Structural and spectroscopic insights on the coordination chemistry of the rigid heterotopic chelating ligand 1H-pyrazolo[4,3-h]quinoline

In this work we report the coordination chemistry of a rigid heterotopic ligand 1H-pyrazolo[4,3-h]quinoline HL1 in copper(II) and zinc(II) complexes for the first time, and examine both the structural properties and solution-phase behaviour of these species. On reaction with zinc(II) nitrate in acetonitrile, a mononuclear complex [Zn(HL1)2(OH2)2](NO3)2 1 is generated, where a size mismatch between the metal ion and the binding pocket leads to an anomalously long Zn-N bond to the pyrazole nitrogen atom. This is consistent with solution-state absorption and fluorescence measurements which indicate a relatively low stability constant logß of 9.1(3) in acetonitrile. The reaction of HL1 with copper(II) nitrate in methanol gave four new crystalline phases, the major forms of which being two polymorphs of the complex [Cu2(µ2-L1)2(NO3)2(MeOH)2] 2a and 2ß which also constitutes the dominant solution-phase behaviour of this mixture. Additionally, trace amounts of the nitric acid salt of HL1 were crystallised, along with the slow formation of a tetranuclear species [Cu4(µ2-L1)6(OH2)2](NO3)2·2MeOH 3 which also features anomalously long bridging distances from the L1 ligand as a result of its backbone rigidity

Quantification of Ultrasound Correlation‐Based Flow Velocity Mapping and Edge Velocity Gradient Measurement

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135662/1/jum201332101815.pd

Trace CO2 capture by an ultramicroporous physisorbent with low water affinity.

CO2 accumulation in confined spaces represents an increasing environmental and health problem. Trace CO2 capture remains an unmet challenge because human health risks can occur at 1000 parts per million (ppm), a level that challenges current generations of chemisorbents (high energy footprint and slow kinetics) and physisorbents (poor selectivity for CO2, especially versus water vapor, and/or poor hydrolytic stability). Here, dynamic breakthrough gas experiments conducted upon the ultramicroporous material SIFSIX-18-Ni-β reveal trace (1000 to 10,000 ppm) CO2 removal from humid air. We attribute the performance of SIFSIX-18-Ni-β to two factors that are usually mutually exclusive: a new type of strong CO2 binding site and hydrophobicity similar to ZIF-8. SIFSIX-18-Ni-β also offers fast sorption kinetics to enable selective capture of CO2 over both N2 (S CN) and H2O (S CW), making it prototypal for a previously unknown class of physisorbents that exhibit effective trace CO2 capture under both dry and humid conditions

Exploiting the labile site in dinuclear [Pd2L2]n+ metallo-cycles: multi-step control over binding affinity without alteration of core host structure

While Nature often controls supramolecular processes through regulation giving multiple levels of activity, synthetic metallosupramolecular systems have generally been binary (e.g. on/off) when they have control over molecular recognition events, and have often relied upon drastic chemical transformations or complete disassembly to enforce this control. We report here a new low symmetry ligand with a bidentate and a monodentate site (L). In combination with Pd2+, this ligand forms a [2 + 2] metallo-macrocycle, [Pd2L2L′2]n+, where L′ is the monodentate ancillary ligand that occupies the fourth and final coordination site of the metal ions. This assembly is structurally simple, but displays nuanced, multi-step binding affinity toward a neutral diplatinate guest employed for proof-of-concept. This complexity is introduced through varying the identity of L′, which can either be solvent (DMSO) or the halides chloride, bromide or iodide. The identity of L′ alters the cationic charge of the complex (neutral DMSO versus monoanionic halides) or otherwise influences the electron deficiency of the binding site of the host through varied strength of halide-ligand intra-molecular hydrogen bonding. Cycling between these different complexes was demonstrated, except for L′ = chloride which is non-reversible. This system therefore is able to interact with a platinate guest with four different graduations of affinity in response to stimuli, while still retaining the same simple core cationic structure. In addition to multi-setting binding affinity, we believe this is the first example of the use of variable intramolecular hydrogen bonding strength in switchable ancillary ligands to alter the electronic character and hence the π-π recognition characteristics of a metallosupramolecular host.DP would like to thank the ARC for a DECRA Fellowship, and the Royal Society of New Zealand for a Rutherford Postdoctoral Fellowship. BH would like to gratefully acknowledge the MBIE Catalyst Fund for a PhD scholarship. RV would like to thank the University of Otago for a PhD scholarship. The authors would like to thank the Australia National University, the University of Canterbury, the University of Otago, and the MacDiarmid Institute for additional funding. The authors acknowledge the contribution of the NeSI high performance computing facilities to the results of this research. New Zealand’s national facilities are provided by the New Zealand eScience Infrastructure and funded jointly by NeSI’s collaborator institutions and through the Ministry of Business, Innovation & Employment’s Research Infrastructure program. https://www.nesi.org.nz

Two-step stabilization of orbital order and the dynamical frustration of spin in the model charge-transfer insulator KCuF3

We report a combined experimental and theoretical study of KCuF3, which offers - because of this material's relatively simple lattice structure and valence configuration (d9, i.e., one hole in the d-shell) - a particularly clear view of the essential role of the orbital degree of freedom in governing the dynamical coupling between the spin and lattice degrees of freedom. We present Raman and x-ray scattering evidence that the phase behaviour of KCuF3 is dominated above the Neel temperature (T_N = 40 K) by coupled orbital/lattice fluctuations that are likely associated with rotations of the CuF6 octahedra, and we show that these orbital fluctuations are interrupted by a static structural distortion that occurs just above T_N. A detailed model of the orbital and magnetic phases of KCuF3 reveals that these orbital fluctuations - and the related frustration of in-plane spin-order-are associated with the presence of nearly degenerate low-energy spin-orbital states that are highly susceptible to thermal fluctuations over a wide range of temperatures. A striking implication of these results is that the ground state of KCuF3 at ambient pressure lies near a quantum critical point associated with an orbital/spin liquid phase that is obscured by emergent Neel ordering of the spins; this exotic liquid phase might be accessible via pressure studies.Comment: 13 pages, 3 figure

Long-cavity [Pd2L4]4+ cages and designer 1,8-naphthalimide sulfonate guests: rich variation in affinity and differentiated binding stoichiometry

One of the most appealing features of [Pd2L4]4+ cages is their well-defined cavities, giving binding affinity for specific guests. If seeking to bind larger and more complex guests, an attractive strategy is to lengthen the ligand backbone and therefore the inter-palladium(II) distance and cavity length. In comparison to large hollow [PdnL2n]2n+ polyhedra, this approach retains a well-ordered cavity environment. We report here a novel ligand, 1,3-bis(4-(4-ethynylpyridine)-phenyl)-adamantane, that has a hydrophobic bis(phenyl)adamantane core and forms [Pd2L4]4+ cages with a large 19 Å inter-palladium(II) cavity length. This cage binds long designer anions: naphthalimide sulfonates at ≥15 Å in length, which consist of two distinct domains: a naphthalimide and a phenyl sulfonate. This binding derives from hydrogen bonding between the endohedral pyridyl protons of the cage and the phenyl sulfonate group, and π–hydrophobic interactions between the adamantane core and the naphthalimide unit. The strength of binding depends on the degree of electron deficiency of the naphthalimide, brought about by the nature of substituents on this moiety, with binding constants for monoanionic guests ranging from 400 to 1800 M−1. The host/guest stoichiometry was found to be 1 : 2, unless the guest possessed a second sulfonate group, and was small enough to fit end-to-end within the cavity, in which case the stoichiometry was 1 : 1, and resulted in a high binding constant (for DMSO solvent) of 6100 M−1. This work demonstrates the subtle interplay and potential between cages and guests that are both large and that both have distinct dual zones able to interact with each other, and offers a pathway to specific and tunable binding of large guests.The authors would like to thank the University of Canterbury, the Australian National University, Massey University Albany and the University of Otago for funding. DP, KP and PK would like to thank the MacDiarmid Institute for funding. DP would like to thank the Royal Society of New Zealand for a Rutherford Postdoctoral Fellowship, and the Australian Research Council for a DECRA Fellowship

Improving the stellarator through advances in plasma theory

Improvements to the stellarator concept can be realized through advancements in theoretical and computational plasma physics. Herein, recent advances are reported in the topical areas of: 1) improved energetic ion confinement, 2) the impact of three-dimensional (3D) shaping on turbulent transport, 3) reducing coil complexity, 4) novel optimization and design methods, and 5) computational MHD tools. These advances enable the development of new stellarator configurations with improved confinement properties.</p

Design and Psychometrics for New Measures of Health-Related Quality of Life in Adults with Type 1 Diabetes: Type 1 Diabetes and Life (T1DAL)

AIMS: To use a three-phase process to develop and validate new self-report measures of diabetes-specific health-related quality of life (HRQOL) for adults with type 1 diabetes. We report on four versions of the Type 1 Diabetes and Life (T1DAL) measure for people age 18-25, 26-45, 46-60, and over 60 years. METHODS: We first conducted qualitative interviews to guide measure creation, then piloted the draft measures. We evaluated psychometric properties at six T1D Exchange Clinic Network sites via completion of T1DAL and validated measures of related constructs. Participants completed the T1DAL again in 4-6 weeks. We used psychometric data to reduce each measure to 23-27 items in length. Finally, we obtained participant feedback on the final measures. RESULTS: The T1DAL-Adult measures demonstrated good internal consistency (α=0.85-0.88) and test-retest reliability (r=0.77-0.87). Significant correlations with measures of general quality of life, generic and diabetes-specific HRQOL, diabetes burden, self-management, and glycemic control demonstrated validity. Factor analyses yielded 4-5 subscales per measure. Participants were satisfied with the final measures and reported they took 5-10 minutes to complete. CONCLUSIONS: The strong psychometric properties of the newly developed self-report T1DAL measures for adults with type 1 diabetes make them appropriate for use in clinical research and care

Multi-Jet Event Rates in Deep Inelastic Scattering and Determination of the Strong Coupling Constant

Jet event rates in deep inelastic ep scattering at HERA are investigated applying the modified JADE jet algorithm. The analysis uses data taken with the H1 detector in 1994 and 1995. The data are corrected for detector and hadronization effects and then compared with perturbative QCD predictions using next-to-leading order calculations. The strong coupling constant alpha_S(M_Z^2) is determined evaluating the jet event rates. Values of alpha_S(Q^2) are extracted in four different bins of the negative squared momentum transfer~\qq in the range from 40 GeV2 to 4000 GeV2. A combined fit of the renormalization group equation to these several alpha_S(Q^2) values results in alpha_S(M_Z^2) = 0.117+-0.003(stat)+0.009-0.013(syst)+0.006(jet algorithm).Comment: 17 pages, 4 figures, 3 tables, this version to appear in Eur. Phys. J.; it replaces first posted hep-ex/9807019 which had incorrect figure 4

The synthesis and characterisation of coordination and hydrogen-bonded networks based on 4-(3,5-dimethyl-1H-pyrazol-4-yl)benzoic acid

The synthesis, structural and thermal characterisation of a number of coordination complexes featuring the N,O-heteroditopic ligand 4-(3,5-dimethyl-1H-pyrazol-4-yl)benzoate, HL are reported. The reaction of H2L with cobalt(II) and nickel(II) nitrates at room temperature in basic DMF/H2O solution gave discrete mononuclear coordination complexes with the general formula {[M(HL)2(H2O)4]·2DMF} (M = Co (1), Ni (2)), whereas the reaction with zinc(II) nitrate gave [Zn(HL)2]∞, 3, a coordination polymer with distorted diamondoid topology and fourfold interpenetration. Coordination about the tetrahedral Zn(II) nodes in 3 are furnished by two pyrazolyl nitrogen atoms and two carboxylate oxygen atoms to give a mixed N2O2 donor set. Isotopological coordination polymers of zinc(II), {[Zn(HL)2]·2CH3OH·H2O}∞, 4, and cobalt(II), [Co(HL)2]∞, 5, are formed when the reactions are carried out under solvothermal conditions in methanol (80 °C) and water (180 °C), respectively. The reaction of H2L with cadmium(II) nitrate at room temperature in methanol gives {[Cd(HL)2(MeOH)2]·1.8MeOH}∞6, a 2-D (4,4)-connected coordination polymer, whereas with copper(II) the formation of green crystals that transform into purple crystals is observed. The metastable green phase [Cu3(HL)4(μ2-SO4)(H2O)3]∞, 7, crystallises with conserved binding domains of the heteroditopic ligand and contains two different metal nodes: a dicopper carboxylate paddle wheel motif, and, a dicopper unit bridged by sulfate ions and coordinated by ligand pyrazolyl nitrogen atoms. The resultant purple phase {[Cu(HL)2]·4CH3OH·H2O}∞, 8, however, has single copper ion nodes coordinated by mixed N2O2 donor sets with trans-square planar geometry and is threefold interpenetrated. The desolvation of 8 was followed by powder X-ray diffraction and single crystal X-ray diffraction which show desolvation induces the transition to a more closely packed structure while the coordination geometry about the copper ions and the network topology is retained. Powder X-ray diffraction and microanalysis were used to characterise the bulk purity of the coordination materials 1-6 and 8. The thermal characteristics of 1-2, 4-6 and 8 were studied by TG-DTA. This led to the curious observation of small exothermic events in networks 4, 6, and 8 that appear to be linked to their decomposition. In addition, the solid state structures of H2L and that of its protonated salt, H2L·HNO3, were also determined and revealed that H2L forms a 2-D hydrogen bonded polymer incorporating helical chains formed through N-HO and O-HN interactions, and that [H3L]NO3 forms a 1-D hydrogen-bonded polymer