Published papers

Three tetrathiolate (tetrathiafulvalenetetrathiolate, ethylenetetrathiolate, and butadienetetrathiolate) nickel polymers are prepared. The polymers contain mixed valence Ni ions and are ESR active based on low-spin d8 Ni (III) species. Magnetic susceptibility measurement in the range of 30–60 K suggests and antiferromagnetic interaction between the Ni ions in the polymers. Below 30K a weak ferromagnetic interaction is observed. Chemically oxidized polymers are ESR inactive, while electrical conductivity is greatly enhanced.

UV Curing behavior of acrylate monomers in the presence of resol is described. A thin layer consist of resol, monofunctional acrylate (ECA), and hexafunctional acrylate (DPCA-60) gives the crosslinked polymer under UV irradiation. IR spectra of the crosslinked polymer show characteristic absorptions due to both resol and acrylate with a decrease of v C=C′ which indicates the additional polymerization takes place in this system. The curing is accelerated by addition of alkali, which suggests the phenol structure is active site for the polymerization. Among several kinds of alkali investigated, Ba(OH)2 is most effective for the reaction from the point of insoluble polymer yield. Consumption of acrylate double bond in the insoluble polymer ranges above 60% which decreases slowly with an increase in the DPCA-60 content due to steric hindrance. The synergic effect of Ba(OH)2 appears when it is added 0.1mol% for hydroxy group in the resol. UV irradiation leads to color change of the cured layer from pale yellow to reddish violet (λmax =570nm) with an appearance of ESR signal at g =2.004, which indicates the formation of phenoxy radical. The phenoxy radical formed in the resol should be an active site for UV polymerization of this system.

Poly[bis(2,6‐pyridinediylmethylidenenitrilohexamethylenenitrilomethylidene)iron sulfate] was said to be a ferromagnetic compound by earlier investigators. This polymer and its derivatives are carefully reprepared and their unusual magnetic property is reinvestigated spectroscopically. The counter anion species and spacer length of the polymers affect their coordination structure and magnetism. Mössbauer spectroscopy and x‐ray diffractometry on the polymers indicate that their unusual magnetic property is caused by the ferromagnetic iron oxide slightly formed in the polymers.

description is given of the synthesis of poly[(3,5-di-tert-butyl-4-hydroxyphenyl)acetylene] (1) and the formation of its polyradical. Experimental data shows that the absorption intensity of the oxidized 1 solution suggests formation of the phenoxy radical of 1 in high concentration and stays constant upon standing at room temperature over a day. This radical formation of 1 is in contrast to the radical formation of the corresponding low molecular phenols, e.g. 3,5-di-tert-butyl-4-hydroxycinnamate; the latter had been reported to give bisquinone methides irreversibly. The sterically crowded structure of 1 probably suppresses bond formation between unpaired electrons.

The complexation of gadolinium (Gd3+) ion with poly(methacrylic acid) and its copolymers was studied. Poly(methacrylic acid-co-acrylamide) formed the tris(carboxylate)-coordinate gadolinium complex with an extra large complex formation constant, while poly(methacrylic acid) formed the biscoordinate complex. Transparent and flexible film containing a high proportion of Gd ion was prepared by casting the complex solution of poly(methacrylic acid-co-methylacrylate). The complexed Gd ion was uniformly dispersed in the film and showed paramagnetism. The formation and magnetic properties of the polymer-Gd complexes are discussed in comparison with those of the corresponding iron complexes.

Complexation of some lanthanide ions with poly(methacry1ic acid) and its copolymers was studied by potentiometric titration. Poly [methacrylic acid-co-oligo(ethy1ene oxide)rnethacrylate] and poly(methacrylic acid-co-acrylamide) formed tris-carboxylate coordinate lanthanide complexes with large overall complexation constants, while poly(methacrylic acid)s and copolymer with higher content of the methacrylic acid residue formed bis-coordinate ones. It was concluded that the comonomer residues in the copolymer chains decreased the steric hindrance for the complexation and/or acted as co-coordinating groups of the carboxylic group to lanthanide ions. Very large positive and favorable entropy changes were observed for the complexation with poly(methacry1ic acid) and its copolymers. This contribution of thermodynamic parameters to the complexation was contrary to that for the analogous monomeric methacrylic acid complex and is assumed to be induced by dehydration of the polymers through the lanthanide ion complexation.

The complexation of europium ion(Eu3+) with poly(methacrylic acid) and its copolymers was studied. Poly(methacrylic acid-co-acrylamide) formed the tris(carboxylate)-coordinate Eu complex with extra large overall complexation constant while poly(methacrylic acid)s did the bis-coordinate ones. Transparent and flexible film containing much Eu ion was prepared by casting the complex solution of poly(methacrylic acid-co-methylacrylate). On exposure to ultraviolet light (393 nm), the film relatively strongly fluorescenced a red color based on the tris-coordinate and uniformly dispersed Eu complex.

メタクリル酸-メチルアクリラート共重合体 (モル組成比約1: 3) とガドリニウムの錯体は, 溶媒キャスト法によりGd3+含量が多く, かつ柔軟で透明な膜を与えた. 錯形成したGd3+は常磁性 (室温, 2.7×10-2emu mol-1) で, 膜中に均一に分散していることを確認した。

References Citations Metrics Reprints & Permissions Get access Abstract Nitronyl nitroxide derivatives bearing NH site, imidazolyl-2-nitronyl nitroxide (Im-NN), 4(5)-methyl-imidazolyl-2-nitronyl nitroxide (MeIm-NN), and benzimidazolyl-2-nitronyl nitroxide (BIm-NN) were synthesized, and were self-assembled by hydrogen bonding at NH site with nitrogen atom on imidazole ring or oxygen atom of nitroxide moiety. Ferromagnetic intermolecular interactions were observed in MeIm-NN and BIm-NN. The magnetic interaction can be rationally explained by McConnell model.

Absorption spectroscopy and circular dichroism (CD) have been used to characterize the DNA binding of [Fe(phen)3]2+, [Fe(phen)2(DIP)]2+ and [Fe(phen)(DIP)2]2+ where phen and DIP stand for 1,10-phenanthroline and 4,7-diphenyl-1,10-phenanthroline, respectively. Both [Fe(phen)3]2+ and [Fe(phen)2(DIP)]2+ bind weakly to calf thymus DNA (CT-DNA) in an electrostatic mode, while [Fe(phen)(DIP)2]2+ binds more strongly to CT-DNA, possibly in an intercalation mode. The hypochromicity, red shift and Kb increase in the order [Fe(phen)3]2+<[Fe(phen)2(DIP)]2+<[Fe(phen)(DIP)2]2+ in accordance with the increase in size and hydrophobicity of the iron(II) complexes. The thermodynamic parameters obtained suggest that the DNA binding of both [Fe(phen)3]2+ and [Fe(phen)2(DIP)]2+ is entropically driven, while that of [Fe(phen)(DIP)2]2+ is enthalpically driven. A strong CD spectrum in the UV and visible region develops upon addition of CT-DNA into the racemate solution of each iron(II) complex (Pfeiffer effect). This has revealed that a shift in diastereomeric inversion equilibrium takes place in the solution to yield an excess of one of the DNA-complex diastereomers. The striking resemblance of the CD spectral profiles to those of the pure Δ-enantiomer indicates that the Δ-enantiomer of the iron(II) complexes is preferentially bound to CT-DNA. The mechanism of the development of Pfeiffer CD is proposed on the basis of kinetic studies on the DNA binding of the racemic iron(II) complexes.

Two novel cationic porphyrins bearing five-membered rings at the meso-positions, meso-tetrakis(1,3-dimethylimidazolium-2-yl)porphyrin (H2TDMImP) and meso-tetrakis(1,2-dimethylpyrazolium-4-yl)porphyrin (H2TDMPzP), have been synthesized. These two compounds interact with calf thymus DNA (CTDNA) in different binding modes from that of meso-tetrakis(N-methylpyridinium-4-yl)porphyrin (H2TMPyP). H2TDMImP outside binds to the minor groove of CTDNA while H2TDMPzP intercalates into CTDNA. These two novel cationic porphyrins strongly bind to CTDNA even at high ionic strength and the binding constant of H2TDMPzP to CTDNA is comparable to that of H2TMPyP. The binding of H2TDMImP to CTDNA is enthalpically driven. The favorable free energy changes in binding of H2TDMPzP to CTDNA come from the large negative enthalpy changes accompanied by small positive entropy changes.

The self-associated structures of two noble meso-(monopyrazolyltritolyl)porphyrins synthesized via their NH-protected precursors have been studied by 1H NMR, FT-IR and ESI MS measurements; meso-(pyrazol-4-yl)porphyrin and meso-(3,5-dimethylpyrazol-4-yl)porphyrin form a dimer and a tetramer, respectively, in solution due to intermolecular hydrogen bonding between pyrazole units.

Two types of mixed-ligand complexes, i.e. [M(phen)2 (dip)]2+ and [M(phen)(dip)2]2+ (M = iron(II) and nickel(II); phen = 1,10-phenanthroline and dip = 4,7-diphenyl-1,10-phenanthroline) have been prepared from their related tris-complexes, [M(phen)3]2+ by ligand substitution, and isolated by semi-preparative HPLC. Elemental and chromatographic analyses confirm the purity of the isolated complexes while u.v./vis and i.r. spectra were used to identify and characterize them. 1H-n.m.r. and room temperature Mössbauer spectra of the iron(III) complexes were also measured and the results are discussed. In addition, our preliminary results on hypochromicity in the MLCT band and circular dihroism (CD) emerging in the u.v./vis region upon addition of CT(calf thymus)-DNA to the racemic complexes indicated that the iron(II) mixed-ligand complexes interact with CT-DNA.

4‐[(3,5‐Di‐tert‐butyl‐4‐hydroxyphenyl)(3,5‐di‐tert‐butyl‐4‐oxo‐cyclohexa‐ 2,5‐dienylidene)methyl]styrene (abbreviated as (p‐vinylphenyl)hydrogalvinoxyl) was polymerized using AIBN as an initiator to give a bright yellow polymer with Mw = 3.2 × 104. The polymer was oxidized to give the corresponding polyradical derivative, whose spin concentration could be increased up to about 70 mol % depending on oxidative conditions. ESR signal line‐width in the solid state was greatly increased below 200 K for the polyradical with a high spin concentration (> 50 mol %). The magnetization and magnetic susceptibility indicated weak antiferromagnetic interaction among the radical sites.

Temperature dependence measurements of magnetic susceptibilities and low-temperature magnetization of tetradentate Schiff base–oxovanadium(IV) complexes, [VO(salpn)] (1), [VO(5-NO2salen)]·2H2O (2), and [VO(3-EtOsal-meso-stien)]·H2O (3) were carried out. Orange 1 and brown 2, which take linear chain structures (VO⋯VO⋯) in the solid state, show dominant ferromagnetic intermolecular interactions (J=+5.2 and +5.7 cm−1, respectively) on which very weak antiferromagnetic interactions between the chains are superimposed. However, green 3, which takes a fairly elongated linear chain structure (V⋯O distance: 4.060(2) Å) in the crystal, shows an isolated doublet state.

N-H水素結合部位を有するニトロニルニトロキシドラジカルの磁気特性に対するイミダゾール導入置換基の影響を報告した。（９頁）

Fe[Fe(CN)5NO]・xH2Oに光照射した際に観測される磁気特性の変化を報告した.

A long-living metastable state is produced in FeII[Fe(CN)5NO]·xH2O by an irradiation of 488 nm light at 200 K. A strong near-infrared band of about 10000 cm−1 and a ν(CN) band at 2070 cm−1 that newly appear in the metastable state point to development of the mixed-valence state analogous to Prussian blue. An iron-to-nitrosyl charge transfer in pentacyanonitrosylferrate(2−), [Fe(CN)5NO]2−, explains the formation of the mixed-valence state, because the charge transfer causes a pair of iron(II) and iron(III) atoms bridged by CN− that has the same local structure as Prussian blue. In addition to the formation of the metastable state, the prolonged irradiation causes an irreversible change of FeII[Fe(CN)5NO]·xH2O and leads to the formation of a photoproduct. The photoproduct also has infrared spectra characteristic of the mixed-valence state. Mössbauer spectra of the photoproduct show that a low-spin iron ion in pentacyanonitrosylferrate(2−) is divalent and a high-spin iron outside of pentacyanonitrosylferrate(2−) is trivalent. Therefore, the charge-transfer between the two non-equivalent iron ions is thought to follow the intra-molecular charge transfer in pentacyanonitrosylferrate(2−).

The chromatographic behaviour of negatively-charged iron(II) and copper(II) chelates with 4,7-diphenyl-1,10-phenanthroline (bathophenanthroline) disulfonate (BPS) on a reversed-phase Inertsil ODS-2 column was studied by using methanol–water (60:40, v/v) containing 0.02 M tetramethylammonium bromide (TMAB) and 0.025 M tris(hydroxymethyl)aminomethane (Tris)–HCl at pH 7.5 as a mobile phase. The possibility that the hydrophilic Tris–HCl buffer also serves as a counter ion together with TMAB was briefly discussed. Chromatographic parameters influencing the separation of the chelates were optimized. The method was successfully applied to indirectly determine iron(II) and iron(III) contents in natural water. Nickel(II) ion and possibly organic pollutants interfere with the present method.

Three imidazole derivatives with stable radical groups at 2-position were prepared and their magnetic property were characterized. The effect of NH hydrogen bonding site was also discussed.