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Polyampholyte hydrogels are attractive materials for tissue engineering scaffolds as they offer a wide variety of features including nonfouling, selective protein delivery, and tunable physical characteristics. However, to improve the potential performance of these materials for in vivo applications, there is a need for a higher diversity of zwitterionic cross-linker species to replace commonly used ethylene glycol (EG) based chemistries. Towards this end, the synthesis of a dipeptide based zwitterionic cross-linker, N-Ser-Ser-C dimethacrylate (S-S) from N-Boc-l-serine is presented. The strategy utilized a convergent coupling of methacrylated serine partners followed by careful global deprotection to yield the zwitterionic cross-linker with good overall yields. This novel cross-linker was incorporated into a polyampholyte hydrogel and its physical properties and biocompatibility were compared against a polyampholyte hydrogel synthesized with an EG-based cross-linker. The S-S cross-linked hydrogel demonstrated excellent nonfouling performance, while promoting enhanced cellular adhesion to fibrinogen delivered from the hydrogel. Therefore, the results suggest that the S-S cross-linker will demonstrate superior future performance for in vivo applications.

Passive treatment systems provide lower cost alternatives for remediation of mine drainage; however, acidic drainage increases treatment difficulty because of higher metal concentrations and proton competition for reactive substrates. A silica fiber functionalized with (3-aminopropyl) triethoxysilane (Si + APTES) and a naturally-occurring, microporous silicate mineral (clinoptilolite of the zeolite family) were evaluated in the laboratory as potential reactive substrates for passive treatment of mild (≥ pH of 3) acid rock drainage. Column permeability experiments with spun, 10-µm median diameter, silica fiber and loosely packed, 3.6-mm median diameter clinoptilolite indicate greater permeability and stability of clinoptilolite under flowing conditions. Batch sorption experiments with silica fiber (Si), Si + APTES, and clinoptilolite in a synthetic Fe(II)–SO4, pH 3.0 solution indicate an Fe specific sorption efficacy of Si + APTES > clinoptilolite > Si at equivalent surface areas. Specific sorption normalized to packing densities indicate greater sorption per volume for clinoptilolite. Sorption results for Si + APTES and clinoptilolite did not produce isotherms described by the Langmuir or Freundlich models, likely because of surface heterogeneity and precipitation reactions. Column sorption experiments under flowing conditions indicate an Fe removal efficacy of clinoptilolite > Si + APTES for permeable packing densities. Si + APTES demonstrated high specific sorption of Fe in batch sorption experiments and has potential use in low-flow, passive treatment of mildly acidic solutions. The balance of minimal surface preparation, greater permeability, structural stability, large surface area, micropore structure, and ion-exchange properties make clinoptilolite a better reactive substrate for passive treatment of mildly acidic solutions in high- or low-flow conditions.

The straightforward synthesis of redox-active arylazothioformamide (ATF) ligands allows for electronic diversity as to measure the weak-binding interactions of transition metal salts in supramolecu...

Carbohydrates are an essential group of molecules to the organic chemistry classroom providing molecular relevance to a common ingredient in chemical biology. While the meticulous elucidation of the carbohydrate structures by Fischer and others is an engaging topic in the lecture, there are few laboratory experiments that can emulate carbohydrate complexity. Advanced and multidimensional NMR (2D NMR) techniques such as correlation spectroscopies (COrrelation SpectroscopY (COSY), 13C Distortionless Enhancement by Polarization Transfer (DEPT), and HETeronuclear CORrelation (HETCOR) or Heteronuclear Single Quantum Coherence (HSQC)) have become more routine as they require less time on today’s instruments and are taught more often in lecture. A laboratory experiment is described for second-year introductory undergraduate organic chemistry students that involves the transformation of nutraceutical N-acetyl-d-glucosamine to α-chloroglucosamine tetraacetate. After synthesis and simple workup, students collect four different NMR spectra from which they identify each 1H signal in the product. Students learn to identify each signal’s multiplicity and how multiple NMR experiments are used to characterize a product. Student confidence in NMR characterization was assessed on a small subset through postlab questions and pre- and postsurvey data.

Additions to the popular evaporation rate determination laboratory of alcohol-based hand-rub sanitizers are described here. Significantly, inquiry-driven protocols for formulating hand-rub sanitizers, falling-ball viscometry, and sanitizer efficacy are included. Incorporation of familiar substances (“molecular relevance”) enables students to assimilate knowledge and connect to and recognize interrelated disciplines. To stimulate engagement and project ownership, students were given the opportunity to alter sanitizer formulations by varying the amount and molecular weight of the gelling agent. Viscosities were determined using a falling-ball viscometer to integrate physics and fluid dynamics concepts into these experiments. Lastly, to stress microbiological applications and determine the efficacy of their hand sanitizers, students tested the formulated hand sanitizers for qualitative efficacy using agar plating of skin secretions and comparing colonies formed from sanitized versus nonsanitized hands. Chemi...

Redox-active ligands lead to ambiguity in often clearly defined oxidation states of both the metal centre and the ligand. The arylazothioformamide (ATF) ligand class represents a redox-active ligand with three possible redox states (neutral, singly reduced, and doubly reduced). ATF-metal interactions result in strong colorimetric transitions allowing for the use of ATFs in metal detection and/or separations. While previous reports have discussed dissolution of zerovalent metals, the resulting oxidation states of coordination complexes have proved difficult to interpret through X-ray crystallographic analysis alone. This report describes the X-ray crystallographic analysis combined with computational modelling of the ATF ligand and metal complexes to deconvolute the metal and ligand oxidation state of metal-ATF complexes. Metal(ATF)2 complexes that originated from zerovalent metals were found to exist as dicationic metal centers containing two singly reduced ATF ligands. When employing Cu(I) salts instead of Cu(0) to generate copper-ATF complexes, the resulting complexes remained Cu(I) and the ATF ligand remained "innocent", existing in its neutral state. Although the use of CuX (where X = Br or I) or [Cu(NCMe)4]Y (where Y = BF4 or PF6) generated species of the type: [(ATF)Cu(μ-X)]2 and [Cu(ATF)2]Y, respectively, the ATF ligand remained in its neutral state for each species type.

The heterogeneity and anisotropy of fractured-rock aquifers, such as those in the Columbia River Basalt Province, present challenges for determining groundwater recharge. The entrance of recharge to the fractured-basalt and interbedded-sediment aquifer in the Palouse region of north-central Idaho is not well understood because of successive basalt flows that act as restrictive barriers. It was hypothesized that a primary recharge zone exists along the basin’s eastern margin at a mountain-front interface where eroded sediments form a more conductive zone for recharge. Potential source waters and groundwater were analyzed for δ18O and δ2H to discriminate recharge sources and pathways. Snowpack values ranged from −22 to −12‰ for δ18O and from −160 to −90‰ for δ2H and produced spring-time snowmelt ranging from −16.5 to −12‰ for δ18O and from −120 to −90‰ for δ2H. With the transition of snowmelt to spring-time ephemeral creeks, the isotope values compressed to −16 and −14‰ for δ18O and −110 and −105‰ for δ2H. A greater range of values was present for a perennial creek (−18 to −13.5‰ for δ18O and −125 to −98‰ for δ2H) and groundwater (−17.5 to −13‰ for δ18O and −132 to −105‰ for δ2H), which reflect a mixing of seasonal signals and the varying influence of vapor sources and sublimation/evaporation. Inverse modeling and the evaluation of matrix characteristics indicate conductive pathways associated with paleochannels and deeper pathways along the mountain-front interface. Depleted isotope signals indicate quicker infiltration and recharge pathways that were separate from, or had limited mixing with, more evaporated water that infiltrated after greater time/travel at the surface.

The distorted title square-planar silver(I) complex was obtained in very good yield after gentle mixing of solutions of the N,N-di­ethyl­phenyl­azo­thio­formamide (ATF) ligand with silver hexa­fluorido­phosphate in tetra­hydro­furan. In the crystal, one sulfur atom from an ATF ligand of a neighboring complex coordinates to the silver atom, with a bond distance of 2.9884 (14) Å. This creates a polymeric zigzag chain propagating along the c-axis direction., The structure of the title complex, [Ag(C11H15N3S)2]PF6, has monoclinic (P21/c) symmetry, and the silver atom has a distorted square-planar geometry. The coordination complex crystallized from mixing silver hexa­fluorido­phosphate with a concentrated tetra­hydro­furan solution of N,N-di­ethyl­phenyl­azo­thio­formamide [ATF; systematic name: 3,3-diethyl-1-(phenyl­imino)­thio­urea] under ambient conditions. The resultant coordination complex exhibits a 2:1 ligand-to-metal ratio, with the silver(I) atom having a fourfold AgN2S2 coordination sphere, with a single PF6 counter-ion. In the crystal, however, one sulfur atom from an ATF ligand of a neighboring complex coordinates to the silver atom, with a bond distance of 2.9884 (14) Å. This creates a polymeric zigzag chain propagating along the c-axis direction. The chains are linked by C—H⋯F hydrogen bonds, forming slabs parallel to the ac plane.

Redox-active azothioformamides ligands rapidly coordinate to transition metals and are excellent substrates for monitoring host–guest binding interaction mechanisms as they can exhibit unique coordination complexes while producing an increase in extinction coefficient upon addition of metal salt. Herein, an alkyl derivative, N,N-diethyl-t-butylazothioformamide, was synthesized and fully characterized, including X-ray crystallography. Crystalline coordination complexes were prepared with various copper(I) salts (CuBr, CuI and [(CH3CN)4Cu]BF4 producing both 1:1 µ-X dimers from copper(I) halides and a distorted tetrahedral 2:1 species with non-coordinative tetrafluoroborate salt. Bond distances and angles suggest neutrally bound alkyl azothioformamide ligands with copper(I), indicating no redox activity upon binding. UV–Vis titration studies with copper(I) salts and subsequent data evaluation with both 1:1 and 2:1 non-linear regression binding models suggest inconsistent mechanisms with copper(I) salts.

With the growing demand for measurements of organophosphate (OP) pesticide use in agriculture along with the potential threat of OP-based chemical warfare agents, there is a need for new devices or surfaces that can quickly degrade OPs into less toxic substances in a variety of environments. Using surface-initiated atom transfer radical polymerization and post-polymerization synthesis, we prepared a series of quaternary ammonium fluoride-based polymer brushes designed to absorb and degrade OPs. Specifically, a polymer brush was formed using 2-dimethylamino-ethyl methacrylate (DMAEMA) as monomer, which, following post-polymerization quaternization of the tertiary amine with alkylating agents and fluoride ion exchange, afforded the OP-reactive polymer surfaces. Poly(DMAEMA) brushes were grown to thicknesses of ~100 nm on silicon wafers and glass slides and characterized by ellipsometry, atomic force microscopy, and Raman spectroscopy. Quaternization and subsequent ion exchange of the brushes were characterized by Raman spectroscopy and X-ray photoelectron spectroscopy, respectively. The interaction of the brushes with OPs was evaluated using the OP-based pesticide coumaphos, through the presence of the highly fluorescent degradation product chlorferon; analyzed qualitatively via fluorescence microscopy; and confirmed via nuclear magnetic resonance and mass spectrometry. We found that the fluoride form of the brush reliably degraded coumaphos deposited via controlled solution-based applications and aerosol applications (electrohydrodynamic jetting) and from microcontact printing of the dried solid directly onto the brush. No degradation was seen for coumaphos deposited on poly(DMAEMA) or the iodide form of the quaternized brush. Copyright © 2016 John Wiley & Sons, Ltd.

Redox-active ligands lead to ambiguity in often clearly defined oxidation states of both the metal centre and the ligand. The arylazothioformamide (ATF) ligand class represents a redox-active ligand with three possible redox states (neutral, singly reduced, and doubly reduced). ATF-metal interactions result in strong colorimetric transitions allowing for the use of ATFs in metal detection and/or separations. While previous reports have discussed dissolution of zerovalent metals, the resulting oxidation states of coordination complexes have proved difficult to interpret through X-ray crystallographic analysis alone. This report describes the X-ray crystallographic analysis combined with computational modelling of the ATF ligand and metal complexes to deconvolute the metal and ligand oxidation state of metal-ATF complexes. Metal(ATF)2 complexes that originated from zerovalent metals were found to exist as dicationic metal centers containing two singly reduced ATF ligands. When employing Cu(I) salts instead of Cu(0) to generate copper-ATF complexes, the resulting complexes remained Cu(I) and the ATF ligand remained “innocent”, existing in its neutral state. Although the use of CuX (where X = Br or I) or [Cu(NCMe)4]Y (where Y = BF4 or PF6) generated species of the type: [(ATF)Cu(μ-X)]2 and [Cu(ATF)2]Y, respectively, the ATF ligand remained in its neutral state for each species type.

OriginLab’s newest version update to Origin and OriginPro includes ease-of-use features, like Origin Central updates and creation of an App Center, as well as larger changes like the addition of Unicode characters, alteration to how user files are stored and visually searched, and user input formula in cells within worksheets. These features add additional value to an already powerful data analysis and plotting software package.

We present a facile microfluidic method for forming narrow chemical gradients in polymer brushes. Co-flow of an alkylating agent solution and a neat solvent in a microfluidic channel forms a diffusion-driven concentration gradient, and thus a gradient in reaction rate at the interface of the two flows, leading to a quaternization gradient in the underlying poly(2-(dimethylamino)ethyl methacrylate) polymer brush. The spatial distribution of the quaternized polymer brush is characterized by confocal Raman microscopy. The quaternization gradient length in the polymer brush can be varied with the injection flow rate and the distance from the co-flow junction. A chemical gradient in the polymer brush as narrow as 5 μm was created by controlling these parameters. The chemical gradient by laminar co-flow is compared with numerical calculations that include only one adjustable parameter: the reaction rate constant of the polymer brush quaternization. The calculated chemical gradient agrees with the experimental data, which validates the numerical procedures established in this study. Flow of multiple laminar streams of reactive agent solutions enables single-run fabrication of brush gradients with more than one chemical property. As one example, four laminar streams-neat solvent/benzyl bromide solution/propargyl bromide solution/neat solvent-generate multistep gradients of aromatic and alkyne groups. Because the alkyne functional group is a click-reaction available site, the alkyne gradient could allow small gradient formation with a wide variety of chemical properties in a polymer brush.

We report a general diffusion based method to form micrometer-scale lateral chemical gradients in polymer brushes via selective alkylation. A quaternized brush gradient is derived from a concentration gradient of alkylating agent formed by diffusion in permeable media around a microchannel carrying the alkylating agent. Polymer brushes containing both charge and aromatic gradients are formed using the alkylating agents, methyl iodide and benzyl bromide, respectively. The gradients are quantitatively characterized by confocal Raman spectroscopy and qualitatively by fluorescence microscopy. The length and gradient strength can be controlled by varying the diffusion time, concentrations, and solvents of the alkylating agent solutions. This microfluidic brush gradient generation method enables formation of 2-D chemical potential gradients with a diversity of shapes.

Preparation of mixed carbonates proceeded in one step from ketones and aldehydes via treatment with NaBH4 in dimethyl or diethyl carbonate solvent at elevated temperatures. This is an efficient and convenient alternative to the traditional two-step sequence of carbonyl reduction to alcohol and subsequent carbonate formation by treatment with an alkyl chloroformate. 25 examples are presented from 49 to 92% yield, highlighting the versatility of this reaction.

The coupling of pentenylcarbene complexes and 2-alkynylbenzoyl derivatives affords naphthocycloheptanones in a single step involving simultaneous construction of both the seven-membered ring and one of the aromatic rings. Aryl tethered systems undergo intramolecular cyclopropanation.

Materials which induce molecular motion without external input offer unique opportunities for spatial manipulation of molecules. Here, we present the use of polyacrylamide hydrogel films containing built-in chemical gradients (enthalpic gradients) to direct molecular transport. Using a cationic tertiary amine gradient, anionic molecules were directionally transported up to several millimeters. A 40-fold concentration of anionic molecules dosed in aerosol form on a substrate to a small region at the center of a radially symmetric cationic gradient was observed. The separation of mixtures of charged dye molecules was demonstrated using a boronic acid-to-cationic gradient where one molecule was attracted to the boronic acid end of the gradient, and the other to the cationic end of the gradient. Theoretical and computational analysis provides a quantitative description of such anisotropic molecular transport, and reveals that the gradient-imposed drift velocity is in the range of hundreds of nanometers per second, comparable to the transport velocities of biomolecular motors. This general concept of enthalpy gradient-directed molecular transport should enable the autonomous processing of a diversity of chemical species.

The glycosylation of proteins, specifically installation of O-GlcNAc on Ser/Thr residues, is a dynamic control element for transcription repression, protein degradation, and nutrient sensing. To provide homogeneous and stable structures with this motif, the synthesis of a C-linked mimic, C-GlcNAc Ser, has been prepared from the C-Glc Ser by a double inversion strategy using azide to insert the C-2 nitrogen functionality. The C-Glc Ser was available by a ring-closing metathesis and hydroalkoxylation route.

The open-chain Fischer carbenes (II) are suitable substrates for the construction of various title compounds where the seven-membered ring and one of the benzene rings are formed in a single step.

Dehydroacetic acid reacts with acetic anhydride in the presence of perchloric acid to give a salt which upon careful neutralization affords a fused bis-gamma-pyrone. The bis-gamma-pyrone forms stable metal complexes with Li, Mg, Cu(II), Ni(II), Zn, Fe(II), Co(II) and Ba perchlorates whose crystal structures reveal that the ligand possesses significant bispyrylium character while the metal is coordinated at the negatively charged edge of the structure.