bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydration Structure of Glycine Molecules in Aqueous Alkaline Solutions
Authors: Sugawara Kentaro , Kameda Yasuo , Usuki Takeshi , Uemura Osamu , Fukunaga Toshiharu 
Published: September 2002

Abstract
Time-of-flight (TOF) neutron diffraction measurements have been carried out on the alkaline aqueous 2 mol% glycine solution in heavy water. The isotopic substitution technique has been applied to both nitrogen and hydrogen atoms within glycine molecules in order to obtain information concerning the hydration structure around the amino- and methylene group in the glycine molecule under the high-pH condition. Results revealed that the nitrogen atom in the amino group forms a hydrogen bond of the N…D-O type with ca. one D2O molecule (rN…D = 1.97(3) Å, ∠N…D-O = 174(5)°), and simultaneously forms bonds of N-D…OD2 type with ca. two D2O molecules (rN…O = 2.92(3) Å) in the present alkaline aqueous solution. This behavior is in contrast to the hydration structure around the amino group in the glycine molecule reported for the neutral aqueous solution, in which the amino group forms the hydrogen bonds of N-D…OD2 type with ca. three D2O molecules. The first hydration shell around the methylene group in the glycine molecule involves ca. two D2O molecules per one glycine molecule. The orientational correlation between the methylene-hydrogen atoms and neighboring D2O molecules is weak.
Synthesis of a Phosphorylated Polypeptide by a Thioester Method
Authors: Kawakami Toru , Hasegawa Koki , Aimoto Saburo 
Published: September 2002

Abstract
A method for the synthesis of phosphorylated polypeptides was investigated through the synthesis of the phosphorylated cAMP response element binding protein 1 (19-106) amide, [Thr(PO3H2)69,71]-CRE BP1(19-106)-NH2, as a model compound. Three partially protected peptide segments: Boc-[Lys(Boc)23,46,48,54, Cys(Acm)27,32]-CRE BP1(19-56)-SCH2CH2CO-β-Ala-NH2, Fmoc-[Thr(PO3H2)69,71, Lys(Boc)77, Cys(Acm)79]-CRE BP1(57-83)-SCH2CH2CO-β-Ala-NH2, and [Lys(Boc)97,98,105,106]-CRE BP1(84-106)-NH2, were prepared by the Boc solid-phase method and were used as building blocks. The segment condensations were carried out sequentially by a thioester method in the presence of a silver compound, HOObt, and DIEA. The desired product was obtained in 19% yield, based on the C-terminal building block, after removal of all the protecting groups on the peptide. These results indicate that the thioester method is quite useful for the preparation of phosphorylated polypeptide even if it contains cysteine residues. One thing which remains to be improved is the efficiency of the method for the preparation of partially protected peptide thioesters, which contain phosphorylated amino acid residues.
Production of Negative Ions from Fluorocarbons and Reaction Mechanism
Authors: Nakagawa Seiko , Shimokawa Toshinari 
Published: September 2002

Abstract
The temperature dependence of the formation of negative ions from C6F6, C5F5N, C6F5CN, C6F5CF3, and C6F5C6F5 was studied by using negative chemical ionization mass spectrometry. Parent negative ion and fragment ions: F- and (M-F)- (M = Parent Molecule) were observed. Secondary product ions: C5F4- and C5F2- for C6F6 and C5F6N- and C4FN- for C5F5N were also observed at temperatures higher than 523 K. A cluster of the parent molecule and F- is produced for C6F6 and C5F5N. The intensity of parent negative ions increases, while that of fragment ions and secondary ions decreases with decreasing temperature. Such results show that electron detachment from the parent anions will occur. Geometry of parent negative ions and cluster anions of C6F6, C5F5N, C6F5CN, and C6F5CF3 were also calculated using the Hartree-Fock method. The structure and the distribution of the spin density are almost the same for all these molecules. This similarity means that the production of negative ions from them and the reaction mechanisms are almost the same.
Chiral Replacement Criterion for Characterizing Holotopic and Hemitopic Relationships
Authors: Fujita Shinsaku 
Published: September 2002

Abstract
A chiral replacement criterion has been proposed to characterize stereochemical equivalence. This criterion is effective to determine holotopic and hemitopic relationships, which are sub-relationships of a homotopic relationship. The criterion has been shown to be complementary to the membership criterion based on the sphericity concept.
Heat Capacities of Isomeric 2-Butoxyethanols from 13 to 300 K: Fusion and Glass Transition
Authors: Atake Tooru , Kawaji Hitoshi , Tojo Takeo , Kawasaki Koji , Ootsuka Yasushiro , Katou Maki , Koga Yoshikata 
Published: September 2002

Abstract
We measured the heat capacities of 2-butoxyethanol (abbreviated as nBE), 2-isobutoxyethanol (iBE) and 2-t-butoxyethanol (tBE) from 13 to 300 K by adiabatic calorimetry, and glass transition was found for all three: 140 K (nBE), 146 K (iBE) and 150 K (tBE). We were successful in crystallizing nBE and tBE, and determined thermodynamic functions for fusion for the first time. The temperatures of fusion and their enthalpy changes are 199.53 K, 11.8 kJ mol-1 for nBE and 223.09 K, 11.4 kJ mol-1 for tBE. Where possible, we calculated thermodynamic functions. The total entropy in the liquid state at fusion is almost the same, within 1%, between nBE and tBE. However, the values of the liquid heat capacity are about 10% different at the melting point. This indicates that the entropy fluctuation is different while the global average of the entropy remains the same. We measured the density of the liquid and supercooled liquid states for all three samples, and calculated the amplitude, as well as the amplitude plus wavelength of the entropy fluctuation.
Self-Assembled Monolayers of Heme Derivatives on a Gold Surface
Authors: Kobayashi Kazutoshi , Imabayashi Shin'ichiro , Fujita Katsuhiko , Nonaka Kazuhide , Kakiuchi Takashi , Sasabe Hiroyuki , Knoll Wolfgang 
Published: September 2002

Abstract
Thiolated heme derivatives were synthesized and their self-assembly behaviors on gold surfaces together with that of native heme were studied. The kinetics of this adsorption and the thickness of the formed monolayer were investigated by surface plasmon resonance spectroscopy. Native heme shows a different adsorption behavior compared to that of the synthesized derivatives. Though the heme derivatives were found to form monolayers, native heme formed only irregular aggregates on gold surfaces. IR spectroscopy was used to reveal the molecular structure of the adsorbates in the vicinity of the peptide linkage in the heme molecules on the gold surfaces. UV spectroscopy was employed to determine the tilt angle of the porphyrin rings relative to the gold surface normal. Cyclic voltammograms and potential-modulated UV-vis reflectance spectra of heme derivatives were observed in order to estimate the adsorbed amount and the redox behaviors of heme derivatives on gold surfaces.
In-Bond Orbitals: A Comprehensive Graphical Expression of Orbital Interaction
Authors: Ichikawa Hiroshi , Kagawa Hirotaka , Kaneko Chikara 
Published: September 2002

Abstract
The minimal linear-combination-of-atomic-orbitals (LCAO) has a clear chemical meaning, namely, that a molecular orbital consists of atomic orbitals of the member atoms. In organic chemistry, this concept has been applied to graphical expression of orbital interactions. However, the minimal LCAO method is inadequate to illustrate such interatomic interactions. Based on a general idea in quantum chemistry, we have proposed pictorial ``in-bond orbitals'' to compensate for the shortcomings of the minimal LCAO scheme without destroying its simple concept. In-bond orbitals well express the qualitative electronic structures of bonding and antibonding internuclear regions. Furthermore, they are continuously correlated with the AOs of the united atom. In this paper, (1) we discuss the conceptual problems of the minimal LCAO expression in interaction between atoms, (2) we show the importance of the contribution of AOs with higher quantum numbers to the chemical interaction nominally given by AOs with the lowest quantum number, (3) we show that the introduction of a minimal number of in-bond orbitals is a simple method to solve the continuity problem of the correlation diagram and to improve the electronic structure, (4) a selection scheme for in-bond orbitals is proposed, and (5) as an example, the concept of the in-bond orbital is applied to the prediction of the direction of pyramidalization of the olefinic carbon atoms of norbornene.
Characterization of Prochirality and Classification of Meso-Compounds by Means of the Concept of Size-Invariant Subductions
Authors: Fujita Shinsaku 
Published: September 2002

Abstract
The concept of size-invariant subductions has been proposed to design prochiral molecules. Thus, an even-membered homospheric orbit has been proved to be desymmetrized into an enantiospheric orbit, where the sizes of the relevant orbits remain invariant. The concept has been applied to methanes, allenes, adamantanes, and biphenyls. It has proved effective in designing a wide variety of prochiral molecules. These prochiral molecules have been shown to be extrinsic meso compounds. Intrinsic meso compounds have also been discussed as another type of prochiral molecule.
Site-Selective X-Ray Absorption Fine Structure (XAFS) Spectroscopy. (1) Design of Fluorescence Spectrometer and Emission Spectra
Authors: Izumi Yasuo , Oyanagi Hiroyuki , Nagamori Hiroyasu 
Published: September 2002

Abstract
A Rowland-type fluorescence spectrometer was designed to measure site-selective XAFS spectra by utilizing the chemical shift of emission peak for each site. The positions of Johansson-type cylindrically-bent Ge(111) crystal and scintillation counter were controlled independently by five-channel stepping motors, thereby satisfying precise Rowland condition. Thus, measurements of many fluorescence lines over wide ranges of Bragg angle 55.6—83.9° and Rowland radius 127.7—240.9 mm are made feasible. The Cu Kα peak shifted by +1.6 eV on going from Cu to CuCl and by -0.6 eV on going from CuCl to CuCl2. The Cr Kβ1 peak shifted by +0.8 eV on going from Cr to Cr2O3 and by -1.6 eV on going from Cr2O3 to K2CrO4. The FWHM of Cu Kα peaks was as small as 3.0 eV. The major factor to control the energy resolution of this spectrometer was found to be geometrical angle width (slit size). The effects of Rowland radius and X-ray penetration depth into the bent crystal were smaller in the range of slit size in this paper [slit length (horizontal) in front of I0 ion chamber was 0.5—2.0 mm and two slit lengths (vertical) in Rowland circle were 0.5—5.5 mm].
Reinvestigation of Decarboxylation Kinetics from the Hydrogencarbonatocobalt(III) Intermediate
Authors: Kitamura Yoichi , Yano Leona , Fujimori Kazuya , Mizuki Ryuji , Hayashi Masayuki , Shibata Akira 
Published: September 2002

Abstract
Acid-catalysed hydrolysis has been studied by a stopped-flow method at 25 °C, ionic strength of 2.0 (NaClO4) and oxonium ion concentration of 0.02—1.0 M for monodentate carbonato complexes ( [Co(CO3)(NH3)5]+, [Rh(CO3)(NH3)5]+, and [Ir(CO3)(NH3)5]+) and for didentate carbonato complexes ( [Co(CO3)(NH3)4 ]+, [Co(CO3)(en)2]+, α, β-[Co(CO3)(trien)]+, [Co(CO3)(tren) ]+ and [Co(CO3)(nta)]2- (M = mol dm-3, en = ethylenediamine, trien = 1,8-diamino-3,6-diazaoctane, tren = tris(2-aminoethyl)amine, and H3nta = nitrilotriacetic acid) ). The experimental first-order rate constant of decarboxylation from the monodentate hydrogencarbonato intermediate depends on the acidity of the solution, which we ascribe to its amphiprotic character. The deprotonation constant depends critically on an aqua ligand cis to the hydrogencarbonato ligand: 0.004—0.6 M with it, whereas about 10-6 M without it. We interpret that the former strong acidity originates from the stability of the aquacarbonato complex, owing to a strong (21—33 kJ mol-1) intramolecular hydrogen bond. The basicity has been confirmed by the acidity dependent zero-time spectra, the protonation constant being 0.1—0.7 M-1. The hydrolysis rate constant of the monodentate carbonic acid complex has been estimated to be smaller than 0.3 s-1 at 25 °C.
NMR Studies on the Aggregation of Mononuclear and Dinuclear Cobalt(III) Amphiphilic Complexes Having Alkyl Chains
Authors: Iida Masayasu , Sakamoto Akie , Yamashita Taeko , Shundoh Kaori , Ohkawa Shiho , Yamanari Kazuaki 
Published: September 2002

Abstract
The aggregation of novel type cobalt(III) surfactants, such as [Co(en)2{NH2(CH2)2S(1-CnH2n+1)}]3+ (n = 6, 8, and 12) and [(en)2Co{NH2(CH2)2 S(CH2)mS(CH2)2NH2}Co(en)2]6+ (m = 8 and 12), was studied in water using multinuclear NMR spectroscopies, 1H NMR self-diffusions, and 1H NMR chemical shifts. The 59Co linewidths of the surfactants were useful to monitor the premicellar and micellar formation. It was revealed that the tripositive mononuclear surfactants have comparable cmc (critical micelle concentration) values to those for the usual monovalent surfactants having the same alkyl chains. The 35Cl longitudinal relaxation rates for the counterions were useful to monitor the two kinds of ionic interactions, i.e., those with the surfactant monomers and with the micelles. We determined the cmcs for the premicellar formation in the hexyl mononuclear and octyl dinuclear complex systems. The determination of this kind of cmc has become possible by using such highly charged complexes as the cystam complex and by measurements of the 59Co linewidths and of the 35Cl longitudinal relaxation rates. The self-diffusion coefficient for the surfactants revealed that the aggregation behavior is similar in comparison between the hexyl mononuclear and octyl dinuclear complexes or between the octyl mononuclear and dodecyl dinuclear complexes.
Circular Dichroism Spectrophotometric Determination of Metal Ions Using Optically Active Tris(thiolato) Type Rhodium(III) Complexes
Authors: Aizawa Sen-ichi , Sone Yasushi , Khajar Siti , Ohishi Yuuki , Yamada Shinkichi , Nakamura Motoshi 
Published: September 2002

Abstract
Sparingly soluble neutral fac(S)-[Rh(aet)3] was newly optically resolved in order to apply the optically active isomer as a CD-inducing reagent to the circular dichroism (CD) spectrophotometric determination of the transition metal ions. Simple determinations of cobalt(II) and nickel(II) and a simultaneous determination for the binary solution were successful by using an excess of powdery Λ-fac(S)-[Rh(aet)3] with the dissolution equilibrium. A more sensitive determination of the transition metal ions, such as iron(III), iron(II), cobalt(III), cobalt(II), and nickel(II), was possible by using a homogeneous solution of ΔLLL-fac(S)-[Rh(L-cys-N,S)3]3- without the dissolution equilibrium. The latter CD spectrophotometric determination is quite effective for a simultaneous determination of the transition metal ions in binary and ternary solutions of metal ions, such as iron(III)-cobalt(III), cobalt(III)-cobalt(II), and cobalt(II)-nickel(II)-zinc(II).
Rotational Isomerism Involving an Acetylenic Carbon: Synthesis of and Barrier to Rotation around C(sp)-C(sp3) Bonds in Bis(1,4-disubstituted 9-triptycyl)ethynes
Authors: Toyota Shinji , Yamamori Takao , Asakura Mitsuhiro , Oki Michinori 
Published: September 2002

Abstract
The substituent effect on the rotational barriers of acetylenic to tetrahedral C-C bonds was studied for the title compounds carrying Me or OMe substituents at the 1,4-positions in the 9-triptycyl groups. These compounds were prepared by use of the Diels-Alder and the Sonogashira reactions from a 9-ethynylanthracene derivative. The kinetic parameters were determined by the total lineshape analysis of the signals observed by the variable temperature 1H NMR for five compounds. The rotational barriers are in the range of 9—15 kcal mol-1, and are enhanced as the steric size of the substituents is increased (H &lt; OMe &lt; Me). This substituent effect is attributed to the destabilization of the transition state of the rotation process, where the two triptycyl groups are almost eclipsed about the central axis, by the steric interactions between the peri substituents. The acetylenic carbons are significantly deformed from the linear geometry in the X-ray structure of the tetramethyl compound. The substituent effect on the rotamer population is also discussed with the aid of the MM calculation.
[Ru(bpy)2(dppz-NH2)]2+ Complex (dppz-NH2: 7-Amino-dipyrido[3,2-a : 2′,3′-c]phenazine) as a Useful Photosensitizing Unit for the Construction of Photoinduced Energy Transfer Systems
Authors: Choi Chang-Shik , Mishra Lallan , Mutai Toshiki , Araki Koji 
Published: September 2002

Abstract
7-Amino-dipyrido[3,2-a : 2′,3′-c]phenazine (dppz-NH2) has a diimine coordination site, a rigid and extended π conjugation system, and a reactive amino group within the molecule, and [Ru(bpy)2(dppz-NH2)]2+ was synthesized as a useful photosensitizing unit for the construction of photoinduced energy-transfer systems. Anthraquinone, anthracene, and [Os(bpy)3]2+ derivatives having a carboxylic acid function were used as energy-accepting units, and were successfully connected to [Ru(bpy)2(dppz-NH2)]2+ through an amide bond. Electronic spectral and electrochemical studies of the resultant complexes were carried out, and it was shown that effective excited electron or energy transfer took place from the Ru(II) polypyridyl center to these units. In the case of the heterodinuclear Ru(II)/Os(II) complex, emission from the Ru(II) polypyridyl center was effectively quenched and that from the Os(II) polypyridyl center was increased compared to the reference Os(II) polyimine complex. The rate of energy transfer from the Ru(II) to the Os(II) polypyridyl center through the dppz-amide connector was estimated to be 1.0 × 108 s-1 in acetonitrile.
Magnetic Properties of Iron(III) Complexes with Photoisomerizable Ligands
Authors: Hirose Shigeyuki , Hayami Shinya , Maeda Yonezo 
Published: September 2002

Abstract
New spin-crossover Iron(III) complexes [Fe(salten)(trans-stpy)]BPh4·(CH3)2CO·0.5H2O 1 and [Fe(salten)(cis-stpy)]BPh42 with cis-trans photoisomerizable ligands have been synthesized and characterized, where trans-stpy is trans-4-styrylpyridine and cis-stpy cis-4-styrylpyridine, and salten denotes bis(3-salicylideneaminopropyl)amine, which is a quinquedentate Schiff base derived from the condensation of salicylaldehyde and di(3-aminopropyl)amine. The data of the variable-temperature magnetic susceptibility measurements for the complexes show that 1 and 2 exhibit spin-crossover phenomena in a solid. The spin-state transition temperature of 1 is lower than that of 2. The temperature dependencies of the Mössbauer spectra for the complexes also provide evidence that spin-state transitions between the high- and low-spin states take place, and that the rates of the spin interexchange at 298 K are faster than the inverse of the lifetime (1×10-7 s) of the Mössbauer nucleus. A temperature dependence of the UV-visible spectra suggesting spin-equilibrium in acetonitrile solution was obtained. The X-ray diffraction structures of single crystals of 1 and 2 were determined. Crystal data for 1: C60H61N4O3.5FeB, space group P1 (#2), Z = 2, a = 14.83(1), b = 17.98(1), c = 11.31(2) Å, α = 103.71(8), β = 110.60(8), γ = 94.31(7)°, V = 2702(5) Å3, R = 14.0%, Rw = 17.2%. Crystal data for 2: C57H54N4O2FeB, space group P21/n (#14), Z = 4, a = 14.823(9), b = 17.417(7), c = 18.37(1) Å, β = 95.331(8)°, V = 4722(3) Å3. The coordination cores of both complexes have trans coordination in oxygen atoms. Although light irradiation to 1 in acetonitrile brings about isomerization from trans- to cis- of styrylpyridine, the change in the spin-state of the complexes is not clear.
Syntheses, Crystal Structures, and Some Spectrochemical Properties of S-Bridged Tetranuclear Complexes with Stacking Arrangements Composed of Planar Palladium(II) Units
Authors: Yamada Yasunori , Fujisawa Kiyoshi , Okamoto Ken-ichi 
Published: September 2002

Abstract
The reaction of [Pd(aet)2] (aet = 2-aminoethanethiolate) with [Pd(NO3)2(diimine)] (diimine = 2,2′-bipyridine (bpy), 4,4′-dimethyl-2,2′-bipyridine (dmbpy), 1,10-phenanthroline (phen), 4,7-dimethyl-1,10-phenanthroline (dmphen)) gave a new type of S-bridged tetranuclear complex [{Pd(diimine)}2{Pd(aet)2}2]4+. The crystal structures of these complexes were determined by X-ray crystallography. In these complexes, the two intramolecular diimine moieties are aligned so as to overlap each other and the PdN2S2 planes in the {Pd(aet)2} units are almost perpendicular to those in the {Pd(diimine)} moieties. In the case of diimine = bpy and dmbpy, furthermore, the complex cations exist in the dimeric structure with a coplanar stacking arrangement, in which the diimine moieties of the two distinct complex cations are antiparallel to each other. In the case of diimine = phen and dmphen, on the other hand, the complex cations exist in the linear-chain-like structure with an alternate coplanar stacking arrangement, in which the diimine moieties of the neighboring complex cations are antiparallel to each other. All of the complexes were characterized on the basis of the electronic absorption, diffuse reflection, and 13C NMR spectra.
Enantioselective Photocyclization of Acrylanilides and N-Ethyl-N-methylbenzoylformamide in Inclusion Crystals with (R,R)-(-)-[trans]-2,3-Bis(α-hydroxydiphenylmethyl)-1,4-dioxaspiro-[4.4]nonane and -[4.5]decane. Mechanistic Study Based on X-Ray Crystal Structure Analyses
Authors: Ohba Shigeru , Hosomi Hiroyuki , Tanaka Koichi , Miyamoto Hisakazu , Toda Fumio 
Published: September 2002

Abstract
X-Ray structure analyses of the inclusion complexes indicated that the high stereo- and enantioselectivities in photocyclization of cyclohex-1-enecarboic acid methyl-phenyl-amide (3), N-methyl, N-{(E)-methylmethacryloyl}anilide (5), N-methyl, N-(methacryloyl)anilide (8), and N-ethyl-N-methylbenzoylformamide (10) are the result of their chiral conformations in the clathrate crystalline environment with the title chiral hosts [(-)-1 and (-)-2, respectively]. The chirality of acrylanilides and benzoylformamide can be indicated by the sign of the torsion angle in the backbone of the molecule, C-N-C(=O)-C and O=C(-Ph)-C(=O)-N, respectively. A partial single-crystal-to-single-crystal transformation of 1 : 1 complex of 10 with (-)-1 was performed by photoirradiation to observe in situ the photoproduct.
A Novel Maleic Anhydride Derivative from the Fungus Talaromyces sp. No. 10092
Authors: Yamanishi Ryo , Okada Kazuki , Tamugi Norihusa , Iwashima Makoto , Iguchi Kazuo 
Published: September 2002

Abstract
A new maleic anhydride derivative 1 (FR222398) was isolated from fermentations with the fungus Talaromyces sp. No. 10092. The structure of 1 was determined based on spectroscopic analysis and chemical conversion. The sodium salt of 1 exhibited a dispersant activity toward kaolin suspension.
Synthesis, Structure, and Reactions of Octakis(1,1,2-trimethylpropyl)octagermacubane
Authors: Unno Masafumi , Higuchi Koichi , Furuya Koji , Shioyama Hiroaki , Kyushin Soichiro , Goto Midori , Matsumoto Hideyuki 
Published: September 2002

Abstract
Octathexyloctagermacubane (1, thexyl = 1,1,2-trimethylpropyl) was synthesized by the condensation of trichlorothexylgermane with Mg/MgBr2, and structurally characterized by X-ray crystallography. As in the case of the thexyl-substituted octasilacubane, a ring-opening reaction followed by skeletal rearrangement of 1 took place with PCl5 to give endo, exo- and exo,exo-4,8-dichlorooctathexyltetracyclo[3.3.0.02,7.03,6]octagermanes. Treatment of these dichlorides with sodium afforded octagermacubane 1.