A rectangular Ni-Fe cluster with unusual cyanide bridges

An asymmetric polycyanide iron complex, K2[Fe III(L1)(CN)4](MeOH) (HL1 = 2,2′-(1H-pyrazole-3,5- diyl)bis-pyridine), was synthesized and its complexation compatibility with nickel ions was examined. Two kinds of enantiomeric nickel-iron squares were obtained in the presence of a chiral bidentate capping ligand. The compounds display unusual cyanide bridge geometry and have ferromagnetic interactions between nickel and iron ions. © 2013 The Royal Society of Chemistry

ナノ磁性分子の合成と展開

科学研究費助成事業（科学研究費補助金）研究成果報告書：基盤研究(A) 平成15～17年度 課題番号：15205008原本の末尾には原著論文・学会発表論文等が掲載されていますが、著作権保護のため、つくばリポジトリでの公開はいたしません

Pre-programmed self-assembly of polynuclear clusters

This perspective reviews our recent efforts towards the self-assembly of polynuclear clusters with ditopic and tritopic multidentate ligands HL1 (2-phenyl-4,5-bis{6-(3,5-dimethylpyrazol-1-yl)pyrid-2-yl}-1H-imidazole) and H2L2 (2,6-bis-[5-(2-pyridinyl)-1H-pyrazole-3-yl]pyridine), both of which are planar and rigid molecules. HL1 was found to be an excellent support for tetranuclear [Fe4] complexes, [FeII4(L1)4](BF4)4 ([FeII4]) and [FeIII2FeII2(L1)4](BF4)6 ([FeIII2FeII2]). The homovalent system was found to exhibit multistep spin crossover (SCO), while the mixed-valence [FeIII2FeII2] complex shows wavelength-dependent tuneable light-induced excited spin state trapping (LIESST). For H2L2, a variety of polynuclear complexes were obtained through complexation with different transition metal ions, allowing the isolation of rings, grids, and helix structures. The rigidity of the ligand, difference in its coordination sites, and affinity for different metal ions dictates its coordination behaviour. In this paper, we summarise these ligand pre-programmed self-assembled clusters and their diverse physical properties

Oxalate-bridged heterometallic chains with monocationic dabco derivatives

A series of bimetallic oxalate-bridged one-dimensional chains with monocationic dabco derivatives, ({R-dabco}[M(solv)2][Cr(ox)3]·n(solv)) (dabco = 1,4-diazabicyclo[2.2.2]octane, H2ox = oxalate; R = H, M = Co (1); R = H, M = Zn (2); R = Bu, M = Co (3); R = Bu, M = Zn (4)) were synthesized. All compounds have one-dimensional zig-zag chain structures with R-dabco cations located between chains. Cryomagnetic studies reveal that 1 and 3 showed intrachain ferromagnetic interactions between Co(II) and Cr(III) ions and metamagnetic behaviour due to interchain antiferromagnetic interactions. Permittivity measurements on compound 4 indicate specific paraelectronic relaxation behaviour originating from the rotational motion of the dabco alkyl substituent

Torsion of an accessory spleen with situs inversus in a child

We present an unusual case of acute abdomen caused by torsion of an accessory spleen with situs inversus in a child. A three-year-old girl was admitted to our hospital with an 11-day history of right flank pain with fever. Her medical history revealed an operation of coarctation of the aorta with situs inversus at one month of age. Physical examination revealed a right flank mass and tenderness. A contrast-enhanced CT scan showed a normally enhanced small spleen in the right upper quadrant and a 7.0×6.0×3.5 cm, hypodense, marginal enhancing mass in　the right midabdomen adjacent to　the intestine. An emergency laparotomy was　decided upon with a preoperative diagnosis as an acute abdomen. During surgery, a mass was found under the greater omentum and two accessory spleens of 1.5 cm in diameter were found surrounding the main spleen. Several loops of bowel were adherent to the mass. The loops of bowel were dissected away. A pediculated congested mass was observed as an accessory spleen emerging from the greater omentum. The mass was twisted on its vascular pedicle and strangulated. The necrotic mass was removed and the postoperative recovery was uneventful. Though torsion of an accessory spleen is extremely rare, it should be considered in the differential diagnosis of acute abdomen in childhood

Carboxylic acid functionalized spin-crossover iron(II) grids for tunable switching and hybrid electrode fabrication

Two carboxyl-substituted iron(II) grids, one protonated, [Fe4(HL)4](BF4)4·4MeCN·AcOEt (1), and the other deprotonated, [Fe4(L)4]·DMSO·EtOH (2), where H2L = 4-{4,5-bis[6-(3,5-dimethylpyrazol-1-yl)pyrid-2-yl]-1H-imidazol-2-yl}benzoic acid, were synthesized. Single-crystal X-ray structure analyses reveal that both complexes have a tetranuclear [2 × 2] grid structure. 1 formed one-dimensional chains through intermolecular hydrogen bonds between the carboxylic acid units of neighboring grids, while 2 formed two-dimensional layers stabilized by π–π-stacking interactions. 1 showed spin transition between the 3HS-1LS and 1.5HS-2.5LS states around 200 K, while 2 showed spin-crossover between the 4LS and 2LS-2HS states above 300 K. A modified indium–tin oxide (ITO) electrode was fabricated by soaking the ITO in a solution of 1. The resultant electrode showed reversible redox waves attributed to the original redox processes of iron(II)/iron(III)

Cyanide-Bridged Decanuclear Cobalt–Iron Cage

A cyanide-bridged decanuclear [Co6Fe4] cluster was synthesized by a one-pot reaction, and the magnetic properties and electronic configuration were investigated. The complex displayed thermally controlled electron-transfer-coupled spin transition (ETCST) behavior between CoIII low-spin–NC–FeII low-spin and CoII high-spin–NC–FeIII low-spin states, as confirmed by single-crystal X-ray, magnetic, and Mössbauer analyses

Cobalt complexes with redox-active anthraquinone-type ligands

Three anthraquinone-type multidentate ligands, HL1-3 (HL = 2-R-1H-anthra[1,2-d]imidazole6,11-dione, HL1; R = (2-pyridyl), HL2; R = (4,6-dimethyl-2-pyridyl), HL3; R = (6-methoxy-2pyridyl)), were prepared, and their complexation behaviour were investigated. Three bis-chelate cobalt complexes with the formula [CoII(L1-3)2].n(solv.) (1, 2, and 3 for HL1, HL2, and HL3, respectively), in which the ligands adopted tridentate binding modes, were synthesized and structurally characterized by single-crystal X-ray analyses. Electrochemical studies of 1-3 in CH2Cl2 reveal three reversible redox waves, assigned to ligand and cobalt-centred processes. Further complexes were obtained in which HL1 adopted a bidentate binding mode, stabilising the mono-chelate [CoII(HL1)(NO3)2(DMF)2] (4) species and tris-chelate [CoIII(L1)3] (5) complex in which the cobalt ion was in its 3+ state. The electrochemical properties of complex 5 were investigated in DMF, and the Co(II)/Co(III) redox couple was found to have negatively shifted compared to that of complex 1, while the ligand-based processes became irreversible. Tridentate chelation is found to stabilise the anthraquinone ligands and unlocks their redox multi-stability

Investigating the transformations of polyoxoanions using mass spectrometry and molecular dynamics

The reactions of [γ-SiW10O36]8– represent one of the most important synthetic gateways into a vast array of polyoxotungstate chemistry. Herein, we set about exploring the transformation of the lacunary polyoxoanion [β2-SiW11O39]8– into [γ-SiW10O36]8– using high-resolution electrospray mass spectrometry, density functional theory, and molecular dynamics. We show that the reaction proceeds through an unexpected {SiW9} precursor capable of undertaking a direct β → γ isomerization via a rotational transformation. The remarkably low-energy transition state of this transformation could be identified through theoretical calculations. Moreover, we explore the significant role of the countercations for the first time in such studies. This combination of experimental and the theoretical studies can now be used to understand the complex chemical transformations of oxoanions, leading to the design of reactivity by structural control