Katsuya Inoue

Systematic syntheses of manganese derivatives with 2-pyridineethanol, 2-pyridinemethanol and 2,6-pyridinedimethanol as chelating ligands have been undertaken to produce [trans-Mn(C5H4N-2-CH2CH2OH)2Cl2] (1), [cis-Mn2(μ-Cl)2(Cl)2(C5H4N-2-CH2CH2OH)2(OH2)2] (2), [cis-Mn2(μ-Cl)2(C5H4N-2-CH2OH)4]Cl2 (3) and [MnCl{η3-C5H3N-2,6-(CH2OH)2}{η2-(C5H3N-2,6-(CH2OH)2)}]Cl (4). The complexes were characterized by single-crystal X-ray diffraction. The oxidation state of the manganese ions in these complexes is 2+. Magnetic data are measured down to 2 K; in dimer complexes (2 and 3) a significant antiferromagnetic interaction is observed between two manganese ions.

Systematic syntheses of manganese derivatives with 2-pyridineethanol, 2-pyridinemethanol and 2,6-pyridinedimethanol as chelating ligands have been undertaken to produce [trans-Mn(C5H4N-2-CH2CH2OH)2Cl2] (1), [cis-Mn2(μ-Cl)2(Cl)2(C5H4N-2-CH2CH2OH)2(OH2)2] (2), [cis-Mn2(μ-Cl)2(C5H4N-2-CH2OH)4]Cl2 (3) and [MnCl{η3-C5H3N-2,6-(CH2OH)2}{η2-(C5H3N-2,6-(CH2OH)2)}]Cl (4). The complexes were characterized by single-crystal X-ray diffraction. The oxidation state of the manganese ions in these complexes is 2+. Magnetic data are measured down to 2 K; in dimer complexes (2 and 3) a significant antiferromagnetic interaction is observed between two manganese ions.

In view of renewed interest in multiferroic for molecular systems, we re-examine the structural and magnetic properties of the potentially ferroic layered perovskite-like (CH3NH3)2[Fe(II)Cl4] due to its high-temperature magnetic ordering transition. The structures from several sets of diffraction data of single crystals consist of square-grid layers of corner-sharing FeCl6 octahedra and changes from the high-symmetry I4/mmm (T > 335 K) to the low-symmetry Pccn (T < 335 K). In the former the iron and bridging chlorine atoms are within the layer and the organic cations sit in the middle of each square grid, while in the latter the octahedra are tilted in pairs, two in and two out, progressively by up to 12° and the nitrogen atoms follow their motion to be nearer to the two-in pairs. Crystals are stable up to 450 K and display three phase transitions, two structural at 332 and 233 K and one magnetic at 95 K. The temperature dependences of the dc magnetization (zero-field and field-cooling modes) in different applied fields (10-10,000 Oe) on several aligned single crystals independently reveal a hidden-canted antiferromagnetic ground state of at least four sublattices and not the reported canted antiferromagnetic ground state. A metamagnetic critical field of only 200 Oe transforms it to a canted antiferromagnet. The estimated canting angle is 1.4° in zero field, and it folds to ca. 2.8° in a field of 50 kOe at 2 K. The easy axis is along 010, the hard axis is along 100, and the intermediate and canting axis is 001. Using the available extracted parameters the phase diagram has been constructed. This study provides evidence of a complex and intricate manifestation of the orientation, temperature, and field dependence of the interplay between anisotropy and coherent lengths, which would need further studies.

The synthesis, crystal structure, and electrical, optical, and magnetic properties of kappa-BETS2[Fe(III)(C2O4)Cl2], where BETS is bis(ethylenedithio)tetraselenafulvalene, are reported. The black plate crystals consist of parallel donor layers, two per unit cell, displaying a kappa-type packing of BETS(0.5+) within the bc plane and anionic magnetic chains, [Fe(C2O4)Cl2-]n, running along the c axis. It displays metallic behavior down to 4.2 K, and analysis of the optical reflectivity data gives unscreened plasma energies of 0.69 eV (E parallel c) and 0.40 eV (E perpendicular c). The optical anisotropy is larger than that seen for other kappa phases and is described well by transfer integrals obtained from extended Hückel calculations. However, the transfer integrals need to be scaled down uniformly by a factor of 1.21 to reproduce the absolute experimental plasma frequencies. The band structure consists of a one-dimensional (1D) band and a hole pocket, characteristics of kappa phases. The magnetic properties were modeled by the sum of a 1D antiferromagnetic chain contribution from the d spins of Fe3+, a temperature-independent paramagnetic contribution, and a Curie impurity term. At 4.5 K, there is a signature of long-range magnetic ordering to a canted-antiferromagnetic state in the zero-field-cooled-field-cooled magnetizations, and at 2 K, a small hysteresis loop is observed.

Dinuclear Cobalt (II) Complexes of an Acyclic Phenol-Based Dinucleating Ligand with Four Methoxyethyl Chelating Arms− First Magnetic Analyses in an Axially Distorted Octahedral Field-Sakiyama-2001-European Journal of Inorganic Chemistry-Wiley Online Library

We present the synthesis, characterization by IR, TGA, single crystal X-ray structure and magnetic properties of a novel series of NaCl-type frameworks of [AmineH(+)][Mn(HCOO)(3)(-)], templated by alkylammonium. The anionic NaCl-framework of [Mn(HCOO)(3)(-)] is counter-balanced by the alkylammonium cations located in the cavities of the framework to which they are hydrogen-bonded. The divalent manganese ions have octahedral geometry and are bridged by the formate in an anti-anti mode of coordination. All the compounds exhibit long-range antiferromagnetism below 9 K with a slight non-collinear arrangement of the moments. The canting, likely due to second-order spin-orbit coupling, is via a Dzyaloshinski-Moriya antisymmetric exchange mechanism. A spin-flop is observed in each case at fairly low fields. An orthorhombic to monoclinic transformation was observed for the protonated cyclotrimethyleneamine that is accompanied by localization of the cations into two positions below 240 K from the rapid dynamic flipping of the ring observed at room temperature.

A banana-shaped spin-crossover (SCO) cobalt(II) complex [Co(C16-terpy)2](BPh4)2 (1) with long alkyl chains, based on a terpyridine frame, was synthesized. Compound 1 exhibited very gradual SCO behavior and changes in the dielectric constant. This shows a way in which SCO materials can be used in electronic devices.

The A mixed crystal compound [Co(0.8)Fe(0.2)(C16-terpy)(2)](BF(4))(2) (2) (C16-terpy is 4'-hexadecyloxy-2,2':6',2''-terpyridine) with long alkyl chains was prepared by mixing [Co(C16-terpy)(2)](BF(4))(2) (1), which exhibits unique magnetic behavior, and the diamagnetic iron(II) compound [Fe(C16-terpy)(2)](BF(4))(2) (3). The long-lived metastable state in the frozen-in effect was observed for the first time in the spin-crossover cobalt(II) compound 2. Furthermore, relaxation from metastable to stable states was very slow because of a large structural transition resulting from the long alkyl chains.

The iron(II) compounds [Fe(3Cn-L)2(NCS)2] (n = 6 (1), n = 8 (2), n = 10 (3), n = 12 (4), n = 14 (5), n = 16 (6), n = 18 (7), n = 20 (8), and n = 22 (9)) were synthesized and their physical properties characterized by polarizing optical microscopy, differential scanning calorimetry, and powder X-ray analysis, where 3Cn-L denotes bidentate Schiff-base ligands formed from the corresponding aniline derivatives and pyridine-2-carboxyaldehyde. The iron(II) compounds 4-8 exhibited crystal to liquid-crystal transitions at 318, 334, 345, 338, and 347 K, respectively. Variable-temperature magnetic susceptibility measurements revealed that the compounds 1-9 exhibit spin-crossover behavior between the high-spin and low-spin states and a photoinduced spin transition from a low-spin state to a metastable high-spin state. Therefore, the iron(II) compounds 4-8 can undergo spin-crossover and photoinduced spin transition as well as have liquid-crystal properties all in a single molecule. Compounds with multifunctions are important in the development of molecular switches and optical materials.

Iron(II) compound [Fe(C16-terpy)2](BF4)2 (1) was synthesized, and exhibited liquid crystal transition. The thermodynamically stable form of the compound 1 is a low-spin state at room temperature. The single crystal X-ray analysis revealed the structure for iron(II) compound [Fe(C16-terpy)2](ClO4)2·acetone (1′). It can be understood that the low-spin iron(II) compound 1 is new type metallomesogen.