Hydrothermal Assembly, Structural Multiplicity, and Catalytic Knoevenagel Condensation Reaction of a Series of Coordination Polymers Based on a Pyridine-Tricarboxylic Acid

A pyridine-tricarboxylic acid, 5-(3',5'-dicarboxylphenyl)nicotinic acid (H3dpna), was employed as a adjustable block to assemble a series of coordination polymers under hydrothermal conditions. The seven new coordination polymers were formulated as [Co(μ3-Hdpna)(μ-dpey)]n·nH2O (1), [Zn4.5(μ6-dpna)3(phen)3]n (2), [Co1.5(μ6-dpna)(2,2'-bipy)]n (3), [Zn1.5(μ6-dpna)(2,2'-bipy)]n (4), [Co3(μ3-dpna)2(4,4'-bipy)2(H2O)8]n·2nH2O (5),[Co(bpb)2(H2O)4]n[Co2(μ3-dpna)2(H2O)4]n·3nH2O (6), and [Mn1.5(μ6-dpna)(μ-dpea)]n (7), wherein 1,2-di(4-pyridyl)ethylene (dpey), 1,10-phenanthroline (phen), 2,2'-bipyridine(2,2'-bipy),4,4'-bipyridine(4,4'-bipy),1,4-bis(pyrid-4-yl)benzene (bpb), and 1,2-di(4-pyridyl)ethane (dpea) were employed as auxiliary ligands. The structural variation of polymers 1-7 spans the range from a 2D sheet (1-4, 6, and 7) to a 3D metal-organic framework (MOF, 5). Polymers 1-7 were investigated as heterogeneous catalysts in the Knoevenagel condensation reaction, leading to high condensation product yields (up to 100%) under optimized conditions. Various reaction conditions, substrate scope, and catalyst recycling were also researched. This work broadens the application of H3dpna as a versatile tricarboxylate block for the fabrication of functional coordination polymers.

Coordination Polymers from an Amino-Functionalized Terphenyl-Tetracarboxylate Linker: Structural Multiplicity and Catalytic Properties

An amino-functionalized terphenyl-tetracarboxylic acid, 2'-amino-[1,1':4',1″-terphenyl]-3,3″,5,5″-tetracarboxylic acid (H4tpta), was used as an adaptable linker to synthesize, under hydrothermal conditions, eight coordination polymers (CPs). The obtained products were formulated as [Co(μ6-H2tpta)]n (1), [Co(μ3-H2tpta)(2,2'-bipy)]n (2), [M3(μ6-Htpta)2(2,2'-bipy)2]n (M = Mn (3), Cd (4)), [Ni2(μ4-tpta)(phen)2(H2O)4]n (5), [Zn2(μ6-tpta)(phen)2]n (6), {[Zn2(μ6-tpta)(μ-4,4'-bipy)]·H2O}n (7), and [Zn2(μ6-tpta)(μ-H2biim)(H2O)2]n (8), wherein 2,2'-bipyridine (2,2'-bipy), 4,4'-bipyridine (4,4'-bipy), 1,10-phenanthroline (phen), or 2,2'-biimidazole (H2biim) are present as additional stabilizing ligands. The structural types of 1-8 vary from one-dimensional (1D) (2, 5) and two-dimensional (2D) (3, 4, 6) CPs to three-dimensional (3D) metal-organic frameworks (MOFs) (1, 7, and 8) with a diversity of topologies. The products 1-8 were investigated as catalysts in the Knoevenagel condensation involving aldehydes and active methylene derivatives (malononitrile, ethyl cyanoacetate, or tert-butyl cyanoacetate), leading to high condensation product yields (up to 99%) under optimized conditions. Various reaction conditions, substrate scope, and catalyst recycling were investigated. This work broadens the application of H4tpta as a versatile tetracarboxylate linker for the generation of diverse CPs/MOFs.

Zinc(II)-Based Ring-and-Rod Coordination Layer as an Excitation-Wavelength-dependent Dual-Emissive Chemosensor for Discriminating Fe3+, Cr3+, and Al3+ in Water

The reactions of Zn(NO3)2, 3,6-bis(pyridin-3-yl)-9H-carbazole (bpycz), and 2,5-dihydroxyterephthalic acid (H4dhbdc) or 2-bromoterephthalic acid (Br-1,4-H2bdc) under hydro(solvo)thermal conditions yielded corresponding coordination polymers (CPs) {[Zn(H2dhbdc)(bpycz)]•0.5H2O}n (1) and [Zn(Br-1,4-bdc)(bpycz)]•2DMAc•H2O (2), respectively, with high thermal stability approaching 350 °C. CP 1 adopts a ring-and-rod layer structure, which is topologically described as a 4-connected net with the point symbol of 2•65. Two layers are interpenetrated in parallel interlocking mode to form a double 2D → 2D polyrotaxane entanglement with extra-framework void space of 19.6%. CP 2 has a non-interpenetrating ring-and-rod layer structure of 4-connected 2•65 net topology, with extra-framework void space of 16.6%. Thermally activated 1 and 2 revealed CO2 uptakes of 101.1 and 98.6 cm3 g-1, respectively, at P/P0 = 1 and 195 K. X-ray powder diffraction (XRPD) patterns confirmed that 1 and 2 both possessed high chemical stability in H2O, CH3OH, acetone, and DMF, and framework stability during gas adsorption-desorption. The H2O suspension of 1 displayed excitation-dependent dual-emissive properties, appearing at 432 nm upon excitation at 300 nm and at 528 nm upon excitation at 365 nm. Of note, 1 was capable of detection of Fe3+, Cr3+, and Al3+ ions in H2O, showing good anti-interference ability, excellent selectivity, and high sensitivity. More interesting, the dual-emissive properties make 1 to be an excellent luminescence chemosensor to screen Fe3+, Cr3+, and Al3+ from a pool of metal ions in H2O upon excitation at 300 nm via luminescence quenching effect and then discriminate Fe3+, Cr3+, and Al3+ upon excitation at 365 nm via luminescence quenching, unaltered, and enhancement responses, respectively. On the other hand, the H2O suspension of 2 demonstrated an excitation-independent emission appearing at around 430 nm, which could be utilized to sensitively detect Fe3+ and Cr3+ ions with good anti-interference ability and excellent selectivity via luminescence quenching effect. Further, 1 and 2 were recyclability and possessed cycling stability. The plausible sensing mechanisms for 1 and 2 toward Fe3+, Cr3+, and Al3+ were also explored in detail.

Synthesis of New Derivatives of Benzylidinemalononitrile and Ethyl 2-Cyano-3-phenylacrylate: In Silico Anticancer Evaluation

In this study, microwave-assisted Knoevenagel condensation was used to produce two novel series of derivatives (1-6) from benzylidenemalononitrile and ethyl 2-cyano-3-phenylacrylate. The synthesized compounds were characterized using Fourier transform infrared (FT-IR) and ¹H NMR spectroscopies. The pharmacodynamics, toxicity profiles, and biological activities of the compounds were evaluated through an in silico study using prediction of activity spectra for substances (PASS) and Absorption, Distribution, Metabolism, Excretion, and Toxicity (ADMET) studies. According to the PASS prediction results, compounds 1-6 showed greater antineoplastic potency for breast cancer than other types of cancer. Molecular docking was employed to investigate the binding mode and interaction sites of the derivatives (1-6) with three human cancer targets (HER2, EGFR, and human FPPS), and the protein-ligand interactions of these derivatives were compared to those reference standards Tyrphostin 1 (AG9) and Tyrphostin 23 (A23). Compound 3 showed a stronger effect on two cell lines (HER2 and FPPS) than the reference drugs. A 20 ns molecular dynamics (MD) simulation was also conducted to examine the ligand's behavior at the active binding site of the modeled protein, utilizing the lowest docking energy obtained from the molecular docking study. Enthalpies (ΔH), Gibbs free energies (ΔG), entropies (ΔS), and frontier molecular orbital parameters (highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap, hardness, and softness) were calculated to confirm the thermodynamic stability of all derivatives. The consistent results obtained from the in silico studies suggest that compound 3 has potential as a new anticancer and antiparasitic drug. Further research is required to validate its efficacy.

X-ray Structure Analyses and Biological Evaluations of a New Cd(II) Complex with S-Triazine Based Ligand

The crystal structure of a new penta-coordinated Cd(II) complex of the formula [Cd(BPMT)Br2] was presented. This Cd(II) complex was synthesized by mixing Cd(NO3)2·4H2O and 2,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)-6-methoxy-1,3,5-triazine (BPMT) in the presence of KBr. It crystallized in the monoclinic crystal system and P21/n space group. The crystal parameters are a = 11.3680(8) Å, b = 11.1648(8) Å, c = 15.8593(11) Å, and β = 103.563(2)°, while the unit cell volume is 2190.6(12) Å3 and it comprised four molecules. The supramolecular structure of the [Cd(BPMT)Br2] complex is mainly controlled by the intermolecular Br∙∙∙H interactions. Hirshfeld calculations predicted the H∙∙∙H (38.1%), Br∙∙∙H (24.3%), C∙∙∙H (11.1%), and N∙∙∙H (9.5%) interactions are the most dominant. Biological evaluations for the antimicrobial and anticancer properties of the studied complex are presented. The Cd(II) complex has better anticancer and antibacterial activities than the free BPMT ligand. The anticancer activity against lung carcinoma (A-549) is higher for the former (18.64 ± 1.09 µg/mL) compared to the latter (372.79 ± 13.64 µg/mL). Additionally, the best antibacterial activity for the Cd(II) complex was found against B. subtilis.

Synthesis, structures and properties of metal–organic frameworks prepared using a semi-rigid tricarboxylate linker

A series of MOFs constructed from 5-((carboxymethyl)amino)isophthalic acid (H3cmai) have been prepared and characterised, with [Cd3(cmai)2(H2O)4]·4H2O demonstrating loss of water in a single-crystal-to-single-crystal transformation.

Coordination Polymers in Dicyanamido-Cadmium(II) with Diverse Network Dimensionalities

The synthesis and structural characterization of six dicyanamido-cadmium(II) complexes are reported: catena-[Cd(μ1,3-dca)(μ1,5-dca)(3-ampy)] (1), catena-[Cd3(μ1,3,5-dca)2(μ1,5-dca)4(pyNO)2(H2O)2] (2), catena-{Cd(H2O)2(μ1,5-dca)2](2,6-lut-NO)} (3), catena-[Cd(Me2en)(μ1,5-dca)2] (4), catena-[Cd(Me4en)(μ1,5-dca)2] (5), and [Cd(1,8-damnp)2(dca)2] (6), where dca = dicyanamide anion, 3-ampy = 3-aminopyridine, pyNO = pyridine-N-oxide, 2,6-lut-NO = 2,6-lutidine-N-oxide, Me2en = N,N-dimethyl-ethylenediamine, Me4en = N,N,N′,N′-tetramethyl-ethylenediamine, and 1,8-damnp = 1,8-diaminonaphthaline. The coordination polymers have different dimensionalities: 1 and 5 form 3D networks structures; 3 and 4 form polymeric 1D chains and 1DD double chains, respectively. Ribbons of three fused polymeric chains are observed in 2. In 6, the mononuclear complex units form a hydrogen-bonded supramolecular 3D network. In the coordination polymer compounds, the dca linkers display three bonding modes: the most common μ1,5-dca and the least popular μ1,3- and μ1,3,5-dca bonding. The luminescence emission and thermal properties of the complexes were investigated.

MOFs assembled from C3 symmetric ligands: structure, iodine capture and role as bifunctional catalysts towards the oxidation-Knoevenagel cascade reaction

Three new NiII/CoII-metal organic frameworks were self-assembled by the reaction of C3 symmetric 1,3,5-tribenzoic acid (H3BTC) and 2,4,6-tris(4-pyridyl)-1,3,5-triazine (4-TPT) ligands and NiII/CoII salts under solvothermal conditions. Isomorphous MOF1 and MOF2 exhibit a 3D pillar-layer framework based on binuclear M2(OH)(COO)2 units connected by tritopic BTC3- and 4-TPT ligands with a novel (3,5)-connected topology net. MOF3 displays a 3-fold interpenetrated 3D network exhibiting a (3,4)-connected topology net. The porous MOF3 can reversibly take up I2. The activated MOFs contain both Lewis acid (NiII center) and basic (uncoordinated pyridyl or carboxylic groups) sites, and act as bifunctional acid-base catalysts. The catalytic measurements demonstrate that the activated MOF3 exhibits good activities for benzyl alcohol oxidation and the Knoevenagel reaction and can be recycled and reused for at least four cycles without losing its structural integrity and high catalytic activity. Thus, the catalytic properties for the oxidation-Knoevenagel cascade reaction have also been studied.

A highly stable Zn coordination polymer exhibiting pH-dependent fluorescence and as a visually ratiometric and on–off fluorescent sensor

A thermally and chemically stable Zn coordination polymer exhibiting pH-dependent fluorescence behaves as a multi-responsive fluorescent sensor for ratiometric and on–off detection of multiple analytes.

Metal–organic architectures designed from a triphenyl-pentacarboxylate linker: hydrothermal assembly, structural multiplicity, and catalytic Knoevenagel condensation

Eight new metal(ii) coordination compounds driven by a triphenyl-pentacarboxylate linker were hydrothermally assembled and fully characterized. Their structural features and catalytic behavior were investigated.

Synthesis of benzylidenemalononitrile by Knoevenagel condensation through monodisperse carbon nanotube-based NiCu nanohybrids

Monodisperse nickel/copper nanohybrids (NiCu@MWCNT) based on multi-walled carbon nanotubes (MWCNT) were prepared for the Knoevenagel condensation of aryl and aliphatic aldehydes. The synthesis of these nanohybrids was carried out by the ultrasonic hydroxide assisted reduction method. NiCu@MWCNT nanohybrids were characterized by analytical techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), and Raman spectroscopy. According to characterization results, NiCu@MWCNT showed that these nanohybrids form highly uniform, crystalline, monodisperse, colloidally stable NiCu@MWCNT nanohybrids were successfully synthesized. Thereafter, a model reaction was carried out to obtain benzylidenemalononitrile derivatives using NiCu@MWCNT as a catalyst, and showed high catalytic performance under mild conditions over 10-180 min.

A dual functional MOF-based fluorescent sensor for intracellular phosphate and extracellular 4-nitrobenzaldehyde

A hydrazine-functionalized Zr(iv) MOF was used for the selective and sensitive detection of intracellular PO₄³⁻ ions and extracellular 4-nitrobenzaldehyde.

Coordination frameworks containing compounds as catalysts

This article describes a collection of MOF containing compounds as catalysts in a diverse range of organic transformation reactions.

Three Cluster Organic Frameworks Constructed from Tetranuclear Cluster Units: Structure and Properties

By treating a semirigid 5-oxyacetate isophthalic acid (H₃ OAIP) ligand with MnSO₄ /CoSO₄ /CdSO₄ under solvothermal conditions, three isostructural cluster organic frameworks, [M₂ (OH)(OAIP)(DMA)]⋅H₂ O (M=Mn²⁺ (1), Co²⁺ (2), Cd²⁺ (3); DMA=N,N'-dimethylacetamide) were constructed. The three complexes contain novel eight-connected tetranuclear M₄ (OH)₂ (COO)₆ (OCH₂ COO)₂ clusters with the unique hexagonal bipyramidal configuration, which are extended by four-connected OAIP linkers to form an uncommon (4,8)-connected alb-4,8-Cmce topology based on (3,6)-connected kgd sublayers. Both 1 and 2 showed significant antiferromagnetic interactions between the intracluster metal ions, whereas 3 revealed strong blue photoluminescence.

Synthesis, Structure, and Ligand-Centered Catalytic Properties of MII Coordination Polymers (M=ZnII , CdII , HgII ) with Open Pyridyl N-Oxide Sites

Four M^II (M=Zn^II , Cd^II , Hg^II ) coordination polymers were designed and synthesized based on two pyridine N-oxide bridging ligands: 3,5-bis(4-pyridyl)pyridine N-oxide and 2,6-bis(3-pyridyl)pyridine N-oxide. The resulting polymers all feature a one-dimensional chain motif and contain free pyridyl moieties. More importantly, they exhibit interesting ligand-centered (pyridyl N-oxide) catalytic behavior, and can be used as highly heterogeneous catalysts to promote the Knoevenagel condensation reaction under ambient conditions.

Crystal structure of dimethyl 9H-carbazole-2,7-di-carb-oxy-late

In the title compound, C₁₆H₁₃NO₄, the carbazole ring system is almost planar with non-H atoms possessing a mean deviation from planarity of 0.037 Å. The two ester groups are orientated trans to one another and tilted slightly from the mean plane of the carbazole ring system, making dihedral angles of 8.12 (6) and 8.21 (5)°. In the crystal, mol­ecules are linked by pairs of N—H⋯O hydrogen bonds forming inversion dimers. The dimers are linked by parallel slipped π–π inter­actions, forming slabs propagating along the b-axis direction [inter-centroid distance = 3.6042 (8) Å, inter-planar distance = 3.3437 (5) Å, slippage = 1.345 Å].

Hydrothermal syntheses, structural characterizations, and magnetic properties of five MOFs assembled from C2-symmetric ligand of 1,3-di(2′,4′-dicarboxylphenyl)benzene with various coordination modes

Five new complexes with appealing structural features from 0D paddle wheel {Cu₂(COO)₄} SBUs to 3D frameworks were reported to better understand the synthon selectivity in multifunctional crystal structures.

Structural diversities and related properties of four coordination polymers synthesized from original ligand of 3,3′,5,5′-azobenzenetetracarboxylic acid

Four CPs, derived from the original 3,3′,5,5′-azobenzenetetracarboxylic acid ligand were obtained under solvothermal conditions.

Assembly of three coordination polymers based on a sulfonic–carboxylic ligand showing high proton conductivity

Three MOFs with different structures all exhibit proton conduction behavior, especially for the Cu compound with a proton conductivity of 3.46 × 10⁻³ S cm⁻¹ at 368 K and 95% RH.

Synthesis and click modification of an azido-functionalized Zr(iv) metal–organic framework and a catalytic study

A new azido-functionalized Zr(iv) MOF was synthesized and further functionalized via post-synthetic click reactions, and the amino-tagged MOF is a base catalyst for Knoevenagel condensation.

Structural diversity of five coordination polymers based on 2,6-bis(3,5-dicarboxyphenyl)pyridine ligand: solvothermal syntheses, structural characterizations, and magnetic properties

Five CPs, featuring diverse structures, have been assembled from the mixed ligands of H₄BDP and bib under different reaction conditions.