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The measurement of ultra-trace level of heavy metals in complex metrics is of great concern and challenge in life and environmental science. Herein, a novel thiol-functionalized covalent organic framework (COF) was prepared and achieved quantitative preconcentration of trace heavy metals in environmental water samples. The material was synthetized by two-step reactions, including a Schiff base reaction between 1,3,5-triformylphloroglucinol (Tp) and 2,5-divinyl-p-phenylenediamine (DvPa) to form preliminary COF (TpDvPa), and a thiol-ene “click” reaction between 1,2-ethanedithiol and the vinyl groups of TpDvPa to produce thiol-functionalized TpDvPa (TpDvPa-S-SH). By packing the material into a home-made SPE micro-column, and hyphenating the micro-column with inductively coupled plasma mass spectrometry (ICP-MS), trace level of Co2+, Ni2+ and Cd2+ in environmental waters could be successfully preconcentrated and measured, with LODs of 1.46, 1.38 and 0.10 ng L-1, respectively. The precisions were all less than 2.7%，with linear ranges extended from 5 to 1000 ng L-1. The proposed method was validated by the analysis of the certificated reference material (GBW08608), and measurement of Co2+, Ni2+ and Cd2+ in tap water, reservoir water, effluent of wastewater treatment plant and sea water, confirming the accuracy and feasibility of the method.

Two-dimensional covalent organic frameworks (2D-COFs), also referred to as 2D polymer networks, display unusual electronic-structure characteristics, which can significantly enrich and broaden the fields of electronics and spintronics. In this Focus article, our objective is to lay the groundwork for the conceptual description of the fundamental relationships among the COF electronic structures, the symmetries of their 2D lattices, and the frontier molecular orbitals (MOs) of their core and linker components. We focus on monolayers of hexagonal COFs and use tight-binding model analyses to highlight the critical role of the frontier-MO symmetry, in addition to lattice symmetry, in determining the nature of the electronic bands near the Fermi level. We rationalize the intriguing feature that, when the core unit has degenerate highest occupied MOs [or lowest unoccupied MOs], the COF highest valence band [or lowest conduction band] is flat but degenerate with a dispersive band at a high-symmetry point of the Brillouin zone; the consequences of having such band characteristics are briefly described. Multi-layer and bulk 2D COFs are found to maintain the salient features of the monolayer electronic structures albeit with a reduced bandgap due to the interlayer coupling. This Focus article is thus meant to provide an effective framework for the engineering of flat and Dirac bands in 2D polymer networks.

Gridization is an alternative way to create macromolecules of various sizes in addition to linear and dendritic polymerization as well as cyclization. Organic nanogrids are an expanding family of macrocycle-like closed structures at the nanoscale, but with a series of well-defined extension edges and vertices. Cyclic nanogrids can be used as nanoscale building blocks for the fabrication of not only rotaxanes, catenanes, knots, 3D cages, but also nanopolymers, covalent organic frameworks (COFs), metal-organic frameworks (MOFs), and complex molecular cross-scale architectures. In this review, the history of fluorene-based macrocycles has first been explored, followed by the development of the synthetic methodologies; in particular, fluorene-based nanogrids are highlighted owing to their features and applications. Typically, fluorenes are fused arenes with a hybrid entity between tetrahedral Csp3 and Csp2. Four ingenious connection modes of fluorene-based macrocycles, including 2,7-, 3,6-, 9,9-, and 2,9-linkages, fully demonstrate the geometric possibilities of the macrocycles and nanogrids. Such fluorene-based nanogrids will give birth to organic intelligence.

Zn-Zn bond as one of the metal-to-metal bonds in clusters and molecules is of fundamental interest in many areas of natural science. Neutral boronyl can be viewed as σ radical and has been found in the boronyl metal complexes. However, the complex with Zn-Zn bond stabilized by boronyl ligands has not been found so far. Herein, we report on the computational design of the simplest case of such a system: linear D∞h OBZnZnBO. The structural and electronic properties and chemical bonding on series of zinc complexes Znx(BO)y (x=1,2; y=1,2) with boronyl as ligands have been studied using quantum chemical calculations at the B3LYP and PBE0 level, respectively. For the Zn2(BO)2 cluster, the linear D∞h OBZnZnBO is the global minimum, in which the calculated Zn-Zn bond length of rZn-Zn = 2.400 A at B3LYP level, appears to be close to the latest recommended covalent radii (2.40 A) of the proposed single bond covalent radii of the Zn-Zn. Chemical bonding analyses show that D∞h OBZnZnBO possesses the linear four-center two-electron (4c-2e) σ bond. The σ bond framework has a contribution of Zn orbitals 54%, B orbitals 44%, which involves the Zn 4s 20% and 4p 34%, B 2s 28% and 2p 16%, respectively. Furthermore, the D∞h HZnZnH and NCZnZnCN clusters also exhibit one linear 4c-2e σ bond, due to the secondary contribution from the H s and C sp components, respectively. Linear 4c-2e σ bond greatly stabilizes the dizinc complexes. D∞h OBZnZnBO is thermochemically stable with respect to possible formation channel at room temperature, whereas the exergonic channel, 2ZnBO (C∞v, 2∑g)→OBZnZnBO (D∞h, 1∑g), the formation energy evaluated is -58.75 kcal mol1 at the B3LYP level. Thus D∞h OBZnZnBO as the first observation of Zn-Zn covalent bond in zinc complexes with boronyl as ligands may be synthesized in the laboratory in the near future.

The S/O heterocyclic covalent triazine frameworks (CTFs i.e., CTF – 7 and CTF - 8) were synthesized using thiophene and furan as building blocks, respectively. The hydrogen evolution rate of CTF-7 is 7430 μmol g-1 h−1, which is about 5.6 times that of CTF-8. Due to their low electronegativity, sulfur heteroatoms are more favorable for charge separation than oxygen heteroatoms in CTFs. This work provides a guiding principle for the design of high efficiency photocatalyst structure.

A series of covalent organic crown-based polymers coordinated with KI exhibit high activity. The synergetic effect plays an important role in accelerating the reaction rate.

Considerable efforts are being made to find cheaper and more efficient alternatives to the currently commercially available catalysts based on precious metals for the Hydrogen Evolution Reaction (HER). In this context, fullerenes have started to gain attention due to their suitable electronic properties and relatively easy functionalization. We found that the covalent functionalization of C60, C70 and Sc3N@IhC80 with diazonium salts endows the fullerene cages with ultra-active charge polarization centers, which are located near the carbon-diazonium bond and improve the efficiency towards the molecular generation of hydrogen. To support our findings, Electrochemical Impedance Spectroscopy (EIS), double layer capacitance (Cdl) and Mott-Schottky approximation were performed. Among all the functionalized fullerenes, DPySc3N@IhC80 exhibited a very low onset potential (-0.025 V vs RHE) value, which is due to the influence of the inner cluster on the extra improvement of the electronic density states of the catalytic sites. For the first time, the covalent assembly of fullerenes and diazonium groups was used as an electron polarization strategy to build superior molecular HER catalytic systems.

In this work we report on new heteroleptic coordination compounds [Pb2(LI)2](NO3)2∙2MeOH (1), [Pb2(LII)2](NO3)2 (2), [Pb2(LIII)2](NO3)2∙MeOH∙H2O (3) and [Pb2(LIII)2(H2O)](NCS)2 (4), which were obtained through self-assembling of 2-(amino(pyridin-2-yl)methylene)hydrazine-1-carbothioamide (HLI), 2-(amino(pyrazin-2-yl)methylene)hydrazine-1-carbothioamide (HLII) or 2-(amino(pyridin-2-yl)methylene)-N-methylhydrazine-1-carbothioamide (HLIII) with Pb(NO3)2 or a mixture of Pb(ClO4)2 and KNCS, respectively. In all the obtained complexes the lead(II) cation is N,N',S-chelated by the tridentate pincer type monodeprotonated ligand LI–III. In addition to the thiosemicarbazone chelation, the sulfur atom in each structure acts as bridging to connect two [Pb(LI–III)]+ units to form a dinuclear dimeric species having a centrosymmetric geometry, so that the ligands are directed either at different, in 1 and 2, or the same, in 3 and 4, side of the coplanar Pb2S2 core. In the latter structures two metal centers are additionally linked with each other through the oxygen atom of the bridging water molecule. The dimeric units in 1–4 are further linked through the Pb–N tetrel bonds, yielding 1D supramolecular polymeric chains, which, in turn, are interlinked though a myriad of other intermolecular noncovalent inetaractions, including tetrel bonds, hydrogen bonds and π-stacking. Counterions (NO3– and NCS–) as well as co-crystallized solvent molecules (MeOH and H2O) are also responsible in further stabilization of the overall crystal packing of the obtained complexes as a source of either tetrel and/or hydrogen bonds. The observation of the recurrent tetrel bonds in compounds 1–4 has been rationalized using DFT calculations and molecular electrostatic potential (MEP) surface plots. Moreover, coordination bonds (covalent character) and tetrel bonds (noncovalent character) between the complexes and their conterions (and water moelcule) have been differentiated using the quantum theory of «atoms-in-molecules» (QTAIM) and the noncovalent interaction index (NCI index) computational methods.

Covalent crosslinked stimuli-destructible hydrogels with the ability of irreversible stimuli-controlled bond dissociation have attracted great attentions due to their easy preparation, biocompatibility, biodegradability, stability against hydrolysis, and controlled solubility by applying desired triggers. Stimuli-controlled microstructure, elasticity, and mechanical properties has resulted in their application in selective capturing, proliferation, and detection of human and bacterial cells, drug delivery, wound dressing, and imprint lithography. Polymerization approaches and different functional groups required to prepare these hydrogels with the ability of irreversible bond dissociations, mechanism of stimuli-controlled bond cleavage, degradation products, comparison between the stimulants, and their final applications are highlighted in this review. Photocleavable hydrogels containing nitrobenzyl, coumarin, and perylene drivatives, redox-dissociable hydrogels containing diselenide and succinimide thioether bonds, destructible hydrogels prepared from phenolic ester and aldazine moieties as pH-cleavable bonds, and hydrogels crosslinked by enzyme- and thermo-dissociable moieties are the most important chemically crosslinked stimuli-destructible hydrogels, which show stimuli-controlled covalent bond dissociation with an irreversible mechanism.

The recently developed reversibly interlocked polymer networks are made from two-pre-formed crosslinked polymers containing reversible covalent bonds via topological rearrangement. Unlike interpenetrating polymer networks, the resultant is rather homogeneous regardless of the miscibility between the parent single networks, and can be repeatedly self-healed and unlocked/re-locked. The present work focuses on revealing the critical role of the hydrogen bonds between the single networks in construction of the interlocked networks, cooperating with dissociation and re-association of the built-in reversible covalent bonds. Based on the systematic investigations of the small molecules, single networks and interlocked networks, the inter-component hydrogen bonds of the interlocked networks are found to be able to be built-up, which are more stable than the intra-molecular hydrogen bonds of the single networks. They help to pull the chains from different single networks together, preventing the occurrence of phase separation during interlocking and implementing the valuable forced miscibility. Besides, the abundant but weak inter-component hydrogen bonds are preferred. The outcomes not only show the hitherto unknown part of the mechanism involved in the formation of the interlocked networks, but also benefit the design of new members of interlocked networks.

Highly crystalline covalent organic frameworks (COFs) or conjugated polymers (CPs) are very important and highly desirable because these materials would display better performance in diverse devices and provide more structure-property related information. However, how to achieve highly crystalline or single-crystal COFs and CPs is very challenging. Recently, many research studies have demonstrated the possibility of enhancing the crystallinity of COFs and CPs. Thus, it is timely to offer an overview of the important progress in improving the crystallinity of COFs and CPs from the viewpoint of design strategies. These strategies include polycondensation reaction optimization, improving the planarity, fluorine substitution, side chain engineering, and so on. Furthermore, the challenges and perspectives are also discussed to promote the realization of highly crystalline or single-crystal COFs and CPs.

Covalent organic frameworks (COFs) have emerged as highly crystalline porous organic materials and proved to be the potential candidates for various interesting applications, such as gas adsorption and separation, catalysis, energy storage, and sensing, etc. Fluorescence-based sensing has gained great attention due to its high selectivity, rapid response time, and real-time monitoring. Lately, luminescent COFs have come to the fore as sensing probes to detect the various target molecules. In this review, we have targeted a comprehensive account of the chronological development of the field of COFs starting from 2005 till date. We have described the design principle with a focus on various topologies reported, classification of their structural diversity on the basis of thirty-two linkages and dimensionality, methods of synthesis with examples, and the use of various characterization techniques. Interestingly, almost one-half of the COFs contains linkages that are nitrogen-rich. With a background in different processes involved for fluorescence sensing, we have illustrated the potential applicability of nitrogen-rich COFs as sensors for numerousanalytes, such as explosives, volatile organic molecules, pH, temperature, toxic anions, metal ions and biomolecules from different media utilizing the striking features of COFs with predesigned structures and diverse functionality.

Finding allotropes with novel structures and intriguing properties is of great interest from both fundamental and applicable standpoints. Here, we propose a hitherto unknown boron allotrope, possessing intrinsic superconductivity and hardness at ambient pressure. With the aid of swarm-intelligence structure search calculations, besides reproducing the known SrB6, a boron-richer compound, SrB8, becomes stable at high pressure, whose remarkable structure feature is that it contains a channel-like boron covalent framework constructed by anticlinal pentapyramid. More interestingly, the removal of Sr atoms, locating at the center of channel, leads to the formation of a novel o-B16 boron allotrope at ambient pressure. It is metallic with superconducting transition temperature of 14.2 K. In addition, o-B16 demonstrates inherent hard nature with an estimated Vickers hardness of 19.2 GPa.

The catalytic cycloaddition of CO2 to epoxides is one of the most promising and green pathways for CO2 utilization in industry. In recent years, covalent organic frameworks (COFs) as a flourishing class of organic porous materials have been widely used for efficient capture and conversion of CO2. By virtue of the flexible regulation of pore parameters and the task-specific introduction of catalytically active components into their crystalline structures, well-designed COFs with tailored functions and stable and ordered frameworks may be a viable alternative to metal–organic frameworks (MOFs) so as to meet the multifaceted requirements of CO2 activation and transformation. This review describes the recent advances made with regard to the design and synthesis of tailored COFs for simultaneously capturing and converting CO2 into cyclic carbonates. Given the presence of different kinds of catalytically active sites, we have divided recently reported COFs into four main categories, i.e., covalent triazine frameworks (CTFs), hydroxyl-decorated COFs (hydroxyl COFs), metal-functionalized COFs (metal COFs) and ionic liquid-modified COFs (ionic COFs). The rational design of organic polymeric monomers and the wise choice of the pre-synthesis or post-modification strategy have been extensively emphasized and discussed here in detail. We expect that valuable guidance and a unique overview may be provided towards CO2 conversion into cyclic carbonates, thereby developing numerous function-led COFs with excellent industrial application prospects.

Conventionally cross-linked polymer networks known as thermosets contain permanent cross-links which prevent their recyclability, leading to major sustainability and environmental challenges. To overcome this problem, covalent adaptable networks (CANs) containing dynamic covalent bonds have been studied over the past two decades. Because of their dynamic nature, CANs are capable of undergoing reversible or exchange reactions rendering them reprocessable, offering a sustainable alternative to thermosets. However, unlike thermosets with static cross-links, CANs are considered to be highly susceptible to creep especially at elevated temperature, which limits their utility in many high-value applications. Here, we use the dynamic cross-linker bis(2,2,6,6-tetramethylpiperidin-1-yl) disulfide methacrylate (BiTEMPS methacrylate) in the free radical polymerization of reprocessable poly(hexyl methacrylate) networks with different degrees of cross-linking. Full recovery of cross-link density was achieved after multiple recycling steps. We show that BiTEMPS chemistry is capable of arresting creep at elevated temperature up to 90 °C. Poly(hexyl methacrylate) networks containing 5 mol% BiTEMPS exhibited almost no creep with strain values of 0.07% and 0.38% at 70 °C and 90 °C, respectively, after 13.9 h of continuous, 3 kPa shear stress. This excellent creep resistance is comparable to the creep response of static networks. The temperature-dependent viscosity of a BiTEMPS-cross-linked dissociative network calculated from creep data followed an Arrhenius relationship. The viscous flow activation energy from creep and the stress relaxation activation energy were very similar to the bond dissociation energy of disulfide bonds in BiTEMPS, indicating that the creep and stress relaxation mechanisms are both dominated by the dynamic chemistry in the network. This work indicates that BiTEMPS chemistry offers a simple method to synthesize CANs with excellent elevated-temperature creep resistance while achieving full recovery of cross-link density after recycling.

In entrapment an active species, which is often a catalyst, is trapped within a material by a solid or gel forming event; thus, it becomes dispersed within the solid or semi-solid matrix. Entrapment methods can be used to immobilize isolated enzymes and render them more stable, and easier to separate and recycle. Entrapment immobilization methods are well established for whole cell biocatalysis. Despite this the applications of entrapment towards isolated enzyme immobilization have lagged the use of covalent attachment and crosslinking methods. In this review entrapment methods are contrasted with other methods of enzyme immobilization and literature methods of enzyme entrapment are reviewed. A key advantage of this approach is that no formal interaction with the protein is required, but this must be balanced against the threat of enzyme leaching, or introduction of mass transfer limitations. The main methods of entrapment are characterized, and some recent innovations are highlighted.

Supramolecular hydrogels gained significant attention as shear-thinning, self-healing materials. However, the introduction of non-covalent crosslinks inherently decreases the strength and stability of the hydrogel. In this work, we developed a novel supramolecular hydrogel that undergoes a reversible transformation to the corresponding covalently crosslinked hydrogel upon UV-irradiation. The supramolecular hydrogel was developed based on the ternary host–guest interaction of two anthracene moieties and one large macrocyclic host. Anthracene functionalized poly(N-acryloylmorpholine)s were synthesized by post-polymerization modification of a copolymer consisting of N-acryloylmorpholine and an activated ester comonomer, whereby two different polymers were prepared having either neutral anthracene side-chains or carrying a positive charge next to the anthracene to enhance the interaction with the host. The binding affinity of the anthracene side chains with and without an additional cationic charge were studied with two macrocyclic hosts, namely cucurbit[8]uril and γ-cyclodextrin (γ-CD) by UV-Vis titration revealing a markedly stronger binding in the presence of the cationic charge due to additional ion-dipole one of the macrocyclic hosts, cucurbit[8]uril. Subsequently, the effect of the binding affinity on the hydrogelation was investigated, indicating that the stronger binding affinity facilitated the hydrogel formation at lower concentration. Finally, the reversible transformation of the supramolecular hydrogel to a chemical hydrogel by anthracene dimerization was studied by the UV irradiation of the hydrogel at 365 nm for covalent crosslinking or at 254 nm for decrosslinking. It could be demonstrated that the dynamic nature of the hydrogel, that is responsible for the shear-thinning behavior, was indeed lost upon UV-irradiation indicative of the formation of a covalently crosslinked hydrogel. The capabilities of the formed supramolecular hydrogel that is easily processable and able to reversibly convert to a chemical hydrogel, provides potential applications in applying mechanically robust covalently crosslinked hydrogels in complex shapes and difficult to reach locations making use of the dynamic nature of the supramolecular crosslinks.

In this study, pyrene was used as a fluorescent dye for peptides. A sensitive, selective, and simple sensor platform was built to detect chymotrypsin based on the covalent binding of peptides to gold nanoparticles (AuNPs) and GO. NaBr as a robust back-filler on gold ensured that the peptides were attached on the surface of AuNPs. Chymotrypsin was added to cleave a specific site on the peptide. Fluorescence was restored after the release of the fluorescent group. The limit of detection was 7.394 pg mL−1. Our method could be applied to real samples.

The chemical functionalization or modification of polymers to alter or improve the physical and mechanical properties constitutes an important field in macromolecular research. Fabrication of polymeric materials via structural tailoring of commercial or commodity polymers that are produced in vast quantities especially possess unique advantages in material applications. In the present study, we report on benign chemical modification of unsaturated styrene–isoprene–styrene (SIS) copolymer using available backbone alkene groups. Covalent attachment of aldehyde functional substrates onto reactive isoprene double bond residues was conveniently carried out using UV-induced Paterno–Buchi [2 + 2] cycloaddition. Model organic compounds with different structures were utilized in high efficiency chemical modification of parent polymer chains via oxetane ring formation. Functionalization studies were confirmed via 1H NMR, FT-IR and SEC analyses. The methodology was extended to covalent crosslinking of polymer chains to obtain organogels with tailorable crosslinking degrees and physical characteristics. Considering the outstanding elastic properties of unsaturated rubbers and their high commercial availability, abundant reactive double bonds in backbone chains of these polymers offer easy to implement structural modification via proposed Paterno–Buchi photocycloaddition.

Nanocomposite double-network hydrogels (ncDN hydrogels) are recently introduced to address the limitations of traditional DN hydrogels, such as the lack of diversity in the network structure and the restricted functionalities. However, two challenges remain, including the time-consuming preparation and the lack of shear-thinning and self-healing properties. Here, our approach to developing versatile ncDN hydrogels is through the use of multiple interfacial crosslinking chemistries (i.e., noncovalent interactions of electrostatic interaction and hydrogen bonds as well as dynamic covalent interactions of imine bonds and boronate ester bonds) and surface functionalized nanomaterials (i.e. phenylboronic acid modified reduced graphene oxide (PBA-rGO)). PBA-rGO was used as a multivalent gelator to further crosslink the two polymer chains (i.e. triethylene glycol-grafted chitosan (TEG-CS) and polydextran aldehyde (PDA)) in DN hydrogels, forming the TEG-CS/PDA/PBA-rGO ncDN hydrogels in seconds. The microstructures (i.e. pore size) and properties (i.e. rheological, mechanical, and swelling properties) of the ncDN hydrogels can be simply modulated by changing the amount of PBA-rGO. The dynamic bonds in the polymeric network provided the shear-thinning and self-healing properties to the ncDN hydrogels, allowing the hydrogels to be injected and molded into varied shapes as well as self-repair the damaged structure. Besides, the designed TEG-CS/PDA/PBA-rGO ncDN hydrogels were cytocompatible and also exhibited antibacterial activity. Taken together, we hereby provide a nanomaterial approach to fabricate a new class of ncDN hydrogels with tailorable networks and favorite properties for specific applications.

Pathogenic E. coli pose a significant threat to public health, as strains of this species cause both foodborne illnesses and urinary tract infections. Using a rapid bioconjugation reaction, we selectively capture E. coli at a disposable gold electrode from complex solutions and accurately quantify the pathogenic microbes using electrochemical impedance spectroscopy.

Covalent organic frameworks (COFs) are emerging porous polymer materials. They are characterized by functionalization of their surface chemical properties, and excellent physical and chemical stability. This review focuses on the advances of COFs in lithium ion batteries (LIBs) regarding the active sites and discusses the redox mechanisms of active sites. Furthermore, the modification methods of COFs as electrode materials are analyzed and summarized.

Attaching proteins to surfaces while maintaining bioactivity is a promising avenue for developing new functional materials. This work describes a method to rapidly apply bioactive coatings by conjugating protein into an adhesive network using an ortho-phthaldialdehyde (oPA)-based linker. The polymer matrix was generated using a copper-catalyzed azide-alkyne cycloaddition (CuAAC) polymerization on a commercial, antifouling copper-based paint that had not been previously examined as a catalytic material. After undergoing bioconjugation with the oPA linker, protein was retained at a higher rate on the surface when compared either with the control, which lacked a linker, or with a commercially-available maleimide linker. The ability to apply in situ, polymerize, and adhere biomacromolecules to surfaces while retaining their efficacy enables the creation of novel functional materials with properties usually reserved for the biological domains.

The synthesis of coinage metal aluminyl complexes, featuring M–Al covalent bonds, is reported via a salt metathesis approach employing an anionic Al(i) (‘aluminyl’) nucleophile and group 11 electrophiles. This approach allows access to both bimetallic (1 : 1) systems of the type (tBu3P)MAl(NON) (M = Cu, Ag, Au; NON = 4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-dimethylxanthene) and a 2 : 1 di(aluminyl)cuprate system, K[Cu{Al(NON)}2]. The bimetallic complexes readily insert heteroallenes (CO2, carbodiimides) into the unsupported M–Al bonds to give systems containing a M(CE2)Al bridging unit (E = O, NR), with the μ-κ1(C):κ2(E,E′) mode of heteroallene binding being demonstrated crystallographically for carbodiimide insertion in the cases of all three metals, Cu, Ag and Au. The regiochemistry of these processes, leading to the formation of M–C bonds, is rationalized computationally, and is consistent with addition of CO2 across the M–Al covalent bond with the group 11 metal acting as the nucleophilic partner and Al as the electrophile. While the products of carbodiimide insertion are stable to further reaction, their CO2 analogues have the potential to react further, depending on the identity of the group 11 metal. (tBu3P)Au(CO)2Al(NON) is inert to further reaction, but its silver counterpart reacts slowly with CO2 to give the corresponding carbonate complex (and CO), and the copper system proceeds rapidly to the carbonate even at low temperatures. Experimental and quantum chemical investigations of the mechanism of the CO2 to CO/carbonate transformation are consistent with rate-determining extrusion of CO from the initially-formed M(CO)2Al fragment to give a bimetallic oxide that rapidly assimilates a second molecule of CO2. The calculated energetic barriers for the most feasible CO extrusion step (ΔG‡ = 26.6, 33.1, 44.5 kcal mol−1 for M = Cu, Ag and Au, respectively) are consistent not only with the observed experimental labilities of the respective M(CO)2Al motifs, but also with the opposing trends in M–C (increasing) and M–O bond strengths (decreasing) on transitioning from Cu to Au., The differential reactivity of copper, silver and gold aluminyl compounds towards CO2 and other heteroallenes are probed by experimental and quantum chemical methods.

In this study, an electrochemical sensing strategy was developed based on the synergies of gold nanoparticles (AuNPs) doped carboxylated covalent organic frameworks (ACOFs) and poly(fuchsin basic) film for the simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA). This strategy not only took advantage of the adopted materials but also made use of the H-bonding and electrostatic interaction between the three compounds and materials. For this sensing, a poly-BFu film was formed on the surface of bare glass carbon electrode (GCE) under a constant potential. AuNPs was highly dispersed and immobilized on the constructed ACOF-TaTp to obtain AuNPs@ACOF. The constructed sensor AuNPs@ACOF/p-BFu/GCE combined the merits of high surface area, hydrophilicity, conductivity, and selective affinity, consequently exhibiting high sensitivity and selectivity toward the simultaneous detection of AA, DA, and UA with wide linear response ranges of 25-1500 μM, 0.75-40 μM, and 1-200 μM, respectively. The corresponding detection limits were 12.0 μM, 0.15 μM, and 0.22 μM. The simultaneous determination of UA in real human urine sample further confirmed the practicability of the designed electrode.

In contrast to aromatic compounds with particular stability, antiaromatic compounds are usually less stable due to their high reactivity and unfavorable formation energies. Cyclo[16]carbon (C16) is a carbon ring molecule with a dual antiaromatic character. In this study, we demonstrate that C16 can be transformed into highly aromatic molecules upon metal encapsulation. The geometrical characteristics, electronic properties and thermodynamic stability of MC16 compounds (M = Ca, Sc, Ti, V, Ce, U) are fully investigated from a theoretical perspective. Based on natural population analysis, atom-in-molecules theory and localized molecular orbital analysis, the nature of the metal–carbon interaction in the MC16 compounds is investigated. It has been proved that the bonding between Ca and C16 corresponds to a typical ionic interaction, while other metal atoms form polar covalent bonds with C16. By analyzing the frontier molecular orbitals and magnetic response of MC16, we have found that all the encapsulated metal atoms donate two electrons to the in-plane π orbitals via either electron transfer or orbital hybridization, which makes the in-plane π orbitals completely satisfy the 4n + 2 (n = 4) Huckel aromaticity rule. The U atom formally transfers four electrons to the carbon ring in total, two to the in-plane π orbitals and two to the out-of-plane π orbitals, which results in the remarkable dual aromaticity feature of UC16. The transformation of aromaticity can be utilized to develop new strategies for the synthesis of novel carbon ring molecules.

Fluorine-containing compounds significantly enrich the diversity of inorganic chemical structures. Here, four alkaline-earth metal difluorophosphates with different space groups, namely NH4Mg(PO2F2)3 (Cmcm) (1), NH4Sr(PO2F2)3 (P1[combining macron]) (2), (NH4)2Ba(PO2F2)4 (P2/n) (3) and Ba(PO2F2)2 (I4[combining macron]2d) (4), were synthesized and their structures were determined for the first time. 4 is not only the first alkaline-earth-metal difluorophosphate, but also the first difluorophosphate reported to crystallize in the non-centrosymmetric space group I4[combining macron]2d of the tetragonal crystal system. All of the three-dimensional (3D) structures of the title compounds consist of isolated (PO2F2)-, AE-O and NH4+ units, while the differences of the cation radius result in various arrangements of the (PO2F2)- units, which leads to diverse crystal structures and the disparate optical anisotropy of the crystals. According to the deep-ultraviolet (DUV) transmittance spectrum, 3 exhibits a short DUV cut off edge (

Acrylonitrile (AN) and ammonia (NH3) are two important nitrogen-containing interstellar molecules in outer space, especially on Titan. Herein, we measured infrared (IR) spectra of neutral and cationic AN-NH3 complexes by VUV single-photon ionization combined with time-of-flight mass spectrometry. On combining IR spectra with the theoretical calculations, we found that the molecules prefer to form a single-ring cyclic H-bonded structure in the neutral AN-NH3 and (AN)2-NH3 clusters. However, after ionization of AN-NH3 and (AN)2-NH3 clusters, a new C-N-covalent bond is confirmed to form directly between AN and NH3, without any energy barrier in the cationic complexes. Moreover, in the ionized (AN)2-NH3 cluster, the covalent C-N bond prefers to form between AN and NH3 rather than the two AN groups. These results provide spectroscopic evidence of AN forming a new molecule with NH3, induced by VUV radiation. The formation of the new C-N bond broadens our knowledge on the evolution of the prebiotic nitrogen-containing molecules in space.

Hydrogen passivation is an important method used to stabilize a specific graphene edge. Although several hydrogen-terminated graphene edges have been proposed in theory, a comprehensive exploration of highly stable hydrogen-terminated graphene edges is still absent. According to the bare graphene-edge databases, a series of hydrogen-terminated graphene edges have been proposed. The energy stability of hydrogen-terminated zigzag and armchair graphene edges is fully investigated. The six most stable hydrogen-terminated zigzag edges and six armchair edges of graphene are determined. Hydrogen passivation makes hydrogen-terminated graphene edges energetically more stable than bare graphene edges. The additional hydrogen atoms balance the dangling bonds of carbon atoms at edges by forming hydrogen-carbon covalent bonds. Hydrogen-terminated graphene edges with six-membered carbon rings have better global stability than those composed of non-hexagonal structural units. The effects of the experimental temperatures and hydrogen partial pressures on the stability of hydrogen-terminated graphene edges are fully investigated. Furthermore, hydrogen passivation can open the band gap of graphene effectively. These results provide a deep understanding of hydrogen-terminated graphene nanostructures.

We report the syntheses, structures, magnetic and electrochemical properties of MRhRh metal cores helically wrapped by four dpa− (2,2′-dipyridylamide) ligands. We successfully synthesized the precursor Rh2(dpa)4 (1) in high yield and characterized its structure including its oxidized form (1+) which facilitated the syntheses of this series of metal springs. By the reactions of (1) and the metal ions of group 7 to group 12 (M = Mn(2), Fe(3), Co(4), Ni(5), Cu(6), Pd(8), Pt(9), Ru(10), Ir(11) and Rh(12)), ten MRh2(dpa)4Cl2 complexes were successfully isolated. Note that Cd(7) can only be obtained by the one-pot method. The yield of Rh3(dpa)4Cl2 (12) is also improved by this stepwise method. The oxidized complexes [MRh2(dpa)4Cl2](PF6) (M: Ni(5+), Ru(10+), Ir(11+)) are also synthesized for the studies of electronic structures and magnetic properties. The X-ray diffraction technique is applied to characterize all of their structures. The results of these structural, magnetic, and electrochemical studies provide us with in-depth knowledge and comprehensive insight into metal–metal bonds and interactions for this new series of metal strings. In particular, four metal–metal bonds with short distances are found: Pd–Rh (2.372(13) A), Pt–Rh (2.385(7) A), Ru–Rh (2.33(3) A), and Ir–Rh (2.373(5) A). The remaining ones show no evidence of covalent metal bonds judging from their metal–metal distances, magnetic behaviour, and redox couples in electrochemical analysis. Besides, two unique tetranuclear MRhRhM(dpa)4X2 (M: Cu+(13) and Ag+(14)) complexes with a Rh2(dpa)4 framework are developed. Four metals are aligned linearly. This coordination mode of metal strings provides a unique synthetic route for constructing longer metal chains from a smaller number of dentate ligands.

Currently, there is a need to explore the effects of different types of protein-anthocyanin complexations, as well as the possible changes in the nutrition and allergenicity of the formed complexes. Here, we systematically investigated the covalent and non-covalent interactions between cyanidin-3-O-glucoside (C3G) and two major milk proteins, α-casein (α-CN) and β-lactoglobulin (β-LG). Fluorescence quenching data showed that, under non-covalent conditions, C3G quenched the fluorescence of the two proteins via a static process, with the interaction forces being revealed; for covalent products, decreased fluorescence intensities were observed with red shifts in the λmax. Multiple spectroscopic analyses implied that C3G-addition induced protein structural unfolding through transitions between the random coil and ordered secondary components. With a two-stage simulated gastrointestinal (GI) digestion model, it was seen that covalent complexes, not their non-covalent counterparts, showed reduced protein digestibility, ascribed to structural changes resulting in the unavailability of enzyme cleaving sites. The GI digests displayed prominent 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation-scavenging abilities (3.8-11.1 mM Trolox equivalents per mL digest), in contrast to the markedly reduced 1,1-diphenyl-2-picrylhydrazyl radical-scavenging capacities. Additionally, covalent protein-C3G complexes, but not their non-covalent counterparts, showed lower IgE-binding levels in comparison to the native control. This study provides new understanding for the development of anthocyanin-milk protein systems as functional ingredients with health-beneficial properties.

Microporous materials are ideal building blocks for separation membranes due to their molecular-sized pores and high porosity. However, it is challenging to assemble/grow crystalline microporous materials, such as zeolites, metal–organic frameworks (MOFs), and covalent organic frameworks (COFs), into ultrathin and defect-free selective membranes. Amorphous microporous materials, such as polymers of intrinsic microporosity (PIMs), have been deposited as ultrathin selective membranes, but their chemical stability, especially in various organic solvents, may be a concern. Herein, for the first time we report microporous metal–organic networks (mMONs) formed via alcoholysis reaction between contorted/rigid organic units with catechol groups and metal linkers. mMONs exhibit similar microporosity to existing microporous materials, high chemical stability and structural integrity against various chemical environments, because of the contortion and rigidity of the organic units and covalent bonds between metal linkers and catechol groups. An interfacial process is developed to fabricate ultrathin mMON membrane (30–120 nm). Compared with the reported organic solvent nanofiltration (OSN) membranes with a similar molecular weight cut-off (MWCO), mMON membranes exhibit similar or higher solvent permeance.

A highly practical method for comprehensive chiroptical sensing of free α amino acids with streamlined operation and high sensitivity via dual CD/UV measurements is developed. The assay takes advantage of an efficient and selective three-component labeling reaction of primary amines with o-phthalaldehyde and p-toluenethiol reagents to derivatize the NH2 group of analytes into an isoindole. The covalent labeling generates sensitive UV and CD readouts, both of which show an excellent linear relationship with the concentration of analytes. The high reactivity and the novel optical reporting mechanism allow fast and accurate measurement without background interference. The sensing assay works well for a remarkably broad range of analyte concentrations, with an unprecedented lower limit of 10 micromolar concentration.

Extraordinary mechanical properties of supramolecular gels (fracture toughness, fatigue resistance, injectability and self-healing ability) are strongly affected by their viscoelastic response driven by rearrangement (association and dissociation) of physical bonds. The kinetics of rearrangement is traditionally studied in small-amplitude shear oscillatory tests by analyzing the effect of the frequency of oscillationsωon the storageG′ and lossG′′ moduli. Conventional Maxwell-type models describe observations rather poorly when the gels reveal a pronounced flattening of the graphsG′′(ω) at high frequencies. A simple model is derived in linear viscoelasticity of supramolecular gels. Its advantage is that the model reproduces experimental data correctly, on the one hand, and involves only four material constants, on the other. Based on the analysis of experimental data on gels cross-linked by coiled-coil complexes, covalent and ionic bonds, phenylboronic acid-diol complexes and metal-ligand coordination bonds, the model is applied to develop structure-property relations that describe the influence of chemical structure of supramolecular gels (concentration of polymer chains and type and molar fraction of temporary bonds) and environmental conditions (temperature, pH and ionic strength of buffer solutions) on their viscoelastic response.

A multifunctional gate dielectric material based on dual cross-linked aromatic polythiourea (c-PTU) networks for organic field-effect transistors is presented. Tailoring the dual covalent and noncovalent cross-links in the c-PTU gate dielectric enables all the advantageous capabilities of excellent insulating properties, including high capacitance, good solvent resistance and thermal stability, as well as low-temperature solution processing and photo-patterning.

International audience; Deep eutectic solvents (DESs) represent an emerging class of solvents featuring some characteristics of their ionic liquid cousins – low vapor pressure, relatively wide liquid range, non-flammability and the ability to dissolve polar species – along with unique specificities, such as their limited toxicity and an improved biocompatibility. Among the numerous applications these solvents may find, their use as media for the ionothermal preparation and post-synthetic modification of metal- and covalent organic frameworks (MOFs and COFs) has been recently explored. This contribution aims at providing an overview of the state of the art in this area focusing on the synthetic aspects as well as on the applications of the materials and composites reported. In particular, the different roles DESs can play in the MOF/COF formation are highlighted. Indeed, while DESs act as solvents, they may also behave as structure-directing agents. Thus, one of their components or decomposition products formed under the ionothermal conditions may be present in the architectures, either as a ligand coordinated to the metal centers or in the pores of the MOFs, yielding unknown crystalline systems. Removal of the DES components from the MOF has been shown as an efficient strategy for the preparation of novel porous architectures. Furthermore, DESs can be employed for the conversion of one MOF into another. DESs show clear advantages as media for COF synthesis, such as the possibility to run reactions at lower temperature, in open-air vessels, with shortened reaction time or to elaborate COFs otherwise difficult to access and with a large variety of linkages. Beyond their solvent role, DESs can also be employed for post-synthetic modification, affording composites or hybrids benefiting from the properties of these media combined with the ones of the porous materials. Applications in catalysis for a diversity of reactions, in gas sorption or for the sensing/extraction of various analytes have been demonstrated

Herein, the clinically approved nitrogen mustard, chlorambucil (Chl), is covalently embedded into a poly(N-(2-hydroxypropyl)methacrylamide, HPMA) vector via a hydrolysable ester bond to overcome the shortcomings of Chl as well as to achieve better efficacy. The well-defined poly-prodrug amphiphiles with Chl loading content >10 wt% can form uniform nanoparticles with an average diameter of 200 nm through a macromolecular self-assembly strategy. The detailed structure information and Chl release properties are carefully inspected. Cytotoxicity studies against the HepG2 and MCF-7 cell lines combined with flow cytometry reveal that the poly(HPMA)–Chl conjugate exhibits obvious targeting ability and markedly enhanced antitumor effect compared to the free Chl. After labelling with a fluorescent group, the cell uptake, lysosome escape and distribution in living organs of the poly-prodrug were also studied.

Having the benefits of low cost, excellent stability and tolerance to extreme conditions, nanozymes are a potential alternative of horseradish peroxidase (HRP) or other enzymes for bioanalytical chemistry, especially immunoassays. CeO2 nanoparticles have oxidase-mimicking activity and can avoid the use of unstable H2O2. For robust assays, the effect of proteins on the activity of CeO2 needs to be carefully studied. Herein, we studied the adsorption and desorption of bovine serum albumin (BSA) from CeO2. The CeO2 nanoparticles exhibited a higher protein adsorption capacity compared to the other tested metal oxide nanoparticles. Although the oxidase-like activity of CeO2 was inhibited by BSA, low concentrations of phosphate and fluoride ions boosted the activity of protein-capped CeO2. CeO2 was still active under strong acidic conditions and at high temperature, while HRP lost its activity. For immunoassay development, we covered CeO2 with an amine-modified silane for covalent conjugation to antibodies. A one-step indirect competitive ELISA for fenitrothion was developed, and an IC50 value of 35.6 ng mL-1 and a limit of detection of 2.1 ng mL-1 were obtained.

Two-dimensional crystalline covalent triazine frameworks (2D-CTFs) are emerging 2D materials with the characteristics of fully annulated conjugated structures and aromatic nitrogen-rich skeletons. Due to the difficulty in the control of the polymerization dynamics, the preparation of crystalline 2D-CTFs is still a daunting challenge compared to that of other organic framework materials. Herein, we report the construction of crystalline 2D-CTFs using dual modulator control, in which aniline and a co-solvent are used as dual modulators for a dynamic covalent linkage formation and non-covalent self-assembly process, respectively. The strategy successfully leads to crystalline CTFs from different functional building blocks. The crystalline CTFs could be further regulated via peripheral functionalization, which dramatically boosted the photocatalytic activity for oxidation of sulfides into sulfoxides, and excellent conversion rates and selectivity for a wide range of sulfides with various functional groups were achieved after functionalization with methoxyl groups. This work gives new insights into the design and synthesis of crystalline CTFs for photocatalytic applications.

A TPE-based fluorescent porous covalent organic polymer (COP-3) was designed and synthesized. The COP-3 exhibits excellent performance in sensing Fe3+ with high anti-interference, recyclability and a low limit of detection (LOD) of 0.191 μM (10.696 ppb), which is much lower than those of the reported metal-free porous polymers.

A "two-in-one" strategy was employed to construct 3D-COFs for the first time. Based on this strategy, a 3D-Flu-COF could be readily synthesized in various simplex organic solvents. Benefitting from the non-conjugated structure, the 3D-Flu-COF showcased excellent acidichromic sensing performance with good sensitivity, reversibility and naked eye visibility.

Smart materials based on photo-responsive dynamic covalent bonds have the potential for use in many applications, such as photo-modulated manipulators, actuators and self-healing materials. However, the development of high-performance multifunction visible-light-driven dynamic covalent systems has been insufficient. Herein, we report a novel linear polyurethane elastomer (HABI-PU) containing visible-light-switchable hexaarylbiimidazole (HABI) units in the polymer backbone with photo-induced scission and rapid healing capacities. When exposed to 405 nm light, the scratches on the HABI-PU film took only a few seconds to heal. More serious cut damage could be healed after exposure for 30 s and placed in the dark at room temperature for 6 h. Moreover, when a certain weight was loaded during light irradiation, the elastomers broke off as the toughness of the HABI-PU elastomers decreased. The reversible dissociation of the C–N bond of the HABI units caused the scission of long polymer chains into short chains upon light irradiation and further endowed HABI-PU with the properties of photo-induced fracture/healing. Such elastomers are promising for application in the fields of photo-controlled triggers, biomimetic systems, recycled materials, optical machining, and other engineering streams.

Reverse osmosis (RO) membrane technology, as an effective and eco-friendly method, has been widely used for seawater desalination and sewage treatment. However, RO membranes inevitably suffer serious organic and biological fouling during operation. Herein, we fabricated a hydrophilic anti-fouling layer on the RO membrane surface through the synergistic effect of covalent bonds and coordination bonds. Polyethyleneimine (PEI) and polyaspartic acid (PASP) are assembled onto the RO membrane surface successively. Fe(III) is utilized to induce further cross-linking for fabricating the PEI/PASP/Fe layer. The modified membranes exhibit superior hydrophilicity, whose water contact angle declines from 86.7° to 23.6°. In addition, the water flux of the PEI/PASP/Fe membrane increases by 45.8% with an excellent desalting property. Long-term, multi-cycle membrane fouling experiments demonstrate that the modified membrane manifests not only a lower flux loss rate (DRt) but also a higher flux recovery rate (FRR). This means that the hydrophilic layer modified membranes show excellent separation performance even under severe environments, which is expected to boost the anti-fouling research in the membrane field.

The effective construction of electron transport channels has essential significance for electron-transfer rate enhancement in REDOX processes during peroxymonosulfate (PMS) activation. This study focuses on the establishment of Cu-involved covalent bonds due to the unique electron configuration of Cu ions. The strategy was achieved by anchoring Cu atoms to an O-doped g-C3N4 (Cu–O–CN) matrix. The C–O–Cu linkage was successfully constructed, derived from the precise incorporation of oxygen. From XAFS, H2-TPR, and solid-ESR characteristic observations, the desired REDOX performance was verified. The constructed C–O–Cu linkages were treated as electron transport channels for electron transfer while reacting with PMS, effectively accelerating the REDOX circulation of the Cu(II)/Cu(I) redox couple and promoting the consecutive generation of active species. Consequently, nearly 100% bisphenol A (BPA) was degraded in the Cu–O–CN/PMS reaction system within 30 min. This demonstrates the effectiveness of Cu–O–CN for PMS activation. The prepared Cu–O–CN exhibited definite stability and potential reusability. This research not only highlights the tailored design of heterogeneous catalysts for PMS activation but also broadens its application in water purification.

Organic functionalization of graphene is successfully performed via 1,3-dipolar cycloaddition of azomethine ylide in the liquid phase. The comparison between 1-methyl-2-pyrrolidinone and N,N-dimethylformamide as dispersant solvents, and between sonication and homogenization as dispersion techniques, proves N,N-dimethylformamide and homogenization as the most effective choice. The functionalization of graphene nanosheets and reduced graphene oxide is confirmed using different techniques. Among them, energy-dispersive X-ray spectroscopy allows to map the pyrrolidine ring of the azomethine ylide on the surface of functionalized graphene, while micro-Raman spectroscopy detects new features arising from the functionalization, which are described in agreement with the power spectrum obtained from ab initio molecular dynamics simulation. Moreover, X-ray photoemission spectroscopy of functionalized graphene allows the quantitative elemental analysis and the estimation of the surface coverage, showing a higher degree of functionalization for reduced graphene oxide. This more reactive behavior originates from the localization of partial charges on its surface due to the presence of oxygen defects, as shown by the simulation of the electrostatic features. Functionalization of graphene using 1,3-dipolar cycloaddition is shown to be a significant step towards the controlled synthesis of graphene-based complex structures and devices at the nanoscale., 15 pages, 8 figures, for associated Supporting Information see http://shorturl.at/dCQ07

Hydrogel is a potential wound dressing material due to its ability to maintain a humid environment, the strong absorptive capacity of exuded tissue fluid, and gas exchange function. Herein, poly(N-isopropyl acrylamide)/keratin double network (PNIPAAm/keratin DN) gels were fabricated through covalent and ionic double cross-linking strategy. The effects of PNIPAAm/keratin ratios on the morphology and swelling rate of gels were characterized. The DN gels could swell up from 2600% to 4600% in proportion to the keratin content, demonstrating their great ability to absorb tissue fluid. The gels possessed thermo-sensitiveness, imparting self-stripping property. Moreover, the antibacterial chlorhexidine acetate (CHX) was loaded into gels with a post-fabrication drug-loading strategy. The release behavior showed that CHX-loaded DN gels exhibited multiple responsive characteristics (temperature, pH, and ROS). Furthermore, the drug-loaded gels showed greater antibacterial activity than free CHX due to the sustained drug release effect. Meanwhile, the antioxidant efficiency of PNIPAAm/keratin DN gels was ca. 33.1%, while the PNIPAAm gel was just ca. 18.2%, indicating the strong oxidation resistance of DN gels. In the Sprague Dawley (SD) rat skin defect model, the hydrogel had better tissue regeneration ability than the commercial film. Taken together, the multifunctional PNIPAAm/keratin DN gels are potential candidates for clinical wound treatment.

Interactions between an atomically precise gold nanocluster Au102(p-MBA)44 (p-MBA = para mercaptobenzoic acid) and a fluorescent organic dye molecule (KU, azadioxatriangulenium) are studied. In solution, the constituents form spontaneously a weakly bound complex leading to quenching of fluorescence of the KU dye via energy transfer. The KU can be separated from the complex by lowering pH, leading to recovery of fluorescence, which forms a basis for an optical reversible pH sensor. However, the sensor is not a stable entity, which could be delivered inside cells. For this purpose, a covalently bound hybrid is synthesized by linking the KU dye to the ligand layer of the cluster via an ester bond. Covalent linking facilitates entry of the cluster–dye hybrids into cells via endocytosis. Inside cells, the hybrids accumulate in endosomes where Au102 releases its cargo via hydrolysis of the ester bond. Changes of the local pH inside endosomes regulate reversible fluorescence due to variations in the interactions between the Au102 cluster and the dye. This work presents a concept for delivering reporter molecules into cells by using atomically precise gold nanoclusters as carriers and paves the way for future developments of cluster-reporter sensors for in vivo measurements of e.g. absolute pH values or ion concentrations.

Vancomycin is an amphoteric glycopeptide molecule, and its group diversity and chiral active sites provide a potential basis for its application in chromatographic analysis. In this article, using photosensitive diazo resin (DR) as the coupling agent, vancomycin is modified on the inner wall of the capillary to construct a capillary coating separation system. The highlight of the coated capillary is that it has both anti-protein adsorption and chiral separation properties. Compared with the bare capillary or non-covalently bonded DR/vancomycin-coated capillary, it can not only achieve the separation of four mixed proteins of lysozyme (Lys), bovine serum albumin (BSA), myoglobin (Mb), and ribonuclease A (RNase A), but also shows excellent performance in chiral drugs. The coated capillary effectively solves the problems of low efficiency of the separation column and high sample loss and provides ideas for the development of coated capillaries in the future.

The mechanism for inhibition of [FeFe]-hydrogenases by formaldehyde is examined with model complexes. Key findings: (i) CH2 donated by formaldehyde covalently link Fe and the amine cofactor, blocking the active site and (ii) the resulting Fe-alkyl is a versatile electrophilic alkylating agent. Solutions of Fe2[(μ-SCH2)2NH](CO)4(PMe3)2 (1) react with a mixture of HBF4 and CH2O to give three isomers of [Fe2[(μ-SCH2)2NCH2](CO)4(PMe3)2]+ ([2]+). X-ray crystallography verified the NCH2Fe linkage to an octahedral Fe(ii) site. Although [2]+ is stereochemically rigid on the NMR timescale, spin-saturation transfer experiments implicate reversible dissociation of the Fe–CH2 bond, allowing interchange of all three diastereoisomers. Using 13CH2O, the methylenation begins with formation of [Fe2[(μ-SCH2)2N13CH2OH](CO)4(PMe3)2]+. Protonation converts this hydroxymethyl derivative to [2]+, concomitant with 13C-labelling of all three methylene groups. The Fe–CH2N bond in [2]+ is electrophilic: PPh3, hydroxide, and hydride give, respectively, the phosphonium [Fe2[(μ-SCH2)2NCH2PPh3](CO)4(PMe3)2]+, 1, and the methylamine Fe2[(μ-SCH2)2NCH3](CO)4(PMe3)2. The reaction of [Fe2[(μ-SCH2)2NH](CN)2(CO)4]2− with CH2O/HBF4 gave [Fe2[(μ-SCH2)2NCH2CN](CN)(CO)5]− ([4]−), the result of reductive elimination from [Fe2[(μ-SCH2)2NCH2](CN)2(CO)4]−. The phosphine derivative [Fe2[(μ-SCH2)2NCH2CN](CN)(CO)4(PPh3)]− ([5]−) was characterized crystallographically., The mechanism for inhibition of [FeFe]-hydrogenases by formaldehyde is examined with model complexes.

It is a pre-requisite to ionize analyte molecules efficiently for detection by laser desorption/ionization mass spectrometry. Here, we report a conceptual demonstration of cationizing neutral small molecules which are typically difficult to be ionized with the traditional organic matrices due to their low proton/cation affinity values. Our strategy features generating radical cations from site-specifically carboxylated 10-(4-carboxyphenyl)-10H-phenothiazine-3,7-dicarboxylic acid (PTZ(A)2-Ph(A)) with a laser, and anchoring the chlorine ion from NaCl through covalent bond-like bridging interactions with the N/S atoms in the heterocyclic structure. This “Maverick” design allows a dramatic change of the energy landscape of analyte sodiation with an enhanced efficiency. We have synthesized two families of compounds based on the model structures of phenothiazine (PTZ) and phenoxazine (PXZ) and their carboxylated derivatives, and performed comparison between them or against the traditional organic matrices in a systematic format. We have demonstrated that PTZ(A)2-Ph(A) is outstanding as a novel MALDI matrix for the detection of oligosaccharides and amino acids, with an ultra-clean background baseline and high signal-to-noise ratios (up to dozens of times better than the traditional matrices). This work provides a new method for the cationization of neutral small molecules in a distinct mechanism, inspiring the development of next-generation matrices for sensitive detection of hard-to-be-ionized molecules by MALDI MS.