Pressure‐Induced Conversion of a Paramagnetic FeCo Complex into a Molecular Magnetic Switch with Tuneable Hysteresis

A key challenge in the design of magnetic molecular switches is to obtain bistability at room temperature. Here, we show that application of moderate pressure makes it possible to convert a paramagnetic Fe^III₂Co^II₂ square complex into a molecular switch exhibiting a full dia‐ to paramagnetic transition: Fe^IICo^III ? Fe^IIICo^II. Moreover, the complex follows a rare behavior: the higher the pressure, the broader the magnetic hysteresis. Thus, the application of an adequate pressure allows inducing a magnetic bistability at room temperature with predictable hysteresis width. The structural studies at different pressures suggest that the pressure‐enhanced bistability is due to the strengthening of intermolecular interactions upon pressure increase. An original microscopic Ising‐like model including pressure effects is developed to simulate this unprecedented behavior. Overall, this study shows that FeCo complexes could be very sensitive piezo switches with potential use as sensors.     

Charge‐induced modulation of magnetic interactions in a [2 × 2] metal‐organic grid complex

We investigate the magnetic state of a recently synthesized [2 × 2]‐metal‐organic grid complex as a function of its redox state. Our analysis of a phenomenological model for the relevant molecular orbitals reveals that additional electrons on the ligands can couple their spins via the bridging metal sites. We find that at certain stages of the reduction of the complex cation, a maximal total spin ground state of the complex (S = 3/2) can be stabilized by the Nagaoka mechanism. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

低维量子磁性和量子海森伯反铁磁体之有效场论

文章对低维量子磁性的基本问题和相关研究进展作了简单评述，强调了量子非线性Sigma模型在研究量子海森伯反铁磁体的低能物理方面所起的作用以及理论本身存在的疑难问题，并简单介绍了作者最近提出的克服这些疑难问题的一个新建议．     

Recent results on some columnar paramagnetic metallomesogens

The liquid crystalline and selected physical properties of some vanadyl and manganese(III)-porphyrin-TCNE complexes are discussed. These materials form linear chains from a magnetic point of view and columnar discotic LC phases. Some of the manganese complexes exhibit a bulk magnetic phase below ∼20 K. The discussed materials are studied by means of DSC, X-ray powder diffraction, dielectric spectroscopy, reversal current characterization and magnetic susceptibility measurements. A broader view on some physical properties of columnar paramagnetic metallomesogens is given.     

Computational Study of Endohedral IrSi9 + Isomers

Recent ion-trap experiments (See Ref. 2) have demonstrated the existence of endohedral transition metal–silicon clusters of composition MeSi_N ⁺ (Me = Hf, Ta, W, Re, Ir) with a characteristic number of Si cage atoms for each of the Me atom species. In this series, IrSi₉ ⁺ was the smallest of the reported systems. In view of its moderate size, this cluster appears particularly suitable for a systematic study of the bonding and stabilization mechanism prevailing in this newly discovered class of metal–Si_N units. We present a discussion of two highly symmetric pure Si₉ cage structures, namely a trigonal prism and a tricapped trigonal prism, and identify a stable IrSi₉ ⁺ (C_3h) unit with a cage structure intermediate between these two D _3h geometries. An additional endohedral IrSi₉ ⁺ species of lower symmetry (C_s), but higher stability than the C _3h alternative, is found from insertion of the Ir impurity into the C _2v ground-state geometry of Si₉. Comparison is made with an exohedral isomer derived from a substitutional structure based on Si₁₀. The role of electron transfer from the Si₉ cage to the Ir impurity in the stabilization of the endohedral complexes is emphasized.     

碘冉酸阴离子桥联双核铜（Ⅱ）配合物的合成与磁性

碘冉酸阴离子桥联双核铜（Ⅱ）配合物的合成与磁性孟祥军寇会忠邹国彰廖代正姜宗慧＊王耕霖（南开大学化学系天津３０００７１）关键词碘冉酸，Ｃｕ（Ⅱ），双核配合物，合成，磁性１９９６－０８－２０收稿，１９９６－１１－１８修回国家自然科学基金资助项目随着生物无...     

层状前体镁铁水滑石及磁性材料的制备及表征

本文提出了利用镁铁水滑石作为磁性材料前体再经高温焙烧制备尖晶石型铁氧体的思路,深入研究了水滑石的制备工艺及结构性能并初步探讨了其焙烧后的磁学性能。由共沉淀法合成了Mg/Fe摩尔比为2,3,4,6的镁铁水滑石,XRD结果表明随镁铁比增大、晶化温度的升高及晶化时间的延长,水滑石的晶体结构规整性增强;热重-差热结果显示镁铁水滑石的分解有两个过程,随着镁铁比增大,水滑石的热稳定性提高。高温焙烧后的镁铁水滑石具有较好的磁学性能。     

Crystal Structure and Magnetic Properties of Pyridyl-Substituted Nitronyl Nitroxides

X-ray crystal structure and cryomagnetic properties of three organic radicals, 2-(2-pyridyl)-4, 4,5,5-tetramethyl-4,5-dihydro-1-H-imidazol-1-oxyl-3-N-oxide(NIT-oPy) 1, 2-(3-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-l-H-imidazol-1-oxyl-3-N-oxide(NIT-mPy) 2 and 2-(6-methyl-2-pyridyl)-4,4,5,5-tetramethyl-4, 5-dihydro-1-H-imidazol-1-oxyl-3-N-oxide(NIT-6M-oPy) 3 were investigated. The crystal structures of compounds 1-3 show the same feature of a P2₁/c space group of a monoclinic system. Two crystallographically independent molecules were found in the crystals of compounds 1-3. The temperature dependence of magnetic susceptibility of compounds 1-3 revealed an intermolecular antiferromagnetic exchange interaction.     

Preparation,crystal structure,and magnetic properties of β-Li3TiF6 = LiLi(TiF6)(TiF6)2 – a double fluoride?

Purple colored single crystals of the β-modification of Li₃TiF₆ have been prepared by heating an appropriate mixture of LiF and TiF₃ at 820°C under an argon atmosphere. β-Li₃TiF₆ crystallizes in C2/c with a = 14.452(2) Å, b = 8.798(1) Å, c = 10.113(1) Å and β = 96.30(1)º. The structure is isotypic to β-Li₃VF₆ and contains isolated compressed TiF₆ octahedra (d_Ti–F = 1.91–2.01 Å). Magnetic properties of β-Li₃TiF₆ were studied and discussed. Band structure calculations and calculations of the Madelung part of the lattice energy, MAPLE, were performed to discuss the chemical bonding.     

The magnetochemistry of verdazyl radical-based materials

Stable organic radicals have received much attention as building blocks for the construction of molecular magnetic materials because they are readily functionalized using modern synthetic techniques. In this context, the nitroxide radical family has been the dominant class of radicals in molecular magnetochemistry. However, other stable radical systems have also been explored. One such example is the verdazyl family of radicals. Their high chemical stability and synthetic versatility make verdazyls one of the more attractive alternatives to nitroxides in molecular magnet design. This article reviews the magnetism of verdazyl-based systems, including through-bond coupling in polyradicals, coordination complexes and intermolecular interactions in the solid state.