Binuclear Zn Research Articles

Unprecedented cyclic-salamo-based compound and binuclear Zn(II) salamo-based complex originated from a double-armed salamo-based ligand: Experimental and theoretical studies

In this work, a double-armed salamo-based ligand H2L1 modified by pyridine ring was synthesized. It was found that the cyclic salamo-based compound H2L2 and binuclear Zn(II) complex [Zn2(L3)(H2O)2](NO3)2 are formed on the basis of X-ray single crystal diffraction. They are obtained separately by the reactions of H2L1 with Sr(OAc)2 and Zn(NO3)2⋅6H2O in different organic solutions. Interestingly, the compound H2L2 is formed by the cleavage and recombination of the ligand H2L1 catalyzed by Sr(OAc)2, and is the first cyclic salamo-based compound. It was worth noting, in the process of forming Zn(II) complex, the ligand H2L1 is hydrolyzed to H2L3, the formation of H2L3 is due to the hydrolysis and fracture of C=N double bonds, which reduces the original formyl groups and forms a new ligand H2L3 containing two exposed formyl groups. The specific coordination mode of the Zn(II) complex is that Zn1 atom is located in O4 cavity, Zn2 atom is located in N2O2 cavity of the ligand (L3)2− unit, and two oxygen atoms on formyl groups reduced by the fracture of connecting arm also participate in coordination, and two phenoxy groups on the (L3)2− unit are bridged with Zn1 and Zn2 atoms at the same time. In addition, two water molecules on Zn1 and Zn2 participate in the coordination, and the Zn(II) atoms form hexacoordinated octahedral configurations. Nitrate ions do not participate in coordination, and their main function are to maintain the charge balance of the complex. UV–Vis titration experiment showed that the binding ratio between the ligand and Zn(II) atoms is 1:2, which is in accordance with the result of X-ray single crystal structure. This shows that the coordination ratio in solution state and solid state is the same. The cyclic-salamo compound H2L2 and Zn(II) complex were analyzed by DFT and Hirshfeld surface analysis. Through the analysis of fluorescence titration spectra, it was found that compared with the ligand H2L1, the fluorescence intensity increases obviously after adding Sr2+ and Zn2+ ions respectively, and gradually increases with the increasement of ion concentration.

A novel binuclear Zn2+ and Cd2+ complexes of carbothiohydrazide chelating agent for the corrosion protection of carbon steel alloy in 15% HCl solution

A novel binuclear Zn²⁺ and Cd²⁺ complexes of carbothiohydrazide chelating agent for the corrosion protection of carbon steel alloy in 15% HCl solution

A Bifunctional Three-Dimensional Zn(II) Metal-Organic Framework with Strong Luminescence and Adsorption Cr(VI) Properties.

The mixed ligand 3-amino-1,2,4-triazole (Hatz) and terephthalic acid (H2pta) reacted with Zn(NO3)2·6H2O to synthesize a three-dimensional binuclear Zn(II) metal-organic framework: {[Zn2·(atz)2·(pta)]·3H2O}n (3D-Zn-MOF). This 3D-Zn-MOF has two different types of pores (4.5 × 4.5 Å2, 5.7 × 5.7 Å2). The crystalline 3D-Zn-MOF could be prepared into nanomaterials (3D-N-Zn-MOF) with particles of approximately 100 nm by a cell fragmentation apparatus. Compared with the solid-state luminescence of Hatz and H2pta, it was found that 3D-N-Zn-MOF exhibited strong luminescence performance and significant red-shift phenomenon. Due to the decrease in electronegativity and rigidity of ligands, as well as the effect of ligand metal charge transfer (LMCT), the fluorescence lifetime and quantum yield of 3D-ZN-N-MOF were 2.7241 ns and 3.02%, respectively. The maximum experimental adsorption capacity of 3D-N-Zn-MOF could reach 125.52 mg/g, which was superior to the majority of MOF adsorbents under the optimal adsorption conditions (25 °C, pH = 7, and the adsorbent concentration is 0.2000 g/L). The thermodynamic analysis of adsorption showed that the adsorption of Cr(VI) by 3D-N-Zn-MOF was a spontaneous (△G < 0) and exothermic (△H < 0) process. It could be found that 3D-N-Zn-MOF was a bifunctional material with potential applications by comprehensive analysis of the fluorescence and adsorption Cr(VI) performance.

Biphenol-based tetradentate N2O2 donor scaffold binuclear Zn(II) and trinuclear Cu(II) Complexes: Synthesis, Structure, Characterizations, and catalytic cyanosilylation of aldehydes at room temperature

In this work, two dinuclear Zn(II) complexes [Zn(H2L1)]2(complex 1), [Zn(H2L2)]2(complex 2), and a trinuclear Cu(II) complex [Cu(H2L2)]3 (complex 3) (H2L1 = 3,3′-bis-[(2,6-dimethyl-phenylimino)-methyl]-[1,1′]-biphenyl-2,2′-diol, H2L2 = 2,6-diethyl phenylimino)-ethyl]-[1,1′]-biphenyl-2,2′- diol) are reported. The complexes 1, 2 &3 have been produced and isolated for the first time in a well-defined and air-stable form by reacting biphenol-based tetradentate N2O2-type (H2L1 and H2L2) ligands with the respective metal acetate salts. The synthesised compounds were characterized by UV–Vis spectroscopy, elemental analysis, mass spectrometry and Fourier-transform infrared spectroscopy (FT-IR). Single crystal X-ray diffraction (SCXRD) study revealed distorted tetrahedral geometry surrounding the core Zn2+ cations (1–2) that were bridging the teradentate N2O2 ligands. In complex-3, the Cu(II) center is four-coordinated via tetradentate N2O2 donor ligand, forming slightly distorted square planar geometry with an angular C2-symmetric core and exhibits weak antiferromagnetic (AF) interactions. Hirshfeld surface analysis and fingerprint plots were used to investigate the intermolecular interactions in the crystalline state. Strong H…H and H… C/C…H intermolecular interactions were seen on the Hirshfeld surface when it was mapped over dnorm, shape index, and curvature. These interactions were found to be the main contributors to crystal packing. Excellent catalytic activity was demonstrated for the dinuclear zinc(II) complexes [Zn(H2L1)]2 (1)and [Zn(H2L2)]2 (2) in the cyanosilylation reaction of various aryl aldehydes into value-added cyanohydrins at room temperature and under solvent free conditions.

Solid-State Structural Transformation in Zn(II) Metal-Organic Frameworks in a Single-Crystal-to-Single-Crystal Fashion.

Solid-state structural transformation is an interesting methodology used to prepare various metal-organic frameworks (MOFs) that are challenging to prepare in direct synthetic procedures. On the other hand, solid-state [2 + 2] photoreactions are distinctive methodologies used for light-driven solid-state transformations. Meanwhile, most of these photoreactions explored are quantitative in nature, in addition to them being stereo-selective and regio-specific in manner. In this work, we successfully synthesized two photoreactive novel binuclear Zn(II) MOFs, [Zn2(spy)2(tdc)2] (1) and [Zn2(spy)4(tdc)2] (2) (where spy = 4-styrylpyridine and tdc = 2,5-thiophenedicarboxylate) with different secondary building units. Both MOFs are interdigitated in nature and are 2D and 1D frameworks, respectively. Both the compounds showed 100% and 50% photoreaction upon UV irradiation, as estimated from the structural analysis for 1 and 2, respectively. This light-driven transformation resulted in the formation of 3D, [Zn2(rctt-ppcb)(tdc)2] (3), and 2D, [Zn2(spy)2(rctt-ppcb)(tdc)2] (4) (where rctt = regio, cis, trans, trans; ppcb = 1,3-bis(4'-pyridyl)-2,4-bis(phenyl)cyclobutane), respectively. These solid-state structural transformations were observed as an interesting post-synthetic modification. Overall, we successfully transformed novel lower-dimensional frameworks into higher-dimensional materials using a solid-state [2 + 2] photocycloaddition reaction.

Study of strong O[sbnd]H⋯O− hydrogen bond interactions in binuclear Zn hydroxyquinoline carboxylic acid complex

Investigation of strong hydrogen bonds in crystal engineering is extensively used for the preparation of intriguing novel pharmaceutical co-crystals and ionic compounds. Strong OH⋯O− hydrogen bonds in phenolates were recently recognized as a promising supramolecular synthon for the preparation of novel ionic co-crystals, and phenolates as promising catalysts and reducing agents. Investigations of complex compounds containing uncoordinated phenolate are exceptionally rare and this particular research area is yet unexplored. As part of our continuous investigations in the supramolecular chemistry of coordination compounds, we have prepared a novel Zn(II) binuclear complex with 4-hydroxyquinoline-2-carboxylic acid as a ligand (4hqc). The compound was characterized by IR-spectroscopy, and molecular and crystal structure was determined by the single-crystal X-ray diffraction method. The compound is a binuclear Zn complex, with each Zn(II) ion coordinated by one 4hqc ligand and two water molecules in the distorted square pyramidal arrangement. The central Zn2(µ-O)2 unit is planar and Zn ions are bridged by monodentatelly coordinated carboxylate oxygen atoms. In the crystal, the discrete binuclear units are primarily connected by strong OH⋯O− hydrogen bond interactions that involve deprotonated hydroxyl oxygen atoms and coordinated water molecules. The 3D structure is additionally stabilized by offset face-to-face π⋯π interactions. Additional structural analysis has shown that geometrical parameters of OH⋯O− hydrogen bonds are very similar to those in phenolate co-crystals, thus confirming the presence of phenolate in the complex. The calculated lattice energy of the compound was found to be unusually high (-505.56 kJ/mol), and OH⋯O− bond energies were estimated to be in the range from −55.0 kJ/mol to −62.5 kJ/mol. By comparison to previously reported phenolate coordination compounds, it was proposed that such compounds could be synthesized in mildly alkaline conditions, ligand: metal stoichiometric ratio 1:1, and with ligands bearing carboxylate, imine, or pyridine groups separated from phenol group by hydrogen atom or other bulkier groups.

Crystal structure and Hirshfeld surface analysis of bis-(μ-4-tert-but-oxy-4-oxobut-2-en-2-olato)bis-[(4-tert-but-oxy-4-oxobut-2-en-2-olato)ethano-lzinc(II)

The mol-ecular and crystal structure of the title binuclear Zn2+ complex, [Zn2(C8H13O3)4(C2H5OH)2], with enolated anionic tert-butyl-aceto-acetate and ethanol was analysed. The coordination polyhedra of the Zn atoms are distorted octa-hedra formed by six oxygen atoms that belong to three ligand mol-ecules and a coordinated ethanol mol-ecule. In the crystal phase, alternating layers can be distinguished parallel to the ac plane. A Hirshfeld surface analysis showed that there are no strong inter-molecular inter-actions in the structure. The most significant contributions to the overall crystal packing are from H⋯H inter-molecular contacts.

Synthesis and characterization of novel binuclear zinc complex, immobilization in nano-porous support, and its catalytic application

Binuclear zinc complex, [Zn2(L)(I)2(CH3CN)] (I) (LH2 = 1,2-phenylenebis(azaneylylidene))bis(methaneylylidene))bis(2-methoxyphenol)) was prepared and single-crystal X-ray diffraction was used to establish the structure of complex assembly. Organic acid and base were used to functionalize the nano-porous material and then binuclear Zn complex was grafted into the modified materials. Brunauer-Emmett-Teller isotherm (BET), Nuclear Magnetic Resonance (NMR), Inductively Coupled Plasma analysis (ICP), X-ray Diffraction (XRD), Fourier transform infrared spectra (FT-IR), thermogravimetric analysis (TG), Scanning electron microscope (SEM), etc., were used to characterized the synthesized nano-catalysts to check for existence of guest moiety, structural stability of the parent and modified catalysts. Catalytic performance was noticeably enhanced post modification; without catalyst, acid/base functionalized, Zn2 immobilized catalyst. Binuclear zinc immobilized on acid/base silica catalyst exhibited a maximum 95%, 89% conversion of piperidine, and 87% and 86% conversion of aniline respectively. Prior to the theoretical investigation the bond parameters of the binuclear zinc complex were measured experimentally. Time-dependent Density Functional Theory (TD-DFT) and Density Functional Theory (DFT) methods were used to calculate the molecule's UV–Vis absorption spectra at B3LYP as well as LANL2DZ and 6–31G(d)). LUMOs and HOMOs energy gap were determined from the electronic transitions to determine electrophilicity index (ω), softness (S), electronegativity (χ), hardness value (Ƞ), and chemical potential (μ), etc.

Synthesis, Crystal Structure, Hirschfeld Surface Analysis and Catalytic Activity of a New Binuclear Zn(II) Complex Based on Homophthalic Acid and 2,2'-Bipyridine Ligands

A new binuclear Zn(II) complex, [Zn2L2(BIPY)2(H2O)2](1) (H2L = homophthalic acid, BIPY = 2,2'-bipyridine) has been synthesized by one-pot method of homophthalic acid, 2,2'-bipyridine, zinc acetate dihydrate, and NaOH in water/ethanol (v:v = 1:1) solution. The structure of complex (1) was characterized by IR and X-ray single-crystal diffraction analysis. The results show that each Zn(II) ion is five-coordinated with two carboxylic O atoms from two homophthalate ligands (O2, O3 or O2a, O3a), two N atoms from two 2,2'-bipyridine ligands (N1, N2 or N1a, N2a) and one O atom from coordinated water molecule (O5 or O5a), and forms a distorted trigonal bipyramid coordination geometry. Complex (1) forms 1D chained structure and 3D network structure by the p-p interaction of 2,2'-bipyridine ligands. The Hirschfeld surface analysis of complex (1) was calculated. The catalytic performance of complex (1) has also been investigated for the oxidation of benzyl alcohol under O2 atmosphere. The optimal reaction temperature and pressure were 100 °C and 0.3 MPa for complex (1). Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Antibacterial properties of binuclear Zn(II)-azomethine complexes derived from diaminodiphenylsulphide bridged spacer

Antimicrobial resistance of microbes against treatment that once could cure, has inspired an urgent need for new drugs development. Accordingly, three binuclear Zn(II)-Schiff bases complexes ZnLa - ZnLc were prepared by direct reaction of the ligands La-Lc with Zn(II) ions in equimolar ratios bearing salicyldehydes with OH, NO2 and Cl functional groups. The synthesized compounds ZnLa - ZnLc were evaulated against Gram positive (Enterococcus faecalis NCIMB 13280, Streptococcus mutant ATCC 25175™ and Staphylococcus aureus ATCC 6538™) and gram negative (Escheria coli NCTC 12900, Salmonella typhi and Pseudomonas aeruginosa ATCC 15442) bacterial strains, respectively, by agar well diffusion and broth microdilution techniques. The minimum inhibitory concentration (MIC90) values were calculated by microplate reader at 550 nm to optimum result. It was found that all the synthesized compounds showed promising antibacterial activity against the genus Streptococcus mutant followed Staphylococcus aureus and Escheria coli. Binuclear Zn(II) complexes had a superior antibacterial activity compared to their parent Schiff base ligands. In general, 3,4-dihydroxy derived Schiff bases alongwith their relevant complexes exhibited magnificent antibacterial activity and hence merits to be established as promising keystone for subsequent antimicrobial drug advancement.

Construction of a photoluminescent Zn(II)-based 2D MOF via in situ cis-trans isomerization of cis,cis-muconate ligand

A Zn(II) based two-dimensional (2D) metal-organic framework (MOF) [Zn3(cis,trans-muco)3(4,4′-bpy)3]·4H2O (1) has been synthesized by slow diffusion method using cis,cis-muconic acid (H2cis,cis-muco) and 4,4′-bipyridine (4,4′-bpy) mixed ligands. The synthesized compound 1 has been structurally characterized by single crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD) techniques, and thermogravimetric analysis (TGA). The solid-state structure of 1 reveals in situ cis,cis- to cis, trans- isomerization of muconate ligand under visible light, which predominately coordinates to Zn(II). The compound 1 comprises binuclear Zn2 secondary building units (SBUs) which propagate in ab plane to furnish 2D framework with (4,4) net topology. Interestingly, compound 1 shows photoluminescence property and can be used as luminescent probe. The non-covalent interactions within the compound 1 have been investigated by means of Hirshfeld surface analysis.

0D + 1D = 1D Zn-orotate-Bimb polyrotaxane coordination polymer: Synthesis, structure, thermogravimetric and variable temperature luminescence analysis

A new polyrotaxane coordination polymer {[Zn(Or)(Bimb)(H2O)]2·6H2O}n(1) has been synthesized using Zn(II) ion with 1,4-bis[(1H-imidazol-1-yl)methyl]benzene) (Bimb) and potassium orotate (OrK) ligands at ambient temperature. Single-crystal X-ray diffraction, elemental analysis, variable temperature Powder X-ray diffraction (VT-PXRD), variable temperature FTIR (VT-FTIR) and TG/DT/TDG were used to characterize the complex. Complex (1) contains 0D binuclear Zn(1)–based molecular “loop”, 1D Zn(2)–based molecular “string” yielding to 0D + 1D = 1D polyrotaxane coordination polymers. Supramolecular network in complex (1) is stabilized by classical strong NH∙∙∙O and OH∙∙∙O hydrogen bonds resulting in the formation of 2D inter-layer polyrotaxane coordination polymers and 3D supramolecular network via these non-covalent interactions. The solid-state variable temperature-luminescence studies of as synthesized and heated forms of (1) emit strong luminescence in the range of 363–439 nm (2.82–3.41 eV) with slight contrast in physical façade. The thermal breakdown of (1) yielded spherical shaped ZnO nanoparticles with diameters of ̴ 32 nm, as confirmed by FESEM, EDAX.

Zn2+-Schiff’s Base Complex as an “On–Off-On” Molecular Switch and a Fluorescence Probe for Cu2+ and Ag+ Ions

The present study presents a thorough theoretical analysis of the electronic structure and conformational preference of Schiff's base ligand N,N-bis(2-hydroxybenzilidene)-2,4,6-trimethyl benzene-1,3-diamine (H2L) and its metal complexes with Zn2+, Cu2+ and Ag+ ions. This study aims to investigate the behavior of H2L and the binuclear Zn2+ complex (1) as fluorescent probes for the detection of metal ions (Zn2+, Cu2+ and Ag+) using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The six conformers of the H2L ligand were optimized using the B3LYP/6-311 + + G** level of theory, while the L-2-metal complexes were optimized by applying the B3LYP functional with the LANL2DZ/6-311 + + G** mixed basis set. The gas-phase and solvated Enol-cis isomer (E-cis) was found to be the most stable species. The absorption spectra of the E-cis isomer and its metal complexes were simulated using B3LYP, CAM-B3LYP, M06-2X and ωB97X functionals with a 6-311 + + G** basis set for C, O, N and H atoms and a LANL2DZ basis set for the metal ions (Zn2+, Cu2+ and Ag+). The computational results of the B3LYP functional were in excellent agreement with the experimental results. Hence, it was adopted for performing the emission calculations. The results indicated that metal complex (1) can act as a fluorescent chemosensor for the detection of Ag+ and Cu2+ ions through the mechanism of intermolecular charge transfer (ICT) and as a molecular switch "On-Off-On" via the replacement of Cu2+ by Ag+ ions, as proved experimentally.

Synthesis and Crystal Structure of New Zn(II) Complex with N-[bis(benzylamino)phosphoryl]-2,2,2-trichloroacetamide

The novel binuclear Zn(II) complex of general formula Zn2(L)4(CH3OH)2 where HL is N-[bis(benzylamino)phosphoryl]-2,2,2-trichloroacetamide has been synthesized from non-aqueous solution and characterized by elemental analysis, FTIR and NMR spectroscopy as well by X-ray single crystal diffraction. This complex represents the third example of binuclear complexes with this ligand within four known for today.

Binuclear Zn(II) Schiff base complexes: Synthesis, spectral characterization, theoretical studies and antimicrobial investigations

Binuclear zinc(II) Schiff base complexes were synthesized through the reaction of ONNO tetradentate Schiff base ligands derived from the condensation of 2,2-dimethyl-1,3-propanediamine and 5-chlorosalicylaldehyde or 5-bromosalicylaldehyde with zinc acetylacetonate salt. The structures of synthesized products were explored spectroscopically through the FT-IR, 1H NMR and elemental analysis. Structural analysis of the complexes revealed that the compound is a centrosymmetric dimer in which the five coordinated Zn(II) atoms are linked to the opposite metal center by making μ-phenoxo bridges through one of the phenolic oxygen atoms of Schiff base ligands. The nature and types of non-covalent interactions present among the sample molecules were also investigated by using the quantum theory of atoms in molecules and non-covalent interactions calculations. The theoretical calculations, performed by density functional theory using the B3LYP/Def2-TZVP level of theory, direct that the intended outcomes are in compliance with the actual consequences. Furthermore, from antimicrobial screenings it was revealed that the zinc complexes are more active as compared to the ligands.

Piperidine based effective chemosensor for Zn(II) with the formation of binuclear Zn complex having specific Al(III) detection ability in aqueous medium and live cell images

A schiff base chemosensor HL [4-chloro-(((2-(piperidine-1-yl)imino)methyl)phenol], constructed by one step condensation of 2-aminoethyl piperidine and 5- Chloro Salicylaldehyde is illustrated to have its usefulness for selective and sensitive detection of Zn(II) among other metal ions in aqueous solution (HEPES buffer) displaying the colour changes from light blue to turquoise under UV light. The specific detection phenomena of Zn (II) is monitored by the remarkable fluorescence enhancement and notable change in NMR spectral data of fluorescence active HL after addition of Zn(II) to it. The impressive high binding constant in 106 orders, determined by electronic spectral titration after introduction of Zn(II) to HL assure the formation of a Zinc complex during sensing phenomena. In order to check whether the nuclearity of the constructed complex can be increased or not fluorescence enhancement phenomenon is further monitored in presence of different bridging ligands and the results display that only in presence of azide a significant enhancement of Zn(II)-HL domain is exposed where as for other bridging ligand the spectra remain unaltered. This observation insists to conduct the reaction between HL and ZnCl2 in presence of sodium azide which lead the formation of a Zn complex [Zn2(HL)2(N3)4] (complex 1) employing azide as the secondary anionic residue instead of bridging. The single crystal structure of the complex unveils the unique protonation of the piperidine N during the crystallization of the dinuclear motif of the complex 1. Furthermore the Zn complex due to the presence of remarkable luminescence property have been effectively used for selective sensing of Al(III) ion as metalloreceptor in HEPES buffer solution via turn of fluorescence with remarkable fluorescence quenching constant. In aqueous solution, complex 1 induces a 1:2 complex formation with Al(III) ion indicated by Job’s plot analysis. The DFT study suggests the formation of bimetal complex during sensing of Al(III) with complex 1 as metalloreceptor. The in vitro cell imaging study gives a authentic hints for in vivo biomedical application of HL as a selective and easy Zn(II) sensor. The two step sensing phenomena of HL and complex 1 is further established by advanced molecular logic gate formation.

Three coordination polymers built by quaternary-ammonium-modified isophthalic acid.

Three coordination polymers based on quaternary-ammonium-modified isophthalic acid, namely, catena-poly[[[aqua-μ2-bromido-di-μ3-hydroxido-methanoldinitratotetracopper(II)]-bis{μ4-5-[2-(tripropylazaniumyl)ethoxy]benzene-1,3-dicarboxylato}] nitrate], {[Cu4Br(C19H28NO5)2(NO3)2(OH)2(CH4O)(H2O)]NO3}n, 1, poly[μ3-bromido-μ2-bromido-bromido-μ3-hydroxido-{μ4-5-[2-(tripropylazaniumyl)ethoxy]benzene-1,3-dicarboxylato}tricopper(II)], [Cu3Br3(C19H28NO5)(OH)]n, 2, and poly[bromido{μ3-5-[2-(tripropylazaniumyl)ethoxy]benzene-1,3-dicarboxylato}zinc(II)], [ZnBr(C19H28NO5)]n, 3, were obtained by solvothermal reactions. Coordination polymer (CP) 1 contains tetranuclear Cu4 units, in which the four Cu atoms are linked by two μ3-OH- groups into a Cu4(OH)2 cluster, which are in turn linked by 5-[2-(tripropylazaniumyl)ethoxy]benzene-1,3-dicarboxylate (cpa-) ligands into a chain structure. CP 2 also contains a tetranuclear Cu4(OH)2 cluster and these are linked with CuBr3 units into chains. The chains are then connected by cpa- ligands into a two-dimensional layered structure. CP 3 contains a two-dimensional layer structure built by binuclear Zn2 units and cpa- ligands. The Br- counter-anions of the quaternary ammonium groups all take part in the construction of the polymeric networks.

High-Throughput Electron Diffraction Reveals a Hidden Novel Metal-Organic Framework for Electrocatalysis.

Metal‐organic frameworks (MOFs) are known for their versatile combination of inorganic building units and organic linkers, which offers immense opportunities in a wide range of applications. However, many MOFs are typically synthesized as multiphasic polycrystalline powders, which are challenging for studies by X‐ray diffraction. Therefore, developing new structural characterization techniques is highly desired in order to accelerate discoveries of new materials. Here, we report a high‐throughput approach for structural analysis of MOF nano‐ and sub‐microcrystals by three‐dimensional electron diffraction (3DED). A new zeolitic‐imidazolate framework (ZIF), denoted ZIF‐EC1, was first discovered in a trace amount during the study of a known ZIF‐CO3‐1 material by 3DED. The structures of both ZIFs were solved and refined using 3DED data. ZIF‐EC1 has a dense 3D framework structure, which is built by linking mono‐ and bi‐nuclear Zn clusters and 2‐methylimidazolates (mIm−). With a composition of Zn3(mIm)5(OH), ZIF‐EC1 exhibits high N and Zn densities. We show that the N‐doped carbon material derived from ZIF‐EC1 is a promising electrocatalyst for oxygen reduction reaction (ORR). The discovery of this new MOF and its conversion to an efficient electrocatalyst highlights the power of 3DED in developing new materials and their applications.

Nano metal complexes in cancer therapy, preparation, spectroscopic, characterization and anti-breast cancer activity of new metal complexes of alanine Schiff-base.

There are many properties of metal ions that were useful for solving basic problems in medicine, metal complexes with particular properties can be covalently affected to biological macromolecules. Mono Co(II), Ni(II) ,Cu(II) ,Zn(II) ,Mg(II) and binuclear Zn(II)/Cu(II) and Ni(II)/Cu(II) complexes of new Schiff-base derived from alanine amino acid ester have been synthesized and characterized. They were studied using elemental and spectral analysis such as IR,UV-VIS,1H-NMR mass spectroscopy as well as conductivity, magnetism, thermal analysis (DTA and TGA), electron microscope and ESR measurements. Conductance measurements of metal complexes indicated non electrolytic in nature. Elemental and spectral analysis confirmed distorted octahedral structural for all complexes. ESR spectra of complexes showed anisotropic or isotropic spectra with covalent bond character. Electron microscope data showed that, complexes with high biological activity were found in Nano form. The ligand and some of its complexes were studied against breast cancer (in vitro) and exhibited moderate to high activity compared to standard drug (doxorubicin). The order of activity was (doxorubicin)= ligand (1) > Ni(II)/Cu(II) complex (19) > Zn(II)/Cu(II) complex (20) > Zn(II) complex (18).

Functional Characterization of Primordial Protein Repair Enzyme M38 Metallo-Peptidase From Fervidobacterium islandicum AW-1.

The NA23_RS08100 gene of Fervidobacterium islandicum AW-1 encodes a keratin-degrading β-aspartyl peptidase (FiBAP) that is highly expressed under starvation conditions. Herein, we expressed the gene in Escherichia coli, purified the recombinant enzyme to homogeneity, and investigated its function. The 318 kDa recombinant FiBAP enzyme exhibited maximal activity at 80°C and pH 7.0 in the presence of Zn2+. Size-exclusion chromatography revealed that the native enzyme is an octamer comprising a tetramer of dimers; this was further supported by determination of its crystal structure at 2.6 Å resolution. Consistently, the structure of FiBAP revealed three additional salt bridges in each dimer, involving 12 ionic interactions that might contribute to its high thermostability. In addition, the co-crystal structure containing the substrate analog N-carbobenzoxy-β-Asp-Leu at 2.7 Å resolution revealed binuclear Zn2+-mediated substrate binding, suggesting that FiBAP is a hyperthermophilic type-I IadA, in accordance with sequence-based phylogenetic analysis. Indeed, complementation of a Leu auxotrophic E. coli mutant strain (ΔiadA and ΔleuB) with FiBAP enabled the mutant strain to grow on isoAsp-Leu peptides. Remarkably, LC-MS/MS analysis of soluble keratin hydrolysates revealed that FiBAP not only cleaves the C-terminus of isoAsp residues but also has a relatively broad substrate specificity toward α-peptide bonds. Moreover, heat shock-induced protein aggregates retarded bacterial growth, but expression of BAP alleviated the growth defect by degrading damaged proteins. Taken together, these results suggest that the viability of hyperthermophiles under stressful conditions may rely on the activity of BAP within cellular protein repair systems.