Tadahiro Nakamoto

Crystal structure and heat capacity of the mixed-valence trinuclear iron monoiodoacetate complex, [Fe(III)2Fe(II)O(O2CCH2I)6(H2O)3][Fe(III)3O(O2CCH2I)6(H2O)3]I

Abstract The crystal structure of a trinuclear iron monoiodoacetate complex was determined. Although it has been incorrectly characterized as [Fe3O(O2CCH2I)6(H2O)3], the correct chemical formula turned out to be [Fe(III)2Fe(II)O(O2CCH2I)6(H2O)3]-[Fe(III)3O(O2CCH2I)6(H2O)3]I (1). The two kinds of Fe3O molecules (Fe(III)2Fe(II)O and Fe(III)3O) are crystallographically indistinguishable. All the Fe atoms are crystallographically equivalent because of a crystallographic threefold symmetry. Heat capacities of 1 seem to exhibit no thermal anomaly in the temperature range 5.5–309 K, although the valence detrapping phenomenon has been observed in this temperature range. This fact indicates that the valence-detrapping phenomenon in 1 occurs without any phase transition, leading 1 to a glassy state, probably because the crystal of 1 is just like a solid solution of distorted mixed-valence Fe(III)2Fe(II)O molecules and permanently undistorted Fe(III)3O molecules which may act as an inhibitor for a cooperative valence-trapping.

Structure of Fe3O complexes with long alkyl chain fatty acid, [Fe3O(O2CCnH2n+1)6L3]NO3 (L=H2O, n=11, 13, 15, 17; L=py, n=13, 15, 17); crystal structure of [Fe3O(O2CC13H27)6(py)3]NO3

Abstract Two series of trinuclear iron(III) carboxylate complexes with long alkyl chains, [Fe3O(O2CR)6L3]NO3 where L=H2O or py (pyridine), were prepared. Powder X-ray diffraction patterns of each series suggested that the aqua series has a double-layer structure and the pyridine series has a single-layer structure. The single crystal X-ray structure determination of [Fe3O(O2CC13H27)6(py)3]NO3 revealed that the compound forms a single-layer structure with the interlamellar orientation of alkyl chains being arranged alternately to those of adjacent layers.

Calorimetric study of the cubic mesogen, ACBC(16)

The heat capacity of the cubic mesogen ACBC(16) was measured between 16 and 500 K by adiabatic calorimetry. As well as the known condensed phases, a new crystalline phase was found to undergo a glass transition at around 165 K. Phase transitions between crystal, SmC, cubic, and isotropic liquid phases took place at 399.16, 431.15, and 474.30 K, respectively. As in the case of ANBC, a broad hump was observed in the heat capacity of the isotropic liquid phase. The first order nature of the SmC–cubic phase transition was confirmed for the first time by the observation of supercooling of the cubic phase. The broad hump in the isotropic liquid phase was shown to extend to a low temperature side if the isotropic liquid was supercooled, suggesting that the event occurring at the hump is not directly related to the cubic–isotropic liquid phase transition.

Adiabatic calorimetry of the metallomesogen purple cobalt stearate Co(O2CC17H35)2

The heat capacity of the metallomesogen purple cobalt stearate Co(O2CC17H35)2 has been measured by adiabatic calorimetry at temperatures between 16 and 420 K. This compound exhibits two crystalline phases (low temperature Cr2 and high temperature Cr1 phases), mesophase (M phase), and isotropic liquid (I phase). A third crystalline phase Cr3, which is entirely metastable with respect to all the others, is suggested by DSC studies. The Cr2-to-Cr1, Cr1-to-M, and M-to-I phase transitions occurred at 362.1, 380.9, and 400.4 K, respectively. The enthalpy and entropy gains at these phase transitions were determined. The mesophase is either smectic A or nematic.

CCDC 1498055: Experimental Crystal Structure Determination

Related Article: Yoichi Sakai, Ryo Ogiso, Takeshi Kawasaki, Takafumi Kitazawa, Tadahiro Nakamoto, Tsutomu Takayama, Masashi Takahashi|2017|Bull.Chem.Soc.Jpn.|90|237|doi:10.1246/bcsj.20160320