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91.
92.
93.
Jones LF Inglis R Cochrane ME Mason K Collins A Parsons S Perlepes SP Brechin EK 《Dalton transactions (Cambridge, England : 2003)》2008,(44):6205-6210
The synthesis and magnetic properties of three new members of a family of salicyaldoxime based [Mn6] single-molecule magnets possessing new structural types, core topologies and Mn oxidation state distributions are reported. The isostructural complexes [MnIII6O2(R-sao)6(X)2(EtOH)6] (R = Et, X = Br (1); R = Me, X = I (2)) exhibit single-molecule magnet behaviour with spin Hamiltonian parameters S = 12, g = 1.98 and D = -0.36 cm(-1) in both cases. The hexametallic cluster [MnIII4MnIV2O2(OMe)(4-)(Et-sao)6(MeOH)2].MeOH (3.MeOH) possesses a planar rod-like topology and a mixed valent [MnIV4MnIII2] core, which is unprecedented in this family of [Mn6] SMMs. 相似文献
94.
Karotsis G Jones LF Papaefstathiou GS Collins A Parsons S Nguyen TD Evangelisti M Brechin EK 《Dalton transactions (Cambridge, England : 2003)》2008,(36):4917-4925
We report the synthesis of a series of mixed valence Mn(II/IV) tetranuclear clusters [Mn(II)(2)Mn(IV)(2)O(2)(heed)(2)(EtOH)(6)Br(2)]Br(2) (), [Mn(II)(2)Mn(IV)(2)O(2)(heed)(2)(H(2)O)(2)Cl(4)].2EtOH.H(2)O (.2EtOH.H(2)O), [Mn(II)(2)Mn(IV)(2)O(2)(heed)(2)(heedH(2))(2)](ClO(4))(4) (), [Mn(II)(2)Mn(IV)(2)O(2)(heed)(2)(MeCN)(2)(H(2)O)(2)(bpy)(2)](ClO(4))(4) () and [Mn(II)(2)Mn(IV)(2)O(2)(heed)(2)(bpy)(2)Br(4)].2MeOH (.2MeOH). Clusters are constructed from the tripodal ligand N,N-bis(2-hydroxyethyl)ethylene diamine (heedH(2)) and represent rare examples of tetranuclear Mn clusters possessing the linear trans zig-zag topology, being the first Mn(II/IV) mixed-valent clusters of this type. The molecular clusters can then be used as building blocks in tandem with the (linear) linker dicyanamide ([N(CN)(2)](-), dca(-)) for the formation of a novel extended network {[Mn(II)(2)Mn(IV)(2)O(2)(heed)(2)(H(2)O)(2)(MeOH)(2)(dca)(2)]Br(2)}(n) (), which exhibits a rare form of the 2D herring bone topology. 相似文献
95.
Higher oxidation states of americium have long been known; however, options for their preparation in acidic solution are limited. The conventional choice, silver-catalyzed peroxydisulfate, is not useful at nitric acid concentrations above about 0.3 M. We investigated the use of sodium bismuthate as an oxidant for Am (3+) in acidic solution. Room-temperature oxidation produced AmO 2 (2+) quantitatively, whereas oxidation at 80 degrees C produced AmO 2 (+) quantitatively. The efficacy of the method for the production of oxidized americium was verified by fluoride precipitation and by spectroscopic absorbance measurements. We performed absorbance measurements using a conventional 1 cm cell for high americium concentrations and a 100 cm liquid waveguide capillary cell for low americium concentrations. Extinction coefficients for the absorbance of Am (3+) at 503 nm, AmO 2 (+) at 514 nm, and AmO 2 (2+) at 666 nm in 0.1 M nitric acid are reported. We also performed solvent extraction experiments with the hexavalent americium using the common actinide extraction ligand tributyl phosphate (TBP) for comparison to the other hexavalent actinides. Contact with 30% tributyl phosphate in dodecane reduced americium; it was nevertheless extracted using short contact times. The TBP extraction of AmO 2 (2+) over a range of nitric acid concentrations is shown for the first time and was found to be analogous to that of uranyl, neptunyl, and plutonyl ions. 相似文献
96.
Crowley JD Leigh DA Lusby PJ McBurney RT Perret-Aebi LE Petzold C Slawin AM Symes MD 《Journal of the American Chemical Society》2007,129(48):15085-15090
We report the design, synthesis, characterization, and operation of a [2]rotaxane in which a palladium-complexed macrocycle can be translocated between 4-dimethylaminopyridine and pyridine monodentate ligand sites via reversible protonation, the metal remaining coordinated to the macrocycle throughout. The substitution pattern of the ligands and the kinetic stability of the Pd-N bond means that changing the chemical state of the thread does not automatically cause a change in the macrocycle's position in the absence of an additional input (heat and/or coordinating solvent/anion). Accordingly, under ambient conditions any of the four sets of protonated and neutral, stable, and metastable co-conformers of the [2]rotaxane can be selected, manipulated, isolated, and characterized. 相似文献
97.
X-Ray Photoelectron Spectroscopy (XPS) was used to quantify the amount of bromide ions present in two samples of [C(4)mpyrr]Br dissolved in the room temperature ionic liquid (RTIL) [C(4)mpyrr][N(Tf)2]. One sample was of a known concentration (0.436 Br atom%); the other was a saturated solution. The results obtained from quantitative XPS analysis indicated that the saturated sample had a concentration, or solubility, of 0.90 Br atom% (746 mM) at 298 K, which was then independently confirmed by potential-step chronoamperometry of the same solution. 相似文献
98.
Stapleton HM Keller JM Schantz MM Kucklick JR Leigh SD Wise SA 《Analytical and bioanalytical chemistry》2007,387(7):2365-2379
Standard reference materials (SRMs) are valuable tools in developing and validating analytical methods to improve quality
assurance standards. The National Institute of Standards and Technology (NIST) has a long history of providing environmental
SRMs with certified concentrations of organic and inorganic contaminants. Here we report on new certified and reference concentrations
for 27 polybrominated diphenyl ether (PBDE) congeners in seven different SRMs: cod-liver oil, whale blubber, fish tissue (two
materials), mussel tissue and sediment (two materials). PBDEs were measured in these SRMs, with the lowest concentrations
measured in mussel tissue (SRM 1974b) and the highest in sediment collected from the New York/New Jersey Waterway (SRM 1944).
Comparing the relative PBDE congener concentrations within the samples, we found the biota SRMs contained primarily tetrabrominated
and pentabrominated diphenyl ethers, whereas the sediment SRMs contained primarily decabromodiphenyl ether (BDE 209). The
cod-liver oil (SRM 1588b) and whale blubber (SRM 1945) materials were also found to contain measurable concentrations of two
methoxylated PBDEs (MeO-BDEs). Certified and reference concentrations are reported for 12 PBDE congeners measured in the biota
SRMs and reference values are available for two MeO-BDEs. Results from a sediment interlaboratory comparison PBDE exercise
are available for the two sediment SRMs (1941b and 1944). 相似文献
99.
Khan A Silversides JD Madden L Greenman J Archibald SJ 《Chemical communications (Cambridge, England)》2007,(4):416-418
The copper(II) complex of a novel rhodamine-azamacrocycle conjugate binds to the CXCR4 chemokine receptor and competes effectively against anti-CXCR4 monoclonal antibodies. The copper macrocycle unit adopts a trans-II configuration in the solid state. 相似文献
100.
Berná J Brouwer AM Fazio SM Haraszkiewicz N Leigh DA Lennon CM 《Chemical communications (Cambridge, England)》2007,(19):1910-1912
Hydrogen bonding in a [2]rotaxane is shown to stabilise the phenolate anion of a coumaric amide chromophore by almost 3 pKa units; however, the effect on the UV spectral shift in the anion is small and, significantly given the photochemistry of PYP, despite the hydrogen bonding olefin photoisomerisation in the anionic rotaxane remains heavily suppressed. 相似文献