Phosphomolybdic acid hydrate encapsulated in MIL-53 (Fe): a novel heterogeneous heteropoly acid catalyst for ultrasound-assisted regioselective nitration of phenols

In this study, a heterogeneous catalyst, PMA@MIL-53 (Fe) (MIL ⇒ Matériaux de l'Institut Lavoisier), has been used to replace the usual mineral acids such as sulfuric acid. A wide variety of nitration methods require the use of a mixture of acids such as concentrated nitric acid and sulfuric acid, which result in producing a large amount of acidic waste. During recent years, the use of the heterogeneous system for the nitration of aromatic compounds has been highly considered and used by chemists due to some specific advantages, i.e. easy separation of the product from the reaction mixture, the possibility of recycling and reusing the catalyst, etc. Herein, the catalyst was synthesized using a metal-organic framework and a heteropoly phosphomolybdic acid. The PMA@MIL-53 (Fe) was prepared using a similar method of MIL-53 (Fe) synthesis. Afterwards, FeCl3·6H2O and 1,4-benzene dicarboxylic acid (BDC) in a dimethylformamide solution were placed in an ultrasound bath and, then, HPA (heteropoly acid) was added to the reaction mixture. The PMA (phosphomolybdic acid) encapsulation in MIL-53 (Fe) was confirmed using various analysis. Under optimal conditions, the catalytic activity of PMA@MIL-53 (Fe) was evaluated in nitration of phenol under ultrasonic waves. Besides, the ratio of the two products of ortho and para was obtained using GC. Optimum conditions were reached after 15 minutes, in such a way that the loaded PMA was 0.02 g under optimal conditions, the efficiencies of ortho-nitrophenol and para nitrophenol were 54.98 and 45.01, respectively.

Tuning the interpenetration of metal–organic frameworks through changing ligand functionality: effect on gas adsorption properties

Two interpenetrated MOFs are constructed with a 2-connected ligand, whereas one non-interpenetrated MOF is constructed by using a 3-connected ligand.

Lanthanide complexes based on a conjugated pyridine carboxylate ligand: structures, luminescence and magnetic properties

Three lanthanide compounds have been synthesized, namely, {[Dy₂(bpda)₃(H₂O)₃]₄·2H₂O}(Dy-1), {[Sm(bpda)₂·(H₂O)]·H₂O}_n (Sm-2) and {[Tb₂(bpda)₃(H₂O)₃]₄·2H₂O} (Tb-3) (H₂bpda = 2,2′-bipyridine-6,6′-dicarboxylic acid). Their structures were determined by single crystal X-ray diffraction and characterized by elemental analysis, infrared spectroscopy and thermogravimetric analysis. Dy-1 and Tb-3 are isostructural with a conjugate bimolecular four-nuclear cluster structure constructed with intramolecular hydrogen bonds and they form a 3D supramolecular structure with intermolecular hydrogen bonding. Sm-2 is a one-dimensional chain structure and is further connected by intricate hydrogen bonds into a three-dimensional supramolecular structure. These three compounds exhibit significant characteristic luminescence from the ligand to the central Ln(iii) ion, which is found by solid-state photoluminescence measurement. Sm-2 exhibits a long luminescence lifetime and high fluorescence quantum yield. A slow relaxation phenomenon is observed for the dysprosium compound by measuring the alternating-current susceptibility at low temperature and the underlying mechanism was further confirmed by theoretical calculations.

The structures, fluorescence and magnetic properties of series three lanthanide complexes have been investigated. Dysprosium complex exhibit the single-molecule behavior.

Syntheses, structures, and magnetic properties of mixed-ligand complexes based on 3,6-bis(benzimidazol-1-yl)pyridazine

Six new metal-organic coordination polymers (CPs) [Ni(L)(2,5-TDC)(H2O)] n (1), [Ni(L)(1,3-BDC)(H2O)] n (2), [Ni(L)(1,4-BDC)(H2O)] n (3), [Mn(L)(2,5-TDC)(H2O)] n (4), [Mn(L)(2,6-PYDC)(H2O)] n (5) and [Mn(L)(1,4-NDC)] n (6) were achieved by reactions of the corresponding metal salt with mixed organic ligands (L = 3,6-bis(benzimidazol-1-yl)pyridazine, 2,5-H2TDC = thiophene-2,5-dicarboxylic acid, 1,3-H2BDC = isophthalic acid, 1,4-H2BDC = terephthalic acid, 2,6-H2PYDC = pyridine-2,6-dicarboxylic acid, 1,4-H2NDC = naphthalene-1,4-dicarboxylic acid) under solvothermal condition. CPs 1-6 were characterized by single-crystal X-ray diffraction, IR, TG, XRD and elemental analyses. Their structures range from the intricate 3D CPs 1, 3, 4 and 6 to the 2D coordination polymer 2 and the infinite 1D chain 5. The CPs 1-4 and 6 underlying networks were classified from the topological viewpoint, disclosing the distinct sql (in 1), pcu (in 3 and 6), new topology (in 2), and dia (in 4) topological nets. Moreover, analysis of thermal stability shows that they had good thermal stability. Finally, magnetic properties of CPs 1-6 have been studied, the results showed that complex 2 had ferromagnetic coupling and complexes 1, 3-6 were antiferromagnetic.

A novel 3D Cd(ii) coordination polymer generated via in situ ligand synthesis involving C-O ester bond formation

A novel 3D Cd(ii) coordination polymer {[Cd(ddpa)(2,2′-bpy)]·H₂O}_n (1) (H₂ddpa = 5,10-dioxo-5,10-dihydro-4,9-dioxapyrene-2,7-dicarboxylic acid, 2,2′-bpy = 2,2′-bipyridine) is hydrothermally synthesized in situ, and the influencing factors and mechanism for the in situ reaction are briefly discussed. The synthesis of 1 requires the formation of a new C–O ester bond. This current study confirms that metal ions and N-donor ligands play important roles in the domination of the in situ ligand from 6,6′-dinitro-2,2′,4,4′-biphenyltetracarboxylic acid (H₄dbta). Furthermore, the structure, thermal stability and photoluminescent property of 1 are also investigated.

A 3D Cd(ii) coordination polymer comprising ligand molecules not included in the original reaction mixtures but instead formed via in situ ligand synthesis involving a C–O ester bond.