User:Mikheaven

PUBLICATIONS (as of 2011 May)

Antesberger, J., G. W. V. Cave, M. C. Ferrarelli, M. W. Heaven, C. L. Raston and J. L. Atwood (2005). "Solvent-free, direct synthesis of supramolecular nano-capsules." Chemical Communications(7): 892-894. The single step direct synthesis of pyrogallol[4]arene via a solvent free protocol yields the pure product as a self-assembled nanocapsule, comprised of six macrocyclic building blocks. © The Royal Society of Chemistry 2005.

Atwood, J. L., L. J. Barbour, M. W. Heaven and C. L. Raston (2003). "Association and orientation of C70 on complexation with calix[5]arene." Chemical Communications 9(18): 2270-2271. Calix[5]arene and C70 in p-xylene form a ball-and-socket supramolecular complex with the C5 axis of the fullerene tilted 40Å relative to the symmetry axis of the calixarene, the extended structure is comprised of well-separated zigzag sheets of C70 molecules.

Atwood, J. L., L. J. Barbour, M. W. Heaven and C. L. Raston (2003). "Controlling van der Waals contacts in complexes of fullerene C60." Angewandte Chemie - International Edition 42(28): 3254-3257. An impurity aids in the purification of C60. A 1:1 complex of C60 and calix[5]arene crystallizes from toluene (see picture) with the fullerenes organized in a one-dimensional zigzag array shrouded by a sheath of calixarenes. The complex forms in the presence of other globular molecules including C70, the major impurity in fullerite.

Atwood, J. L., L. J. Barbour, M. W. Heaven and C. L. Raston (2003). "Synthesis of 2-imino-5-phenylimidazolidin-4-one and the structure of its trifluoroacetate salt." Journal of Chemical Crystallography 33(3): 175-179. The trifluoroacetate salt of 2-imino-5-phenylimidazolidin-4-one has been prepared and characterized crystallographically. The complex crystallizes in the monoclinic space group C2, with a = 27.894(3) Å…, b = 6.2616(7) Å…, c = 7.1989(8) Å…, V = 93.176(2)Å2. The extended structure consists of neutral, one-dimensional, hydrogen-bonded ribbons incorporating both ionic species.

Buntine, M. A., G. J. Gutsche, W. S. Staker, M. W. Heaven, K. D. King and W. D. Lawrance (2001). "Singlet methylene removal rate constants from the (0,1,0) vibrational level: enhancement via complex-mediated vibrational relaxation." Zeitschrift fur Physikalische Chemie 215(6): 795-809. The technique of laser flash photolysis/laser absorption has been used to obtain absolute removal rate constants for singlet methylene, 1CH2 (a1At), from the vibrationally excited (0,1,0) level. (0,1,0) removal rate constants are reported for the 13 species N2, CH4, C2H4, C2H6, CH2CO, CH3Cl, CH3OC2H5, CH3OH, CH3CN, CH3F, CF4, C2F4, and C2F6. With the exception of the slowest three reacting species, CH4, CH3F and C2F4, for the species which are known to react from the (0,0,0) level the removal rate constants are essentially identical for the (0,0,0) and (0,1,0) levels. The removal rate constants for CH4, CH3F and C2F4 increase by factors of 1.2, 2.2 and 1.45 respectively with vibrational excitation to (0,1,0). For the species N2, CF4, and C2F6, which do not appear to react from (0,0,0), the removal rate constants are increased in the (0,1,0) state. The increase is very large for N2, for which the factor is 4, and is substantial for CF4 and C2F6, which show factors of 2.55 and 2.7 respectively. The increased removal rate constants for N2and for the fluorine-containing species are attributed to the formation of an association complex between 1CH2 (0,1,0) and the partner followed by dissociation to 1CH2 (0,0,0) and the partner. We refer to this as complex-mediated vibrational relaxation (CMVR). Removal rate constants for the (0,0,0) level are likely to be in error when experimental conditions allow the simultaneous production of 1CH2 (0,1,0) from the methylene precursor and where CMVR, which typically has comparable efficiency to collision induced intersystem crossing, provides a growth term for the (0,0,0) population. The species for which CMVR is likely to be significant are those for which reaction is either absent or a minor pathway and where there are electron-rich centres for the empty orbital of 1CH2 to "bind", allowing the formation of a long lived 1CH2-collider complex. Copyright © Oldenbourg Wissenschaftsverlag GmbH 2001

Heaven, M. W., G. W. V. Cave, R. M. McKinlay, J. Antesberger, S. J. Dalgarno, P. K. Thallapally and J. L. Atwood (2006). "Hydrogen-bonded hexamers self-assemble as spherical and tubular superstructures on the sub-micron scale." Angewandte Chemie - International Edition 45(37): 6221-6224. Six packs: Hydrogen-bonded pyrogallol[4]arene hexameric nanocapsules self-assemble into spheres (A; see picture), tubules, and combinations of both (B) on the sub-micron scale. These assemblies were characterized by using dynamic light scattering, scanning electron microscopy, transmission electron microscopy (see inset), and atomic force microscopy techniques. (Figure Presented). Â© 2006 Wiley-VCH Verlag GmbH & Co. KGaA.

Heaven, M. W., A. Dass, P. S. White, K. M. Holt and R. W. Murray (2008). "Crystal structure of the gold nanoparticle [N(C8H17)4][Au25(SCH2CH2Ph)18]." Journal of the American Chemical Society 130(12): 3754-3755. We report the crystal structure of the thiolate gold nanoparticle [TOA+][Au25(SCH2CH2Ph)18-], where TOA+ = N(C8H17)4+. The crystal structure reveals three types of gold atoms: (a) one central gold atom whose coordination number is 12 (12 bonds to gold atoms); (b) 12 gold atoms that form the vertices of an icosahedron around the central atom, whose coordination number is 6 (five bonds to gold atoms and one to a sulfur atom), and (c) 12 gold atoms that are stellated on 12 of the 20 faces of the Au13 icosahedron. The arrangement of the latter gold atoms may be influenced by aurophilic bonding. Together they form six orthogonal semirings, or staples, of −Au2(SCH2CH2Ph)3− in an octahedral arrangement around the Au13 core.

Heaven, M. W., G. F. Metha and M. A. Buntine (2001). "Reaction pathways of singlet silylene and singlet germylene with water, methanol, ethanol, dimethyl ether, and trifluoromethanol: An ab initio molecular orbital study." Journal of Physical Chemistry A 105(7): 1185-1196. Ab initio molecular orbital calculations have been performed to explore the reaction potential energy surfaces of singlet silylene and germylene with water, methanol, ethanol, dimethyl ether, and trifluoromethanol. We have identified two new reaction channels on each reaction surface, except for reactions involving dimethyl ether. The previously unreported reaction channels involve H2 elimination following the initial formation of an association complex. For reactions involving singlet silylene and water, a simple activated complex theory (ACT) analysis predicts that these newly identified reaction channels are equally likely to be accessed as the previously identified 1,2 hydrogen atom shift channels. For reactions involving singlet germylene and water, a similar ACT analysis predicts that the H2-elimination channels will occur in preference to the 1,2 hydrogen shift. Indeed, the room-temperature rate constants for H2 elimination from the germanium complex are predicted to be approximately 5 orders of magnitude greater than for the H atom migration channel. Â© 2001 American Chemical Society.

Heaven, M. W., G. F. Metha and M. A. Buntine (2001). "Reaction rate constants for singlet silylene and singlet germylene with water, methanol, ethanol, dimethyl ether and trifluoromethanol: Competition between H-atom migration and H2 elimination." Australian Journal of Chemistry 54(3): 185-192. Stationary points on the reaction potential energy surfaces of singlet silylene and singlet germylene with water, methanol, ethanol, dimethyl ether and trifluoromethanol have been used to predict reaction rate constants for temperatures between 100 and 1500 Kelvin. We have previously identified two new reaction channels on each reaction surface, except for reactions involving dimethyl ether [J. Phys. Chem. A, 2001, 105, 1185]. The previously unreported reaction channels involve H2 elimination following the initial formation of an association complex. A simple Activated-Complex Theory (ACT) analysis predicts that in the case of singlet silylene reacting with water, the newly identified reaction channels are equally likely to be accessed as previously identified 1,2 H-atom migration channels. The H2-elimination channels are slightly disfavored upon reaction of singlet silylene with methanol and ethanol, but become the preferred reaction channels with trifluoromethanol as the reaction partner. For reactions involving singlet germylene with water and with methanol, the ACT analyses predict that the H2-elimination channels will occur in preference to 1,2 H-atom migration. Indeed, the room temperature rate constants for H2 elimination from the germanium complexes are predicted to be approximately five orders of magnitude greater than for the H-atom migration channels.

Heaven, M. W., G. M. Stewart, M. A. Buntine and G. F. Metha (2000). "Neutral tantalum-carbide clusters: A multiphoton ionization and density functional theory study." Journal of Physical Chemistry A 104(15): 3308-3316. Neutral tantalum-carbide clusters, TamCn (m = 1-6, n = 1-7), have been formed in a supersonic expansion following the reaction of tantalum and acetylene in a laser ablation source. These clusters have been subjected to multiphoton ionization at 532 and 355 nm and the mass spectra recorded in a reflectron time-of-flight mass spectrometer. The cluster distributions show a drop off after m = 4 suggesting the stabilization of clusters containing four tantalum atoms. We have investigated the structures of these clusters using density functional theory and shown that the smaller clusters tend to form fragments of face-centered cubes, culminating in the formation of a distorted cube of stoichiometry Ta4C4. The structure of Ta4C4 is shown to be a distorted tetrahedron, or "butterfly", made up of four tantalum atoms with a carbon atom bonded to each face. The theoretical calculations also indicate that clusters containing three tantalum atoms form a triangle and that there is competition for the carbon atoms to bond to either the face or the edge of the tantalum triangle. © 2000 American Chemical Society.

Verheyen, V., A. Cruickshank, K. Wild, M. W. Heaven, R. McGee, M. Watkins and D. Nash (2009). "Soluble, semivolatile phenol and nitrogen compounds in milk-processing wastewaters." Journal of Dairy Science 92(7): 3484-3493. Potable water is an essential and major input in processing our food supplies, and the continued growth in food manufacturing is placing increased pressure on this limited resource. Recycling and reuse of factory wastewater can lessen potable water use but requires a detailed understanding of wastewater properties. This study uses solid-phase extraction techniques with gas chromatography-mass spectrometry analysis to investigate trace-level semivolatile organic species in various waste and reference waters associated with the Burra Foods milk-processing plant located in Southeastern Australia. Our focus was on contaminants containing phenolic and heterocyclic nitrogen functional groups, which, because of their toxicity and persistence, may limit options for water recycling and reuse. Effluent from the wastewater treatment plant of the factory showed both the highest soluble carbon burden (47 mg/ kg) and concentrations of target compounds. The target species found in these effluents included methyl phenol (13 mg/kg), hydroxy indole (9.8 mg/kg), synthetic tolyltriazoles (5.1 mg/kg) and alkyl phenol ethoxylates (0.2 mg/kg). Given the environmental stability of the tolyltriazoles, they may act as chemical markers where these effluents are used for purposes such as irrigation. Milk evaporator condensate waters, in contrast to the effluent, contained very few target species, with only low levels of pyrrolidine and piperidine derivatives such as ethylglutarimide (450 ug/L) detected. Although there were fewer target microcontaminants overall in the potable and creek reference waters, these samples had characteristic profiles. The potable water analysis revealed hydroxy cineole (2.1 ug/L) and the creek analysis revealed dichlorohydroxyacetophenone (0.3 ug/L), which were not detected in other waters. The compounds found in the wastewaters are likely to have been derived from milk or synthetic chemicals used in factory operations. The presence of nitrogen compounds in all the different milk-processing waters suggest their likely source was milk, probably milk phosphoproteins subjected to thermal, chemical, or microbial degradation. Our benign results for the condensates suggest it may be possible to substitute condensate for potable water with minimal pretreatment, both within the plant and in other applications, such as irrigation of recreation turf. © American Dairy Science Association, 2009.

Verheyen, V., A. Cruickshank, K. Wild, M. W. Heaven, R. McGee, M. Watkins and D. Nash (2011). "Characterization of organic particulates present in milk factory process waters used for reuse along with aerobically digested effluent wastewater." Bioresource Technology 102(2): 2118-2125. Wastewater from a dairy processor is being reused and recycled both within the plant and for irrigation. Flash pyrolysis GC-MS was used to examine nitrogen and phenol containing compounds (M.W. = 35 to 450 g/mol) in the particulate fraction of the milk condensate, combined clean wastewater and aerobic bioreactor effluent. For comparison, the particulates were also prepared for standard GC-MS analyses using conventional solvent extraction methods. Compounds detected by pyrolysis GC-MS were found mostly in the bioreactor with the amino acid arginine (220 mg/kg) and the amino acid derivative 1-methyl-5-oxo-L-proline methyl ester (130 mg/kg) found at the highest concentrations. In comparison, sterols detected in the effluent were found at higher concentrations when using solvent extraction indicating some degradation with pyrolysis GC-MS. However, with few exceptions, particulates were generally found not to act as passive collectors capable of concentrating less water soluble chemicals.