bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct Energy Extraction from Brown Macroalgae‐Derived Alginate by Gold Nanoparticles on Functionalized Carbon Nanotubes
Authors: Hoa Le Quynh , Yoshikawa Hiroyuki , Saito Masato , Ueda Mitsuyoshi , Shibata Toshiyuki , Tamiya Eiichi 
Published: October 2013

AbstractThe viability of employing brown macroalgae as a future renewable energy and chemical resource has so far proven to be challenging because of the low efficiency of the energy extraction process from alginate, which forms the principle, difficult‐to‐degrade component. In contrast to currently employed alginate‐metabolizing microbial approaches, we here extract energy from macroalgae, for the first time, through a fuel cell system that exploits the electrochemical oxidation of alginate by gold nanoparticle‐decorated functionalized carbon nanotubes without any external input of energy. The analyses suggest that the electrochemical oxidation process induces partial oxidation of alginate and, in addition to bioenergy, also yields valuable chemicals, which paves the way for the future production of energy and feedstock materials from inedible biomass.
Platinum Ruthenium Catalysts Supported on Carbon Xerogel for Methanol Electro‐Oxidation: Influence of the Catalyst Synthesis Method
Authors: Alegre Cinthia , Gálvez María Elena , Moliner Rafael , Baglio Vincenzo , Stassi Alessandro , Aricò Antonino Salvatore , Lázaro María Jesús 
Published: October 2013

AbstractA high surface area, highly mesoporous carbon xerogel was synthesised and used as a support in the preparation of platinum–ruthenium catalysts by different synthetic routes. The platinum–ruthenium carbon xerogel catalysts were physico‐chemically characterised and used for the chemical electro‐oxidation of methanol. The synthetic routes pursued included: 1) impregnation with metal chloride precursors and reduction with two different reducing agents: sodium borohydride and formic acid; 2) a microemulsion‐based method and 3) a sulfite complex method, which led to catalysts with different physico‐chemical features that strongly influence their catalytic behaviour towards methanol oxidation. The electro‐oxidation of methanol was found to depend on both the crystal size and the extent of active phase reduction as well as on the platinum concentration on the catalyst surface, which were maximised for the impregnation method and reduction with formic acid.
Acid‐Activated Carbon Materials: Cheaper Alternative Catalysts for the Synthesis of Substituted Quinolines
Authors: López‐Sanz Jesús , Pérez‐Mayoral Elena , Soriano Elena , Omenat‐Morán Delia , Durán Carlos J. , Martín‐Aranda Rosa María , Matos Ines , Fonseca Isabel 
Published: October 2013

AbstractWe describe the first examples of Friedländer reactions efficiently catalyzed by carbon materials. We report herein a series of acidic activated carbon materials, which can be considered as an environmentally friendly, cheaper alternative to the traditional acidic mesoporous silicates or even zeolites for the synthesis of quinolines/quinolones. Textural parameters of the acidic activated carbon materials together with their acidic properties are important factors that affect the reaction selectivity. Some mechanistic details have been addressed by computational calculations.
Conformational Analysis of the Anti‐obesity Drug Lorcaserin in Water: How To Take Advantage of Long‐Range Residual Dipolar Couplings
Authors: Trigo‐Mouriño Pablo , de la Fuente M. Carmen , Gil Roberto R. , Sánchez‐Pedregal Víctor M. , Navarro‐Vázquez Armando 
Published: October 2013

AbstractThe conformational state of 8‐chloro‐1‐methyl‐2,3,4,5‐tetrahydro‐1H‐3‐benzazepine hydrochloride (lorcaserin) in water has been determined on the basis of one‐bond and long‐range CH residual dipolar coupling (RDC) data along with DFT computations and 3JHH coupling‐constant analysis. According to this analysis, lorcaserin exists as a conformational equilibrium of two crown‐chair forms, of which the preferred conformation has the methyl group in an equatorial orientation.
Structure–Property Relationships and 1O2 Photosensitisation in Sterically Encumbered Diimine PtII Acetylide Complexes
Authors: Nolan Deanne , Gil Belén , Wang Longsheng , Zhao Jianzhang , Draper Sylvia M. 
Published: October 2013

AbstractA series of sterically encumbered [Pt(L)(σ‐acetylide)2] complexes were prepared in which L, a dendritic polyaromatic diimine ligand, was held constant (L=1‐(2,2′‐bipyrid‐6‐yl)‐2,3,4,5‐tetrakis(4‐tert‐butylphenyl)benzene) and the cis ethynyl co‐ligands were varied. The optical properties of the complexes were tuned by changing the electronic character, extent of π conjugation and steric bulk of the ethynyl ligands. Replacing electron‐withdrawing phenyl‐CF3 substituents (4) with electron‐donating pyrenes (5) resulted in a red shift of both the lowest‐energy absorption (ΔE=3300 cm−1, 61 nm) and emission bands (ΔE=1930 cm−1, 64 nm). The emission, assigned in each case as phosphorescence on the basis of the excited‐state lifetimes, switched from being 3MMLL′CT‐derived (mixed metal–ligand‐to‐ligand charge transfer) when phenyl/polyphenylene substituents (3, 4, 6) were present, to ligand‐centred 3ππ* when the substituents were more conjugated aromatic platforms [pyrene (5) or hexa‐peri‐hexabenzocoronene (7)]. The novel PtII acetylide complexes 5 and 7 absorb strongly in the visible region of the electromagnetic spectrum, which along with their long triplet excited‐state lifetimes suggested they would be good candidates for use as singlet‐oxygen photosensitisers. Determined by in situ photooxidation of 1,5‐dihydroxynaphthalene (DHN), the photooxidation rate with pyrenyl‐5 as sensitiser (kobs=39.3×10−3 min−1) was over half that of the known 1O2 sensitiser tetraphenylporphyrin (kobs=78.6×10−3 min−1) under the same conditions. Measured 1O2 quantum yields of complexes 5 and 7 were half and one‐third, respectively, of that of TPP, and thus reveal an efficient triplet–triplet energy‐transfer process in both cases.
Conformational Selection in Glycomimetics: Human Galectin‐1 Only Recognizes syn‐Ψ‐Type Conformations of β‐1,3‐Linked Lactose and Its C‐Glycosyl Derivative
Authors: Vidal Paloma , Roldós Virginia , Fernández‐Alonso María del Carmen , Vauzeilles Boris , Bleriot Yves , Cañada F. Javier , André Sabine , Gabius Hans‐Joachim , Jiménez‐Barbero Jesús , Espinosa Juan Félix , Martín‐Santamaría Sonsoles 
Published: October 2013

AbstractThe human lectin galectin‐1 (hGal‐1) translates sugar signals, that is, β‐galactosides, into effects on the level of cells, for example, growth regulation, and has become a model for studying binding of biopharmaceutically relevant derivatives. Bound‐state conformations of Galβ‐C‐(1→3)‐Glcβ‐OMe (1) and its βGal‐(1→3)‐βGlc‐OMe disaccharide parent compound were studied by using NMR spectroscopy (transferred (TR)‐NOESY data), assisted by docking experiments and molecular dynamics (MD) simulations. The molecular recognition process involves a conformational selection event. Although free C‐glycoside access four distinct conformers in solution, hGal‐1 recognizes shape of a local minimum of compound 1, the syn‐Φ/syn‐Ψ conformer, not the structure at global minimum. MD simulations were run to explain, in structural terms, the observed geometry of the complex.
Fe‐Catalyzed One‐Pot Oxidative Cleavage of Unsaturated Fatty Acids into Aldehydes with Hydrogen Peroxide and Sodium Periodate
Authors: Spannring Peter , Yazerski Vital , Bruijnincx Pieter C. A. , Weckhuysen Bert M. , Klein Gebbink Robertus J. M. 
Published: October 2013

AbstractA one‐pot method has been developed for the oxidative cleavage of internal alkenes into aldehydes by using 0.5 mol % of the nonheme iron complex [Fe(OTf)2(mix‐bpbp)] (bpbp=N,N′‐bis(2‐picolyl)‐2,2′‐bipyrrolidine) as catalyst and 1.5 equivalents of hydrogen peroxide and 1 equivalent of sodium periodate as oxidants. A mixture of diastereomers of the chiral bpbp ligand can be used, thereby omitting the need for resolution of its optically active components. The cleavage reaction can be performed in one pot within 20 h and under ambient conditions. Addition of water after the epoxidation, acidification and subsequent pH neutralization are crucial to perform the epoxidation, hydrolysis, and subsequent diol cleavage in one pot. High aldehyde yields can be obtained for the cleavage of internal aliphatic double bonds with cis and trans configuration (86–98 %) and unsaturated fatty acids and esters (69–96 %). Good aldehyde yields are obtained in reactions of trisubstituted and terminal alkenes (62–63 %). The products can be easily isolated by a simple extraction step with an organic solvent. The presented protocol involves a lower catalyst loading than conventional methods based on Ru or Os. Also, hydrogen peroxide can be used as the oxidant in this case, which is often disproportionated by second‐ and third‐row metals. By using only mild oxidants, overoxidation of the aldehyde to the carboxylic acid is prevented.
The Isolation of Single MMX Chains from Solution: Unravelling the Assembly–Disassembly Process
Authors: Azani Mohammad‐Reza , Paz Alejandro Pérez , Hermosa Cristina , Givaja Gonzalo , Gómez‐Herrero Julio , Mas‐Ballesté Rubén , Zamora Felix , Rubio Angel 
Published: October 2013

AbstractHerein, we provide a systematic theoretical and experimental study of the structural and optical properties of MMX (M=metal, X=halide) chains. The influence of solvent, temperature, and concentration has been analyzed to find suitable parameters for initial building‐block associations in solution. By using density functional calculations, we have computed the dissociation energy of different MMX oligomers (up to the tetramer) in the gas phase. On the basis of these findings, we discuss the most likely disassembly scenario and propose a new interpretation of these compounds. We also calculated the charge redistribution that occurs upon MM+XMMX binding in vacuum. Time‐dependent density functional theory (TDDFT) is used to calculate the UV/visible spectra of different MMX chains up to the tetramer in the gas phase. The implications of these theoretical findings in the analysis of our experiments are discussed in the text. The overall body of data presented suggests a new way of looking at such linear structures. By taking into account these new data, we have been able to isolate single/few MMX chains on mica.
Lyotropic Liquid Crystal to Soft Mesocrystal Transformation in Hydrated Salt–Surfactant Mixtures
Authors: Albayrak Cemal , Barım Gözde , Dag Ömer 
Published: October 2013

AbstractHydrated CaCl2, LiI, and MgCl2 salts induce self‐assembly in nonionic surfactants (such as C12H25(OCH2CH2)10OH) to form lyotropic liquid‐crystalline (LLC) mesophases that undergo a phase transition to a new type of soft mesocrystal (SMC) under ambient conditions. The SMC samples can be obtained by aging the LLC samples, which were prepared as thin films by spin‐coating, dip‐coating, or drop‐casting of a clear homogenized solution of water, salt, and surfactant over a substrate surface. The LLC mesophase exists up to a salt/surfactant mole ratio of 8, 10, and 4 (corresponding to 59, 68, and 40 wt % salt/surfactant) in the CaCl2, LiI, and MgCl2 mesophases, respectively. The SMC phase can transform back to a LLC mesophase at a higher relative humidity. The phase transformations have been monitored using powder X‐ray diffraction (PXRD), polarized optical microscopy (POM), and FTIR techniques. The LLC mesophases only diffract at small angles, but the SMCs diffract at both small and wide angles. The broad surfactant features in the FTIR spectra of the LLC mesophases become sharp and well resolved upon SMC formation. The unit cell of the mesophases expands upon SMC transformation, in which the expansion is largest in the MgCl2 and smallest in the CaCl2 systems. The POM images of the SMCs display birefringent textures with well‐defined edges, similar to crystals. However, the surface of the crystals is highly patterned, like buckling patterns, which indicates that these crystals are quite soft. This unusual phase behavior could be beneficial in designing new soft materials in the fields of phase‐changing materials and mesostructured materials, and it demonstrates the richness of the phase behavior in the salt–surfactant mesophases.
New Reactions of N‐tert‐Butylimines; Formation of N‐Heterocycles by Methyl Radical Elimination on Flash Vacuum Thermolysis of N‐Benzylidene‐ and N‐(2‐Pyridylmethylidene)‐tert‐butylamines
Authors: Vu Thien Y , Chrostowska Anna , Huynh Thi Kieu Xuan , Khayar Saïd , Dargelos Alain , Justyna Katarzyna , Pasternak Beata , Leśniak Stanisław , Wentrup Curt 
Published: October 2013

AbstractThermal reactions of N‐benzylidene‐ and N‐(2‐pyridylmethylidene)‐tert‐butylamines (5 and 13) under FVT conditions have been investigated. Unexpectedly, at 800 °C, compound 5 yields 1,2‐dimethylindole and 3‐methylisoquinoline. In the reaction of 13 at 800 °C, 3‐methylimidazo[1,5‐a]pyridine was obtained as the major product. Mechanisms of these reactions have been proposed on the basis of DFT calculations. Furthermore, UV‐photoelectron spectroscopy combined with FVT has been applied for direct monitoring and characterization of the thermolysis products in situ.
Conformational Diversity in Contryphans from Conus Venom: cis–trans Isomerisation and Aromatic/Proline Interactions in the 23‐Membered Ring of a 7‐Residue Peptide Disulfide Loop
Authors: Sonti Rajesh , Gowd Konkallu Hanumae , Rao K. N. Shashanka , Ragothama Srinivasarao , Rodriguez Alex , Perez Juan Jesus , Balaram Padmanabhan 
Published: October 2013

AbstractConformational diversity or “shapeshifting” in cyclic peptide natural products can, in principle, confer a single molecular entity with the property of binding to multiple receptors. Conformational equilibria have been probed in the contryphans, which are peptides derived from Conus venom possessing a 23‐membered cyclic disulfide moiety. The natural sequences derived from Conus inscriptus, GCVDLYPWC* (In936) and Conus loroisii, GCPDWDPWC* (Lo959) differ in the number of proline residues within the macrocyclic ring. Structural characterisation of distinct conformational states arising from cis–trans equilibria about Xxx–Pro bonds is reported. Isomerisation about the C2–P3 bond is observed in the case of Lo959 and about the Y5–P6 bond in In936. Evidence is presented for as many as four distinct species in the case of the synthetic analogue V3P In936. The Tyr‐Pro‐Trp segment in In936 is characterised by distinct sidechain orientations as a consequence of aromatic/proline interactions as evidenced by specific sidechain–sidechain nuclear Overhauser effects and ring current shifted proton chemical shifts. Molecular dynamics simulations suggest that Tyr5 and Trp7 sidechain conformations are correlated and depend on the geometry of the Xxx–Pro bond. Thermodynamic parameters are derived for the cis↔ trans equilibrium for In936. Studies on synthetic analogues provide insights into the role of sequence effects in modulating isomerisation about Xxx–Pro bonds.
A Theoretical DFT‐Based and Experimental Study of the Transmetalation Step in Au/Pd‐Mediated Cross‐Coupling Reactions
Authors: Hansmann Max M. , Pernpointner Markus , Döpp René , Hashmi A. Stephen K. 
Published: October 2013

AbstractIn this work a combined theoretical and experimental investigation of the cross‐coupling reaction involving two metallic reaction centers, namely gold and palladium, is described. One metal center (Au) hereby is rather inert towards change in its oxidation state, whereas Pd undergoes oxidative insertion and reductive elimination steps. Detailed mechanistic and energetic studies of each individual step, with the focus on the key transmetalation step are presented and compared for different substrates and ligands on the catalytic Pd center. Different aryl halides (Cl, Br, I) and aryl triflates were investigated. Hereby the nature of the counteranion X turned out to be crucial. In the case of X=Cl and L=PMe3 the oxidative addition is rate‐determining, whereas in the case of X=I the transmetalation step becomes rate‐determining in the Au/Pd‐cross‐coupling mechanism. A variety of Au–Pd transmetalation reaction scenarios are discussed in detail, favoring a transition state with short intermetallic Au–Pd contacts. Furthermore, without a halide counteranion the transmetalation from gold(I) to palladium(II) is highly endothermic, which confirms our experimental findings that the coupling does not occur with aryl triflates and similar weakly coordinating counteranions—a conclusion that is essential in designing new Au–Pd catalytic cycles. In combination with experimental work, this corrects a previous report in the literature claiming a successful coupling potentially catalytic in both metals with weakly coordinating counteranions.
Design of Glycosyltransferase Inhibitors: Pyridine as a Pyrophosphate Surrogate
Authors: Wang Shuai , Cuesta‐Seijo Jose A. , Lafont Dominique , Palcic Monica M. , Vidal Sébastien 
Published: October 2013

AbstractA series of ten glycosyltransferase inhibitors has been designed and synthesized by using pyridine as a pyrophosphate surrogate. The series was prepared by conjugation of carbohydrate, pyridine, and nucleoside building blocks by using a combination of glycosylation, the Staudinger–Vilarrasa amide‐bond formation, and azide–alkyne click chemistry. The compounds were evaluated as inhibitors of five metal‐dependent galactosyltransferases. Crystallographic analyses of three inhibitors complexed in the active site of one of the enzymes confirmed that the pyridine moiety chelates the Mn2+ ion causing a slight displacement (2 Å) from its original position. The carbohydrate head group occupies a different position than in the natural uridine diphosphate (UDP)–Gal substrate with little interaction with the enzyme.
Fluorescent Protein Capped Mesoporous Nanoparticles for Intracellular Drug Delivery and Imaging
Authors: Yang Xinjian , Li Zhenhua , Li Meng , Ren Jinsong , Qu Xiaogang 
Published: October 2013

AbstractA multifunctional system for intracellular drug delivery and simultaneous fluorescent imaging was constructed by using histidine‐tagged, cyan fluorescent protein (CFP)‐capped magnetic mesoporous silica nanoparticles (MMSNs). This protein‐capped multifunctional nanostructure is highly biocompatible and does not affect cell viability or proliferation. The CFP acts not only as a capping agent, but also as a fluorescent imaging agent. The nanoassembly was activated by histidine‐based replacement, leading to release of drug molecules encapsulated in the nanopores into the bulk solution. The fluorescent imaging functionality would allow noninvasive tracking of the nanoparticles in the body. By combining the drug delivery with cell‐imaging capability, these nanoparticles may provide valuable multifunctional nanoplatforms for biomedical applications.
Pyridine‐Enhanced Head‐to‐Tail Dimerization of Terminal Alkynes by a Rhodium–N‐Heterocyclic‐Carbene Catalyst
Authors: Rubio‐Pérez Laura , Azpíroz Ramón , Di Giuseppe Andrea , Polo Victor , Castarlenas Ricardo , Pérez‐Torrente Jesús J. , Oro Luis A. 
Published: October 2013

AbstractA general regioselective rhodium‐catalyzed head‐to‐tail dimerization of terminal alkynes is presented. The presence of a pyridine ligand (py) in a Rh–N‐heterocyclic‐carbene (NHC) catalytic system not only dramatically switches the chemoselectivity from alkyne cyclotrimerization to dimerization but also enhances the catalytic activity. Several intermediates have been detected in the catalytic process, including the π‐alkyne‐coordinated RhI species [RhCl(NHC)(η2‐HCCCH2Ph)(py)] (3) and [RhCl(NHC){η2‐C(tBu)C(E)CHCHtBu}(py)] (4) and the RhIII–hydride–alkynyl species [RhClH{CCSi(Me)3}(IPr)(py)2] (5). Computational DFT studies reveal an operational mechanism consisting of sequential alkyne CH oxidative addition, alkyne insertion, and reductive elimination. A 2,1‐hydrometalation of the alkyne is the more favorable pathway in accordance with a head‐to‐tail selectivity.
Thiepin‐Fused Heteroacenes: Simple Synthesis, Unusual Structure, and Semiconductors with Less Anisotropic Behavior
Authors: Cai Zhengxu , Zhang Hantang , Geng Hua , Liu Zitong , Yang Sifen , Luo Hewei , Jiang Lang , Peng Qian , Zhang Guanxin , Chen Jianming , Yi Yuanping , Hu Wenping , Zhang Deqing 
Published: October 2013

AbstractThe simple one‐pot syntheses of sulfur‐rich thiepin‐fused heteroacences with an alkylidene–fluorene framework, THA1 and THA6 (thiepin‐fused heteroacene 1 or 6, in which the thiepin is conjugated at both ortho positions with SCH3 or SC6H13, respectively), is reported. Based on electrochemical studies and theoretical calculations, their LUMO energies are relatively low (−3.26 eV), and their HOMO and HOMO−1 orbitals are nearly degenerate. The thiepin ring contributes mainly to HOMO−1 and LUMO orbitals, however, HOMO orbitals dominantly reside on thienoacence rings. Within the crystal of THA1, the molecules adopt a herringbone arrangement and multiple intermolecular interactions lead to the formation of a 2D network. Interestingly, THA6 shows totally different intermolecular arrangements. Organic field‐effect transistor (OFET) devices show both compounds exhibiting p‐type semiconducting behavior. Thin films or microcrystals of THA1 possess relatively high hole mobility. Moreover, the mobilities of the microcrystal of THA1 along three directions are in the same order, thus the hole‐carrier transporting within the hexagonal‐plane of microcrystal of THA1 exhibits less anisotropic behavior. In comparison, both thin films and microrods of THA6 show low hole mobilities. This agrees well with the intermolecular arrangements and interactions within crystal of THA6. Further theoretical calculations reveal that significant intermolecular electronic coupling among HOMO−1 orbitals and sulfur atoms play an important role in intermolecular electronic coupling for THA1.
Linear and Cyclic Hybrids of Alternating Thiophene–Amino Acid Units: Synthesis and Effects of Chirality on Conformation and Molecular Packing
Authors: Ngo Thien H. , Berndt Hülya , Wilsdorf Michael , Lentz Dieter , Reissig Hans‐Ulrich 
Published: October 2013

AbstractThe dipeptide isostere 5‐aminothiophene carboxylic acid has been combined with L‐phenylalanine moieties to provide linear and cyclic hybrid oligopeptides. A suitable protecting group strategy and appropriate coupling methods have been developed to guarantee a high degree of enantiopurity of the resulting amides. Cyclic tetraamides have been efficiently obtained by macrocyclization of the linear derivatives. In the case of racemized cyclization precursors, two diastereomeric macrocycles (S,S/R,R and meso) have been isolated. Their crystal structures show clear effects of the stereogenic centers on the ring conformations and molecular packing.