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排序方式: 共有102条查询结果,搜索用时 265 毫秒
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Metallation of hexahydropyrimidopyrimidine (hppH) by [Fe{N(SiMe(3))(2)}(2)] (1) produces the trimetallic iron(II) amide cage complex [{(Me(3)Si)(2)NFe}(2)(hpp)(4)Fe] (2), which contains three iron(II) centers, each of which resides in a distorted tetrahedral environment. An alternative, one-pot route that avoids use of the highly air-sensitive complex 1 is described for the synthesis of the iron(II)-lithium complex [{(Me(3)Si)(2)N}(2)Fe{Li(bta)}](2) (3) (where btaH = benzotriazole), in which both iron(II) centers reside in 3-coordinated pyramidal environments. The structure of 3 is also interpreted in terms of the ring laddering principle developed for alkali metal amides. Magnetic susceptibility measurements reveal that both compounds display very weak antiferromagnetic exchange between the iron(II) centers, and that the iron(II) centers in 2 and 3 possess large negative axial zero-field splittings. 相似文献
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Faust TB Bellini V Candini A Carretta S Lorusso G Allan DR Carthy L Collison D Docherty RJ Kenyon J Machin J McInnes EJ Muryn CA Nowell H Pritchard RG Teat SJ Timco GA Tuna F Whitehead GF Wernsdorfer W Affronte M Winpenny RE 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(50):14020-14030
We present a synthetic, structural, theoretical, and spectroscopic study of a family of heterometallic ring dimers which have the formula [{Cr(7)NiF(3)(Etglu)(O(2)CtBu)(15)}(2)(NLN)], in which Etglu is the pentadeprotonated form of the sugar N-ethyl-D-glucamine, and NLN is an aromatic bridging diimine ligand. By varying NLN we are able to adjust the strength of the interaction between rings with the aim of understanding how to tune our system to achieve weak magnetic communication between the spins, a prerequisite for quantum entanglement. Micro-SQUID and EPR data reveal that the magnetic coupling between rings is partly related to the through-bond distance between the spin centers, but also depends on spin-polarization mechanisms and torsion angles between aromatic rings. Density functional theory (DFT) calculations allow us to make predictions of how such chemically variable parameters could be used to tune very precisely the interaction in such systems. For possible applications in quantum information processing and molecular spintronics, such precise control is essential. 相似文献
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Shaw JL Wolowska J Collison D Howard JA McInnes EJ McMaster J Blake AJ Wilson C Schröder M 《Journal of the American Chemical Society》2006,128(42):13827-13839
The mononuclear +2 oxidation state metal complexes [Au([9]aneS(3))(2)](2+) and [Ag([18]aneS(6))](2+) have been synthesized and characterized crystallographically. The crystal structure of the Au(II) species [Au([9]aneS(3))(2)](BF(4))(2) shows a Jahn-Teller tetragonally distorted geometry with Au-S(1) = 2.839(5), Au-S(2) = 2.462(5), and Au-S(3) = 2.452(5) A. The related Ag(II) complex [Ag([18]aneS(6))](ClO(4))(2) has been structurally characterized at both 150 and 30 K and is the first structurally characterized complex of Ag(II) with homoleptic thioether S-coordination. The single-crystal X-ray structure of [Ag([18]aneS(6))](ClO(4))(2) confirms octahedral homoleptic S(6)-thioether coordination. At 150 K, the structure contains two independent Ag(II)-S distances of 2.569(7) and 2.720(6) A. At 30 K, the structure retains two independent Ag(II)-S distances of 2.615(6) and 2.620(6) A, with the complex cation retaining 3-fold symmetry. The electronic structures of [Au([9]aneS(3))(2)](2+) and [Ag([18]aneS(6))](2+) have been probed in depth using multifrequency EPR spectroscopy coupled with DFT calculations. For [Au([9]aneS(3))(2)](2+), the spectra are complex due to large quadrupole coupling to (197)Au. Simulation of the multifrequency spectra gives the principal g values, hyperfine (A) and quadrupole (P) couplings, and furthermore reveals non-co-incidence of the principal axes of the P tensor with respect to the A and g matrices. These results are rationalized in terms of the electronic and geometric structure and reveal that the SOMO has ca. 30% Au 5d(xy)() character, consistent with DFT calculations (27% Au character). For [Ag([18]aneS(6))](2+), detailed EPR spectroscopic analysis confirms that the SOMO has ca. 26% Ag 4d(xy)() character and DFT calculations are consistent with this result (22% Ag character). 相似文献
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Stergios Piligkos Dr. Høgni Weihe Dr. Eckhard Bill Dr. Frank Neese Prof. Dr. Hassane El Mkami Dr. Graham M. Smith Dr. David Collison Prof. Gopalan Rajaraman Dr. Grigore A. Timco Dr. Richard E. P. Winpenny Prof. Eric J. L. McInnes Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(13):3152-3167
Spinning wheels : The presented highly resolved multifrequency continuous wave EPR spectra (e.g., see figure) of the heterooctametalic “wheels” Cr7M provide rare examples of high nuclearity polymetallic systems where detailed information on the spin‐Hamiltonian parameters of the ground and excited spin states is observed.
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Michael L. Baker Marzio Rancan Floriana Tuna Grigore A. Timco David Collison Hannu Mutka Hans-Ulrich Güdel Robin J. Pritchard Richard E. P. Winpenny Eric J. L. McInnes 《Applied magnetic resonance》2010,37(1-4):685-692
The synthesis, magnetic and electron paramagnetic resonance (EPR) characterisation of isolated, discrete, {Cr n III } antiferromagnetically coupled chain complexes is reported for n = 6 and 7. Previous studies had reported supramolecular linked {Cr n III } x species. For n = 6, the lowest lying total spin state is diamagnetic with S = 1 and 2 first and second excited states, respectively; for n = 7, the lowest lying total spin state is S = 3/2 with S = 1/2 and 5/2 first and second excited states, respectively. The zero-field splittings of these states are well defined by low-temperature, multi-frequency EPR spectroscopy. 相似文献