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71.
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Aaron J. Scott Julia Vallejo Arup Sarkar Lucy Smythe E. Regincs Martí Gary S. Nichol Wim T. Klooster Simon J. Coles Mark Murrie Gopalan Rajaraman Stergios Piligkos Paul J. Lusby Euan K. Brechin 《Chemical science》2021,12(14):5134
Reaction of Ni(OTf)2 with the bisbidentate quaterpyridine ligand L results in the self-assembly of a tetrahedral, paramagnetic cage [NiII4L6]8+. By selectively exchanging the bound triflate from [OTf⊂NiII4L6](OTf)7 (1), we have been able to prepare a series of host–guest complexes that feature an encapsulated paramagnetic tetrahalometallate ion inside this paramagnetic host giving [MIIX4⊂NiII4L6](OTf)6, where MIIX42− = MnCl42− (2), CoCl42− (5), CoBr42− (6), NiCl42− (7), and CuBr42− (8) or [MIIIX4⊂NiII4L6](OTf)7, where MIIIX4− = FeCl4− (3) and FeBr4− (4). Triflate-to-tetrahalometallate exchange occurs in solution and can also be accomplished through single-crystal-to-single-crystal transformations. Host–guest complexes 1–8 all crystallise as homochiral racemates in monoclinic space groups, wherein the four {NiN6} vertexes within a single Ni4L6 unit possess the same Δ or Λ stereochemistry. Magnetic susceptibility and magnetisation data show that the magnetic exchange between metal ions in the host [NiII4] complex, and between the host and the MX4n− guest, are of comparable magnitude and antiferromagnetic in nature. Theoretically derived values for the magnetic exchange are in close agreement with experiment, revealing that large spin densities on the electronegative X-atoms of particular MX4n− guest molecules lead to stronger host–guest magnetic exchange interactions.The tetrahedral [NiII4L6]8+ cage can reversibly bind paramagnetic MX41/2− guests, inducing magnetic exchange interactions between host and guest. 相似文献
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A very simple and rapid procedure is described in which the addition of a large amount of Zn(II) to a water sample before extraction by 2-mercaptobenzothiazole into n-butyl acetate brings about almost total extraction of Cd and allows determination of concentrations down to at least 0.02 ng/ml. High precision is achieved, and the interference of cyanide is also overcome. 相似文献
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Comprehensive studies of the extraction of the molybdenum-thiocyanate complex with methyl isobutyl ketone have resulted in an improved method for the determination of traces of molybdenum in soils and geological materials by atomic-absorption spectroscopy. The method is applicable in the range 1-500 ppm Mo, with 1-g samples, giving relative standard deviations not exceeding about 8% at a level of 1 ppm. The limit of detection is 0.1 ppm. There are few interferences, and large quantities of iron are without effect. 相似文献
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The progress of atomic absorption spectrometry has been reviewed for the period 1955–1971. Topics discussed are: the volume of literature, countries in which research was carried out and the language in which the work was published, the identity of the principal journals which publish atomic absorption papers, broad categories of research, and the economic benefit of the technique. 相似文献
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An experimental rig has been developed to study the effects of electric and acoustic field combinations on the filtration rate of titanium dioxide suspensions. Ultrasound energy is applied tangentially to the filter medium. Electric field strengths, suspension characteristics and process parameters can all be varied independently. Results from an experimental programme demonstrate that the use of ultrasound across the cake surface can decrease the specific cake flow resistance and increase the filtration rates of low-concentration rutile suspensions (0.1% v/v). Changes in the conductivity induced by ultrasonic irradiation affect the suspension such that the application of an electrical field is enhanced, giving an equivalent electric field strength higher than that applied. 相似文献