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><tbody><tr><td>Bromine</td><td>DAMAO CHEMICAL REAGENT FACTORY</td><td>7726-95-6</td><td>Highly toxic</td></tr><tr><td>Triphenylene&amp;nbsp;&amp;nbsp;</td><td>HWRK Chem</td><td>HWG45510</td><td></td></tr><tr><td>Iron powder</td><td>Sigma-Aldrich</td><td>12310</td><td></td></tr><tr><td>Nitrobenzene</td><td>DAMAO CHEMICAL REAGENT FACTORY</td><td>2934</td><td></td></tr><tr><td>Diethyl ether&amp;nbsp;</td><td>DAMAO CHEMICAL REAGENT FACTORY</td><td>48</td><td></td></tr><tr><td>Dichloromethane</td><td>DAMAO CHEMICAL REAGENT FACTORY</td><td>3067</td><td></td></tr><tr><td>Sodium metal</td><td>J&amp;amp;K</td><td>WM-NMS-54-25X-50G</td><td>Air sensitive</td></tr><tr><td>Tetrahydrofuran</td><td>J&amp;amp;K</td><td>315353</td><td></td></tr><tr><td>Dimethyl disulfide</td><td>INTERNATIONAL LABORATORY USA</td><td>726415</td><td></td></tr><tr><td>1,3-Dimethyl-2-imadazolidinone</td><td>J&amp;amp;K</td><td>50483</td><td>Dried over 4&amp;Aring; sieves</td></tr><tr><td>Valeryl&amp;nbsp; chloride</td><td>J&amp;amp;K</td><td>99590</td><td></td></tr><tr><td>Methanol</td><td>Guangzhou Chemical Reagent Factory</td><td>2334</td><td></td></tr><tr><td>Sodium hydroxide</td><td>Guangzhou Chemical Reagent Factory</td><td>1588</td><td></td></tr><tr><td>Ethylene diamine</td><td>Riedel-de Ha&amp;euml;n</td><td>15070</td><td></td></tr><tr><td>Lead acetate trihydrate</td><td>PEKING CHEMICAL WORKE</td><td>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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9.0K 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

Gyroid Nickel Nanostructures from Diblock Copolymer Supramolecules

Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, have high porosity, high surface-to-volume and strength-to-weight ratio. Unfortunately, common approaches for preparation of metallic nanostructures render materials with highly disordered architecture, which might have an adverse effect on their mechanical properties. Block copolymers have the ability to self-assemble into ordered nanostructures and can be applied as templates for the preparation of well-ordered metal nanofoams. Here we describe the application of a block copolymer-based supramolecular complex - polystyrene-block-poly(4-vinylpyridine)(pentadecylphenol) PS-b-P4VP(PDP) - as a precursor for well-ordered nickel nanofoam. The supramolecular complexes exhibit a phase behavior similar to conventional block copolymers and can self-assemble into the bicontinuous gyroid morphology with two PS networks placed in a P4VP(PDP) matrix. PDP can be dissolved in ethanol leading to the formation of a porous structure that can be backfilled with metal. Using electroless plating technique, nickel can be inserted into the template&#39;s channels. Finally, the remaining polymer can be removed via pyrolysis from the polymer/inorganic nanohybrid resulting in nanoporous nickel foam with inverse gyroid morphology.

This article describes the preparation of well-ordered nickel nanofoams via electroless metal deposition onto nanoporous templates obtained from self-assembled diblock copolymer based supramolecules.

Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, ...

Synthesis of Ligand-free CdS Nanoparticles within a Sulfur Copolymer Matrix

Aliphatic ligands are typically used during the synthesis of nanoparticles to help mediate their growth in addition to operating as high-temperature solvents. These coordinating ligands help solubilize and stabilize the nanoparticles while in solution, and can influence the resulting size and reactivity of the nanoparticles during their formation. Despite the ubiquity of using ligands during synthesis, the presence of aliphatic ligands on the nanoparticle surface can result in a number of problems during the end use of the nanoparticles, necessitating further ligand stripping or ligand exchange procedures. We have developed a way to synthesize cadmium sulfide (CdS) nanoparticles using a unique sulfur copolymer. This sulfur copolymer is primarily composed of elemental sulfur, which is a cheap and abundant material. The sulfur copolymer has the advantages of operating both as a high temperature solvent and as a sulfur source, which can react with a cadmium precursor during nanoparticle synthesis, resulting in the generation of ligand free CdS. During the reaction, only some of the copolymer is consumed to produce CdS, while the rest remains in the polymeric state, thereby producing a nanocomposite material. Once the reaction is finished, the copolymer stabilizes the nanoparticles within a solid polymeric matrix. The copolymer can then be removed before the nanoparticles are used, which produces nanoparticles that do not have organic coordinating ligands. This nascent synthesis technique presents a method to produce metal-sulfide nanoparticles for a wide variety of applications where the presence of organic ligands is not desired.

Herein we present a method to synthesize ligand-free cadmium sulfide (CdS) nanoparticles based on a unique sulfur copolymer. The sulfur copolymer operates as a high temperature solvent and a sulfur source during the nanoparticle synthesis and stabilizes the nanoparticles after the reaction.

Aliphatic ligands are typically used during the synthesis of nanoparticles to help mediate their growth in addition to operating as high-temperature ...

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, ...

The Synthesis of [Sn10(Si(SiMe3)3)4]2- Using a Metastable Sn(I) Halide Solution Synthesized via a Co-condensation Technique

The number of well-characterized metalloid tin clusters, synthesized by applying the disproportionation of a metastable Sn(I) halide in the presence of a sterically demanding ligand, has increased in recent years. The metastable Sn(I) halide is synthesized at&#160;&#34;outer space conditions&#34; via the preparative co-condensation technique. Thereby, the subhalide is synthesized in an oven at high temperatures, around 1,300 &#176;C, and at reduced pressure by the reaction of elemental tin with hydrogen halide gas (e.g., HCl). The subhalide (e.g., SnCl) is trapped within a matrix of an inert solvent, like toluene at -196 &#176;C. Heating the solid matrix to -78 &#176;C gives a metastable solution of the subhalide. The metastable subhalide solution is highly reactive but can be stored at -78 &#176;C for several weeks. On heating the solution to room temperature, a disproportionation reaction occurs, leading to elemental tin and the corresponding dihalide. By applying bulky ligands like Si(SiMe3)3, the intermediate metalloid cluster compounds can be trapped before complete disproportionation to elemental tin. Hence, the reaction of a metastable Sn(I)Cl solution with Li-Si(SiMe3)3 gives [Sn10(Si(SiMe3)3)4]2- 1 as black crystals in high yield. 1 is formed via a complex reaction sequence including salt metathesis, disproportionation, and degradation of larger clusters. Further, 1 can be analyzed by various methods like NMR or single crystal X-ray structure analysis.

The Synthesis of [Sn10SiSiMe334]2- Using a Metastable SnI Halide Solution Synthesized via a Co-condensation Technique

The disproportionation reaction of a metastable Sn(I) chloride solution, obtained via the preparative co-condensation technique, is used for the synthesis of a metalloid tin cluster compound.

The number of well-characterized metalloid tin clusters, synthesized by applying the disproportionation of a metastable Sn(I) halide in the presence of a ...

Preparation of Large-area Vertical 2D Crystal Hetero-structures Through the Sulfurization of Transition Metal Films for Device Fabrication

We have demonstrated that through the sulfurization of transition metal films such as molybdenum (Mo) and tungsten (W), large-area and uniform transition metal dichalcogenides (TMDs) MoS2 and WS2 can be prepared on sapphire substrates. By controlling the metal film thicknesses, good layer number controllability, down to a single layer of TMDs, can be obtained using this growth technique. Based on the results obtained from the Mo film sulfurized under the sulfur deficient condition, there are two mechanisms of (a) planar MoS2 growth and (b) Mo oxide segregation observed during the sulfurization procedure. When the background sulfur is sufficient, planar TMD growth is the dominant growth mechanism, which will result in a uniform MoS2 film after the sulfurization procedure. If the background sulfur is deficient, Mo oxide segregation will be the dominant growth mechanism at the initial stage of the sulfurization procedure. In this case, the sample with Mo oxide clusters covered with few-layer MoS2 will be obtained. After sequential Mo deposition/sulfurization and W deposition/sulfurization procedures, vertical WS2/MoS2 hetero-structures are established using this growth technique. Raman peaks corresponding to WS2 and MoS2, respectively, and the identical layer number of the hetero-structure with the summation of individual 2D materials have confirmed the successful establishment of the vertical 2D crystal hetero-structure. After transferring the WS2/MoS2 film onto a SiO2/Si substrate with pre-patterned source/drain electrodes, a bottom-gate transistor is fabricated. Compared with the transistor with only MoS2 channels, the higher drain currents of the device with the WS2/MoS2 hetero-structure have exhibited that with the introduction of 2D crystal hetero-structures, superior device performance can be obtained. The results have revealed the potential of this growth technique for the practical application of 2D crystals.

Through the sulfurization of pre-deposited transition metals, large-area and vertical 2D crystal hetero-structures can be fabricated. The film transferring and device fabrication procedures are also demonstrated in this report.

We have demonstrated that through the sulfurization of transition metal films such as molybdenum (Mo) and tungsten (W), large-area and uniform transition ...

Engineering

Constructing Thioether/Vinyl Sulfide-tethered Helical Peptides Via Photo-induced Thiol-ene/yne Hydrothiolation

Here, we describe a detailed protocol for the preparation of thioether-tethered peptides using on-resin intramolecular/intermolecular thiol-ene hydrothiolation. In addition, this protocol describes the preparation of vinyl-sulfide-tethered peptides using in-solution intramolecular thiol-yne hydrothiolation between amino acids that possess alkene/alkyne side chains and cysteine residues at i, i+4 positions. Linear peptides were synthesized using a standard Fmoc-based solid-phase peptide synthesis (SPPS). Thiol-ene hydrothiolation is carried out using either an intramolecular thio-ene reaction or an intermolecular thio-ene reaction, depending on the peptide length. In this research, an intramolecular thio-ene reaction is carried out in the case of shorter peptides using on-resin deprotection of the trityl groups of cysteine residues following the complete synthesis of the linear peptide. The resin is then set to UV irradiation using photoinitiator 4-methoxyacetophenone (MAP) and 2-hydroxy-1-[4-(2-hydroxyethoxy)-phenyl]-2-methyl-1-propanone (MMP). The intermolecular thiol-ene reaction is carried out by dissolving Fmoc-Cys-OH in an N,N-dimethylformamide (DMF) solvent. This is then reacted with the peptide using the alkene-bearing residue on resin. After that, the macrolactamization is carried out using benzotriazole-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate (PyBop), 1-hydroxybenzotriazole (HoBt), and 4-Methylmorpholine (NMM) as activation reagents on the resin. Following the macrolactamization, the peptide synthesis is continued using standard SPPS. In the case of the thio-yne hydrothiolation, the linear peptide is cleaved from the resin, dried, and subsequently dissolved in degassed DMF. This is then irradiated using UV light with photoinitiator 2,2-dimethoxy-2-phenylacetophenone (DMPA). Following the reaction, DMF is evaporated and the crude residue is precipitated and purified using high-performance liquid chromatography (HPLC). These methods could function to simplify the generation of thioether-tethered cyclic peptides due to the use of the thio-ene/yne click chemistry that possesses superior functional group tolerance and good yield. The introduction of thioether bonds into peptides takes advantage of the nucleophilic nature of cysteine residues and is redox-inert relative to disulfide bonds.

We present a protocol for the construction of thioether/vinyl sulfide-tethered helical peptides using photo-induced thiol-ene/thiol-yne hydrothiolation.

Here, we describe a detailed protocol for the preparation of thioether-tethered peptides using on-resin intramolecular/intermolecular thiol-ene ...

Synthesis of Terpolymers at Mild Temperatures Using Dynamic Sulfur Bonds in Poly(S-Divinylbenzene)

Elemental sulfur (S8) is a byproduct of the petroleum industry with millions of tons produced annually. Such abundant production and limited applications lead to sulfur as a cost-efficient reagent for polymer synthesis. Inverse vulcanization combines elemental sulfur with a variety of monomers to form functional polysulfides without the need for solvents. Short reaction times and straight forward synthetic methods have led to rapid expansion of inverse vulcanization. However, high reaction temperatures (&#62;160 &#176;C) limit the types of monomers that can be used. Here, the dynamic sulfur bonds in poly(S-divinylbenzene) are used to initiate polymerization at much lower temperatures. The S-S bonds in the prepolymer are less stable than S-S bonds in S8, allowing radical formation at 90 &#176;C rather than 159 &#176;C. A variety of allyl and vinyl ethers have been incorporated to form terpolymers. The resulting materials were characterized by 1H NMR, gel permeation chromatography, and differential scanning calorimetry, as well as examining changes in solubility. This method expands on the solvent-free, thiyl radical chemistry utilized by inverse vulcanization to create polysulfides at mild temperatures. This development broadens the range of monomers that can be incorporated thus expanding the accessible material properties and possible applications.

Synthesis of Terpolymers at Mild Temperatures Using Dynamic Sulfur Bonds in PolyS-Divinylbenzene

The goal of this protocol is to initiate polymerization using dynamic sulfur bonds in poly(S-divinylbenzene) at mild temperatures (90 &#176;C) without using solvents. Terpolymers are characterized by GPC, DSC and 1H NMR, and tested for changes in solubility.

Elemental sulfur (S8) is a byproduct of the petroleum industry with millions of tons produced annually. Such abundant production and limited applications ...

Synthesis of Single-Crystalline Core-Shell Metal-Organic Frameworks

Because of their designability and unprecedented synergistic effects, core-shell metal-organic frameworks (MOFs) have been actively examined recently. However, the synthesis of single-crystalline core-shell MOFs is very challenging, and thus a limited number of examples have been reported. Here, we suggest a method of synthesizing single-crystalline HKUST-1@MOF-5 core-shells, which is HKUST-1 at the center of MOF-5. Through the computational algorithm, this pair of MOFs was predicted to have the matched lattice parameters and chemical connection points at the interface. To construct the core-shell structure, we prepared the octahedral- and cubic-shaped HKUST-1 crystals as a core MOF, in which the (111) and (001) facets were mainly exposed, respectively. Via the sequential reaction, the MOF-5 shell was well-grown on the exposed surface, showing a seamless connect interface, which resulted in the successful synthesis of single-crystalline HKUST-1@MOF-5. Their pure phase formation was proved by optical microscopic images and powder X-ray diffraction (PXRD) patterns. This method presents the potential of and insights into the single-crystalline core-shell synthesis with different kinds of MOFs.

Here, we demonstrate a protocol for the two-step synthesis of single-crystalline core-shells using a non-isostructural metal-organic framework (MOF) pair, HKUST-1 and MOF-5, which have well-matched crystal lattices.

Because of their designability and unprecedented synergistic effects, core-shell metal-organic frameworks (MOFs) have been actively examined recently. ...

Synthesis of Low-Valent MOFs from Multitopic Phosphine Linkers

Experimental Approaches for the Synthesis of Low-Valent Metal-Organic Frameworks from Multitopic Phosphine Linkers

Metal-organic frameworks (MOFs) are the subject of intense research focus due to their potential applications in gas storage and separation, biomedicine, energy, and catalysis. Recently, low-valent MOFs (LVMOFs) have been explored for their potential use as heterogeneous catalysts, and multitopic phosphine linkers have been shown to be a useful building block for the formation of LVMOFs. However, the synthesis of LVMOFs using phosphine linkers requires conditions that are distinct from those in the majority of the MOF synthetic literature, including the exclusion of air and water and the use of unconventional modulators and solvents, making it somewhat more challenging to access these materials. This work serves as a general tutorial for the synthesis of LVMOFs with phosphine linkers, including information on the following: 1) the judicious choice of the metal precursor, modulator, and solvent; 2) the experimental procedures, air-free techniques, and required equipment; 3) the proper storage and handling of the resultant LVMOFs; and 4) useful characterization methods for these materials. The intention of this report is to lower the barrier to this new subfield of MOF research and facilitate advancements toward novel catalytic materials.

Author Spotlight: Experimental Approaches for the Synthesis of Low-Valent Metal-Organic Frameworks from Multitopic Phosphine Linkers  

Here, we describe a protocol for the synthesis of low-valent metal-organic frameworks (LVMOFs) from low-valent metals and multitopic phosphine linkers under air-free conditions. The resulting materials have potential applications as heterogeneous catalyst mimics of low-valent metal-based homogeneous catalysts.

Metal-organic frameworks (MOFs) are the subject of intense research focus due to their potential applications in gas storage and separation, biomedicine, ...

Synthesis of Nine-atom Deltahedral Zintl Ions of Germanium and their Functionalization with Organic Groups

Although the first studies of Zintl ions date between the late 1890's and early 1930's they were not structurally characterized until many years later.1,2 Their redox chemistry is even younger, just about ten years old, but despite this short history these deltahedral clusters ions E9n- (E = Si, Ge, Sn, Pb; n = 2, 3, 4) have already shown interesting and diverse reactivity and have been at the forefront of rapidly developing and exciting new chemistry.3-6 Notable milestones are the oxidative coupling of Ge94- clusters to oligomers and infinite chains,7-19 their metallation,14-16,20-25 capping by transition-metal organometallic fragments,26-34 insertion of a transition-metal atom at the center of the cluster which is sometimes combined with capping and oligomerization,35-47 addition of main-group organometallic fragments as exo-bonded substituents,48-50 and functionalization with various organic residues by reactions with organic halides and alkynes.51-58 
This latter development of attaching organic fragments directly to the clusters has opened up a new field, namely organo-Zintl chemistry, that is potentially fertile for further synthetic explorations, and it is the step-by-step procedure for the synthesis of germanium-divinyl clusters described herein. The initial steps outline the synthesis of an intermetallic precursor of K4Ge9 from which the Ge94- clusters are extracted later in solution. This involves fused-silica glass blowing, arc-welding of niobium containers, and handling of highly air-sensitive materials in a glove box. The air-sensitive K4Ge9 is then dissolved in ethylenediamine in the box and then alkenylated by a reaction with Me3SiC&equiv;CSiMe3. The reaction is followed by electrospray mass spectrometry while the resulting solution is used for obtaining single crystals containing the functionalized clusters [H2C=CH-Ge9-CH=CH2]2-. For this purpose the solution is centrifuged, filtered, and carefully layered with a toluene solution of 18-crown-6. Left undisturbed for a few days, the so-layered solutions produced orange crystalline blocks of [K(18-crown-6)]2[Ge9(HCCH2)2]&bull;en which were characterized by single-crystal X-ray diffraction. 
The process highlights standard reaction techniques, work-up, and analysis towards functionalized deltahedral Zintl clusters. It is hoped that it will help towards further development and understanding of these compounds in the community at large.

We present the high-temperature synthesis of intermetallic precursors K4Ge9, their dissolution in ethylenediamine to form Ge94- deltahedral Zintl ions, and the reaction of the clusters with alkynes to form organo-Zintl ions. The latter are characterized by electrospray mass spectrometry in solutions and by single-crystal X-ray diffraction in the solid state.

Although the first studies of Zintl ions date between the late 1890's and early 1930's they were not structurally characterized until many years later.1,2 ...