Masashi Takahashi

Spin-crossover behaviour of the coordination polymer FeII(C5H5N)2NiII(CN)4

The iron(II) spin state of Fe(C5H5N)2Ni(CN)4 changes from paramagnetic to diamagnetic when the temperature is lowered, while that of Fe(NH3)2Ni(CN)4·2C6H6 does not.

Cadmium cyanide–ether clathrates: crystal structures of Cd8(CN)16(H2O)6·6G (G = Et2O or Pri2O) and Cd3(CN)6(H2O)2·2Prn2O

The cadmium cyanide host clathrates Cd8(CN)16(H2O)6·6G (G = Et2O 1a or Pri2O 1b) and Cd3(CN)6(H2O)2·2Prn2O 2 have been prepared and their structures determined by X-ray crystallography: 1a, cubic, space group P3n, a= 15.661 (5)A, Z= 2, R= 0.045 for 565 reflections; 1b, cubic, space group P3n, a= 15.762(9)A, Z= 2, R= 0.035 for 653; 2, monoclinic, space group C2/c, a= 14.044(6), b= 18.034(6), c= 12.931 (4)A, β= 111.47(2)°, Z= 4, R= 0.040 for 2003. The novel hosts in 1a and 1b contain tetrahedral and octahedral Cd atoms in a 5:3 ratio. The host in 2 is isostructural to that of the previously reported Cd3(CN)6(H2O)2·2PriOH 3, containing tetrahedral and octahedral cadmium atoms in a ratio of 2:1. The guest ether molecules are accommodated in cage-like cavities, and participate in hydrogen bonding between their O atoms and those of the co-ordinated water molecules.

Comparison of adsorption characteristics of methyl orange and α-naphthol orange molecules onto the cationic Langmuir-Blodgett films

The adsorbability of dicationic Langmuir-Blodgett (LB) film, which was fabricated by film materials of N,N′-ω-p-xylylenebis(stearyldimethylammonium chloride) (XSAC), have been investigated by using dye molecules such as methyl orange (MO) and α-naphthol orange (NO) as adsorbates. The structural characterizations of these LB films before and after dye adsorption were also carried out by applying spectroscopic methods and X-ray diffraction analysis. As a result, it was found that dye molecules in the dye-adsorbed XSAC LB film exhibited the remarkable distinction in the adsorbing state, i.e., an edge-on structure for the MO molecule and a lie-flat structure for the NO molecule. Such molecular arrangements were almost the same as those of corresponding XSAC-dye complexed LB films, which was deposited from XSAC monolayers on the aqueous dye solutions. Furthermore, the dye adsorption of MO and/or NO occurred with the nearly stoichiometrical ratio of XSAC to dye in XSAC LB films, similar to the case of tristearylmethylammonium chloride (TSAC) to dye in TSAC LB films.

Preparation of langmuir-Blodgett films of long-chain alkylammonium salts

Abstract The possibility of formation of Langmuir-Blodgett (LB) films of mono-, di-, and trialkylammonium salts without any additives in the subphase was investigated. The monolayers of distearyldimethylammonium chloride and tristearylammonium chloride could be transferred onto a glass surface in multilayer form from the plain water surface only at surface pressures slightly higher than their equilibrium spreading pressures, while transfer was impossible for the monolayers of monoalkylammonium chlorides. In order to determine the structure of the deposited films, X-ray diffraction, attenuated total reflection-Fourier transform IR spectroscopy, X-ray photoelectron spectroscopy, and contact angle measurements were carried out. Consequently, it was found that the LB film of tristearylmethylammonium salt was regularly and uniformly deposited, compared with that of distearyldimethylammonium salt, and the structure of these cationic LB films takes the Z-type form.

Adsorbability of dye molecules on Langmuir-Blodgett films of long-chain alkylammonium salts

The adsorbability of α-naphthol orange (NO) and methyl orange (MO) at monolayers at the water surface and at Langmuir-Blodgett (LB) films on substrates was investigated. It was found that dye molecules such as NO and MO were selectively adsorbed on LB films of long-chain alkylammonium salts. Furthermore, we found that NO and MO molecules had the same conformation for LB films on a substrate and monolayers at the water surface.

Cd(CN)3–: a novel mineralomimetic infinite chain-like polycyanopolycadmate anion

[SbPh4]2[Cd(CN)3]2 contains a novel mineralomimetic infinite chain-like Cd(CN)3–anion which is topologically similar to the linear single chain SiO32– having a repeat unit after every second tetrahedron in the pyroxenes.

121Sb Mössbauer spectra for crown ether adducts of antimony(III) chloride and molecular structure of SbCl3.12-crown-4

The 121Sb Mossbauer spectra for the crown ether (12-crown-4, 15-crown-5 and 18-crown-6) adducts of antimony(III) chloride at 20 K show that the stereochemical activity of the lone pair of the SbIII atom varys with the antimony–crown ether interaction, which is strongest in the 12-crown-4 adduct having the shortest average Sb–O distance of 2.81(7)A.

Tetranuclear iron(III) complexes with amino acids involving a planar (µ-oxo)(µ-hydroxo)bis(µ-alkoxo)bis(µ-carboxylato)tetrairon core†

Reactions of FeIII(NO3)3·9H2O with 0.5 equivalent of 2-hydroxypropane-1,3-diamine-N,N,N′,N′-tetraacetic acid (H5dhpta) and an excess of amino acid [glycine (Gly) or L-alanine (L-Ala)] in water with the pH adjusted to ca. 5 by a solution of NaOH gave pale green crystals formulated as Na[Fe4(dhpta)2(µ-O)(µ-OH)(O2CCHRNH3)2] (Rxa0=xa0H 1 or CH3 2) in moderate yields. The tetrairon(III) complexes were characterized by elemental analyses, IR and 57Fe Mossbauer spectra, variable-temperature magnetic susceptibility, and X-ray crystallographic and absorption analyses. The structure of 2·6H2O was determined by X-ray crystallography to comprise a (µ-oxo)(µ-hydroxo)bis(µ-alkoxo)bis(µ-carboxylato)tetrairon(III) cluster core bridged by two dhpta and two amino acid ligands. Two identical dinuclear iron(III) units [Fe(1)Fe(2) and Fe(3)Fe(4)] are each co-ordinated by a pentadentate dhpta ligand. The Fe(1) and Fe(4) are then bridged by the carboxylate of an amino acid and an oxo group, with the Fe(2) and Fe(3) similarly linked. The central two oxo groups are protonated to form a strongly hydrogen bonded (O–H–O)3– bridge [O·xa0·xa0·O 2.426(4) A]. The average Fe·xa0·xa0·Fe distance for the µ-alkoxo dinuclear units is 3.692 A (intradimer) and that for the bis(µ-carboxylato)(µ-oxo/hydroxo)diiron units is 3.463 A (interdimer), both being in accord with the corresponding values from EXAFS analyses. The two L-alanine moieties are in zwitterionic form and act as interdimer bridging ligands with the carboxylate groups. The Na+ counter cation is well packed between the tetrairon(III) complex anions, resulting in an infinite chain aggregation. The 57Fe Mossbauer spectrum for 2·6H2O clearly demonstrated that the four iron sites are equivalent, being in a high-spin octahedral iron(III) state. The variable-temperature magnetic susceptibility measurement for 2·6H2O showed modest antiferromagnetism with an interdimer coupling constant (J) of –42.3 cm–1 and an intradimer coupling constant (J′) of –20.8 cm–1.

Adsorbability and structural characterization of Langmuir-Blodgett films of N,N′-ω-p-xylene-bis-[stearyldimethylammonium chloride]

Abstract The adsorbability of α-naphthol orange (NO) onto the dicationic Langmuir-Blodgett (LB) films of N , N ′- ω -p-xylene-bis-[stearyldimethylammonium chloride] (XSAC) with octadecane was investigated. As a result, the specific adsorbability of mixed LB films was observed for NO molecules at the molar fraction of 0.25. The film structures before and after dye adsorption were also studied by using Fourier transform infrared spectroscopy, UV-Vis spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. It was found that NO molecules have the same molecular arrangements in both NO-adsorbed LB films and XSAC-NO-complexed LB films.

155Gd Mössbauer Spectroscopic Study of GdM(CN)6 · 4H2O (M = CrIII, FeIII and CoIII) and KGdM(CN)6 · 3H2O (M = FeII and RuII)

155Gd Mössbauer spectroscopic studies of the title complexes have been performed. Although the 155Gd isomer shifts (d) varied scarcely, the quadrupole coupling constants (e2qQ) changed in the range 4.07-4.81 mm s-1. The e2qQ values of KGdM(CN)6 · 3H2O (M = FeII and RuII) are larger than those of GdM(CN)6 · 4H2O (M = CrIII, FeIII, and CoIII), these values increasing with increasing orthorhombic distortion of the crystal structures. A relationship between the e2qQ values and the ionic radii of the transition metal ions has also been recognized