Hisashi Ōkawa

Synthesis and magnetism of multi-dimensional cyanide-bridged bimetallic assemblies

Abstract The structures and magnetism of complex-based metal assemblies derived from [M(CN) 6 ] n − (M=Cr 3+ , Mn 3+ , Fe 3+ , Co 3+ , Fe 2+ ; n =3, 4) and coordinatively unsaturated [M A (L) x ] m + (M A =Mn 2+ , Ni 2+ , Cu 2+ , Mn 3+ , Fe 3+ ; L=polyamine ligand, salen 2− derivatives) are reviewed. The reaction of the constituents in different ratios, in the absence or presence of an appropriate cation or anion and by the change of ligand L provides multi-dimensional bimetallic assemblies of various networks extended through MCNM A NC linkages. The magnetic properties of the assemblies are discussed with respect to their network structures and M A /M combinations. These assemblies provide significant insights into magnetostructural correlation and design of magnetic materials.

d–f Heteronuclear complexes: synthesis, structures and physicochemical aspects

Abstract This article concerns d–f heteronuclear complexes, focusing on recent progress in their synthesis, stereochemistry, magnetism, some other physicochemical properties, and potential use as new materials.

Heterodinuclear metal complexes of phenol-based compartmental macrocycles

Abstract This article concerns recent progress in the derivation of heterodinuclear metal complexes from phenol-based compartmental macrocycles. Focus is placed on the design of unsymmetrical macrocycles whose two metal-binding sites, sharing two phenolic oxygens, are dissimilar with respect to the cavity size, coordination number, or the nature of donor atom. The stereochemistry, physicochemical properties and reactivities of the heterodinuclear complexes derived from these compartmental macrocycles are reviewed.

A Three-Dimensional Ferrimagnet with a High Magnetic Transition Temperature (TC) of 53 K Based on a Chiral Molecule

The transparent, double bridged-(R)-spiral three-dimensional polymeric complex K0.4 [Cr(CN)6 ][Mn(S)-pn](S)-pnH0.6 ((S)-pn=(S)-1,2-diaminopropane) has been synthesized and characterized (see X-ray structure; Cr: brown, Mn: red, C: gray, N: blue, K: green). Magnetic measurements on the complex show that the MnII and CrIII ions interact ferrimagnetically and magnetic transition occurs at 53 K (Curie temperature).

[Mn(en)]3[Cr(CN)6]2⋅4 H2O: A Three-Dimensional Dimetallic Ferrimagnet (Tc=69 K) with a Defective Cubane Unit

The first modified analogue of the AII3 [BIII (CN)6 ]2 ⋅x H2 O type of Prussian-Blue, the title compound, has a three-dimensional network structure extended by CrIII -CN-MnII linkages, which is based on a defective cubane unit comprising three Cr and four Mn ions (see structure), and shows ferrimagnetic ordering below 69 K.

Bimetallic dioxygen complexes derived from ‘end-off’ compartmental ligands

Abstract This article deals with recent progress in bimetallic dioxygen complexes derived from ‘end-off’ compartmental ligands having a phenolic or alcoholic oxygen as the endogenous bridge. Focus is placed on oxygenation of μ-phenoxo and μ-alkoxo bridged dimetal(II) complexes (metal(II)=Co(II), Fe(II), and Cu(II)) in view of the electronic and stereochemical nature of the compartmental ligands and bimetallic core structures.

Dicopper(II,II) and dicopper(I,II) complexes of a series of dinucleating macrocycles

The dinucleating macrocycles H2Lm,n containing two 2,6-di(aminomethyl)-4-methylphenol entities combined through two alkane chains, (CH2)m and (CH2)n, at the amine nitrogens have been prepared for the (m,n) sets (2,3), (2,4), (2,5), (3,3) and (3,4). The dinuclear copper(II) complexes having general formula [Cu2Lm,n][ClO4]2 have been prepared. Cryomagnetic investigations (80–300 K) reveal a strong antiferromagnetic spin-exchange between the copper(II) ions within each complex (J based on ℋ=–2JS1S2 in the range –345 to –255 cm–1). The cyclic voltammograms show two reduction couples, CuIICuII–CuICuII and CuICuII–CuICuI. The comproportionation constants Kcom for the mixed-valence CuICuII complexes have been determined electrochemically. The Kcom value increase in the order of the macrocycles (L2,3)2– < (L2,4)2– < (L2,5)2– and (L3,3)2– < (L3,4)2–. The CuICuII mixed-valence state is shown to be ‘spin-trapped’(Class I) for all the complexes based on ESR spectra.

Heterodinuclear Ni(II)M(II) (MPb, Mn, Fe, Co, Ni, Cu, Zn) complexes of a phenol-based dinucleating macrocycle with dissimilar 4- and 5-coordination sites

Abstract An Ni(II)Pb(II) complex [NiPb(L)](ClO 4 ) 2 ·H 2 O has been obtained by template reaction, where L 2− is the dinucleating macrocycle with two 2,6-di(iminomethyl)-4-methylphenolate entities combined by two lateral chains, (CH 2 ) 2− and (CH 2 ) 2 NH(CH 2 ) 2 , at the imino nitrogens. The Ni and Pb ions are located at the 4-coordination site with the chain (CH 2 ) 2  and the 5-coordination site with the chain (CH 2 ) 2 NH(CH 2 ) 2  of the macrocycle, respectively. By the use of the Ni(II)Pb(II) complex as the precursor a series of Ni(II)M(II) complexes [NiM(L)](ClO 4 ) 2 (MMn, Fe, Co, Ni, Cu, Zn) have been obtained in hydrated or solvated forms and characterized by IR, 1 H NMR and UVVis spectra, magnetic measurements, and cyclic voltammetry. Cyclic voltammograms of the Ni(II)M(II) complexes show the Ni(II)/Ni(I) reduction at −1.0 to −1.1 V versus SCE. The oxidation of the Fe(II) of the Ni(II)Fe(II) complex occurs at + 0.43 V whereas the oxidation of the Mn(II) of the Ni(II)Mn(II) complex and the Co(Il) of the Ni(II)Co(II) complex does not occur up to + 1.3 V.

A two-dimensional bimetallic assembly, [Ni(pn)2]2[Fe(CN)6]ClO4-2H2O, with a square structure

A bimetallic assembly, [Ni(pn)2]2[Fe(CN)6]ClO4·2H2O, has a two-dimensional square network structure, formed from Fe–CN–Ni(pn)2–NC–Fe linkages, and shows ferromagnetic ordering.

Structure and magnetism of a trinuclear CuII–GdIII–CuII complex derived from one-pot reaction with 2,6-di(acetoacetyl)pyridine

Abstract A unique 3d–4f mixed metal trinuclear compound, [Cu2Gd(L)2(NO3)2]NO3 (1; H2L=2,6-di(acetoacetyl)pyridine), is derived from a ‘one-pot’ reaction with H2L,Cu(NO3)2·3H2O and Gd(NO3)3·5H2O. Two L2− providing one central 2,6-diacylpyridine site and two terminal 1,3-diketonate sites hold two CuII ions and GdIII ion and form a linear Cu–Gd–Cu trinuclear core. This compound shows ferromagnetic interaction between CuII and GdIII.