Richard S. Glass

New Infrared Transmitting Material via Inverse Vulcanization of Elemental Sulfur to Prepare High Refractive Index Polymers

Polymers for IR imaging: The preparation of high refractive index polymers (n = 1.75 to 1.86) via the inverse vulcanization of elemental sulfur is reported. High quality imaging in the near (1.5 μm) and mid-IR (3-5 μm) regions using high refractive index polymeric lenses from these sulfur materials was demonstrated.

Carbamoylphosphate requirement for synthesis of the active center of (NiFe)-hydrogenases

The iron of the binuclear active center of [NiFe]‐hydrogenases carries two CN and one CO ligands which are thought to confer to the metal a low oxidation and/or spin state essential for activity. Based on the observation that one of the seven auxiliary proteins required for the synthesis and insertion of the [NiFe] cluster contains a sequence motif characteristic of O‐carbamoyl‐transferases it was discovered that carbamoyl phosphate is essential for formation of active [NiFe]‐hydrogenases in vivo and is specifically required for metal center synthesis suggesting that it is the source of the CO and CN ligands. A chemical path for conversion of a carbamoyl group into cyano and carbonyl moieties is postulated

One- to two-electron reduction of an [FeFe]-hydrogenase active site mimic: the critical role of fluxionality of the [2Fe2S] core.

The one- to two-electron reduction of mu-(1,2-ethanedithiolato)diironhexacarbonyl that has been observed under electrochemical conditions is dependent on scan rate and temperature, suggesting activation of a structural rearrangement. This structural rearrangement is attributed to fluxionality of the [2Fe2S] core in the initially formed anion. Computations support this assessment. Upon an initial one-electron reduction, the inherent fluxionality of the [2Fe2S] complex anion allows for a second one-electron reduction at a less negative potential to form a dianionic species. The structure of this dianion is characterized by a rotated iron center, a bridging carbonyl ligand, and, most significantly, a dissociated Fe-S bond. This fluxionality of the [2Fe2S] core upon reduction has direct implications for the chemistry of [FeFe]-hydrogenase mimics and for iron-sulfur cluster chemistry in general.

Inverse vulcanization of elemental sulfur with 1,4-diphenylbutadiyne for cathode materials in Li–S batteries

High sulfur content copolymers were prepared via inverse vulcanization of sulfur with 1,4-diphenylbutadiyne (DiPhDY) for use as the active cathode material in lithium–sulfur batteries. These sulfur-rich polymers exhibited excellent capacity retention (800 mA h g−1 at 300 cycles) and extended battery lifetimes of over 850 cycles at C/5 rate.

Sulfur Radical Cations

Sulfur radical cations are novel reaction intermediates that have attracted considerable attention recently. This in part is due to the renewed interest in the chemistry of radical cations in general, as well as four other factors. The first is the basis for understanding the structure and reactions of radical cations — can their inherent nature be best depicted by analogy with radicals, with cations, or is a new algorithm required? As is exemplified in this review, sulfur radical cations show novel behavior. Second, some reactions of sulfur radical cations are attracting interest for their application in organic synthesis. Third, biological electron-transfer may be mediated by sulfur and, indeed, sulfur radical cations may be intermediates in biological redox processes. Finally, materials based on tetrathiafulvalene, polythiophene, and related sulfur compounds have high electrical conductivity which may be understood in terms of p-delocalized sulfur radical cations or the related dications. Consequently, a comprehensive and critical review of this field appeared timely.

Neighboring Amide Participation in Thioether Oxidation: Relevance to Biological Oxidation

To investigate neighboring amide participation in thioether oxidation, which may be relevant to brain oxidative stress accompanying beta-amyloid peptide aggregation, conformationally constrained methylthionorbornyl derivatives with amido moieties were synthesized and characterized, including an X-ray crystallographic study of one of them. Electrochemical oxidation of these compounds, studied by cyclic voltammetry, revealed that their oxidation peak potentials were less positive for those compounds in which neighboring group participation was geometrically possible. Pulse radiolysis studies provided evidence for bond formation between the amide moiety and sulfur on one-electron oxidation in cases where the moieties are juxtaposed. Furthermore, molecular constraints in spiro analogues revealed that S-O bonds are formed on one-electron oxidation. DFT calculations suggest that isomeric sigma*(SO) radicals are formed in these systems.

A facile synthesis of trimethylsilyl thioethers

Abstract Imidazole catalyzes the reaction of thiols with hexamethyldisilazane. This procedure affords a convenient method for the synthesis of trimethylsilyl thioethers. Some aspects of the mechanism of this reaction are discussed.

New developments in selenium biochemistry: Selenocysteine biosynthesis in eukaryotes and archaea

We used comparative genomics and experimental analyses to show that (1) eukaryotes and archaea, which possess the selenocysteine (Sec) protein insertion machinery contain an enzyme, O-phosphoseryl-transfer RNA (tRNA)[Ser]Sec kinase (designated PSTK), which phosphorylates seryl-tRNA[Ser]Sec to form O-phosphoseryl-tRNA[Ser]Sec and (2) the Sec synthase (SecS) in mammals is a pyridoxal phosphate-containing protein previously described as the soluble liver antigen (SLA). SecS uses the product of PSTK, O-phosphoseryl-tRNA[Ser]Sec, and selenophosphate as substrates to generate selenocysteyl-tRNA[Ser]Sec. Sec could be synthesized on tRNA[Ser]Sec from selenide, adenosine triphosphate (ATP), and serine using tRNA[Ser]Sec, seryl-tRNA synthetase, PSTK, selenophosphate synthetase, and SecS. The enzyme that synthesizes monoselenophosphate is a previously identified selenoprotein, selenophosphate synthetase 2 (SPS2), whereas the previously identified mammalian selenophosphate synthetase 1 did not serve this function. Monoselenophosphate also served directly in the reaction replacing ATP, selenide, and SPS2, demonstrating that this compound was the active selenium donor. Conservation of the overall pathway of Sec biosynthesis suggests that this pathway is also active in other eukaryotes and archaea that contain selenoproteins.

Conformational analysis of mesocyclic polythioethers : Gas phase conformational analysis of five mesocyclic polythioethers using photoelectron spectroscopy

Abstract The helium I photoelectron spectra of the mesocyclic polythioethers 1,4-dithiacycloheptane (1,4-DTCH), 1,5-dithiacyclooctane (1,5-DTCO), 1,5-dithiacyclononane (1,5-DTCN), 1,4,7-trithiacyclononane (1,4,7-TTCN), and 1,6-dithiacyclodecane (1,6-DTCD) are reported. The conformations of these molecules in the gas phase are deduced from correlations of the observed spectra with semi-empirical MO calculations, as well as molecular mechanics analysis.

Electrochemical and chemical oxidation of dithia-, diselena-, ditellura-, selenathia-, and tellurathiamesocycles and stability of the oxidized species.

The diverse electrochemical and chemical oxidations of dichalcogena-mesocycles are analyzed, broadening our understanding of the chemistry of the corresponding radical cations and dications. 1,5-Diselenocane and 1,5-ditellurocane undergo reversible two-electron oxidation with inverted potentials analogous to 1,5-dithiocane. On the other hand, 1,5-selenathiocane and 1,5-tellurathiocane undergo one-electron oxidative dimerization. The X-ray crystal structures of the Se-Se dimer of the 1,5-selenathiocane one-electron oxidized product and the monomeric two-electron oxidized product (dication) of 1,5-tellurathiocane are reported. 1,5-Dithiocanes and 1,5-diselenocanes with group 14 atoms as ring members undergo irreversible oxidation, unlike the reversible two-electron oxidation of the corresponding silicon-containing 1,5-ditellurocanes. These results demonstrate the chemical consequences of the dication stabilities Te(+)-Te(+) > Se(+)-Se(+) > S(+)-S(+), as well as Se(+)-Se(+) > Se(+)-S(+) and Te(+)-Te(+) > Te(+)-S(+).