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Membrane separation technique has been widely used in recent years for oily wastewater treatment because of the advantages of simplicity of operation, lack of residual contamination and high separation efficiency. However, membrane fouling and pore plugging can cause serious problems, such as short membrane life and decreased flux. Therefore, in this paper, a self-cleaning polyacrylonitrile (PAN) composite membrane with excellent oil–water emulsion separation properties was prepared. The PAN membrane modified with AgI/UiO-66-NH2 was first prepared using electrospinning. The zwitterionic poly(sulfobetaine methacrylate) (pSBMA) was then modified onto the prefabricated electrospinning membrane by atom transfer radical polymerization (ATRP) to prepare hydrophilic polymer brush grafted PAN/AgI/UiO-66-NH2 composite membranes after 2-bromoisobutyryl bromide (BiBB) was introduced to the composite membrane. The membrane possesses a self-cleaning capacity because AgI/UiO-66-NH2 has the ability of visible light driven catalytic degradation. The powerful hydration ability of the pSBMA and the surrounding water molecules enhance the wettability of the composite membrane. The existence of a photocatalyst and hydration of a zwitterionic polymer brush greatly improve the resistance of the membrane towards contamination. The as prepared membrane was used to treat oil/water emulsions and the results revealed that the membrane has high permeability to four kinds of different oil/water emulsions when driven by gravity. The mentioned membrane might have potential application prospects in oily water treatment. [ABSTRACT FROM AUTHOR]

Thread-based microfluidic colorimetric sensors have been deemed a potential tool that may be incorporated into textiles for non-invasive sweat analysis. Nevertheless, their poor performance significantly limits their practical uses in sweat glucose detection down to 20 μM. Herein, a microfluidic glucose sensing device containing a salt-responsive thread is developed for the highly sensitive detection of glucose in human sweat. By grafting a zwitterionic polymer brush—which could react to ionic strength by changing the conformation of the polymer chains from the collapsing state to the stretching state—onto the cotton thread, the salt-responsive thread was created. Compared to the pristine cotton thread, the modified thread has better ion-capture capabilities, a more noticeable swelling effect, and a higher ability to absorb water. These enable a significant enrichment of glucose when the saline solution passes through it. The salt-responsive thread was employed to construct a thread/paper-based microfluidic sensing device for the monitoring of glucose in artificial sweat, exhibiting a sensitivity of −0.255 μM−1 and a detection limit of 14.7 μM. In comparison to the pristine cotton thread-based device, the performance is significantly superior. Using a hydrophobic fabric and salt-responsive threads, a glucose-sensing headband was prepared for on-body sweat glucose monitoring. With the use of a smartphone-based image analysis system, the headband can detect the concentration of glucose in a volunteer's perspiration. Using the thread-based salt-responsive zwitterionic polymer brush might offer a novel approach to creating wearable sweat sensors with extremely high sensitivity. [ABSTRACT FROM AUTHOR]

Highly sensitive and selective choline microbiosensors were constructed by microcontact printing (μCP) of choline oxidase (ChOx) in a crosslinked, polyamine-functionalized zwitterionic polymer matrix on microelectrode arrays (MEAs). μCP has emerged as a potential means to create implantable, multiplexed sensor microprobes, which requires the targeted deposition of different sensor materials to specific microelectrode sites on a MEA. However, the less than sufficient enzyme loading and inadequate spatial resolution achieved with current μCP approaches has limited adoption of the method for electroenzymatic microsensors. A novel polymer, poly(2-methacryloyloxyethyl phosphorylcholine)-g-poly(allylamine hydrochloride) (PMPC-g-PAH), has been developed to address this challenge. PMPC-g-PAH contributes to a higher viscosity “ink” that enables thicker immobilized ChOx deposits of high spatial resolution while also providing a hydrophilic, biocompatible microenvironment for the enzyme. Electroenzymatic choline microbiosensors with sensitivity of 639 ± 96 nA μM−1 cm−2 (pH 7.4; n = 4) were constructed that also are selective against both ascorbic acid and dopamine, which are potential electroactive interfering compounds in the mammalian brain. The high sensitivities achieved can lead to smaller MEA microprobes that minimize tissue damage and make possible the monitoring of multiple neurochemicals simultaneously in vivo with high spatial resolution. [ABSTRACT FROM AUTHOR]

The document is a contents list for an issue of the journal Chemical Communications, published by The Royal Society of Chemistry. It provides information about the editorial staff, subscription details, and the editorial board of the journal. The document also includes instructions for authors who wish to submit material for publication, as well as guidelines for reproducing published contributions. The contents list features articles on various topics in chemistry and materials science, such as the atmospheric transformation of organosulfates and charge carrier dynamics in lead halide perovskites. The document concludes with comments and replies related to a previous publication in the journal. [Extracted from the article]

A novel copolymer containing zwitterionic and methylsulfinyl structures was developed, which enhanced cryoprotective efficacy by enabling intracellular cytoplasmic permeation without relying on mediated endocytosis and diffused out of the cells within approximately 30 min, making it more advantageous than polymeric nanoparticles for the transport of membrane-impermeable cryoprotectants such as trehalose. [ABSTRACT FROM AUTHOR]

A strategy through the combination of a polyzwitterion matrix, salt mixture, and interfacial organic solvent layer is proposed to achieve an improvement in the performance of gel polymer electrolyte-based quasi-solid-state electrical double-layer capacitors by modulating the properties of the electrolytes from bulk to interfaces. [ABSTRACT FROM AUTHOR]

In this study, we synthesized and characterized a zwitterionic polymer based on the 4-vinylpyridine monomer (4-VP) and used it as a practical drug carrier for 5-fluorouracil (5-FU). Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FE-SEM), gel permeation chromatography (GPC) and zeta potential analysis were conducted to investigate the molecular interactions, morphology, molecular weight, and surface charge, respectively. The GPC findings showed the weight average molecular weight of 64.5 kDa for poly(4-VP). Using ethyl bromoacetate in a basic medium, the zwitterion poly(4-VP), abbreviated as ZVP, was obtained and showed a different morphology, medium weight average molecular weight, and increased negative surface charge (-17 mV) as compared to poly(4-VP). Moreover, the ZVP nanoparticles (NPs) illustrated a mean size of 76 nm, polydispersity index of 0.25 and ultimate 5-FU cumulative release of 55% with a first-order kinetic model. The in vivo results showed that the percentage of neutrophils over time in ZVP NPs was lower than 5-FU, indicating the reliable potential of the ZVP coating for the enhancement of the drug circulation time in blood with long-term stability for medical applications. [ABSTRACT FROM AUTHOR]

Polyanion-type Na3V2(PO4)2F3 (NVPF) represents a new potential cathode material due to its sodium super ionic conductor (NASICON) structure. However, unmodified Na3V2(PO4)2F3 is restricted by its intrinsic properties, and its limitation of poor conductivity make it an unsatisfactory cathode material. Herein, a zwitterionic polymer is used as a new nitrogen and sulfur source to successfully synthesize nitrogen and sulfur co-doped carbon-coated Na3V2(PO4)2F3 (NVPF-NSC) through a sol–gel method combined with freeze-drying technology. The obtained three-dimensional framework both alleviates agglomeration between particles and improves the electrical conductivity and electrochemical performance of the material. Based on these advantages, NVPF-NSC-2 (the zwitterionic polymer was added at 25% of NVPF mass) exhibits a high specific discharge capacity (109 mA h g−1 at 0.5 C) and excellent cycle performance (with a capacity retention ratio of 92.1% after 500 cycles at 5 C and a capacity retention ratio of 87.6% after 500 cycles at 10 C with a retained capacity of 83 mA h g−1). Ex situ X-ray diffraction (ex-XRD) tests were performed to explore the charge/discharge deintercalation mechanism of Na+, with the results demonstrating the excellent cycle stability of the material. The results reported herein demonstrate that using zwitterionic polymers as a new heteroatom source is feasible and effective, providing a new idea for the future large-scale application of sodium ion batteries. [ABSTRACT FROM AUTHOR]

Biofouling is a serious problem in the medical, marine, and all other industrial fields as it poses significant health risks and financial losses. Therefore, there is a great demand for endowing surfaces with antifouling properties to mitigate biofouling. Zwitterionic polymers (containing an equimolar number of homogeneously distributed anionic and cationic groups on the polymer chains) have been used extensively as one of the best antifouling materials for surface modification. Being a superhydrophilic polymer, zwitterionic polymers need a strong binding agent to continue to remain attached to the surface for long-term applications. The use of a mussel-inspired dopamine adhesive functional layer is one of the most widely exploited approaches for the attachment of a zwitterion layer on the surface via thiol and amine chemistry. Based on recent studies, we have categorized this dopamine and zwitterion conjugation into four different approaches: (1) conjugation of dopamine with zwitterions by direct modification of zwitterions with the dopamine functional moiety; (2) co-deposition of dopamine with zwitterionic polymers; (3) zwitterionic post modification of the polydopamine (PDA) coated surface; and (4) surface-initiated polymerization of zwitterionic polymers using dopamine modified initiators. In this review, we have briefly discussed about all the possible conjugation mechanisms and reactions for this promising dopamine and zwitterion conjugation and how this conjugated system significantly contributes to the development of non-fouling surfaces along with the other applications. [ABSTRACT FROM AUTHOR]

Current olivine structure LiFePO4 possesses poor conductivity, which makes it unsuitable for unparalleled battery applications. This issue can be solved by improved design concepts of binder systems. Herein, an original waterborne binder polymer with efficient functional groups is designed and fabricated for LiFePO4 cathodes of lithium-ion batteries (LIBs). Compared to universal lithiated ionomer binders, the introduction of the zwitterionic structure of the ionomer enhances the ionic conductivity by nearly 100-fold. LiFePO4 cathodes assembled with limited 1.5 wt% lithiated zwitterionic ionomer (LZI) maintain markedly stable cycling performances with 95.62% retention at 1C after 250 cycles. Also, LZI-cathodes preserve good integrity structures after cycling, as confirmed by morphology analysis. In sum, LZI-cathodes look promising for potential applications in LIBs due to their numerous advantageous characteristics. [ABSTRACT FROM AUTHOR]

Polyphenols containing catechol (1,2-dihydroxyphenyl)/pyrogallol (1,2,3-trihydroxyphenyl) groups have been employed as precursors to prepare substrate-independent (i.e., universal) coatings. However, quercetin, an interesting flavonol due to its unique biological properties, was previously found to be an inefficient compound for substrate coatings after screening polyphenolic compounds. We report that quercetin-based thin films could be formed on various substrates, including titanium dioxide, silicon wafers, gold, nylon, and glass, when diethylenetriamine (DETA) was used as an additive. DETA acted as a cross-linker to facilitate conjugate addition and imine formation with the catechol in quercetin. The film thickness was controllable by changing the quercetin concentration. Static water contact angles for all examined substrates converged to 25° regardless of the vastly different static water contact angles of the bare substrates, showing the universal coating capability of quercetin and DETA. Importantly, the films formed with quercetin and DETA were chemically modifiable; thus, specific functions on the surface could be introduced. α-Bromoisobutyryl bromide was immobilized on the films via esterification, and then a zwitterionic sulfobetaine polymer was subsequently grafted. Compared to the controls, the polymer-grafted surface effectively suppressed the adsorption of fibrinogen and platelets, demonstrating its non-biofouling effect. Considering its universal coating and postfunctionalization capabilities, this quercetin-based film provides a route for the preparation of functional organic coatings. [ABSTRACT FROM AUTHOR]

In order to reduce the enzyme cost of lignocellulosic enzymatic hydrolysis, upper critical solution temperature (UCST) additives are used to recover and reuse cellulase by regulating the temperature. A sulfobetaine polymer, PSPE, showed a sensitive UCST response in buffer, and its UCST-performance was optimised by adjusting the molecular weight of the polymer. PSPE-3 (Mw = 355.1 kDa) was added to the cellulase buffer at 50 °C, and PSPE-3 and cellulase were co-precipitated by cooling to the room temperature of 25 °C. PSPE-3 and cellulase co-precipitated mainly through hydrophobic interactions via cooling. Compared with octadecyl sulfobetaine (SB3–18), PSPE-3 had a more sensitive UCST response and stronger cellulase recovery ability. Adding only 40% PSPE-3 (accounting for the mass fraction of cellulase) can save more than 50% cellulase in the enzymatic hydrolysis system of eucalyptus chips pre-treated with dilute acid (Eu-DA). However, for the Eu-DA system, adding 100% SB3–18 can only save about 30% of cellulase. In this work, efficient recycling of cellulase was achieved at room temperature by adding UCST-type PSPE. The process is green without consuming acid and alkali, and this work provides a new idea for reducing the production cost of cellulosic ethanol. [ABSTRACT FROM AUTHOR]

A zwitterionic polymer containing a hydrophobic long chain, named MANPS, was independently developed by free radical solution polymerization. The introduction of an hydrophobic long-chain monomer, namely, octadec-9-enioc acid allylamide (NAE) and an amphoteric ionic monomer, i.e., 3-(3-methylacrylamide propyl dimethylamino)-propyl-1-sulfonate (MEPS) in conventional acrylamide (AM) and acrylic acid (AA) enhanced the rheological properties of polymer flooding agents, thereby improving their temperature resistance and salt tolerance. A series of experiments were performed to determine the optimal reaction conditions for the polymer; the structure and molecular weight characteristics of MANPS were confirmed by FT-IR spectroscopy, 1H NMR spectroscopy, intrinsic viscosity, high-performance liquid chromatography (HPLC) and SEM. The rheological test results showed that MANPS had higher apparent viscosity than the partially hydrolyzed polyacrylamide (HPAM). It exhibited good shear recovery at a certain shear rate. The reason was considered to be the long-chain entanglement of molecules and the "anti-polyelectrolyte action" of zwitterions. Thermogravimetric analysis provided good evidence of the thermal properties of the copolymer MANPS. Evaluating the oil displacement performance of the oil-displacing agent was an essential part. The results showed that the copolymer MANPS was comparable to HPAM having a 10.4% higher oil displacement rate under the same concentration and test conditions. [ABSTRACT FROM AUTHOR]

A facile and scalable polyzwitterion–polydopamine coating strategy has been developed to functionalize substrates and sponges. This approach, for the first time, achieves superior regenerable underwater self-cleaning of stubborn asphaltenes-containing heavy oil fouling without pre-hydration and removal of water residues from heavy oil, with significant implications in many engineering and environmental processes. [ABSTRACT FROM AUTHOR]

The regioselective insertion of DDQ into a C–H bond of the 6π + 6π electron zwitterionic benzoquinonemonoimines 4a–c results in the formation of novel chiral C-substituted quinoid ligands 11a–c. These Michael adducts feature a preserved zwitterionic form and a quaternary stereogenic carbon center as evidenced by the single crystal X-ray structure of the derivative 11a. The ECD spectra, optical rotations and racemization barriers of the two enantiomers of 11a were measured subsequently to their separation using preparative chiral HPLC. Because the racemization of 11a is stopped in basic media, compounds 11a–c give a new entry in chiral zwitterionic bridging ligands. [ABSTRACT FROM AUTHOR]

In this study, nano-hydroxyapatite crystals (nHAs) were prepared in the presence of zwitterionic poly(3-carboxy-N,N-dimethyl-N-(3′-acrylamidopropyl) propanaminium inner salt) (PCBAA) at different concentrations and pH microenvironments, denoted as Z-nHAs. The phase, morphology, size of apatite, and interactions between nHAs and PCBAA were systemically characterized via XRD, TEM, FTIR, and TGA. The results showed that Z-nHAs could be formed at all pH ranges in the presence of PCBAA in our experiment. It was different from the case of pure nHAs that could not be formed under an acidic microenvironment without PCBAA. In addition, a higher pH value was beneficial for the formation of nHAs with a smaller size. Z-nHAs exhibited a fiber-like structure at the initial 2 h and became rod-like in shape after 5 h, whereas pure nHAs prepared in water had an irregular flake-like structure. Moreover, 14–20% PCBAA could be incorporated into Z-nHAs via interactions between the quaternary ammonium group (–R3N+) and carboxyl group (–COO−) in the PCBAA chain and Ca2+/PO43− of nHA. A possible mechanism for the formation of Z-nHAs in the presence of PCBAA was proposed based on the experimental results. [ABSTRACT FROM AUTHOR]

Herein, a novel water-soluble comb-shaped polyzwitterion (PNMASt) was prepared by introducing N-maleoyl chitosan, 2-(dimethyl(5-methyl-4-oxohex-5-en-1-yl)ammonio)ethyl sulfite, and other hydrophilic hydrophobic monomers into HPAM via free-radical copolymerization. Chemical structure determination and heat endurance analysis were accomplished via XRD, FTIR and 1H-NMR spectroscopy, SEM, and TGA. A simulated reservoir environment (shear rates, temperature, and salinity) was used to survey the solution performance and the rheology of the polyzwitterion as a function of the apparent viscosity and changing conditions. PNMASt exhibited excellent thickening efficiency, surface activity, anti-shear behavior, restorable action after shearing, heat tolerance, ageing tolerance, viscoelasticity, and salt tolerance as compared to HPAM under the same simulation environment. Furthermore, a core flooding experiment showed the remarkable flow control capability (Rf = 18.23 and RRf = 6.62), excellent oil production enhancement (13.32%), and remarkable residual oil displacement capacity (6.11%) of PNMASt as compared to those of HPAM. [ABSTRACT FROM AUTHOR]

Zwitterionic 4-vinylpyridine-based polymers were immobilized on different surfaces by a self-assembled monolayer (SAM) formation technique for better durability and reliability. Atomic force microscopic studies revealed dense polymeric brushes with a high degree of smoothness. A large variation in water contact angle was observed when the surface was treated with buffers of different pH, indicating a tunable hydrophilicity of the polymeric brush. The contact angle variation was observed under both acidic and basic media, possibly due to the presence of both quaternary ammonium groups and carboxylic acid functionality. Interestingly, a time-dependent contact angle variation under different pH was observed when the polymer was directly coated on the leather surface. [ABSTRACT FROM AUTHOR]

Polymorphic compounds {[Cu(dcbb)2(H2O)2]·10H2O}n (2, 1D chain), [Cu(dcbb)2]n (3, 2D layer) and their co-crystal {[Cu(dcbb)2(H2O)][Cu(dcbb)2]2}n (4) have been prepared from the coordination reaction of a 2D polymer [Na(dcbb)(H2O)]n (1, H2dcbbBr = 1-(3,5-dicarboxybenzyl)-4,4′-bipyridinium bromide) with Cu(NO3)2·3H2O at different temperatures in water. Compounds 2–4 have an identical metal-to-ligand stoichiometric ratio of 1 : 2, but absolutely differ in structure. Compound 3 features a 2D layer structure with aromatic rings, positively charged pyridinium and free carboxylates on its surface, promoting electrostatic, π-stacking and/or hydrogen-bonding interactions with the carboxyfluorescein (FAM) labeled probe single-stranded DNA (probe ss-DNA, delineates as P-DNA). The resultant P-DNA@3 system facilitated fluorescence quenching of FAM via a photoinduced electron transfer process. The P-DNA@3 system functions as an efficient fluorescent sensor selective for HIV double-stranded DNA (HIV ds-DNA) due to the formation of a rigid triplex structure with the recovery of FAM fluorescence. The system reported herein also distinguishes complementary HIV ds-DNA from mismatched target DNA sequences with the detection limit of 1.42 nM. [ABSTRACT FROM AUTHOR]

Compact polymerized polydiacetylene-micelles with “stealth” zwitterionic surface coating were assembled and tested in a murine xenograft model of breast cancer. In vivo fluorescence imaging indicated accumulation in the tumor area and histological studies revealed predominant uptake of the micelles at the margins of the tumor, thereby allowing the delineation of its volume. [ABSTRACT FROM AUTHOR]

Surface modification and endothelialization of vascular biomaterials are common approaches that are used to both resist the nonspecific adhesion of proteins and improve the hemocompatibility and long-term patency of artificial vascular grafts. Surface modification of vascular grafts using hydrophilic poly(ethylene glycol), zwitterionic polymers, heparin or other bioactive molecules can efficiently enhance hemocompatibility, and consequently prevent thrombosis on artificial vascular grafts. However, these modified surfaces may be excessively hydrophilic, which limits initial vascular endothelial cell adhesion and formation of a confluent endothelial lining. Therefore, the improvement of endothelialization on these grafts by chemical modification with specific peptides and genes is now arousing more and more interest. Several active peptides, such as RGD, CAG, REDV and YIGSR, can be specifically recognized by endothelial cells. Consequently, graft surfaces that are modified by these peptides can exhibit targeting selectivity for the adhesion of endothelial cells, and genes can be delivered by targeting carriers to specific tissues to enhance the promotion and regeneration of blood vessels. These methods could effectively accelerate selective endothelial cell recruitment and functional endothelialization. In this review, recent developments in the surface modification and endothelialization of biomaterials in vascular tissue engineering are summarized. Both gene engineering and targeting ligand immobilization are promising methods to improve the clinical outcome of artificial vascular grafts. [ABSTRACT FROM AUTHOR]

Nacre-mimetic materials are of great interest, but difficult to synthesize, because they require the ordering of organic and inorganic materials on several length scales. Here we introduce peptoid nanosheets as a versatile two-dimensional platform to develop nacre mimetic materials. Free-floating zwitterionic nanosheets were mineralized with thin films of amorphous calcium carbonate (of 2–20 nm thickness) on their surface to produce planar nacre synthons. These can serve as tunable building blocks to produce layered brick and mortar nanoarchitectures. [ABSTRACT FROM AUTHOR]

A new electrochemical label has been developed, which is made up of silver nanoparticles (AgNPs) coated with a mixture of zwitterionic and biotinylated zwitterionic polymers. These polymers improve colloidal stability in physiological medium and ensure biorecognition while direct electrochemical oxidation of silver nanoparticles strongly enhances the detection signal. The resulting hybrid nanomaterials are used as labels in the electrochemical sensing of avidin using sandwich assays elaborated using the biotin-avidin biorecognition system. [ABSTRACT FROM AUTHOR]

A novel strategy was achieved to make ultra-stable core-shell nanoparticles directly from nonfouling zwitterionic polymers through a one-step microwave method. The resulting nanoparticles showed superior colloid stability in bio-relevant media and even under freeze-drying conditions. [ABSTRACT FROM AUTHOR]

Mechanically strong supramolecular hydrogels (up to 98.9% water content) were obtained by the combination of a rigid, fully π-conjugated polymer backbone and zwitterionic side chains. The gels were characterized by SAXS, SEM and rheology measurements and are fluorescent, stimuli responsive (temperature, salts) and bind DNA. [ABSTRACT FROM AUTHOR]

A novel type of zwitterionic fluorescent nanoparticles (ZFNPs) containing polysulfobetaine groups, the boron dipyrromethane (BODIPY) fluorophore and graphene oxide plates is prepared for the detection of tumor cells in response to the intra- and extracellular stimuli. The fluorescence intensities of the ZFNPs are highly influenced by temperature and pH. [ABSTRACT FROM AUTHOR]

A mild, efficient and ambient temperature photochemical approach for the synthesis of silver nanoparticle core–shell structures employing a zwitterionic polymer as well as polyethylene glycol is presented. [ABSTRACT FROM AUTHOR]

The stimuli-responsive macrocycles are smart materials of high interest. Crown ethers with the ring frameworks enlarged with one and two spiropyran units were synthesized in this work, whose ring conformation, ring sizes and charge states could be responsively altered. The cyclic spiropyran derivatives changed from neutral SP form to zwitterionic ME form at pH ＜ 7. The cyclic spiropyran derivatives in either SP or ME form formed stable Langmuir monolayers on the water surface. The monolayer of cyclic spiropyran derivatives in the SP form showed recognition of specific metal ions according to analysis of the surface pressure–molecular area isotherms, whereas the cyclic spiropyran derivatives in ME form lost the ability of specific recognition based on size-fitting complexation. The stimuli-responsive macrocycles hold promising potential to act as responsive molecular gates and catalysts, to mimic ion channels of bio-membranes, etc. [ABSTRACT FROM AUTHOR]

A series of novel β-diketone ligands bearing alkyloxyphenyl R = C6H4OCnH2n+1and pyridyl substituents at 1 and 3 positions of the β-diketone core [HLR(n)py] have been prepared and structurally characterized. The corresponding β-diketonate complexes [Pd(κ2-LR(n)py)2] were isolated as a mixture of cisand transisomers each of them exhibiting the ligand in a NO- or OO-bidentate coordinative mode which were established by multinuclear NMR studies (1H, 13C and 15N). However none of those characteristics were determining to achieve liquid-crystalline properties on the new complexes. By contrast reactions of the aforementioned ligands [HLR(n)py] or those containing the pyridiniumyl substituent [HLR(n)pyH]+towards the allyl–palladium fragment were successful to afford ionic metallomesogenic materials isolated as PF6salts of [Pd(η3-C3H5)(κ2-HLR(n)py)][PF6] (I) and [Pd(η3-C3H5)(κ2-LR(n)pyH)][PF6] (II) types. Structural characterization and mesomorphic properties were established by multinuclear NMR and the use of DSC and POM techniques. In complexes Iand IIthe corresponding β-diketone ligands were coordinated as neutral bidentate NO-donor or zwitterionicOO-donor systems, respectively. Complexes of type IIexhibit a range of the SmC mesophases significantly greater than that found in the type I. [ABSTRACT FROM AUTHOR]

Three-component reaction of the zwitterion generated from dialkyl acetylenedicarboxylate and an alkyl or aryl isocyanide with an alkyl or aryl sulfonamide is described. The reaction afforded the corresponding special type of ketenimine sulfonamide derivatives in water without using any activation and modification. The products could be easily hydrolyzed to the corresponding sulfonamide-butanamide derivatives at 80 °C in good yields without using a catalyst. [ABSTRACT FROM AUTHOR]

Three isostructures [C16H8O4·2(CH6N3)·4(H2O)] (1), [C16H10O4·2(CH6N3)·4(H2O)] (2) and [C14H8N2O4·2(CH6N3)·4(H2O)] (3) were prepared by the complexation of guanidinium with 4,4′-(ethyne-1,2-diyl)dibenzoic acid, 4,4′-(ethene-1,2-diyl)dibenzoic acid and 4,4′-(diazene-1,2-diyl)dibenzoic acid, respectively. The strong charge-assisted +N–HO−hydrogen bonds cause the assembly of guanidinium and these different acids following almost the same procedure. The hydrogen-bonded water wire is incorporated in zwitterionic channels of organic salts. [ABSTRACT FROM AUTHOR]

Three compounds, each derived from Fentanyl and differing essentially only in the length of a carboxylic acid chain, were synthesized and yielded four crystal structures three of which share several structural similarities, including the length of the chain, while the fourth, with a shorter chain, is quite different. The chain length has a significant influence on the crystal structures formed. The ‘three atom’ chain compounds are all solvated zwitterions which feature a hydrogen-bonded ‘dimer’ between adjacent zwitterions. The formation of this large dimer leaves available a second carboxylate O atom to take part in hydrogen bonding interactions with solvent molecules. The shorter ‘two atom’ chain compound was difficult to crystallize and required the use of synchrotron radiation to measure X-ray diffraction data. It does not form the same dimer motif observed in the ‘three atom’ chain compounds and has not formally formed a zwitterion; although there is evidence of proton sharing or disorder X-ray data are insufficient to create a disordered model, and the compound was modeled as formally neutral based on O–H and N–H distances. Room temperature analyses showed the proton transfer behavior to be independent of crystal temperature, and nuclear magnetic resonance studies show proton transfer behavior in solution. The formation of a zwitterionic hydrogen-bonded dimer is implicated in providing some stability during crystal growth of the easily crystallized ‘three atom’ chain compounds. [ABSTRACT FROM AUTHOR]

Two rare three-component polymorphs have been prepared that adopt different molecular recognition models: brick-wall and herringbone frameworks. Both the polymorphs also exhibit an interesting inclusion phenomenon wherein the guest molecules are in fact ion pairs. The crystal structure of 3, on the other hand, represents a unique inclusion feature of encapsulation of a zwitterion. [ABSTRACT FROM AUTHOR]

We compare the response of the crystalline dl-cysteine to cooling and to increasing pressure. The structure undergoes a low-temperature phase transition into an isosymmetric polymorph, dl-cysteine-II, with the conformation of zwitterion changing from gauche− to gauche+. The first pressure-induced transition at 0.1 GPa (the lowest pressure reported for a phase transition in a crystalline amino acid thus far) gives the same polymorph. Further compression of dl-cysteine-II proceeds differently on cooling and with increasing hydrostatic pressure. dl-cysteine-II is preserved down to 3 K, but undergoes phase transitions on compression at about 1.55 GPa, and 6.20 GPa. The changes in the hydrogen bond network preceding the phase transition in dl-cysteine-II in the range 0.25–0.85 GPa differ from those observed on cooling the same structure, but resemble those preceding pressure-induced phase transitions in β- and γ-glycine. [ABSTRACT FROM AUTHOR]

l-Alanine crystallises as a zwitterion in space group P212121at ambient pressure. The strongest intermolecular interactions are three N–HO hydrogen bonds. The H-bonds link the molecules into puckered layers in the acplane, which are then stacked along the baxis. PIXEL calculations indicate that the H-bond mediated intermolecular energies within the layers are 118 and 145 kJ mol−1, while the stacking interactions are considerably weaker (31 kJ mol−1). Neutron powder diffraction data on l-alanine-d7to 9.87 GPa show that the effects of pressure are most prominent along a, the direction which is least well aligned with the H-bonds. The aaxis decreases in length more rapidly than the caxis, and the two axis lengths are equal at ca.2 GPa. Although the structure is metrically tetragonal at this point, the true symmetry is still orthorhombic. In fact, the structure remains in a compressed form of its starting orthorhombic phase throughout the pressure range studied, in contradiction of previous Raman and energy dispersive power diffraction studies, in which data were interpreted in terms of phase transitions at ca.2 GPa and 9 GPa. It is likely that the spectroscopic signature of the apparent transition at 2 GPa is the result of a conformational change at the ammonium group. The molecular coordination number in l-alanine is 14, and the packing topology is a distorted form of body-centred cubic at ambient pressure. As pressure increases this topology becomes more regular, until at 9.87 GPa it is very similar to the perfect BCC topology of a structure such as tungsten. It is suggested that this behaviour can be traced to the sphericity of the alanine molecule. [ABSTRACT FROM AUTHOR]

3-Dialkylaminomethyl substituted salicylaldoximes are efficient metal saltextractants, and, in contrast to related “salen”-based reagents, are sufficiently stable to acid hydrolysis to allow commercial application in base metal recovery. Crystal structures show that metal salts are bound by a zwitterionic form of the reagents, with copper(II) nitrate, tetrafluoroborate and trifluoroacetate forming [Cu(L)2X2] assemblies in a tritopic arrangement with a trans-disposition of the anions outwith the coordination sphere. Copper(II) chloride, bromide and zinc(II) chloride form 1:1 assemblies, [Cu(L)X2], with the halides in the inner coordination sphere of the metal, leading to high chloride selectivity and very good mass transport efficiencies of CuCl2. Introduction of the anion-binding sites into the salicylaldoxime extractants changes their cation selectivities; the ligands co-extract small amounts of FeIIIalong with CuIIfrom mixed metal aqueous feed solutions, an issue which will need to be addressed prior to industrial application. [ABSTRACT FROM AUTHOR]

As a diene, 2-methoxyfuran fails to generate a Diels–Alder adduct when it reacts with β-cyanostyrenes (cinnamonitriles). However, in the reaction with β-cyanostyrenes possessing additional electron-withdrawing groups (CN, CO2Et and SO2Ph), it yielded two new phenylcyclopropanes. We have used computational methods to investigate the mechanism and to probe the regioselectivity observed in the rearrangement reactions. We used a B3LYP/6-31G* level density functional calculation to locate the transition states (TS), and to account for the selectivity observed in these reactions, we examined the global electronic index involved. An analysis of the results for the reaction pathways of two adducts (the endoand exoisomers) shows that the reaction takes place viaa polar stepwise mechanism. The first step involves a side-on nucleophilic attack by the α-carbon atom of the furan ring on the vinyl carbon of the cyanostyrene to give a zwitterionic intermediate. An intramolecular substitution within the intermediate (IN) gives the cyclopropane ring, together with fission of the furan ring. The potential energy barriers for these reactions had the following values: at the nucleophilic addition step, 14.6 and 13.7 kcal mol−1for 2b, and 18.4 and 17.8 kcal mol−1for 2c; at the rearrangement step, 22.3 and 22.8 kcal mol−1for 2b, and 25.1 and 23.1 kcal mol−1for 2c. Solvent effects in chloroform stabilized the rearrangement steps by 5–6 kcal mol−1, but the nucleophilic addition step appeared to be slightly affected. From the theoretical results, in the case of 2b, the energy of TS2-endois lower than that of TS2-exo, so more trans-cyclopropane product from the endoform is formed under kinetic conditions. Conversely, in the case of 2c, the energy of TS2-exois lower and more of the cis-product is formed. Density functional theory analysis of these reactions is in complete agreement with the experimental results. [ABSTRACT FROM AUTHOR]

A series of classical B(C6F5)3-phosphine adducts are shown to be reactive molecules. Reaction of (THF)B(C6F5)3 with phosphines are shown to effect ring-opening of THF affording the zwitterionic phosphonium-borate species of the form R2PH(C4H8O)B(C6F5)3 and R3P(C3H8O)B(C6F5)3. Alternatively, treatment of (THF)B(C6F5)3 with a lithium phosphide (R2PLi, R = tBu, Ph Mes) affords species of the form [Li(THF)x][R2P(C4H8O)B(C6F5)3]. Additionally, double THF ring-opening is also demonstrated to give species of the form [Li(THF)x][R2P(C4H8OB(C6F5)3)3]. In addition a series of classical borane-phosphine adducts are also shown to undergo thermal rearrangement reactions to give the zwitterionic products of aromatic substitution R2PH(C6F4)BF(C6F5)2 and R3P(C6F4)BF(C6F5)2. The mechanism of these substitutions is considered. A series of crystallographic studies of phosphine-borane adducts, THF ring-opened zwitterions and para-attack zwitterionic phosphonium borates are reported and discussed. [ABSTRACT FROM AUTHOR]

Metal-free hydrogenation of imines by phosphonium borate zwitterion R2PH(C6F4)BH(C6F5)2 (1, R = CH3, tBu), has been studied by density functional theory (DFT) calculations. The study elucidates a two-step mechanism in which protonation of an imine by the phosphonium part of 1 is followed by hydride transfer to the C center from the borohydride part of 1. According to our calculations, the hydride transfer indeed occurs separately from the protonation; furthermore, both transition states were found to have quite low activation energy. We predict a migration of an iminium ion along the P-B bridging C6F4 group between these two steps; the spatial separation between PH+ and BH- centers makes the concerted hydrogenation highly unlikely. The influence of the steric congestion of the P center of 1 on the transition state for protonation has been studied. Based on the thermodynamics for protonation of an imine and the corresponding amine by 1, the alternative reaction mechanism in which the protonation of an imine is mediated by the corresponding amine is discussed in the context of a complete catalytic cycle. All relevant intermediates and transition states are computationally characterized in this study at the B3LYP/6-31+G* level and relative energies are computed with the 6-31++G** basis; the comparison of relative energies of key reaction steps revealed good agreement between B3LYP, MPW1K and BHandHLYP density functional calculations. Solvent effects are included via the self consistent reaction field (SCRF/PCM) approach. [ABSTRACT FROM AUTHOR]

The reaction of EtNHC(S)Ph2PNP㸝(S)N−Et (HEtSNS) with [Ru3(CO)12] has been carried out under two different experimental conditions: in the first case [Ru3(CO)12], previously turned into the labile intermediate [Ru3(CO)10(CH3CN)2], afforded, at room temperature in dichloromethane, the trinuclear clusters [Ru3(CO)11(CNEt)] (1), {Ru3(CO)9(μ-H)[(μ-S:κ-P)Ph2PNPPh2C(S)NEt]} (2), {Ru3(CO)9(μ-H)[(μ-S:κ-P)Ph2PNP(S)Ph2]} (3) and {Ru3(CO)10[(μ-κ2P)Ph2PNHPPh2]} (4). Ligand fragmentation occurs vialoss of EtNC or EtNCS, without sulfur transfer to the cluster core. In the second case, [Ru3(CO)12] reacted with HEtSNSin toluene at 70 °C, giving the trinuclear clusters 4, {Ru3(CO)7(CNEt)(μ3-S)[(μ2-N:η1-C:κ1-P)Ph2PNPPh2C(H)NEt]} (5), {Ru3(CO)8)(μ3-S)[(μ2-N:η-C:κ-P)Ph2PNPPh2C(H)NEt]} (6) and {Ru3(CO)6(μ3-CO)(μ3-S)(EtNC)[(μ-κ2P) Ph2PNHPPh2]} (7). The last three compounds derive from ligand fragmentation and sulfur transfer to the metal cluster. All compounds were characterized by spectroscopy (NMR, IR) and the molecular structures of 2, 5and 7were determined by single-crystal X-ray diffraction. Cluster 2preserves the original Ru3triangular core in which an edge is bridged by a hydride ligand and by the sulfur atom of the Ph2PNPPh2C(S)NEt ligand. Cluster 5shows an open triangle of Ru atoms capped by a μ3-sulfide and by the unprecedented methideylamide –N(Et)CH(R)–μ3-bridging moiety of the Ph2PNPPh2C(H)NEt ligand. It formally derives from cluster 6by substitution of ethyl isonitrile with one CO molecule. Finally, cluster 7displays a Ru3(μ3-S)(μ3-CO) trigonal bipyramidal core. [ABSTRACT FROM AUTHOR]

Various types of multi-functional zwitterionic compounds containing both ester and sulfonate groups were prepared and their silver nitrate salts were tested as carriers for facilitated olefin transport membranes in the separation of ethylene–ethane and propylene–propane mixtures. Ester group-containing multi-functional zwitterionic silver compounds exhibited much higher performances in comparison with methyl group-containing zwitterionic compounds. A FT-IR study showed that ester-containing zwitterionic compounds interact with silver ions through both sulfonate and ester functional groups. [ABSTRACT FROM AUTHOR]

A simple, one-pot method is presented whereby gold nanoparticles coated with a zwitterionic diblock copolymer are incorporated within single crystals of calcite. This may provide a versatile alternative to dyeing crystal with organic molecules and could be extended to create a series of new nanocomposite crystals with novel properties. [ABSTRACT FROM AUTHOR]

New vinylbenzene substituted imidazole based zwitterionic polymers with unique characteristics like swelling in water and solubility in concentrated brine solution in which they exhibited a reversible upper critical solution temperature (UCST) and gel-sol transitions are reported herein. [ABSTRACT FROM AUTHOR]

The synthesis of the first members of a new class of cyclic peptide-containing hemicryptophanes is described. Synthesis was achieved through attachment of veratryl groups to the l-tyrosine side chains of a cyclic hexapeptide, c(YG)3, followed by intramolecular cyclodehydration to generate the CTV unit. The diastereomeric P- and M-hemicryptophanes were generated in a 2 : 1 ratio and were separated by chromatography. The enantioselective binding properties of the hemicryptophanes were investigated by complexation with carnitine. Both isomers were found to have significant selectivity for binding (R)-carnitine. [ABSTRACT FROM AUTHOR]

A solid hydrazine was isolated as a crystalline powder by reacting aqueous hydrazine with supercritical CO2. Its structure determined by single crystal X-ray diffraction shows a zwitterionic form of NH3+NHCO2−. The solid hydrazine is remarkably stable but is as reactive as liquid hydrazine even in the absence of solvents. [ABSTRACT FROM AUTHOR]

1-Ethyl-3-methylimidazolium leucine, a typical amino acid ionic liquid, turns into a thermotropic and ion conductive gel while retaining its ion pair upon adding a phosphonium-type zwitterion. [ABSTRACT FROM AUTHOR]

Charge-assisted hydrogen bond-directed self-assembly of a zwitterionic quinonemonoimine was investigated at the liquid/solid interface using scanning tunnelling microscopy. Factors governing morphology, chirality and multilayer formation are discussed, presenting an important foundation for understanding the properties of a large family of related molecules with interesting potential in supramolecular design. [ABSTRACT FROM AUTHOR]

Reactions of [H4L][PF6]4with 4 equiv. of Mn(OAc)2·4H2O in the presence of air gave rise to a mononuclear Mn(iii)–superoxo complex [Mn(iii)L(O2)(H2O)](PF6)2, which contains a bowl-shaped cationic structure with a D4dsymmetry. It has an unprecedented linear end-on Mn(iii)–O2unit and exhibited good efficiency and selectivity in the catalytic oxidation of alkenes with O2plus isobutyraldehyde under mild conditions. [ABSTRACT FROM AUTHOR]

The first zwitterionic alkaline earth metal silanides featuring two naked silyl anions were synthesized and a combined structural and computational study on these zwitterions revealed a correlation between the energy of the HOMO and the degree of negative charge of the naked silyl anions. [ABSTRACT FROM AUTHOR]

A novel zwitterionic stationary phase with high hydrophilicity was facilely synthesized based on the “thiol-ene” click reaction between cysteine and vinyl silica, which exhibited great potential in the separation of oligosaccharides, peptides and basic compounds, as well as in the enrichment of glycopeptides. [ABSTRACT FROM AUTHOR]