Systematic Investigation of the Hydrothermal Syntheses of Pr(III)−PDA (PDA = Pyridine-2,6-dicarboxylate Anion) Metal−Organic Frameworks

Role of biologically important imidazole moiety on the antimicrobial and anticancer activity of Fe(III) and Mn(II) complexes

Currently, most pathogens influencing a number of epidemics outline a notable warning to human health. It has pushed researchers to design new antimicrobial drugs using transition metals that are studied in proceeding fewer years for their antimicrobial properties. Henceforth, in this work, two mononuclear complexes [Imz-H][Fe(pda)₂]⋅1⋅3H₂O (1) and [Mn(Imz)₆]⋅2Cl^-⋅2H₂O (2) [Imz = imidazole and H₂pda = 2,6 pyridine dicarboxylic acid] are isolated and characterized systematically by various spectral and single-crystal XRD studies. The antimicrobial activity of the present hexadentate complexes of Fe(III) and Mn(II) against Gram-positive as well as Gram-negative bacteria is also assessed. Augmented activity against standard isolates of Staphylococcus aureus with a minimum inhibitory concentration (MIC) is observed. Similar activity was also observed toward Escherichia coli, Klebsiella pneumoniae and Listeria monocytogenes. 1 and 2 have excellent bactericidal activity, and no resistant mutant for S. aureus was seen. The compound also unveiled antibiofilm activity and was capable to disrupt significantly the pre-formed biofilms and this property was confirmed by XTT assay experiment. The MTT assay data indicate that 1 and 2 can be used as anticancer agents toward the RAW 64.7 (human macrophage/monocyte) cell line. Further, the molecular docking study reveals that the role of imidazole is very important in the biological activity of these complexes. Moreover, our results suggest that 1 and 2 with its effective anti-microbial, anti-biofilm and cytotoxicity activity can be used to treat bacterial and fungal infections and could be appraised clinically for further applications.Communicated by Ramaswamy H. Sarma.

Construction of high-nuclear 4p–4f heterometallic {Ln11Ge12} cluster-organic frameworks with high-sensitivity luminescence sensing of Fe3+ in aqueous solution

The [Pr₁₁Ge₁₂] 4p–4f cluster-organic framework shows highly selective and sensitive sensing of Fe³⁺ in aqueous solution.

Synthesis, crystal structure and magnetic properties of an octanuclear cerium(III) complex of pyridine-2,6-dicarboxylate

An octanuclear compound of cerium(III), [Ce8(Pydc)10(HPydc)4.22H2O].11H2O (1) (Pydc=pyridine-2,6-dicarboxylate anion) was prepared under mild solvothermal conditions and its crystal structure was determined by single-crystal X-ray diffraction. Three kinds of coordination environments are observed, which include: [Ce(Pydc)3], [Ce(Pydc)(H2O)4(O,O)], and [Ce(H2O)7(O,O)]. Each cerium atom in 1 is nine-coordinated but two different geometries are found. The Ce1 and Ce2 atoms exhibit a nearly tricapped trigonal prismatic CeN3O6 geometry, while Ce3 and Ce4 possess CeNO8 and CeO9 coordination polyhedra, which approximate to slightly distorted mono-capped square antiprisms having 12 triangular faces. The Pydc ligands adopt tri-, tetra-, and penta-coordination modes through tridentate chelating and, μ 2 and μ 3 -bridging modes, respectively. The clusters are joined by O–H···O hydrogen bonds to generate 3D supramolecular network. Magnetic susceptibility measurements for 1 indicate that the χ m values obey the Curie-Weiss law. The overall magnetic behavior is typical for the presence of antiferromagnetic exchange coupling interactions between the cerium(III) ions.

Ultrasound assisted facile synthesis of Mn(II) and Cu(II) coordination polymers and their use as precursors for α-Mn3O4 and CuO nanoparticles: Synthesis, characterization and catalytic properties

A self-assembly of pyridine-2,6-dicarboxylate with Cu(II) and Mn(II) under ultrasonic and microwave irradiation gave the two coordination polymers [Cu(PDA)(H₂O)_1.5]n (1) and [Mn(PDA)(H₂O)_1.5]n (2). Their structures were characterized using IR, elemental analysis, X-ray diffraction (XRD) and spectroscopic methods. The corresponding α-Mn₃O₄ and CuO nanoparticles were synthesized by calcination of 1 and 2 in air at 600 °C. Transmission electron microscopy (TEM) reveals a sphere-like morphology for the Mn₃O₄ nanoparticles. Shrinkage of the particle size from 90 nm (by conventional synthesis of the precursor) to 19 nm (ultrasonic-assisted) takes place, indicating the great effect of ultrasonication. CuO nanoparticles were of semispherical (conventional and ultrasonic-assisted methods) and hexagonal shapes (microwave irradiation) with an average diameter of 7, 15 and 25 nm, respectively. The catalytic performance of the coordination polymers towards degradation of methylene blue and methyl orange in the presence of hydrogen peroxide was studied. Using the same dose, catalyst 1 proved to be more efficient in color removal of both MB and MO than catalyst 2 did. Recycling test for 2 showed that it is a recyclable catalyst with no structural changes over three recycling experiments.

Lanthanide-based coordination compounds based on 4-(4-carboxyphenyl)-1,2,4-triazole: synthesis, structures, Hirshfeld surface and luminescence properties

Four compounds with dinuclear, 1-D and 2-D frameworks have been synthesized. Their Hirshfeld surface and luminescence properties were studied.

Crystal engineering of cadmium coordination polymers decorated with nitro-functionalized thiophene-2,5-dicarboxylate and structurally related bis(imidazole) ligands with varying flexibility

Five bis(imidazole) ligand modulated cadmium coordination polymers based on a new nitro-functionalized thiophene-2,5-dicarboxylate ligand or 4-nitro-thiophene-2-carboxylic acid involving in situ ligand synthesis.

3D lanthanide metal–organic frameworks constructed from lanthanide formate skeletons and 3,5-bis(4′-carboxy-phenyl)-1,2,4-triazole connectors: synthesis, structure and luminescence

3D Ln-MOFs constructed from lanthanide formate skeletons and 3,5-bis(4′-carboxy-phenyl)-1,2,4-triazole connectors show tunable luminescence emission including white light emission.

Hydrogen bonded-extended lanthanide coordination polymers decorated with 2,3-thiophenedicarboxylate and oxalate: synthesis, structures, and properties

Five new LnCPs decorated with H₂tdc and oxalate mixed ligands exhibit a 2D sql layer structure, then the 2D layers are further linked by intermolecule hydrogen bonds to form a 3D supramolecular network with sxb topology.

Alkaline earth metal-based metal–organic framework: hydrothermal synthesis, X-ray structure and heterogeneously catalyzed Claisen–Schmidt reaction

Two alkaline earth metal based carboxylate framework systems, [Mg(HL)(H₂O)₂]_n (1) and [Ca(H₂L)₂]_n (2) (H₃L = chelidamic acid) have been hydrothermally synthesized and characterized. Both compound 1 and its dehydrated species heterogeneously catalyze Claisen–Schmidt reaction.

Hydrothermal synthesis and crystal structure of novel bis(6-carboxypyridine-2-carboxylato-κ3O2,N,O6)nickel(II) trihydrate, Ni(Hpydc)2·3H2O

The synthesis and crystal structure of the compound bis(6-carboxypyridine-2-carboxylato-κ(3)O(2),N,O(6))nickel(II) trihydrate, Ni(Hpydc)(2)·3H(2)O, with a supramolecular network is reported (H(2)pydc is pyridine-2,6-dicarboxylic acid). The compound has been prepared by hydrothermal methods. The crystal structure has been solved by direct methods using single-crystal X-ray diffraction data collected at 293 K and refined by full-matrix least-squares procedures to a final R value of 0.0323 for 2779 observed reflections. The compound has distorted octahedral geometry around the metal centre. The complex contains two identical singly ionized ligand molecules. The nickel(II) is bonded to four O atoms and two N atoms from the tridentate ligand molecules, which are nearly perpendicular to each other. Hydrogen-bonded interactions create a three-dimensional supramolecular porous network. The supramolecular structure accounts for the porous structure of the compound as is evident from the Brunauer, Emmett & Teller (BET) surface area of 80 m(2) g(-1). Thermal degradation of the compound shows that lattice water molecules give stability to the crystal structure.