共查询到20条相似文献,搜索用时 15 毫秒
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M. A. Kiskin I. G. Fomina A. A. Sidorov G. G. Aleksandrov O. Yu. Proshenkina Zh. V. Dobrokhotova V. N. Ikorskii Yu. G. Shvedenkov V. M. Novotortsev I. L. Eremenko I. I. Moiseev 《Russian Chemical Bulletin》2004,53(11):2508-2518
The formation of magnetically active polynuclear FeIII pivalates in the FeSO4·7H2O-KOOCCMe3 system was studied. The reaction of FeSO4·7H2O (1) with KOOCCMe3 in EtOH in air afforded the antiferromagnetic trinuclear complex [Fe3O(OOCCMe3)6(H2O)3]+[OOCCMe3]–·3EtOH. A change of the solvent (EtOH) in this system to a 40:1 benzene—THF mixture resulted in the formation of the antiferromagnetic hexanuclear cluster [Fe6(O)2(OH)2(OOCCMe3)12(HOOCCMe3)(THF)]·1.5C6H6. The addition of trimethylacetic acid to EtOH and recrystallization from hexane gave rise to the antiferromagnetic coordination polymer [K2Fe4(O)2(OOCCMe3)10(HOOCCMe3)2(H2O)2]n (7). Recrystallization of the latter from acetonitrile afforded the antiferromagnetic tetranuclear complex K2Fe4(O)2(OOCCMe3)10(HOOCCMe3)2(MeCN)2. The structures of these compounds were established by X-ray diffraction analysis, and their magnetic susceptibilities and thermal decomposition were investigated.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2403–2413, November, 2004. 相似文献
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Boudalis AK Sanakis Y Clemente-Juan JM Donnadieu B Nastopoulos V Mari A Coppel Y Tuchagues JP Perlepes SP 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(8):2514-2526
Complexes [Fe9(X)2(O2CMe)8{(2‐py)2CO2}4] (X?=OH? ( 1 ), N3? ( 2 ), and NCO? ( 3 )) have been prepared by a route previously employed for the synthesis of analogous Co9 and Ni9 complexes, involving hydroxide substitution by pseudohalides (N3?, NCO?). As indicated by DC magnetic susceptibility measurements, this substitution induced higher ferromagnetic couplings in complexes 2 and 3 , leading to higher ground spin states compared to that of 1 . Variable‐field experiments have shown that the ground state is not well isolated from excited states, as a result of which it cannot be unambiguously determined. AC susceptometry has revealed out‐of‐phase signals, which suggests that these complexes exhibit a slow relaxation of magnetization that follows Arrhenius behavior, as observed in single‐molecule magnets, with energy barriers of 41 K for 2 (τ0=3.4×10?12 s) and 44 K for 3 (τ0=2.0×10?11 s). Slow magnetic relaxation has also been observed by zero‐field 57Fe Mössbauer spectroscopy. Characteristic integer‐spin electron paramagnetic resonance (EPR) signals have been observed at X‐band for 1 , whereas 2 and 3 were found to be EPR‐silent at this frequency. 1H NMR spectrometry in CD3CN has shown that complexes 1 – 3 are stable in solution. 相似文献
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The ultraviolet absorbance data from experiments conducted at constant pH and total iron concentration but variable B(OH)3 concentration were used to determined the stability constants of FeB(OH)
4
2+
and Fe[B(OH)4
2
+
at 25°C and an ionic strength of 0.68. The estimates obtained were *1 = 1.0 ± 0.2 × 10–2 and *2 = 2 ± 1 × 10–5, respectively (uncertainties are two times the standard error of the estimates). A calculation of the extent of iron(III) borate formation in ocean water at pH 8.2 shows that iron(III) borates are not a significantly large component of iron(III) speciation in seawater. 相似文献
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Shi W Chen XY Zhao YN Zhao B Cheng P Yu A Song HB Wang HG Liao DZ Yan SP Jiang ZH 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(17):5031-5039
A new series of oxovanadium(IV)-lanthanide(III) heteronuclear complexes [Yb(H2O)8]2[(VO)2(TTHA)](3)21 H2O (1), {[Ho(H2O)7(VO)2(TTHA)][(VO)2(TTHA)](0.5)} 8.5 H2O (2), {[Gd(H2O)7(VO)2(TTHA)][(VO)2(TTHA)](0.5)}8.5 H2O (3), {[Eu(H2O)7][(VO)2(TTHA)](1.5)} 10.5 H2O (4), and [Pr2(H2O)6(SO4)2][(VO)2(TTHA)] (5) (H6TTHA=triethylenetetraaminehexaacetic acid) were prepared by using the bulky flexible organic acid H(6)TTHA as structure-directing agent. X-ray crystallographic studies reveal that they contain the same [(VO)2(TTHA)]2- unit as building block, but the Ln3+ ion lies in different coordination environments. Although the lanthanide ions always exhibit similar chemical behavior, the structures of the complexes are not homologous. Compound 1 is composed of a [Yb(H2O)8]3+ ion and a [(VO)2(TTHA)]2- ion. Compounds 2 and 3 are isomorphous; both contain a trinuclear [Ln(H2O)7(VO)2(TTHA)]+ (Ln=Ho for 2 and Gd for 3) ion and a [(VO)2(TTHA)]2- ion. Compound 4 is an extended one-dimensional chain, in which each Eu3+ ion links two [(VO)2(TTHA)]2- ions. For 5, the structure is further assembled into a three-dimensional network with an interesting framework topology comprising V2Pr2 and V4Pr2 heterometallic lattices. Moreover, 4 and 5 are the first oxovanadium(IV)-lanthanide(III) coordination polymers and thus enlarge the realm of 3d-4f complexes. The IR, UV/Vis, and EPR spectra and the magnetic properties of the heterometallic complexes were studied. Notably, 2 shows unusual ferromagnetic interactions between the VO2+ and Ho3+ ions. 相似文献
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Luisa Gregoli Dr. Chiara Danieli Dr. Anne‐Laure Barra Dr. Petr Neugebauer Giovanna Pellegrino Dr. Giordano Poneti Roberta Sessoli Prof. Dr. Andrea Cornia Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(26):6456-6467
Tunable single‐molecule magnets : The spin‐level landscape in a series of FeIII4 single‐molecule magnets with propeller‐like structure was analyzed by means of high‐frequency EPR spectroscopy. The zero‐field splitting parameter D of the ground S=5 spin state correlates strongly with the pitch of the propeller γ (see picture), and thus provides a simple link between molecular structure and magnetic behavior.
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Ivan Nemec Roman Boča Radovan Herchel Zdeněk Trávníček Milan Gembický Wolfgang Linert 《Monatshefte für Chemie / Chemical Monthly》2009,140(7):815-828
Abstract A series of dinuclear Fe(III) complexes was synthesized in which the Schiff-base blocking ligand L5 coordinates each of the centers which are linked by a bidentate, bipyridine-type ligand. For these systems, [L5FeIII{bridge}FeIIIL5](BPh4)2, thermally induced spin crossover is observed. The corollary of the systems is that the spin crossover interferes with the
magnetic exchange interaction. The overlap of the energy bands of the LL and HH reference states (L, low-spin; H, high-spin)
causes the exchange interaction to act against the spin crossover (leading to incompleteness or gradual behavior).
Graphical abstract
相似文献
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Rebilly JN Charron G Rivière E Guillot R Barra AL Serrano MD van Slageren J Mallah T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(4):1169-1177
Pentacoordinate complexes in which Ni(II) is chelated by the tridentate macrocyclic ligand 1,4,7-triisopropyl-1,4,7-triazacyclononane (iPrtacn) of formula [Ni(iPrtacn)X(2)] (X=Cl, Br, NCS) have relatively large magnetic anisotropies, revealed by the large zero-field splitting (zfs) axial parameters |D| of around 15 cm(-1) measured by frequency-domain magnetic resonance spectroscopy (FDMRS) and high-field high-frequency electron paramagnetic resonance (HF-HFEPR). The spin Hamiltonian parameters for the three complexes were determined by analyzing the FDMRS spectra at different temperatures in zero applied magnetic field in an energy window between 0 and 40 cm(-1). The same parameters were determined from analysis of HF-HFEPR data measured at different frequencies (285, 380, and 475 GHz) and at 7 and 17 K. The spin Hamiltonian parameters D (axial) and E (rhombic) were calculated for the three complexes in the framework of the angular overlap model (AOM). The nature and magnitude of the magnetic anisotropy of the three complexes and the origin of the influence of the X atoms were analyzed by performing systematic calculations on model complexes. 相似文献
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Meiners J Scheibel MG Lemée-Cailleau MH Mason SA Boeddinghaus MB Fässler TF Herdtweck E Khusniyarov MM Schneider S 《Angewandte Chemie (International ed. in English)》2011,50(35):8184-8187
Squaring the circle: the novel dienamido pincer ligand N(CHCHPtBu(2))(2)(-) affords the isolation of the unusual square-planar iridium(II) and iridium(III) amido complexes [IrCl{N(CHCHPtBu(2))(2)}](n) (n=0 (1), +1 (2)). In contrast, the corresponding iridium(I) complex of the redox series (n=-1) is surprisingly unstable. The diamagnetism of 2 is attributed to strong N→Ir π donation. 相似文献
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