N-donor Sites Research Articles

A {PMo12}-based 2D sandwich-like supramolecular network constructed from a new semi-rigid amide-derived ligand with enhanced capacitive activity and electrochemical sensing performances

To achieve high electrochemical performance of polyoxometalates (POMs)-based materials, introducing POMs to crystalline supramolecular structures via hydrogen bonding interactions represents a potential strategy. Herein, a new semi-rigid pyrazole-amide-derived bis(pyridyl) ligand N,N'-bis(3-pyridinamide)-1-hydropyrazole (3-Hdpyp) was designed due to the abundant hydrogen bond sites of amide group, as well as the multiple N-donor sites, which was used to assemble with the Keggin-type [PMo12O40]3− (PMo12) anion and cobalt under solvothermal condition. A new 2D sandwich-like supramolecular network [Co2(3-dpyp)2(H2O)2][HPMo12O40] (1) was synthesized and structurally characterized. The PMo12 anions are fixed between the 1D metal–organic chains [Co2(3-dpyp)2(H2O)2]n2n+via hydrogen bonding interaction. Complex 1 shows excellent specific capacitances 1062.5F g−1 at the current density of 1 A g−1. After 1000 cycles, it can maintain 90.0% of the capacitance retention. Meanwhile, complex 1 represents an excellent amperometric sensor for measurement of Cr(VI) with low detection limit of 0.22 µM. The excellent electrochemical performance can be attributed the discrete 2D sandwich-like structures, which can improve the active area of POMs and conductivity of the network.

Leveraging Nitrogen Linkages in the Formation of a Porous Thorium-Organic Nanotube Suitable for Iodine Capture.

We report the synthesis, characterization, and iodine capture application of a novel thorium-organic nanotube, TSN-626, [Th6O4(OH)4(C6H4NO2)7(CHO2)5(H2O)3]·3H2O. The classification as a metal-organic nanotube (MONT) distinguishes it as a rare and reduced dimensionality subset of metal-organic frameworks (MOFs); the structure is additionally hallmarked by low node connectivity. TSN-626 is composed of hexameric thorium secondary building units and mixed O/N-donor isonicotinate ligands that demonstrate selective ditopicity, yielding both terminating and bridging moieties. Because hard Lewis acid tetravalent metals have a propensity to bind with electron donors of rival hardness (e.g., carboxylate groups), such Th-N coordination in a MOF is uncommon. However, the formation of key structural Th-N bonds in TSN-626 cap some of the square antiprismatic metal centers, a position usually occupied by terminal water ligands. TSN-626 was characterized by using complementary analytical and computational techniques: X-ray diffraction, vibrational spectroscopy, N2 physisorption isotherms, and density functional theory. TSN-626 satisfies design aspects for the chemisorption of iodine. The synergy between accessibility through pores, vacancies at the metal-oxo nodes, and pendent N-donor sites allowed a saturated iodine loading of 955 mg g-1 by vapor methods. The crystallization of TSN-626 diversifies actinide-MOF linker selection to include soft electron donors, and these Th-N linkages can be leveraged for the investigation of metal-to-ligand bonding and unconventional topological expressions.

Synthesis, characterization, anti-microbial and cytotoxic applications of zinc(II) complexes

ABSTRACT. In the present research, three zinc(II) complexes were synthesized using 3-(3-fluorophenyl)-2-methylacrylic acid (HL), 1,10-phenanthroline and 2,2'-pyridine as ligands. The composition, structural confirmation, coordination way of ligand and assignment of geometry to the complexes were made by different analytical tools like elemental analysis, FTIR and 1H-NMR. The ligand 3-(3-fluorophenyl)-2-methylacrylate appeared to coordinate the metal (Zn) atom via COO- moiety in all of the complexes (1-3) while 1,10-phenanthroline and 2,2'-pyridine co-ordinated to Zn(II) atom through N-donor sites in complexes 2 and 3, respectively. The complex 1 showed four while 2 and 3 showed six co-ordinated geometry. The synthesized complexes were evaluated for antimicrobial and cytotoxic activities. The obtained results showed that complexes are active against microbial agents and exhibited significant cytotoxicity.
 
 KEY WORDS: Co-coordination, Geometry, Zinc(II) complexes, Biological activity
 
 Bull. Chem. Soc. Ethiop. 2021, 35(2), 287-299.
 DOI: https://dx.doi.org/10.4314/bcse.v35i2.6

Efficient capture of ReO4− on magnetic amine-functionalized MIL-101(Cr): Revealing from selectivity to mechanism

The efficient decontamination of pertechnetate (99TcO4−) is an essential task for managing radioactive 99Tc in nuclear wastes. Perrhenate, (ReO4−), as a nonradioactive analog, exhibits almost identical physicochemical properties as 99TcO4−. Herein, a novel magnetic amine-functionalized MIL-101(Cr) (NH2-MIL-101(Cr)@Fe3O4) was prepared and used to efficiently remove ReO4− from solution for the facile magnetic separation. A series of environmental parameters were considered to investigate the adsorption performance of NH2-MIL-101(Cr)@Fe3O4. Experimental results suggested that NH2-MIL-101(Cr)@Fe3O4 has reached a satisfied adsorption capacity (~401 mg/g) and a very fast adsorption kinetics at pH 7.0. The selectivity for ReO4− was maintained even in the presence of interfering anions with relatively high concentrations. ReO4− were mainly captured by N-donor sites of the surface-decorated amine via complexation and were trapped in the cavities of modified MIL-101(Cr). NH2-MIL-101(Cr)@Fe3O4 exhibits satisfactory adsorption performance for ReO4− and can be conveniently separated from wastewaters after adsorption.

Zn(II)-Based Coordination Polymer for Detection of Picric Acid in Aqueous Media and Treatment Effect against Deep Vein Thrombosis by Reducing P-ERK2 and p53 Expression.

The coordination polymers based on Zn(II) ions and the metal nodes which has chemical formula of {[Zn3(L)2(tib)2(H2O)2]·(DMF)2}n (1) was synthesized via using 1,3,5-tris(1-imidazolyl)benzene (tib) and 2,6-di(4-carboxylphenyl)pyridine-4-carboxylic acid (H3L) as ligands under solvothermal conditions. Given its strong luminescent emission at room temperature and the uncoordinated N-donor sites in the framework, the selective detection performance of 1 toward the nitroanalytes was studied, 1's sensitive fluorescence quenching reactions along with selectivity to the electron-deficient TNP over other analytes of nitro within the aqueous phase was studied via the method of fluorescence quenching titration. Furthermore, the treatment effect of the compound on the deep vein thrombosis (DVT) was evaluated. Firstly, the ELISA was carried out to determine IL-17A content. Then, the platelet function was determined via the western blot by measuring expression level of platelet activation signaling pathway protein p-ERK2 and p53.

Microporous MOF with open metal sites for CO2 fixation and protective effect on osteoarthritis by regulating the activation of PI3K/AKT pathway

A novel microporous metal-organic framework (MOF) based on Zn(II) ion as node with the chemical formula of {[Zn(H2O)(HL)]·(DMF)2(H2O)2}n (1, H3L ​= ​2-(4-carboxyphenyl)-1H-benzo[d]imidazole-5-carboxylic acid, DMF ​= ​N,N-dimethylformamide), which has rich water-coordinated metal centers and high density of free N-donor groups has been successfully prepared via H3L ligand and Zn(NO3)2·6H2O reaction within H2O, EtOH along with DMF mixed solvent. The presence of open metal sites along with the basic N-donor sites in the resulting activated 1a induces a moderate high sorption capacity of CO2. In addition, because of basic N-donor groups along with Lewis acidic Zn2+ ions, 1a has become an efficient heterogeneous catalyst, which can chemically fix CO2 in the carbonate of cyclic annular at mild room temperature. Furthermore, the influence of compound on the activation of PI3K/AKT signaling pathway was studied by Western blot. The ELISA was carried out the evaluate the IL-18 and IL-6 content in synovial cells after compound treatment.

Ethylene-Bridged Hexadentate Bis(amidines) and Bis(amidinates) with Variable Binding Sites.

Hexadentate bis(amidines) form versatile networks of hydrogen bonds both in solid state and solution, as revealed by X-ray crystallography, IR, and NMR spectroscopy. Moreover, the corresponding bis(amidinates) produce blue and green emissions in THF solution. Tethered tetradentate bis(amidines) have emerged in coordination chemistry, enantioselective catalysis, as building blocks for polyfunctional heterocycles, and in photoluminescent materials. The next generation of flexible bis(amidine)/bis(amidinate) platforms with up to six N-donor sites has now been established.

Efficient oxidation of benzene catalyzed by Cu(II) tetrazolato complexes under mild conditions

Two new coordination complexes containing 5-(4-chlorophenyl)tetrazolato (4-Clptz) and polypyridyl ligands, [Cu2(bipy)2(4-Clptz)4] [1, bipy = 2,2′-bipyridine] and [Cu2(phen)2(4-Clptz)4] [2, phen = 1, 10 phenanthroline] have been synthesized following metal ligated [2 + 3] cycloaddition reaction between copper bound azide polymer containing polypyridyl and 4-chloro benzonitrile. Both the complexes have been fully characterized by different spectroscopic techniques. Single crystal X-ray diffraction study reveals that the complexes are dimeric in nature with penta-coordinated geometry around the Cu(II) centre through N-donor sites. These complexes have been explored as homogeneous catalysts for the selective oxidation (in presence of hydrogen peroxide) of benzene to phenol and benzoquinone under mild conditions in an open atmosphere condition.

Framework disorder and its effect on selective hysteretic sorption of a T-shaped azole-based metal-organic framework.

Metal-organic frameworks with highly ordered porosity have been studied extensively. In this paper, the effect of framework (pore) disorder on the gas sorption of azole-based isoreticular Cu(II) MOFs with rtl topology and characteristic 1D tubular pore channels is investigated for the first time. In contrast to other isoreticular rtl metal-organic frameworks, the Cu(II) metal-organic framework based on 5-(1H-imidazol-1-yl)isophthalate acid has a crystallographically identifiable disordered framework without open N-donor sites. The framework provides a unique example for investigating the effect of pore disorder on gas sorption that can be systematically evaluated. It exhibits remarkable temperature-dependent hysteretic CO2 sorption up to room temperature, and shows selectivity of CO2 over H2, CH4 and N2 at ambient temperature. The unique property of the framework is its disordered structure featuring distorted 1D tubular channels and DMF-guest-remediated defects. The results imply that structural disorder (defects) may play an important role in the modification of the performance of the material.

Synthesis and characterization of a holmium 2,2′-bipyridine-5,5′-dicarboxylate MOF: Towards the construction of a suitable holmium carrier

Based on the 2,2′-bipyridine-5,5′-dicarboxylic acid ligand (H2bpdc), a new metal–organic framework using holmium as the coordinating metal site was synthesized through a solvothermal reaction. The 3D compound {[Ho2(bpdc)3(DMF)2]·2(DMF)}n (1) was characterized by single crystal X-ray diffraction, FTIR, TGA and PXRD. The coordination between H2bpdc, the solvent, and holmium (CN = 7) allows for the construction of a MOF containing potentially free metal sites and uncoordinated N-donor sites. These features make this MOF an attractive holmium carrier for radiotherapeutic applications.

Bimetallic d10 -Metal Complexes of a Bipyridine Substituted N-Heterocyclic Carbene.

The hybrid ligand 3-(2,2'-bipyridine-6-ylmethyl)-1-mesityl-1H-imidazolylidene (NHCBipy ) featuring both carbene and N-donor sites, was selectively complexed with various d10 metal cations in order to examine its coordination behavior with regard to homo and heterometallic structures. Respective silver complexes can be obtained by the silver oxide route and are suitable transmetallation reagents for the synthesis of gold(I) compounds. Starting from the mononuclear complexes [(NHCBipy )AuCl], [(NHCBipy )Au(C6 F5 )] and [(NHCBipy )2 Au][ClO4 ], open-chain as well as cyclic heterobimetallic complexes containing Cu+ , Ag+ , Zn2+ , Cd2+ , and Hg2+ were synthesized. Furthermore, the homobimetallic species [(NHCBipy )2 M2 ][ClO4 ]2 (M=Cu, Ag) were obtained. All bimetallic compounds were fully characterized including single-crystal X-ray analysis. Their photoluminescence (PL) properties were investigated in the solid state at temperatures between 15 and 295 K and compared with those of the mononuclear species. There is a clear difference in PL properties between the open chain and the cyclic heterobimetallic complexes. The latter species show different PL properties, depending on the metals involved. In addition, collision-induced dissociation (CID) experiments were performed on electrosprayed cations of the cyclic heterobimetallic compounds, to compare the metal binding at the carbene and N-donor sites.

Effect of N-donor sites of bis-pyridyl-bis-amide ligands on the architectures of three Anderson-type polyoxometalate-based metal–organic complexes

Three polyoxometalate-based metal–organic complexes [Co2(H2O)6(TeMo6O24)](3-H2dpyb)·2H2O (1), [M2(4-Hdpyb)2(H2O)6(TeMo6O24)]·6H2O [M = Co (2), Zn (3); 3-dpyb = N,N′-bis(3-pyridinecarboxamide)-1,4-butane, 4-dpyb = N,N′-bis(4-pyridinecarboxamide)-1,4-butane] have been hydrothermally synthesized and characterized by elemental analysis, IR, TG, powder diffraction and single-crystal X-ray diffraction analysis. The structure of complex 1 consists of 1D [Co2(H2O)6(TeMo6O24)] inorganic chains, which are joined together by the 3-dpyb ligands through weak hydrogen bonds to generate a 2D supramolecular network. Complexes 2 and 3 are isostructural; each [TeMo6O24]6− (TeMo6) polyoxoanion chelates either two cobalt or two zinc atoms to generate the discrete complexes [Co2(4-Hdpyb)2(H2O)6(TeMo6O24)] and [Zn2(4-Hdpyb)2(H2O)6(TeMo6O24)], respectively. The electrochemical properties, electrocatalytic and photocatalytic activities of the complexes have been investigated.

Assembly, structures, electrocatalytic and photocatalytic properties of a series of Anderson-type polyoxometalate-based metal–organic complexes based on flexible pyridyl-amide ligands

Five new Anderson-type polyoxometalate-based metal–organic complexes, [Cu4(μ3-OH)2(H2O)6(4-dpye)2(TeMo6O24)]·2H2O (1), [Cu(4-dpyb)(CrMo6(OH)6O18)2(H2O)2][Cu(4-dpyb)(H2O)4](4-H2dpyb)·6H2O (2), H[Cu2(3-dpyb)2(C2O4)(CrMo6(OH)6O18)]·8H2O (3), [Cu2(4-dpyh)(CrMo6(OH)5O19)(H2O)8]·10H2O (4) and [Cu4(μ2-OH)(μ3-OH)(H2O)6(4-dpyh)(TeMo6O24)]·H2O (5) (4-dpye=N,N′-bis(4-pyridinecarboxamide)-1,2-ethane, 4-dpyb=N,N′-bis(4-pyridinecarboxamide)-1,4-butane, 3-dpyb=N,N′-bis(3-pyridinecarboxamide)-1,4-butane, 4-dpyh=N,N′-bis(4-pyridinecarboxamide)-1,6-hexane), were hydrothermally prepared and structurally characterized by single crystal X-ray diffraction analyses and characterized by single-crystal X-ray diffraction, elemental analysis, IR, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA). Complex 1 is a 2D network, which is constructed from Cu4–TeMo6 inorganic chains and 4-dpye ligands. Complex 2 contains two types of 1D chains. Complex 3 shows a 1D ring-like chain structure, in which the CrMo6 anions act as fourfold monodentate ligands consolidating the [Cu2(3-dpyb)2(C2O4)] rings. Complex 4 is a 0D structure containing a dinuclear complex cation [Cu2(4-dpyh)]4+ and discrete CrMo6 anion. Complex 5 exhibits a 3D framework constructed from 2D Cu4–TeMo6 inorganic layer and 4-dpyh ligands. The spacer lengths and N-donor sites of the bis-pyridyl-bis-amide ligands, as well as different polyoxometalates play important roles in tuning the structures of the title complexes. The electrochemical behavior and electrocatalytic properties, as well as the photocatalytic activities of the title complexes have been studied.

A facile approach for the synthesis of hydroxyl-rich microporous organic networks for efficient CO2 capture and H2 storage.

A new series of porous organic networks (PONs) internally decorated with several free -OH functional groups has been synthesized through acid catalyzed condensation reaction of terephthalaldehyde and nucleophilic aromatic compounds. These materials possess high Brunauer-Emmett-Teller specific surface areas (592-865 m2 g-1) and showed maximum CO2 adsorption capacity of 4.31 mmol g-1 and H2 uptake of 8.23 mmol g-1 at 273 and 77 K, respectively, under 1 bar.

Two new porous UiO-66-type zirconium frameworks; open aromatic N-donor sites and their post-synthetic methylation and metallation

Free pyridyl functionality is incorporated into two new MOFs through an unusual high acidity route, and exploited through post-synthetic modification.

Pd-Catalyzed C-H arylation of pyridazine-based fused 1,2,4-triazoles: overriding selectivity at the usual position by undermining of preferred chelate formation.

The applicability of C-H functionalization to medicinally important 2-pyridyl-based N-heterocycles suffers from severe challenges owing to the high Lewis basicity of the N-atom. This arrests catalytic activity and yields undesirable positional selectivity due to preferential chelate formation. In this regard, we report a novel palladium(ii)-catalyzed arylation strategy on multiple-N-containing pyridazines by over-riding the functionalization due to a chelated palladacycle. We report a regioselective mono-arylation at the 8-position of diphenyl azolopyridazines without any ortho-C-H activation on the proximal phenyl groups. This methodology presents a broad arylation scope with uncompromised yield and positional selectivity, including the heteroarylation of N-heterocycles, which is an unprecedented feat for these types of molecules.

Structural and theoretical characterization of a new twisted 4'-substituted terpyridine compound: 4'-(isoquinolin-4-yl)-2,2':6',2''-terpyridine.

4'-Substituted derivatives of 2,2':6',2''-terpyridine with N-containing heteroaromatic substituents, such as pyridyl groups, might be able to coordinate metal centres through the extra N-donor atom, in addition to the chelating terpyridine N atoms. The incorporation of these peripheral N-donor sites would also allow for the diversification of the types of noncovalent interactions present, such as hydrogen bonding and π-π stacking. The title compound, C24H16N4, consists of a 2,2':6',2''-terpyridine nucleus (tpy), with a pendant isoquinoline group (isq) bound at the central pyridine (py) ring. The tpy nucleus deviates slightly from planarity, with interplanar angles between the lateral and central py rings in the range 2.24 (7)-7.90 (7)°, while the isq group is rotated significantly [by 46.57 (6)°] out of this planar scheme, associated with a short Htpy...Hisq contact of 2.32 Å. There are no strong noncovalent interactions in the structure, the main ones being of the π-π and C-H...π types, giving rise to columnar arrays along [001], further linked by C-H...N hydrogen bonds into a three-dimensional supramolecular structure. An Atoms In Molecules (AIM) analysis of the noncovalent interactions provided illuminating results, and while confirming the bonding character for all those interactions unquestionable from a geometrical point of view, it also provided answers for some cases where geometric parameters are not informative, in particular, the short Htpy...Hisq contact of 2.32 Å to which AIM ascribed an attractive character.

Moisture-Stable Zn(II) Metal-Organic Framework as a Multifunctional Platform for Highly Efficient CO2 Capture and Nitro Pollutant Vapor Detection.

A moisture-stable three-dimensional (3D) metal-organic framework (MOF), {(Me2NH2)[Zn2(bpydb)2(ATZ)](DMA)(NMF)2}n (1, where bpydb = 4,4'-(4,4'-bipyridine-2,6-diyl)dibenzoate, ATZ = deprotonated 5-aminotetrazole, DMA = N,N-dimethylacetamide, and NMF = N-methylformamide), with uncoordinated N-donor sites and charged framework skeleton was fabricated. This MOF exhibits interesting structural dynamic upon CO2 sorption at 195 K and high CO2/N2 (127) and CO2/CH4 (131) sorption selectivity at 298 K and 1 bar. Particularly, its CO2/CH4 selectivity is among the highest MOFs for selective CO2 separation. The results of Grand Canonical Monte Carlo (GCMC) simulation indicate that the polar framework contributes to the strong framework-CO2 binding at zero loading, and the tetrazole pillar contributes to the high CO2 uptake capacity at high loading. Furthermore, the solvent-responsive luminescent properties of 1 indicate that it could be utilized as a fluorescent sensor to detect trace amounts of nitrobenzene in both solvent and vapor systems.

A metal dicyanamide cluster with high CO2/N2 selectivity

A new microporous metal dicyanamide cluster, Co(hmt)(dca)2 (hmt: hexamethylenetetramine, dca: dicyanamide), with accessible N-donor sites exhibits high CO2/N2 selectivity, 83 at 295 K and 1 bar, for a mixture with a 15:85 CO2 to N2 ratio. Adsorption studies show that the use of hmt and dca moieties as building blocks for solid adsorbents can enhance the CO2:surface interactions due to N atoms available inside the pores, which is confirmed by X-ray single crystal studies.

The rigid isomeric 5-(x-pyridyl)-1H-tetrazole ligands-directed various isopolymolybdate-based compounds: assembly, structures, and properties

Two new isopolymolybdate-based metal–organic complexes, [Cu2(2-ptz)2(Mo4O14)0.5] (1) and [Cu3(OH)2(3-ptz)4(γ-H4Mo8O26)(H2O)4]·10H2O (2) (2-ptzH = 5-(2-pyridyl)-1H-tetrazole, 3-ptzH = 5-(3-pyridyl)-1H-tetrazole), constructed from isomeric ligands with different N-donor sites were synthesized under hydrothermal conditions. In 1, each [Mo4O14]4− cluster connected with six neighboring [Mo4O14]4− clusters through six binuclear [Cu2(2-ptz)2]2+ subunits to yield a 2-D layer. In 2, bidentate inorganic [Mo8O26]4− anions link the trinuclear [Cu3(OH)2(3-ptz)4] clusters to construct a 1-D chain. Adjacent chains connect through Mo–N bonds between the [Mo8O26]4− anions and pyridyl groups from the trinuclear clusters to form a 2-D layer. The effect of the N-donor sites of the rigid isomeric ligands on the structures of 1 and 2 was discussed. The electrochemical properties and photocatalytic activities of 1 and 2 have also been studied.