bluuebunny/crossref_metadata_2025 huggingface dataset:
Determining reference conditions for management and restoration of temperate grassy woodlands: relationships among trees, topsoils and understorey flora in little-grazed remnants
Authors: Prober Suzanne M. , Lunt Ian D. , Thiele Kevin R.
Published: March 2003

Temperate grassy woodlands were once widespread and dominant in many agricultural regions of south-eastern Australia. Most are now highly degraded and fragmented and exist within a context of broadscale landscape degradation. Greater understanding of natural processes in these woodlands is needed to benchmark management and restoration efforts that are now critical for their ongoing survival. We studied physical and chemical properties of topsoils from rare, little-grazed remnants of grassy Eucalyptus albens Benth. and E. melliodora Cunn. ex Schauer woodlands in central New South Wales and examined natural patterns in topsoil properties and understorey flora in relation to trees and canopy gaps. Topsoils were generally low in available macronutrients (nitrogen, phosphorus and sulfur), but were favourable for plant growth in most other measured characteristics. Topsoils beneath trees were notably more fertile than in open areas, particularly in total carbon, total nitrogen, available phosphorus, available potassium and salinity. Higher nutrient concentrations, particularly of available phosphorus, may have contributed to patterns in understorey dominants, with Themeda australis (R.Br.) Stapf predominating in open areas and Poa sieberiana Spreng. beneath trees. Trees were also associated with a higher native-plant richness, possibly resulting from their influence on the competitive dynamics of the dominant grasses. We discuss the implications of these interactions for the use of burning, grazing and slashing in woodland management and re-establishment of native grasses and trees in restoration efforts.
An investigation into the possible inhibitory effects of white cypress pine (Callitris glaucophylla) litter on the germination and growth of associated ground cover species
Authors: Harris Mark R. , Lamb David , Erskine Peter D.
Published: March 2003

White cypress-pine stands typically support sparse densities of shrubs and grasses. The commonly held opinion is that leaching of allelopathic chemical compounds from cypress-pine litter partly facilitates this exclusion. Germination and growth of cypress pine seedlings do not appear to be similarly affected. This study set out to determine whether cypress litter had a differential effect on germination and growth of cypress-pine seedlings and on associated ground-cover species. Glasshouse trials comparing seedling emergence under cypress- and artificial-litter layers were undertaken. Cypress-pine litter did not have an inhibitory effect on the germination or growth of ground-cover species. In most cases, seedling emergence was facilitated by the application of cypress-pine litter due to its ability to increase the water holding capacity of the underlying soil. Cypress litter did not promote growth of its own seedlings over its competitors except on coarse-textured soils where it provided an ameliorative function to water stress due to the soil's reduced water holding capacity. The inhibition of ground-cover species' germination and growth in pure cypress stands was suggested to be the result of high below-ground resource competition due to the pine's expansive root morphology.
Collenchyma in Panicum maximum (Poaceae): localisation and possible role
Authors: Paiva Elder A. S. , Machado Sílvia R.
Published: March 2003

This work relates the occurrence and distribution of collenchyma in Panicum maximum Jacq. P.�maximum leaves were collected at different phases of development and sampled from both the base of the sheath and from the sheath–leaf blade transition area. For the stems, the study was made by using hand-cut sections of the internodal base. In the leaves, analyses of serial sections showed, at the base and sheath–leaf blade transition area, a sudden change of tissue at vascular bundle. The vascular bundles are surrounded by sclerenchyma, both in the sheath and the leaf blade, as well as by fibrous threads that occur on the adaxial side of the central bundles. However, at the base of the sheath and at the sheath–leaf blade transition area, sclerenchyma was substituted for collenchyma. In the stem, the substitution of sclerenchyma associated with vascular bundles for collenchyma occurs at the base of the internode, in the pulvinus region. The analyses from transmission electron microscopy showed the presence of lamellated cell wall and active protoplast in collenchyma cells.
Genetic control of coppice and lignotuber development in Eucalyptus globulus
Authors: Whittock S. P. , Apiolaza L. A. , Kelly C. M. , Potts B. M.
Published: March 2003

The economics of short-rotation pulpwood plantations of Eucalyptus globulus as a coppice crop are influenced by stump survival and subsequent coppice growth rates. This study revealed significant genetic diversity in coppicing traits, both within and between subraces, following felling in a progeny trial after 9 years of growth. A total of 67% of trees coppiced after 14 months, but subraces varied from 43 to 73%. Heritabilities for coppice success (0.07) and subsequent growth (0.16–0.17) were low but statistically significant. Strong genetic correlation between presence/absence of coppice, the number of stems coppicing from the stump and modal coppice height, indicate that selection is possible by using the binary trait. The ability of a tree to coppice was genetically correlated with tree growth prior to felling (rg = 0.61) and with nursery-grown seedling traits, where large genetic differences were observed in the development of lignotubers. Coppicing was genetically correlated with the number of nodes with lignotubers (rg = 0.66) and seedling stem diameter at the cotyledonary node (rg = 0.91). These traits were uncorrelated with later age growth and with each other. The results suggest that coppicing is influenced by three independent mechanisms—lignotuber development, enlargement of the seedling stem at the cotyledonary node and vigorous growth—which enhance ability to survive catastrophic damage, and indicate that both lignotuber and coppice development can be altered by both natural and artificial selection.
Identifying ecological barriers to restoration in temperate grassy woodlands: soil changes associated with different degradation states
Authors: Prober Suzanne M. , Thiele Kevin R. , Lunt Ian D.
Published: March 2003

Temperate grassy woodlands were once the dominant vegetation across many agricultural regions of south-eastern Australia, but most of these are now highly degraded and fragmented. Adequate conservation of these woodlands is dependent on successful ecological restoration; however, ecological barriers often limit ecosystem recovery once degrading processes are removed. To help identify these barriers, we used a state and transition framework to compare topsoils of little-disturbed (reference) and variously degraded remnants of grassy Eucalyptus albens Benth. and E. melliodora Cunn. ex Schauer woodlands. Topsoils of degraded remnants showed a repeated pattern, with the most compacted, most acidic and most depleted topsoils occurring in remnants dominated by Aristida ramosa R.Br. or Austrodanthonia H.P.Linder and Austrostipa scabra (Lindl.) S.W.L.Jacobs & J.Everett; the least compacted and most nutrient rich topsoils in remnants dominated by annual exotics; and generally intermediate topsoils in remnants dominated by Bothriochloa macra (Steud.) S.T.Blake or Austrostipa bigeniculata (Hughes) S.W.L.Jacobs & J.Everett. Surprisingly, topsoils beneath trees in reference sites (supporting Poa sieberiana Spreng.) were similar to topsoils supporting annual exotics for most soil properties. Chemical properties of topsoils from open areas of reference sites [supporting Themeda australis (R.Br.) Stapf] were usually intermediate and similar to Bothriochloa macra and Austrostipa bigeniculata topsoils. The most striking exception to these trends was for soil nitrate, which was extremely low in all reference topsoils and showed a high correlation with annual exotic abundance. We discuss the potential for positive feedbacks between soil nitrogen cycling and understorey composition and the need for intervention to assist possible nitrate-dependent transitions between annual and perennial understorey states. Dominant grasses, trees and annual weed abundance may be useful indicators of soil conditions and could inform selection of target sites, species and techniques for restoration projects.
Self-compatibility and floral biology in subdioecious Wurmbea dioica (Colchicaceae)
Authors: Vaughton Glenda , Ramsey Mike
Published: March 2003

Dioecy has long been interpreted as a mechanism to avoid self-fertilisation and the negative effects of inbreeding depression. We determined relative self-compatibility and temporal overlap of male and female functions for hermaphrodites in subdioecious Wurmbea dioica to assess the role of selfing in the maintenance of gender dimorphism. Plants were self-compatible but did not self-pollinate autonomously. Self- and open-pollinated hermaphrodites had high seed abortion and low seed set, whereas crossed hermaphrodites and crossed and open females had low seed abortion and high seed set. For selfed hermaphrodites, abortion occurred over a range of developmental stages and was negatively related to seed set. Inbreeding depression for seed set varied extensively among plants, averaging 0.56. Despite high inbreeding depression, substantial selfing occurred in open-pollinated hermaphrodites (S = 0.76), as estimated by a non-genetic method. Flowers were protogynous, although temporal separation of male and females functions was limited because anthers began to dehisce shortly after flowers opened. Anther dehiscence was staggered over 4 days and floral longevity, pollen longevity and stigma receptivity were prolonged, thus providing considerable opportunities for pollinator-mediated self-pollination. Our findings indicate that high levels of selfing and subsequent abortion of selfed embryos due to early acting inbreeding depression are important factors maintaining gender dimorphism in W. dioica.
The potential contribution of biomechanical properties to anti-herbivore defence in seedlings of six Australian rainforest trees
Authors: Iddles Tracey L. , Read Jennifer , Sanson Gordon D.
Published: March 2003

Biomechanical properties of leaves, such as strength and toughness, may contribute to anti-herbivore defence by making it physically difficult or energetically costly for animals to eat them. We investigated leaf strength and toughness in seedlings of six rainforest trees from eastern Australia and their potential contribution to defence. Strength and toughness (work to fracture) were measured at the scale of the whole leaf and of different leaf parts. Resources for herbivores (water and nitrogen) and potential chemical defences (phenolics, alkaloids and cyanogenic glycosides) were also investigated.Leaves of Nothofagus moorei (F.Muell.) Krasser, Ceratopetalum apetalum D.Don and Doryphora sassafras Endl. were generally the toughest and strongest of those studied. Toona ciliata M.Roemer showed high concentrations of nutritive resources and little investment in the defences investigated, consistent with its shorter leaf lifespan and higher growth rate. There were no significant correlations of mechanical properties with palatability, but the softest leaf (T. ciliata) was associated with high levels of leaf damage in bioassay trials. There was also evidence that some leaves that are well-defended mechanically (involving carbon-rich cell wall) may invest less in competing carbon-based chemical defences, such as phenolics.
Geographic gradients in seed size among and within perennial Australian Glycine species
Authors: Murray Brad R. , Brown A. H. D. , Grace J. P.
Published: March 2003

In the Northern Hemisphere, a latitudinal gradient of increasing seed size towards the equator has been well documented. Because of a paucity of studies from the Southern Hemisphere, however, the global generality of this latitudinal gradient in seed size is unknown. This study investigated variation in seed size in relation to latitude among and within perennial Glycine species across Australia. Seed size was estimated from over 1500 provenances covering the latitudinal, longitudinal and altitudinal extents of 37 taxa within the subgenus. In order to ensure that any observed latitudinal gradient in seed size existed independently of two other major geographic variables, longitude and altitude, we controlled for their influence via the use of general linear models. Among species, a significant negative relationship emerged between seed size and latitude when latitude was considered on its own and after accounting for the influence of longitude and altitude in models. For Australian populations of the subgenus Glycine, mean species seed size increased by 4.23% with each shift of one degree of latitude towards the equator and increased significantly along an east–west cline across the continent, by 2.25% with each degree of longitude. This latter relationship was obtained both when longitude was considered on its own and after controlling for the influence of latitude and altitude in models. Patterns of seed size variation with latitude and longitude within species mirrored patterns among species, although there were some notable exceptions. Altitude was significantly related to seed size among species only after removing the linear effects of latitude and longitude, when the trend was for lowland species to have smaller seeds. In contrast to the interspecific pattern, some intraspecific negative trends were found within G. canescens and G. cyrtoloba, which accords with Baker's hypothesis for an inverse relation between seed size and altitude. We discuss the relationships between seed size and the three geographic variables in the subgenus Glycine, with respect to environmental factors that could account for the trends detected.
A Preparative and Preliminary Spectroscopic Study of Analogues of a Zinquin-Related Fluorophore
Authors: Kimber Marc C. , Geue Jason P. , Lincoln Stephen F. , Ward A. David , Tiekink Edward R. T.
Published: March 2003

The syntheses of the 4- and 5-methoxy isomers of 4-N-(6-methoxy-2-methyl-8-quinolyl)-4-methylbenzenesulfon-amide and of N-(2-methoxy-8-quinolyl)-4-methylbenzenesulfonamide are described. The 6-methoxy compound is a precursor of Zinquin ester, a specific fluorophore for Zn(II). The 2-methoxy analogue was synthesized by nitration of 2-chloroquinoline and subsequent functional group manipulation. The 4-methoxy isomer was synthesized from a 4-quinolone derivative, and the 5-methoxy isomer was synthesized by a standard Skraup quinoline synthesis. The structures of the 4- and 5-methoxy isomers were determined by single-crystal X-ray analysis. All of these compounds showed a bathochromic shift in their ultraviolet/visible spectra upon addition of Zn(II) to the solution. These compounds are all weakly or non-fluorescent in solution. All form fluorescent complexes with Zn(II) except the 5-methoxy compound. The 4-methoxy compound forms a significantly more fluorescent complex than those of the 6-methoxy compound and Zinquin ester and has a higher quantum yield than the others.
Langmuir Aggregation of Eosin-Y in Protein and its Application
Authors: Gao Hong-Wen , Zhao Jian-Fu
Published: March 2003

The microsurface adsorption–spectral correction (MSASC) technique is described and applied to the investigation of the interaction of eosin-Y (EOY) with proteins at pH 3.8. The microelectrostatic fields in proteins cause the aggregation of EOY and it obeys Langmuir isothermal adsorption. Results have shown that the binding ratio of EOY to bovine serum albumin (BSA), ovalbumin (OVA), concanavalin A (ConA), and human γ-globulin (γ-G) are 77 : 1, 23 : 1, 4 : 1, and 83 : 1, the adsorption constants of the complexes were calculated to be 2.82×106, 1.70×105, 1.80×105, and 2.49×104 M–1, and their molar absorptivities 3.20×106, 1.21×106, 1.35×105, and 5.27×106 L mol–1 cm–1 at 540�nm. The adsorption reaction has been applied to the quantitative detection of proteins in samples with satisfactory results.
Synthesis, Characterization, and Modelling of Novel Multifunctional Acryloyl-Based Monomers: An Experimental and Computational Study
Authors: Patras Georgia , Qiao Greg G. , Solomon David H. , Koch Rainer
Published: March 2003

Several novel multifunctional monomers with at least three reactive N-acryloyl double bonds have been synthesized and fully characterized. Quantum-chemical calculations and nuclear magnetic resonance (NMR) spectroscopy have been used to predict the structural dissymmetry of these monomers: the simulation of conformers and the NMR spectrum of monomer (3) allows the explanation of the observed 13C NMR spectra as well as a comparison of the performance of several methods for calculating chemical shifts.
Solvothermal Syntheses and Characterizations of Two Isomorphous One-Dimensional Chain Complexes Constructed by Orotic Acid
Authors: Sun D. , Cao R. , Liang Y. , Hong M. , Zhao Y. , Weng J.
Published: March 2003

Solvothermal reactions of M(OAc)2 (M = Ni, Co) with orotic acid (2,6-dioxo-1,2,3,6-tetrahydropyrimidine-4-carboxylic acid, H3L) in H2O/MeOH (1 : 1) gave rise to two new isomorphous polymeric complexes, [M(HL)(H2O)3]n [M = Ni, (4); Co, (5)], with one-dimensional chain structures. Both complexes crystallize in the orthorhombic space group P212121, with a 7.7438(7), b 7.7610(7), c 14.6528(12) �, Z 4 for (4), and a 7.7005(3), b 7.8725(3), c 14.6997(10) �, Z 4 for (5). X-Ray diffraction analysis shows that the metal ion is coordinated by nitrogen and oxygen atoms of an orotate ligand (HL2–) and water molecules in a distorted octahedral geometry. The hydrogen-bond interactions between chains leads to the formation of three-dimensional network structures.
Effect of Cr Addition on the Methane Aromatization Performance of the Mo/HZSM-5 Catalyst
Authors: Zhang Y. , Wang D. , Fei J. , Zheng X.
Published: March 2003

The promotional effect of Cr addition on the methane aromatization performance of the Mo/HZSM-5 catalyst was investigated. It was found that much higher methane conversion was obtained over Mo–Cr/HZSM-5 catalyst than over Mo/HZSM-5. The results indicate that when the Cr/Mo molar ratio is 0.07, the methane conversion and aromatics selectivity reach 11.6 and 97.3% respectively at a reaction temperature of 973 K. Raising the temperature is beneficial to the methane conversion and 15.82% conversion is obtained at 1023 K. Modern measurements such as isopropyl alcohol decomposition and temperature desorption of ammonia (NH3-TPD) were used to characterized the catalysts. The results of isopropyl alcohol decomposition show that the surface acidity of Mo–Cr/HZSM-5 is increased at high temperature. The NH3-TPD findings imply that the Mo–Cr/HZSM-5 catalyst has much stronger acidity and more acid sites than Mo/HZSM-5, most likely one of the reasons for the enhanced activity for methane aromatization using Mo–Cr/HZSM-5 catalyst.
Structural Studies of N-Acyl 1,1′-Bis(1,2,3,4-tetrahydroisoquinoline) Derivatives
Authors: Craig Donald C. , Judeh Zaher M. A. , Read Roger W.
Published: March 2003

The X-ray crystal structures of N-acyl substituted 1,1′-bis(1,2,3,4-tetrahydroisoquinolines) are disclosed for the first time and evidence is provided that the molecules reside in single preferred conformations in solution and solid states, with axial bonds bridging C1–C1′ that have no steric impediment to rotational freedom.
Water-Binding and Oxygen Permeability in Poly(vinyl alcohol) Films
Authors: Lien L. , Fellows C. M. , Copeland L. , Hawkett B. S. , Gilbert R. G.
Published: March 2003

The measurement and interpretation of isotherms for sorption of water onto, and oxygen permeability of, polymer substrates are important for designing polymers in applications such as agricultural seed coatings. In a preliminary study of water sorption in the commonly used copolymer poly(vinyl alcohol–co-vinyl acetate), moisture sorption isotherms were measured for a series of substrates of different comonomer composition at 25°C. The data were fitted to the D'Arcy–Watt model, which gave physically reasonable values for parameters related to the strength of monolayer adsorption to high affinity sites on the substrate and the number of sites for secondary water adsorption per unit mass. The oxygen permeability of poly(vinyl alcohol) films was found to be a function only of the water content of the films, with no other obvious contributing factors. Marked differences were seen in the populations of 'bound' and 'unbound' water characterized by 1H nuclear magnetic resonance (NMR) spectroscopy and moisture sorption isotherm fitting. There was no correlation of oxygen permeability with 'bound' or 'unbound' water measured by any means, a fact suggesting that there is a continuum of water environments within the materials.
The Synthesis and Crystal Structures of Two Cobalt(III) Complexes Containing the Ligand 1,4,8,11-Tetraazacyclotetradecane
Authors: Funston A. M. , McFadyen W. D. , Tregloan P. A.
Published: March 2003

The new cobalt(III) complex [Co(cyclam)(NO3)2]NO3�HNO3 (2) has been synthesized. The crystal structure of this complex and the related complex [Co(cyclam)(NH3)2]Cl2BF4�2H2O (1) have been determined. Crystal data for (1): M 451.04, monoclinic, space group P21/c (No. 14), a 7.3927(10), b 13.3082(7), c 19.524(2) Å, β 97.625(14)�, V 1903.9(3) Å3, F(000) 936, Z 4, Dc 1.574 g cm–3, μ 1.225 cm–1, Mo Kα (graphite monochromatized) λ 0.71073 Å, T 293(1) K. Crystal data for (2): M 571.33, triclinic, space group P1–(No. 2),a 7.3988(14), b 8.5682(16), c�9.209(3) Å, α 89.02(2), β 76.64(3), γ 82.340(16)�, V 562.9(2) Å3, F(000) 296, Z 1, Dc 1.685 g cm–3, μ 0.854 cm–1, Mo Kα (graphite monochromatized) λ 0.71073 Å, T 293(1) K. In both complexes the complex crystallizes in the trans-III form with the cobalt in the usual octahedral environment.
High-Temperature Structural Studies of SrPbO3 and BaPbO3
Authors: Hester J. R. , Howard C. J. , Kennedy B. J. , Macquart R.
Published: March 2003

High-resolution X-ray powder diffraction studies have shown BaPbO3 to transform from an orthorhombic Imma structure at room temperature, through an intermediate I4/mcm phase, to a cubic Pm3–mstructure above 500�C. The Imma to I4/mcm transition is first order and the I4/mcm–Pm3–m transition for BaPbO3 is tricritical in nature. We find no evidence for any phase transitions in SrPbO3 up to 760�C, the structure remaining in Pnma from room temperature to 760�C.
Synthesis and Crystal Structure of [(CH2)6N4CH3]2[CoCl4]
Authors: Li W. , Zheng S.-L. , Zhu C.-R. , Tong Y.-X. , Chen X.-M.
Published: March 2003

The interesting three-dimensional hydrogen-bonded self-assembled network of [(CH2)6N4CH3]+ cations and [CoCl4]2– anions has been prepared and structurally characterized. In the title complex, the quaternization of one hexamethylenetetramine nitrogen atom has been trapped, and further stabilized by the large [CoCl4]2– anions, featuring C–H���Cl hydrogen bonds (3.497–3.709 �) between the methylene groups of [(CH2)6N4CH3]+ cations and the chlorine atoms of the [CoCl4]2– anions.
2-Cyclopropylglycinatobis(2,2´-bipyridyl)cobalt(III) Diperchlorate and its Dihydrate
Authors: Richardson C. , Telfer S. G. , Hartshorn R. M.
Published: March 2003

The crystal structures of 2-cyclopropylglycinatobis(2,2�-bipyridyl)cobalt(III) diperchlorate, [Co(cpg)(2,2�- bpy)2](ClO4)2 (1), and its dihydrate [Co(cpg)(2,2�-bpy)2](ClO4)2�2H2O (2), are the first reported structures of a metal complex of 2-cyclopropylglycinate. Mixtures of the two kinds of crystals are formed from solutions that contain an excess of the Δ-R/Λ-S diastereoisomer. This diastereoisomer predominates in the solid state, but small amounts of the Δ-S/Λ-R diastereoisomer are also present, creating a disordered structure. Modelling the disorder to fit the diffraction data gives a diastereoisomeric composition of the crystals that is consistent with the nuclear magnetic resonance data.
Homogeneous Controlled Free Radical Polymerization in Aqueous Media
Authors: Lowe A. B. , McCormick C. L.
Published: March 2003

The ability to conduct controlled radical polymerizations (CRP) in homogeneous aqueous media is discussed. Three main techniques, namely stable free radical polymerization (SFRP), with an emphasis on nitroxide-mediated polymerization (NMP), atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer polymerization (RAFT) are examined. No examples exist of homogeneous aqueous NMP polymerization, but mixed water/solvent systems are discussed with specific reference to the NMP of sodium 4-styrenesulfonate. Aqueous ATRP is possible, although monomer choice is limited to methacrylates and certain styrenics. Finally, homogeneous aqueous RAFT polymerizations are examined. We demonstrate the greater versatility of this technique, at least in terms of monomer variety, by discussing the controlled polymerization of charged and neutral acrylamido monomers and of a series of ionic styrenic monomers. Many of these monomers cannot/have not been polymerized by either NMP or ATRP.
The Effect of Solvent on Isomer Formation. Synthesis and Crystal Structures of CdII Complexes with 3-Nitrobenzoate and Thiourea
Authors: Zheng S.-L. , Li W. , Yang G. , Chen X.-M. , Zhu H.-G. , Ye B.-H.
Published: March 2003

Two crystal forms of bis(3-nitrobenzoato)bis(thiourea)cadmium(II) were obtained by the reaction of Cd(NO3)2�4H2O, 3-nitrobenzoate (mNA) and thiourea (TU) from ethanol and water solutions, respectively. One is cube-shaped and crystallizes in the orthorhombic space group Pbca and consists of discrete mononuclear molecules of bis(3-nitrobenzoato-O,O�)bis(thiourea)cadmium(II) (1). The other form is needle shaped and crystallizes in the triclinic space group P1–.It is comprised of discrete molecules of bis(3-nitrobenzoato-O,O�)bis(thiourea)cadmium(II) (2) and (3-nitrobenzoato-O,O�)(3-nitrobenzoato-O)bis(thiourea)cadmium(II) (3). (1), (2) and (3) are isomers, in which (1) may be regarded as a structural intermediate between (2) and (3) in the 'carboxylate shift' process. The formation of these isomers may be influenced by the solvent effect.
Chelating and Bridging Modes of Coordination by 1,3-Bis(pyrazol-1-yl)propane; Coexistence of Discrete and Polymeric Metallosupramolecular Isomers within the Same Crystal
Authors: McMorran D. A. , Pfadenhauer S. , Steel P. J.
Published: March 2003

1,3-Bis(pyrazol-1-yl)propane (1) reacts with zinc acetate and cadmium nitrate to give tetrahedral [Zn(1)(OAc)2] and eight-coordinate [Cd(1)2(NO3)2] mononuclear complexes (2) and (3), respectively. Reaction with silver nitrate results in the formation of an intriguing complex (4) that consists of discrete M2L2 binuclear units stacked between [ML]n polymeric chains.
An Investigation into Alkenyl-Functionalized 1,4,7-Triazacyclononanes: Synthesis, Metal Complexation, and Attempted Olefin Metathesis
Authors: Baker M. V. , Brown D. H. , Skelton B. W. , White A. H.
Published: March 2003

Two triazacyclononanes bearing pendant alkenyl groups [1,4,7-tri(3-butenyl)-1,4,7-triazacyclononane and 1,4,7-tri(2-propenyl)-1,4,7-triazacyclononane] were synthesized. These triazacyclononanes reacted with nickel salts to form dinuclear complexes [(R3TACN)Ni(μ-Cl)3Ni(R3TACN)]+, various salts of which have been structurally characterized. Attempts to perform intramolecular olefin metathesis reactions on the pendant alkenes in these complexes were unsuccessful.
Subvirensic Acid, a New Depsidone from the Lichen Flavoparmelia haysomii
Authors: Elix J. A. , Xing-Wang L. , Wardlaw J. H.
Published: March 2003

The new depsidone subvirensic acid (4-formyl-3,8-dihydroxy-1,6-dimethyl-11-oxo-11H-dibenzo[b,e][1,4]di-oxepin-7-carboxylic acid) (7) has been isolated from the lichen Flavoparmelia haysomii and the structure deduced from a combination of spectroscopic data.
A Comparison of the Antimicrobial Skin Peptides of the New Guinea Tree Frog (Litoria genimaculata) and the Fringed Tree Frog (Litoria eucnemis)
Authors: Brinkworth C. S. , Bowie J. H. , Tyler M. J. , Wallace J. C.
Published: March 2003

The Fringed Tree Frog (Litoria eucnemis) is closely related to the Tree Frog Litoria genimaculata. Both species are found in northern Australia and New Guinea. We have reported that the major antibiotic peptide of L. genimaculata is maculatin 1.1 which has the sequence GLFGVLAKVAAHVVPAIEHF-NH2, and that this basic peptide is different from the hinged caerin 1 peptides (e.g. caerin 1.1, from Litoria splendida and other green tree frogs, which has the sequence GLLSVLGSVAKHVLPHVVPVIAEHL-NH2), in that it lacks four residues of the central hinge region of a caerin 1. Litoria eucnemis has three major host defence peptides, two of these are maculatins (e.g. maculatin 1.3; GLLGLLGSVVSHVVPAIVGHF-NH2) which are related in sequence to that of maculatin 1. The other antibiotic peptide is caerin 1.11 (GLLGAMFKVASKVLPHVVPAITEHF-NH2) a peptide related to the caerin 1 peptides of the green tree frogs of Australia. L. eucnemis is the only species of the Litoria genus (that we have studied) which contains both maculatin and caerin peptides in its skin secretion. The three antibiotic peptides of Litoria eucnemis are significantly less active than maculatin 1.1 and other caerins 1 isolated from anurans of the genus Litoria so far studied.
RAFT in Emulsion Polymerization: What Makes it Different?
Authors: Prescott S. W. , Ballard M. J. , Rizzardo E. , Gilbert R. G.
Published: March 2003

Reversible addition-fragmentation chain transfer (RAFT) polymerization techniques have been the focus of a great deal of recent work, particularly in their application to emulsion polymerization, which is the method of choice for implementing most free-radical polymerizations on an industrial scale. RAFT/emulsion polymerizations have considerable technical potential: to 'tailor-make' material properties, to eliminate added surfactant from surface coatings, and so on. However, considerable difficulties have been experienced in using RAFT in emulsion polymerization systems. Here, progress in the application of RAFT techniques to emulsion polymerization is reviewed, summarizing the difficulties that have been experienced and mechanisms that have been postulated to explain the observed behaviour. Possible origins of the difficulties in implementing RAFT in emulsion polymerizations include polymerization in droplets, water sensitivity of some RAFT agents, slow transport of highly hydrophobic RAFT agents across the water phase, and surface activity of some RAFT agents.
Termination Kinetics of Free-Radical Methyl Methacrylate - Dodecyl Acrylate and Dodecyl Methacrylate - Methyl Acrylate Copolymerizations
Authors: Buback M. , Feldermann A.
Published: March 2003

Copolymerization termination rate coefficients (kt) of the methyl methacrylate–dodecyl acrylate (MMA–DA) and dodecyl methacrylate–methyl acrylate (DMA–MA) systems at 40°C and 1000 bar have been measured using the single pulse (SP)–pulsed laser polymerization (PLP) technique. Plateau regions of kt are observed in the initial polymerization period. The region of constant kt increases with the size of the alkyl ester group, e.g. it extends up to at least 60% monomer conversion in DA and DMA homopolymerizations. The plateau kt values of MA and MMA are significantly above the corresponding DA and DMA values. The kt penultimate unit effect model, which uses the so-called geometric mean approximation, is well suited for representation of the dependence on monomer composition of the plateau kt values. The dependence of kt on monomer composition is quite different at low and at high degrees of monomer conversion. The reason behind this is seen in different types of diffusion control being operative at low and at high degrees of monomer conversion. The plateau-type behaviour is assigned to segmental diffusion control, whereas high-conversion kt is controlled by reaction diffusion.
High Pressure 'Living' Free-Radical Polymerization of Styrene in the Presence of RAFT
Authors: Monteiro M. J. , Bussels R. , Beuermann S. , Buback M.
Published: March 2003

Reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene was studied at high pressure, employing two dithioester RAFT agents with an isopropylcyano (5) and a cumyl (6) leaving group, respectively. The high-pressure reaction resulted in low polydispersity polymer. It was found that controlled polymerizations can be performed at increased pressures with a high degree of monomer conversion, which signifies that high-pressure polymerizations can be utilized for the production of higher molecular weight polystyrene of controlled microstructure. Retardation of styrene polymerization was also observed at high pressure in the presence of RAFT agents (5) and (6). It is postulated that the retarding potential of these two RAFT agents is associated with an intermediate radical termination mechanism. High-pressure free-radical polymerizations open the way to producing living polymers with high rates, and thus lower impurities such as 'dead' polymer that are formed through bimolecular termination reactions.
Infrared Spectra of Phthalocyanine and Naphthalocyanine in Sandwich-Type (Na)phthalocyaninato and Porphyrinato Rare-Earth Complexes. II. The Effects of Rare-Earth Ionic Size on the IR Characteristics of Naphthalocyaninein Bis(naphthalocyaninato) Rare-Earth Complexes
Authors: Sun X. , Bao M. , Pan N. , Cui X. , Arnold D. P. , Jiang J.
Published: March 2003

The infra-red (IR) spectroscopic data for a series of 28 homoleptic substituted bis(naphthalocyaninato) rare-earth complexes M(2,3-Nc*)2 [M = Y, La–Lu except Pm; H2Nc* = 3(4),12(13),21(22),30(31)-tetra(tert-butyl)-2,3- naphthalocyanine (H2TBNc) and 3,4,12,13,21,22,30,31-octa(dodecylthio)-2,3-naphthalocyanine (H2ODTNc)] have been collected with a resolution of 2 cm–1. These neutral sandwich complexes are radicals due to their composition (Nc*)2–MIII(Nc*)–, wherein the unpaired electron is delocalized over both macrocycles on the vibrational time scale. Compared to spectra obtained with low resolution, such as 4 cm–1, a larger number of vibrational modes could be distinguished. The IR spectra for M(ODTNc)2 are much simpler than those of M(TBNc)2, revealing the relatively higher symmetry of the former molecules. By analogy with bis(phthalocyaninato) rare-earth counterparts, the pyrrole stretching absorptions at 1314–1317 and 1323–1330�cm–1 for M(TBNc)2 and at 1316–1327 cm–1 for M(ODTNc)2 are assigned to the IR marker bands of the respective naphthalocyanine mono-anion radicals. These marker bands, together with those at 746–753 cm–1 assigned to C–H wagging, 1350–1355 cm–1 attributed to pyrrole stretchings, and 1389–1394 cm–1 due to naphthalene stretchings, have been found to shift slightly to higher energy along with the rare-earth contraction, clearly demonstrating the effect of rare-earth ionic radius.
Structural Characterization and CO Oxidation Activity of Nanostructured LaMnO3 Catalysts
Authors: Chen Min , Huang Huai-Qing , Zheng Xiao-Ming , Morris Michael A.
Published: March 2003

Perovskite-type LaMnO3 catalysts were prepared by three different methods and tested for CO oxidation. The structural character of the catalysts was investigated by using powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). All three different preparation methods resulted in nanostructured particles forming in the LaMnO3 catalysts. The crystallite size was in the range of 20 to 80 nm depending on the synthesis conditions. It was possible to synthesize the smallest particle size and a pure phase of perovskite-type LaMnO3 oxide by using a sol–gel method. The results also indicated that the CO total oxidation activity was related to the size of LaMnO3 particle and the structure formed.
Lewis-Base Adducts of Lead(II) Compounds. XXI. Revisitations: Synthesis and Structure of the Hydrated 1 : 2 Adduct of Lead(II) Bis(perchlorate) and 2,4,6-Tris(2-pyridyl)-1,3,5-triazine and a Low-Temperature Redetermination of the Structure of Bis(2-aminLewis-Base Adducts of Lead(II) Compounds
Authors: Harrowfield J. M. , Miyamae H. , Skelton B. W. , Soudi A. A. , White A. H.
Published: March 2003

Lead(II) perchlorate crystallizes from aqueous ethanol with 2,4,6-tris(2-pyridyl)-1,3,5-triazine (trz) as a 1 : 2 trihydrate adduct, [(trz)2Pb(OH2)(O2ClO2)](ClO4)�2H2O, as has been confirmed by a low temperature (ca .153 K) single crystal X-ray structure determination. The lead(II) environment is derivative of that of the previously recorded hydrated (rather than the methanol solvated) nitrate complex, comprising a pair of tridentate trz ligands, and, in place of the pair of bidentate nitrates, a unidentate water and an unsymmetrically bidentate perchlorate ion. A redetermination of the structure of bis(2-aminomethylpyridine)lead(II) bis(perchlorate) has resulted in a non-disordered model, still based upon the [Pb(amp)2(OClO3)2] entity, where amp = 2-aminomethylpyridine, but with eight independent molecules, devoid of any crystallographic symmetry, comprising the asymmetric unit of the structure, which is described in a larger unit cell of lower symmetry.
Morphologically Controlled Proton-Conducting Membranes Using Graft Polymers Possessing Block Copolymer Graft Chains
Authors: Ding J. , Tang Q. , Holdcroft S.
Published: March 2003

Ionic graft membranes comprising macromonomeric poly(styrene-block-styrene sulfonic acid) grafted polystyrene [PS-g-mac(PS-b-PSSA)] polymers were prepared by copolymerization of styrene and poly(styrene-block-sodium styrene sulfonate) (PS-b-PSSNa) macromonomers followed by ion-exchange. The latter were prepared with controlled molecular weight by stable free radical polymerization. Membranes exhibit varying degrees of phase separation. Membranes of low ion content are comprised of isolated ionic domains and exhibit low ionic conductivity. Increasing the number density of ionic graft chains in the polymer results in a network of nanochannels and a dramatic increase in ion conductivity. In comparison to analogous macromonomeric poly(styrene sulfonic acid) grafted polystyrene (PS-g-macPSSA) membranes, of similar ion exchange capacity (IEC) and PSSA chain length, dehydrated PS-g-mac(PS-b-PSSA) membranes consist of smaller, more densely connected ionic domains; however, water sorption and ionic conductivity are similar.
Electrochemistry, Protein Binding and Crystal Structures of Platinum(II) and Platinum(IV) Carboxylato Complexes
Authors: Battle Andrew R. , Deacon Glen B. , Dolman Rachael C. , Hambley Trevor W.
Published: March 2003

The crystal structures of the platinum(II) complexes [Pt(ox)(en)] (ox = oxalato, en = ethane-1,2-diamine) and [Pt(ethmal)(en)] (ethmal = ethylmalonato), and of their platinum(IV) analogues, trans-[Pt(OH)2(ox)(en)].H2O and trans-[Pt(ethmal)(OH)2(en)], have been determined. All crystallize in the monoclinic space group P21/c, with the exception of trans-[PtIV(OH)2(ox)(en)].H2O which crystallizes in C2/c. The ethylmalonato ligand in [PtII(ethmal)(en)] adopts a pseudo-boat conformation. Changes in the fold angles of the boat occur on oxidation and introduction of the trans hydroxo ligands. The cathodic forward half-wave potentials of the platinum(iv) complexes (including trans-[Pt(mal)(OH)2(en)], mal = malonato) are reported and reveal that these complexes are more difficult to reduce than analogous complexes with equatorial chloro ligands. The binding of trans-[Pt(OH)2(ox)(en)].H2O and trans-[Pt(mal)(OH)2(en)] to mouse albumin was investigated with no binding observed after 6 h and a very small amount observed for the latter complex after 24 h.
N-Methyldiethanolamine-Modified Titanium Isopropoxide: X-Ray Crystal Structure of [Ti2(μ2-(OCH2CH2)2NCH3)(μ2-OPri)(OPri)5]
Authors: Kemmitt T. , Al-Salim N. I. , Gainsford G. J.
Published: March 2003

A highly fluxional dititanium N-methyldiethoxoamine hexaisopropoxide complex was isolated from reactions of N-methyldiethanolamine with Ti(OPri)4. X-ray crystallography identified the solid state compound as the unsymmetrical complex Ti2(μ2-(OCH2CH2)2NCH3)(μ2-OPri)(OPri)5. In solution, the time-averaged structure was shown by NMR to be symmetrical. The amine function coordinates to both titanium atoms alternately, while the isopropoxide ligands exchange to maintain equal coordination numbers on both titaniums. Variable temperature NMR demonstrates that the exchange processes slow on cooling, and a spectrum consistent with the solid-state structure is apparent at –50�C.
Synthesis and Complexation of a Chiral Sexidentate Pendant-Arm Macropolycyclic Polyamino Acid
Authors: Wei G. , Hambley T. W. , Lawrance G. A. , Maeder M.
Published: March 2003

The reaction of the acyclic complex ion (methyl (SS,SS)-3-[(2�-aminocyclohexyl)amino]-2-[(2�-aminocyclohexyl)-aminomethyl]propionate)copper(II) with formaldehyde and nitroethane in basic solution yields the pendant-arm macrocyclic complex (SS,SS)-(methyl-15-methyl-15-nitro-2,6,13,17-tetraazatricyclo[16.4.0.07,12]docosane-4-carboxylate)copper(ii) ion. Reduction with zinc in hydrochloric acid yields the hydrochloride salt of the pendant-arm macrocycle (SS,SS)-15-amino-15-methyl-2,6,13,17-tetraazatricyclo[16.4.0.07,12]docosane-4-carboxylic acid (1), separated into and isolated as the major trans (1a) and minor cis (1b) isomers. Co-ordination of (1) to several metal ions [CoIII, CrIII, NiII, ZnII, CuII] and comparison with a previously reported analogue without the cyclohexane rings, trans-13-amino-13-methyl-1,4,8,11-tetraazacyclotetradecane-6-carboxylic acid (2a) salt, is described. The [Ni{(1a) – H+}](ClO4) crystallizes in the monoclinic space group P21, a 9.710(2), b 14.442(1), c 10.317(2) Å, β 96.02(2)°. The nickel displays a distorted octahedral geometry, with all four secondary amines coordinated (Ni–N range 2.044(7)–2.063(6) Å), in addition to pendant primary amine (Ni–N, 2.109(6) Å) and carboxylate (Ni–O, 2.100(6) Å) groups. Protonation constants for the trans (1a) and cis (1b) isomers and stability constants of these isomers with the labile metal ions ZnII, CdII, HgII, PbII, MnII, and CoII were determined by potentiometric titrations. The log K values for 1 : 1 complexes show small variations between geometric isomers.
An Unexpected Zinc Coordination Polymer formed during the Preparation of 5-Substituted 1H-Tetrazoles from a Nitrile in Water
Authors: Xue X. , Abrahams B. F. , Xiong R.-G. , You X.-Z.
Published: March 2003

The reaction of N,N�-dicyanohydrazine with ZnCl2 and NaN3 in water unexpectedly affords 5-aminotetrazolato hydroxo zinc rather than a zinc complex with bis(tetrazolyl)hydrazine. An N–N bond cleavage has occurred in the Demko–Sharpless' tetrazole synthesis.
Competitive Reactions During Amine Addition to cis-Aconityl Anhydride
Authors: Dinand E. , Zloh M. , Brocchini S.
Published: March 2003

Amine addition to cis-aconityl anhydride has been used to prepare monomers needed to make water-soluble polymers that are being developed for biomedical applications. Unfortunately competitive decarboxylation, double bond isomerization, and hydrolysis reactions of cis-aconityl anhydride have been observed during monomer synthesis. Since cis-aconityl anhydride has also been used for bioconjugation applications, these deleterious side reactions should be accounted for. Reactions and product profiles of cis-aconityl anhydride with amines and amino acids in aqueous and organic media are described. The side reactions could be avoided with weakly nucleophilic aromatic amines and by the interfacial reaction of glycine with cis-aconityl anhydride.
Synthesis and Preliminary Pharmacological Evaluation of 4´-Arylmethyl Analogues of Clozapine. I. The Effect of Aromatic Substituents
Authors: Capuano B. , Crosby I. T. , Lloyd E. J. , Taylor D. A.
Published: March 2003

As part of a research program to develop compounds with mixed dopamine D4 and serotonin 5-HT2A antagonist activity with potential for the treatment of schizophrenia, we report a family of compounds based on structural modification of the atypical antipsychotic, clozapine (2). The chemical synthesis, structural characterization and pharmacological evaluation of a series 4�-arylmethyl analogues of clozapine are described. Preliminary receptor binding data are presented, examining primarily the electronic and positional effects of substituents on the introduced arylmethyl group, and secondarily the nature of the aryl ring.
Antioxidant Behaviour of Thia Fatty Acids
Authors: Easton C. J. , Ferrante A. , Robertson T. A. , Xia L.
Published: March 2003

Eight thia fatty acids and other sulfides have been studied as inhibitors of autoxidation of arachidonic acid. The inhibitors extend the lag phase of the oxidation, to varying degrees. A carboxyl group in the vicinity of the sulfur reduces the antioxidant activity, while unsaturated sulfides are more effective than their saturated analogues. The results are consistent with the sulfides acting to reduce fatty acid hydroperoxides, which otherwise accumulate during the early stages of reaction and propagate the free-radical oxidation process.
Synthesis of Some Nefopam Analogues as Potential Analgesics
Authors: Rosamilia A. E. , Mayes P. A. , Papadopoulos R. , Campi E. M. , Jackson W. R. , Rash L. , Jarrott B.
Published: March 2003

Some derivatives of the non-narcotic analgesic nefopam containing amidine and guanidine substituents have been prepared and their analgesic activity assessed by their ability to block the uptake of noradrenaline. The compounds have been shown to inhibit noradrenaline uptake but they also display possible α1 antagonist activity at higher concentration. An ester derivative was also active and was more selective as it did not exhibit α1 adrenoreceptor antagonism.
Catalytic Chain Transfer Polymerization: an Overview
Authors: Heuts J. P. A. , Roberts G. E. , Biasutti J. D.
Published: March 2003

Catalytic chain transfer polymerization is a very efficient and versatile free-radical polymerization technique for the synthesis of functional macromonomers. The process is based on the ability of certain transition metal complexes, most notably of low-spin CoII complexes such as cobaloximes, to catalyse the chain transfer to monomer reaction. A brief overview is given of the applications and the mechanistic understanding of catalytic chain transfer polymerization.
Insights into the van der Waals Radius of Low-Spin Ni(ii) fromMolecular Mechanics Studies and the Crystal Structures of [Ni(cis-cyclohexane-1,3-diamine)2]Cl2, [Ni{(R)-5,5,7-trimethyl-1,4-diazacycloheptane}2]Cl2·H2O and [Ni(5,7-dimethyl-1,4-diazacycloheptane)2](ClO4)2. Synthesis of 5,7-Dimethyl-1,4-diazacycloheptane and an Improved Synthesis of cis-Cyclohexane-1,3-diamine
Authors: Munk V. P. , Cham S. T. , Fenton R. R. , Hocking R. K. , Hambley T. W.
Published: March 2003

The structures of three bis(diamine)nickel(II) complexes, chosen to shed light on the van der Waals radius of nickel(II), are described. [Ni(cis-1,3-chxn)2]Cl2 (cis-1,3-chxn = cis-cyclohexane-1,3-diamine) crystallizes in the monoclinic space group P21/n, with a 6.397(2), b 16.463(4), c 7.229(2) Å, b 90.70(2)�, and its structure has been refined to an R value of 0.031 on 1214F. [Ni{(R)-tmdz}2]Cl2�H2O (tmdz = 5,5,7-trimethyl-1,4-diazacycloheptane) crystallizes in the orthorhombic space group P212121, with a 10.678(1), b 11.073(5), c 17.968(6) Å, and its structure has been refined to an R value of 0.031 on 1586F. [Ni(dmdz)2](ClO4)2 (dmdz = 5,7-dimethyl-1,4-diaza- cycloheptane) crystallizes in the monoclinic space group P21/n, with a 9.582(1), b 10.390(2), c 11.817(3) Å, β 96.19(2)�, and its structure has been refined to an R value of 0.059 on 817F. In all three structures, short Ni���H and Ni���C interactions, ranging from 2.37 to 2.61 Å and 2.99 to 3.03 Å, respectively, are observed. Using molecular mechanics modelling to reproduce these separations, we have arrived at a van der Waals radius of 1.35 Å for low-spin nickel(ii). Analysis of Ni���O contacts in the solid state leads to a van der Waals radius of about 1.26 Å, which is consistent with the molecular mechanics derived value since these are usually longer.