn(SCN)₂(api)₂]_n (2), respectively. Single-crystal X-ray diffraction analysis reveals one-dimensional polymeric chain structures for both compounds. The structure of 1 consists of tetrahedral Zn(SCN)₂(api)₂ units linked by one molecule 1-aminopropyl imidazole in an unsymmetric mode, i.e., each metal center is coordinated by an imidazole nitrogen as well as a nitrogen of the aminopropyl group. The metal ions in 2 display an octahedral coordination geometry with each Zn(SCN)₂(api)₂ unit linked by two molecules of the imidazole, thus, exhibiting two imidazole and two amino groups in the coordination sphere. The polymers were further characterized by IR-, ¹H NMR- and ¹³C NMR-spectroscopy.     

Synthesis and characterization of one lead(II) photoluminescent coordination polymer with the fumarate ligand

One lead(II) coordination polymer, {[Pb(fum)(phen)]·2H₂O}_n (fum = fumarate, phen = 1,10-phenanthroline), was synthesized through the self-assembly of the lead(II) ion with the mixed fum and phen ligands and characterized by FT-IR spectroscopy, elemental analysis, thermogravimetric analysis, X-ray analysis and solid state photoluminescence spectrum. The compound shows a center-symmetrical dinuclear-based 2D architecture and further assembles into porous 3D supramolecular framework with 1D channel via interlayer π-π stacking interactions. The six-coordinated lead atoms in the complex show hemidirected geometry. The compound exhibits photoluminescence with the maximum emission located in UV region.     

Spectroscopic and structural analyses of the copper(II) 2-D coordination polymer {[Cu2(BPP)4(NCS)4]}n (BPP = 1,3-bis(4-pyridyl)propane) comprising interpenetrated layers of (4, 4) topology

The synthesis and structural characterization of the 2-D Cu(II) coordination polymer namely {[Cu₂(BPP)₄(NCS)₄]}_n, where BPP is the nitrogen ligand 1,3-bis(4-pyridyl)propane, are described. Single crystal diffraction analysis shows that the asymmetric unit consists on two crystallographically independent Cu(II) ions that adopt a distorted octahedral geometry. Each Cu(II) center is coordinated by four nitrogen atoms from different BPP ligands and by other two nitrogen atoms from isothiocyanate groups. The BPP ligands link the metal centers generating an undulated two-dimensional net of (4, 4) topology. Two sets of two-dimensional sheets interlock each other in the same plane, giving rise to a twofold parallel interpenetrating network. EPR spectra indicate no magnetic coupling of the two individual Cu²⁺ centers.     

Topological diversity in copper aromatic meta-dicarboxylate coordination polymers with bis(pyridylformyl)piperazine coligands

Hydrothermal synthesis has afforded divalent copper coordination polymers containing bis(4-pyridylformyl)piperazine (4-bpfp) tethers and aromatic meta-dicarboxylate ligands. {[Cu(ip)(4-bpfp)]·2H₂O}_n (1, ip = isophthalate) possesses a (4, 4) rectangular grid structure with an unusual ABCD stacking pattern along a 4₁ screw axis. Sterically bulky substituents in the 5-position of the isophthalate ligands reduced the coordination polymer dimensionality, with [Cu₂(tBuip)₂(4-bpfp)(H₂O)₂]_n (2, tBuip = 5-tert-butylisophthalate) and {[Cu(MeOip)(HMeOip)₂(4-bpfp)]·3H₂O}_n (3, MeOip = 5-methoxyisophthalate) displaying 1D polymeric ladder and chain motifs, respectively. Compound 3 possesses a rare twofold interpenetrated binodal supramolecular hms net with (6³)(6⁹8) topology. Longer meta-disposed acetate pendant arms induced a doubly interpenetrated 3D primitive cubic topology in {[Cu₂(1,3-phda)₂(H₂O)₂(4-bpfp)]}_n (4, 1,3-phda = 1,3-phenylenediacetate), which possesses antiferromagnetically coupled {Cu₂O₂} kernels (J = −6.14(8) cm⁻¹).     

One-dimensional silver(I) and mercury(II) complexes with 1,4-bis(1-benzyl-benzimidazol-2-yl)cyclohexane (N-BBzBimCH)

The crystal structures of four Ag(I) and Hg(II) complexes of the ligand 1,4-bis(1-benzyl-benzimidazol-2-yl)cyclohexane (N-BBzBimCH) have been described, that is, [Hg₂(N-BBzBimCH)Cl₄] (1), [Hg(N-BBzBimCH)Br₂] (2), [Ag(N-BBzBimCH)](NO₃)(H₂O) (3) and [Ag₂(N-BBzBimCH)(CF₃OCO)₂] (4). All these compounds show 1D polymeric structures in the solid state. In complexes 1 and 4, the chloride ions and the trifluoroacetate groups bridge the [Hg₂(N-BBzBimCH)Cl₂] and [Ag₂(N-BBzBimCH)] fragments, respectively, to generate 1D polymers. While the bromide ions in complex 2 and nitrate groups in complex 3 are only serving as terminal ligands to suffice the coordination geometry of the metal centers. In all cases, weak intermolecular interactions such as C-H?X (X = Cl, Br) contacts, hydrogen bonds, π-π interactions and C-H?π stacking play important roles to extend the 1D chain structures to 2D network. Solid state fluorescence of these compounds was also studied.     

Coordination network solids based on Cu(II) coordination compounds with 1,4-bis-(1,2,4-triazol-1-yl)-butane as a flexible alkyl spacer ligand: Synthesis, characterization and X-ray structures

The coordination chemistry of three selected copper(II) salts with the flexible ligand 1,4-bis(1,2,4-triazol-1-yl)butane (abbreviated as btb) is described. This ligand acts as a bidentate ligand, bridging copper(II) ions, thereby generating polymers in 2D and 3D network solids.     

Synthesis, crystal structures and in vitro anti-fungal activities of two silver(I) coordination polymers with fluconazole

Two new polymeric silver(I)-fluconazole complexes: [Ag(HFlu)(NO₃)]_n (1) and {[Ag(HFlu)₂](ClO₄)}_n (2), have been synthesized and structurally characterized. The crystal structure of 1 consists of infinite 1D single strand helical coordination arrays with alternative …PMPM… arrangements, which are interlinked through hydrogen bonding interactions to generate a 3D network. The shortest intrachain Ag?Ag distance bridged by HFlu ligand is 8.287(1) Å. In 2, each Ag(I) ion is coordinated by four triazole N atoms from four HFlu ligands to form a 2D coordination layer, which has a helical arrangement along the [1 0 0] direction. The results of anti-fungal studies demonstrate that both silver(I) complexes are more active in comparison to the fluconazole drug.     

Synthesis and crystal structure of a cobalt(II) coordination polymer constructed from 2,6-pyridinedicarboxylate anion and 1,3-bis(4-pyridyl)propane nitrogen ligand

The coordination polymer named {[Co(H₂O)₄(BPP)][Co(dipic)₂]·H₂O}_n (dipic = 2,6-pyridinedicarboxylate and BPP = 1,3-bis(4-pyridyl)propane) has been synthesized by the diffusion method and characterized by thermal analysis, vibrational spectroscopy and single crystal X-ray diffraction analysis. The compound is formed by an one-dimensional polymeric cationic chain, in which the BPP ligands connect the Co2 sites, and an anionic moiety formed by Co1 center and two dipic²⁻ anions. Both crystallographic independent metal sites adopt a distorted octahedral geometry. Co2 center is coordinated by two nitrogen atoms from BPP ligands and four oxygen atoms from aqua ligands, while Co1 center is coordinated by two nitrogen atoms and four oxygen atoms from two dipic²⁻ anions. The cationic and anionic moieties are connected through hydrogen bonding interactions leading to a 3D supramolecular array.