Synthesis and Thermal Decomposition of Mn-Al Layered Double Hydroxides

In this paper, the synthesis and thermal decomposition behavior of hydrotalcite-like Mn-Al layered double hydroxide (LDH) have been investigated. First, the Mn-Al LDH was synthesized by the coprecipitation method using various anions such as Cl⁻, CO²⁻₃, NO⁻₃, SO²⁻₄ or dicarboxylic acids (DCA). The single phase of the Mn-Al LDH was obtained when Cl⁻, NO⁻₃ or DCA was used as a guest anion. In the case of CO²⁻₃ or SO²⁻₄, the solid products included MnCO₃ or shigaite as a by-product. The crystallinity of the Cl/Mn-Al LDH was greatly influenced by a drying temperature and that the crystallinity of the Cl/Mn-Al LDH dried at room temperature was found to rise about 6 times in comparison with that dried at 333 K. The DCA/Mn-Al LDH was found to have an expanding LDH structure, supporting that the LDH basal layers were bridged by the intercalated DCA anion. Then, the thermal decomposition of the DCA/Mn-Al LDH has been examined, and the intercalated DCA was found to be decomposed at lower temperature than DCA itself. The oxidation number of Mn ion rose with increasing the heat treatment temperature and was +2.70 with crystallizing Mn₃O₄ after being heated at 973 K. The thermal decomposition of guest DCA was thought to be accelerated by the strong catalytic action of Mn ion in the host hydroxide basal layers.     

Deoxygenation of sugar trifluoromethanesulfonates by sodium metal in liquid ammonia and by photolysis

Several trifluoromethanesulfonyl(TFMS) derivatives of sugars were prepared and treated with sodium in liquid ammonia or subjected to ultraviolet irradiation. Three 3-$\text{O}$-TFMS derivatives gave the corresponding 3-deoxy compounds, but a 2-$\text{O}$-TFMS derivative gave a branched-chain sugar.     

Synthesis,magnetic properties,and electronic spectra of Bis(beta-diketonato)chromium(III) and nickel(II) complexes with a chelated imino nitroxide radical: X-ray structures of [Cr(acaMe)(2)(IM2py)]PF(6) and [Ni(acac)(2)(IM2py)

Two new series of each of four Cr(III) and Ni(II) imino nitroxide complexes with various kinds of beta-diketonates, [Cr(beta-diketonato)(2)(IM2py)]PF(6), and [Ni(beta-diketonato)(2)(IM2py)] (IM2py = 2-(2'-(pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxy)) have been synthesized, and their structures and magnetic and optical properties have been examined. The X-ray analysis demonstrated that a IM2py ligand coordinated to Cr(III) and Ni(II) acts as a five-membered bidentate chelate. The variable-temperature magnetic susceptibility measurements indicated the antiferromagnetic and ferromagnetic interaction of Cr(III) and Ni(II) with IM2py, respectively, giving a variety of the magnetic coupling constant J values with varying the beta-diketonato ligands. The UV-vis shoulders around (19-20) x 10(3) and (17-18) x 10(3) cm(-)(1) for the Cr(III) and Ni(II) complexes, respectively, characteristic of the IM2py complexes were assigned to the metal-ligand charge-transfer transitions, Cr(t(2g))-SOMO(pi*) and Ni(e(g))-SOMO(pi*) MLCT in terms of the resonance Raman spectra and the variable-temperature absorption spectra. The absorption components centered around (13-14) x 10(3) cm(-1) for the Cr(III) and Ni(II) complexes were due to the formally spin-forbidden d-d transition within the t(2g) and e(g) subshells, associated with the intensity enhancement. The spectroscopic behavior with varying the beta-diketonato ligands is discussed in connection with the antiferromagnetic or ferromagnetic coupling constant J values on the basis of the exchange mechanism along with the coligand effect.     

Retroperitoneal ancient schwannoma presenting as an adrenal incidentaloma: CT and MR findings

A 35-year-old woman was referred to our institution for additional examinations to evaluate bilateral suprarenal masses incidentally found on abdominal ultrasonographic images obtained during an annual medical health checkup. Our computed tomographic scans showed bilateral and well-circumscribed low-density suprarenal masses, while MRI revealed the tumors to be heterogeneous with low intensity on T₁-weighted images and high intensity on T₂-weighted images. A laparoscopic adrenalectomy was performed under the suspicion of a malignant tumor, such as a malignant fibrous histiocytoma. Pathologic findings indicated a retroperitoneal ancient schwannoma of two histologic types: Antoni A and Antoni B. We considered that elucidation of the characteristic features of a schwannoma would provide helpful preoperative information for diagnosis.     

84% catalyst activity of water-assisted growth of single walled carbon nanotube forest characterization by a statistical and macroscopic approach

We propose a statistical and macroscopic analysis to estimate the catalyst activity of water-assisted growth (super-growth) of single-walled nanotubes (SWNT) and to characterize SWNT forests. The catalyst activity was estimated to be 84% (+/-6%), the highest ever reported. The SWNT forest was found to be a very sparse material where SWNTs represent only 3.6% of the total volume. This structural sparseness is believed to play a critical role in achieving highly efficient growth.     

Kinetics and mechanism of aquation of [Cr(NCS)(edtrp)]-, [Cr(NCS)(R-pdtrp)]-, [Cr(edtrp)(NCSHg)]+ and [Cr(R-pdtrp) (NCSHg)]+ complexes. Unexpected rate retardation in strongly acidic media for NCS- ligand release

Three new complex ions, [Cr(NCS)(R-pdtrp)]^-, [Cr(R-pdtrp)(NCSHg)]⁺ and [Cr(edtrp)(NCSHg)]⁺, that are derivatives of the trans-equatorial isomers of [Cr(R-pdtrp)(H₂O)]⁰ and [Cr(edtrp)(H₂O)]⁰ (edtrp= ethylenediamine-N,N,N-tripropionate, R-pdtrp= R-propane-1,2-diamine-N,N,N-tripropionate) have been obtained and characterized in solution. Rate constants and activation parameters, including, in two cases, volumes of activation, have been determined. Rate retardation for NCS^- ligand release has been observed with increasing acidity within the pH 0–2 range. The mechanism of the reactions has been discussed.     

Magnetic behavior and Mossbauer spectra of spin-crossover pyrazolate bridged dinuclear diiron(II) complexes: X-ray structures of high-spin and low-spin [(Fe(NCBH3)(py))2(mu-bpypz)2

The synthesis and characterization of new spin-crossover pyrazolato bridged dinuclear [(FeII(NCS)(py))2(mu-bpypz)2] and the corresponding cyanotrihydroborato-kappaN complexes are described together with the X-ray crystal analysis of the latter in both the high-spin and low-spin states as well as the variable temperature magnetic susceptibility and/or Mossbauer spectra demonstrating the spin-crossover which exhibits an one-step process, but not a two-step one characteristic of the known bpym bridged dinuclear complexes.     

Simultaneous determination of halogenated benz(a)anthracenes in water by HPLC with fluorometric detection

Summary A HPLC method using a fluorescence detector is described for the determination of halogenated benz(a)anthracenes (BAX, x=Cl or Br) in water. It consists of the following three procedures; (1) liquid-liquid extraction of BAX with benzene, (2) elimination of interfering compounds from the extracts by one dimensional dual-band thin layer chromatography, and (3) quantitative determination of BAX by HPLC equipped with a fluorescence detector. The recoveries of BAX from water samples through the entire analytical procedure amounted to more than 72%. The calibration curves for BAX were linear, e.g., with a range from 1 to 20 ng ml^–1 for 7-chlorobenz(a)anthracene (BACl). The lower detection limit for BACl was 20 pg for an injection volume of 20 l. This method has been applied to BAX in river water spiked with benz(a)anthracene [B(a)A] at 10 ng ml^–1 after chlorination. B(a)A, BACl and BABr were found in the levels of 2.01, 0.16 and 0.13 or less ng ml^–1, respectively.     

Syntheses, characterization, and photochemical properties of amidate-bridged Pt(bpy) dimers tethered to Ru(bpy)3(2+) derivatives

Amidate-bridged diplatinum(II) entities [Pt(2)(bpy)(2)(μ-amidato)(2)](2+) (amidate = pivalamidate and/or benzamidate; bpy = 2,2'-bipyridine) were covalently linked to one or two Ru(bpy)(3)(2+)-type derivatives. An amide group was introduced at the periphery of Ru(bpy)(3)(2+) derivatives to give metalloamide precursors [Ru(bpy)(2)(BnH)](2+) (abbreviated as RuBnH, n = 1 and 2), where deprotonation of amide BnH affords the corresponding amidate Bn, B1H = 4-(4-carbamoylphenyl)-2,2'-bipyridine, and B2H = ethyl 4'-[N-(4-carbamoylphenyl)carbamoyl]-2,2'-bipyridine-4-carboxylate. From a 1:1:1 reaction of [Pt(2)(bpy)(2)(μ-OH)(2)](NO(3))(2), RuBnH, and pivalamide, trinuclear complexes [Pt(2)(bpy)(2)(μ-RuBn)(μ-pivalamidato)](4+) (abbreviated as RuBn-Pt(2)) were isolated and characterized. Tetranuclear complexes [Pt(2)(bpy)(2)(μ-RuBn)(2)](6+) (abbreviated as (RuBn)(2)-Pt(2)) were separately prepared and characterized in detail. The quenching of the triplet excited state of the Ru(bpy)(3)(2+) derivative (i.e., Ru*(bpy)(3)(2+)) upon tethering the Pt(2)(bpy)(2)(μ-amidato)(2)(2+) moiety is strongly enhanced in RuB1-Pt(2) and (RuB1)(2)-Pt(2), while it is only slightly enhanced in RuB2-Pt(2) and (RuB2)(2)-Pt(2). These are partly explained by the driving forces for the electron transfer from the Ru*(bpy)(3)(2+) moiety to the Pt(2)(bpy)(2)(μ-amidato)(2)(2+) moiety (ΔG°(ET)); the ΔG°(ET) values for RuB1-Pt(2), (RuB1)(2)-Pt(2), RuB2-Pt(2), and (RuB2)(2)-Pt(2) are estimated as -0.01, 0.00, +0.22, and +0.28 eV, respectively. The considerable difference in the photochemical properties of the B1- and B2-bridged systems were further examined based on the emission decay and transient absorption measurements, which gave results consistent with the above conclusions.