A New Solid-State Proton Conductor: The Salt Hydrate Based on Imidazolium and 12-Tungstophosphate

We report the structure and charge transport properties of a novel solid-state proton conductor obtained by acid-base chemistry via proton transfer from 12-tungstophosphoric acid to imidazole. The resulting material (henceforth named Imid3WP) is a solid salt hydrate that, at room temperature, includes four water molecules per structural unit. To our knowledge, this is the first attempt to tune the properties of a heteropolyacid-based solid-state proton conductor by means of a mixture of water and imidazole, interpolating between water-based and ionic liquid-based proton conductors of high thermal and electrochemical stability. The proton conductivity of Imid3WP\ub74H2O measured at truly anhydrous conditions reads 0.8 7 10-6 S cm-1 at 322 K, which is higher than the conductivity reported for any other related salt hydrate, despite the lower hydration. In the pseudoanhydrous state, that is, for Imid3WP\ub72H2O, the proton conductivity is still remarkable and, judging from the low activation energy (Ea = 0.26 eV), attributed to structural diffusion of protons. From complementary X-ray diffraction data, vibrational spectroscopy, and solid-state NMR experiments, the local structure of this salt hydrate was resolved, with imidazolium cations preferably orienting flat on the surface of the tungstophosphate anions, thus achieving a densely packed solid material, and water molecules of hydration that establish extremely strong hydrogen bonds. Computational results confirm these structural details and also evidence that the path of lowest energy for the proton transfer involves primarily imidazole and water molecules, while the proximate Keggin anion contributes with reducing the energy barrier for this particular pathway

A long-chain protic ionic liquid inside silica nanopores: Enhanced proton mobility due to efficient self-assembly and decoupled proton transport

We report enhanced protonic and ionic dynamics in an imidazole/protic ionic liquid mixture confined within the nanopores of silica particles. The ionic liquid is 1-octylimidazolium bis(trifluoromethanesulfonyl)imide ([HC8Im][TFSI]), while the silica particles are microsized and characterized by internal well connected nanopores. We demonstrate that the addition of imidazole is crucial to promote a proton motion decoupled from molecular diffusion, which occurs due to the establishment of new N-H⋯N hydrogen bonds and fast proton exchange events in the ionic domains, as evidenced by both infrared and1H NMR spectroscopy. An additional reason for the decoupled motion of protons is the nanosegregated structure adopted by the liquid imidazole/[HC8Im][TFSI] mixture, with segregated polar and non-polar nano-domains, as clearly shown by WAXS data. This arrangement, promoted by the length of the octyl group and thus by significant chain-chain interactions, reduces the mobility of molecules (Dmol) more than that of protons (DH), which is manifested by DH/Dmolratios greater than three. Once included into the nanopores of hydrophobic silica microparticles, the nanostructure of the liquid mixture is preserved with slightly larger ionic domains, but effects on the non-polar ones are unclear. This results in a further enhancement of proton motion with localised paths of conduction. These findings demonstrate significant progress in the design of proton conducting materials via tailor-made molecular structures as well as by smart exploitation of confinement effects. Compared to other imidazole-based proton conducting materials that are crystalline up to 90 \ub0C or above, the gel materials that we propose are useful for applications at room temperature, and can thus find applications in e.g. intermediate temperature proton exchange fuel cells

Mono- and bis-imidazolidinium ethynyl cations and the reduction of the latter to give an extended bis-1,4-([3]cumulene)-p-carbo-quinoid system

Sherpa Romeo yellow journal. This is the peer reviewed version. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived VersionsAn extended π-system containing two [3]cumulene fragments separated by a p-carbo-quinoid and stabilized by two capping N-heterocyclic carbenes (NHCs) has been prepared. Mono- and bis-imidazolidinium ethynyl cations have also been synthesized from the reaction of an NHC with phenylethynyl bromide or 1,4bis(bromoethynyl)benzene. Cyclic voltammetry coupled with synthetic and structural studies showed that the dication is readily reduced to a neutral, singlet bis-1,4-([3]cumulene)-p-carbo-quinoid due to the πaccepting properties of the capping NHCsYe

¹²⁵Te NMR Probes of Tellurium Oxide Crystals: Shielding-Structure Correlations

The local environments around tellurium atoms in a series of tellurium oxide crystals were probed by ¹²⁵Te solid-state NMR spectroscopy. Crystals with distinct TeO_<i>n</i> units (<i>n</i> from 3 to 6), including Na₂TeO₃, α-TeO₂ and γ-TeO₂, Te₂O­(PO₄)₂, K₃LaTe₂O₉, BaZnTe₂O₇, and CsYTe₃O₈ were studied. The latter four were synthesized through a solid-state process. X-ray diffraction was used to confirm the successful syntheses. The ¹²⁵Te chemical shift was found to exhibit a strong linear correlation with the Te coordination number. The ¹²⁵Te chemical-shift components (δ₁₁, δ₂₂, and δ₃₃) of the TeO₄ units were further correlated to the O–Te–O-bond angles. With the aid of ¹²⁵Te NMR, it is likely that these relations can be used to estimate the coordination states of Te atoms in unknown Te crystals and glasses

Relating ¹³⁹La Quadrupolar Coupling Constants to Polyhedral Distortion in Crystalline Structures

A broad series of crystalline lanthanum oxide-based materials has been investigated through high-field ¹³⁹La solid state nuclear magnetic resonance (ssNMR) spectroscopy and ab initio density functional theory (DFT) calculations. The ¹³⁹La NMR spectra of LaBGeO₅, LaBSiO₅, LaBO₃, LaPO₄·1.8H₂O, La₂(SO₄)₃·9H₂O, and La₂(CO₃)₃·8H₂O are reported for the first time. Both newly reported and literature values of ¹³⁹La quadrupolar coupling constants (<i>C</i>_Q) are related to various quantitative expressions of polyhedral distortion, including sphericity (Σ) and ellipsoid span (ϵ). The compounds were separated into two groups based upon their polyhedral distortion behavior: compounds with the general formula LaMO₃, where M is a trivalent cation; compounds with different general formulas. The ¹³⁹La <i>C</i>_Q of the LaMO₃ family was found to correlate best with ϵ. The ¹³⁹La <i>C</i>_Q of non-LaMO₃ compounds correlates adequately to ϵ but is better described by Σ. The ¹³⁹La isotropic chemical shift (δ_iso^CS) of the non-LaMO₃ compounds is negatively correlated with the lanthanum coordination number; there is insufficient data from the LaMO₃ compounds to draw conclusions relating to chemical shift. DFT calculations of NMR parameters prove to be a sensitive probe of the quality of input geometry, with predicted parameters agreeing with experiment except in cases where the crystal structure is suspect

Hair-trichomes-files, and spectrochemistry of Macroneuropteris scheuchzeri (Basal Cantabrian, Sydney Coalfield, Canada)

Hoffmann's species Neuropteris Scheuchzeri in Keferstein 1827 is generally but not exclusively identified by its 1-4 mm long trichomes or hairs, though he did not mention nor illustrate them in the diagnosis of the species.  Basal Cantabrian-age compressions of the species, including 'Odontopteris subcuneata', from Sydney Coalfield, Canada, are oxidized/macerated by Schulze's process from 3 hours to 12 days to track solubility patterns of the trichomes or hairs, and files. Proposed is also a spectrochemical model for Macroneuropteris (ex Neuropteris) scheuchzeri based on carbon 13 nuclear magnetic resonance (13C NMR) experiments, combined with Fourier transform infrared (FTIR) spectroscopy. M. scheuchzeri is chemically similar to other medullosaleans in respect to high aliphatic and low aromatic contents, though FTIR analysis signals preservation variability. Hair invariably drops from compressions during HF treatment, it is opaque, pointed and not organically attached to compressions. A secretory origin is hypothesized that requires confirmation, including explanation of physiological function. Files-hair-trichomes, besides dissolving at different rates when oxidized, are physicomorphologically distinguishable from one another; hence hair and trichomes are not synonymous, as assumed by some authors.Morphological/functional-group changes occur across the basal frond dichotomy (bfd). Apart from the 'pinnule' differences is that above bfd trifoliate foliage shows hair and trichomes, whereas below bfd 'O. subcuneata', for example, shows hair, files, and some trichomes. Most conspicuous in functional-group differences is that aliphatic side-chain branching is lower below than above bfd. It is suggested that aspects of Zimmermann's telomic theory may offer an explanation for the phenomenon.Fil: Zodrow, Erwin L.. Cape Breton University. Paleobaiogy Laboratory; CanadáFil: D`angelo, José Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Werner Zwanziger, Ulrike. Dalhousie University Halifax; CanadáFil: Chen, Banghao. Dalhousie University Halifax; Canad

Spectrochemical study of coalified Trigonocarpus grandis (Pennsylvanian tree-fern ovule, Canada): Implications for fossil-organ linkage

Five coalified ovules of the type Trigonocarpus grandis are investigated four of which co-occur with tree-fern foliage Alethopteris pseudograndinioides in the medullosalean forest (basal Cantabrian), and the fifth occurs in top Asturian D (Sydney Coalfield, Canada). Addressed are questions of variability (what is a coalified ovule?), comparison with petrified ovules, pyrolysates and the original make-up of the grandis seeds, and can similar chemistry proxy for organic connection between ovule and foliage? The results demonstrate variable preservation quality despite similar thermal-maturity levels in the geological interval in which the ovules were collected. Nevertheless, the proposed T. grandis model is based on evidence from epidermises associated with inner and outer integuments, and a two-layered nucellus with granulose exine that is covered by a diaphanous layer (tectum?) and nucellar cuticle. The latter separates the inner cuticle of the inner integumentary surface from the megaspore membrane. Parenchymatous and sclerenchymatous cell structures are rare, whereas evidence for integuments, vasculature, and sclerotesta is equivocal. Overall, these features compare with petrified seeds. 13C nuclear-magnetic resonance analysis suggests that the A. pseudograndinioides tree fern bore T. grandis seeds. Pyrolysates from low and high molecular weights can almost exclusively be grouped with alkenes and aromatics; phenolics, furan and branched alkenes; and with n-alkene/n-alkane homologous series (~ 3 to 1) for cuticles from the inner integumentary surface which suggests a cutin-based, aliphatic-rich biomacromolecule. More generally, preservation is presumed correlative with aliphatic content, but not exclusively, and organ–organ linkage by spectrochemical means certainly has potential as a new research vector in palaeobotany.Fil: Zodrow, Erwin L.. Cape Breton Universit. Palaeobotanical Laboratory; CanadáFil: Helleur, Robert. Memorial University of Newfoundland. Department of Chemistry; CanadáFil: Werner-Zwanziger, Ulrike. Dalhousie Universit. Department of Chemistry; CanadáFil: Chen, Banghao. Dalhousie Universit. Department of Chemistry; CanadáFil: D` Angelo, José Alejandro. Cape Breton Universit. Palaeobotanical Laboratory; Canadá. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentin