研究者詳細 - 奥野　恒久

論文 - 奥野　恒久

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1-Ethyl-4-(1H-naphtho[1,8-de][1,3,2]diazaborinin -2(3H)-yl)pyridin-1-ium Iodide monohydrate

橋本柊, 三木慎太朗, 奥野恒久 (担当区分：最終著者,　責任著者 )

IUCrdata 9 x240369 2024年03月 [査読有り]

1-Ethyl-4-(1H-naphtho[1,8-de][1,3,2]diazaborinin -2(3H)-yl)pyridin-1-ium Iodide

橋本柊, 奥野恒久 (担当区分：最終著者,　責任著者 )

IUCrdata 9 x240362 2024年03月 [査読有り]

2,3,4,5,6-ペンタクロロ安息香酸水和物結晶:結晶学的そして計算科学的な乱れた水素結合系の構造解析

奥野恒久, 尾﨑康次, 東野伊央里 (担当区分：筆頭著者,　責任著者 )

Journal of Molecular Structure 1276 134815 2023年01月 [査読有り]

10-[(4-Nitrophenyl)ethynyl]-10H-phenothiazine

奥野恒久, 土居生枝 (担当区分：筆頭著者,　責任著者 )

IUCrData 7 x220942 2022年09月 [査読有り]

DOI

N-Phenyl-N-[(E)-2-(4,4,5,5-tetramethyl-1,3,2- dioxaborolan-2-yl)ethenyl]aniline

畑山友希, 赤木一登, 奥野恒久 (担当区分：最終著者,　責任著者 )

IUCrData 7 x220083 - x220083 2022年01月 [査読有り]

9-[(Z)-2-(4,4,5,5-テトラメチル-1,3,2-ジオキサボロラン-2-イル)エテニル]-9H-カルバゾールの結晶構造

金川真侑, 赤木一登, 奥野恒久 (担当区分：最終著者,　責任著者 )

IUCrデータ ( International Union of Crystallography (IUCr) ) 6 ( 2 ) x210142 - x210142 2021年02月 [査読有り]

The title compound, C20H22BNO2, has a polarized π-system due to resonance between N—C(H)=C(H)—B and ionic N+=C(H)—C(H)=B− canonical structures. The dihedral angles between the ethenyl plane (r.m.s. deviation for C2H2 = 0.0333 Å) with the ethenyl-<italic>C</italic>(NC2-pyrrole) plane (r.m.s. deviation CNC2 0.0423 Å) and the ethenyl-C(BO2-1,3,2-dioxaborolane) plane (r.m.s. deviation BCO2 0.0082 Å) are 45.86 (8) and 37.47 (8)°, respectively, and are greater than those found for the previously reported <italic>E</italic>-isomer [Hatayama & Okuno (2012) <italic>Acta Cryst.</italic> E<bold>68</bold>, o84]. In comparison with the <italic>E</italic>-isomer, the reduced planarity of <italic>Z</italic>-isomer results in a decrease of the contribution of the N+=C(H)—C(H)=B− canonical structure.

DOI

N-(6-(ジフェニルアミノ)ピリジン-2-イル)-N-フェニルアセタミドの結晶構造とDFT計算

奥田朋花, 梅園悟, 奥野恒久 (担当区分：最終著者,　責任著者 )

Journal of Structural Chemistry ( NIIC SB RAS ) 60 ( 3 ) C.412 - C.414 2019年05月 [査読有り]

DOI

N-[5-(ジフェニルアミノ)ペンタ-2,4-ジイン-1-イル]ベンズアミドの結晶多形

尾﨑康次, 奥野恒久 (担当区分：最終著者,　責任著者 )

IUCrデータ ( International Union of Crystallography (IUCr) ) 4 ( 4 ) x190371 - x190371 2019年03月 [査読有り]

The title compound, C24H18N2O, was been described previously in the space group <italic>P</italic>21/<italic>c</italic> with <italic>Z</italic> = 4 [Kawashima & Okuno (2017). <italic>IUCrData</italic>, <bold>2</bold>, x170277]. The current <italic>P</italic>\overline{1} polymorph was obtained from a chloroform–ethanol solution. The molecular structure in this polymorph is slightly different from the previously reported structure, with different dihedral angles of the two <italic>N</italic>-phenyl groups to the ynamine plane; these are 79.99 (11) and 12.09 (11)° in the polymorph reported here. The molecules form dimers through four C—H...π interactions. Furthermore, in this polymorph, the molecules stack along the <italic>a</italic> axis to form a molecular arrangement that would be suitable to promote the solid-state polymerization of diacetylenes.

DOI

3-(4-ヨードフェニル)ペンタンジニトリルの結晶構造

南保勇輝, 奥野恒久 (担当区分：最終著者,　責任著者 )

IUCrデータ ( International Union of Crystallography (IUCr) ) 4 ( 2 ) x190282 - x190282 2019年02月 [査読有り]

DOI

2,3,4,5,6-ペンタクロロ安息香酸の結晶多形と量子化学計算

尾﨑康次, 奥野恒久 (担当区分：最終著者 )

Journal of Molecular Structure ( Elsevier BV ) 1173 959 - 963 2018年12月 [査読有り]

DOI

6-[(フェニルカルバモイル)オキシ]ヘキサ-2,4-ジイン-1-イルイソニコチン酸エステルの結晶多形

山本稜, 南翔馬, 奥野恒久 (担当区分：最終著者,　責任著者 )

Acta Crystallographica Section C Structural Chemistry ( International Union of Crystallography (IUCr) ) 74 ( 8 ) 876 - 881 2018年08月 [査読有り]

The title compound, C19H14N2O4, was found to have two crystal polymorphs, in which the molecular structures of the diacetylenic compound are broadly similar. The main structural difference between the polymorphs concerns the intermolecular hydrogen-bonding motifs adopted, namely a one-dimensional zigzag polymer linked by N—H...N(py) (py is pyridine) interactions in polymorph I and a centrosymmetric dimeric motif formed by N—H...O=C interactions in polymorph II. The diacetylene cores of the molecules stack along the <italic>a</italic> and <italic>b</italic> axes in polymorphs I and II, respectively. It was found that only the molecular arrangement in polymorph II satisfies Baughman's criterion to afford polydiacetylenes (PDAs) by thermal annealing or irradiation with light. This predicted polymerization activity was confirmed by experiment.

DOI

5-[フェニル(ピリジン-4-イル)アミノ]ペンタ-2,4-ジイン-1-オールの結晶構造

梅園悟, 奥野恒久 (担当区分：最終著者,　責任著者 )

IUCrデータ ( International Union of Crystallography (IUCr) ) 3 ( 3 ) x180454 - x180454 2018年03月 [査読有り]

In the title diacetylene derivative, C16H12N2O, the amino plane makes dihedral angles of 3.90 (4) and 60.53 (4)°, respectively, with the pyridyl and phenyl rings, indicating that an electron-deficient pyridyl ring makes better conjugation with a lone pair of the amino nitrogen atom. In the crystal, molecules form inversion dimers<italic>via</italic>pairs of hydrogen bonds between the hydroxy and pyridyl groups, with an O...N distance of 2.7765 (16) Å. The dimers stack along the<italic>a</italic>axis, but the title compound shows little solid-state polymerization reactivity.

DOI

10-[1,1-ジクロロ-4-(トリメチルシリル)ブタ-1-エン-3-イン-2-イル]-10H-フェノチアジンの結晶構造

梅園悟, 奥野恒久 (担当区分：最終著者,　責任著者 )

IUCrデータ ( International Union of Crystallography (IUCr) ) 3 ( 2 ) x180232 - x180232 2018年02月 [査読有り]

The title compound, C19H17Cl2NSSi, is an enamine derivative, in which the N atom adopts a shallow trigonal–pyramidal geometry [displacement from the plane of its attached C atoms = 0.1383 (18) Å]. The dihedral angle between the plane through the three amino carbon atoms and the vinyl group is 89.47 (7)°. The phenothiazine unit has a butterfly structure and the central six-membered ring adopts a boat conformation. The fold angle between the benzene rings is 28.52 (7)°. The crystal structure features weak C<italic>sp</italic>3—H...Cl hydrogen bonds, H...S contacts and π–π stacking interactions between phenothiazine units.

DOI

アセチレン基を置換基とする新規TCNQ誘導体の配座多形結晶

飯田勇輝, 片岡誠, 奥野恒久 (担当区分：最終著者,　責任著者 )

Journal of Molecular Structure ( Elsevier BV ) 1152 261 - 265 2018年01月 [査読有り]

DOI

(E)-10-(1,2-dihalovinyl)-10H-phenothiazine 5,5-dioxidesにおけるハロゲン結合の系統的研究

梅園悟, 奥野恒久 (担当区分：最終著者,　責任著者 )

Journal of Molecular Structure ( Elsevier BV ) 1147 636 - 642 2017年11月 [査読有り]

DOI

N2,N2,N6,N6-テトラフェニルピリジン-2,6-ジアミンの結晶構造

三木慎太朗, 梅園悟, 奥野恒久 (担当区分：最終著者,　責任著者 )

IUCrデータ ( International Union of Crystallography (IUCr) ) 2 ( 4 ) x170521 - x170521 2017年04月 [査読有り]

DOI

N-[5-(ジフェニルアミノ)ペンタ-2,4-ジイン-1-イル]ベンズアミドの結晶構造

川島拓也, 奥野恒久 (担当区分：責任著者 )

IUCrデータ ( International Union of Crystallography (IUCr) ) 2 ( 2 ) x170277 - x170277 2017年02月

DOI

ニコチン酸エステル骨格を含むジアセチレン誘導体の合成・結晶構造・DFT計算

南翔馬, 岩橋宏和, 奥野恒久 (担当区分：最終著者,　責任著者 )

Journal of Molecular Structure ( Elsevier BV ) 1108 438 - 443 2016年03月 [査読有り]

DOI

9-(1,3-ブタジイニル)カルバゾール誘導体の結晶多形と固相重合反応

田端秀行, 桑本和典, 奥野恒久 (担当区分：最終著者,　責任著者 )

Journal of Molecular Structure ( Elsevier BV ) 1106 452 - 459 2016年02月 [査読有り]

DOI

N-フェニル-N-(ピリジン-4-イル)アセタミドの結晶構造とDFT計算

梅園悟, 奥野恒久 (担当区分：最終著者,　責任著者 )

J. Struct. Chem 56 472 - 474 2015年07月 [査読有り]

(E)-10-(1,2-dibromoprop-1-en-1-yl)-10H-phenothiazineの特異な平面構造

梅園悟、奥野恒久 (担当区分：最終著者,　責任著者 )

J. Mol. Struct. 1084 172 - 176 2014年12月 [査読有り]

4-(prop-2-yn-1-yloxy)benzinitrileの結晶構造

M. Kanagawa, T. Okuno (担当区分：最終著者,　責任著者 )

Acta Cryst. E 71 o97 - o98 2014年11月 [査読有り]

N-phenylpyridin-4-amineの2種類の結晶多形

奥野恒久, 梅園悟 (担当区分：筆頭著者,　責任著者 )

J. Mol. Struct. 1064 88 - 93 2014年02月 [査読有り]

Transannular S···N interactions in 10-ethynyl-10H-phenothiazine 5-oxide and 5,5-dioxide

S. Umezono, T. Okuno

Acta Cryst. C 69 1553 - 1556 2013年09月 [査読有り]

Crystal structure and anomalous chemical shift 10-(prop-1-yn-1-yl)-10H-phenothiazine 5,5-dioxide: Intramolecular S···N transannular effect

梅園悟, 奥野恒久 (担当区分：最終著者,　責任著者 )

J. Mol. Struct. 1049 293 - 298 2013年06月 [査読有り]

Preparations, crystal polymorphs and DFT calculations of N1,N1,N4,N4-tetraphenylbuta-1,3-diyne-1,4-diamine

Y. Tokutome, T. Okuno

J. Mol. Struct. 1049 293 - 298 2013年05月 [査読有り]

2-Methyl-3-(10H-phenothiazin-10-yl)-buta-1,3-diene-1,1,4,4-tetracarbonitrileの結晶構造

奥野恒久, 岩橋宏和 (担当区分：筆頭著者,　責任著者 )

Acta Cryst. E 69 o665 - o665 2013年04月 [査読有り]

1,3-bis(pentafluorophenyl)ureaの新しい結晶多形

奥野恒久 (担当区分：筆頭著者,　責任著者 )

Acta Cryst. E 69 o608 - o608 2013年03月 [査読有り]

(Z)-9-(1,2-Dichlorovinyl)-9H-carbazoleの結晶構造

鵜飼美帆, 田端秀行, 奥野恒久 (担当区分：最終著者,　責任著者 )

Acta Cryst. E 69 o555 - o555 2013年03月 [査読有り]

2-(2,5-Dimethyphenoxy)ethanolの結晶構造

鵜飼美帆, 奥野恒久 (担当区分：最終著者,　責任著者 )

Acta Cryst. E 69 o456 - o456 2013年02月 [査読有り]

N,N-Bis(4-nitrophenyl)acetamideの結晶構造

K. Nanaura, T. Okuno (担当区分：最終著者,　責任著者 )

Acta Cryst. E 69 o457 - o457 2013年02月 [査読有り]

N-(2,4-dinitrophenyl)-2,4-dinitroanilineの単斜晶系の多形

徳留由衣, 奥野恒久 (担当区分：最終著者 )

Acta Cryst. E 69 o152 - o152 2013年01月 [査読有り]

4-(prop-2-yn-1-yloxy)benzaldehydeの結晶構造

土居生枝, 奥野恒久 (担当区分：最終著者,　責任著者 )

Acta Cryst. E 69 o125 - o125 2013年01月 [査読有り]

1-(10H-phenothiazin-10-yl)ethenoneの結晶構造

徳永枝里, 奥野恒久 (担当区分：最終著者,　責任著者 )

Acta Cryst. E 68 o3369 - o3369 2012年11月 [査読有り]

10-(prop-1-yn-1-yl)-10H-phenothiazineの結晶構造

梅園悟, 奥野恒久 (担当区分：最終著者,　責任著者 )

Acta Cryst. E 68 o2790 - o2790 2012年08月 [査読有り]

10-(1,2,2-Trichlorovinyl)-10H-phenothiazine 5,5-dioxideの結晶構造

田端秀行, 奥野恒久 (担当区分：最終著者,　責任著者 )

Acta Cryst. E 68 o2519 - o2519 2012年07月 [査読有り]

Preparations, crystal structures and DFT calculations of novel diacetylenes incorporating ynamine moieties

徳留由衣, 久保夏希, 奥野恒久 (担当区分：最終著者,　責任著者 )

J. Mol. Struct. 1029 135 - 141 2012年07月 [査読有り]

10-(6-Hydroxyhexa-2,4-diyn-1-yl)-10H-phenothiazine 5-oxideの結晶構造

田端秀行, 奥野恒久 (担当区分：最終著者,　責任著者 )

Acta Cryst. E 68 o2214 - o2214 2012年06月 [査読有り]

9-Ethynyl-9H-carbazoleの結晶構造

田端秀行, 奥野恒久 (担当区分：最終著者 )

Acta Cryst. E 68 o828 - o828 2012年02月 [査読有り]

9-[(E)-2-4,4,5,5-Tetramethy-1,3,2-dioxaborolan-2-yl)ethenyl]-9H-carbazole

畑山友希, 奥野恒久 (担当区分：最終著者,　責任著者 )

Acta Cryst. E 68 o84 - o84 2012年01月 [査読有り]

Preparation and properties of two-legged ladder polymers based on polydiacetylenes

Hideyuki Tabata, Hiroaki Tokoyama, Hideo Yamakado, Tsunehisa Okuno

JOURNAL OF MATERIALS CHEMISTRY ( ROYAL SOC CHEMISTRY ) 22 ( 1 ) 115 - 122 2012年 [査読有り]

A novel diacetylene derivative, N,N'-bis[5-(3-tolylaminocarbonyloxy)-1,3-pentadiynyl]-N,N'-diphenyl-1,4- phenylenediamine (1), was prepared, where two diacetylene groups were connected by a 1,4-phenylenediamine moiety. The molecules stacked one-dimensionally and showed solid-state-polymerization reactivity above 80 degrees C. The decay of the monomers at 100 degrees C proceeded gradually without a marked induction period and was fully completed after 400 h. The obtained polymer was a crystalline solid judged by powder X-ray diffraction (PXRD) patterns and SEM imaging. The conjugated pi-system of the obtained polymer was classified as a two-legged conjugated ladder. The polymer showed a broad absorption from the visible to the near IR region, indicating a decrease in the optical band gap of ca. 1.0 eV, because of the expansion of the pi-conjugated system from a one-dimensional system to a ladder. The ladder polymer showed high conductivity after I(2) doping from sigma(293K) = 5 x 10(-12) S cm(-1) to 1.2 x 10(-5) S cm(-1). The conductivity depended heavily on the pressure of iodine and reached s373K 2.3 x 10(-1) S cm(-1). The activation energy of the ladder polymer was also estimated as 360 meV.

DOI

N1,N4-Diethynyl-N1,N4-diphenylbenzene-1,4-diamineの結晶構造

田端秀行, 奥野恒久

Acta Cryst. E 67 o3169 - o3169 2011年10月 [査読有り]

Two polymorphs of N1,N4-bis(5-hydroxypenta-1,3-diynyl)-N1,N4-diphenylbenzene-1,4-diamine

田端秀行, 久保夏希, 奥野恒久 (担当区分：最終著者,　責任著者 )

Acta Cryst. C 67 492 - 495 2011年09月 [査読有り]

Solid State Polymerization of Diacetylenes with Amide Groups

奥野恒久, 山根健太郎, D. J. Sandman

Mol. Cryst. Liq. Cryst. 456 33 - 44 2006年07月 [査読有り]

Solid state polymerization of diacetylenes incorporating ynamine moiety

奥野恒久, 池田智, 久保夏希, D. J. Sandman (担当区分：筆頭著者,　責任著者 )

MOLECULAR CRYSTALS AND LIQUID CRYSTALS ( TAYLOR & FRANCIS LTD ) 456 35 - 44 2006年 [査読有り]

Novel ynamine. compounds, 5-hydroxy-1-(phenothiazine-10-yl)-1,3-pentadiyne (1), its S-oxide (2) and S-dioxide (3), were prepared. Compound 2 was found to show thermal reactivity to give polydiacetylene, however 1 and 3 did not show any reactivity. Compound 2 stacks along the c axis, forming a columnar structure. The condition of molecular arrangement satisfied Baughman's criterion. Significant intermolecular contact between the oxygen atoms of sulfoxide groups and the adjacent sulfur atoms was recognized.

DOI

Crystal structures and magnetic properties of (m- or p-MPYNN)(2) Ni-II(tdaS)(2)

T Okuno, K Kuwamoto, W Fujita, K Awaga, W Nakanishi

POLYHEDRON ( PERGAMON-ELSEVIER SCIENCE LTD ) 22 ( 14-17 ) 2311 - 2315 2003年07月 [査読有り]

Novel Ni-II(tdaS)(2) complexes, (m - or p-MPYNN)(2)Ni(tdas)(2) (MPYNN = N-methylpyridinium alpha-nitronyl nitroxide and tdas = 1,2,5-thiadiazole-3,4-dithiolate), were prepared. The Ni(tdaS)2 anions are located on the lattice points and at the lattice center in the crystal of (m -MPYNN)(2)Ni(tdas)(2). The m -MPYNN cations form a centrosymmetric dimer, and the anion is sandwiched by a pair of the dimers, forming alternate stacks along the a axis. In the crystal of the (p-MPYNN)2Ni(tdas)(2) complex, the Ni(tdas)(2) anions are located on the lattice points and at the center of the bc plane. The anion is surrounded by four p-MPYNN cations. The p-MPYNN cations also form a centrosymmetric dimer. Each cation has a short contact with a different Ni(tdas)(2) anion. The magnetic susceptibilities of both complexes decrease with decreasing temperature, indicating antiferromagnetic interaction within the radicals. The behavior of (m- and p-MPYNN)(2)Ni(tdas)(2) was understood with the singlet-triplet model and the Curie-Weiss law. (C) 2003 Elsevier Science Ltd. All rights reserved.

DOI

Spin density distributions of p-N-alkylpyridinium nitronyl nitroxides studied by solid-state high-resolution NMR

G Maruta, S Takeda, A Yamaguchi, T Okuno, K Awaga

POLYHEDRON ( PERGAMON-ELSEVIER SCIENCE LTD ) 22 ( 14-17 ) 1989 - 1994 2003年07月 [査読有り]

The electron spin density distributions of p-N-alkylpyridinium alpha-nitronyl nitroxides with alkyl = methyl (p-MPYNN) and n-butyl (p-BPYNN) were determined in their iodide salts from the temperature dependence of the solid-state high-resolution H-1 MAS NMR spectra. The results were compared with that of p-pyridyl alpha-nitronyl nitroxide (p-PYNN) to see how positive charge on the aromatic ring affects the spin density distribution. This effect was not significant contrary to the effect of incorporation of a nitrogen atom into the aromatic group. The change in the magnitude of the spin density can be ascribed to the dihedral angle between nitroxide and aromatic moieties. Relatively large hyperfine coupling constant of N-methyl proton, which is almost half as large as those of beta-methyl proton, implies the utility of the N-methyl group as an intermolecular magnetic coupler. (C) 2003 Published by Elsevier Science Ltd.

DOI

Nuclear magnetic relaxation of H-1 in the organic radical salts m-MPYNN+center dot ClO4- and m-MPYNN+center dot BF4-

Y Fujii, T Goto, A Oyamada, T Okuno, K Awaga

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN ( PHYSICAL SOC JAPAN ) 69 ( 5 ) 1294 - 1297 2000年05月 [査読有り]

We have measured nuclear spin-lattice relaxation limes T-1 of H-1 in the organic salts mMPYNN(+). ClO4- and m-MPYNN+. BF4- in the temperature range between 2 K and 100 Ii under external fields up to 70 kOe. In these salts, two cationic (spin-1/2) radicals constitute a dimer due to the ferromagnetic interaction J(1). We interpreted the experimental results of T-1(-1) below about 10 K (similar to J(1)/k(B)) in terms of two relaxation processes based on the energy levels of the ferromagnetic dimer. The flip-flop and the direct processes which are due to longitudinal and transverse spin fluctuations become dominant at higher and lower fields, respectively, the crossover field being around 10 kOe. For the field dependence of T-1(-1) at higlrer temperatures, the spin diffusive model of spin-1/2 in a two-dimensional system is satisfactorily applied.

DOI

Magic angle spinning H-1-NMR study of the spin density distribution of pyridyl nitronyl nitroxides in the crystalline phase

G Maruta, S Takeda, A Yamaguchi, T Okuno, K Awaga, K Yamaguchi

MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS ( GORDON BREACH PUBLISHING, TAYLOR & FRANCIS GROUP ) 334 295 - 304 1999年 [査読有り]

The electron spin density distribution was investigated for p- and m-pyridyl nitronyl nitroxides (p-PYNN and m-PYNN) in the crystalline phase by the temperature dependence of the solid state high resolution H-1-MAS NMR spectrum. The results were compared with that of phenyl nitronyl nitroxide (PNN) for elucidating the effect of incorporation of a nitrogen atom into the aromatic group. For p-PYNN, the magnitude of the negative spin density at 3 and 5 positions of the pyridyl group was suppressed by 30% in comparison with that of PNN and the positive spin density at 2 and 6 positions was slightly enhanced by 10%. On the other hand, the positive spin density at 2, 4 and 6 positions of pyridyl group of m-PYNN was suppressed by 30% in average and the negative one at 5 was also suppressed by 20%. The DFT calculation at UBLYP/6-31G(d, p) level suggested that the molecular geometry largely contributed to the change of the spin density in addition to the effect of incorporation of the nitrogen atom. In fact, the spin density distribution of the aromatic ring of p-PYNN was remarkably reduced in solution compared with that in the crystalline phase.

DOI

Muon-spin-relaxation study of the ground state of the two dimensional S=1 kagome antiferromagnet [2-(3-N-methyl-pyridium)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-l-oxyl-3-N-oxide]BF4

Watanabe, I, N Wada, H Yano, T Okuno, K Awaga, S Ohira, K Nishiyama, K Nagamine

PHYSICAL REVIEW B ( AMER PHYSICAL SOC ) 58 ( 5 ) 2438 - 2441 1998年08月 [査読有り]

Zero- and longitudinal-field positive muon spin relaxation (mu(+) SR) measurements were carried out from 300 K to 30 mK to study a ground state of m-MPYNN . BF4 which is known to be a two-dimensional kagome antiferromagnet with S=1 by ac-susceptibility measurements. An implanted muon is expected to make a hydrogen bonding state with F- ions in the crystal. Muon-spin depolarization by a dynamically fluctuating component of an internal field was still observed at 30 mK. This fluctuating component is suggested to be caused by an intradimer ferromagnetic interaction of 2J(0)/k(B) = 23.3 K between radicals. No clear long-range magnetic ordering of the dimer spins was observed down to 30 mK, suggesting that the ground state of m-MPYNN . BF4 was nonmagnetic.

DOI

Observation of spontaneous magnetization in the layered perovskite ferromagnet, (p-chloroanilinium)(2)CuBr4

T Sekine, T Okuno, K Awaga

INORGANIC CHEMISTRY ( AMER CHEMICAL SOC ) 37 ( 9 ) 2129 - 2133 1998年05月 [査読有り]

The crystal structure and magnetic properties of the layered perovskite, (p-chloroanilinium)(2)CuBr4 (1) have been investigated. The crystal of 1 belongs to the orthorhombic Pbca space group [a = 7.551(2) Angstrom, b = 32.082(10) Angstrom, c = 7.879(2) Angstrom, and Z = 4], which is typical of the material family. The temperature dependence of the ac susceptibility (chi(lac) = (partial derivative M/partial derivative H)) of a polycrystalline sample shows magnetic ordering at 15 K with an abrupt increase of the value. In the ordered state, the field dependence of chi(ac), namely the differential susceptibility, and the de magnetization indicate a hysteresis loop of the magnetization, which can be ascribed to the presence of spontaneous magnetization. Furthermore, single-crystal magnetic measurements indicate that the magnetic properties of 1 are quite anisotropic. When the field is along the b axis (perpendicular to the inorganic layer), the field dependence of chi(ac) shows the hysteresis behavior, as observed for the polycrystals, but when it is parallel to the a axis (parallel to the layer), chi(ac) shows metamagnetic transitions. The observed anisotropy can be understood in terms of a magnetic easy axis parallel to the a axis, an antiferromagnetic interlayer interaction, and a spin canting which produces spontaneous magnetization along the b axis.

DOI

Proton spin-lattice relaxation in m-MPYNN+center dot X- (X = ClO4, BF4) at ultra low temperatures

Y Fujii, T Goto, K Awaga, T Okuno, Y Sasaki, T Mizusaki

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS ( ELSEVIER SCIENCE BV ) 177 991 - 992 1998年01月 [査読有り]

The nuclear spin-lattice relaxation times T-1 of H-1 in organic radical salts m-MPYNN+.X-.1/3(acetone)(X = ClO4, BF4) were measured at ultra low temperatures down to 0.1 K. The T-1 in BF4 salt was almost temperature-independent below 1 K. The experimental results suggest that temperature-independent magnetic fluctuation is caused by frustration effect associated with quantum spin tunnelling in kagome antiferromagnet of S = 1 dimer. (C) 1998 Elsevier Science B.V. All rights reserved.

30a-PS-36 歪んだカゴメ有機反強磁性体の極低温物性,m-AlkylPYNN^+・X^-

吉丸雅浩, 山口明, 阿波賀邦夫, 矢野英雄, 和田信雄, 奥野恒久

日本物理学会講演概要集 ( 一般社団法人日本物理学会 ) 53 375 - 375 1998年

DOI

Observation of spin-gap state in two-dimensional spin-1 Kagome antiferromagnet m-MPYNN center dot BF4

N Wada, T Kobayashi, H Yano, T Okuno, A Yamaguchi, K Awaga

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN ( PHYSICAL SOC JAPAN ) 66 ( 4 ) 961 - 964 1997年04月 [査読有り]

Low temperature properties of the organic spin-1 Kagome' antiferromagnet, m-MPYNN . BF4, have been studied by measuring heat capacity and magnetic susceptibility down to 35 mK. The heat capacity maximum due to a magnetic short-range order was observed at 1.4 K, which is about half of the antiferromagnetic interaction 2\J\/k(B)=3.1 K in the Kagome' lattice. As temperature decreases, the susceptibility begins to decrease below 0.24 K. The susceptibilities both parallel and perpendicular to the Kagome' lattice collapse to almost zero at the lowest temperature, which indicates a nonmagnetic ground state. The temperature dependence suggests that the gap energy of the magnetic state is about 0.25 K.

DOI

Ferromagnetic interaction between nitronyl nitroxide radical cations in a semiconducting salt

H Imai, T Inabe, T Otsuka, T Okuno, K Awaga

SYNTHETIC METALS ( ELSEVIER SCIENCE SA LAUSANNE ) 85 ( 1-3 ) 1705 - 1706 1997年02月 [査読有り]

DOI

Unusual crystal structures and magnetic properties of nitronylnitroxide radical ions

K Awaga, K Takeda, A Yamaguchi, T Okuno, H Yano, N Wada

SYNTHETIC METALS ( ELSEVIER SCIENCE SA ) 85 ( 1-3 ) 1643 - 1646 1997年02月 [査読有り]

We report unusual crystal structures and magnetic properties of nitronylnitroxide radical ions. (i) A nitronylnitroxide anion, p-(nitronyl nitroxide)ben to ate (p-NNBA), is found to crystallize with Mn2+ and water molecules in the form of Mn(p-NNBA)(2)(H2O)(2). In this crystal, the manganese(II) ion is in an octahedral environment, surrounded by two NO groups, two CO2 groups and two H2O. The magnetic properties are well interpreted in terms of the trimer model of [p-NNBA (S=1/2)][Mn2+ (S=5/2)]-[p-NNBA (S=1/2)]. (ii) A nitronylnitroxide cation, m-N-methylpyridinium nitronylnitroxide (m-MPYNN), crystallizes with I-, BF4-, or ClO4- into a trigonal space group, where the spin system is regarded as a spin-1 Kagome antiferromagnet with spin frustration. Low-temperature magnetic measurements reveal a spin-gap state below 0.24 K.

DOI

31P-L-5 二次元スピン・ギャップ反強磁性体m-MPYNN塩のドーピングと磁場効果

和田信雄, 小林竜也, 矢野英雄, 山口明, 奥野恒久, 阿波賀邦夫

日本物理学会講演概要集 ( 一般社団法人日本物理学会 ) 52 511 - 511 1997年

DOI

5p-PSA-5 有機カゴメ反強磁性体、m-AlkylPYNN・Iの構造、磁性、比熱

山口明, 長谷川守邦, 阿波賀邦夫, 小林竜也, 矢野英雄, 和田信雄, 奥野恒久

日本物理学会講演概要集 ( 一般社団法人日本物理学会 ) 52 435 - 435 1997年

DOI

Hydrogen-bonded acid-base molecular complexes of nitronylnitroxides

T Otsuka, T Okuno, M Ohkawa, T Inabe, K Awaga

MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS ( GORDON BREACH SCI PUBL LTD ) 306 285 - 292 1997年 [査読有り]

Intermolecular hydrogen-bonded complexes of p-nitronylnitroxide benzoic acid (p-NNBA-H) with m- and p-pyridylnitronylnitroxides (m-and p-PYNN, respectively) were prepared. The m-PYNN . p-NNBA-H complex crystallizes into the monoclinic P2(1)/c space group [a = 6.685(3) Angstrom, b = 17.657(2) Angstrom, c = 22.169(1) Angstrom, beta = 92.90(1)degrees, V = 261.3(1) Angstrom(3), Z = 4], while the crystal of p-PYNN. p-NNBA H belongs to the monoclinic P2(1)/n space group [a=12.199(3) Angstrom, b = 23.265(4) Angstrom, c = 9.522(2) Angstrom, beta = 101.84(2)degrees, V = 2644.9(9) Angstrom(3), Z = 4]. In their crystals, there is an intermolecular hydrogen bond between the nitrogen atom on the pyridyl ring of PYNN and one of the oxygen atoms of the carboxyl group of p-NNBA-H. The intermolecular N ... O distances are 2.642(5) Angstrom in m-PYNN . p-NNBA-H and 2.613(6) Angstrom in p-PYNN . p-NNBA-H, indicating rather intense hydrogen bonds. The magnetic properties of m-PYNN . p-NNBA-H and p-PYNN . p-NNBA-H are well interpreted in terms of the singlet-triplet model with 2J(AF)/k(B) = -16.0 K and the Curie-Weiss law with theta = -0.68 K, respectively.

DOI

Magnetic interaction in the 1:1 salts of nitronyl nitroxide cations with the dicyanophthalocyaninatocobalt(III) anion

K Mitsuya, T Inabe, T Okuno, K Awaga

MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS ( GORDON BREACH SCI PUBL LTD ) 296 293 - 303 1997年 [査読有り]

Two cationic derivatives of alpha-nitronyl nitroxide (NN), p-PPYNN (p-N-n-propylpyridinium alpha-nitronyl nitroxide) and p-BPYNN (p-N-n-butylpyridinium alpha-nitronyl nitroxide), have been crystallized with the [Co(Pc)(CN)2](-) (dicyanophthalocyaninatocobalt(III)) counter anion. Obtained two kinds of 1:1 salt crystals have been found to be isomorphous; monoclinic, P2(1)/c, a = 15.585(6), b = 11.015(4), c = 26.111(3) Angstrom, beta = 89.95(2)degrees, V = 4482(3) Angstrom(3), Z = 4 for p-PPYNN[Co(Pc)(CN)(2)] and a = 15.830(3), b = 11.201(4), c = 25.709(3) Angstrom, beta = 90.29(1)degrees, V = 4558.4(17) Angstrom(3), Z = 4 for p-BPYNN[Co(Pc)(CN)(2)]. The magnetic interaction between the NN radicals in these two kinds of crystals has been found not to be the same; weak antiferromagnetic interaction operates in p-PPYNN[Co(Pc)(CN)(2)], while only paramagnetic behavior is observed for p-BPYNN[Co(Pc)(CN)(2)].

DOI

Ferromagnetic linear chain of p-NPNN center dot Cu(hfac)(2) with enhanced interchain interaction

T Origuchi, W Fujita, A Yamaguchi, T Okuno, K Awaga, H Yano, N Wada

MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS ( GORDON BREACH PUBLISHING, TAYLOR & FRANCIS GROUP ) 296 281 - 292 1997年 [査読有り]

The complex p-NPNN . Cu(hfac)(2) (p - NPNN =p-nitrophenyl nitronylnitroxide and hfac=hexafluoroacetylacetonate) crystallizes into the triclinic P (1) over bar space group [a=12.515(3) Angstrom, b=12.540(2) Angstrom, c=11.610(3) Angstrom, alpha=106.18(2)degrees, beta=119.15(2)degrees, gamma=91.14(2)degrees, V=1501.7(6) Angstrom(3), Z=2]. The structure consists of an alternating chain of p-NPNN and Cu(hfac)(2) in which p-NPNN bridges two nonequivalent copper ions occupying the axial positions. The chains are connected by a pi-pi and head-to-tail overlap of the p-NPNN molecules, resulting in a two-dimensional network. The high-temperature magnetic susceptibilities can be interpreted in terms of a ferromagnetic intrachain interaction of J/k(B)=14.3 K and an antiferromagnetic interchain interaction of zJ'/k(B)=-2.6 K. The observed interchain interaction which would originate in the overlap of p-NPNN is much stronger than those in the related Cu(II) materials reported so far. The low-temperature magnetic susceptibilities indicate an antiferromagnetic order at T-N=1.22+/-0.01 K, followed by an enhancement of the susceptibility below T-c=0.6+/-0.1 K, probably due to a spin canting.

DOI

Ferromagnetic intermolecular interaction of N-protonated pyridylphenylcarbene

T Okuno, K Awaga

MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS ( GORDON BREACH SCI PUBL LTD ) 305 579 - 586 1997年 [査読有り]

The HCl and DCl salts of phenyl-4-pyridyldiazomethane were prepared and irradiated at 6 K to generate the carbenes. Their ESR spectra indicated presence of plural triplet carbenes with slightly-different zero-field splitting constants. Besides the triplet species, we found a quintet species whose signal intensity decreases with increasing temperature. The quintet spin state was concluded to be a ground state which was produced by an intermolecular ferromagnetic interaction of the triplet carbenes. The ferromagnetic interaction would be explained by the McConnell mechanism, judging from the crystal structure of the HCl salt of phenyl-4-pyridylketone.

DOI

Molecular spin ladder in the Ni(dmit)(2) (dmit=1,3-dithiol-2-thione-4,5-dithiolate) salt with a nitronyl nitroxide cation

H Imai, T Inabe, T Otsuka, T Okuno, K Awaga

PHYSICAL REVIEW B ( AMER PHYSICAL SOC ) 54 ( 10 ) R6838 - R6840 1996年09月 [査読有り]

DOI

Magnetic behavior of the layered perovskite ferromagnet (p-cyanoanilinium(+))(2)CuCl42- under hydrostatic pressure

T Sekine, T Okuno, K Awaga

CHEMICAL PHYSICS LETTERS ( ELSEVIER SCIENCE BV ) 249 ( 3-4 ) 201 - 204 1996年02月 [査読有り]

DOI

2次元スピン・ギャップ有機磁性体m-MPYNN・BF_4II

和田信雄, 小林竜也, 矢野英雄, 山口明, 奥野恒久, 阿波賀邦男

日本物理学会講演概要集. 秋の分科会 ( 一般社団法人日本物理学会 ) 1996 60 - 60 1996年

DOI

Molecular spin ladder in the N (dmit=1,3-dithiol-2-thione-4,5-dithiolate) salt with a nitronyl nitroxide cation

Hiroyuki Imai, Tamotsu Inabe, Takeo Otsuka, Tsunehisa Okuno, Kunio Awaga

Physical Review B - Condensed Matter and Materials Physics 54 ( 10 ) R6838 - R6840 1996年 [査読有り]

The crystal and magnetic structure of the 1:1 salt of Ni(Formula presented) anionic radical and [Ni(Formula presented)] (Formula presented)-ethylpyridinium (Formula presented)-nitronyl nitroxide ((Formula presented)-EPYNN) cationic radical have been studied. Ferromagnetic interaction with (Formula presented) K has been found to operate in the one-dimensional (Formula presented)-EPYNN chains, while the first molecular antiferromagnetic spin ladder has been found to form in the Ni(Formula presented) chains. © 1996 The American Physical Society.

DOI

Nuclear magnetic relaxation of H-1 in organic cation radical salt m-MPYNN(+)X(-) (X=ClO4, BF4)

Y Fujii, T Goto, K Awaga, T Okuno

CZECHOSLOVAK JOURNAL OF PHYSICS ( CZECHOSLOVAK JNL OF PHYSICS ) 46 2213 - 2214 1996年 [査読有り]

The nuclear spill-lattice relaxation time T-1 of H-1 in the organic cation radical salt m-MPYNN(+)X(-) (S=ClO4, BF4) has been measured in the temperature range 1.5 similar to 200K and in the field range 1 similar to 70kOe. The experimental results in high fields were well interpreted in terms of flip-flop relaxation process involving the pairs of ferromagnetic dimers, whose energy scheme consists of lower triplet- and upper singlet-states with the gap energy of 20K. An appreciable increase of the relaxation rate in low fields below about 10kOe was explained by the direct relaxation process due to the band-like spread of each Zeeman level.

DOI

Crystal Structures and Magnetic Properties of MCl4 2- (M=Mn(II) and Co(II)) Salts of m- and p-N-Methylpyridinium Nitronyl Nitroxides

Akira Yamaguchi, Tsunehisa Okuno, Kunio Awaga

Bulletin of the Chemical Society of Japan ( Chemical Society of Japan ) 69 ( 4 ) 875 - 882 1996年 [査読有り]

Organic radical cations, 4,4,5,5-tetramethyl-2-(1-methyl-3 or 4-pyridinio)-3-oxide-4,5-dihydro-1H-1-imidazolyloxyl (or, m- and p-N-methylpyridinium nitronyl nitroxides, abbreviated as m- and p-MPYNN+, respectively), were found to crystallize with magnetic counter anions, MCl4 2- (M = Mn2+ (S = 5/2) and Co2+ (S = 3/2)), although the MnCl4 2- salts were rather air-sensitive. X-Ray full-crystal analyses were carried out on the stable CoCl4 2- salts. The structure of (m-MPYNN+)2CoCl4 2- crystallizes in the monoclinic P21/c space group, while that of (p-MPYNN+)2CoCl4 2- belongs to the triclinic P1 space group. Although (m-MPYNN+)2MnCl2- 4 and (p-MPYNN+)2MnCl4 2- were not stable enough for an X-ray full data collection, they were indicated to be isostructural to the corresponding CoCl4 2- salts, respectively, by their diffractions of 20 &lt
θ &lt
25°. Variable-temperature magnetic susceptibility measurements reveal a clear contrast between the (m-MPYNN+)2MCl4 2- and (p-MPYNN+)2MCl4 2- salts. The two (m-MPYNN+)2MCl4 2- salts exhibit a ferromagnetic behavior independently of MCl4 2-, which is attributable to a m-MPYNN+ dimer. However, the magnetic properties of two (p-MPYNN+)2MCl4 2- salts are strongly dependent on the MCl4 2- anion: (p-MPYNN+)2MnCl4 2- exhibits an antiferromagnetic interaction in opposition to a ferromagnetic one in (p-MPYNN+)CoCl4 2-. The magnetic difference between them can be qualitatively understood in terms of a charge-transfer interaction between MCl4 2- and p-MPYNN+, in which the difference in the electronic structure between the Mn2+ and Co2+ ions is reflected.

DOI

Intercalation of functional organic molecules into copper(II) magnetic materials

K Awaga, W Fujita, T Sekine, T Okuno

MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS ( GORDON BREACH SCI PUBL LTD ) 285 323 - 330 1996年 [査読有り]

(i) The magnetic properties of the series of a layered material, Cu-2(OH)(3)(n-CmH2m+1COO), are found to show an anomalous change, depending on the alkyl-chain length: the m=0 and 1 materials are metamagnetic while the m=7-9 materials become weak ferromagnets below 22 K. Further, 4-phenylazobenzoate and 2-anthracene carboxylate, which are derivatives of well-known photo-functional molecules, are intercalated into the copper hydroxides. The obtained materials are both antiferromagnetic in the whole temperature range of 3-280 K, However, the photochemical reactions do not take place by irradiation with a xenon lump. (ii) The magnetic properties of the layered perovskite ferromagnets (p-cyanoanilinium(+))(2)CuCl42- and (p-chloroanilinium(+))(2)CuBr42- are studied under hydrostatic high pressure of 1.0 GPa. Above T-c, they show an increase of the magnetization, which would due to enhancement of the ferromagnetic coupling, but, below T-c, they show different magnetic response to the pressure.

Mossbauer spectroscopic study of the reentrant phase transitions in TBA[Fe(tdas)(2)]

M Takahashi, M Takeda, K Awaga, T Okuno, Y Maruyama, A Kobayashi, H Kobayashi, S Schenk, N Robertson, AE Underhill

MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS ( GORDON BREACH SCI PUBL LTD ) 285 399 - 404 1996年 [査読有り]

Temperature dependence of Fe-57 Mossbauer spectra for TBA[Fe(tdas)(2)] is measured to obtain the information on the spin state and the phase transitions. The large quadrupole splitting due to the S = 3/2 spin state increases reenteringly in the intermediate temperature region (190 - 230 K on cooling and 200 - 240 K on heating). The small increase in the quadrupole splitting and the continuous decrease in the isomer shift suggests the 3/2 spin state does not change, supporting the interpretation of the magnetic susceptibility.

[NHN](+) hydrogen bond in organic radical solid

T Okuno, T Otsuka, K Awaga

MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS ( GORDON BREACH SCI PUBL LTD ) 278 A57 - A63 1996年 [査読有り]

Reaction of m- or p-pyridyl nitronyl nitroxide (m- or p-PYNN) with HBr gas gave a 2:1 complex between them. The IR spectra of (m- and p-PYNN)(2)HBr indicates an intermolecular [NHN](+) hydrogen bond between two pyridyl rings. (m-PYNN)(2)HBr shows ferromagnetic properties, while the p-isomer does antiferromagnetic properties. Furthermore, the HCl salt of phenyl-4-pyridylcarbene was generated by irradiation of the diazo precursor. The ESR spectrum shows signals of triplet and quintet spin species, latter of which indicates a ferromagnetic interaction between the triplet carbenes.

Intermolecular arrangements of p-substituted aniliniums in the interlayer of cupric chloride

T Sekine, T Okuno, K Awaga

MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS ( GORDON BREACH SCI PUBL LTD ) 278 A65 - A72 1996年 [査読有り]

Crystal structures and magnetic properties of the layered pervoskite compounds, (p-X-C6H4NH3+)(2)CuCl42- with X=CN (1), Cl (2), and NO2 (3), were studied. The compound 1 crystallizes in the triclinic <P(1)over bar> space group. The structure consists of a CuCl layer and an organic bilayer in which the molecular axis of the cyanoanilinium is nearly perpendicular to the inorganic layer. At the middle of the organic bilayer, there is a layer of the CN group, in which the CN groups are arranged to cancel their electric dipoles. The compound 2 has a similar structure to that of 1. The crystal of 3 belongs to the orthorhombic Pbca space group, in which the structure also consists of an inorganic layer and an organic bilayer. The bilayer is formed by short contacts between the NO2 groups, which appear to incline the molecular axis of the nitroanilinium with respect to the normal to the CuCl layer. AC and DC magnetic susceptibility measurements were carried out on the three salts. Their behavior can be understood with two parameters, ferromagnetic transition temperature T-c and in-plane ferromagnetic coupling constant J. The obtained parameters are T-c=9.5 K and J/k(B)=24 K for 1, T-c=9.1 K and J/k(B)=23 K for 2, and T-c=7.0 K and J/k(B)=17 K for 3. The values of T-c and J of 3 are smaller than those of the other two. The distortion of the molecular arrangement in the organic layer of 3, is found to result in weakening the magnetic interaction in the CuCl layer.

EPR STUDIES OF THE 2-D MAGNETIC SYSTEM IN AN ORGANIC CATION-RADICAL SALT, M-MPYNN+CENTER-DOT-X-

M HASEGAWA, A YAMAGUCHI, T OKUNO, K AWAGA

SYNTHETIC METALS ( ELSEVIER SCIENCE SA ) 71 ( 1-3 ) 1797 - 1798 1995年04月 [査読有り]

EPR measurements were carried out on a single crystal of m-N-methylpyridinium nitronyl nitroxide perchlorate which consists of a 2-D bond-alternated hexagonal lattice. Angular dependence of the linewidth Delta H-pp shows minimums at the magic angles, and can be well interpreted with the theoretical equation for the 2-D magnetic system,Delta H-pp=A(3cos2 theta . 1)(2)+B. Temperature dependence of Delta H-pp shows an anomaly between 50 K and 100 K, which could be relevant to freezing of the orientational disorder of the perchlorate ion. Angular dependence of the g-value confirms the 2-D character of the magnetic system. Below 50 K, the EPR signal is affected by the demagnetizing effects.

DOI

CRYSTAL-STRUCTURES AND MAGNETIC-PROPERTIES OF (M-PYRIDINIUM-NITRONYL-NITROXIDE)+CENTER-DOT-X- - POSSIBLE SPIN-1 KAGOME ANTIFERROMAGNET

K AWAGA, T OKUNO, A YAMAGUCHI, M HASEGAWA, T INABE, Y MARUYAMA, N WADA

SYNTHETIC METALS ( ELSEVIER SCIENCE SA ) 71 ( 1-3 ) 1807 - 1808 1995年04月 [査読有り]

Crystal structures and magnetic properties of m-N-methylpyridinium nitronyl nitroxide (abbreviated as m-MPYNN+) salts were studied. m-MPYNN+. ClO4-.(1/3)(acetone) is found to crystallize into the trigonal P3c1 space group, where the m-MPYNN+ molecules exist as a dimer and the dimer units form a 2-D triangular lattice. Temperature dependence of the magnetic susceptibility can be well interpreted in terms of a strong ferromagnetic intradimer interaction J(1) forming a triplet state and a weak antiferromagnetic interdimer interaction J(2). There is a possibility that this spin system can be characterized as a spin-1 Kagome antiferromagnet at very low temperatures. m-MPYNN+ makes salts with various anions, I-, Cl-, BF4-, ClO4- etc. and their mixtures. In an isostructural solid-solution system, m-MPYNN+.(ClO4-)(x) . l-(1-x).(1/3)(acetone) (0 less than or equal to x less than or equal to 1), J(2) quickly weakens with increasing the ratio of the ClO4- ion, in contrast to little dependence of J(1).

DOI

Ferromagnetic and antiferromagnetic intermolecular arrangements of the N-alkylpyridinium nitronyl nitroxide

K Awaga, A Yamaguchi, T Okuno

MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS ( GORDON BREACH SCI PUBL LTD ) 271 97 - 105 1995年 [査読有り]

The magneto-structural correlation in some p-N-alkylpyridinium nitronyl nitroxide salts has been studied. In the iodide salts of p-N-R-pyridinium nitronyl nitroxides with R=methyl, ethyl, n-propyl, and n-butyl, the magnetic property varies from antiferromagnetic to ferromagnetic with the extension of the N-alkyl chain. The nearest-neighbor molecular arrangements of the nitroxides observed in the four crystals, can be classified into two groups: the radicals are connected by a intermolecular contact between the NO groups (Type I) or between the NO group and the pyridinium ring (Type II). The observed magnetic behaviors can be interpreted in terms of an antiferromagnetic intermolecular interaction for the Type I contact and a ferromagnetic for Type II. Effects of replacement of the I- ion by Br- or Cl-, have been also studied in the p-N-methyl derivative.

DOI

VARIABLE MAGNETIC-INTERACTIONS IN AN ORGANIC RADICAL SYSTEM OF (M-N-METHYLPYRIDINIUM ALPHA-NITRONYL NITROXIDE).X- - A POSSIBLE KAGOME ANTIFERROMAGNET

K AWAGA, T OKUNO, A YAMAGUCHI, M HASEGAWA, T INABE, Y MARUYAMA, N WADA

PHYSICAL REVIEW B ( AMER PHYSICAL SOC ) 49 ( 6 ) 3975 - 3981 1994年02月 [査読有り]

In this paper we study an organic system of geometrical spin frustration. m-N-methylpyridinium alpha-nitronyl nitroxide (m-MPYNN+) is a spin-1/2 organic radical. The simple salt, m-MPYNN+.ClO4-.1/3 (acetone), crystallizes in a trigonal P3c1 space group, where the m-MPYNN+ molecules exist as a dimer and the dimer units form a two-dimensional (2D) triangular lattice. One-third of the ClO4- ions are in the organic layer, joining the m-MPYNN+ molecules, and the remainder is between the layers, compensating the excess of positive charge in the organic layers. The single-crystal EPR measurements clearly indicate a 2D Heisenberg character of the magnetic system in it. m-MPYNN+ makes a crystalline solid-solution system, m-MPYNN+.(ClO4-)x.I1-x-.1/3 (acetone) (0 less-than-or-equal-to x less-than-or-equal-to 1), which also belongs to the trigonal system. Both the a and c axes are slightly lengthened with increasing the ratio of the ClO4- ion, x, in the solid solution: The unit-cell volume is increased by 3.2% when x runs from 0 to 1. The temperature dependence of the magnetic susceptibilities of the solid solutions can be well interpreted in terms of a strong ferromagnetic intradimer interaction J1 forming a triplet state and a weak antiferromagnetic interdimer interaction J2 which is expected to give rise to spin frustration among the triplet spin species on each side of the triangles. It is found that J2 quickly weakens with an increase in x, while J1 shows little dependence. There is a possibility that this organic system can be characterized as a spin-1 kagome anti-ferromagnet at very low temperatures.

30p-PSA-39 三角格子有機反強磁性体m-MPYNN塩II

和田信雄, 矢野英雄, 山口明, 奥野恒久, 阿波賀邦夫

日本物理学会講演概要集. 年会 ( 一般社団法人日本物理学会 ) 49 156 - 156 1994年

DOI

13p-PSA-7 有機ラジカル分子がつくる反強磁性カゴメ格子

阿波賀邦夫, 山口明, 長谷川守邦, 奥野恒久, 和田信雄, 板倉充洋, 氷上忍, 稲辺保, 丸山有成

日本物理学会講演概要集. 秋の分科会 ( 一般社団法人日本物理学会 ) 1993 73 - 73 1993年

DOI

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