Coordinate Covalent Research Articles

Controlling Magnetic Anisotropy in a Zero-Dimensional S = 1 Magnet Using Isotropic Cation Substitution.

The [Zn1–xNix(HF2)(pyz)2]SbF6 (x = 0.2; pyz = pyrazine) solid solution exhibits a zero-field splitting (D) that is 22% larger [D = 16.2(2) K (11.3(2) cm–1)] than that observed in the x = 1 material [D = 13.3(1) K (9.2(1) cm–1)]. The substantial change in D is accomplished by an anisotropic lattice expansion in the MN4 (M = Zn or Ni) plane, wherein the increased concentration of isotropic Zn(II) ions induces a nonlinear variation in M-F and M-N bond lengths. In this, we exploit the relative donor atom hardness, where M-F and M-N form strong ionic and weak coordinate covalent bonds, respectively, the latter being more sensitive to substitution of Ni by the slightly larger Zn(II) ion. In this way, we are able to tune the single-ion anisotropy of a magnetic lattice site by Zn-substitution on nearby sites. This effect has possible applications in the field of single-ion magnets and the design of other molecule-based magnetic systems.

Recent advances in membrane hydrophilic modification with plant polyphenol‐inspired coatings for enhanced oily emulsion separation

AbstractOily wastewater, especially the emulsified one, causes serious environment pollution and poses threats to the ecosystem and resource recycling. Among various filtration media, porous polymeric membranes have gained tremendous attention in dealing with oily emulsions due to their energy‐saving, cost‐effective, and highly efficient features. However, to alleviate membrane fouling by oil droplets and ensure high separation efficiency, endowing membrane with superhydrophilicity and underwater superoleophobicity via facile strategy is highly desired. Taking advantages of the mild forming conditions, universality and cost‐efficiency, more and more efforts have been devoted to membrane hydrophilic modification by plant polyphenol‐inspired coatings in recent years. In this review, we focus on recent advances in constructing plant polyphenol‐involved coatings on membrane surface for oil‐in‐water emulsion separation. The interactions between plant polyphenol and functional materials including amino‐functionalized materials, transition metal ions and oxidants via covalent chemistry, coordination chemistry, and rapid oxidation are highlighted. In addition, the impacts of the resultant coating on the wettability, oily emulsion separation performance, and anti‐oil fouling performance of the modified membrane are systematically summarized. Finally, future outlooks in membrane surface engineering with plant polyphenol‐involved coatings are discussed to further broaden the research related to high‐efficiency oil/water separation based on membrane technology.

Chemical functionalization of 2D black phosphorus

AbstractAs an emerging two‐dimensional material, black phosphorus (BP) has fascinating structure and electronic properties, affording broad applications in field‐effect transistors, optoelectronic devices, energy devices, and biomedicines. However, the lone pair electrons of phosphorus atoms readily react with oxygen, so few‐layer BP is easily oxidized and degraded when exposed to air. Therefore, the ambient stability of BP needs to be enhanced for its potential application. Chemical functionalization is one of the most effective methods for improving the ambient stability of few‐layer BP. In this review, we provide a comprehensive overview of the chemical functionalization of BP, focusing on covalent and noncovalent functionalization and surface coordination. The influence of the functionalization pattern on the electronic properties and ambient stability of BP is summarized. Finally, the challenges and future development of chemical functionalization of BP are discussed.image

A Facile Synthesis of HKUST-1 MOF through Reductive Electrosynthesis Method

Metal-organic frameworks (MOFs) are porous crystalline materials that consist of metal ions bind to organic ligands as linkers by coordination covalent bonds. MOF properties, such as the presence of open metal sites, large surface area, high porosity, high thermal stability, tunable structure, and feasibility in modification are controlled and determined by metal cations, organic linkers, and applied synthetic method. Reductive electrosynthesis is a popular and interesting MOF synthetic method on the surface of conductive substrates. This method is based on electroreduction of oxoanions to generate hydroxide anions that lead to selective deposition of MOFs on conductive surfaces to form a thin MOFs film. The applied potentials during electrosynthesis affect the properties and applications of the produced MOFs. Here, Cu-based MOFs with the type of CuBTC (H3BTC: 1,3,5-benzenetricarboxylic acid) known as HKUST-1 films were synthesized using different cathodic potentials and time, at room temperature, on the surface of brass. The reductive electrosynthesis was found to be fast and mild for preparing HKUST-1. This method allows direct surface modification which in turn affect the HKUST-1 applications as electrode material for electrochemical sensing such as glucose.

A quest for stable bicyclic carbenes with one, two, and three carbenic centers at theoretical level

We have scrutinized eighteen new derivatives of carbenes with one, two, and three carbenic centers and compared their structural and thermodynamic parameters, at B3LYP/6-311++G** level of theory. All novel carbene scrutinized show singlet ground stat, and the highest stability belongs to 1,2,3,4-tetraazabicyclo[1.1.1]-5-pentanylene (9) (ΔEs-t = 47.95 kcal/mol). This stability can be related to their σ−bond and intermolecular interactions. This bond arose from a tendency of nonbonding electrons of nitrogen (N(E or G)) to empty p orbital of the carbenic center. In addition, carbene 16s and 17s because of three coordinate covalent bonds with their carbenic centers have low nucleophilicity (N). The increase in band gaps (ΔEHOMO–LUMO) is correlated with an increase in ΔEs–t values. The purpose of the present work was to assess the influence of 1 to 4 nitrogen substituents on the stability (ΔEs-t), ΔEHOMO–LUMO, N, electrophilicity (ω), and isodesmic reactions. Finally, our investigation introduces novel carbenes that can be applied as cumulated multi-dentate ligands.

Zwitterionic and hydrophilic polyelectrolyte/metal ion anti-fouling layersviacovalent and coordination bonds for reverse osmosis membranes

A durable PEI/PASP/Fe coated reverse osmosis membrane was fabricatedviathe dual action of covalent bonds and coordination bonds, which shows excellent long-term desalination and anti-fouling property.

A novel photothermal, self-healing and anti-reflection water evaporation membrane.

For the solar water evaporation system, there are no reports on the self-healing support, which is crucial for the sustainable use of solar evaporation membrane. In this work, a self-healing hydrogel is prepared via free radical copolymerization with covalent cross-linking and coordination cross-linking and is used as a photothermal water evaporation support. The photothermal material is then introduced into the hydrogel by physically doping acetylene carbon black. At the same time, inverted micro-pyramids are fabricated on the surface of the hydrogel by soft imprint to increase the utilization efficiency of incident light. The water evaporation rate of the composite membrane can reach 1.58 kg m-2 h-1, and the breaking elongation is 1580%. It can self-heal after it is completely broken, and can still be stretched 3 times its original length. The design of this self-healing photothermal membrane will provide a new idea for its application in a harsh outdoor environment.

Electronic structure study of divanadium complexes with rigid covalent coordination: potential molecular qubits with slow spin relaxation.

The electronic structures of homovalent [V2(μ-S2)2(R2dtc)4] (R = Et, iBu) and mixed-valent [V2(μ-S2)2(R2dtc)4]+ are reported here. The soft-donor, eight-coordinate ligand shell combined with the fully delocalised ground state provides a highly rigid and covalent environment that will nurture long spin relaxation times in vanadyl-based molecular qubits.

Chromium-based covalent coordination nano-polymer: a promising dye elimination compound for water purification

Chromium-based covalent coordination nano-polymer: a promising dye elimination compound for water purification

Immobilization of alpha-L-rhamnosidase on a magnetic metal-organic framework to effectively improve its reusability in the hydrolysis of rutin

α-L-Rhamnosidase (Rha) is a biotechnologically important enzyme that degrades biomass containing natural rhamnoside. Herein, the recombinant Rha was successfully immobilized on magnetic metal-organic frameworks (MOFs), and used to hydrolyze rutin. Magnetic MOFs were constructed by binding Cu2+ and PABA to the surface of Fe3O4 nanoparticles coated with a polydopamine film through coordinate covalent bonds, and the enzyme was attached to the MOFs using the cross-linking agents EDC/NHS. The immobilized enzyme Rha@MOF reached an activity of 25.09 U/g with a lower apparent Km value compared with the free enzyme. The conversion rate of 20 g/L rutin was 91.42%, corresponding to an isoquercitrin productivity of 12.78 g/L/h. Rha@MOF also exhibited significantly improved reusability; the conversion rate was still 73.55% after 30 cycles at 60 °C. These results indicated that the magnetic MOF-immobilized enzyme was a feasible biocatalyst for the conversion of flavonoids with low aqueous solubility.

Unique 2-methylimidazole based Inorganic Building Brick nano-particles (NPs) functionalized with 3-aminopropyltriethoxysilane with excellent controlled corrosion inhibitors delivery performance; Experimental coupled with molecular/DFT-D simulations

Metal organic frameworks (MOFs) are unique organic-inorganic-based nanomaterials with highly porous structures that can be obtained through the metal ions (as a center) linking to the organic ligands via covalent bond coordination. Despite different applications, i.e., sensing, molecular sieves, and drug delivery, the anti-corrosion properties of the MOFs is an issue that remains rarely reported. ZIF-67, which can be constructed via cobalt ions (Co2+) coordination with 2-methylimidazole ligands, is a new type of MOFs for unique performance i.e., in catalysis/gas adsorption applications. In this study, for the first time, the ZIF-67 NPs were synthesized and modified by 3-aminopropyltriethoxysilane (APS) to control its solubility in water. The field emission scanning electron microscopes (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), ultraviolet-visible spectroscopy (UV–vis), and low-angle X-ray diffraction analysis (XRD) tests were used to investigate the structures of the NPs. Also, the dispersion stability of ZIF-67 and ZIF-67@APS NPs were studied in different solvents at different times. The ZIF-67 and ZIF-67@APS NPs corrosion retardation activities were evaluated in the aquatic simulated seawater solution (NaCl-3.5 wt.%) on the bare steel samples by FE-SEM, grazing incidence X-ray diffraction (GIXRD), and electrochemical techniques. Besides, the theoretical (QM, MC/MD) computations supported the adsorption of ZIF-67 compounds on the metal-based adsorbent. The results showed that the ZIF-67 NPs synthesis and modification were done successfully. Also, the modification of ZIF-67 led to the improvement of its thermal stability and reduction of hydrophilicity. Tafel (potentiodynamic) polarization test demonstrated that in the ZIF-67@APS NPs containing NaCl-based extract, the metal corrosion was diminished by a high inhibition degree of 81% through mixed anodic (Fe oxidation to Fe2+) and cathodic (O2 reduction to OH−) reactions retardation mechanisms. EIS test showed that there is an ascending trend for the values of log |Z|10 mHz in the Bode module plots of ZIF-67 and ZIF-67@APS samples until 24 h and the log |Z|10 mHz values of the sample immersed in ZIF-67@APS solution over immersion time were more than the impedance values of the samples immersed in ZIF-67 and blank solutions.

Photoelectric properties of Sr2MgSi2O7: Eu2+ phosphors produced by co-precipitation method

Eu2+-doped phosphors Sr2MgSi2O7: xEu2+ (x = 1–5 mol%) with blue color are synthesized by the co-precipitation method. The X-ray diffraction patterns of these phosphors indicate a tetragonal crystal structure. The emission peak centered at 486 nm is attributed to the 4 F7→ 4F65D1 transitions of Eu2+ ions with CIE coordinates of (x = 0.176, y = 0.637). We use Sr2MgSi2O7: 4 mol% Eu2+ phosphors to find latent fingerprints (LFPs) with visible patterns on different surfaces under 337 nm UV light. The results indicate that this phosphor may possess the potential to be used for LFP recognition. Three calculated models mimicking the crystal host, Eu2+ ion-doped phosphor, and Eu2+ ion-doped phosphor with oxygen vacancy are built using CASTEP software to perform density functional theory (DFT) calculations. The geometry optimization results of the Eu2+ doping ion reveal that a coordinate covalent bond is formed by the Eu2+ doping ion with its neighboring oxygen atoms. The oxygen vacancy VO causes obvious changes in the electron orbitals of Si and O atoms as well as the 5d empty orbital of Eu2+ ions.

(Invited) Liquid Phase Interfacial Assemblies of Porous Nanosheets with Controlled Orientation and Thickness

Development of rational methods for creating ordered two-dimensional (2D) structures with nanometer scale precision is one of the central issues in the nanoscience and nanotechnology fields because of their intrinsic physical-chemical properties which are seen in those of their equivalent bulk state. Inclusion of highly regulated nanopores into the nanosheet structure will further open the possible applications such as nanosieves, molecular/ion storage and sensor devices as well as introducing guest molecules into the nanopores tune variedly the sheet properties (electric conduction, nanoheterojunction). Utilizing molecular building units are suitable for creating such porous nanosheets because of rich variety of design and facile modification of size and shape. Furthermore, various chemical interactions such as covalent bond, coordination and hydrogen bond are applied for assembling molecular-based nanosheets.Here, I present a facile bottom-up synthesis of molecular nanosheets with both positional and size regulated nanopores utilizing air/liquid interfaces. By applying liquid interfaces, growth direction of the object can be well controlled with utilizing self-assembly feature of the molecules under mild conditions. We have succeeded to tune finely the nanosheet structures by rational modification of molecular building units [1-4]. In addition, new methodology we developed based on the liquid interface technique resulted in enlarging the nanosheet size. The highly crystalline structure remains after transferring a solid substrate from the liquid surface as well as without any supports. Notably, such highly oriented porous crystalline structure is obtained specifically by applying bottom up synthesis at air/liquid interfaces, not by other techniques such as drop cast [5]. Makiura, R. et al. Nature Mater. 9, 565 (2010).Motoyama, R. Makiura, O. Sakata, H. Kitagawa, J. Am. Chem. Soc. 133, 5640 (2011).Makiura, R., Konovalov, O. Rep. 3, 2506 (2013).Makiura, R. et al. ChemPlusChem. 79, 1352 (2014).Makiura, R. et al. ACS Nano, 11, 10875–10882 (2017). Figure 1

A theoretical investigation into novel germylenes: effects of nitrogen substitution on stability and multiplicity.

The effects of substituting nitrogen atoms on the stability of novel singlet (s) and triplet (t) forms of germylenes (1-20) are compared and contrasted, at B3LYP/AUG-cc-pVTZ level of theory. Every one of the 40 new divalents scrutinized appears as a minimum on its energy surface, for showing no negative force constant. Also, every singlet (1s-20s) appears more stable than its corresponding triplet (1t-20t). The highest stability (ΔEs-t) is achieved by germylene (11) where all the three nitrogens are bonded to the central boron atom. The EHOMO slightly decreases when the number of electronegative, σ-acceptor nitrogen atoms increases, and also causes it to be less electron-rich. Germylene 16s with low stability (ΔEs-t = 17.19kcal/mol), bond gap (ΔEHOMO-LUMO = 57.46kcal/mol-1), and atomic charge on -G̈e- (+ 0.9012), has high electrophilicity (ω = 3.78eV) and nucleophilicity (N = 3.87eV). Germylenes 8s, 14s, and 19s with coordinate covalent bond between nitrogen (N(Y)) and germylene center have low ω and high ΔEHOMO-LUMO. The purpose of the present work was, therefore, to assess the influence of nitrogen substituents on the stability (ΔΕs-t), band gaps (ΔΕHOMO-LUMO), N, ω, and heat of hydrogenation (ΔEH). This investigation is aimed to introduce novel germylenes that can be applied as cumulated multi-dentate NHG̈e ligands.

Dynamic Helicates Self-Assembly from Homo- and Heterotopic Dynamic Covalent Ligand Strands.

The understanding and the application of reversible covalent reactions and coordination chemistry together with the proper design of the molecular frameworks, allow to achieve not only well-defined output architectures but also different grades of complex behavior. In this work, the dynamic nature of the helical systems offers an additional level of complexity by combining self-sorting on two levels: 1) the build-up of the ligand strand constituents from their components through dynamic covalent chemistry; 2) the assembly of the helicates from the ligands and the metal cations through dynamic metallo-supramolecular chemistry. The information encoded in the ligands constituent molecule was read differently (and accurately at the same time) by metal cations that varied in the coordination algorithms. It enabled the selective formation of a specific type of helicates from a wide library of helicates formed by the possible combination of subcomponents. Ligands containing dynamic tridentate and/or bidentate binding motifs in the same strand were studied to explore the helicates self-assembly with appropriate metal cations.

Boronate Covalent and Hybrid Organic Frameworks Featuring PIII and P=O Lewis Base Sites.

Two covalent organic frameworks comprising Lewis basic PIII centers and Lewis acidic boron atoms were prepared by poly‐condensation reactions of newly obtained tris(4‐diisopropoxyborylphenyl)phosphine with 2,3,6,7,10,11‐hexahydroxytriphenylene and 2,3,6,7‐tetrahydroxy‐9,10‐dimethylanthracene. Obtained materials exhibit significant sorption of dihydrogen (100 cm3 g−1 at 1 bar at 77 K), methane (20 cm3 g−1 at 1 bar at 273 K) and carbon dioxide (50 cm3 g−1 at 1 bar at 273 K). They were exploited as solid‐state ligands for coordination of Pd0 centers. Alternatively, in a bottom‐up approach, boronated phosphine was treated with Pd2dba3 and poly‐condensated, yielding hybrid materials where the polymer networks are formed by means of covalent boronate linkages and coordination P−Pd bonds. In addition, the analogous materials based on phosphine oxide were synthesized. The DFT calculations on framework–guest interactions revealed that the behavior of adjacent boron and phosphorus/phosphine oxide centers is reminiscent of that found in Frustrated Lewis Pairs and may improve sorption of selected molecules.

Novel azaborastannylenes by DFT

We have reached novel borastannylenes with an unprecedented common frame work that can accommodate up to five nitrogen heteroatoms. All species appear as ground state minima on their energy surface, for showing no negative force constant. Singlets 7-boratricyclo[1.1.1.01,7.07,3.07,5]hexa-2-stannylenes (1s-20s) are ground states and more stable than their corresponding triplets (1t-20t). They are compared and contrasted with respect to their geometrical parameters, stability (ΔΕs-t), heat of hydrogenation (ΔEH), nucleophilicity (N), electrophilicity (ω), and isodesmic reactions at B3LYP/AUG-cc-pVTZ//B3LYP/6–311++G** level of theory. The highest stability belong to the singlet 1,3-diaza-7-boratricyclo[1.1.1.01,7.07,3.07,5]hexa-2-stannylene (5) which shows the highest value of ΔEs-t. Boracyclics singlet 1,4,6-triaza-7-boratricyclo[1.1.1.01,7.07,3.07,5]hexa-2-stannylene (14s) with coordinate covalent bond between nitrogen and stannylene center and 1,4,5,6-teraaza-7-boratricyclo[1.1.1.01,7.07,3.07,5]hexa-2-stannylene (18s) with high LPN → LP*Sn interactions have low ω. Also, the highest band gap (ΔΕHOMO–LUMO) belong to theirs. Our investigation introduces novel stannylene with possible applications in chemistry such as semiconductors, cumulated multi-dentate legends, etc.

Effects of nitrogen atoms on the stability and reactivity of tricyclic boracarbenes by DFT

Following our quest for novel carbenes, effects of substituting 1 to 5 nitrogen atoms on the stability and reactivity of singlet (s) and triplet (t) forms of 7-boratricyclo[1,1,1,01,7,07,3,07,5]hexa-2-carbylenes (1–20) are compared and contrasted, at B3LYP/aug-cc-pvtz level of theory. All species appear as ground state minima on their energy surface, for showing no negative force constant. Singlets (1s–20s) are ground states and more stable than their corresponding triplets (1t–20t). Reactivity of the species (1s–20s vs. 1t–20t) is discussed in terms of isodesmic reactions, considering nucleophilicity (N), electrophilicity (ω), and heat of hydrogenation. As well as, the addition of nitrogen atoms decreased nucleophilicity (N), while increasing electrophilicity (ω). Despite the enormous steric strain involved in their cubic structures, the most stable scrutinized carbenes appear to be singlet 1,4,5-triaza-7-boratricyclo[1,1,1,01,7,07,3,07,5]hexa-2-carbylene (13) for showing the highest value of ΔEs–t. Such higher stabilization is attributed to a coordinate covalent bond observed between the carbenic center and the boron atom. This study offers new insights into the chemistry of these exotic tricyclic shaped carbenes.

USING ONE OF ORGANIC EXTRACTS AS A CORROSION INHIBITOR FOR CARBON STEEL IN ACIDIC ENVIRONMENT

Utilization of mangosteen rind extract as carbon steel inhibitors in the environment of hydrochloric acid (HCl) 0.1M, 0.5M, and 1.0M. Extracts were carried out by extraction using ethanol solvent at a temperature of 600C with a time of 80 minutes. The variation of extract concentration (100 ppm to 1000 ppm in 3 days and the effect of time of corroding the carbon steel with the addition of 1000 ppm extract. Corrosion rate is calculated based on the difference in weight and corrosion products shown by microscope optics. The objective was investigated corrosion inhibition efficiency that could be prevented by mangosteen peel extract as inhibitor. The results showed inhibitory properties of mangosteen peel extract for three (3) days increased with increasing extract concentrations up to 76.53% in 0.1M HCl solution and 28.83% in 1.0M HCl solutions. For the addition of 1000 ppm mangosteen peel extract showed inhibitor efficiency reached about 90% at 3 days of corrosive time in HCl 0, 5 M, 87% in 1.0 M HCl solution, and 81% in 0.1 M HCl solution. The experiment showed that the process of diffusion of compounds in extracts on the surface of carbon steel and react with ferro ions (Fe2 +) to form chemical covalent coordination coordinate with a thickness of 76 µm was successfully done.

Shifting the Specificity of E. coli Biosensor from Inorganic Arsenic to Phenylarsine Oxide through Genetic Engineering

It has recently been discovered that organic and inorganic arsenics could be detrimental to human health. Although organic arsenic is less toxic than inorganic arsenic, it could form inorganic arsenic through chemical and biological processes in environmental systems. In this regard, the availability of tools for detecting organic arsenic species would be beneficial. Because As-sensing biosensors employing arsenic responsive genetic systems are regulated by ArsR which detects arsenics, the target selectivity of biosensors could be obtained by modulating the selectivity of ArsR. In this study, we demonstrated a shift in the specificity of E. coli cell-based biosensors from the detection of inorganic arsenic to that of organic arsenic, specifically phenylarsine oxide (PAO), through the genetic engineering of ArsR. By modulating the number and location of cysteines forming coordinate covalent bonds with arsenic species, an E. coli cell-based biosensor that was specific to PAO was obtained. Despite its restriction to PAO at the moment, it offers invaluable evidence of the potential to generate new biosensors for sensing organic arsenic species through the genetic engineering of ArsR.