87,698 results

  • The C602- Fulleride Ion

    Boyd, Peter; Bhyrappa, P; Paul, P; Stinchcombe, J; Bolskar, RD; Sun, Y; Reed, CA (1995-03-15)

    Journal article
    The University of Auckland Library

    Synthetic, structural, and magnetic aspects of discrete C salts have been investigated to bring coherence to conflicting descriptions of the electronic structure of the Buckminsterfulleride(2-) ion. The C NMR chemical shift in DMSO solution appears as a broad signal at 184 ppm indicative of a ???40 ppm downfield paramagnetic shift relative to C. Variable-temperature magnetic susceptibility studies are consistent with essentially equi-energy singlet (S = 0) and triplet (S = 1) spin states. The EPR spectrum of C at 4 K consists of two signals. One signal is a typical axial triplet with 2D ??? 25 G. The second is a narrower, doublet-like signal proposed to arise from a triplet with 2D too small to be resolved. A further axial triplet signal is observed at higher temperatures and is ascribed to thermal occupation of a low-lying excited state. The presence of three triplet states is a natural consequence of the reduction of the symmetry of C from I to C as required by the Jahn-Teller theorem and observed in the X-ray crystal structure of [PPN][C ] (PPN = bis(triphenylphosphine)iminium). Collectively, the NMR, magnetic susceptibility, and EPR data show that, contrary to indications from recent EPR studies, C is paramagnetic.

    View record details
  • A D(0) TO D(2) TRANSFORMATION OF TUNGSTEN, PROMOTED BY FORMATION OF AN ORGANOIMIDO LIGAND AND INVOLVING DISRUPTION OF THE PI-PERPENDICULAR BONDING COMPONENT OF COORDINATED DIPHENYLACETYLENE

    NIELSON, AJ; Boyd, Peter; Clark, George; HUNT, PA; Metson, James; RICKARD, CEF; SCHWERDTFEGER, P (1995-05-01)

    Journal article
    The University of Auckland Library

    Synthetic, spectroscopic and structural investigations as well as theoretical calculations show that reaction of the d0, four-electron donor alkyne complex [{WCl4(PhC2Ph)}2] with the silylamines Me3SiNHR (R = CMe3, CHMe2, CH2Me, 2,6-CHMe2Ph) leads to d2, two-electron donor alkyne complexes containing organoimido ligand.

    View record details
  • Fullerides of pyrrolidine-functionalized C-60

    Sun, YP; Drovetskaya, T; Bolskar, RD; Bau, R; Boyd, PDW; Reed, CA (1997)

    Journal article
    The University of Auckland Library

    The spectral characteristics of the fulleride (1-) anions of pyrrolidine-functionalized C60 derivatives have been investigated in order to assess the degree to which the parent C60 moiety retains its distinctive redox and chromophoric properties upon functionalization. Such comparison data are necessary if C60 is to fulfill its anticipated role as a versatile electron-accepting chromophore and a multielectron reservoir. Three systems have been investigated: a simple, monomeric, N-methylpyrrolidine derivative, 1, a pyrrolidine-linked tetraphenylporphyrin/C60 dyad, 2, and a pair of bifullerenes, 3 and 4, with adjacent and remote dispositions of the C60 moieties, respectively. Near infrared spectra of the fulleride(1-) ions of these derivatives are notably similar to C601- with only small energy shifts of the band envelope. 1H and 13C NMR data on 11- are consistent with unpaired spin density confined largely to the C60 moiety rather than delocalized onto the pyrrolidine functionality. The EPR spectra of all of the pyrrolidine-functionalized fulleride(1-) species are characterized by sharp doublets (??H = 1-2 G) and g values less than the free electron value. Unlike the EPR spectrum of C601-, there is little temperature dependence of the line width. EPR evidence for ball-to-ball spin-spin interactions are observed in the fulleride of 3 but not in 4 or in the CuII/C601- metalated porphyrin dyad. The X-ray crystal structure of the porphyrin-C60 dyad 2 has been determined. It is the first X-ray structural characterization of a pyrrolidine-functionalized C60 species and confirms that the azamethine ylide addition has occurred across a 6:6 ring juncture. The crystal packing of the dyad reveals an intermolecular interaction of the C60 ball nestled in remarkably close approach to the porphyrin plane. The closest approach of a fullerene carbon atom to the mean plane of the porphyrin is ca. 2.75 ??. This interaction is notably similar to that envisaged for porphyrin-functionalized chromatographic supports used to separate fullerenes. A novel donor/acceptor relationship is proposed to account for this close interaction.

    View record details
  • Isolation of protonated arenes (wheland intermediates) with BArF and carborane anions. A novel crystalline superacid

    Reed, CA; Fackler, NLP; Kim, KC; Stasko, D; Evans, DR; Boyd, PDW; Rickard, CEF (1999)

    Journal article
    The University of Auckland Library

    Protonated arenes are widely accepted intermediates in electrophilic aromatic substitution chemistry.1 Known as Wheland intermediates, but more correctly ascribed to Pfeiffer and Wizinger,2,3 they have been characterized by isolation and spectroscopy at low temperatures in superacid media.4,5 However, obtaining an X-ray crystal structure of a protonated arene salt is an unrealized experimental challenge,5 and thermal instability has prevented their development as useful reagents. In this paper, we show how modern anions lead to readily crystallized salts of remarkable thermal stability. The salt of protonated benzene is a crystalline superacid with distinct advantages over existing superacid media.

    View record details
  • ??-Arene/Cation Structure and Bonding. Solvation versus Ligand Binding in Iron(III) Tetraphenylporphyrin Complexes of Benzene, Toluene, p-Xylene, and [60]Fullerene

    Evans, DR; Fackler, NLP; Xie, Z; Rickard, CEF; Boyd, PDW; Reed, CA (1999)

    Journal article
    The University of Auckland Library

    Benzene, toluene, p-xylene, and [60]fullerene are shown to be weak ligands to a hard metal such as iron(III) in Fe(TPP)+ cation (TPP = tetraphenylporphyrinate). X-ray crystal structures of [Fe(TPP)(C6H6)][CB11H6Br6]??3.5C6H6 (1), [Fe(TPP)(C7H8)][CB11H6Cl6]??2C7H8 (2), [Fe(TPP)(C8H10)][Ag(CB11H6Br6)2]??arene (3), and [Fe(TPP)(C60)][F20-BPh4]??2.5dichlorobenzene (4) show distinctively short Fe??????C contacts, in the range 2.65???2.95 ??, which distinguish ligation from ??????? cocrystallized solvation. Dihedral angles between the arene and metalloporphyrin planes are also diagnostic of ligand versus solvate roles. The essential features of the arene coordination can be faithfully reproduced using density functional theory. In contrast to alkali metal cation/??-arene interactions, a component of the covalent bonding can be recognized. In a broader context, this study suggests that solvents such as benzene should always be viewed as potential ligands in the presence of coordinatively unsaturated cations. The common use in supramolecular chemistry of the term ???noncovalent??? to describe entities with metal???ligand bonds is viewed as misleading.

    View record details
  • Selective supramolecular porphyrin/fullerene interactions

    Boyd, PDW; Hodgson, MC; Rickard, CEF; Oliver, AG; Chaker, L; Brothers, Penelope; Bolskar, RD; Tham, FS; Reed, CA (1999)

    Journal article
    The University of Auckland Library

    Naturally assembling cocrystallates of C60 and C70 fullerenes with tetraphenylporphyrins (H2TPP??C60??3 toluene, 1; H2T3,5-dibutylPP??C60, 2; H2T3,5-dimethylPP??1.5C60??2 toluene, 3; H2TpivPP??C60, 4; H2T3,5-dimethylPP??C70??4 toluene, 5; ZnTPP??C70, 6; NiT4-methylPP??2C70??2 toluene, 7) show unusually short porphyrin/fullerene contacts (2.7???3.0 ??) compared with typical ??????? interactions (3.0???3.5 ??). In the C60 structures, an electron-rich, 6:6 ring juncture, C???C bond lies over the center of the porphyrin ring. In the C70 structures, the ellipsoidal fullerene makes porphyrin contact at its equator rather than its poles; a carbon atom from three fused six-membered rings lies closest to the center of the porphyrin. These structures provide an explanation for the manner in which tetraphenylporphyrin-appended silica stationary phases effect the chromatographic separation of fullerenes. The interaction of the curved ?? surface of a fullerene with the planar ?? surface of a porphyrin, without the need for matching convex with concave surfaces, represents a new recognition element in supramolecular chemistry. NMR measurements show that this interaction persists in toluene solution, suggesting a simple way to assemble van der Waals complexes of donor???acceptor chromophores.

    View record details
  • Heptane coordination to an iron(II) porphyrin

    Evans, DR; Drovetskaya, T; Bau, R; Reed, CA; Boyd, PDW (1997)

    Journal article
    The University of Auckland Library

    One of the most interesting weak interactions of organotransition metal chemistry is the coordination of an alkane to a metal center. Formerly regarded as inert and non-nucleophilic, an sp3 saturated C-H bond is now recognized ...

    View record details
  • The [Cu8Br15](6-) ion, a crystal-stabilized high-symmetry mixed-valence copper complex with a linear halogen bridge

    Bowmaker, GA; Boyd, PDW; Rickard, CEF; Scudder, ML; Dance, IG (1999)

    Journal article
    The University of Auckland Library

    The [Cu8Br15]6- ion in green crystalline (MePh3P)6[Cu8Br15] is shown by X-ray crystallography to have the structure [Br3(??3-Br4Cu4)(??2-Br)(??3-Br4Cu4)Br3]6- derived from two Cu4Br8 cubane units. The unusual geometry and charge of the anion are determined by the high-symmetry (space group Pa3??) lattice of cations, maintained by phenyl??????phenyl interactions, and interacting with the anion by C???H??????Br hydrogen bonds.

    View record details
  • Supramolecular fullerene-porphyrin chemistry. Fullerene complexation by metalated "jaws porphyrin" hosts

    Sun, D; Tham, FS; Reed, CA; Chaker, L; Boyd, Peter (2002)

    Journal article
    The University of Auckland Library

    Porphyrins and fullerenes are spontaneously attracted to each other. This new supramolecular recognition element is explored in discrete, soluble, coordinatively linked porphyrin and metalloporphyrin climers, Jawlike clefts in these bis-porphyrins ar

    View record details
  • Establishing through-bond connectivity in solids with NMR: Structure and dynamics in HC60+

    Mueller, LJ; Elliott, DW; Kim, KC; Reed, CA; Boyd, Peter (2002)

    Journal article
    The University of Auckland Library

    We present a novel nuclear magnetic resonance experiment for establishing through-bond connectivity in solids using scalar coupling-driven correlation. This method, a variant of the popular double-quantum-filtered correlation spectroscopy experiment in liquids, is robust under fast magic-angle-spinning conditions and in the presence of dynamics. In HC60+, where anisotropic molecular motion renders through-space dipolar-driven correlation ineffective, this through-bond correlation method answers a significant structural question by accurately identifying the direct bond between the protonated sp3 hybridized carbon site and the sp2 hybridized cationic site.

    View record details
  • Trends within the adsorption energy of alcohols over rutile TiO2(110) and (011) clusters

    Kieu, L; Boyd, Peter; Idriss, H (2002)

    Journal article
    The University of Auckland Library

    The non-dissociative adsorption energy of a series of alcohols over a rutile Ti8O29H26 cluster, representing the TiO2(0 1 1) surface, as well as over a rutile Ti11O42H40 cluster, representing the TiO2(1 1 0) surface, was computed by means of a semi-e

    View record details
  • Molecular structure of the solvated proton in isolated salts. Short, strong, low barrier (SSLB) H-bonds

    Stasko, D; Hoffmann, SP; Kim, KC; Fackler, NLP; Larsen, AS; Drovetskaya, T; Tham, FS; Reed, CA; Rickard, Clifton; Boyd, Peter; Stoyanov, ES (2002)

    Journal article
    The University of Auckland Library

    Large, inert, weakly basic carborane anions of the icosahedral type CHB11R5X6- (R = H, Me; X = Cl, Br) allow ready isolation and structural characterization of discrete salts of the solvated proton, [H(solvent)x][CHB11R5X6], (solvent = common O-atom donor). These oxonium ion Br??nsted acids are convenient reagents for the tuned delivery of protons to organic solvents with a specified number of donor solvent molecules and with acidities leveled to those of the chosen donor solvent. They have greater thermal stability than the popular [H(OEt2)2][BArF] acids based on fluorinated tetraphenylborate counterions because carborane anions can sustain much higher levels of acidity. When organic O-atom donors such as diethyl ether, tetrahydrofuran, benzophenone, and nitrobenzene are involved, the coordination number of the proton (x) in [H(solvent)x]+ is two. A mixed species involving the [H(H2O)(diethyl ether)]+ ion has also been isolated. These solid-state structures provide expectations for the predominant molecular structures of solvated protons in solution and take into account that water is an inevitable impurity in organic solvents. The O??????O distances are all short, lying within the range from 2.35 to 2.48 ??. They are consistent with strong, linear O??????H??????O hydrogen bonding. Density functional theory calculations indicate that all H(solvent)2+ cations have low barriers to movement of the proton within an interval along the O??????H??????O trajectory, i.e., they are examples of so-called SSLB H-bonds (short, strong, low-barrier). Unusually broadened IR bands, diagnostic of SSLB H-bonds, are observed in these H(solvent)2+ cations.

    View record details
  • Water Localisation and reclamation: steps towards Low Impact Urban Design and Development

    van Roon, MR (2007)

    Journal article
    The University of Auckland Library

    Numerous drivers are providing stimulus for increased water cycle localisation within urban neighbourhoods. This paper uses predominantly Australasian case studies to highlight trends, successes and challenges in the transition to neighbourhood centred water-based services using ???Low Impact??? and ???Water Sensitive??? design and development techniques. Major steps towards urban sustainability are demonstrated, for example, up to 70% reduction in the demand for potable water (Aurora, Melbourne), removal of contaminated stormwater and sewage effluent discharge to natural waterways vulnerable to nutrient or toxin accumulation, and up to 55% of the area of the greenfield site planted in indigenous species (Regis Park, New Zealand). Reduced demand for potable water would enable continued undiluted use of ???pure??? water sources from limited bush catchments (Waitakere Ranges, New Zealand), and less dependence on rivers stressed by low flows. Reductions and dispersion of sewage effluent discharges protects receiving waters, such as Port Phillip Bay, Melbourne, from eutrophication. Reduced stormwater discharge favours retention of the natural hydrological regime of rivers and minimises bioaccumulation of toxins in aquatic ecosystems.

    View record details
  • Dicopper(II) and dinickel(II) complexes of Schiff-base macrocycles derived from 5,5-dimethyl-1,9-diformyldipyrromethane

    Li, RQ; Mulder, TA; Beckmann, U; Boyd, Peter; Brooker, S (2004)

    Journal article
    The University of Auckland Library

    The synthesis and characterisation of two dicopper(II) and two dinickel(II) macrocyclic complexes, [(Cu2LPr)-L-II] (10), [(Cu2LBu)-L-II] (11), [(Ni2LPr)-L-II] (12) and [(Ni2LBu)-L-II] (13), are reported. The two new Schiff-base macrocycles (L-Pr)(4-)

    View record details
  • Isolating Benzenium Ion Salts

    Reed, CA; Kim, KC; Stoyanov, ES; Stasko, D; Tham, FS; Mueller, LJ; Boyd, Peter (2003)

    Journal article
    The University of Auckland Library

    When partnered with carborane anions, arenium ions are remarkably stable. Previously investigated only at subambient temperatures in highly superacidic media, protonated benzene is readily isolated as a crystalline salt, thermally stable to >150 ??C. Salts of the type [H(arene)][carborane] have been prepared by protonating benzene, toluene, m-xylene, mesitylene, and hexamethylbenzene with the carborane superacid H(CB11HR5X6) (R = H, Me; X = Cl, Br). They have been characterized by elemental analysis, X-ray crystallography, NMR and IR methods. Solid-state 13C NMR spectra are similar to those observed earlier in solution, indicating that lattice interactions are comparable to solution solvation effects. The acidic proton(s) of the arenium cations interact weakly with the halide substituents of the anion via ion pairing. This is reflected in the dependence of the C???H stretching frequency on the basicity of the carborane anion. Bond lengths in the arenium ions are consistent with predominant cyclohexadienyl cation character, but charge distribution within the cation is less well represented by this resonance form. Structural and vibrational comparison to theory is made for the benzenium ion (C6H7+) with density functional theory at B3LYP/6-31G* and B3P86/6-311+G(d,p) levels. The stability of these salts elevates arenium ions from the status of transients (Wheland intermediates) to reagents. They have been used to bracket the solution-phase basicity of C60 between that of mesitylene and xylene.

    View record details
  • Spin states of C-60(3-) and C120On- (n=2, 3, 4) anions using electron spin transient nutation spectroscopy

    Drew, SC; Boas, JF; Pilbrow, JR; Boyd, Peter; Paul, P; Reed, CA (2003)

    Journal article
    The University of Auckland Library

    Electron spin transient nutation (ESTN) experiments show that the spin multiplicity of the ground state of C-60(3-) in frozen solution is a doublet with S = 1/2. In purified samples, there is no evidence for excited states or other species with highe

    View record details
  • Synthesis of the C59N+ Carbocation. A Monomeric Azafullerene Isoelectronic to C60

    Kim, KC; Hauke, F; Hirsch, A; Boyd, Peter; Carter, E; Armstrong, RS; Lay, P; Reed, CA (2003)

    Journal article
    The University of Auckland Library

    A heterofullerene isoelectronic to C60 is reported. The azafullerenium cation C59N+ can be isolated in good yield as a carborane salt via the two-electron oxidation of the C-C bond of (C59N)2 dimer. [C59N][Ag(CB11H6Cl6)2] has been characterized by electronic, IR, Raman, and 13C NMR spectroscopies, MALDI spectrometry, DFT calculations, and X-ray crystallography.

    View record details
  • Artifacts in the electron paramagnetic resonance spectra of C-60 fullerene ions: Inevitable C120O impurity

    Paul, P; Kim, KC; Sun, D; Boyd, Peter; Reed, CA (2002)

    Journal article
    The University of Auckland Library

    Aspects of the electron paramagnetic resonance (EPR) spectra Of C-60(n) fulleride ions (n = 2, 3) and the EPR signal observed in solid C-60 are reinterpreted, Insufficient levels of reduction and the unrecognized presence Of C120O, a ubiquitous and u

    View record details
  • Pentane-2,4-dionebis(diphenylphosphino)alkane Complexes of Nickel(II).

    Boyd, PDW; Rickard, CEF; Cavell, KJ (2000)

    Journal article
    The University of Auckland Library

    ACTA CRYST. C56, e16-e18 (2000). P.D.W. Boyd, C.E.F. Rickard and K.J. Cavell

    View record details
  • Porphyrin-fullerene host-guest chemistry

    sun, D; Tham, FS; Reed, CA; Chaker, L; Burgess, M; Boyd, Peter (2000)

    Journal article
    The University of Auckland Library

    Fullerenes are spontaneously attracted to porphyrins and metalloporphyrins. This new supramolecular recognition element was first discovered in cocrystallates of C60 and C70 with tetraarylporphyrins and octaethylmetalloporphyrins. ...

    View record details