bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiple Phase Transitions in Long‐Range First‐Passage Percolation on Square Lattices
Authors: Chatterjee Shirshendu , S. Dey Partha
Published: May 2015

We consider a model of long‐range first‐passage percolation on the d‐dimensional square lattice ℤd in which any two distinct vertices x,y ∊ ℤd are connected by an edge having exponentially distributed passage time with mean ‖x–y‖α+o(1), where α > 0 is a fixed parameter and ‖·‖ is the l1–norm on ℤd. We analyze the asymptotic growth rate of the set ßt, which consists of all x ∊ ℤd such that the first‐passage time between the origin 0 and x is at most t as t → ∞. We show that depending on the values of α there are four growth regimes: (i) instantaneous growth for α < d, (ii) stretched exponential growth for α ∊ d,2d), (iii) superlinear growth for α ∊ (2d,2d + 1), and finally (iv) linear growth for α > 2d + 1 like the nearest‐neighbor first‐passage percolation model corresponding to α=∞. © 2015 Wiley Periodicals, Inc.
Crystal growth, crystal structure and pyroelectric properties of the polar hexagonal antimony tartrates MII[Sb2(C4H2O6)2]·2H2O (MII = Ca, Sr, Pb)
Authors: Bohatý Ladislav , Held Peter , Schneeberger Helmut , Zheng Tianyi , Becker Petra
Published: May 2015

Single crystal growth of lead antimony tartrate dihydrate, Pb[Sb2((+)C4H2O6)2]·2H2O, was successfully performed. The determined polar hexagonal crystal structure is isomorphous to the corresponding calcium and strontium antimony tartrates dihydrates. New results of crystal growth and the redetermination of the crystal structures of the nonlinear optical crystal Sr[Sb2((+)C4H2O6)2]·2H2O and its calcium analogue are reported, together with investigations of the thermal stability and the pyroelectric properties of these polar crystals.

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Titania‐Supported Catalysts for Levulinic Acid Hydrogenation: Influence of Support and its Impact on γ‐Valerolactone Yield
Authors: Ruppert A. M. , Grams J. , Jędrzejczyk M. , Matras‐Michalska J. , Keller N. , Ostojska K. , Sautet P.
Published: May 2015

Invited for this month’s cover are the groups from Lodz University of Technology (Poland), from the University of Strasbourg (France) and from the University of Lyon (France). The image shows which titania phase can facilitate the distribution of ruthenium metal on its surface and, hence, which factors allow to prepare active catalysts for biomass valorization. The Full Paper itself is available at 10.1002/cssc.201403332.
Testing Taxon Tenacity of Tortoises: evidence for a geographical selection gradient at a secondary contact zone
Authors: Edwards Taylor , Berry Kristin H. , Inman Richard D. , Esque Todd C. , Nussear Kenneth E. , Jones Cristina A. , Culver Melanie
Published: May 2015

We examined a secondary contact zone between two species of desert tortoise,Gopherus agassiziiandG. morafkai. The taxa were isolated from a common ancestor during the formation of the Colorado River (4–8 mya) and are a classic example of allopatric speciation. However, an anomalous population ofG. agassiziicomes into secondary contact withG. morafkaieast of the Colorado River in the Black Mountains of Arizona and provides an opportunity to examine reinforcement of species' boundaries under natural conditions. We sampled 234 tortoises representingG. agassiziiin California (n = 103),G. morafkaiin Arizona (n = 78), and 53 individuals of undetermined assignment in the contact zone including and surrounding the Black Mountains. We genotyped individuals for 25STRloci and determined maternal lineage using mtDNAsequence data. We performed multilocus genetic clustering analyses and used multiple statistical methods to detect levels of hybridization. We tested hypotheses about habitat use betweenG. agassiziiandG. morafkaiin the region where they co‐occur using habitat suitability models.Gopherus agassiziiandG. morafkaimaintain independent taxonomic identities likely due to ecological niche partitioning, and the maintenance of the hybrid zone is best described by a geographical selection gradient model.
Phenotypic switch of CD8+ T cells reactivated under hypoxia toward IL‐10 secreting, poorly proliferative effector cells
Authors: Vuillefroy de Silly Romain , Ducimetière Laura , Yacoub Maroun Céline , Dietrich Pierre‐Yves , Derouazi Madiha , Walker Paul R.
Published: May 2015

CD8+ T cells controlling pathogens or tumors must function at sites where oxygen tension is frequently low, and never as high as under atmospheric culture conditions. However, T‐cell function in vivo is generally analyzed indirectly, or is extrapolated from in vitro studies under nonphysiologic oxygen tensions. In this study, we delineate the role of physiologic and pathologic oxygen tension in vitro during reactivation and differentiation of tumor‐specific CD8+ T cells. Using CD8+ T cells from pmel‐1 mice, we observed that the generation of CTLs under 5% O2, which corresponds to physioxia in lymph nodes, gave rise to a higher effector signature than those generated under atmospheric oxygen fractions (21% O2). Hypoxia (1% O2) did not modify cytotoxicity, but decreasing O2 tensions during CTL and CD8+ tumor‐infiltrating lymphocyte reactivation dose‐dependently decreased proliferation, induced secretion of the immunosuppressive cytokine IL‐10, and upregulated the expression of CD137 (4‐1BB) and CD25. Overall, our data indicate that oxygen tension is a key regulator of CD8+ T‐cell function and fate and suggest that IL‐10 release may be an unanticipated component of CD8+ T cell‐mediated immune responses in most in vivo microenvironments.
Simple Azo Dyes Provide Access to Versatile Chiroptical Switches
Authors: Anger Emmanuel , Fletcher Stephen P.
Published: May 2015

Azo dyes have played an important role in the development of the chemical industry for 150 years. The azo‐core of these dyes can undergo trans to cis photoisomerization, which allows azobenzene derivatives to act as light triggered molecular switches. Here, we showed that simple derivatization of Sudan I provides access to chiroptical molecular switches, and that the properties of these switches can be readily tuned by modification of the molecular structure. The synthesis, characterization, photoisomerization, thermal stability, chiral HPLC resolution, determination of absolute configuration and chiroptical properties of chiroptical switches based on Sudan I are reported. ortho‐difluorinated Sudan I derivatives have improved thermal stabilities and switching properties compared to switches based on Sudan I itself. Transfer of stereochemical information from a non‐racemic chiral unit to the π‐conjugated system of the dye and exciton‐coupled circular dichroism are both observed. The chiral unit influences the geometry and hence the spectra of cis and trans‐isomers differently, which is the mechanistic basis of chiroptical switching.
Synergistic effect of mixed methanol/ethanol on transesterification of waste food oil using p‐toluenesulfonic acid as catalyst
Authors: Ma Yingqun , Zheng Lu , Wang Qunhui , Ma Hongzhi , Niu Ruxuan , Gao Zhen
Published: May 2015

In this study, inexpensive waste food oil was used as raw material, the p‐toluenesulfonic acid as catalyst, the methanol/ethanol as a transesterification agent to prepare biodiesel was reported. The results indicated that the mixed methanol/ethanol contributed to improving the biodiesel performance. Specifically, when mole percentage of ethanol in the total alcohol was 30%, the yield reached 99.55%, and heating value reached 40.47 MJ/Kg. It was higher than that of single methanol and single ethanol as transesterification agent, respectively. The concentration of saturated fatty acid esters in the biodiesel were also increased by mixed methanol/ethanol as transesterification agent (i.e. increase in the proportion of H in C/H), resulting in higher biodiesel heating value. The mixed methanol/ethanol also showed a good synergistic effect in the biodiesel preparation process. The solubility of ethanol in oil is superior to that in methanol, and ethanol plays a double role of the cosolvent and the transesterification agent. Methanol weakened the drawbacks of the steric effect and emulsification effect of ethanol. This study showed that the methanol can be partially substituted by ethanol. It reduced not only the dependence on methanol, but also the yield and heating value of biodiesel can be increased. © 2015 American Institute of Chemical Engineers Environ Prog, 34: 1547–1553, 2015
Dental Chatter: Bacterial Cross‐Talk in the Biofilm of the Oral Cavity
Authors: Steinberg Doron
Published: May 2015

Dental biofilms are composed of hundreds of bacterial species. These biofilms are diverse biological structures due to the heterogeneity of the many different types of supports in the oral cavity. The bacteria immobilized in these biofilms are exposed to rapid environmental changes such as pH, temperature, nutrition and anti‐plaque agents. One mode in which these bacteria adapt in the dental biofilm is by quorum sensing. This cell‐cell communication regulates diverse sets of adhesion modes, physiological changes, virulence properties, allowing the bacteria to persist in the dental biofilm under rapid environmental changes. In this review, we will concentrate mostly on the cariogenic bacterium Streptococcus mutans as one of the pivotal microorganisms in the supra‐gingival biofilm that plays a major role in dental caries.
The Regioselectivity of (Dimethylvinylidene)carbene Directed by Aromatic Ring upon the Addition into Aryl Alkenes in the Presence of Other Olefins
Authors: Sheu Jyh‐Horng , Yen Ching‐Fen , Huang Chia‐Wen
Published: May 2015

Regioselective cycloaddition of (dimethylvinylidene)carbene (1) into aryl alkenes in the presence of other olefins is reported. The reaction is presumably controlled by the phenyl group, which forms an aromatic π‐complex with the carbene C‐3 orbital, followed by the selective addition of 1 to the closest phenyl‐substituted double bond. Also, this selectivity is assumed to be attributed to delocalization of aromatic π electrons which increases the electron density of the conjugated carbon‐carbon double bond, thus leading to the facile addition of vinylidenecarbene.
Synthesis of 1‐[(3‐Halo‐1‐Hydroxy‐2‐Propoxy)methyl]uracil and Thymine as Potential Antiviral Agents
Authors: Wang Eng‐Chi , Chen Hour‐Young , Tzeng Cherng‐Chyi
Published: May 2015

3′‐Halogen acyclonucleoside analogs have been prepared. The starting material, benzyl glycidyl ether (5), prepared from eplchlorohydrin and sodium benzyloxidc, underwent ring opening by soft halogen ions to give l‐benzyloxy‐3‐fluoro‐2‐propanol (6), l‐bcnzyloxy‐3‐chloro‐2‐propanol (7), and l‐benzyloxy‐3‐ bromo‐2‐propanol (8) respectively. The treatment of 5 with lithium iodide in the presence of acetic acid provided 1‐benzyloxy‐3‐iodo‐2‐propanol (9). The treatment of 8 with sodium iodide in anhydrous acetone also produced l‐benzyloxy‐3‐iodo‐2‐propanol (9). Chloromethylation of these halohydrins 6‐9 using paraformaldehyde and hydrogen chloride gas produced the chloromcthyl ethers 10‐13. These chloromethyl ethers without further purification were allowed to react with the silylated bases 16‐17, previously prepared by silylating the bases 14‐15 with HMDS in the presence of ammonium sulfate to give 1‐ [(l‐benzyloxy‐3‐halogen‐2‐propoxy)methyl]uracils and thymines 19‐25. The target compounds 26‐33 were obtained respectively after the debcnzylation of 18‐25. Compounds 26, 27, 30 and 31 had no significant cell toxicity in the range of concentrations 0.001‐20 mM. Compounds 26, 27, 28 and 29 have no significant activity against HSV II (for less than 2 mM there is a cytopathic effect). Compounds 30, 31, 32 and 33 show no activity against HSV II virus even at the level 20 mM.
Constituents of Clinopodium Umbrosum
Authors: Lee Shu‐Mei , Lai Jeng‐Shiow , Kuo Yueh‐Hsiung
Published: May 2015

The isolation and identification of fifteen crystalline components from the whole herb of Clinopodium umbrosum (Bieb.) C. Koch (Labiatae) are described. Their structures were determined on the basis of spectral evidence and chemical transformation. These compounds include five steroids (α‐spinasterone, β‐sitosterol, stigmasterol, α‐spinasterol, and α‐spinasteryl‐3‐O‐β‐glucopyranoside), four triterpenoids (3β‐hydroxyurs‐11‐en‐28,13‐olide, betulinic acid, oleanolic acid, ursolic acid), four flavonoids (luteolin, luteolin‐7‐O‐β‐glucopyranoside, apigenin‐7‐O‐β‐glucuronide, and apigenin‐7‐O‐β‐methylglucuronate), and two lignolic acids [3‐(3,4‐dihydroxyphenyl)‐ lactic acid and rosmarinic acid].
Synthesis of 4‐Arylpyridines Containing Electron‐Withdrawing Groups on the Benzene Ring
Authors: Shiao Min‐Jen , Liu Kang‐Hsiuan , Wang Jy‐Shih
Published: May 2015

4‐Arylpyridines 5 that contain electron‐withdrawing groups such as nitrile, methyl ester, fluoride, and trifluoromethyl on the benzene ring were synthesized in moderate yields (29‐63%) by reaction of mixed copper, zinc aryl organometallics 1 with various 1‐(ethoxycarbonyi)pyridinium chlorides 2 followed by o‐chloranil oxidization under reflux in toluene.
The Mean Isomer Degeneracy of the Wiener Index
Authors: Gutman Ivan , Luo Ycung‐Long , Lee Shyi‐Long
Published: May 2015

The mean isomer degeneracy of the Wiener index was previously shown to become unboundedly large as n (the number of vertices of the molecular graphs of the isomers considered) increases. We here show that there is a high isomer degeneracy in the case of molecules of medium size, namely when n = 6 and n = 7.
Exchange Charges and Bond Orders for Homonuclear Diatomic Molecules
Authors: Chang Tse‐Chiang
Published: May 2015

A new bond order definition B = βS2 is defined which relates the bond order B to the non‐classical exchange charges in the bonding region. This definition is successful in correlating the bond order to its bond energy, when the overlap is calculated from a generalized valence‐bond pair function and the parameter β is chosen to be the inverse of bond distance.
Aspergillus Protease‐Catalyzed Esterification at pH > 7
Authors: Tai Dar‐Fu , Chiu Li‐Chun , Huang Ching Chong , Liaw Wen‐Cheng
Published: May 2015

Diverse N‐substituted amino acids were converted to their corresponding esters by crude sucrose‐immobilized Aspergillus oryzae protease in organic solvents at pH 7.5. The front part of captopril S‐(‐)‐acetylthio‐2‐methylpropionic acid and the aspartame precursor Cbz‐L‐Asp‐L‐Phe‐OH also underwent esterification under such conditions.
Indirect Determination of Sulfate by Atomic Absorption Spectrophotometry
Authors: Chang Chur‐Min , Huang Hsuan‐Jung
Published: May 2015

With a flow injection technique, the content of sulfate in solution was determined indirectly from the concentration of partially equilibrated barium ion in solution. To obtain improved sensitivity, atomic absorption spectrophotometry of a flame was used to determine barium. With these procedures combined with a linear calibration graph, superior sensitivity and detection limit of sulfate determination were obtained compared with those from other indirect methods.
Proton Nuclear Magnetic Resonance Measurements of 2′‐Aminodeoxyuridylyl‐3′,5′‐Deoxyuridine
Authors: Kan Lou‐Sing , Bauman Rick , Bhan Purshotam , Miller Paul S.
Published: May 2015

A dideoxyribonucleotide, 2′‐amino‐2′‐deoxyuridylyl 3′,5′‐deoxyuridine, containing an unsual base (2′‐amino‐2′‐deoxyuridine) that isresistant to nucleases was investigated by ′H NMR. The pKa of the protonation of the amino group (5.8) was determined by profiles of chemical shifts of protons in the vicinity of amino group versus pH. However, protonation of the amino group has little effect on the conformation of the dimer, assumed to be B‐form DNA. This conclusion is drawn from the chemical shift data and coupling constants of H1‐H2. Thus, 2′‐amino‐2′‐deoxyuridine can be used in antisense and anticode oligonucleotides.
Photochemistry of Syn‐ and Anti‐A8,9‐Dimethoxycarbonyl‐1,5‐Dipropyl‐3‐Oxatricyclo[3.2.2.02,4]Non‐8‐Ene‐6,7‐Dione
Authors: Liao Chun‐Chen , Lin Ho‐Shen , Tsai Yow‐Fu , Ueng Yih‐Gang
Published: May 2015

In the photochemistry of the title compounds, the anti isomer 6 afforded oxepine 9 whereas the syn isomer yielded 9 and 10; the reactions proceeded partly via cyclobutanediones 12 and 13. The distinct photochemical behavior are explained in terms of stereorelectronic effects of the epoxy rings.
Thermal Decomposition of Fluorinated Dioxolane Carboxylates
Authors: Hung Ming‐H. , Famham Willia M. B.
Published: May 2015

Synthesis of fluorodioxole olefin monomers by thermal decomposition of fluorinated dioxolane carboxylic acid and the corresponding acyl chloride was explored. Complex product formation is observed, including acyl fluoride from Cl‐F exchange, the hydro‐dioxolane from proton abstraction, the cyclic ether ketone from dioxolane ring opening, and the epoxy acid fluoride from thermal rearrangement. The product distribution is strongly dependent upon reaction conditions. The main influential factors include the reaction temperature, the base used for the reaction, the presence or absence of solvent, and the counter ion associated with the intermediate salt. A mechanism is proposed to rationalize both the results and the product distribution. Methods to make authentic samples for product analysis are reported.
The Reaction of 4‐Formylsydnone with Nitroalkanes
Authors: Hung Wei‐Jing , Tien Hsien‐Ju , Yu Hsien‐Cheng
Published: May 2015

Under various basic solutions and reaction durations, 3‐substituted 4‐formyIsydnones and nitroalkanes containing α‐active hydrogen (e.g. nitromethane and nitroethane) are converted to β‐nitroalcohols, nitroalkenes and dinitroalkanes. β‐Nitroalcohols are obtained only by electrochemical reaction on an electrogenerated base (EGB). The mechanism of overall reaction steps in particular is discussed.
An Exchange Charge Model for Covalent Bonds in Simple Homonuclear Diatomic Molecules
Authors: Chang Tse‐Chiang
Published: May 2015

The point charge in Parr's simple bond charge model is replaced by the exchange charge, which can be evaluated according to a simple ab initio method. The calculated exchange charge correlate well with the experimental values of force constants and dissociation energies for homonuclear diatomic molecules H2, Li2, F2, Na2 and Cl2.
Constituents of the Heartwood of Diospyros Eriantha
Authors: Chen Chien‐Chih , Yu Hsi‐Jung , Ou Jun‐Chih , Pan Tzu‐Ming
Published: May 2015

The isolation and identification of fifteen compounds from the heartwood of Diospyros eriantha are described. Their structures were determined on the basis of spectral evidence and/or comparison with authentic samples. These compounds include three steroids (stigmast‐4‐en‐3‐one, stigmast‐4‐ene‐3,6‐dione, and 3β‐hydroxystigmast‐5‐en‐7‐one), seven triterpenoids (friedelin, lupeol, betulinaldehyde, 3β‐acetoxyurs‐11‐en‐13,28‐olide, 3β‐acetoxyoleanolic acid, betulin, and betulinic acid), three quinones (2‐ethoxy‐7‐methyljuglone, 3‐ethoxy‐7‐methyljuglone, and 2,6‐dimethoxy‐1,4‐benzoquinone), and two phenols (3,4,5‐trimethoxyphenol, and syringic acid).
New Pseudostationary Phases for Electrokinetic Chromatography: A High‐Molecular Surfactant and Proteins
Authors: Terabe Shigeru , Ozaki Hiroto , Tanaka Yoshihide
Published: May 2015

To extend the applicability of electrokinetic chromatography (EKC), two new types of pseudostationary phases have been introduced. A high‐molecular surfactant, butyl acrylate/butyl methacrylate/methacrylic acid copolymer (BBMA) is employed as a micellar forming surfactant for miccllar electrokinetic chromatography (MEKC). The critical micelle concentration of BBMA is essentially zero, which means the micellar concentration is constant irrespective of temperature and buffer. Some characteristic features of BBMA as the pseudostationary phase for MEKC is investigated in comparison with conventional ionic surfactants. Ovomucoid and avidin, which are proteins isolated from egg white, have been found to be useful chiral selectors in affinity EKC. A few examples of the separation of enantiomers with these proteins are shown.
Uncharged Co(lll) Complexes: Transfer Chemical Potentials and Base Hydrolysis in Water‐Methanol Mixtures
Authors: Abu‐Gharib Ezz‐Eldin A.
Published: May 2015

Solubilities are reported for three Co(III) complexes of 2‐aminophenol, 2‐amino‐4‐nitrophenol and 6‐amino‐2,4‐dimethylphenol. Transfer chemical potentials have been derived from appropriate solubility measurements in aqueous methanol. The trends in transfer chemical potentials are discussed in terms of the nature of the coordinated ligands and are compared with those for selected of other inorganic Co(III) complex ions. The kinetics of base hydrolysis of Co(III) complexes in aqueous methanol solutions are described and the change in the activation barrier δmΔG≠ is determined. Solvent effects on reactivity trends are analysed into initial state and transition state components. The small decrease in the rate constant, with increasing proportion of methanol, is ascribed to a greater effect of solvent on the initial state.
Mixed Valence Chemistry of Pyrimidine Bridged Binuclear Complex of Pentacyanoferrate and Pentaammineruthenium
Authors: Tsaur Grace , Wu Ming‐Chu , Yen Andrew
Published: May 2015

The pyrimidine bridged binuclear complex (CN)5FepymRu(NH3)5‐ (I) was prepared in aqueous solution by mixing cquimolar of Fe(CN)5OH23− and Ru(NH3)5pym2+. Its mixed valence state molecule (CN)5FepymRu(NH3)5(II) was obtained upon oxidation of I by one equivalent of peroxydisulfate ion. Both binuclear complexes and corresponding Fe(II) and Ru(II) mononuclear complexes displayed a metal‐to‐ligand charge transfer absorption in 400–450 nm region. Rate constants of formation and dissociation of I and II were measured, and the values of kf (−103M−1s−1) and kd (−10−3‐10−4 s−1) were consistent with kinetic results expected for the substitution of Fe(CN)5OH23− with di‐ and trivalent ligands. Cyclic voltammetry of I exhibited two one‐electron steps of oxidation corresponding to [III, L, II] + e → [II, L, II] and [III, L, III] + e → [III, L, II], respectively. The mixed valence binuclear complex II showed an intervalence band at 955 nm with a molar extinction coefficient 5.80 × 102 M−1cm−1 and a half‐width 5100 cm−l. The properties of the IT band conform to Hush's theory. Spectroscopic, electrochemical and kinetic results of II suggest that the mixed valence complex features a trapped ‐ valence formulation with localized oxidation states of Fe(II) and Ru(III).
Hydrogen Chloride Induced Reorganization of Packing Phases in Self‐assembled Monolayers of n‐Alkanoic Acids on Silver Surface
Authors: Tao Yu‐Tai , Ma Li‐Fang
Published: May 2015

A unique reorganization process, which was induced by HCI treatment of the self‐assembled monolayers of n‐alkanoic acids on silver surfaces, was visualized by polarized reflection absorption IR spectroscopy. The process can be reversible or irreversible, depending on the chain length of the monolayer‐forming acid. Thus for C16 acid, the highly oriented and crystalline monolayer packing phase reorganized reversibly into isotropic microcrystallites. For C8 acid, the ordered packing phase reorganized irreversibly into a disordered, liquid‐like phase. For C24 acid, reversible change in orientation occurred. All changes are due to the protonation‐deprotonation reaction occurring at the binding head group.
Monosubstituted Trinuclear and Tetranuclear VIB Metal Carbonyl Complexes: Syntheses of [{M(CO)5}3(Pf‐Pf‐Pf)] [Pf‐Pf‐Pf = PhP(CH2CH2PPh2)2] and [{M(CO)5}4(P‐Pf3)] [P‐Pf3 = P(CH2CH2PPh2)3] (M = Cr, Mo) and Crystal Structures of the Latter Three
Authors: Horng Deng‐Nan , Jeng Shuenn‐Tay , Ueng Chuen‐Her
Published: May 2015

The triligate trimetallic complexes, [{M(CO)5}3(Pf‐Pf‐Pf)] and tetraligate tetrametallic complexes, [{M(CO)5}4(P‐Pf3)] (M = Cr and Mo), were prepared from [M(CO) 6] and the corresponding ligands in MeCN/CH2Cl2 promoted by Me3NO at 0 °C. Crystals of trimer lb are monoclinic, space group P 21/n, with a = 13.407(3), b = 15.002(5), c = 26.52(1) Å, β = 90.65(2)°, Z = 4, and R = 0.060 for 2760 observed reflections. Crystals of tetramer 2a are monoclinic, space group P 21/c, with a – 14.183(8), b = 29.880(4), c = 16.103(2) Å, β = 94.98(3)°, Z = 4, and R = 0.039 for 5014 observed reflections. Crystals of 2b are monoclinic, space group C 2/c, with a = 42.120(8), b = 13.679(1), c = 23.486(2) Å, β = 92.14(1)°, Z = 8, and R = 0.032 for 6897 observed reflections. Each phosphorus atom of the ligands is coordinated to the M(CO)5 moiety in each title compounds. The geometry of the four metals is a distorted tetrahedron for the tetramers.
Pyrazole Derivatives Part III Synthesis of Novel Naphtho[1,2‐c]pyrazolebenzenesulfonylureas, Thioureas and Their Cycllzed Derivatives
Authors: Faidallah Hassan M. , Makki Mohamad S. I.
Published: May 2015

Substituted p‐(naphtho[1,2‐c]pyrazol‐2‐yl)benzenesulfonylurea and thiourea derivatives 5–7 were prepared in three series. Cyclization of the thioureido group of compounds 7 by treating with ethyl bromoacetate, ethyl β‐bromopropionate and α‐bromoacetophenone afforded the corresponding thiazolidinone, thiazinone and thiazoline derivatives 8, 9 and 10 respectively.
Spatial Taming and Trapping of Molecules
Authors: Friedrich Bretislav , Herschbach Dudley
Published: May 2015

Molecular beam techniques for study of collisional and spectroscopic processes have recently been enhanced by use of static electric or magnetic fields to orient or align molecules with permanent dipole moments. A more general method is now in prospect, applicable both to alignment and to spatial trapping of molecules. This exploits the anisotropic interaction of the electric field vector of intense laser radiation with the dipole moment induced in a polarizable molecule by the laser field. The interaction creates directional superpositions of field‐free states that correspond to oblate spheroidal wavefunctions, with eigenenergies that decrease with increasing field strength. We suggest that this polarizability interaction produces the marked alignment found in laser‐induced dissociative ionization of CO by the Saclay group. We also present calculations illustrating the feasibility of spattal trapping. In combination with supermirror focussing and buffer‐gas cooling, an intense infrared laser can typically confine molecules for long‐times (‐hours) within a small (‐picoliter) and cold (−1°K) “pocket of light.”
Picosecond Time Resolved Hard X‐Ray Diffraction from Laser Heated Metallic Crystals
Authors: Chen P. , Tomov I. V. , Rentzepis P. M.
Published: May 2015

We report the development of a novel hard X‐ray diffraction system with picosecond time resolution. Picosecond X‐ray pulses are produced by excitation of an X‐ray diode with picosecond ultraviolet light pulses at a repetition rate of 300 Hz. The X‐ray pulses are synchronized to the optical pulses with picosecond accuracy. The system has been utilized in picosecond time resolved X‐ray diffraction of laser pulse heated gold and platinum single crystals.
Duschinsky Effect in Sum Frequency Generation from Adsorbed Molecules
Authors: Vallet J. C. , Boeglin A. J. , Lavoine J. P. , Villaeys A. A.
Published: May 2015

It is the purpose of this work to give a theoretical description of the role played by the Duschinsky rotation in sum frequency generation experiments performed on adsorbed molecules. In addition to the mode mixing resulting from the Duschinsky rotation, frequency shifts as well as nuclear equilibrium position shifts, occuring under electronic excitation, are incorporated in the present model. The sum frequency generation spectra are calculated in order to compare the effects of the equilibrium position shifts and the quadratic mode mixing.
Modeling of Decay Rates for Molecules at an Island Surface
Authors: Xiong T. , Lcung P. T. , George Thomas F.
Published: May 2015

The decay rates for molecules at rough surfaces are studied via an island surface model, with particular emphasis on the effect due to the distribution of surface roughness. Two extreme cases are studied when the surface islands distribute themselves evenly and when they coalesce to form local clusters at the molecule‐substrate interface. The optical properties of the interfacial layer in these two cases are described by the Maxwell‐Garnett and the fractal‐cluster models, respectively. Among other results, it is found that both enhancement and suppression of the surface‐induced decay rates are possible due to the presence of roughness, with more dramatic suppression taking place when the surface islands coalesce to form clusters.
Chemical Constituents from the Roots of Neolitsea hiiranensis
Authors: Wu Shwu‐Li , Li Wen‐Shyong
Published: May 2015

One triterpenoid, taraxerone (1); four germacrane‐type sesquiterpene lactones, linderane (2), linderalactone (6), pseudoneolinderane (7), (+)‐linderadine (8); one sesquiterpene dilactone, pseudoneoliacine (10); three elemane‐type sesquiterpenes, isolinderalactone (3), compound 4 and sericealactone (9); one eudesmane type sesquiterpene, cryptomeridol (11); one glucoside, β‐sitosterol‐β‐D‐glucoside (12) along with β‐sitosterol (5) were isolated from the roots of Neolitsea hiiranensis. The structures of these compounds were identified on the basis of spectral properties.
Ring Enlargement of N‐Heterocycles
Authors: Liang Xiao‐Tian
Published: May 2015

This review describes our preliminary results of ring enlargement of N‐heterocycles by N‐ylide formation at a targeted site, exemplified by 55→56→58. Before development of this method, the strategy can be traced to our modified Hofmann degradation led at first to several miscarried probings on the reaction between N‐halomethyl ammonium salts and halophilic reagents.
Structural Tailoring of Monomolecular Films on Evaporated Silver Surface
Authors: Tao Yu‐Tai , Chang Shun‐Chi , Ma Li‐Fang
Published: May 2015

Monomolecular films with well‐defined structure were prepared by self‐assembling of n‐alkanoic acids on an evaporated silver surface. Here we report the structural studies of thin films of acids containing aromatic chromophores of varied size and polarity. Information regarding the packing, orientation and conformation of the structural units within the assembly were deduced from ellipsometric thickness measurement, polarized reflection absorption infrared spectra and wetting property measurement. Implications of results to the design of functional thin films are discussed.
Convergent and Stereoselective Synthesis of Sarcophytol‐Q Precursor: (11S)‐3,7,11,15‐Tetramethyl‐11‐hydroxy‐14‐oxo‐3E,7E,12E‐hexadecatrienal
Authors: Li Wei‐Dong , Li Yu‐Lin , Li Ying
Published: May 2015

A chiral precursor of sarcophytol‐Q, (11S)‐3,7,11,15‐tetramethyl‐11‐hydroxy‐14‐oxo‐3E,7E,12E‐hexadecatrienal, was synthesized in a convergent and stereoselective manner starting from geraniol and 4‐hydroxy‐2‐butanone in nine steps. The key steps were asymmetric Sharpless epoxidation, base‐induced dehydrohalogenation rearrangement of chiral epoxy chloride 5 and the phase transfer catalytic coupling reaction of allylic phenyl sulfone 4 with chiral allylic chloride 3.
Non‐Equivalent Hybrid Atomic Orbitals and Covalent Bonds in a2 Molecules
Authors: Chang Tse‐Chiang
Published: May 2015

In addition to having a noninteger value of λ for non‐equivalent hybrid atomic orbitals sp λ the introduction of a noninteger occupation number to a valence configuration for atoms in a molecule renders a precise account of the covalent bond in homonuclear diatomic molecules. For instance, the following bond orders 0.05, 1.42 and 2.62 are obtained for the molecules Be2, B2 and C2 according to the proposed method.
Potentiometric Determination of the Dissociation Constants of Glycylglycine in Various Aquo‐Organic Media
Authors: Azab H. A. , El‐Nady A. M. , Hamed M. M. A. , Ahmed I. T.
Published: May 2015

The dissociation constant values of glycylglycine were determined at 25 ± 0.1 °C (I = 0.1 mol L−1 KNO3) with Potentiometric pH titration in pure water and various mixture of water and organic solvents. The organic solvents used were methanol, ethanol, N, N‐dimethylformamide, dimethylsulfoxide, acetonitrile and dioxane. Initial estimates of the dissociation constants of glycylglycine were refined with ESAP2M computer program. The results obtained are discussed in terms of average macroscopic properties of the mixed solvents and the possible variation in microheterogeneity of the solvation shells around the solute.
Stereoselective Synthesis and Diels‐Alder Reactions of (Z)‐ and (E)‐1,2‐bis(Phenylthio)‐1,3‐Butadiene
Authors: Chou Shang‐Shing P. , Sun Der‐Jen , Hai‐Ping Tai
Published: May 2015

Bromination of 3‐phenylthio‐2‐sulfolene (2) with N‐bromosuccinimide gave 2‐bromo‐3‐phenylthio‐2‐sulfolene (3) which was converted mainly to 2,3‐bis(phenylthio)‐2‐sulfolene (4) by treatment with sodium phenylthiolate. Thermal desulfonylation of 4 at different temperatures in the presence of a base (DBU) yielded stereoselectively the (Z)‐ and (E)‐1,2‐bis(phenylthio)‐1,3‐butadiene (6). These two geometric isomers could be thermally interconverted. The Diels‐Alder reactions of 6 were also investigated. Only the (Z)‐diene 6a could undergo the Diels‐Alder reaction; the (E)‐diene 6b was in situ converted to the Z isomer before undergoing (he Diels‐Alder reaction. The reaction of 6a with N‐phenylmaleimide gave the cycloaddition product 7 with complete endo selectivity, but under daylight or during chromatography it readily underwent a thioallylic rearrangement to yield 8 with inversion of configuration. The cycloaddition of 6a with methyl acrylate proceeded regiospecifically, but generating a mixture of endo and exo isomers. The endo/exo ratio could be increased by using ZnCl2 as the catalyst.
Constituents of Roots of Rubia Lanceolata Hayata
Authors: Kuo Su‐Ching , Chen Pey‐Rin , Lee Shwu‐Woan , Chen Zong‐Tsi
Published: May 2015

A naphthohydroquinone and eight anthraquinones were isolated from the roots of Rubia lanceolata Hayata. Their structures were assigned as mollugin (1), l‐hydroxy‐2‐methyl‐9,10‐anthraquinone (2), 2‐methylquinizarin (3), 3‐carbomethoxy‐l‐hydroxy‐9,10‐anthraquinone (4), lucidin ethyl ether (5), rubiadin (6), alizarin (7), ω‐hydroxypachybasin (8) and digiferruginol (9) on the basis of spectral evidence. Among them, compounds 8 and 9 were isolated for the first time from Rubia species.
Theoretical Calculations of Combination of Hydrogen Atoms
Authors: Shyu Jiann‐Shing
Published: May 2015

A resonance‐complex set was developed to investigate the process of combination of hydrogen atoms with a modified resonance‐complex theory and Monte‐Carlo trajectory method over the temperature range 40‐300 K. The obtained ratios of ortho to para at 300 K and at 77 K agree satisfactorily with experimental results. Unlike previous results, a maximum of the rate coefficient as a function of temperature is found near 150 K.
Synthesis of N‐ (1, 3‐Dimethyl‐1 H‐2, 3‐Dihydrobenzimidazol‐2‐Ylidene) Acetamido Derivatives as Potential Antiarrhythmic Agents
Authors: Al‐Khamees Hamad A.
Published: May 2015

N‐(1,3‐dimethyl‐1H‐2,3‐dihydrobenzimidazol‐2‐y]idene)‐acetamido derivatives were prepared and evaluated for antiarrhythmic activity.
Metal Ion Dependent Binding and Nuclease Activity of Hexaazacyclophane
Authors: Chang Tsu Hsin , Ong Chi Wi , Chou Yi Meen , Chuang Kuo‐Shen , Wang Wen Jwu
Published: May 2015

The HAPP‐Fe complex was more active than HAPP‐Cu complex in cleavage of DNA in the presence of dithiothreitol and hydrogen peroxide. In contrast, the HAPP‐Cu complex was found to bind more strongly with λ‐DNA, whereas the HAPP‐Fe binds weakly. It was shown that the metal ion complexed with HAPP ligand can influence the binding and cleaving activity due to the ability of the ligand to undergo geometrical tautomerization.
Chemistry of Isodrin Derivatives. The Syntheses of 11‐ and 12‐Hydroxy‐1,4,4a,9,9a,10‐Hexahydro‐Endo, Endo‐1,4;9,10‐Dimethano‐Anthracenes
Authors: Chow Tahsin J.
Published: May 2015

The titled compounds are synthesized through multi‐step sequences involving consecutive [n4s + n2s] cycloadditions of norbornadiene with two units of chlorinated cyclopentadiene. A dyotropic double hydrogen migration was observed between two closely located double bonds during the process of aromatization of a cyclohexadiene moiety. A hydroxyl group is introduced onto either of the two methylene bridges in order to provide products suitable for solvolytic analyses.
Optical Nonlinearities of Phthalocyanines and Naphthalocyanines
Authors: Wen Tsai‐Chuan , Jen Shiaw‐Juang , Liu Huei‐Wen , Hwang Long‐Chih , Lian Iu‐De
Published: May 2015

The nonlinear absorption and refraction of soluble phthalocyanines and naphthalocyanines have been measured with z‐scan technique using 8 ns, 532 nm laser pulses. The excited‐state absorption cross‐section and the excited‐state refractive‐index cross section have been estimated under the consideration of laser induced thermal effect. The excited state absorption induced n2 and Re χ(3) values are in the range of 10−12 esu. These observed data are enhanced by the concentrations of both metal substituted Pc's and Nc's, but this increment became very small for the metal free phthalocyanine. During the optical limiting experiments, a 25% linear transmitted solution of R8PcH2 can limit laser pulses to ≤ 120 μJ from incident energies as high as 2.0 mJ, and this limitation moved down to ≤ 50 μJ when replacing R8PcCu from P8PcH2. A similar property has also been observed for the metal substituted naphthalocyanines. The results indicate that both the nonlinear refraction and optical limiting properties should be strongly affected by the metal induced triplet‐state nonlinear absorption in both Pc's and Nc's. Moreover, the laser pulses created a self trapped filament inside the solution of this optical limiter, while emitting time‐resolved, concentric rings on a projection screen, which could be induced by the thermal lensing effect. The various optical nonlinear properties observed from these materials should make them valuable as an optical limiter.
Aminolysis of N‐acyl‐2‐Oxazolidinones with Primary Arylamines
Authors: Wu Ming‐Jung , Tseng Tsung‐Chin
Published: May 2015

The reaction of N‐acyl‐2‐oxazolidinones with aniline and analogs in the presence of 1.1 equiv of T1Cl4 gave the corresponding amides in modest to high yields.
Stereoselectivity of the Diels‐Alder Reaction of (E)‐γ‐Oxo‐α,β‐Unsaturated Thioesters with Cyclopentadiene
Authors: Tsai Shih‐Hwa , Chung Wen‐Sheng , Wu Hsien‐Jen
Published: May 2015

The stereoselectivity of the Diels‐Alder reaction of (E)‐γ‐oxo‐α,β‐unsaturated thioesters 3a‐3d with cyclopentadiene is greatly enhanced in the presence of Lewis acids favoring the endo acyl isomers 4a‐4d. In the absence of Lewis acid, Diels‐Alder reaction of 3a‐3d with cyclopentadiene at 25 °C gave two adducts 4a‐4d and 5a‐5d in a ratio of 1:1 respectively. In the presence of Lewis acids, Diels‐Alder reaction of 3a‐3d with cyclopentadiene gave 4a‐4d and 5a‐5d in ratios of 75‐94:25‐6 respectively. The stereoelectivity was enhanced to ratios of 95‐98:5‐2 with lowering the reaction temperature. The stereochemistry of the cycloadducts 4 and 5 was confirmed by iodocyclization. Reaction of the endo‐thioester 5c with I2 in aqueous THF at 0 °C gave the novel methylthio group rearranged product 6c in 80% yield, the first example of iodo‐lactonization of endo‐thioesters. Reaction of the endo‐acyl isomer 4b with I2 under the same reaction conditions gave an isomeric mixture of 7b and 8b in 1:2 ratio. The stereochemistry of the thioester group in 8b was proved by X‐ray single‐crystal analysis. The solvent effect on the endo selectivity of (Z)‐γ‐oxo‐α,β‐unsaturated thioester 2b was also examined.
Dissociation Kinetics of Nickel (II), Zinc (II) and Cadmium (II) Complexes of 1,7‐Diaza‐4,10,13‐trioxacyclopentadecane‐N,N′‐diacetic Acid and 1,10‐Diaza‐4,7,13,16‐tetraoxacyclooctadecane‐N,N′‐diacetic Acid
Authors: Chang C. Allen
Published: May 2015

The dissociation kinetics of the complexes of nickel(II), zinc(II) and cadmium(II) of 1,7‐diaza‐4,10,13‐trioxacyclopentadecane‐N,N′‐diacetic acid (K21DA) and 1,10‐diaza‐4,7,13,16‐tetraoxacyclooctadecane‐N,N′‐diacetic Acid (K22DA) were studied in constant ionic strength aqueous medium with various [H+]‐range, i.e., (0.88−53.9) × 10−5 M and (0.5−7.5) × 10−3 M. Copper(II) was used as the scavenger of free ligand and the rates of dissociation of these complexes have been found to be independent of (Cu2+]. All the complexes exhibit acid‐independent and acid‐dependent pathways. For NiK21DA, CdK21DA and CdK22DA complexes, the acid‐dependent rates are linear functions of [H+]. For NiK22DA and ZnK21DA complexes, a saturation kinetics is observed, i.e., [H+]‐dependence at low [H+] and [H+]‐independent at high [H+]. The rationalization of such different observations is proposed to be due to difference in complex solution structures rather than the thermodynamic stabilities. Influence of acetate content in the buffer, temperature, and total electrolyte concentration on the rate of dissociation has also been investigated and discussed.
Three Prenylated Isoflavones from Erythrina variegate
Authors: Huang Keh‐Feng , Yen Yuh‐Fang
Published: May 2015

Two new prenylated isoflavones (erythrivarones A and B) were isolated from the stem bark of Erythrina variegata Linn, together with the known compound alpinumisoflavone (1). The structures of erythrivarones A and B were characterized as dihydroalpinumisoflavone (2) and 4′‐hydroxy‐[6″,6″‐dimethyldihydropyrano(2″,3″:5,6)]‐[6‴,6‴‐dimethyldihydropyrano(2‴,3‴:7,8)]isoflavone (3), respectively, by means of spectroscopic analysis.
Bromination of Binor‐S
Authors: Chow Tahsin J. , Chen Yi‐Lung , Lin Kuan‐Jiuh , Wang Yu‐Wen , Li Chun‐Lien
Published: May 2015

Bromination of binor‐S resulted in a mixture of products containing several pairs of isomers. Three major processes were found to be involved in the reaction mechanism, i.e., bromination, hydrobromination, and dehydrobromination. The structures of nine compounds derived from dibromide 6 were identified by spectroscopic methods. Yields between isomers were rationalized by comparison of their relative strain energies calculated by force field model (MM2). The crystal structures of a tribromide (9) and a pentabromide (15) were solved by X‐ray diffraction analyses. Their crystal packing patterns indicated the existence of attractive interactions among the bromine atoms.
Total Synthesis of (±)‐Patriscabrol and (±)‐Boschnialactone
Authors: Chiu Jiun‐Yuh , Chiu Chih‐Tsao , Chang Nein‐Chen
Published: May 2015

A total synthesis of (±)‐patriscabrol (1) and (±)‐boschnialactone (2) is described. The cyclopentapyranone skeleton is assembled by means of Baeyer‐Villiger oxidation of ketol 5.
Satellite Hole Investigation of the Vibrational Modes of 9‐Aminoacridine upon Binding to DNA
Authors: Cheng Ji‐Yen , Chiang Chien‐Chih , Cheng Yah‐Ru , Chen Hsuan‐Shen , Lin Leh‐Jame , Chang Ta‐Chau
Published: May 2015

The spectral features of satellite holes are used to investigate 9‐aminoacridine‐DNA interactions. The hole depths of the outer ring vibronic modes are reduced more than that of the inner ring vibronic modes, implying that inner ring motion is less perturbed than outer ring motion. As a result, the mode coupling between the inner ring and outer ring is reduced upon binding to DNA. However, similar hole frequency and width of the satellite hole corresponding to the NH2 mode upon binding to DNA imply that the amino group of 9‐aminoacridine sits outside the DNA.
A New Approach to the Synthesis of Cortical Steroids
Authors: Shih Ing‐Lung , Hendrickson James B.
Published: May 2015

A new bondset for cortical steroid synthesis is developed from the dual concepts of convergent assembly and multiple construction. A short synthesis on this bondset is presented in which the final bond construction by electrocyclization took an unwanted course. Stereocontrol is discussed separately.
Enantioseparation of Reduced Haloperidol by Capillary Zone Electrophoresis with Dimethyl‐β‐Cyclodextrin
Authors: Wu Hsin‐Lung , Wu Shou‐Mei , Chen Su‐Hwei , Otsuka Koji , Terabe Shigeru
Published: May 2015

Chiral separation of reduced haloperidol (RHP), an optically active metabolite from haloperidol, by capillary electrophoresis is described. RHP was separated on an uncoated capillary with dimethyl‐β‐cyclodextrin (dimethyl‐β‐CD) in Tris phosphate buffer using PEG 6000 as an organic additive. Several parameters affecting the separation of RHP were studied, including pH and concentration of buffer, buffer additive, and concentration of chiral selector. The migration order of the resolved RHP was assigned with reference RHP enantiomers.
Natural Product Chemistry: From Plants to Human
Authors: Tsai Ming‐Daw
Published: May 2015

Conventionally, natural product chemistry deals with the isolation, characterization, and synthesis of compounds from plants. It a broad sense, natural product chemistry may include all fields of biochemistry. Two projects are presented to illustrate the expanded definition of natural product chemistry. One deals with phosphatidylinositol (PI) and the key enzyme involved in its metabolism, PI‐specific phospholipase C. The other project is on the structure‐function relationship of human tumor suppressor p16.
EPR Studies of Photoreduction of Ni/TiO2 Catalysts
Authors: Chien Shu‐Hua , Wei Yu‐Wen , Lin Mau‐Chen
Published: May 2015

Irradiations of Ni/TiO2 catalyst by UV in hydrogen at 77 K produced not only Ni+ ions on the catalyst surface, but also Ni3+ and Ti3+ species in bulk or near the interface between nickel and titania. These photo‐generated species were detected and characterized by low temperature electron paramagnetic resonance (EPR) spectroscopy. Relative spin concentrations of the photogenerated paramagnetic species (Nin+ and Ti3+) varied with the nickel content in titania. A high nickel content in the sample resulted in a high peak intensity ratio of Nin+ to Ti3+. It was found that the photoinduced self‐redox reaction of Ni2+ ions to form Ni+ and Ni3+ ions has a priority over the photoreduction of Ti4+ to Ti3+ ions. The characteristic EPR spectrum of the Ni3+ (3d7) ions with g1 = 2.268, g2 = 2.237, and g3 = 2.045 indicates that the Ni3+ ions are most likely located in the substitutional sites of TiO2, possibly near the surface rutile phase. The Ni+ species (3d9) with g4 = 2.130 and g1 = 2.063 are on the surface of TiO2. Both Ni+ and Ni3+ ions are quite stable in hydrogen. The Ni3+ ions seem to be responsible for anchoring the nickel ions onto titania and stablizing the Ni+ species on the surface. The Ni+ ions are thus free from oxygen poisoning and still show a high activity toward olefin oligomerization.
Mechanistic Studies on the Photogenerated Dienol with α‐Phenyl‐N‐tert‐Butylnitrones
Authors: Pan Kai , Ho Tong‐Ing
Published: May 2015

The mechanism for the photochemical reactions of o‐methyl‐benzaldehyde (1), o‐methyl‐acetophenone (2) and o‐methyl‐benzophenone (3) in the presence of α‐phenyl‐N‐tert‐butylnitrone (PBN) to the formation of stable nitroxyl radicals 4–6 is studied.

The nitroxyl radical product 6 can also be obtained by the thermolysis of benzocyclobutenol with PBN. Thus, the radical products were derived from a novel and regioselective 4+2 cycloaddition of the photogenerated dienol intermediate with PBN.
Synthesis and Properties of 3‐Thia‐9‐azabicyclo[3.3.1]nonan‐7‐one
Authors: Ho Tse‐Lok , Lin Yueh‐Jyh
Published: May 2015

N‐Benzyl‐3‐thia‐9‐aza‐bicyclo[3.3.1]nonan‐7‐one has been prepared from methyl 4‐bromocrotonate by reaction sequence involving sodium sulfide, benzylamine, and Dieckmann condensation. Some spectral and chemical properties of this system are also reported.
One‐Pot Formation of Carbonates from the Reactions of Carbonyl Compounds with Samarium Diiodide and Methyl Chloroformate
Authors: Lu Ling , Fang Jim‐Min , Lee Gene‐Hsiang , Wang Yu
Published: May 2015

Treatment of carbonyl compounds with SmI2 and methyl chloroformate in the presence of molecular sieves provides the cyclic carbonates or biscarbonates of pinacols. This one‐pot reaction proceeds rapidly even with aliphatic ketones. The stereochemistry obtained by this procedure is different from that of conventional pinacolic couplings.