John V. Hanna

Novel rare gas interstitial fullerenes of C60 with Ar, Kr and Xe

Abstract In this paper we report the formation and characterisation of rare gas C 60 interstitial compounds of Ar, Kr and Xe. The materials were produced by hot isostatically pressing (HIP) the fullerene solid at temperatures between 200 and 550 °C and under rare gas pressures in the range 170–200 MPa. With this method, we have been able to make rare gas fullerene compounds with stoichiometries of Ar 1 C 60 , Kr 0.9 C 60 and Xe 0.66 C 60 . Thermal gravimetric analysis (TGA) showed that the HIPed materials contained rare gas after treatment, and gave a method for determining the stoichiometry. TGA also enabled the thermal stabilities of these materials with respect to rare gas loss to be investigated. The structure of the rare gas fullerenes was characterised by both X-ray and neutron powder diffraction. By Rietveld analysis of the diffraction data it has been shown that only the octahedral interstices of the fullerene face centred cubic (FCC) lattice were occupied by the rare gas, and the site occupancy of this site gave a stoichiometry agreeing within 5% of that obtained from TGA. The face centred to primitive cubic orientational ordering phase transition for these rare gas fullerenes was studied using neutron diffraction. The transition temperature was found to decrease as the size of the rare gas increases. This lowering is a result of the net weakening of the c 60 c 60 interaction potential, as the rare gas pushes the c 60 molecules slightly apart; a consequence of not only their size but also a result of their thermal motion (internal pressure) within the interstitial site. Differential scanning calorimetry (DSC) confirmed the transition temperatures obtained from neutron diffraction. In addition, transmission electron microscopy (TEM) and 13 C NMR studies have been performed on these materials and the results are discussed.

The role of short-range diffusion in solvent-assisted mechanochemical synthesis of metal complexes

The role of short-range diffusion in solvent-assisted mechanochemical synthesis is demonstrated in studies of a polymorphic transition and a ligand dissociation reaction involving copper(I) thiocyanate complexes.

Composition of size exclusion fractions of swamp water humic and fulvic acids as measured by solid state NMR and pyrolysis-gas chromatography-mass spectrometry

Abstract Organics from Neranie swamp water, collected from the Myall Lakes district, New South Wales, Australia, have been fractionated by gel permeation chromatography and analysed by 13C nuclear magnetic resonance (NMR) spectroscopy and pyrolysis-gas chromatography-mass spectrometry (py-GC-MS). The results from these techniques demonstrate that: (1) low ( M w daltons ) and high ( M w > 74,830 daltons ) weight average molecular weight humic acid fractions have aliphatic chains which are relatively unbranched compared to those humic acids fractions of intermediate molecular weight. (2) Alcoholic carbon, mainly as carbohydrates, is more predominant in the highest weight average molecular weight material, and carboxylic carbon is more predominant in molecules with M w 2800–8270 daltons. (3) If it is assumed that CP/MAS NMR data are at least semi-quantitative, polyoxyethers or unsaturated ethers account for as much as one half of the oxygen in humic low molecular weight ( M w daltons ) materials. (4) Lignin related components of the fractions concentrate in the region M w = 74,830−27,930 daltons . If there are not multiple lignin sources, these data indicate that lignin degradation is somewhat selective about weak links. (5) The fulvic acids are more homogeneous, with different molecular weight fractions having similar structures.

Chemical Composition Of Humic Acids: A Comparison With Precursor ‘light Fraction’ Litter From Different Vegetations Using Spectroscopic Techniques

Humic acids from a range of Italian soils and the residual suspended organic material (light fraction litter) associated with them have been studied by pyrolysis gas chromatography mass spectrometry, solid state nuclear magnetic resonance spectroscopy, and infra-red spectroscopy. Although the major vegetation types on the soils differ considerably, spectra of humic acids from soils with different major vegetation types were similar. Because no relationship between humic acid structure and major vegetation type was observed, gross assumptions about humic acid structure should not be drawn from a knowledge of macro-vegetation types on soils. Light fraction litter in the soils from minor vegetation may be more significant in affecting the eventual structure of the humic acids.

1H CRAMPS NMR derived hydrogen distributions in various coal macerals

Abstract The distribution of protons bonded to sp 2 and sp 3 hybridized carbons in a number of macerals including liptinites and inertinites, has been investigated by 13 C cross polarization magic angle spinning (CP/MAS) and 1 H combined rotation and multiple pulse nuclear magnetic resonance spectroscopy (CRAMPS). Some preliminary 1 H- 13 C solid state heterocorrelation spectra of coals and one maceral have also been obtained. CRAMPS was only successful in resolving acidic, aromatic/alkenic, carbohydrate and aliphatic protons in the macerals. The semifusinites had variable (0.38→0.58) proton aromaticities and (0.40→0.84) carbon aromaticities, and the liptinite macerals had a low (0.06) fraction of protons attached to sp 2 hybridized carbon. Of the nine resinite samples examined, one (Hornerstown) was clearly identified to be a naturally occurring polymer of styrene. The CRAMPS spectra of the other seven were useful, identifying them as carboxylic acids. Two dimensional 1 H- 13 C heteronuclear solid state spectroscopy was successful in resolving two types of aliphatic hydrogen in the selected coals studied, with longer range coupling able to be observed in the structurally simpler Hornerstown resinite by implementation of two WIM-24 cross-polarization cycles.

Changes in organic structural group composition of humic and fulvic acids with depth in sediments from similar geographical but different depositional environments

A series of soil and swamp sediments from the Myall Lake National Park region, New South Wales, Australia have been studied by traditional wet chemical techniques and by solid state 13C NMR. Amino acid, carbohydrate, total acidity, phenolic, phenoxy and alkyl contents have been measured. Results obtained support previous literature reports that NMR carboxyl content measurements correlate better with total acidity than wet chemical COOH measurements. Large discrepancies (×20) between NMR and traditional chemical methods of measuring carbohydrate contents were also observed. The carbohydrate content of humic and fulvic acids measured by NMR or traditional methods drops rapidly with increasing soil or sediment depth probably because of metabolization by microorganisms. Fulvic acids contain more carboxylic acid and decreased alkyl carbon than their humic acid counterparts from the same source. The structure of humic acids however more closely reflect their depositional environment. For example, more phenolic and phenoxy carbon is present in forest humic acids because of the high lignin input.

The degradation of wood in old Indian Ocean shipwrecks

Abstract Woods from five old ships wrecked in the Indian Ocean over the period 1629–1886 have been studied by Fourier transform infra-red spectroscopy, by solid state 13 C nuclear magnetic resonance spectroscopy and by pyrolysis gas chromatography/mass spectrometry. The results from all three techniques strongly support each other. It is shown that samples of outer wood in closer proximate contact with the marine environment have lost carbohydrates, whereas the inner wood is relatively intact. There appears to be no correlation between the age of ships and degradation, however one wreck ( James Matthews ) which is located at an anaerobic site appears to have undergone little or no degradation, unlike the samples obtained from aerobic sites.

Structural and ion exchange properties of nanocrystalline Si-doped antimony pyrochlore

Antimonic acid Sb2O5·4H2O with the pyrochlore structure is a well known ion-exchanger that is selective for Sr2+ in mildly acidic solution. An enhancement of the ion exchange properties of antimony-based pyrochlore materials, with respect to Cs+ and Sr2+, was previously reported by Moller and co-workers to be achievable if Si4+ is incorporated during synthesis of these materials (T. Moller, R. Harjula, M. Pillinger, A. Dyer, J. Newton, E. Tusa, S. Amin, M. Webb and A. Araya, J. Mater. Chem., 2001, 11, 1526–1532). The present study aims to shed light on the role of Si4+ in the pyrochlore structure and its influence on the ion-exchange properties. A series of samples were prepared with increasing concentrations of Si added during preparation. X-Ray powder diffraction and electron microscope observations indicate that the average particle size of the antimony pyrochlores decreases as Si concentration increases. Refinement of X-ray powder data shows a small and abrupt decrease in unit cell volume at an added Si concentration corresponding to about 10 atom%. For undoped samples 29Si solid-state MAS NMR showed only a single sharp resonance at −75 ppm assigned to Si(OH)4 species located within the hexagonal channels of the pyrochlore structure. The increasing addition of Si to the reactant mixture gave rise to a progressive increase in the intensity of resonances from hydrated amorphous silicate species. Base treatment succeeded in removing only the resonances due to these silicate species, leaving the resonance assigned to structural Si unaffected. These data are taken as confirmation of the assignment of the sharp −75 ppm resonance to isolated species Si(OH)4 within the pyrochlore tunnels. Neutron powder diffraction of partially dehydrated samples shows the existence of two pyrochlore phases that appear to differ slightly in their unit cell parameters and confirms that incorporation of Si4+ into the pyrochlore structure and a reduction in water content cause volume contraction of the cubic cell. The slight unit cell contraction resulting from Si incorporation is hypothesised to be responsible for enhanced Cs+ selectivity of samples containing Si.

Structural and spectroscopic studies of some copper(I) halide tert-butyl isocyanide adducts.

Single-crystal structural characterizations confirm the existence of the unusual 1 : 4 copper(I) halide : unidentate ligand adducts [Cu(CNt-Bu)4]X for X = Cl, Br (two forms), I (the chloride and one form of the bromide being solvated) with crystal packing dominated by stacks of interleaving cations. Cu-C range between 1.941(2) and 1.972(4) A. The structure of the 1 : 2 chloride complex is also recorded, being [ClCu(CNt-Bu)2], with the copper(I) atom environment trigonal planar, while CuCN : (CNt-Bu) (1 : 1) is a single-stranded polymer which spirals about a crystallographic 3-axis (CN scrambled), the ligands being pendant from the ...CuCNCuCN... string. The (5Cu static broadline NMR spectra of [Cu(CNt-Bu)4]I and [Cu(CNt-Bu)4]Br.H2O in the solid state exhibit dominant, narrow -1/2 <--> +1/2 central transition resonances and associated +/-1/2 <--> +/-3/2 satellite transition resonances which are characteristic of first-order quadrupole broadened systems, while associated high-resolution 65Cu MAS NMR data provide accurate measurement of the 65Cu isotropic chemical shifts. Both approaches provide complete data on the quadrupole and chemical shift interactions which contribute to these spectra. Far-IR spectra of products of reactions involving a range of CuX : t-BuNC ratios reveal the existence of 1 : 1.5 adducts for X = Br, I. Metal-carbon and metal-halogen bands are assigned in the far-IR spectra, which indicate a binuclear double halogen-bridged structure for the 1 : 1.5 complexes.

X-Ray and spectroscopic re-investigation of urotropine-p-nitrophenol complex

Abstract The product of the reaction between urotropine and p-nitrophenol, reported as a 1:1 adduct that belongs to the triclinic P1 space group, is, in fact, a 1:2 [C6H12N4]·[p-HOC6H4NO2]2·[H2O] hydrate that crystallizes in the monoclinic C2 space group. In the crystal structure, one nitrogen atom of the urotropine moiety is linked by a hydrogen bond to the hydroxyl group of a p-nitrophenol molecule [ N ⋯ O =2.655 (7) A ]; the [C6H12N4]·[p-HOC6H4NO2] entities are linked into a linear one-dimensional chain through the lattice water molecule [ O ⋯ N =2.871 (8), O ⋯ O =2.878 (7) A ]. The other p-nitrophenol moiety is disordered over two positions across the two-fold axis; its interaction with adjacent water molecules [ O ⋯ O =2.53 (1), 2.57xa0(2)xa0A] holds neighboring chains together. The FTIR spectrum of the complex in the solid indicate the formation of OH⋯N intermolecular hydrogen bond described by an asymmetric double minimum potential and weak Zundels polarizability. The spectroscopic measurements in solution demonstrate the dissociation of the complex observed in the solid and prove the presence of the 1:1 complexes urotropine–p-nitrophenol. In these complexes no proton transfer from p-nitrophenol to urotropine is observed.