Articles de revues : « [Pt]-Oligomers »

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Melník, Milan, Peter Mikuš et Clive E. Holloway. « Platinum organometallic complexes : classification and analysis of crystallographic and structural data of tri- and oligomeric complexes ». Reviews in Inorganic Chemistry 34, n^o 4 (1 décembre 2014) : 247–79. http://dx.doi.org/10.1515/revic-2013-0015.

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AbstractThis review covers almost 100 organoplatinum complexes: trimers (40 examples), tetramers (40 examples), pentamers (4 examples), hexamers (5 examples), nona- and oligomers (8 examples). Platinum is predominantly found in the oxidation states +2 and +4. A number of coordination geometries are observed, the most common being essentially square planar, especially with Pt(II), and distorted octahedral, especially with Pt(IV). The most common ligands are methyl, carbonyl, PX3 and bis(diphenylphosphine)methane. Relationships between the Pt-Pt distances, Pt-X-Pt bridge angles, Pt-L bond distances and covalent radii of coordinated atoms are discussed. The mean Pt-Pt bond distance elongates in the order of nuclearity: 269.0 pm (trimers)<270.5 pm (tetramers)<271.5 pm (dimers)<278.0 pm (oligomers). A comprehensive brief discussion on over 1600 organoplatinum complexes and over 2500 platinum coordination complexes is given. These complexes prefer to crystallize in monoclinic (53%) and triclinic (27%) crystal classes. About l0% of these 4100 plus complexes exist as isomers. It is observed that these isomers are more often stereoisomers than structural isomers and that distortion isomerism is surprisingly more common than the better known cis-trans isomerism, especially in the chemistry of Pt(II) complexes.

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D’Ambroise, J., P. G. Kevrekidis et S. Lepri. « Asymmetric wave propagation through nonlinear PT-symmetric oligomers ». Journal of Physics A : Mathematical and Theoretical 45, n^o 44 (23 octobre 2012) : 444012. http://dx.doi.org/10.1088/1751-8113/45/44/444012.

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Irwin, Michael J., Guochen Jia, Jagadese J. Vittal et Richard J. Puddephatt. « Rigid-Rod Polymers, Oligomers, and Model Complexes with Pt−Pt Bonds in the Backbone ». Organometallics 15, n^o 25 (janvier 1996) : 5321–29. http://dx.doi.org/10.1021/om960420q.

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Rochon, Fernande D., Pi-Chang Kong et Louise Girard. « Reactions of cis-[Pt(sulfoxide)2Cl2] with silver salts and synthesis of hydroxo-bridged platinum(II) complexes with sulfoxides ». Canadian Journal of Chemistry 64, n^o 9 (1 septembre 1986) : 1897–902. http://dx.doi.org/10.1139/v86-313.

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Platinum(II) compounds of the type cis-[Pt(L)2X2] where L = tetramethylenesulfoxide (TMSO), ethylmethylsulfoxide (EMSO), di-n-propylsulfoxide (DPSO), benzylmethylsulfoxide (BMSO), and dibenzylsulfoxide (DBSO) and X = Cl− and I− have been synthesized. The reactions of these compounds with a silver salt were studied in aqueous solution. Monomers of the type cis-[Pt(L)2(ClO4)2] (L = TMSO, EMSO, and DBSO), cis-[Pt(EMSO)2(SO4)] and hydroxy-bridged oligomers were isolated. Dimers, cis-[Pt(L)2(OH)]2(NO3)2 (L = TMSO, DPSO), and cis-[Pt(EMSO)2(OH)]2SO4 and possibly a trimer (cis-[Pt(EMSO)2(OH)]3)2(SO4)3 were characterized. The compounds were studied by infrared spectroscopy and by 1H nmr.

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Silverman, Eric E., Thomas Cardolaccia, Xiaoming Zhao, Kye-Young Kim, Ksenija Haskins-Glusac et Kirk S. Schanze. « The triplet state in Pt-acetylide oligomers, polymers and copolymers ». Coordination Chemistry Reviews 249, n^o 13-14 (juillet 2005) : 1491–500. http://dx.doi.org/10.1016/j.ccr.2004.11.020.

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Bonuccelli, Veronica, Tiziana Funaioli, Piero Leoni, Fabio Marchetti, Lorella Marchetti et Marco Pasquali. « Synthesis and characterization of non-bridging mono- and bis-σ-η1-alkynyl derivatives of the phosphido-bridged hexaplatinum core [Pt6(μ-PBut2)4(CO)4]2+ ». Dalton Transactions 45, n^o 16 (2016) : 6878–92. http://dx.doi.org/10.1039/c6dt00410e.

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Several mono- or bis-alkynyl derivatives of the [Pt₆(μ-PBu^t₂)₄(CO)₄]²⁺ core, pivotal intermediates in the synthesis of new cluster-containing oligomers, were prepared and fully characterized.

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Hadi, Sutopo, et Trevor G. Appleton. « STUDY OF REACTION OF TRANS-[Pt(¹⁵NH₃)₂(H₂O)₂]²⁺ WITH N-ACETYL-L-CYSTEINE ». Indonesian Journal of Chemistry 5, n^o 1 (14 juin 2010) : 54–57. http://dx.doi.org/10.22146/ijc.21839.

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A study of the reaction between trans-[Pt(15NH3)2(H2O)2](NO3)2 and N-acetyl-L-cysteine (H3accys) was undertaken to confirm the identity of the products formed. In alkaline solution, the platinum products observed were mononuclear species, while in acidic solution, the oligomeric products were obtained. The mass spectrometry of the reaction in alkaline solution showed a sulfur-bridged dinuclear platinum(II) species, trans-[{Pt(H2accys-S)2(15NH3)2}2((-H2accys-S)]+ giving m/z 948 and the lost of two ammines was observed. Keywords: thiolate, oligomers, 2D NMR, mass spectrometry

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Wang, Man, Yahui Zhang, Zuqi Fei, Dongchao Xie, Haihua Zhang, Qizhen Du et Peng Jin. « Hyaluronan Oligosaccharides-Coated Paclitaxel-Casein Nanoparticles with Enhanced Stability and Antitumor Activity ». Nutrients 14, n^o 19 (20 septembre 2022) : 3888. http://dx.doi.org/10.3390/nu14193888.

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This study aims to develop specific-molecular-weight hyaluronic acid oligosaccharides-coated paclitaxel-loaded casein nanoparticles (HA-PT-Cas NPs) via chemical conjugation to increase the stability and antitumor effects. Optimized HA-PT-Cas NPs (HA/casein of 3:1) were obtained with a mean size of 235.3 nm and entrapment efficiency of 93.1%. HA-PT-Cas exhibited satisfactory stability at 4 °C for 12 days and 37 °C for 3 h; paclitaxel was retained at rates of 81.4% and 64.7%, respectively, significantly higher than those of PT-Cas (only 27.8% at 4 °C after 16 h and 20.3% at 37 °C after 3 h). HA-PT-Cas exhibited high efficiency (61.3%) in inhibiting A375 tumor owing to the enhanced stability of HA oligosaccharides barrier, which was comparable with that of 10 μg/mL cis-platinum (64.9%). Mice experiments showed the 74.6% tumor inhibition of HA-PT-Cas by intravenously administration, significantly higher than that of PT-casein (39.8%). Therefore, this work provides an effective carrier for drug delivery via HA oligomers-coated modification.

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Kirikchi, O. B., et N. Karjanto. « Discrete solitons dynamics in $$\mathscr {PT}$$-symmetric oligomers with complex-valued couplings ». Nonlinear Dynamics 103, n^o 3 (février 2021) : 2769–82. http://dx.doi.org/10.1007/s11071-021-06217-5.

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Sebhat, Woldemichael, Ayman El Roz, Pascal Fongarland, Léa Vilcocq et Laurent Djakovitch. « Catalytic Liquefaction of Kraft Lignin with Solvothermal Approach ». Catalysts 11, n^o 8 (21 juillet 2021) : 875. http://dx.doi.org/10.3390/catal11080875.

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Lignin is a natural biopolymer present in lignocellulosic biomass. During paper pulp production with the Kraft process, it is solubilized and degraded in Kraft lignin and then burned to recover energy. In this paper, the solvolysis of Kraft lignin was studied in water and in water/alcohol mixtures to produce oligomers and monomers of interest, at mild temperatures (200–275 °C) under inert atmosphere. It was found that the presence of alcohol and the type of alcohol (methanol, ethanol, isopropanol) greatly influenced the amount of oligomers and monomers formed from lignin, reaching a maximum of 48 mg·glignin−1 of monomers with isopropanol as a co-solvent. The impact of the addition of various solid catalysts composed of a metal phase (Pd, Pt or Ru) supported on an oxide (Al2O3, TiO2, ZrO2) was investigated. In water, the yield in monomers was enhanced by the presence of a catalyst and particularly by Pd/ZrO2. However, with an alcoholic co-solvent, the catalyst only enhanced the formation of oligomers. Detailed characterizations of the products with FTIR, 31P-NMR, 1H-NMR and HSQC NMR were performed to elucidate the chemical transformations occurring during solvolysis. The nature of the active catalytic specie was also investigated by testing homogeneous palladium catalysts.

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Ruiz del Árbol, Nerea, Carlos Sánchez‐Sánchez, Gonzalo Otero‐Irurueta, José I. Martínez, Pedro L. Andrés, Ana C. Gómez‐Herrero, Pablo Merino et al. « On‐Surface Driven Formal Michael Addition Produces m ‐Polyaniline Oligomers on Pt(111) ». Angewandte Chemie 132, n^o 51 (12 octobre 2020) : 23420–27. http://dx.doi.org/10.1002/ange.202009863.

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Ruiz del Árbol, Nerea, Carlos Sánchez‐Sánchez, Gonzalo Otero‐Irurueta, José I. Martínez, Pedro L. Andrés, Ana C. Gómez‐Herrero, Pablo Merino et al. « On‐Surface Driven Formal Michael Addition Produces m ‐Polyaniline Oligomers on Pt(111) ». Angewandte Chemie International Edition 59, n^o 51 (12 octobre 2020) : 23220–27. http://dx.doi.org/10.1002/anie.202009863.

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Rochon, F. D., et Louise Girard. « Étude par résonance magnétique nucléaire du platine-195 de la réaction de cis-[Pt(éthylméthylsulfoxyde)2Cl2] avec un sel d'argent ». Canadian Journal of Chemistry 64, n^o 10 (1 octobre 1986) : 1974–78. http://dx.doi.org/10.1139/v86-327.

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The products of the reaction of cis-[Pt(EMSO)2Cl2] (EMSO = ethylmethylsulfoxide) with Ag2SO4 were studied by 195Pt nuclear magnetic resonance. The results have shown the presence of several species in aqueous solution. The reactions were done at different conditions of pH. The spectra of two isolated oligomers were also measured. The hydroxy-bridged dimer and trimer show a signal around −2900 ppm while the hydrolyzed monomers have signals around −3200 ppm. A semi-quantitative profile of the different equilibria in solution is suggested.

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NANDY, SUBHAJIT, PINAKI CHAUDHURY, RAHUL SHARMA et S. P. BHATTACHARYYA. « A DENSITY-MATRIX-BASED SIMULATED ANNEALING (SA) TECHNIQUE FOR LOCATING MINIMUM ENERGY STRUCTURES ON THE NEUTRAL POLYTHIOPHENE POTENTIAL ENERGY SURFACE ». Journal of Theoretical and Computational Chemistry 07, n^o 05 (octobre 2008) : 977–87. http://dx.doi.org/10.1142/s0219633608004234.

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We use the elements of the single particle density matrix in the atomic orbital basis as the basic variables and the simulated annealing method as the optimization tool to locate the global minima on the potential surfaces of polythiophene and polyselenophene oligomers (PT)n, (PS)n with n up to 100. A modified version of the Su–Schrieffer–Heeger Hamiltonian is used to generate the PES and the unitary transformation of the density variables as the bond lengths change during random reconfiguring moves. The cost effectiveness of the method is analyzed.

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Jiang, Feng-Lei, Daniel Fortin et Pierre D. Harvey. « Syntheses, Characterization, and Photophysical Properties of Conjugated Organometallic Pt-Acetylide/Zn(II) Porphyrin-Containing Oligomers ». Inorganic Chemistry 49, n^o 6 (15 mars 2010) : 2614–23. http://dx.doi.org/10.1021/ic901421m.

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Ji, Zhi Hong, Yan Bin Jiang, Hao Li, Li Ye, Wei Jian Han et Tong Zhao. « Synthesis and Characterization of Platinum-Containing Ordered Mesoporous Carbon with High Specific Surface Area ». Advanced Materials Research 79-82 (août 2009) : 2035–38. http://dx.doi.org/10.4028/www.scientific.net/amr.79-82.2035.

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A Pt-containing ordered mesoporous carbon with a high specific surface area was synthesized through evaporation-induced multi-constituent co-assembly method, wherein soluble resol polymer is used as the carbon precursor, silicate oligomers as the inorganic precursor, triblock copolymer as the template, and H2PtCl6•6H2O as the Pt precursor. After thermopolymerization, the template was removed by calcinations, and silica was removed by NaOH solutions. The resultant sample was characterized by X-ray diffraction, nitrogen sorption and transmission electron microscopy. The results showed that the carbon material exhibited highly ordered mesoporous structure, with a high specific surface area of 1560 m2/g, and the pore size distributions of the sample are very narrow, centering at around 6 nm; and the platinum particles with sizes of less than 8 nm were highly distributed in the carbon matrix. The high specific surface area may be ascribed to plenty of small pores inside carbon walls caused by the removal of silica from the composites. Interaction between the Pt4+ and the resin caused the Pt species to be incorporated into the framework of the resin, which was self-assembled into an ordering structure under the direction of the surfactant. After being subjected to pyrolysis at a high temperature, the Pt4+ ions were gradually reduced to form Pt nanoparticles, which were strongly imbedded in the carbon substrate and thereby thermally stable. The removal of silica may result in the exposure of Pt nanoparticles, which render Pt nanoparticles to contact easily with reactant molecules.

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Ghosh, Pijush K. « Classical Hamiltonian Systems with balanced loss and gain ». Journal of Physics : Conference Series 2038, n^o 1 (1 octobre 2021) : 012012. http://dx.doi.org/10.1088/1742-6596/2038/1/012012.

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Abstract Classical Hamiltonian systems with balanced loss and gain are considered in this review. A generic Hamiltonian formulation for systems with space-dependent balanced loss and gain is discussed. It is shown that the loss-gain terms may be removed completely through appropriate co-ordinate transformations with its effect manifested in modifying the strength of the velocity-mediated coupling. The effect of the Lorentz interaction in improving the stability of classical solutions as well as allowing a possibility of defining the corresponding quantum problem consistently on the real line, instead of within Stokes wedges, is also discussed. Several exactly solvable models based on translational and rotational symmetry are discussed which include coupled cubic oscillators, Landau Hamiltonian etc. The role of PT -symmetry on the existence of periodic solution in systems with balanced loss and gain is critically analyzed. A few non- PT -symmetric Hamiltonian as well as non-Hamiltonian systems with balanced loss and gain, which include mechanical as well as extended system, are shown to admit periodic solutions. An example of Hamiltonian chaos within the framework of a non- PT -symmetric system of coupled Duffing oscillator with balanced loss-gain and/or positional non-conservative forces is discussed. It is conjectured that a non- PT -symmetric system with balanced loss-gain and without any velocity mediated interaction may admit periodic solution if the linear part of the equations of motion is necessarily PT symmetric —the nonlinear interaction may or may not be PT -symmetric. Further, systems with velocity mediated interaction need not be PT -symmetric at all in order to admit periodic solutions. Results related to nonlinear Schrödinger and Dirac equations with balanced loss and gain are mentioned briefly. A class of solvable models of oligomers with balanced loss and gain is presented for the first time along with the previously known results.

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Langlois, Guillaume, Shawkat M. Aly, Claude P. Gros, Jean-Michel Barbe et Pierre D. Harvey. « Rational synthetic design of well-defined Pt(bisethynyl)/Zn(porphyrin) oligomers for potential applications in photonics ». New Journal of Chemistry 35, n^o 6 (2011) : 1302. http://dx.doi.org/10.1039/c0nj00819b.

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Estrany, Francesc, Ramon Oliver, Esther García, Esther Gualba, Pere-Lluís Cabot et Enric Brillas. « Electrogeneration of Conducting Poly(α-tetrathiophene). Effect of Solution Stirring and Detection of Linear Oligomers ». Collection of Czechoslovak Chemical Communications 68, n^o 7 (2003) : 1326–44. http://dx.doi.org/10.1135/cccc20031326.

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The anodic oxidation of α-tetrathiophene on Pt was studied in a 1.0 mM monomer solution in 0.1 M LiClO4 in 45:35:20 acetonitrile/ethanol/DMF. Three consecutive oxidation peaks were detected by cyclic voltammetry, along with a cathodic peak related to the reduction of electroactive polarons formed during the first anodic process. Uniform, adherent, insoluble and black polymer films were obtained by chronoamperometry at 1.000 V vs Ag|AgCl corresponding to the first oxidation-polymerization process. Stirring of monomer solution promotes the production of polymer, favoring the oxidation of polymer chains with the incorporation of more doping ClO4- ions and ion pairs of Li+ClO4- in their monomeric units. The conductivity of the polymer obtained under stirring was three orders of magnitude higher than that synthesized from a quiescent solution. The scanning electron microscopy images also showed much more uniform films under stirring. This behavior points to the existence of less crosslinking in the polymer and the production of longer linear chains when the solution is stirred. IR analysis of these materials confirmed the formation of crosslinked chains with predominance of β-β linkages. Short linear oligomers such as the dimer, trimer and tetramer were detected in all polymers by MALDI-TOF-MS, thus showing a radical polycondensation as initial electropolymerization mechanism. A larger proportion of linear oligomers is formed under solution stirring.

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Harvey, Pierre D. « Organometallic and Coordination Polymers, and Linear and Star Oligomers Using the trans-Pt(PR3)2(C≡C)2 Linker ». Journal of Inorganic and Organometallic Polymers and Materials 27, S1 (15 septembre 2017) : 3–38. http://dx.doi.org/10.1007/s10904-017-0673-y.

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Clément, Sébastien, Shawkat M. Aly, Jérôme Husson, Daniel Fortin, Carsten Strohmann, Michael Knorr, Laurent Guyard, Alaa S. Abd-El-Aziz et Pierre D. Harvey. « A-Frame-Containing Organometallic Oligomers Constructed From Homo- and Heterobimetallic M(μ-dppm)2M′ (M/M′ = Pd, Pt) Building Blocks ». European Journal of Inorganic Chemistry 2009, n^o 17 (juin 2009) : 2536–46. http://dx.doi.org/10.1002/ejic.200900103.

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Zeng, Peng, Ying-Hong Xu et Ming-Fei Li. « Catalytic reductive depolymerization of corncob lignin to produce bio-oil via formic acid/ethanol system ». BioResources 18, n^o 1 (30 janvier 2023) : 2083–99. http://dx.doi.org/10.15376/biores.18.1.2083-2099.

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Formic acid (FA) was used for reductive depolymerization of industrial corncob lignin via ethanol and Pt/C system. The highest yield of bio-oil obtained was 71.4% when the reaction was conducted at 260 °C with an FA/lignin ratio of 8 for 0.5 h. The bio-oil was composed of oligomers (Mw within 600 Da) and lignin depolymerized fragments (Mw beyond 600 Da). Reaction temperature was the most important factor affecting the properties of bio-oil. Although excessive temperature could increase the C/H ratio and higher heating value (HHV) of bio-oil, it would lead to repolymerization of lignin degraded fragments, thus resulting in a higher molecular weight of bio-oil. Additionally, alkylphenols were major products in bio-oil, and the amount of alkyl phenols could be increased by increasing the temperature and extending the retention time appropriately. This study reveals the effects of various reaction conditions on the yield and properties of bio-oil, providing a theoretical basis for subsequent upgrading of bio-oil to biofuels and aromatic chemicals.

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Fratoddi, I., C. Battocchio, A. Furlani, P. Mataloni, G. Polzonetti et M. V. Russo. « Study of chemical structure and conjugation length in organometallic Pt(II) oligomers and polymers containing 1,4-diethynylbenzene derivatives as bridging units ». Journal of Organometallic Chemistry 674, n^o 1-2 (mai 2003) : 10–23. http://dx.doi.org/10.1016/s0022-328x(03)00156-6.

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Meletov, K. P., G. Velkos, J. Arvanitidis, D. Christofilos et G. A. Kourouklis. « Raman study of the photopolymer formation in the {Pt(dbdtc) 2 }·C 60 fullerene complex and the decomposition kinetics of the photo-oligomers ». Chemical Physics Letters 681 (août 2017) : 124–29. http://dx.doi.org/10.1016/j.cplett.2017.05.065.

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Amodeo, Giuseppe Federico, Natalya Krilyuk et Evgeny V. Pavlov. « Formation of High-Conductive C Subunit Channels upon Interaction with Cyclophilin D ». International Journal of Molecular Sciences 22, n^o 20 (13 octobre 2021) : 11022. http://dx.doi.org/10.3390/ijms222011022.

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The c subunit of the ATP synthase is an inner mitochondrial membrane (IMM) protein. Besides its role as the main component of the rotor of the ATP synthase, c subunit from mammalian mitochondria exhibits ion channel activity. In particular, c subunit may be involved in one of the pathways leading to the formation of the permeability transition pore (PTP) during mitochondrial permeability transition (PT), a phenomenon consisting of the permeabilization of the IMM due to high levels of calcium. Our previous study on the synthetic c subunit showed that high concentrations of calcium induce misfolding into cross-β oligomers that form low-conductance channels in model lipid bilayers of about 400 pS. Here, we studied the effect of cyclophilin D (CypD), a mitochondrial chaperone and major regulator of PTP, on the electrophysiological activity of the c subunit to evaluate its role in the functional properties of c subunit. Our study shows that in presence of CypD, c subunit exhibits a larger conductance, up to 4 nS, that could be related to its potential role in mitochondrial toxicity. Further, our results suggest that CypD is necessary for the formation of c subunit induced PTP but may not be an integral part of the pore.

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Brillas, Enric, José Carrasco, Ramon Oliver, Francesc Estrany et Víctor Ruiz. « Effects of Doping on the Electrochemical and Electrical Properties of Poly(2,5-di(2-thienyl)pyrrole) ». Collection of Czechoslovak Chemical Communications 64, n^o 8 (1999) : 1357–68. http://dx.doi.org/10.1135/cccc19991357.

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The electropolymerization of 2,5-di(2-(thienyl)pyrrole) (SNS) on a Pt electrode from ethanolic solution with LiClO4 or LiCl as electrolyte has been studied by cyclic voltammetry (CV) and chronoamperometry (CA). In both media, a quasi-reversible process has been indicated by CV, reversing the scan at low oxidation potentials. Under these conditions, reducible positive charges formed in both oxidized polymers are compensated by the entrance of anions from solution. Elemental analysis reveals that polymers generated at a low oxidation potential by CA contain a 21.03% (w/w) of ClO4- or a 9.56% (w/w) of Cl-. The poly(SNS) doped with Cl- presents higher proportion of reducible positive charges, higher polymerization charge and lower productivity. A much higher electrical conductivity, however, has been found for the poly(SNS) doped with ClO4-. Both polymers are soluble in DMSO, acetone and methanol. The dimer, trimer, tetramer and pentamer have been detected as soluble and neutral linear oligomers by mass spectrometry-fast atom bombardment. The analysis of polymers by infrared spectroscopy confirms the predominant formation of linear molecules with α-α linkages between monomeric units. A condensation mechanism involving one-electron oxidation of all electrogenerated linear and neutral polymeric chains is proposed to explain the SNS electropolymerization.

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Zhuravkov, Sergey P., Elena L. Boytsova et Anastasia V. Slavinskaya. « STABILIZATION OF POLYETHYLENE AND OTHER POLYOLEFINS BY PHENOTHIAZINE DERIVATIVES ». ChemChemTech 67, n^o 12 (12 novembre 2024) : 96–101. https://doi.org/10.6060/ivkkt.20246712.6941.

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This paper presents the results of the synthesis and study of the thermostabilizing properties of a number of new derivatives, as well as previously known derivatives of Phenothiazine (PT). The objects of the study were: cis-10-propenylphenothiazine (cis-10-PPT), 1-ethyl-2-methyl-3-(10H-phenothiazin-10-yl)-2,3-dihydro-1H-pyrido[3,2,1-kl]phenothiazine. Propenylphenothiazine dimer (DPРT),1-ethyl-2-methyl-3-(5-oxido-10H-phenothiazin-10-yl)-2,3-dihydro-1H-pyrido[3,2,1-kl]phenothiazine 7-oxide. S-oxide (DPРTО),1-ethyl-2-methyl-1H-pyrido-[3,2,1-k,l]phenothiazine. Pyridophenothiazine (PyrPT) and a mixture of two fractions of 10-propenylphenothiazine oligomers: 1-ethyl-2-methyl-3-(10H-phenothiazin-3-yl)-2,3-dihydro-1H-pyrido[3,2,1-kl]phenothiazine (ОPРT 1) and 3,7-bis(1-ethyl-2-methyl-2,3-dihydro-1H-pyrido[3,2,1-kl]phenothiazin-3-yl)-10H-phenothiazine (ОPРT 2). A well-known industrial stabilizer, Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox 1010), was used as a comparison sample. Irganox 1010 is an antioxidant based on spatially hindered phenol with a high molecular weight, has very low volatility, is used as an antioxidant and heat stabilizer for polypropylene, polyethylene, impact-resistant polystyrene, poly-4-methyl-pentene. To evaluate the stabilizing effect of PT derivatives, a powder of unstabilized templene (a copolymer of poly-4-methylpentene-1 and n-hexene) was used. Thermogravimetric (TGA) and differential thermal analysis (DTA) methods were used to study the thermal oxidative degradation of polymer compositions based on templene in open and closed crucibles. For each tested stabilizer sample, the following were determined: the temperature of the beginning of decomposition of the polymer composition (Tb.d., °C), the decomposition temperature of 1% of the mass of the tested polymer composition (T1%, °C). Based on the experimental data obtained, the following were calculated: the thermal stability of the tested compositions, the effective activation energy (Ea). The thermostabilizing effect of additives in compositions based on ethylene copolymer with vinyl acetate (savylene), high-pressure polyethylene (HDPE) was evaluated according to TU 301-05-91, according to the accumulation time of acidic polymer degradation products in them during aging at 180 °C and 160 °C in oxygen current (pH), as well as by the change in the melt flow index in the process of holding the polymer in air at 200 °C for two hours (for savylene and HDPE). In addition, the effectiveness of the additives was evaluated by changing the mechanical properties of the compositions: tensile yield strength (σt), elongation (ε, %). It was found that mixture of two fractions oligomers (OPPT 1) and (OPPT 2) products synthesized from cis-10-PPT have a sufficiently high stabilizing effect. For citation: Zhuravkov S.P., Boytsova E.L., Slavinskaya A.V. Stabilization of polyethylene and other polyolefins by phenothiazine derivatives. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 12. P. 96-101. DOI: 10.6060/ivkkt.20246712.6941.

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Niazi, Maryam, et Axel Klein. « DFT Investigation of the Molecular Properties of the Dimethylglyoximato Complexes [M(Hdmg)2] (M = Ni, Pd, Pt) ». Inorganics 9, n^o 6 (7 juin 2021) : 47. http://dx.doi.org/10.3390/inorganics9060047.

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Important applications of the NiII, PdII and PtII complexes [M(Hdmg)2] (H2dmg = dimethylglyoxime) stem from their metal...metal stacked virtually insoluble aggregates. Given the virtual insolubility of the materials, we postulated that the rare reports on dissolved species in solution do not represent monomolecular species but oligomers. We thus studied the structural and spectral properties of the monomolecular entities of these compounds using density functional theory (DFT) and time-dependent DFT computations in dimethyl sulfoxide (DMSO) as a solvent. The molecular geometries, IR and UV-vis spectra, and frontier orbitals properties were computed using LANL2DZ ecp and def2TZVP as basis sets and M06-2X as the functional. The results are compared with the available experimental and other calculated data. The optimised molecular geometries proved the asymmetric character of the two formed O–H…O bonds which connect the two Hdmg‒ ligands in the completely planar molecules. Calculated UV-vis spectra revealed the presence of three absorptions in the range 180 to 350 nm that are red-shifted along the series Ni–Pd–Pt. They were assigned to essentially ligand-centred π−π* transitions in part with metal(d) to ligand(π*) charge transfer (MLCT) contributions. The notorious d‒p transitions dominating the colour and electronics of the compounds in the solid-state and oligomeric stacks are negligible in our monomolecular models strongly supporting the idea that the previously reported spectroscopic observations or biological effects in solutions are not due to monomolecular complexes but rather to oligomeric dissolved species.

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Fratoddi, Ilaria, Chiara Battocchio, Alessandra L. Groia et Maria V. Russo. « Nanostructured polymetallaynes of controlled length : Synthesis and characterization of oligomers and polymers from 1,1′-bis-(ethynyl)4,4′-biphenyl bridging Pt(II) or Pd(II) centers ». Journal of Polymer Science Part A : Polymer Chemistry 45, n^o 15 (2007) : 3311–29. http://dx.doi.org/10.1002/pola.22081.

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Lin, Yuan, Maio Wang et Xu Rui Xiao. « Investigation of PEO-Imidazole Ionic Liquid Oligomer and Polymer Electrolytes for Dye-Sensitized Solar Cells ». Key Engineering Materials 451 (novembre 2010) : 41–61. http://dx.doi.org/10.4028/www.scientific.net/kem.451.41.

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Ionic liquid oligomer, 1-oligo(ethyleneoxide)-3-methylimidazolium salt (PEO(X)MIm) and Ionic liquid polymer, poly(1-oligo (ethylene glycol) methacrylate-3-methylimidazolium) salt (P(MOEMIm)) prepared by incorporating imidazolium ionic liquid with PEO oligomer and polymer were investigated as electrolytes for dye-sensitized solar cells (DSCs). Ionic liquid electrolytes were composed of LiI, I2, and PEO(X)MImCl or the mixture of 1-hexyl-3-methylidazolium iodide (HMImI), 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) and PEO(X)MImCl. Quasi-solid-state electrolytes were prepared by employing the imidazole polymers P(MOEMImCl) to solidify the liquid electrolyte containing lithium iodide, iodine and ethylene carbonate (EC)/propylene carbonate (PC) mixed solvent. Ionic liquid based quasi-solid state electrolytes were prepared by solidifying the ionic liquid electrolytes containing HMImI or a binary mixture of HMImI and EMImBF4 with an ionic liquid polymer P(MOEMImCl), respectively. The influences of PEO molecular weight, polymer content, addition of alkyl ionic liquid and various anions of the ionic liquid oligomers and polymer on the ionic conductivity, apparent diffusion coefficient of the redox species in the electrolytes and the performance of solar cells were examined. The influences on the kinetic behaviors of dye regeneration and triiodide reduction reactions taken place at nanocrystalline TiO2 electrode and Pt counter-electrode, respectively, were also studied by cyclic-voltammetry and electrochemical impedance spectroscopy measurements. By using ternary ionic liquid electrolyte containing 1M lithium iodide and 0.5M iodine in the ionic liquid of the ionic liquid mixture of PEO(X)MImCl), HMImI and EMImBF4, quasi-solid-state electrolytes and ionic liquid based quasi-solid state electrolytes the photoelectron conversion efficiency of DSCs is 7.89%, 7.6% and 6.1%, respectively(AM 1.5, 100mWcm−2). These results show the potential application of PEO based ionic liquid in SCs.

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Zonder, Jeffrey, Christiane Houde, Sascha Tuchman, Vishal Kukreti, Vaishali Sanchorawala, Silva Pregja, Kathy A. Reichel, Steven M. Burt, Colleen Neveux et Jeffrey Matous. « A Phase I Trial of Pomalidomide, Bortezomib (Velcade), and Dexamethasone (PVD) As Initial Treatment of AL Amyloidosis and Light Chain Deposition Disease ». Blood 124, n^o 21 (6 décembre 2014) : 4767. http://dx.doi.org/10.1182/blood.v124.21.4767.4767.

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Abstract Introduction: AL amyloidosis (AL) and Light Chain Deposition Disease (LCDD) are plasma cell dyscrasias in which misfolded monoclonal light chains form insoluble extracellular protein deposits (fibrillar and amorphous, respectively). In AL particularly, toxic soluble light chain oligomers also play a role in disease pathogenesis. Treatment of AL and LCDD aims at eliminating the abnormal plasma cell clone. Typical agents used include corticosteroids, bortezomib (btz), alkylators, or immunomodulatory drugs (IMiDs) such as lenalidomide (len) or pomalidomide (pom). Len-btz-dexamethasone (dex) is a highly efficacious frontline regimen commonly used for multiple myeloma, a related plasma cell cancer. Despite this, prospective studies using btz-IMiD combos as initial therapy of AL or LCDD are lacking. Here we report our experience with pom-btz-dex(PVD) for pts with AL or LCDD. Methods: This is a prospective Phase I trial using a standard 3+3 dose escalation scheme (described in Table 1). The primary objective is to establish the maximally tolerated dosing (MTD), with assessment for dose limiting toxicity (DLT) extending through cycles 1 and 2 for each pt. Hematologic and organ responses (HR and OR) were assessed using recently updated guidelines. PVD was administered in repeating 28-day cycles until either DLT or progressive disease. Key inclusion/exclusion criteria: biopsy proven AL amyloidosis or LCDD; no more than 1 prior cycle of anti-plasma cell therapy; measurable disease defined as at least a 5 mg/dL difference between the involved (iFLC) and uninvolved (uFLC) serum free light chains, or a serum M-protein of 0.5 g/dL or greater (latter not permissible without measurable sFLCdifference after protocol amendment); ECOG PS of 2 or less; adequate renal, hepatic, and marrow function; no Grade 3 or higher peripheral neuropathy (PN; pts with painful grade 2 PN also excluded). Abnormal left ventricular ejection fraction or cardiac biomarkers allowed, but pts with NYHA class III/IV congestive heart failure or uncontrolled ventricular arrhythmias were excluded. Antithrombotic/antiviral prophylaxis was required for all pts. Results: Six pts have been enrolled thus far (3 each in cohorts 1 and 2, respectively). Three additional pts have already been identified for cohort 3. Five of 6 pts had AL, and 1 had LCDD. Median age was 65.5 yrs (range 49-74 yrs). 5 pts were female. Mayo cardiac stage I/II/III in 1, 2, and 3 pts, respectively. Three pts had one prior cycle of therapy (the others had none). The iFLC was lambda type in all 5 AL pts, and kappa for the pt with LCDD. Median number of organs involved by AL/LCDD was 2 (range, 2-4; 4 with both cardiac and renal, and 1 additional pt with cardiac). The median number of PVD cycles administered was 3 (range 1-6). Two pts are still on therapy. The reasons for stopping PVD in the other 4 pts were: sudden death due to underlying cardiac AL (during cycle 3 of PVD), pt preference after reaching maximal HR (after cycle 6), lack of HR (after cycle 3), and toxicity (after cycle 4). Baseline dex dose adjustment was required for protocol-specified reasons in all pts. One pt required further dex reduction during cycle 4 of PVD. No pts required baseline or subsequent modification of pom or btz. Table 2 summarizes reported adverse events (AEs). No DLTshave been observed. Two pts achieved HR (0 CR, 1 VGPR, 1 PR, 3 SD, 0 PD). Organ responses have not been observed, but the first protocol-specified OR assessment takes place after 4 cycles of PVD and some pts have yet to reach this time point. Conclusions: PVD was well tolerated in this group of pts with AL and LCDD. Importantly, no significant myelosuppression or PN was noted in the first 2 (out of a planned 4) dose cohorts. Most AEs have been related to the ptsÕ underlying AL/LCDD, though dex has posed difficulties for some pts. Hematologic responses have been seen, but organ responses are predictably lagging. Once the MTD is established, an 18-pt expansion cohort dosed at that level willfurther examine the efficacy of PVD as up-front treatment for AL and LCDD. Disclosures Zonder: Celgene: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy. Off Label Use: Pomalidomide and Bortezomib are approved drugs for multiple myeloma; they are used in this trial as treatment for the related plasma cell dyscrasias AL amyloidosis and light chain deposition disease. . Tuchman:Celgene: Honoraria, Research Funding, Speakers Bureau; Millennium: Honoraria, Research Funding, Speakers Bureau. Kukreti:Celgene: Honoraria. Burt:Celgene: Speakers Bureau. Matous:Takeda Pharmaceuticals International Co.: Speakers Bureau; Onyx: Speakers Bureau; Celgene: Consultancy, Speakers Bureau; Seattle Genetics, Inc.: Research Funding, Speakers Bureau.

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Li, K., et P. G. Kevrekidis. « PT-symmetric oligomers : Analytical solutions, linear stability, and nonlinear dynamics ». Physical Review E 83, n^o 6 (30 juin 2011). http://dx.doi.org/10.1103/physreve.83.066608.

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Zhang, M., E. G. Bromfield, J. B. Helms et B. M. Gadella. « The fate of porcine sperm CRISP2 from the perinuclear theca before and after in vitro fertilization ». Biology of Reproduction, 2 septembre 2022. http://dx.doi.org/10.1093/biolre/ioac169.

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Abstract In a previous study we reported that porcine sperm cysteine rich secretory protein 2 (CRISP2) is localized in the post-acrosomal sheath (PAS)-perinuclear theca (PT) as reduction-sensitive oligomers. In the current study, the decondensation and removal of CRISP2 was investigated during in vitro sperm capacitation, both after induction of the acrosome reaction and after in vitro fertilization. Confocal immunofluorescent imaging revealed that additional CRISP2 fluorescence appeared on the apical ridge and on the equatorial segment (EqS) of the sperm head following capacitation, likely due to cholesterol removal. After an ionophore A23187 induced acrosome reaction, CRISP2 immunofluorescence disappeared from the apical ridge and the EqS area partly due to the removal of the acrosomal shroud vesicles but also partly due to its presence in a subdomain of EqS (EqSS). The fate of sperm head CRISP2 was further examined post-fertilization. In vitro matured porcine oocytes were co-incubated with boar sperm cells for 6-8 h and the zygotes were processed for CRISP2 immunofluorescent staining. Notably, decondensation of CRISP2, and thus of the sperm PT, occurred while the sperm nucleus was still fully condensed. CRISP2 was no longer detectable in fertilized oocytes in which sperm nuclear decondensation and paternal pronucleus formation were apparent. This rapid dispersal of CRISP2 in the PT is likely regulated by redox reactions for which its cysteine rich domain is sensitive. Reduction of disulfide bridges within CRISP2 oligomers may be instrumental for PT dispersal and PT elimination.

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Yang, Yixing, Richard Farley, Timothy Steckler, Jonathan Sommer, Sang Hyun Eom, Kenneth Graham, John Reynolds, Kirk Schanze et Jiangeng Xue. « Near Infrared Fluorescent and Phosphorescent Organic Light-Emitting Devices ». MRS Proceedings 1154 (2009). http://dx.doi.org/10.1557/proc-1154-b05-98.

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AbstractOrganic light-emitting devices (OLEDs) emitting near-infrared (NIR) light have many potential applications, yet the efficiency of these devices remains very low, typically ˜0.1% or less. Here we report efficiency NIR OLEDs based on two fluorescent donor-acceptor-donor oligomers and a phosphorescent Pt-containing organometallic complex. External quantum efficiencies in the range of 0.5–3.8% with emission peak ranging from 700 to 890 nm have been achieved.

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Cooper, Thomas M., Benjamin C. Hall, Daniel G. McLean, Joy E. Rogers, Aaron R. Burke, Kenneth Turnbull et Andrew Weisner. « Synthesis and Characterization of Novel Platinum Acetylide Oligomers ». MRS Proceedings 771 (2003). http://dx.doi.org/10.1557/proc-771-l4.21.

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AbstractAs part of an effort to develop a spectroscopic structure-property relationship in platinum acetylide oligomers, we have prepared a series of bidentate Pt(PBu3)2L2 compounds. The ligand was the series o-syd-C6H4-CΞC-(C6H4-CΞC)n-H, n = 0,1,2. The terminal oligomer unit consisted of a sydnone group ortho to the acetylene carbon. The compounds were characterized by various methods, including 13C-NMR, ground state absorption, fluorescence, phosphorescence and laser flash photolysis. The acetylenic 13C-NMR resonances showed sydnone influences that decreased with increasing number of monomer units. The ground state absorption spectra were slightly red shifted from those of the baseline oligomers not having a sydnone group. The low temperature emission and excitation spectra showed complex dependence on excitation and emission wavelengths, suggesting the chromphores resided in a distribution of solvent environments and conformations. Finally, broad triplet state absorption spectra were observed, with absorption throughout the visible and near infrared regions.

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Vaneev, Alexander, Petr Gorelkin, Eugene Barykin, Vasilii Kolmogorov, Roman Timoshenko, Vladimir Mitkevich, Irina Petrushanko et al. « Impact of Antioxidants on Mechanical Properties and ROS levels of Neuronal Cells Exposed to β‐amyloid peptide ». ChemBioChem, 16 novembre 2024. http://dx.doi.org/10.1002/cbic.202400786.

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This study aims to investigate the potential role of antioxidants in oxidative stress and its consequent impact on the mechanical properties of neuronal cells, particularly the stress induced by amyloid‐beta (1‐42) (Aβ42) aggregates. A key aspect of our research involved using scanning ion‐conductance microscopy (SICM) to assess the mechanical properties (Young’s modulus) of neuronal cells under oxidative stress. Reactive oxygen species (ROS) level was measured in single‐cell using the electrochemical method by low‐invasive Pt nanoelectrode. We investigated the effects of the low molecular weight antioxidant N‐acetylcysteine (NAC) and the antioxidant enzyme superoxide dismutase 1 (SOD1) on the physiological and mechanical properties of neuronal cells using SICM. Using electrochemical method and SICM, NAC effectively reduces oxidative stress and restores Young's Modulus in SH‐SY5Y cells exposed to hydrogen peroxide and Aβ42 oligomers. Our study first examined the influence of SOD1 on intracellular ROS levels in the presence of Aβ oligomers. The investigation into the effects of SOD1 and its nanoparticle form SOD1 on SH‐SY5Y cells reveals impacts on mechanical properties and oxidative stress. The combined use of SICM and electrochemical measurements provided a comprehensive understanding of how oxidative stress, including that triggered by the Aβ oligomers affects the mechanical properties of cells.

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Wang, Yuehu, Feihong Tian, Peimei Guo, Dazhen Fu, Hero Jan Heeres, Taotao Tang, Huayu Yuan, Bing Wang et Jiang Li. « Catalytic liquefaction of sewage sludge to small molecular weight chemicals ». Scientific Reports 10, n^o 1 (3 novembre 2020). http://dx.doi.org/10.1038/s41598-020-75980-z.

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Abstract The catalytic hydrotreatment of sewage sludge, the wet solid byproducts from wastewater treatment plants, using supported Ir, Pt, Pd, Ru catalysts had been investigated with different solvent conditions. Reactions were carried out in a batch set-up at elevated temperatures (400 °C) using a hydrogen donor (formic acid (FA) in isopropanol (IPA) or hydrogen gas), with sewage sludge obtained from different sampling places. Sewage sludge conversions of up to 83.72% were achieved using Pt/C, whereas the performance for the others catalysts is different and solvent had a strong effect on the conversion rate and product constitution. The sewage sludge oils were characterised using a range of analytical techniques (GC, GC–MS, GCxGC, GPC) and were shown to consist of monomers, mainly alkanes and higher oligomers.

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Kirikchi, O. B., et N. Karjanto. « Correction to : Discrete solitons dynamics in $$ {\mathscr {PT}}$$-symmetric oligomers with complex-valued couplings ». Nonlinear Dynamics, 24 juin 2021. http://dx.doi.org/10.1007/s11071-021-06638-2.

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Watanabe, Honoka, Munetaka Iwamura et Koichi Nozaki. « Kinetic Analysis of Excited-State Dynamics of Emissive Oligomers of Pt(II) Complex in Solution ». Inorganic Chemistry, 13 mars 2024. http://dx.doi.org/10.1021/acs.inorgchem.3c04542.

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Blum, Yigal D., Richard M. Laine, Kenneth B. Schwartz, David J. Rowcliffe, Robert C. Bening et David B. Cotts. « A New Catalytic Method for Producing Preceramic Polysilazanes ». MRS Proceedings 73 (1986). http://dx.doi.org/10.1557/proc-73-389.

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ABSTRACTA transition metal (e.g., Ru3 (CO)12, Pt/C) catalyzed process for Si-N bond formation is discussed that provides a new route to mono-, oligo-, and polysilazanes. The catalysts function by activating Si-H bonds in the pres-ence of ammonia. Polymeric silazanes can also be produced from oligomers in the presence of ammonia at low temperatures. This method allows us to control or modify the composition of the polysilazane during or after the polymeriza-tion. A variety of polysilazanes were prepared and converted to Si3 N4 with ceramic yields ranging from 55%-85%. By varying the monomers and reaction conditions, we can control the nitrogen and carbon content in the preceramic polymers, which enables us to obtain ceramic products that are primarily Si3N4and simultaneously minimizes the coproduction of SiC and C.

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Patterson, Charles H., et Smruti Ranjan Sahoo. « Charge Transfer Excitons in π -stacked Thiophene Oligomers and P3[Alkyl]T Crystals : CIS calculations and electroabsorption spectroscopy ». Journal of Chemical Physics, 20 juillet 2022. http://dx.doi.org/10.1063/5.0098575.

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Poly(3-alkylthiophenes), P3[Alkyl]T, exhibit high mobility and efficiency of formation of polaronic chargecarriers generated by light absorption which gives them applications in field effect devices. Excited states ofπ -stacked dimers of tetra-thiophene oligomers (T4), infinite isolated polythiophene (PT) chains and P3[Alkyl]Tcrystals are modeled using configuration interaction singles (CIS) calculations. Excited states in cofacial T4dimers are mostly localized, Frenkel (FR) states except for two low energy CT exciton states which become theionization potential and electron affinity levels of T4 molecules at large dimer separation. The lowest excitedstates in infinite, isolated PT chains and P3[Alkyl]T crystals are intra-chain excitons where the electron and holeare localized on the same chain. The next lowest excited states are inter-chain, CT excitons in which electronand hole reside on neighboring chains. The former capture almost all optical oscillator strength and the lattermay be a route to efficient formation of polaronic charge carriers in P3[Alkyl]T systems. Changes in opticalabsorption energies of T4 dimers are explained as a function of molecular separation using CIS calculations withfour frontier orbitals in the active space. Shifts in optical absorption energy observed on going from isolatedchains to P3[Alkyl]T lamellar structures are already present in single-particle transition energies induced bydirect π - π interactions at short range. The electroabsorption spectrum of T4 dimers is calculated as a functionof dimer separation and states which are responsible for parallel and perpendicular components of the spectrumare identified.

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Zhang, Ruijuan, Boying Zhang, Haining Liu, Linda Jewell, Xinying Liu et Shanlin Qiao. « Homo‐Nuclear Hetero‐Atomic Conjugated Reticular Oligomers for Heterojunction : A Novel “Electron Medium” for Panel Photoelectrocatalysis ». Advanced Science, 21 octobre 2024. http://dx.doi.org/10.1002/advs.202407834.

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AbstractA substantial challenge in employing covalent organic frameworks (COFs) for photoelectrochemical (PEC) water splitting lies in improving their solution‐processability while concurrently facilitating the transfer of charges and mass to the catalytic sites. Herein, we synthesize a solution‐processable conjugated reticular oligomers (CROs), and further embed ruthenium (Ru) into the CRO, forming a CRO‐Ru with homo‐nuclear hetero‐atomic. Thereafter, CRO and CRO‐Ru construct an organic–organic heterojunction membrane at the nanoscale. This design achieves perfect lattice matching, significantly reducing the energy barrier of mass transfer, and effectively lowering the recombination rate of charge carriers. The optimized photocathode, CuI/CRO‐Bpy:CRO‐Bpy‐Ru‐1:1+P3HT/SnO2/Pt, exhibits an efficiency of 111.0 µA cm−2 at 0.4 V versus a reversible hydrogen electrode (RHE). Compared with the original bulk COFs and CROs, the efficiency is significantly improved. The apparent improvements in charge carrier separation and transfer are responsible for the high PEC activity. In the heterojunction, the incorporation of CRO‐Bpy‐Ru with a longer excited‐state lifetime and a substantial built‐in electric field has effectively accelerated the photo‐induced electron transfer from the conduction band (CB) of CRO‐Bpy to the valence band (VB) of CRO‐Bpy‐Ru, effectively suppressing the recombination of charges. These findings offer significant guidance for the design and optimization of high‐performance photoelectrochemical catalysts.

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Haseena, Sheik, et Mahesh Kumar Ravva. « Theoretical studies on donor–acceptor based macrocycles for organic solar cell applications ». Scientific Reports 12, n^o 1 (3 septembre 2022). http://dx.doi.org/10.1038/s41598-022-19348-5.

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AbstractWe have designed a series of new conjugated donor–acceptor-based macrocyclic molecules using state-of-the-art computational methods. An alternating array of donors and acceptor moieties in these macrocycle molecules are considered to tune the electronic and optical properties. The geometrical, electronic, and optical properties of newly designed macrocyclic molecules are fully explored using various DFT methods. Five conjugated macrocycles of different sizes are designed considering various donor and acceptor units. The selected donor and acceptors, viz., thiophene (PT), benzodithiophene (BDT), dithienobenzodithiophene (DTBDT), diketopyrrolopyrrole (DPP), and benzothiazole (BT), are frequently found in high performing conjugated polymer for different organic electronic applications. To fully assess the potential of these designed macrocyclic derivatives, analyses of frontier molecular orbital energies, excited state energies, energy difference between singlet–triplet states, exciton binding energies, rate constants related to charge transfer at the donor–acceptor interfaces, and electron mobilities have been carried out. We found significant structural and electronic properties changes between cyclic compounds and their linear counterparts. Overall, the cyclic conjugated D–A macrocycles’ promising electronic and optical properties suggest that these molecules can be used to replace linear polymer molecules with cyclic conjugated oligomers.

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Lin, Xiaogeng, Xingyu Ma, Yasan He, Shijun Li, Wangzhi Chen et Lei Li. « One‐pot Construction of Metal Nanoparticles Loaded COF Catalysts for Aqueous Hydrogenation Reactions ». Chemistry – A European Journal, 24 décembre 2023. http://dx.doi.org/10.1002/chem.202303505.

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The catalysis performance of metal nanoparticles (NPs) will be significantly deteriorated because of their spontaneous agglomeration during practical applications. Covalent‐organic frameworks (COFs) materials with functional groups and well‐defined channels benefit for the dispersion and anchor of metal ions and the confined growth of metal NPs, working as an ideal platform to compose catalytic systems. In this article, we report a one‐pot strategy for the preparation of metal NPs loaded COFs without the need of post‐modification. During the polymerization process, the pre‐added metal ions were stabilized by the rapidly formed COF oligomers and hardly disturb the construction of COFs. After reduction, metal NPs are uniformly anchored on the COF matrix. Eventually, a wide spectrum of metal NPs, including Au, Pd, Pt, AuPd, CuPd, CuPt and CuPdPt, loaded COFs are successfully prepared. The versatility and metal ions anchoring mechanism are verified with four different COF matrixes. Taking AuPd NPs as example, the resultant AuPd NPs loaded COF materials can selectively decompose ammonium formate and produce hydrogen in‐situ, exhibiting over 99% conversion of hydrodechlorination for chlorobenzenes and nitro‐reduction reaction for nitroaromatic compounds under ambient temperature in aqueous solution.

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Zhang, Boying, Huimin Gao, Yazhou Kang, Xiaoming Li, Qing Li, Pengda Zhai, Diane Hildebrandt, Xinying Liu, Yue Wang et Shanlin Qiao. « Molecular and Heterojunction Device Engineering of Solution‐Processed Conjugated Reticular Oligomers : Enhanced Photoelectrochemical Hydrogen Evolution through High‐Effective Exciton Separation ». Advanced Science, 7 mars 2024. http://dx.doi.org/10.1002/advs.202308535.

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AbstractCovalent organic frameworks (COFs) face limited processability challenges as photoelectrodes in photoelectrochemical water reduction. Herein, sub‐10 nm benzothiazole‐based colloidal conjugated reticular oligomers (CROs) are synthesized using an aqueous nanoreactor approach, and the end‐capping molecular strategy to engineer electron‐deficient units onto the periphery of a CRO nanocrystalline lattices (named CROs‐Cg). This results in stable and processable “electronic inks” for flexible photoelectrodes. CRO‐BtzTp‐Cg and CRO‐TtzTp‐Cg expand the absorption spectrum into the infrared region and improve fluorescence lifetimes. Heterojunction device engineering is used to develop interlayer heterojunction and bulk heterojunction (BHJ) photoelectrodes with a hole transport layer, electron transport layer, and the main active layers, using a CROs/CROs‐Cg or one‐dimensional (1D) electron‐donating polymer HP18 mixed solution via spinning coating. The ITO/CuI/CRO‐TtzTp‐Cg‐HP18/SnO2/Pt photoelectrode shows a photocurrent of 94.9 µA cm‒2 at 0.4 V versus reversible hydrogen electrode (RHE), which is 47.5 times higher than that of ITO/Bulk‐TtzTp. Density functional theory calculations show reduced energy barriers for generating adsorbed H* intermediates and increased electron affinity in CROs‐Cg. Mott‐Schottky and charge density difference analyses indicate enhanced charge carrier densities and accelerated charge transfer kinetics in BHJ devices. This study lays the groundwork for large‐scale production of COF nanomembranes and heterojunction structures, offering the potential for cost‐effective, printable energy systems.

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Kemp, James William, Jesse Lynn Reed et Brett Gibson Compton. « Size effects in 3D‐printed polymer‐derived, zirconium diboride‐reinforced ceramic composites ». Journal of the American Ceramic Society, 25 octobre 2023. http://dx.doi.org/10.1111/jace.19516.

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AbstractPreceramic polymers are of interest for use in many manufacturing techniques such as injection molding, ceramic fiber infiltration, and additive manufacturing. However, off‐gassing of low molecular weight oligomers occurs when these polymers cure, potentially leading to porosity in the cured part. To study how porosity and strength are affected by the size of the printed part, and the presence of a high surface area nano‐scale filler, polycarbosilane (PCS) microrods of varying diameter were fabricated via direct ink writing (DIW), an additive manufacturing technique, with two ink formulations containing either zirconium diboride (ZrB2) alone, or ZrB2 and fumed alumina (FA). Sets of microrods were printed in a range of sizes by using print nozzles of 450, 634, 979, 1 346, or 1 702 μm in diameter, which were thermally cured, pyrolyzed to form ceramic composite microrods, and tested in 3‐pt flexure. Porosity increased with increasing diameter, while failure strength decreased. For a given nozzle size, the microrods containing FA displayed lower porosity and higher strength (up to ∼500 MPa) compared to the microrods containing only ZrB2. Weibull strength analysis was performed on each group of microrods and shows that the addition of FA increased Weibull modulus from 4.63 ± 1.56 to 9.35 ± 0.601. In conjunction with optical microscopy, this analysis indicates two distinct flaw populations in the printed materials, porosity which arises during the curing step and cracking which arises during pyrolysis of the larger specimens.

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