Aliphatic Dithiols Research Articles

Photopolymerizable semi-crystalline polymers for thermally reversible, 3D printable cast molds

ObjectivesThis study demonstrates the use of photopolymerization to create semi-crystalline linear polymers suitable for thermally reversible materials in dental cast moldings produced from 3D printing. MethodsAn aromatic diallyl, aliphatic dithiol chain extender, and monofunctional thiol were used in a photoinitiated system. The photopolymerization and crystallization kinetics as a function of chemistry and temperature were investigated using spectroscopy and calorimetry. These insights were used to realize vat photopolymerization-based 3D printing of functional objects that could be remotely melted and thereby removed using induction heating. ResultsThe addition of monothiol was shown to decrease the polymer molecular weight which correspondingly increased the crystallization rate. Photopolymerization kinetics are independent of temperature while crystallization was slowed as the temperature approaches the melting point of the materials. Through inclusion of chromium oxide, semicrystalline materials could be melted through induction heating. These materials were implemented in vat photopolymerization 3D printing to realize high-resolution objects that could be used as releasable dental molds following printing and induction heating. SignificanceThis work demonstrates a proof-of-concept methodology to realize directly printable, thermally reversible semicrystalline materials for potential use as dental molding materials.

Tailor-made poly(vinylidene sulfide)s by Rh(I)–NHC catalyzed regioselective thiol-yne click polymerization

The [Rh(μ-Cl)(IPr)(η2-coe)]2/pyridine system efficiently catalyzes the polyhydrothiolation of a series of dialkynes with dithiols, producing sulfur-rich poly(vinylidene sulfide)s with a typical Mw in the range 20.000–124.000 and vinylidene content of 75–87%. A combination of flexible aliphatic dithiols, including 1,6-hexanedithiol and 2,2′-(ethylendioxy)diethanethiol, and the rigid aromatic dithiol 4,4′-thiobisbenzenethiol, with rigid aromatic dialkynes, 1,3-diethynylbenzene and 1,4-diethynylbenzene, and flexible dialkynes, including propargyl ether and 1,7-octadiyne, have been used to prepare poly(vinylidene sulfide)s. The copolymerization of flexible dithiols with rigid aromatic dialkynes or vice versa results in high molecular weight polymers, Mw up to 259.000, with low polydispersities. However, polyhidrothiolation of flexible dialkynes with flexible dithiols is much less efficient and usually results in the formation of oligomers. The interplay of the IPr and pyridine ligands on the RhCl(IPr)(py)(η2-coe) catalyst, which controls the regioselectivity of the alkyne insertion step towards the branched vinyl sulfide, is key in the preparation of these poly(vinylidene sulfide)s.

ОКИСЛЕНИЕ ХИРАЛЬНЫХ БИС-ТИОЭФИРОВ РЯДА 2(5Н)-ФУРАНОНА ДО ДИСУЛЬФОКСИДОВ

Novel disulfinyl derivatives based on 3,4-dichloro-2(5H)-furanone, aliphatic dithiols, and monoterpene alcohols were synthesized. Chiral bis-thioethers in the molecules of which the dithiol fragment links two five-membered cycles at C4 atoms were obtained in the reactions of 5(S)-(l-menthyloxy)- and 5(S)-(l-bornyloxy)-2(5H)-furanones with ethane-1,2-dithiol and propane-1,3-dithiol in acetone in basic medium. The action of an excess of m-chloroperoxybenzoic acid (2.0–3.2 equiv.) on bis-thioethers led to the formation of the corresponding mono- and disulfoxides bearing l-menthol or l-borneol fragments at the 5th position of the lactone ring. The methods of column chromatography and fractional recrystallization were used for the isolation of individual products. The structure of the synthesized heterocycles was proved by IR and NMR spectroscopy, and their composition was confirmed by high-resolution mass spectrometry. The molecular structure of the three disulfoxides was characterized by X-ray diffraction analysis.

Hydrogel networks by aliphatic dithiol Michael addition to glycidylmethacrylated gelatin

Functionalization of gelatin with glycidylmethacrylate (GMA-gelatin) enables network formation employing the double bond, so that the reaction is orthogonal to the inherent functional groups in the biomacromolecule. Here, network formation by crosslinking of GMA-gelatin with hexane 1,6-dithiol or nonane 1,9-dithiol to tailor properties and enable a shape-memory effect is shown by 1H NMR and FT-IR spectroscopy. Hydrogel swelling (460–1900 vol%) and mechanical properties (Young’s modulus E = 59–512 kPa, elongation at break εb = 44–127%) depended on the molecular composition of the networks and temperature. Increased crosslinker length, thiol:methacrylate molar ratio, and precursor concentrations led to denser networks. Change of properties with temperature suggested adoption of triple helices by gelatin chains, forming physical netpoints at lower temperatures (< 20 °C). However, the limited freedom of the gelatin chains to move allowed only a minimal extent of triple helices formation, as it became apparent from the related signal in wide-angle X-ray scattering and the thermal transition associated to triple helices in some networks by DSC. The presented strategy is likely transferable to other biomacromolecules, and the results suggest that too short crosslinkers may result in a significant amount of grafting rather than network formation.Graphic abstract

ChemInform Abstract: Calcium Carbide as a Convenient Acetylene Source in the Synthesis of Unsaturated Sulfides, Promising Functionalized Monomers.

AbstractThe atom‐economic thiol‐yne click reactions of heterocyclic thiols or aliphatic dithiols with from calcium carbide in situ generated acetylene lead to the corresponding vinyl sulfides or bis(thiovinyl)ethers.

Calcium carbide as a convenient acetylene source in the synthesis of unsaturated sulfides, promising functionalized monomers

Calcium carbide was studied as a useful solid-state reagent to incorporate acetylene unit into synthetic procedures. Atom-economic thiol-yne click reaction was successfully performed with single and double additions. Heterocyclic thiols and aliphatic dithiols reacted with acetylene generated in situ from calcium carbide to afford corresponding vinyl sulfides and bis(thiovinyl)ethers in good to high yields.

Synthesis of blue light emitting and electrochromic polyimidothioethers with diphenylpyrenylamine chromophore via thiol-ene reaction

Two novel blue light emitting and electrochromic polyimidothioethers (PITEs) were prepared from a new diphenylpyrenylamine-based bismaleimide and two commercially available dithiols via the thiol-ene Michael addition polymerization. These two PITEs were readily soluble in various organic solvents and could be cast into robust films on the glass substrate. The PITEs exhibited strong UV–vis absorption bands at 316–319 nm in NMP solution and their photoluminescence spectra showed maximum bands around 473–477 nm in the blue region. The PITE Py-C 2 derived from an aliphatic dithiol of 1,2-ethanedithiol was optically transparent in the visible region and fluoresced with a higher quantum yield (ΦPL = 32 %) compared to that derived from an aromatic dithiol of 4,4’-thiobisbenzenethiol. Cyclic voltammetry studies indicated that they show a moderate stability in the anodic oxidation process, but the cathodic reduction process is irreversible. The PITE films exhibited a noticeable electrochromic behavior, with color change from a colorless neutral state to a purple oxidized state and an orange reduced state.

Sensitive Surface-Enhanced Raman Spectroscopy (SERS) Detection of Organochlorine Pesticides by Alkyl Dithiol-Functionalized Metal Nanoparticles-Induced Plasmonic Hot Spots

In this work, we report the detection of the organochlorine pesticides aldrin, dieldrin, lindane, and α-endosulfan by using surface-enhanced Raman spectroscopy (SERS) and optimization of the SERS-sensing substrate. In order to overcome the inherent problem of the low affinity of the above pesticides, we have developed a strategy consisting of functionalization of the metal surface with alkyl dithiols in order to achieve two different goals: (i) to induce the nanoparticle linkage and create interparticle junctions where sensitive hot spots needed for SERS enhancement are present, and (ii) to create a specific environment in the nanogaps between silver and gold nanoparticles, making them suitable for the assembly and SERS detection of the analyzed pesticides. Afterward, an optimization of the sensing substrate was performed by varying the experimental conditions: type of metal nanoparticles, molecular linker (aromatic versus aliphatic dithiols and the length of the intermediate chain), surface coverage, laser excitation wavelength. From the adsorption isotherms, it was possible to deduce the corresponding adsorption constant and the limit of detection. The present results confirm the high sensitivity of SERS for the detection of the organochlorine pesticides with a limit of detection reaching 10(-8) M, thus providing a solid basis for the construction of suitable nanosensors for the identification and quantitative analysis of this type of chemical.

Energy transfer between lead sulfide quantum dots in the liquid phase

Förster resonant energy transfer (FRET) from smaller sized PbS Quantum Dots (QDs) to larger sized ones occurs in the liquid phase when adjacent QDs are brought in close proximity by the bridging action of the two SH groups in aromatic or aliphatic dithiols. Signatures of FRET were observed by the lowering of the fluorescence peak corresponding to the smaller particle group and intensification of the peak corresponding to the larger particle group in a mixture of the two in the liquid phase. The suspensions of the two QDs size distributions were mixed in a ratio such that total surface area of the smaller QDs was equal to that of the larger QDs. A 10–13% size deviation in each PbS QDs group also allows this phenomenon to be observed in these samples and is manifested by red-shift and broadening of the fluorescence peak. The ratio of the absorption peak intensity corresponding to the two groups of PbS QDs in the mixture remains the same.

Discriminative response of aliphatic and aromatic dithiol in the self-assembly of gold nanoparticles

Self-assembly of gold nanoparticles (Au NPs) in the presence of an aliphatic dithiol and an aromatic dithiol of similar molecular length in an EtOH–H2O mixture was found to be remarkably different. Aromatic dithiols lead to the predominant formation of dimers of Au NPs. Our results strongly suggest the potential use of aromatic dithiol for the easy preparation of controllable and well-defined nanostructures of Au NPs.

Synthesis, structure, properties and immobilization on a gold surface of the monoribbed-functionalized tris-dioximate cobalt(ii) clathrochelates and an electrocatalytic hydrogen production from H+ ions

The cycloaddition of the mono- and dichloroglyoximes to the cobalt(II) bis-α-benzyldioximate afforded the cobalt(II) mono- and dichloroclathrochelates in moderate yields (40-60%). These complexes undergo nucleophilic substitution of their reactive chlorine atoms with aliphatic amines, alcohols and thiolate anions. In the case of ethylenediamine and 1,2-ethanedithiol, only the macrobicyclic products with α,α'-N(2)- and α,α'-S(2)-alicyclic six-numbered ribbed fragments were obtained. The cobalt(II) cage complexes with terminal mercapto groups were synthesized using aliphatic dithiols. The crystal and molecular structures of the six cobalt(II) clathrochelates were obtained by X-ray diffraction. Their CoN(6)-coordination polyhedra possess a geometry intermediate between a trigonal prism and a trigonal antiprism, and the encapsulated cobalt(II) ions are shifted from their centres due to the structural Jahn-Teller effect with the Co-N distances varying significantly (by 0.10-0.26 Å). The electrochemistry of the complexes obtained was studied by cyclic voltammetry (CV). The anodic waves correspond to the quasi-reversible Co(2+/3+) oxidations, whereas the cathodic ranges contain the quasi-reversibile waves assigned to the Co(2+/+) reductions; all the cobalt(i)-containing clathrochelate anions formed are stable in the CV time scale. The electrocatalytic properties of the cobalt complexes obtained were studied in the production of hydrogen from H(+) ions: the addition of HClO(4) resulted in the formation of the same catalytic cathodic reduction Co(2+/+) waves. The controlled-potential electrolysis with gas chromatography analysis confirmed the production of H(2) in high Faraday yields. The efficiency of this electrocatalytic process was enhanced by an immobilization of the complexes with terminal mercapto groups on a surface of the working gold electrode.

Determination of amines based on their interaction with QDs: Effect of the formation QD-assemblies

Assemblies of closed nanoparticles have focused interest because they exhibit new optical and chemical properties. The use of a 1D covalent strategy for quantum dots-assemblies has been proposed in this work as novelty. It was studied the effect of use different dithiols, including aromatic and aliphatic dithiol compounds, on the formation of QDs-assemblies in order to establish the influence of the linker's structure on the geometry of the assemblies, and hence on their properties. As a second part of the work, the changes on analytical response to analytes thanks to the formation of QDs-assemblies when dithiols are added were studied for firs time. For this study, some biogenic amines were selected as target analytes. We observed an improvement of 2.7–4 times in the sensitivity, expressed as slope of the calibration graph, when the dithiols were added to the system obtaining QDs-assemblies.

Structure and conductivity of self-assembled films of gold nanoparticles

Self-assembled thin films of gold nanoparticles of 4–5nm, prepared on glass using aliphatic dithiols of different hydrocarbon chain lengths as interparticle linker molecules, have been studied by x-ray methods and dc conductivity. X-ray data revealed small spacer-dependent cluster size variations in the films. Conductivity, in the temperature range of 4.2–300K, showed a strong relation with spacer length, indicating that different mechanisms of conduction from metal-like through hopping to tunneling dominate, depending on temperature range and particle spacing. The results demonstrate that the electronic and optical properties of such films can be precisely controlled by interparticle distance.

Solvent-free derivatization of pristine multi-walled carbon nanotubes with dithiols

We report on direct solvent-free derivatization of pristine multi-walled carbon nanotubes (MWNTs) with aliphatic dithiols (1,4-butanedithiol, 1,6-hexanedithiol and 1,8-octanedithiol), by means of heating at 130–150 °C under reduced pressure. This method requires no additional chemical activation and about 2 h only for completion. Studies by high-resolution transmission electron microscopy and scanning electron microscopy with energy dispersive X-ray spectroscopy showed that dithiol-derivatized MWNTs have a high affinity to ZnCl 2 in solution, which covers the nanotubes with a dense amorphous layer. According to PM3 semi-empirical calculations, employing a closed-cap zigzag (10,0) single-walled carbon nanotube (SWNT) model incorporating a Stone-Wales defect, site-specificity of the addition depends on the mutual position of pentagons. If the nanotube contains pyracylene units or Stone-Wales defect, the addition takes place on their 6,6 or 7,7 bonds, respectively, whereas for isolated pentagons, preferential reaction sites are their C–C bonds. Ideal graphene sheet sidewalls with cylindrical curvature are relatively inert (although one cannot discard the possibility to activate the reaction by heating). Dithiol groups introduced in the way proposed can be used as chemical linkers for anchoring metal complexes and nanoparticles to carbon nanotubes, attaching SWNTs to gold tips for atomic force and scanning tunneling microscopy, and potentially for adsorption and concentration of trace metal ions.

Molecular structure and thermal stability of α-halogen-gem-dithiols

The electronic structure of α-halogen-gem-dithiols RC(SH)2CH2X (R = Me, Ph; X = F, Cl, Br, I) was studied by quantum chemistry methods. Four most stable rotamers were located, differing in the mutual orientation of the thiol groups and the halogen atom. The thermodynamic and kinetic characteristics of the thermolysis of α-halogen-gem-dithiols were obtained. Thermolysis of chlorine- and bromine-substituted gem-dithiols depends on the properties of the medium, namely, in aprotic media aromatic dithiols form trithianorbornane derivatives while aliphatic dithiols form thiirane derivatives. In an aqueous medium (R = Me, Ph), water promoted elimination of hydrogen sulfide with the formation of corresponding thiones is more preferable. Thermolysis of aliphatic iodine-substituted gem-dithiols proceeds as bimolecular deiodination resulting in the formation of a new C-C bond.

Synthesis of Sulfone‐Containing Monomers and Polymers Using Cationic Cyclopentadienyliron Complexes

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of macrocyclic aliphatic disulfide oligomers from dithiols by oxidative coupling with oxygen using a copper‐amine catalyst

AbstractA new effective method is provided for the synthesis of macrocyclic aliphatic disulfide oligomers by catalytic oxidation of aliphatic dithiols with oxygen in the presence of a copper‐amine catalyst. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Synthesis of sulfone‐containing monomers and polymers using cationic cyclopentadienyliron complexes

AbstractThe synthesis of sulfone‐containing monomers with pendent cationic cyclopentadienyliron (CpFe+) moieties has been accomplished via nucleophilic aromatic substitution of dichloroarene complexes with a number aliphatic dithiols. These complexes were further oxidized using m‐CPBA to give the sulfone‐based monomers. Polymerization of the sulfone‐based monomers with O‐containing nucleophiles produced the sulfone‐based polymers. Direct nucleophilic aromatic substitution of dichloroarene complexes with dinucleophiles allowed for the formation of organoiron sulfide‐based polymers. Oxidation of these polymers led to the formation of sulfone polymers with the pendent iron moieties. The organometallic monomers and polymers were found to be more soluble in polar solvents in comparison to their organic analogues.

Synthesis and ring‐opening polymerization of co‐cyclic(aromatic aliphatic disulfide) oligomers

AbstractAn effective approach was presented for the synthesis of co‐cyclic(aromatic aliphatic disulfide) oligomers by catalytic oxidation of aromatic and aliphatic dithiols with oxygen in the presence of a copper‐amine catalyst. The aromatic dithiols can be 4,4′‐oxybis(benzenethiol), 4,4′‐diphenyl dithiol, 4,4′‐diphenylsulfone dithiol. The aliphatic dithiols can be 1,2‐ethanedithiol, 2,3‐butanedithiol, 1,6‐hexane dithiol. The co‐cyclic(aromatic aliphatic disulfide) oligomers were characterized by gradient HPLC, MALDI‐TOF‐MS, GPC, 1H‐NMR, TGA, and DSC techniques. The glass transition temperatures of these co‐cyclics ranged from −11.3 to 56.6°C. In general, these co‐cyclic(aromatic aliphatic disulfide) oligomers are soluble in common organic solvents, such as CHCl3, THF, DMF, DMAc. These co‐cyclic oligomers readily underwent free radical ring‐opening polymerization in the melt at 180°C, producing linear, tough and high molecular weight poly(aromatic aliphatic disulfide)s. The glass transition temperatures of these polymers ranged from −3.7 to 107.8°C that are higher than those of corresponding co‐cyclics. Copyright © 2003 John Wiley &amp; Sons, Ltd.

Mixed Self-Assembled Multilayer of 4,4‘-Dimercaptobiphenyl and 1,8-Octanedithiol

Mixed multilayers from aromatic (biphenyl) and aliphatic (octane) dithiols, using Cu(II) ions, have been prepared and characterized by ellipsometry, FTIR, and XPS. The data support the formation of...