This work was supported by the National Natural Science Foundation of China (21471037), Guangdong Natural Science Funds for Distinguished Young Scholars (15ZK0307), Science and Technology Planning Project of Guangdong Province (2017A050506051), and the Research Grants Council of HKSAR [GRF 11303414].

Caution: Please consult all relevant material safety data sheets before use. Methyl disulfide and sodium thiomethoxide are strongly malodorous and should be handled in a fume hood. Sodium metal is highly reactive and requires special safety precautions against potential fire and explosion hazards. In addition to the use of a fume hood, personal protective equipment (safety glasses, gloves, lab coat, full length pants, and closed-toe shoes) should be properly employed. Portions of the following procedures involve standard, air-free handling techniques.
1. Preparation of Sodium Thiomethoxide (CH3SNa)
<ol>
	<li>Connect a 200-mL Schlenk flask to a vacuum gas manifold. Evacuate the flask and then backfill it with N2 three times, such that the flask is filled with a slightly positive N2 pressure. 
	NOTE: A similar method of preparing CH3SNa was mentioned briefly in the literature, but no detailed procedures were provided27,28.</li>
	<li>Take out a block of metallic sodium from the kerosene oil reservoir. Use a paper towel to wipe off the residual oil on the surface, and use a knife to scrape off the oxide layer on the surface. Quickly cut 6.7 g of the metallic sodium (0.29 mol) into small pieces (e.g., about soybean size) and immediately transfer the small pieces to the 200-mL Schlenk flask under a counter flow of N2. Seal the flask with a septum immediately. 
	NOTE: To reduce the exposure to air, one can cut out the sodium with some variation from the amount of 6.7 g, and adjust the amounts of THF and dimethyl disulfide according to the actual amount of sodium used.</li>
	<li>Transfer 80 mL of an anhydrous, airless&#160;THF into the flask via cannula under N2 protection from the Schlenk line. Withdraw 14.0 mL of dimethyl disulfide (0.158 moles; pre-purged with N2) into a syringe and inject it into the flask dropwise under N2 protection. 
	Caution: Dimethyl disulfide is malodorous and should be handled in a fume hood.</li>
	<li>Replace the septum with a ground glass stopper. Stir the reaction mixture at room temperature for 24 h and then at 60 &#176;C for 3 h. 
	NOTE: The reaction mixture became viscous while stirring at room temperature; when heated up to 60 &#176;C, the mixture can be stirred more easily and thus speed up the reaction towards completion.</li>
	<li>With the temperature maintained at about 60 &#176;C, use a stream of N2 (0.2 L/min) to blow off the majority of the THF solvent and the excess dimethyl disulfide, until a dry solid appears. Use a cold trap (e.g., acetone/dry ice) to collect the THF and dimethyl disulfide in the outflow.</li>
	<li>Evacuate the remaining solid mixture with an oil pump for about 2 h to remove the residual THF and dimethyl disulfide and then backfill it with N2 to obtain a light-yellow solid (19.8 g, 97%). Store the solid product CH3SNa in a nitrogen atmosphere in the dark. 
	NOTE: To protect the vacuum oil pump, a cold trap should be used during the pumping.</li>
</ol>
2. Preparation of 2,3,6,7,10,11-hexakis(pentanoylthio)triphenylene (HVaTT) as a protected thiol linker
<ol>
	<li>Load 0.664 g of CH3SNa (9.0 mmol) into a 50-mL Schlenk flask under a counter flow of N2 (i.e., connected as above to a vacuum gas manifold under N2 protection). 
	NOTE: CH3SNa is sensitive to air and easily absorbs water. To minimize exposure to air, one can quickly weigh out a specific amount and add it to the flask, and then adjust the quantity of the other reactant, 2,3,6,7,10,11-hexabromotriphenylene (HBT), accordingly. 
	Caution: Solid CH3SNa has a strong smell and should be handled in a fume hood.</li>
	<li>Add 0.216 g of HBT (0.30 mmol) to the flask under a counter flow of N2, and seal the flask with a septum.</li>
	<li>Transfer 10 mL of anhydrous and airless 1,3-dimethyl-2-imidazolidinone (DMEU) into the flask via cannula under N2 protection from the Schlenk line.</li>
	<li>Replace the septum with a regular glass stopper, and stir the reaction mixture and use a salt bath to heat it to 240 &#176;C for 48 h under N2.</li>
	<li>TLC monitoring of the progress of the reaction: Under N2, use a glass dropper to withdraw a small aliquot of the reaction mixture (about 0.1 mL) and immediately inject it into a neat liquid sample of valeroyl chloride (about 0.1 mL) in a plastic microcentrifuge vial, and then shake for 1 min; the mixture should immediately turn turbid with a grey-white color. Add 0.4 mL of deionized water and 0.1 mL of ethyl acetate, close the cap, and shake it for a few seconds. 
	NOTE: If the reaction has completed already, there will not be anything that appears between the layers of water and ethyl acetate. If not, a white insoluble substance will appear between the two layers.</li>
	<li>Pipet out the upper portion and use it for spotting the TLC plates. Use 1:4 ethyl acetate/petroleum ether to develop the TLC plate. For a complete reaction, the target molecule shows up as a regular spot around Rf = 0.4 under a UV lamp.</li>
	<li>Turn off the heating and take the reaction flask out of the salt bath to cool it to room temperature, and then use an ice bath to cool the flask down to 0 &#176;C.</li>
	<li>Inject 1.5 mL of valeroyl chloride (12.6 mmol) into the flask dropwise (over a period of about 2 min) with a syringe under N2. Keep stirring at 0 &#176;C for 2 h. Note: adding valeroyl chloride slowly and at low temperature helps to reduce the generation of by-products.</li>
	<li>Pour the mixture into 50 mL of ice water and extract using ethyl acetate (3 30 mL). Then wash the combined organic layer with water (6 60 mL), dry over anhydrous MgSO4, and remove the volatiles by a rotary evaporator.</li>
	<li>Isolate the oily crude product by column chromatography using 1:10 ethyl acetate/petroleum ether as the eluent, which affords a light-yellow oily product after rotary evaporation of the solvents. Use 1:4 ethyl acetate/petroleum ether to develop the TLC plate, Rf = 0.4. Further purify the oily product using the trituration step below.</li>
	<li>Add 5 mL of methanolto the oily product, and sonicate for 2 min. Collect the resultant off-white solid using suction filtration (yield: 59%).</li>
</ol>
3. Preparation of Single Crystals of the HTT-Pb Framework Material
<ol>
	<li>Mix 11.4 mg of PbOAc&#183;3H2O (0.030 mmol) in 1.0 mL of ethylene diamine in a vial to make a clear solution.</li>
	<li>Load 9.1 mg of HVaTT (0.010 mmol), 2.0 mL of pre-degassed methanol solution of NaOH (70 mmol/L), and 1.0 mL of ethylene diamine into an empty 10-mL vial and sonicate for 5 min.</li>
	<li>Add the PbOAc solution to the sonicated HVaTT mixture. Then bubble the reaction mixture with N2 for 1 min, and put on the screw cap to seal the vial.</li>
	<li>Heat the vial at 90 &#176;C in an oven for 48 h, followed by natural cooling to room temperature, during which yellow-orange, octahedral single crystals suitable for single-crystal X-ray diffraction studies were formed (yield: 45%).</li>
	<li>Suction filtration off the crystals and quickly wash with MeOH. Transfer the crystals with a glass dropper into a vial containing airless MeOH (5 mL) for storage at room temperature.</li>
</ol>
4. Interaction of Paraquat Diiodide with HTT-Pb Crystals
<ol>
	<li>Use a glass Pasteur pipet to withdraw a few grains of the HTT-Pb single crystal from the MeOH stock and drop it onto a Petri dish (diameter 35 mm and depth 10 mm). Soak up the methanol liquid by tissue or filter paper (or let the MeOH dry up naturally), and then drop onto the crystals a few drops of an aqueous solution of paraquat diiodide (0.1%, w/w).</li>
	<li>Observe the color change of the crystals by eye or under a microscope.</li>
</ol>

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The authors have nothing to disclose.

The reaction between the bromo group and the thiomethoxide anion apparently first produced the methyl thioether, which was then demethylated by the excess thiomethoxide to provide the thiolate anion product. To ensure complete conversion to the desired thiolate anion (especially for a polybromide substrate like HBT), the vigorous conditions of prolonged heating (e.g., 240 &#176;C over 48 h) with a large excess of sodium thiomethoxide (e.g., over three times the moles of the bromo groups) are essential. ...

There is currently great interest in employing strong, polarizable metal-sulfur (e.g., metal-thiolate) links for constructing open framework materials with enhanced electrocatalytic and conductive properties1,2,3,4,5,6,7,8,9,10. In addition to promoting electronic interaction and transport in the extended state, the soft and covalent metal-sulfur links also impart better stability for applications in aqueous environments. Among the sulfur-equipped building blocks, symmetrical, multidentate polycyclic aromatic building blocks like 2,3,6,7,10,11-triphenylene hexathiol (HTT)9,11,12,13,14 not only supply highly polarizable &#960;-electrons, but also offer distinct advantages with respect to framework design and synthesis. First, the rigid and symmetrical triphenylene core, in conjunction with the chelating dithiolene groups of HTT, serves to lock in metal ions in regular bonding motifs, simplifying the structural prediction of the prospective network7,15. Together with the rigid and open geometry of the sulfur linker, framework structures with substantial porosity features can often be achieved in the solid state.
One major challenge in assembling thiol-equipped metal orangic framework (MOF) materials is rooted in the synthesis of the organic linker molecules. In a classical protocol, the thiol group had to be derived from the phenol group using the Newman-Kwart rearrangement of the O-aryl thiocarbamate precursor16,17,18. This approach, however, involves elaborate preparative steps for the phenol precursor molecule as well as potential complications of a high-temperature solid phase transformation. Another way of making thiols utilizes reductive dealkylation of thioethers under the harsh conditions of, for example, sodium metal in liquid ammonia19,20,21,22, and is not compatible with the carboxyl and many other donor functions for network construction.
By comparison, the protocol presented here has multiple advantages: safety, convenience, cost-effectiveness, and compatibility with other functional groups (e.g., carbonitrile and pyridinyl). By vigorously heating the generally inexpensive aromatic halide (e.g., hexabromotriphenylene) and thiomethoxide anion, the thiolate anion was generated (via the methyl thioether intermediate product) and then acylated to give the stable and easy-to-handle thioester product-all in one pot.
We will also describe a procedure for utilizing the thioester molecules as the masked form of the thiol linkers for accessing a single-crystalline semiconducting and porous metal-dithiolene network. Unlike the highly reactive free-standing thiols, which tend to decompose and complicate the crystallization of metal-thiolate open frameworks, the thioester can be readily cleaved (e.g., by NaOH or ethylenediamine) in situ to provide the thiol species, serving to mitigate the reaction between the mercaptan units and the metal centers, and to consequently improve the crystallization.
This protocol of preparing thiol/thioester has not been widely used by other groups for the emerging field of metal-sulfur frameworks, even though nucleophilic dealkylations of alkyl aryl thioethers by thiolate anions have already been well documented by organic chemists23,24,25,26. By showcasing this efficient synthetic method for thioesters and their use for facilitating the crystallization of metal-sulfur networks, we wish to promote further efforts to bridge the intellectual and practical divide between synthetic organic chemistry and solid state chemistry, so as to help the speedy and healthy development of porous frameworks.

<table border="0" cellpadding="0" cellspacing="0" width="850">
	<tbody>
		<tr height="22">
			<td height="22" style="height:22px;width:216px;">Bromine</td>
			<td style="width:348px;">DAMAO CHEMICAL REAGENT FACTORY</td>
			<td style="width:119px;">7726-95-6</td>
			<td style="width:167px;">Highly toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Triphenylene&#160;&#160;</td>
			<td style="width:348px;">HWRK Chem</td>
			<td style="width:119px;">HWG45510</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Iron powder</td>
			<td style="width:348px;">Sigma-Aldrich</td>
			<td style="width:119px;">12310</td>
			<td></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:216px;">Nitrobenzene</td>
			<td style="width:348px;">DAMAO CHEMICAL REAGENT FACTORY</td>
			<td style="width:119px;">2934</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:216px;">Diethyl ether&#160;</td>
			<td style="width:348px;">DAMAO CHEMICAL REAGENT FACTORY</td>
			<td style="width:119px;">48</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:216px;">Dichloromethane</td>
			<td style="width:348px;">DAMAO CHEMICAL REAGENT FACTORY</td>
			<td>3067</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Sodium metal</td>
			<td style="width:348px;">J&#38;K</td>
			<td style="width:119px;">WM-NMS-54-25X-50G</td>
			<td>Air sensitive</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Tetrahydrofuran</td>
			<td style="width:348px;">J&#38;K</td>
			<td style="width:119px;">315353</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Dimethyl disulfide</td>
			<td style="width:348px;">INTERNATIONAL LABORATORY USA</td>
			<td style="width:119px;">726415</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">1,3-Dimethyl-2-imadazolidinone</td>
			<td style="width:348px;">J&#38;K</td>
			<td style="width:119px;">50483</td>
			<td>Dried over 4&#197; sieves</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Valeryl&#160; chloride</td>
			<td style="width:348px;">J&#38;K</td>
			<td style="width:119px;">99590</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Methanol</td>
			<td style="width:348px;">Guangzhou Chemical Reagent Factory</td>
			<td>2334</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sodium hydroxide</td>
			<td style="width:348px;">Guangzhou Chemical Reagent Factory</td>
			<td style="width:119px;">1588</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ethylene diamine</td>
			<td style="width:348px;">Riedel-de Ha&#235;n</td>
			<td style="width:119px;">15070</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Lead acetate trihydrate</td>
			<td>PEKING CHEMICAL WORKE</td>
			<td style="width:119px;">861218</td>
			<td></td>
		</tr>
	</tbody>
</table>

synthesis of a thiol building block for the crystallization of a semiconducting gyroidal metal-sulfur framework

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and porous metal-dithiolene network in the highly ordered single crystalline state. Unlike the highly reactive free-standing thiols, which tend to decompose and complicate the crystallization of metal-thiolate open frameworks, the thioester reacts in situ to provide the thiol species, serving to mitigate the reaction between the mercaptan units and the metal centers, and to improve crystallization consequently. Specifically, the thioester was synthesized in a one-pot procedure: an aromatic bromide (hexabromotriphenylene) reacted with excess sodium thiomethoxide under vigorous conditions to first form the thioether intermediate product. The thioether was then demethylated by the excess thiomethoxide to provide the thiolate anion that was acylated to form the thioester product. The thioester was conveniently purified by standard column chromatography, and then used directly in the framework synthesis, wherein NaOH and ethylenediamine serve to revert in situ the thioester to the thiol linker for assembling the single-crystalline Pb(II)-dithiolene network. Compared with other methods for thiol synthesis (e.g., by cleaving alkyl thioether using sodium metal and liquid ammonia), the thioester synthesis here uses simple conditions and economical reagents. Moreover, the thioester product is stable and can be conveniently handled and stored. More importantly, in contrast to the generic difficulty in accessing crystalline metal-thiolate open frameworks, we demonstrate that using the thioester for in situ formation of the thiol linker greatly improves the crystallinity of the solid-state product. We intend to encourage broader research efforts on the technologically important metal-sulfur frameworks by disclosing the synthetic protocol for the thioester as well as the crystalline framework solid.

The IR spectrum of the HVaTT molecule (collected by the KBr pellet method) features its strongest absorption at 1,700 cm-1, in accordance with the carbonyl stretching of the thioester functional group. The 1H-NMR spectrum of HVaTT (400 MHz, CDCl3) reveals a singlet at &#948; 8.47 from the aromatic hydrogens, together with 4 multiplets from the aliphatic protons: &#948; 8.47 (s, 6H, CHAr), 2.75 -2.72 (t, J = 7.4, 12H, CH2), 1.81-1.77 (m,...

Watch this Scientific Journal Video about Synthesis of a Thiol Building Block for the Crystallization of a Semiconducting Gyroidal Metal-sulfur Framework at JoVE.com

Synthesis of a Thiol Building Block for the Crystallization of a Semiconducting Gyroidal Metal-sulfur Framework

Here, we present a one-pot, transition-metal-free synthesis of thiols and thioesters from aromatic halides and sodium thiomethoxide, followed by the preparation of single crystals of a metal-dithiolene network using thiol species generated in situ from the more stable and tractable thioester.

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and ...

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8.9K Views.  Guangdong University of Technology. Here, we present a one-pot, transition-metal-free synthesis of thiols and thioesters from aromatic halides and sodium thiomethoxide, followed by the preparation of single crystals of a metal-dithiolene network using thiol species generated in situ from the more stable and tractable thioester. 

Video: Synthesis of a Thiol Building Block for the Crystallization of a Semiconducting Gyroidal Metal-sulfur Framework

Preparation and Use of Samarium Diiodide (SmI2) in Organic Synthesis: The Mechanistic Role of HMPA and Ni(II) Salts in the Samarium Barbier Reaction

Although initially considered an esoteric reagent, SmI2 has become a common tool for synthetic organic chemists. SmI2 is generated through the addition of molecular iodine to samarium metal in THF.1,2-3 It is a mild and selective single electron reductant and its versatility is a result of its ability to initiate a wide range of reductions including C-C bond-forming and cascade or sequential reactions. SmI2 can reduce a variety of functional groups including sulfoxides and sulfones, phosphine oxides, epoxides, alkyl and aryl halides, carbonyls, and conjugated double bonds.2-12 One of the fascinating features of SmI-2-mediated reactions is the ability to manipulate the outcome of reactions through the selective use of cosolvents or additives. In most instances, additives are essential in controlling the rate of reduction and the chemo- or stereoselectivity of reactions.13-14 Additives commonly utilized to fine tune the reactivity of SmI2 can be classified into three major groups: (1) Lewis bases (HMPA, other electron-donor ligands, chelating ethers, etc.), (2) proton sources (alcohols, water etc.), and (3) inorganic additives (Ni(acac)2, FeCl3, etc).3
Understanding the mechanism of SmI2 reactions and the role of the additives enables utilization of the full potential of the reagent in organic synthesis. The Sm-Barbier reaction is chosen to illustrate the synthetic importance and mechanistic role of two common additives: HMPA and Ni(II) in this reaction. The Sm-Barbier reaction is similar to the traditional Grignard reaction with the only difference being that the alkyl halide, carbonyl, and Sm reductant are mixed simultaneously in one pot.1,15 Examples of Sm-mediated Barbier reactions with a range of coupling partners have been reported,1,3,7,10,12 and have been utilized in key steps of the synthesis of large natural products.16,17 Previous studies on the effect of additives on SmI2 reactions have shown that HMPA enhances the reduction potential of SmI2 by coordinating to the samarium metal center, producing a more powerful,13-14,18 sterically encumbered reductant19-21 and in some cases playing an integral role in post electron-transfer steps facilitating subsequent bond-forming events.22 In the Sm-Barbier reaction, HMPA has been shown to additionally activate the alkyl halide by forming a complex in a pre-equilibrium step.23
Ni(II) salts are a catalytic additive used frequently in Sm-mediated transformations.24-27 Though critical for success, the mechanistic role of Ni(II) was not known in these reactions. Recently it has been shown that SmI2 reduces Ni(II) to Ni(0), and the reaction is then carried out through organometallic Ni(0) chemistry.28
These mechanistic studies highlight that although the same Barbier product is obtained, the use of different additives in the SmI2 reaction drastically alters the mechanistic pathway of the reaction. The protocol for running these SmI2-initiated reactions is described.

Preparation and Use of Samarium Diiodide SmI2 in Organic Synthesis: The Mechanistic Role of HMPA and NiII Salts in the Samarium Barbier Reaction

A straightforward procedure for the preparation of samarium diiodide (SmI2) in THF is described. The role of two main additives namely hexamethylphosphoramide (HMPA) and Ni(acac)2 in Sm mediated reactions is demonstrated in the Sm-Barbier reaction.

Although initially considered an esoteric reagent, SmI2 has become a common tool for synthetic organic chemists. SmI2 is generated through the addition of ...

Synthesis and Purification of Iodoaziridines Involving Quantitative Selection of the Optimal Stationary Phase for Chromatography

The highly diastereoselective preparation of cis-N-Ts-iodoaziridines through reaction of diiodomethyllithium with N-Ts aldimines is described. Diiodomethyllithium is prepared by the deprotonation of diiodomethane with LiHMDS, in a THF/diethyl ether mixture, at -78 &#176;C in the dark. These conditions are essential for the stability of the LiCHI2 reagent generated. The subsequent dropwise addition of N-Ts aldimines to the preformed diiodomethyllithium solution affords an amino-diiodide intermediate, which is not isolated. Rapid warming of the reaction mixture to 0 &#176;C promotes cyclization to afford iodoaziridines with exclusive cis-diastereoselectivity. The addition and cyclization stages of the reaction are mediated in one reaction flask by careful temperature control.
Due to the sensitivity of the iodoaziridines to purification, assessment of suitable methods of purification is required. A protocol to assess the stability of sensitive compounds to stationary phases for column chromatography is described. This method is suitable to apply to new iodoaziridines, or other potentially sensitive novel compounds. Consequently this method may find application in range of synthetic projects. The procedure involves firstly the assessment of the reaction yield, prior to purification, by 1H NMR spectroscopy with comparison to an internal standard. Portions of impure product mixture are then exposed to slurries of various stationary phases appropriate for chromatography, in a solvent system suitable as the eluent in flash chromatography. After stirring for 30 min to mimic chromatography, followed by filtering, the samples are analyzed by 1H NMR spectroscopy. Calculated yields for each stationary phase are then compared to that initially obtained from the crude reaction mixture. The results obtained provide a quantitative assessment of the stability of the compound to the different stationary phases; hence the optimal can be selected. The choice of basic alumina, modified to activity IV, as a suitable stationary phase has allowed isolation of certain iodoaziridines in excellent yield and purity.

A protocol for the diastereoselective one-pot preparation of cis-N-Ts-iodoaziridines is described. The generation of diiodomethyllithium, addition to N-Ts aldimines and cyclization of the amino gem-diiodide intermediate to iodoaziridines is demonstrated. Also included is a protocol to rapidly and quantitatively assess the most appropriate stationary phase for purification by chromatography.

The highly diastereoselective preparation of cis-N-Ts-iodoaziridines through reaction of diiodomethyllithium with N-Ts aldimines is described. ...

Synthesis and Exfoliation of Discotic Zirconium Phosphates to Obtain Colloidal Liquid Crystals

Due to their abundance in natural clay and potential applications in advanced materials, discotic nanoparticles are of interest to scientists and engineers. Growth of such anisotropic nanocrystals through a simple chemical method is a challenging task. In this study, we fabricate discotic nanodisks of zirconium phosphate [Zr(HPO4)2&#183;H2O] as a model material using hydrothermal, reflux and microwave-assisted methods. Growth of crystals is controlled by duration time, temperature, and concentration of reacting species. The novelty of the adopted methods is that discotic crystals of size ranging from hundred nanometers to few micrometers can be obtained while keeping the polydispersity well within control. The layered discotic crystals are converted to monolayers by exfoliation with tetra-(n)-butyl ammonium hydroxide [(C4H9)4NOH, TBAOH]. Exfoliated disks show isotropic and nematic liquid crystal phases. Size and polydispersity of disk suspensions is highly important in deciding their phase behavior.

A two dimensional model material of discotic zirconium phosphate was developed. The inorganic crystal with lamellar structure was synthesized by hydrothermal, reflux, and microwave-assisted methods. On exfoliation with organic molecules, layered crystals can be converted to monolayers, and nematic liquid crystal phase was formed at sufficient concentration of monolayers.

Due to their abundance in natural clay and potential applications in advanced materials, discotic nanoparticles are of interest to scientists and ...

Synthesis of Programmable Main-chain Liquid-crystalline Elastomers Using a Two-stage Thiol-acrylate Reaction

This study presents a novel two-stage thiol-acrylate Michael addition-photopolymerization (TAMAP) reaction to prepare main-chain liquid-crystalline elastomers (LCEs) with facile control over network structure and programming of an aligned monodomain. Tailored LCE networks were synthesized using routine mixing of commercially available starting materials and pouring monomer solutions into molds to cure. An initial polydomain LCE network is formed via a self-limiting thiol-acrylate Michael-addition reaction. Strain-to-failure and glass transition behavior were investigated as a function of crosslinking monomer, pentaerythritol tetrakis(3-mercaptopropionate) (PETMP). An example non-stoichiometric system of 15 mol% PETMP thiol groups and an excess of 15 mol% acrylate groups was used to demonstrate the robust nature of the material. The LCE formed an aligned and transparent monodomain when stretched, with a maximum failure strain over 600%. Stretched LCE samples were able to demonstrate both stress-driven thermal actuation when held under a constant bias stress or the shape-memory effect when stretched and unloaded. A permanently programmed monodomain was achieved via a second-stage photopolymerization reaction of the excess acrylate groups when the sample was in the stretched state. LCE samples were photo-cured and programmed at 100%, 200%, 300%, and 400% strain, with all samples demonstrating over 90% shape fixity when unloaded. The magnitude of total stress-free actuation increased from 35% to 115% with increased programming strain. Overall, the two-stage TAMAP methodology is presented as a powerful tool to prepare main-chain LCE systems and explore structure-property-performance relationships in these fascinating stimuli-sensitive materials.

A novel methodology is presented to synthesize and program main-chain liquid-crystalline elastomers using commercially available starting monomers. A wide range of thermomechanical properties was tailored by adjusting the amount of crosslinker, while the actuation performance was dependent on the amount of applied strain during programming.

This study presents a novel two-stage thiol-acrylate Michael addition-photopolymerization (TAMAP) reaction to prepare main-chain liquid-crystalline ...

Synthesis of Cd-free InP/ZnS Quantum Dots Suitable for Biomedical Applications

Fluorescent nanocrystals, specifically quantum dots, have been a useful tool for many biomedical applications. For successful use in biological systems, quantum dots should be highly fluorescent and small/monodisperse in size. While commonly used cadmium-based quantum dots possess these qualities, they are potentially toxic due to the possible release of Cd2+ ions through nanoparticle degradation. Indium-based quantum dots, specifically InP/ZnS, have recently been explored as a viable alternative to cadmium-based quantum dots due to their relatively similar fluorescence characteristics and size. The synthesis presented here uses standard hot-injection techniques for effective nanoparticle growth; however, nanoparticle properties such as size, emission wavelength, and emission intensity can drastically change due to small changes in the reaction conditions. Therefore, reaction conditions such temperature, reaction duration, and precursor concentration should be maintained precisely to yield reproducible products. Because quantum dots are not inherently soluble in aqueous solutions, they must also undergo surface modification to impart solubility in water. In this protocol, an amphiphilic polymer is used to interact with both hydrophobic ligands on the quantum dot surface and bulk solvent water molecules. Here, a detailed protocol is provided for the synthesis of highly fluorescent InP/ZnS quantum dots that are suitable for use in biomedical applications.

In this protocol, the synthesis of Cd-free InP/ZnS quantum dots (QDs) is detailed. InP-based QDs are gaining popularity due to the toxicity of Cd2+ ions that may be released through nanoparticle degradation. After synthesis, QDs are solubilized in water using an amphiphilic polymer for use in biomedical applications.

Fluorescent nanocrystals, specifically quantum dots, have been a useful tool for many biomedical applications. For successful use in biological systems, ...

HKUST-1 as a Heterogeneous Catalyst for the Synthesis of Vanillin

Vanillin (4-hydoxy-3-methoxybenzaldehyde) is the main component of the extract of vanilla bean. The natural vanilla scent is a mixture of approximately 200 different odorant compounds in addition to vanillin. The natural extraction of vanillin (from the orchid Vanilla planifolia, Vanilla tahitiensis and Vanilla pompon) represents only 1% of the worldwide production and since this process is expensive and very long, the rest of the production of vanillin is synthesized. Many biotechnological approaches can be used for the synthesis of vanillin from lignin, phenolic stilbenes, isoeugenol, eugenol, guaicol, etc., with the disadvantage of harming the environment since these processes use strong oxidizing agents and toxic solvents. Thus, eco-friendly alternatives on the production of vanillin are very desirable and thus, under current investigation. Porous coordination polymers (PCPs) are a new class of highly crystalline materials that recently have been used for catalysis. HKUST-1 (Cu3(BTC)2(H2O)3, BTC = 1,3,5-benzene-tricarboxylate) is a very well known PCP which has been extensively studied as a heterogeneous catalyst. Here, we report a synthetic strategy for the production of vanillin by the oxidation of trans-ferulic acid using HKUST-1 as a catalyst.

The conversion of trans-ferulic acid to vanillin was achieved by heterogeneous catalysis. HKUST-1 was employed in this synthesis and the essential step in the catalytic process was the generation of unsaturated metal sites. Thus, when the catalyst was activated under vacuum, full vanillin conversion (yield of 95%) was obtained.

Vanillin (4-hydoxy-3-methoxybenzaldehyde) is the main component of the extract of vanilla bean. The natural vanilla scent is a mixture of approximately ...

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the development of antibody drug conjugates (ADCs) and nanomedicine, fluorescent microscopy and systems chemistry. For many of these applications, specificity of the bioconjugation method used is of prime concern. The Michael addition of maleimides with cysteine(s) on the target proteins is highly selective and proceeds rapidly under mild conditions, making it one of the most popular methods for protein bioconjugation.
We demonstrate here the modification of the only surface-accessible cysteine residue on yeast cytochrome c with a ruthenium(II) bisterpyridine maleimide. The protein bioconjugation is verified by gel electrophoresis and purified by aqueous-based fast protein liquid chromatography in 27% yield of isolated protein material. Structural characterization with MALDI-TOF MS and UV-Vis is then used to verify that the bioconjugation is successful. The protocol shown here is easily applicable to other cysteine - maleimide coupling of proteins to other proteins, dyes, drugs or polymers.

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

This protocol details the important steps required for the bioconjugation of a cysteine containing protein to a maleimide, including reagent purification, reaction conditions, bioconjugate purification and bioconjugate characterization.

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the ...

Sulfate Separation by Selective Crystallization with a Bis-iminoguanidinium Ligand

A simple and effective method for selective sulfate separation from aqueous solutions by crystallization with a bis-guanidinium ligand, 1,4-benzene-bis(iminoguanidinium) (BBIG), is demonstrated. The ligand is synthesized as the chloride salt (BBIG-Cl) by in situ imine condensation of terephthalaldehyde with aminoguanidinium chloride in water, followed by crystallization as the sulfate salt (BBIG-SO4). Alternatively, BBIG-Cl is synthesized ex situ in larger scale from ethanol. The sulfate separation ability of the BBIG ligand is demonstrated by selective and quantitative crystallization of sulfate from seawater. The ligand can be recycled by neutralization of BBIG-SO4 with aqueous NaOH and crystallization of the neutral bis-iminoguanidine, which can be converted back into BBIG-Cl with aqueous HCl and reused in another separation cycle. Finally, 35S-labeled sulfate and &#946; liquid scintillation counting are employed for monitoring the sulfate concentration in solution. Overall, this protocol will instruct the user in the necessary skills to synthesize a ligand, employ it in the selective crystallization of sulfate from aqueous solutions, and quantify the separation efficiency.

A protocol for in situ aqueous synthesis of a bis(iminoguanidinium) ligand and its utilization in selective separation of sulfate is presented.

A simple and effective method for selective sulfate separation from aqueous solutions by crystallization with a bis-guanidinium ligand, ...

Electrophoretic Crystallization of Ultrathin High-performance Metal-organic Framework Membranes

We report the synthesis of thin, highly intergrown, polycrystalline metal-organic framework (MOF) membranes on a wide range of unmodified porous and non-porous supports (polymer, ceramic, metal, carbon, and graphene). We developed a novel crystallization technique, which is termed the ENACT approach: the electrophoretic nuclei assembly for the crystallization of highly intergrown thin films (ENACT). This approach allows for a high density of heterogeneous nucleation of MOFs on a chosen substrate via the electrophoretic deposition (EPD) directly from the precursor sol. The growth of well-packed MOF nuclei leads to a highly intergrown polycrystalline MOF film. We show that this simple approach can be used for the synthesis of thin, intergrown zeolite imidazole framework (ZIF)-7 and ZIF-8 films. The resulting 500 nm-thick ZIF-8 membranes show a considerably high H2 permeance (8.3 x 10-6 mol m-2 s-1 Pa-1) and ideal gas selectivities (7.3 for H2/CO2, 15.5 for H2/N2, 16.2 for H2/CH4, and 2655 for H2/C3H8). An attractive performance for C3H6/C3H8 separation is also achieved (a C3H6 permeance of 9.9 x 10-8 mol m-2 s-1 Pa-1 and a C3H6/C3H8 ideal selectivity of 31.6 at 25 &#176;C). Overall, the ENACT process, owing to its simplicity, can be extended to synthesize intergrown thin films of a wide range of nanoporous crystalline materials.

A simple, reproducible, and versatile approach for the synthesis of intergrown, polycrystalline metal-organic framework membranes on a wide range of unmodified porous and non-porous supports is presented.

We report the synthesis of thin, highly intergrown, polycrystalline metal-organic framework (MOF) membranes on a wide range of unmodified porous and ...

Solid-phase Synthesis of [4.4] Spirocyclic Oximes

A convenient synthetic route for spirocyclic heterocycles is well sought after due to the molecule&#39;s potential use in biological systems. By means of solid-phase synthesis, regenerating Michael (REM) linker strategies, and 1,3-dipolar cycloaddition, a library of structurally similar heterocycles, both with and without a spirocyclic center, can be constructed. The main advantages of the solid-support synthesis are as follows: first, each reaction step can be driven to completion using a large excess of reagents resulting in high yields; next, the use of commercially available starting materials and reagents keep the costs low; finally, the reaction steps are easy to purify via simple filtration. The REM linker strategy is attractive because of its recyclability and traceless nature. Once a reaction scheme is completed, the linker can be reused multiple times. In a typical solid-phase synthesis, the product contains either a part of or the whole linker, which can prove undesirable. The REM linker is &#34;traceless&#34; and the point of attachment between the product and the polymer is indistinguishable. The high diastereoselectivity of the intramolecular 1,3-dipolar cycloaddition is well documented. Limited by the insolubility of the solid support, the reaction progression can only be monitored by a change in the functional groups (if any) via infrared (IR) spectroscopy. Thus, the structural identification of intermediates cannot be characterized by conventional nuclear magnetic resonance (NMR) spectroscopy. Other limitations to this method stem from the compatibilities of the polymer/linker to the desired chemical reaction scheme. Herein we report a protocol that allows for the convenient production of spirocyclic heterocycles that, with simple modifications, can be automated with high-throughput techniques.

Here we present a protocol to demonstrate an efficient method for the synthesis of spirocyclic heterocycles. The five-step process utilizes solid-phase synthesis and regenerating Michael linker strategies. Generally difficult to synthesize, we present a customizable method for the synthesis of spirocyclic molecules otherwise inaccessible to other modern approaches.

A convenient synthetic route for spirocyclic heterocycles is well sought after due to the molecule&#39;s potential use in biological systems. By means of ...