bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photosensitization of composite metal oxide semiconductor films
Authors: Bedja I. , Hotchandani S. , Kamat P. V. 
Published: July 2012

AbstractNew approach of surface modification consisting on mixing SnO2 and TiO2 colloids and packing them as a composite film (SnO2‐TiO2) on a conducting glass surface has led to the increased sensitized photocurrent quantum yields. The photoinjected electrons from the sensitizer into TiO2 are quickly transferred into lower lying conduction band of SnO2 carriers thus promoting the charge separation. High internal photocurrent quantum yield for CdS film as sensitizer, approaching unity (φ = 95%), has been obtained. In addition, composite SnO2‐TiO2 nanocrystalline films improve the charge separation in adsorbed bis(2,2′‐bipyridine)(2,2′‐bipyridine‐4,4′‐dicarboxylic acid) ruthenium complex (Ru(II)) too. Higher internal photocurrent quantum yield (φ = 92%) has been obtained for Ru(II) by replacing SnO2 carriers against composite SnO2‐TiO2 particles in the film. On the other hand, the later composition does not show any increase in the photovoltage.
Synthesis, morphology and optical properties of thiol‐stabilized CdTe nanoclusters in aqueous solution
Authors: Rogach A. L. , Katsikas L. , Kornowski A. , Su D. , Eychmüller A. , Weller H. 
Published: July 2012

AbstractThiol‐stabilized CdTe nanoclusters with sizes ranging from 1.3 to 2.4 nm have been prepared in aqueous solution and separated as oxidize‐stable powders. Investigation of CdTe nanoclusters by means of X‐ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) indicates the cubic (zincblende phase) CdTe crystalline structure. Pronounced electronic transitions in the absorption spectra are shifted dramatically towards higher energies in comparison with bulk CdTe as a consequence of quantum confinement in nanosized CdTe particles. Two kinds of size‐ and surface‐dependent photoluminescence (“excitonic” and trapped) of CdTe nanoclusters in aqueous solution were observed. A further growth of CdTe nanoclusters leads to a shift of both absorption edge and “excitonic” photoluminescence band towards longer wavelengths.
Colloids and polymers: Amphiphilic block copolymers
Authors: Förster Stephan 
Published: July 2012

AbstractAmphiphilic block copolymers self‐assemble into a variety of mesoscopic structures comprising micellar and ordered continuous topologies. Size and topology of these structures can be controlled by variation of block lengths. Their stability allows the preparation of well‐defined polymer/inorganic hybrid materials. Quantum‐size semiconductor colloids as well as nanometer‐sized noble metal colloids can be prepared within block copolymer microdomains. Enhanced stability of such colloids allows to use them as efficient catalysts.
Synthesis, structure and properties of coagulated ultrathin membranes
Authors: Rehage Heinz , Achenbach Barbara , Kaplan Adnan 
Published: July 2012

AbstractThe Coulomb interactions between charged surfactants and multivalent counter‐ions can be used to form coagulated cross‐linked membranes at the surface of water. We have systematically measured the kinetics of the two‐dimensional gelation and the rheological properties of the stabilized films. The membranes, thus prepared, exhibit striking rubber‐elastic features. The results of Brewster‐Angle‐Microscopy indicate that these films consist of disc‐like aggregates, having typical diameters of about 10 μm. These particles are in close contact and form fractal network clusters. The shape of these structures is in general agreement with aggregates calculated from percolation theories.
Nanocrystalline materials: Nanocrystalline metals and oxides I: Pulsed electrodeposition
Authors: Natter H. , Schmelzer M. , Janßen S. , Hempelmann R. 
Published: July 2012

AbstractThree preparation routes are presented which, in a simple and cheap way, allow to produce rather large amounts of nanocrystalline solids with controlled particle sizes and narrow particle size distributions: the pulsed electrodeposition for nanocrystalline metals and alloys (this contribution), and the precipitation in microemulsions of nanocrystalline metal fluorides as well as the sol‐gel type hydrolysis in microemulsions for nanocrystalline metal oxides (next contribution).By means of pulsed electrodeposition we have prepared n‐Pd, n‐Cu, n‐Ni, n‐Co and n‐Fe as well as n‐Ni‐Cu and n‐Ni‐Fe alloys. The particle sizes are analysed preferentially using scattering methods; further characterisations concern chemical analyses and density or porosity measurements, respectively. The thermal stability is remarkable; grain growth is not detectable below 150°C.As an example of a particular physical property we present the very fast hydrogen diffusion in nanocrystalline Pd as investigated by means of quasielastic neutron scattering, an experimental technique which requires large amounts of sample.
“NiSn” — A nanostructured compound
Authors: Schwitzgebel G. , Mildenberger R. 
Published: July 2012

AbstractThe recent finding that “NiSn” is composed of Ni3Sn2 with additions of Ni3Sn4 and a Sn(II) compound, SnO or Sn(OH)2, permits to develop a refined model of its structure and stability. The mean grain diameter was determined by STM (15 nm) with a rather small variance. Electrode potentials could be measured in a fused salt mixture of SnCl2 and KC1 between 240 and 300°C. Their evolution with time was consistently interpreted by assuming a solid state separation of Ni3Sn4 from the Ni‐deficient metastable phase Ni3‐δSn2. This model is in good agreement with earlier results of excess enthalpies and XRD changes measured during the recrystallization process.
NMR investigations of nanostructured ceramics
Authors: Edgar M. , Schubert M. , Limbach H. H. , Göltner C. G. 
Published: July 2012

AbstractNanostructured mesoporous silicates displaying hexagonally arranged channels, templated using a liquid crystal mesophase, were investigated using H‐2 and N‐15 NMR spectroscopy. It is shown that N‐15 MAS NMR spectroscopy allows to estimate the surface acidity of mesoporous materials by measuring the N‐H bond length via the N‐15 chemical shift. Further, H‐2 and N‐15 NMR spectroscopy identify significant differences between the structure of the surface area of HI, silica and MCM‐41. Static N‐15 NMR spectroscopy was used to differentiate between pyridine located in channels perpendicular to the magnetic field from, for example, pyridine located in channels orientated parallel to the field. This observation offers the possibility of separating the NMR signals and thus pursuiting the goal of “liquid phase single crystal NMR spectroscopy”.
Density functional study of model species for nucleic acids and lipids
Authors: Hill Jörg‐Rüdiger , Liang Congxin 
Published: July 2012

AbstractDensity functional calculations for dimethylphosphate, methylpropylphosphate, 1‐methylphosphoryl‐2‐acetoxy‐propane, and methylphosphorylcholine which can serve as model species for nucleic acids and lipids were carried out. The VWN, BPW91, BLYP, and ACM functionals have been used and the results are compared with results obtained within the Hartree‐Fock and MP2 approximations and, where available, with observed data. Conformational energies are generally in good agreement with MP2 results for the BPW91, BLYP, and ACM functionals if no intramolecular hydrogen bonds are present. The performance of the VWN functional is not satisfying. Geometries can be predicted with all tested functionals reasonably well and are closer to observed values than Hartree‐Fock results.
The thermally induced phase transition in 2,3,7,8‐tetramethoxythianthrene
Authors: Sanchis M. J. , Marthe S. , Calleja R. Díaz , Martínez E. Sánchez , Epple M. , Klar G. 
Published: July 2012

Abstract2,3,7,8‐Tetramethoxythianthrene is known to crystallize in orthorhombic and monoclinic polymorphs, depending on the solvent used for crystallization. Upon heating the orthorhombic form to ca. 150°C, an enantiotropic (reversible) phase transition into the monoclinic phase occurs. This phase transition has been characterized by different techniques: differential scanning calorimetry (DSC), temperature‐resolved X‐ray powder diffractometry (TXRD), and thermally stimulated depolarization current measurements (TSDC). A mechanism for this solid‐state transition is proposed based on single‐crystal X‐ray structures.
A laser flash photolysis study of the decay of Cl‐Atoms and Cl2− radical anions in aqueous solution at 298 K
Authors: Jacobi H.‐W. , Herrmann H. , Zellner R. 
Published: July 2012

AbstractThe rate coefficient for the reaction of Cl atoms with (1) H2O and of Cl2− radical anions with (2) H2O and (3) OH− have been determined using laser photolysis for the generation of Cl/Cl2− and long path laser absorption for the time resolved detection of Cl2−. The following results were obtained: k1 = (2.3 + 0.6)· 105 s−1, k2 < 610s−1 and k3 = (4.0 + 0.6)· 106M−1s−1. It is concluded that the lifetime of Cl/Cl2− in aqueous solution strongly depends on the Cl− content and on pH.
Dielectric relaxation of aqueous solutions of ribonuclease A in the absence and presence of urea
Authors: Abou‐Aiad T. , Becker U. , Biedenkap R. , Brengelmann R. , Elsebrock R. , Hinz H.‐J. , Stockhausen M. 
Published: July 2012

AbstractThe dielectric spectra of aqueous solutions of ribonuclease A (RNase) have been measured in the frequency domain over the whole absorption region between 2 MHz and 72 GHz at 20°C in two solvents, pure water and 8 mol/1 urea solution. These environmental conditions promote the native and unfolded state of the protein, respectively. The results are discussed with regard to (i) the low and (ii) the high frequency part of the spectra. The contribution to (i) which is attributable to the tumbling motion of RNase is changed by the presence of urea, indicating that the RNase moieties are increased in polarity, but only insignificantly in size. From (ii) it is concluded that addition of urea leads to a change in the overall water structure and dynamics which is accompanied by an increased fraction of non‐associated solvent molecules. These are likely to be instrumental in the denaturation process.
A novel catanionic surfactant: Hexadecyltrimethylammonium dodecyl sulfate
Authors: Tomašić V. , Popović S. , Tušek‐Božić Lj. , Pucić I. , Filipović‐Vinceković N. 
Published: July 2012

AbstractThe novel catanionic surfactant, hexadecyltrimethylammonium dodecyl sulfate, was prepared from the equimolar aqueous solutions of cationic, hexadecyltrimethylammonium bromide, and anionic, sodium dodecyl sulfate, surfactants. The composition, structure, morphology and thermal behavior of new compound were determined by chemical, X‐ray diffraction, IR and 1H NMR spectra analyses, differential scanning calorimetry, thermogravimetry and polarizing microscopy.The thermal behavior of solid crystalline CTADS is rather complex because of its polymorphism, thermotropic mesomorphism and coexistence of ordered and disordered phases below the melting temperature. There are two parallel mechanisms during heating: structural transition of the system and transition from solid crystalline to liquid crystalline phase.Several polymorphic phases, all of the bilayered structure, were observed exhibiting a change of the basic lamellar thickness with temperature. Polarizing microscopy revealed a characteristic texture of the smectic phase.
Dynamic and thermodynamic aspects of polymer‐surfactant interactions: The SDS‐PVP‐water system
Authors: Persi Livio , la Mesa Camillo , D'Aprano Alessandro 
Published: July 2012

AbstractThe water‐PVP (polyvinylpyrrolidone)‐SDS (sodium dodecylsulfate) system has been investigated by ultrasonic relaxation measurements. In water‐PVP mixtures the relaxation time is independent on the polymer content, whereas in water‐SDS solutions it decreases on increasing the amount of surfactant in micellar form. In the ternary water‐PVP‐SDS systems, at fixed PVP content, three different regions have been observed on increasing the amount of SDS: namely, at very low surfactant content the relaxation time, τ, increases then remains nearly constant and finally decreases. The above behaviour has been ascribed to surfactant binding onto the polymer and to micelle formation, respectively. By analysing the dependence of relaxation time(s) on composition, it was possible to divide the investigated region in three domains (i.e. non interaction region, polymer‐surfactant interaction region and micellar region). A phase diagram for the above system was drawn according to the experimental kinetic results. From the data obtained by ultrasonic relaxation experiments the number of SDS molecules bound to PVP, (m), was evaluated and the Gibbs energy of binding, [ΔGbind/<m>], calculated.
Hollow fiber‐based liquid membrane microextraction combined with high‐performance liquid chromatography for extraction and determination of trimetazidine in human plasma
Authors: Lv Jiang , Zhao Xu , Ye Jing , Liu Dan , Chen Xiaohui , Bi Kaishun 
Published: July 2012

ABSTRACTA hollow fiber‐based liquid phase microextraction strategy combined with high‐performance liquid chromatography was evaluated for the quantitative determination of trimetazidine in human plasma. Trimetazidine was extracted from a 2.1 mL basified plasma sample (donor phase) into the organic solvent (n‐octanol) impregnated in the pores of a hollow fiber and then extracted into an acidic solution (acceptor phase) inside the lumen of the hollow fiber. The result showed that transport of drugs from alkaline sample solution into 0.5 m HCl occurred efficiently when 25 μL of 250 mm sodium 1‐octanesulfonate was added into the donor phase. Several parameters influencing the efficiency of the method, such as the nature of organic solvent used to impregnate the membrane, compositions of donor phase and acceptor phase, type and concentration of carrier, extraction time, stirring rate and salt concentration, were investigated and optimized. Under the optimal conditions, the calibration curves were obtained in the range of 5–200 ng/mL with reasonable linearity (r > 0.9980). The method was successfully applied to determine the concentration of trimetazidine in human plasma. Copyright © 2012 John Wiley & Sons, Ltd.
Stereochemistry of Molecular Figures‐of‐Eight
Authors: Boyle Megan M. , Gassensmith Jeremiah J. , Whalley Adam C. , Forgan Ross S. , Smaldone Ronald A. , Hartlieb Karel J. , Blackburn Anthea K. , Sauvage Jean‐Pierre , Stoddart J. Fraser 
Published: July 2012

AbstractA trans isomer of a figure‐of‐eight (Fo8) compound was prepared from an electron‐withdrawing cyclobis(paraquat‐p‐phenylene) derivative carrying trans‐disposed azide functions between its two phenylene rings. Copper(I)‐catalyzed azide–alkyne cycloadditions with a bispropargyl derivative of a polyether chain, interrupted in its midriff by an electron‐donating 1,5‐dioxynaphthalene unit acting as the template to organize the reactants prior to the onset of two click reactions, afforded the Fo8 compound with Ci symmetry. Exactly the same chemistry is performed on the cis‐bisazide of the tetracationic cyclophane to give a Fo8 compound with C2 symmetry. Both of these Fo8 compounds exist as major and very minor conformational isomers in solution. The major conformation in the trans series, which has been characterized by X‐ray crystallography, adopts a geometry which maximizes its CH⋅⋅⋅O interactions, while maintaining its π⋅⋅⋅π stacking and CH⋅⋅⋅π interactions. Ab initio calculations at the M06L level support the conformational assignments to the major and minor isomers in the trans series. Dynamic 1H NMR spectroscopy, supported by 2D 1H NMR experiments, indicates that the major and minor isomers in both the cis and trans series equilibrate in solution on the 1H NMR timescale rapidly above and slowly below room temperature.
ChemInform Abstract: Fluoride‐Ion Acceptor Properties of WSF4: Synthesis, Characterization, and Computational Study of the WSF‐5 and W2S2F9‐ Anions and 19F NMR Spectroscopic Characterization of the W2OSF9‐ Anion.
Authors: Nieboer Jared , Haiges Ralf , Hillary William , Yu Xin , Richardet Tyler , Mercier Helen P. A. , Gerken Michael 
Published: July 2012

AbstractThe new compound (III) is synthesized by reaction of (I) and (II) (yield given in g) and directly from (IV) using the new sulfide‐transfer reagent (V).
ChemInform Abstract: A New Electronically Deficient Atropisomeric Diphosphine Ligand (S)‐CF3O‐BiPhep and Its Application in Asymmetric Hydrogenation.
Authors: Zhang De‐Yang , Yu Chang‐Bin , Wang Min‐Can , Gao Kai , Zhou Yong‐Gui 
Published: July 2012

AbstractThe biphenyl ligand is successfully applied to the hydrogenation of quinoline and indole derivatives.
ChemInform Abstract: A Carbaboranylmercuric Salt Catalyzed Reaction: Highly Regioselective Cycloisomerization of 1,3‐Dienes.
Authors: Yamamoto Hirofumi , Sasaki Ikuo , Shiomi Shinya , Yamasaki Naoto , Imagawa Hiroshi 
Published: July 2012

AbstractThe title salt efficiently promotes the formation of pyrrolidine, piperidine, indole, quinoline, isoquinoline, and tetrahydronaphthalene derivatives.
ChemInform Abstract: Catalyst‐Free Approach for Solvent‐Dependent Selective Oxidation of Organic Sulfides with Oxone.
Authors: Yu Bing , Liu An‐Hua , He Liang‐Nian , Li Bin , Diao Zhen‐Feng , Li Yu‐Nong 
Published: July 2012

AbstractThe oxidation of sulfides (I) with Oxone in ethanol leads to sulfoxides (II), while the oxidation in water affords sulfones (III) in high yields.
ChemInform Abstract: Iodine(III)‐Promoted Intermolecular Diamination of Alkenes.
Authors: Souto Jose A. , Gonzalez Yolanda , Iglesias Alvaro , Zian Debora , Lishchynskyi Anton , Muniz Kilian 
Published: July 2012

AbstractThe bis(mesyl)amines are conveniently deprotected by treatment with Red‐Al.
ChemInform Abstract: Novel Synthesis of 1,2,4‐Triazolophanes and 1,3,4‐Oxadiazolophanes: A Dieckmann Condensation Approach.
Authors: Chande Madhukar S. , Sajithkumar C. , Mondkar Hemant S. , Barve Pravin A. , Diwan Sachin 
Published: July 2012

AbstractSymmetrical diesters containing triazole and oxadiazole units are subjected to Diekmann condensation to prepare title triazolophanes, e.g. (IV) and (VII), and oxadiazolophanes, e.g. (VI).
ChemInform Abstract: Efficient and Practical Transition Metal‐Free Catalytic Hydration of Organonitriles to Amides.
Authors: Tu Tao , Wang Zhixun , Liu Zelong , Feng Xike , Wang Qingyi 
Published: July 2012

AbstractPotassium carbonate is an efficient catalyst for the microwave‐assisted conversion of nitriles (I) into amides (II) (23 examples).
ChemInform Abstract: A New Synthetic Route for the Preparation of β‐Acyloxy Mercaptans via the Addition of Thioacids to Epoxides.
Authors: Abbasi Mohammad 
Published: July 2012

AbstractRing‐opening of epoxides with thioacids in the presence of silica gel‐NEt3 combined catalyst yields S‐benzylated β‐acyloxy mercaptans after benzylation of the crude thiols intermediates.
ChemInform Abstract: Suzuki Cross‐Coupling Catalyzed by Palladium (II) Complexes Bearing 1‐Aryl‐3,4,5,6‐tetrahydropyrimidine Ligands.
Authors: Mao Pu , Yang Liangru , Xiao Yongmei , Yuan Jinwei , Liu Xiujun , Song Maoping 
Published: July 2012

AbstractNovel monodentate imine complexes (I) are presented as highly efficient catalysts for the reaction.
ChemInform Abstract: Chiral Sulfoxide—Olefin Ligands: Tunable Stereoselectivity in Rh‐Catalyzed Asymmetric 1,4‐Additions.
Authors: Chen Guihua , Gui Jiangyang , Cao Peng , Liao Jian 
Published: July 2012

AbstractThe ligand E/Z geometry controls the absolute configuration of the product.
ChemInform Abstract: Synthesis of [60]Fullerene‐Fused Sultones via Sulfonic Acid Group Directed C—H Bond Activation.
Authors: Li Fei , Liu Tong‐Xin , Wang Guan‐Wu 
Published: July 2012

AbstractThe reaction involves cleavage of C—H and O—H bonds and formation of C—C and C—O bonds.
ChemInform Abstract: Synthesis and Chemistry of New Spiro‐Δ1‐pyrazoline.
Authors: Louhichi Nesrine , Houas Amel , Hamadi Naoufel Ben , Msaddek Moncef 
Published: July 2012

AbstractAddition of diazopropane (II) to α‐arylidenepyrrolidinones and α‐arylidene‐γ‐butyrolactones (I) affords the monoadducts (III) in a regiospecific fashion.
ChemInform Abstract: Facile Synthesis of 2‐Alkyl/Aryloxy‐2H‐azirines and Their Application in the Synthesis of Pyrroles.
Authors: Qi Xinxin , Xu Xianxiu , Park Cheol‐Min 
Published: July 2012

AbstractThe pyrrole synthesis can also be performed in an intramolecular manner by tethering of an alkene group onto the starting material, cf.
ChemInform Abstract: Cyclic α‐Amino Acids as Precursors for Synthesis of 2‐Amino‐3‐hetarylpyrrolin‐4‐ones and Their Spiro Derivatives.
Authors: Dobrydnev Alexey V. , Volovnenko Tatyana A. , Volovenko Yulian M. , Palamarchuk Gennady V. , Shishkin Oleg V. 
Published: July 2012

AbstractA facile route for the synthesis of hetarylpyrrolinones and corresponding spiro‐derivatives based on the reaction of N‐protected amino acids (I) with benzimidazolylacetonitriles (II) or thiazole analogues is developed.
ChemInform Abstract: Iodine‐Catalyzed Condensation of Isatin with Indoles: A Facile Synthesis of Di(indolyl)indolin‐2‐ones and Evaluation of Their Cytotoxicity.
Authors: Reddy B. V. Subba , Rajeswari N. , Sarangapani M. , Prashanthi Y. , Ganji Roopa Jones , Addlagatta Anthony 
Published: July 2012

AbstractThe title compounds (III) (15 examples) are smoothly obtained under mild reaction conditions and found to possess a strong and selective cytotoxicity against cancer cells.
ChemInform Abstract: Efficient Construction of Fused Indolines with a 2‐Quaternary Center via an Intramolecular Heck Reaction with a Low Catalyst Loading.
Authors: Zhao Lei , Li Ziyuan , Chang Lin , Xu Jinyi , Yao Hequan , Wu Xiaoming 
Published: July 2012

AbstractThe transformation is effective for 2,3‐disubstituted indoles.
ChemInform Abstract: Palladium‐ and Copper‐Catalyzed Cyclizations of Hydrazine‐Derived Ugi Products: Facile Synthesis of Substituted Indazolones and Hydroxytriazafluorendiones.
Authors: Welsch Sebastian , Kalinski Cedric , Umkehrer Michael , Ross Guenther , Kolb Juergen , Burdack Christoph , Wessjohann Ludger A. 
Published: July 2012

AbstractA broad spectrum of Ugi four‐component products involving ortho‐halogenated benzoic acids and protected hydrazines is synthesized.
ChemInform Abstract: Synergistic Chiral Ion Pair Catalysts for Asymmetric Catalytic Synthesis of Quaternary α,β‐Diamino Acids.
Authors: Shi Shi‐Hui , Huang Fu‐Ping , Zhu Ping , Dong Zhen‐Wen , Hui Xin‐Ping 
Published: July 2012

AbstractThe reaction proceeds with high dia‐ and enantioselectivities using a combination of a chiral phosphate anion and silver cation as a catalytic system.
ChemInform Abstract: Solvent‐Free One‐Pot Synthesis of Sulfonephthaleins from Saccharin and Phenols.
Authors: Tillu V. H. , Dumbre D. K. , Borate H. B. , Wakharkar R. D. , Choudhary V. R. 
Published: July 2012

AbstractThe reaction proceeds via in situ generation of o‐sulfobenzoic anhydride and its subsequent acid‐catalyzed condensation with phenols.
ChemInform Abstract: Synthesis and Characterization of 5‐Heteroarylsulfanyl‐4‐aryl‐1,2,3‐selena/thiadiazoles.
Authors: Manikannan Ramaiyan , Shanmugaraja Masilamani , Manojveer Seetharaman , Muthusubramanian Shanmugam 
Published: July 2012

AbstractThe reaction of heteroarylthio substituted semicarbazones (I) and (III) with thionyl chloride and selenium dioxide affords the corresponding thia‐ (II) and selenadiazoles (IV), respectively.
ChemInform Abstract: Studies on Novel Synthetic Methodologies. Part 9. A Novel Route to Synthesis of Flavones from Salicylaldehyde and Acetophenone Derivatives.
Authors: Sashidhara Koneni V. , Kumar Manoj , Kumar Abdhesh 
Published: July 2012

AbstractThe alternative process involves formation of 2‐hydroxychalcones followed by oxidative cyclization in the presence of catalytic iodine.
ChemInform Abstract: Enantioselective Activation of Stable Carboxylate Esters as Enolate Equivalents via N‐Heterocyclic Carbene Catalysts.
Authors: Hao Lin , Du Yu , Lv Hui , Chen Xingkuan , Jiang Huishen , Shao Yaling , Chi Yonggui Robin 
Published: July 2012

AbstractArylacetic ester enolates, generated in situ, react with α,β‐unsaturated imines to afford highly substituted N‐tosyl dihydropyridinones.