A Chiral Molecular Based Metamagnet Prepared from Manganese Ions and a Chiral Triplet Organic Radical as a Bridging Ligand

Below 5.4 K the one-dimensional polymeric complex made up of manganese(II ) hexafluoroacetylacetonate units and bridging bisaminooxylbenzene diradicals (shown in the picture) behaves as a metamagnet. The R-helical chain not only contains an S-configured chiral carbon center, but also an R-configured C₂-symmetric chiral skeleton of the organic ligand.     

Two-Dimensional Nitroxide-Based Molecular Magnetic Materials

Manganese(II ) complexes of imidazolyl-substituted chelating nitronylnitroxides are characterized by a stereoselective arrangement of the metal centers and the ligands to give a honeycomblike layer structure (shown on the right). The magnetic properties at high temperature indicate the presence of a ferrimagnetic structure within the layers. At low temperatures, ferromagnetic ordering is observed.     

A Dendritic Macrocyclic Organic Polyradical with a Very High Spin of S=10

Designed as a ferromagnetically coupled spin pentamer , the macrocyclic polyradical 1 possesses an average spin of S=10 in the ground state. This is the highest spin quantum number that has yet been measured for an organic molecule. Ar=tBuC₆H₄.     

MnII[MnII(CN)4]—A Magnetic Interpenetrating Three-Dimensional Diamondlike Solid

Three-dimensional extended diamondlike networks containing four-coordinate metal centers can be constructed from [Mn^II(CN)₄]²⁻ building blocks. Besides the title compound, which was prepared and its magnetic properties studied in detail, other novel magnetic solids might be able to be synthesized.     

Four Discrete Transition Metal Complexes Involving Pyridyl‐substituted Nitronyl Nitroxide: Syntheses,Crystal Structures,and Magnetic Properties

Four discrete metal‐radical complexes, [Cu(p‐MePh‐COO)₂(NITpPy)₂] ( 1 ), [Ni(m‐MePhCOO)₂(NITpPy)₂(H₂O)₂] · (CH₃‐OH)₂ ( 2 ), [Mn(p‐MePhCOO)₂(NITpPy)₂(H₂O)₂] ( 3 ), and [Mn(m‐MePhCOO)₂(NITpPy)₂(H₂O)₂] ( 4 ) [NITpPy = 2‐(4‐pyridyl)‐4,4,5,5‐tetramethyl‐4,5‐dihydro‐1H‐imidazolyl‐1‐oxyl‐3‐oxide] were synthesized and characterized by elemental analyses, IR spectroscopy, PXRD, single‐crystal X‐ray diffraction, and magnetic susceptibility. For the four complexes, the crystal structural analyses indicate that the two radical ligands coordinated to the metal ions by the nitrogen atoms of the pyridine rings form three spin complexes, where toluates act as co‐ligands. Weak antiferromagnetic interactions [J_Cu–Rad = –6.75 cm^–1 ( 1 ), J_Co–Rad = –4.15 cm^–1 ( 2 ), J_Mn–Rad = –0.22 cm^–1 ( 3 ), and J_Mn–Rad = –3.74 cm^–1 ( 4 )] were observed, spin polarization mechanism and orbital symmetry are used to explain the magnetic coupling in these complexes.     

Synthesis,Structure and Magnetic Properties of a MnII Framework Assembled by Two Carboxylate Ligands

The 3D framework [Mn₃(CH₃COO)₂(HCOO)₄]_n · nDMF ( 1 ) was obtained from the assembly of Mn^II ions with acetate and the in‐situ generated formate ligands. It features Mn‐centered MnMn₄ tetrahedral nodes, each of which is linked to another four ones by sharing the apexes to form the 3D framework of 1 . Each of the acetate and formate ligands behaves as a syn‐syn:anti bridge to link two apical Mn^II ions and the central Mn^II ion. The magnetic measurement of 1 revealed the coexistence of spin‐canted antiferromagnetism and metamagnetism. It represents a typical example to synergistically use two kinds of carboxylate ligands to construct metal‐organic frameworks, as well as to tune the structure and magnetic properties of the aimed complex.     

Organic and Organometallic Molecular Magnetic Materials—Designer Magnets

Magnets composed of molecular species or polymers and prepared by relatively low-temperature organic synthetic methodologies are a focus of contemporary materials science research. The anticipated properties of such molecular-species-based magnetic materials, particularly in combination with other properties associated with molecules and polymers, may enable their use in future generations of electronic, magnetic, and/or photonic/photronic devices ranging from information storage and magnetic imaging to static and low-frequency magnetic shielding. A tutorial of typical magnetic behavior of molecular materials is presented. The three distinct models (intramolecular spin coupling through orthogonal orbitals in the same spatial region within a molecule/ion, intermolecular spin coupling through pairwise “configuration interaction” between spin-containing moieties, and dipole—dipole, through-space interactions) which enable the design of new molecular-based magnetic materials are discussed. To achieve the required spin couplings for bulk ferro- or ferrimagnetic behavior it is crucial to prepare materials with the necessary primary, secondary, and tertiary structures akin to proteins. Selected results from the worldwide effort aimed at preparing molecular-based magnetic materials by these mechanisms are described. Some organometallic solids comprised of linear chains of alternating metallocenium donors (D) and cyanocarbon acceptors (A) that is, …?D^?+ A^?? D^?+ A^??…?, exhibit cooperative magnetic phenomena. Bulk ferromagnetic behavior was first observed below the critical (Curie) temperature T_c of 4.8 K for [Fe^III(C₅Me₅)₂]^?+ [TCNE]^?? (Me = methyl; TCNE = tetracyanoethylene). Replacement of Fe^III with Mn^III leads to a ferromagnet with a T_c of 8.8 K in agreement with mean-field models developed for this class of materials. Replacement with Cr^III, however, leads to a ferromagnet with a T_c lowered to 3.65 K which is at variance with this model. Extension to the reaction of a vanadium(o) complex with TCNE leads to the isolation of a magnet with a T_c ≈ 400 K, which exceeds the thermal decomposition temperature of the material. This demonstrates that a magnetic material with a T_c substantially above room temperature is achievable in a molecule/organic/polymeric material. Finally, a new class of one-dimensional ferrimagnetic materials based on metalloporphins is discussed.     

Magnetic Field and Magnetic Isotope Effects upon Reactions of Heavy Atom-Centered Radicals

We present our recent studies on magnetic field effects (MFEs) observed in reactions of heavy atom-centered radicals such as Si-,P-, Ge-, and Sn-radicals with a ns-laser photolysis technique under magnetic fields of 0–10 T. Although the MFES of heavy atom-centered radicals are much smaller than those of C-radicals due to the spin-orbit interaction of heavy atoms, we have found appreciable MFEs in many reactions of such heavy atom-centered radicals. Comparing the MFES of C-radicals with those of heavy atom-centered ones, we have explained the MFEs of heavy atom-centered radicals in terms of the Δg and relaxation mechanisms. We have found that the separation between the MFES due to the Δg mechanism and those due to the relaxation one is possible with the enhancement of spin relaxation by the addition of a paramagnetic ion. We have also tried to enrich magnetic isotopes of heavy atoms with the magnetic isotope effect (MIE), using the reactions which show fairly large MFES. Recently, we have succeeded in enriching ⁷³Ge. This is the heaviest isotope which has so far been enriched with the MIE from samples of natural abundance.     

Synthesis,Structure and Magnetic Properties of dimeric Nickel(II) Benzoate with Pyridyl‐substituted Nitronyl Nitroxides

The novel heterospin complex [Ni₂(PhCOO)₄(NITpPy)₂]·2CH₃CN ( 1 ) was synthesized by the reaction of nickel benzoate and 2‐(4‐pyridyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide (NITpPy) in acetonitrile and dichloromethane solutions. The X‐ray structure determination shows that complex 1 consists of a symmetrical dimeric Ni^II benzoate paddle‐wheel core and pyridyl nitrogen atoms of radical ligands at the apical position, in addition, the temperature (2–300K) dependent magnetic susceptibility measurements indicate that 1 has antiferromagnetic behavior.     

Synthesis and Structure of a Hybrid Metal Phthalate Compound and Its Magnetic Property

The hybrid transition metal – alkali metal compound, [Ni(H₂O)₆·(μ‐H₂O)₂·K₂(phth)₄(H₂O)], (phth = phthalate) ( 1 ), was synthesized from nickel(II) nitrate, KOH and potassium hydrogen phthalate, and was isolated by crystallization. Single‐crystal X‐ray analysis revealed that 1 belongs to the monoclinic system, space group P2₁/c with a = 10.455(2) Å, b = 6.8670(14) Å, c = 29.704(6) Å, γ = 98.14(3)°, R₁ = 0.0585, wR₂ = 0.1503. In the title compound, [K₂(phth)₄]²⁺ units are bonded to water‐bridged Ni chains forming 2D lamellar‐like compounds.     

A Series of Transition Metal Coordination Polymers Bearing 1,4‐Phenylenediacetate

The reactions of transition metal salts or hydroxide with 1,4‐phenylenediacetic acid (H₂PDA) in the presence of ancillary ligands 4,4′‐bipyridine (4,4′‐bpy) or imidazole (Im) produced five coordination polymers with the empirical formula [M(PDA)(4,4′‐bpy)(H₂O)₂]_n [M = Mn ( 1 ), Ni ( 2 )], [Cu(PDA)(4,4′‐bpy)]_n · 2nH₂O ( 3 ), [Ni(PDA)(Im)₂(H₂O)₂]_n · nH₂O ( 4 ), and [Cu(PDA)(Im)₂]_n · 2nH₂O ( 5 ). Their structures were determined by single‐crystal X‐ray diffraction analyses. The isomorphous 1 and 2 present a two‐dimensional sheet constructed by two kinds of one‐dimensional chains of –Ni^II–PDA^2––Ni^II– and –Ni^II–4,4′‐bpy–Ni^II–. Compound 3 features dinuclear subunits, which are further connected by two PDA^2– ligands and two 4,4′‐bpy ligands along (001) and (011) directions, respectively, to build a two‐dimensional sheet with the topology (4².6⁷.8)(4².6) different from those of 1 and 2 . Both 4 and 5 show one‐dimensional chain structure. The difference of compound 4 and 5 is that the two carboxylato groups of PDA^2– in 4 adopt monodentate coordination modes, whereas the two carboxylato groups of PDA^2– in 5 chelate to the metal ions. Magnetic susceptibility data of 1 were measured. Magnetically, 1 presents a one‐dimensional chain with a weak antiferromagnetic interaction (J =–0.064 cm^–1) between the intrachain Mn^II atoms mediated by 4,4′‐bpy.     

Synthesis,Crystal Structure and Magnetic Properties of Rb2Mn3O4

Rb₂Mn₃O₄, which is the first rubidium oxomanganates(II), has been synthesized via the azide/nitrate route from a stoichiometric mixture of the precursors RbN₃, RbNO₃, and MnO, as well as from Rb₂O and MnO, through an all solid state reaction. Its crystal structure (C2/c, Z = 4, a = 1546.9(2) pm, b = 666.22(7) pm, c = 588.06(6) pm) consists of a 3D arrangement of edge‐ and corner‐sharing MnO₄ tetrahedra with rubidium filling the space between. Magnetic susceptibility measurements indicate a magnetic phase transition at 126 K. The magnetic response as a function of temperature is complex, indicating strong, partly frustrated magnetic exchange interactions.     

基于磁性金属有机框架化合物-适配体探针的氯霉素仿生比色传感器研究

构建了一种基于磁性金属有机框架化合物( MOF)-适配体探针的仿生比色传感器,用于食品中氯霉素残留分析。首先将氯霉素( CAP)的适配体标记到Fe3 O4磁珠上获得捕获探针,进而采用该适配体的互补链标记到铁基MOF( Fe-MOF)上作为纳米示踪剂( MOF-cDNA),将捕获探针和示踪剂杂交结合后,可获得铁磁性仿生复合探针。当氯霉素和此类探针孵育后,其与捕获探针上的适配体结合,将纳米示踪剂释放到溶液中,并经过磁分离后进入上清液。由于Fe-MOF具有过氧化物酶的性质,可以催化TMB-H2 O2系统显色,由此构建了一种高选择性的氯霉素比色传感器。在最佳反应条件下,本法对氯霉素的检测范围在0.001~10 ng/mL之间,最低检出限为0.3 pg/mL(S/N=3),实际样品的加标回收率为86.9%~93.5%,且不受其它抗生素干扰。用此方法检测牛奶样品中氯霉素的结果与商业化ELISA方法一致。此类无酶标记仿生探针具有高催化活性且成本较酶标探针大大降低;该分析方法利用磁分离简化了前处理步骤,可用于奶制品中氯霉素的快速灵敏分析。     

Synthesis,Structures and Magnetic Properties of Cyano‐bridged FeIII/MnIII Heterobimetallic 1D Chain Complexes

Using the tricyanometalate building block, (nBu₄N)[(Tp*)Fe(CN)₃] [Bu₄N⁺ = tetrabutylammonium cation; Tp*^– = hydrotris(3,5‐dimethylpyrazol‐1‐yl)borate], and bidentate Schiff base ligands, HL1 or HL2 {HL1 = 2‐[[(2‐phenylethyl)imino]methyl]phenol; HL2 = 4‐methoxy‐2‐[[(2‐phenylethyl)imino]methyl]phenol}, two heterobimetallic one‐dimensional (1D) chain complexes, [Mn(L1)₂Fe(Tp*)(CN)₃]_n ( 1 ) and [Mn(L2)₂Fe(Tp*)(CN)₃]_n ( 2 ), were synthesized. Single crystal X‐ray diffraction reveal the formation of neutral cyano‐bridged zigzag single chains in 1 and 2 . Magnetic studies demonstrate that both complexes show ferromagnetic interactions between central Fe^III and Mn^III atoms.     

氮氧自由基磁偶合体系的研究进展

介绍了含氮氧自由基磁偶合体系及金属－自由基类分子铁磁体的结构特点及其磁偶合机制.对其发展趋势和前景作一展望.     

Structure,Magnetic Properties and Catalase-like Activity of Asymmetric Dimanganese(III,III) Carboxylate Complexes with Salicylaldimine Ligands

The crystal structures, magnetic properties, and catalase-like activities of assymmetric dinuclear manganese(III, III) complexes, [Mn₂^{III, III}(spa)₂(μ-Me₃CCO₂)(Me₃CCO₂)(CH₃OH)] ( 1 ) and [Mn₂^{III, III}(vpa)₂(μ-Me₃CCO₂)(Me₃CCO₂)(CH₃OH)] ( 2 ), (H₂spa = 3-salicyclideneamino-1-propanol, H₂vpa = O-vanillin), were reported. The crystal structures of complexes 1 and 2 consist of the same discrete asymmetric coordination environment of dinuclear clusters, where the two manganese atoms are bridged by two alkoxo oxygens of the spa or vpa ligands and one bidentate carboxylate ion, whereas an additional oxygen atom of monodentate carboxylate coordinated to the first metal ion, and the second metal ion was coordinated by one oxygen atom of the solvent CH₃OH. Magnetic investigations (2–300 K) reveal an intramolecular antiferromagnetic spin exchange interaction with axial-field splittings: J = ?12.3 cm^?1 (D = ?0.10 cm^?1) and J = ?13.3 cm^?1 (D = ?0.15 cm^?1) for complexes 1 and 2 , respectively. The complexes should show catalase-like activity for H₂O₂ disproportionation in CH₃OH solvent at 25° with rate constants of k = 6.35 dm³moI^?1s^?1 and 6.20 dm³mol^?1s^?1 for complexes 1 and 2 , respectively.     

Isomorphous Catena Transition Metal Squarates [MII(C4O4)(dmso)2(OH2)2] (M = Co,Mn) and Magnetic Investigation into their Solid Solution M = CoxMn1–x

The crystal structures of two new isomorphous transition metal squarato complexes [M^II(C₄O₄)(dmso)₂(OH₂)₂] [M^II = Co^II (3d⁷), Mn^II (3d⁵); dmso = dimethylsulfoxide] and their magnetic properties are reported. The compounds feature two symmetrically independent chains, in which 1,3‐bridging squarato ligands connect cations in distorted octahedral surroundings of pseudo‐symmetry D_4h. From an equimolar solution of CoCl₂ · 6H₂O and MnCl₂ · 2H₂O a mixed‐metal coordination polymer crystallizes; it represents a solid solution and adopts the same structure as the corresponding monometallic compounds. The results of the diffraction experiment unambiguously proof the presence of both Co^II and Mn^II cations in either independent site albeit no precise ratio between the metal cations involved may be deduced from these findings. The difference in the magnetic properties between Co^II and Mn^II cations in the given ligand field has allowed us to establish their ratio in the solid solution more reliably than by X‐ray diffraction: Accounting for ligand field potential and spin‐orbit coupling of Co^II and regarding Mn^II as a pure spin system, the calculations yielded a fraction of 73 % Co^II in the mixed‐metal polymer. With respect to superexchange effects only weak antiferromagnetic interactions have been detected for the three coordination polymers.     

Heterometallic Trinuclear Complexes of Macrocyclic Oxamide: Synthesis,Crystal Structures,and Magnetic Properties

Two heterometallic trinuclear complexes of macrocyclic oxamide [Co(Ni L¹ )₂ L² (H₂O)] · 3H₂O ( 1 ) and [Mn(Ni L¹ )₂ L² (H₂O)] · 0.5CH₃OH · 1.5H₂O ( 2 ) (H₂ L¹ = 2,3‐dioxo‐5,6,14,15‐dibenzo‐1,4,8,12‐tetraazacyclopentadeca‐7,13‐diene, H₂ L² = 5‐sulfosalicylic acid) were synthesized and structurally characterized by elemental analysis, IR spectroscopy, and X‐ray diffraction. Single‐crystal X‐ray analyses reveal that both the complexes contain discrete neutral trinuclear [(Ni L¹ )₂M L² (H₂O)] (for 1 and 2 , M = Co, Mn, respectively) moieties. The structures of 1 and 2 have oxamido‐bridged trinuclear [M^IINi^II₂] units and consist of one‐dimensional chains formed by strong intermolecular hydrogen bonds. Furthermore, the magnetic properties of complex 1 were investigated and discussed in detail.     

Synthesis,Crystal Structures,and Magnetic Properties of Two Tetrahedral MnIIMnIII3 Complexes

Two tetranuclear manganese complexes, [NaMn^IIMn₃^III(μ₄‐O^2–)(HL)₃(SCN)₄] ( 1 ) and [NaMn^IIMn₃^III(μ₄‐O^2–)(HL)₃Cl₄][NaMn^IIMn₃^III(μ₄‐O^2–)(HL)₃Cl₃(H₂O)]ClO₄ · 3.5H₂O ( 2 ) were obtained from the reaction of manganese perchlorate with a quadridentate Schiff base ligand, 3‐(2‐hydroxybenzylideneamino)propane‐1, 2‐diol (H₃L) derived from condensation of 2‐hydroxybenzaldehyde with 3‐amino‐1, 2‐propanediol, as well as the coligand KSCN or NaCl under basic conditions. Single‐crystal X‐ray studies reveal that those two complexes all have a mixed‐valent tetrahedral core, which contains an apical Mn^II ion and three basal Mn^III ions situated in the [Mn₃(μ₄‐O^2–)]⁷⁺ equilateral triangle plane. Fitting of the magnetic susceptibility data to the theoretical χ_mT vs. T expression, revealed that the presence of only antiferromagnetic interactions between the central metal atoms in 1 , while both antiferromagnetic and ferromagnetic interactions are present in 2 .     

Two New Dinuclear MnII Cluster-based Metal-organic Frameworks: Syntheses,Crystal Structures,and Magnetic Properties

Two new dinuclear Mn^II cluster-based metal-organic frameworks, namely [Mn₂(L)(DMPU)₃]_n ( 1 ) and [Mn(L)_0.5(4,4'-bipy)_0.5(H₂O)]_n ( 2 ) (H₄L = biphenyl-3,3',5,5'-tetracarboxylic acid, DMPU = 1,3-dimethyltetrahydropyrimidin-2(1H)-one, 4,4'-bipy = 4,4'-bipyridine), were solvothermally synthesized and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, and magnetic studies. Compound 1 crystallizes in the monoclinic P2₁/n space group and displays a 3D framework with 4-connected crb/BCT -type topology, and compound 2 crystallizes in the monoclinic C2/c space group and displays a 3D framework with (4,6)-connected sqc422 -type topology. The magnetic studies of compounds 1 and 2 show the presence of weak antiferromagnetic interactions within the dinuclear Mn^II units.