Syntheses, structures, luminescent and gas adsorption properties of five new interpenetrated, 2D and 3D metal–organic frameworks based on a semi-rigid bis(imidazole)-carbazole ligand

On-Surface Isomerization of Indigo within 1D Coordination Polymers

Natural products are attractive components to tailor environmentally friendly advanced new materials. We present surface-confined metallosupramolecular engineering of coordination polymers using natural dyes as molecular building blocks: indigo and the related Tyrian purple. Both building blocks yield identical, well-defined coordination polymers composed of (1 dehydroindigo : 1 Fe) repeat units on two different silver single crystal surfaces. These polymers are characterized atomically by submolecular resolution scanning tunnelling microscopy, bond-resolving atomic force microscopy and X-ray photoelectron spectroscopy. On Ag(100) and on Ag(111), the trans configuration of dehydroindigo results in N,O-chelation in the polymer chains. On the more inert Ag(111) surface, the molecules additionally undergo thermally induced isomerization from the trans to the cis configuration and afford N,N- plus O,O-chelation. Density functional theory calculations confirm that the coordination polymers of the cis-isomers on Ag(111) and of the trans-isomers on Ag(100) are energetically favoured. Our results demonstrate post-synthetic linker isomerization in interfacial metal-organic nanosystems.

3-(5-(1H-imidazol-1-yl) pent-1-en-1-yl)-9-ethyl-9H-carbazole: synthesis, characterization (IR, NMR), DFT, antimicrobial-antioxidant activities and docking study

3-(5-(1H-imidazol-1-yl) pent-1-en-1-yl)-9-ethyl-9H-carbazole called as compound 1 was synthesized and characterized by proton and carbon-13 nuclear magnetic resonance (¹H- and ¹³C- NMR) and Fourier transform infrared (FTIR) spectroscopic methods. Density Functional Theory/Becke, 3-parameter (DFT/B3LYP), for compound 1 were performed with 6-311++G(d,p) method. Optimized geometry, frontier molecular orbitals (HOMO; highest occupied molecular orbital; LUMO: lowest unoccupied molecular orbital), IR and NMR parameters of compound 1 were obtained. The evaluations reveal that the calculation results support the experimental results. In addition, the antimicrobial (a microwell dilution method) and antioxidant activities (2,2-Diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) ferric ion reducing antioxidant power (FRAP) of compound 1 were evaluated. According to the results obtained, it showed higher antimicrobial activity (Minimal inhibition concentration (MIC): 78.12 µg/mL) against B. subtilis subsp. Spizizenii. Morever, molecular docking studies were carried out to investigate the interactions of an antimicrobial agent on some important enzymes played important roles in nucleic acid (Deoxyribo nucleic acid (DNA) synthesis, cell wall synthesis, protein synthesis, and metabolism etc. The compound 1 was strongly bound to tyrosyl-tRNA synthetase enzyme (binding energy: -11.18 and K_i: 6.37 nM) and Beta-Ketoacyl-Acp Synthase III enzyme (binding energy: -10.29 and K_i: 28.47 nM).Communicated by Ramaswamy H. Sarma.

Temperature-induced structural diversity of metal-organic frameworks and their applications in selective sensing of nitrobenzene and electrocatalyzing the oxygen evolution reaction

Structural diversities are presented in four new Co-MOFs containing 1,5-bi(imidazolyl)anthracene and different dibenzobarrelene skeletons based on dicarboxylic acid, in which MOFs 1-3 exhibit 2D networks in a 4-connected node sql topology with the point symbol of {44·62}, while MOF 4 forms a 1D chain structure. It is clearly observed that the 2D-1D structural transformation of 2-4 has been realized by temperature modulated hydrothermal synthesis procedures from 120-160 °C, suggesting the key role of temperature for constructing MOFs. In addition, obvious π-π interactions between anthracene rings can be observed in the architectures of 1-3, which may favorably stabilize their 2D supramolecular networks. More importantly, fluorescence behaviors of 1-4 have been investigated in water among various nitro-aromatic compounds (NACs) and the results show that all samples exhibit high selectivity and fine sensitivity to nitrobenzene (NB) with fluorescence quenching, which is confirmed to be the result of electron transfer from the excited state of ligands to that of NB by density functional theory. Furthermore, MOFs 1-4 have been directly employed as electrocatalysts for the oxygen evolution reaction (OER), in which MOF 4 gives the best activity towards the OER among all as-synthesized samples with an overpotential of 398 mV at a current density of 10 mA cm-2 and a low Tafel slope of 59 mV dec-1.

Metal–organic frameworks based on tetraphenylpyrazine-derived tetracarboxylic acid for electrocatalytic hydrogen evolution reaction and NAC sensing

Tetraphenylpyrazine-derived tetracarboxylic acid-based new MOFs and their promising applications in the electrocatalytic hydrogen evolution reaction.

Gas adsorption, magnetic, and fluorescent sensing properties of four coordination polymers based on 1,3,5-tris(4-carbonylphenyloxy)benzene and bis(imidazole) linkers

Four 3D novel coordination polymers (CPs) have been synthesized under solvothermal conditions. Furthermore, gas sorption behaviors revealed that complex 1 has excellent selective separation for CO₂/CH₄.

Cd and Hg coordination complexes based on a heterocyclic multidentate ligand: Synthesis, structures and photoluminescence properties

The complexes [Cd(cpbi)Cl2]·(H2O), [Hg2(cpbi)2Cl4] and [Hg(cpbi)Br2] (cpbi = [5-chloro-2-(pyrazin-2-yl)-1H-benzoimidazole]) have been synthesised using solvent evaporation reactions and structurally characterised by single-crystal X-ray diffraction. The first complex displays a one-dimensional (1-D) chain structure, the second has a binuclear structure, while the third is mononuclear. The complexes show different luminescence properties.