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21.
Factors affecting the electrochemical and spectroelectrochemical properties of diruthenium(III,II) complexes containing four unsymmetrical bridging ligands are reported for seven related compounds which were isolated in one or two of the four possible isomeric forms. The investigated compounds are represented as Ru(2)(2-CH(3)ap)(4)Cl, Ru(2)(2,5-F(2)ap)(4)Cl, Ru(2)(2,6-F(2)ap)(4)Cl, and Ru(2)(2,4,6-F(3)ap)(4)Cl where 2-CH(3)ap, 2,5-F(2)ap, 2,6-F(2)ap, and 2,4,6-F(3)ap are, respectively, the 2-(2-methylanilino)pyridinate anion, the 2-(2,5-difluoroanilino)pyridinate anion, the 2-(2,6-difluoroanilino)pyridinate anion, and the 2-(2,4,6-trifluoroanilino)pyridinate anion. Ru(2)(2-CH(3)ap)(4)Cl and Ru(2)(2,5-F(2)ap)(4)Cl exist only in a (4,0) conformation while Ru(2)(2,4,6-F(3)ap)(4)Cl is present in both (3,1) and (4,0) isomeric forms. Ru(2)(2,6-F(2)ap)(4)Cl also exists in two isomeric forms, but only the (3,1) isomer was generated in sufficient quantities to be isolated and structurally characterized. This series of seven closely related metal-metal bonded complexes thus provides the first possibility to systematically examine how differences in position and number of the electron-donating or electron-withdrawing groups on the anionic bridging ligands might be related to the electronic properties and structural features of the compound as well as the type and number of geometric isomers which are formed. Each diruthenium derivative undergoes three one-electron transfers in CH(2)Cl(2) containing 0.1 M tetra-n-butylammonium perchlorate (TBAP). The first reduction and first oxidation products were characterized by thin-layer UV-vis spectroelectrochemistry, and the spectroscopic data, along with E(1/2) values, were then related via linear free energy relationships to the type of isomer and/or position of the electron-donating or electron-withdrawing substituents on the anionic ap bridge. The electrogenerated Ru(2)(6+) and Ru(2)(4+) forms of the compounds were assigned on the basis of electrochemical and UV-vis spectroscopic data as having the electronic configuration sigma(2)pi(4)delta(2)pi(2) and sigma(2)pi(4)delta(2)pi(3)delta, respectively, and seemed to be independent of the isomer type ((3,1) or (4,0)). The spectral and electrochemical properties of the compounds both vary substantially as a function of the isomer type, but this is not reflected in the structural features of the compounds which are within the range of what is seen for other Ru(2)(5+) species described in the literature. The Ru-Ru bond lengths of the four structurally characterized (4,0) isomers of the ap complexes range from 2.275 to 2.296 A while those of the three structurally characterized (3,1) isomers of ap derivatives fall in the range 2.284-2.286 A and show no significant difference among the three compounds. The Ru-Cl bond lengths of the (3,1) isomers do not vary significantly with the bridging ligand and range from 2.458 to 2.471 A whereas those of the (4,0) isomers range from 2.437 to 2.487 A and show larger variations among the compounds. The Ru-Ru-Cl bond angle is virtually independent of the bridging ligand in the case of the (4,0) isomers but decreases with the electron-withdrawing effect of the substituent in the case of the (3,1) isomers. 相似文献
22.
Bonhommeau S Bréfuel N Pálfi VK Molnár G Zwick A Salmon L Tuchagues JP Sanchez Costa J Létard JF Paulsen H Bousseksou A 《Physical chemistry chemical physics : PCCP》2005,7(15):2909-2914
A quasi-quantitative photo-induced low-spin (LS)-->high-spin (HS) conversion of FeII ions has been observed in the [Fe(TRIM)2]Cl2 complex by irradiating the sample with blue light (488 nm) at 10 K. The time dependence of the HS-->LS relaxation has been studied between 10 K and 44 K by means of magnetic susceptibility measurements. These relaxation curves could be satisfactorily fitted by mono-exponential decays including tunnelling effect except for temperatures below 30 K. The introduction of a distribution of vibrational frequencies into this model improved significantly the fits in the low-temperature range and gave a good agreement with the experimental data in the whole temperature range suggesting a multi-rate relaxation process in this complex. 相似文献
23.
Antoine Versini Lou Saier Fabien Sindikubwabo Sebastian Müller Tatiana Cañeque Raphaël Rodriguez 《Tetrahedron》2018,74(39):5585-5614
Cancer stem cells (CSC) have been shown to be refractory to conventional therapeutic agents, can promote metastasis, and have been linked to cancer relapse. The natural product Salinomycin has been identified by means of high throughput phenotypic screening as a selective killer of CSC in vitro and in vivo. In this article we comprehensively review the chemistry of Salinomycin, documenting early total syntheses, along with strategies that have been developed over the years to effectively modify this natural product at key positions with the view to establish a robust structure-activity-relationship and to delineate the complex mechanism of action of this fascinating molecule in the context of cancer research. Then, we document the biology of Salinomycin, putting forward phenotypic alterations that have been observed in the relevant biological models and highlighting how chemistry has been instrumental in discovering unprecedented physiological features of cancer stem cells that can be exploited for therapeutic benefits. 相似文献
24.
Dr. Justine Harmel Dr. Laurent Peres Dr. Marta Estrader Adrien Berliet Dr. Sylvie Maury Dr. Antoine Fécant Dr. Bruno Chaudret Prof. Dr. Philippe Serp Dr. Katerina Soulantica 《Angewandte Chemie (International ed. in English)》2018,57(33):10579-10583
The Fischer–Tropsch synthesis (FTS) is a structure‐sensitive exothermic reaction that enables catalytic transformation of syngas to high quality liquid fuels. Now, monolithic cobalt‐based heterogeneous catalysts were elaborated through a wet chemistry approach that allows control over nanocrystal shape and crystallographic phase, while at the same time enables heat management. Copper and nickel foams have been employed as supports for the epitaxial growth of hcp‐Co nanowires directly from a solution containing a coordination compound of cobalt and stabilizing ligands. The Co/Cufoam catalyst was tested for Fischer–Tropsch synthesis in a fixed‐bed reactor, showing stability and significantly superior activity and selectivity towards C5+ compared to a Co/SiO2‐Al2O3 reference catalyst under the same conditions. 相似文献
25.
Antoine Busseau Dr. Carmen Villegas Dr. Sylvie Dabos‐Seignon Dr. Clément Cabanetos Prof. Piétrick Hudhomme Dr. Stéphanie Legoupy 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(25):8452-8456
New penta(organo)fullerenes donor–acceptor systems bearing five tetrathiafulvalene recognition units have been synthesized to promote self‐assemblies similar in appearance to shuttlecocks nested into each other thanks to the conical host cavity created around the fullerene together with the π–π and electronic interactions. 相似文献
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29.
Antoine Tiya Djowe Samuel Laminsi Daniel Njopwouo Elie Acayanka Eric M. Gaigneaux 《Plasma Chemistry and Plasma Processing》2013,33(4):707-723
Smectite clay from Sabga (west-Cameroon) was treated in aqueous suspension by gliding arc plasma to modify its surface properties. The evolution of the modifications was followed with the exposure time and post-discharge duration using Fourier transformed infra red spectroscopy and scanning electron microscopy. X-ray diffraction and nitrogen physisorption analyses were also performed to evaluate if both crystalline and textural properties of the material are affected by the treatment. The results obtained show that the plasma treatment causes the breakdown of structural bounds at the clay surface and induces the formation of new hydroxyl groups (Si–OH and Al–OH) on the clay edges. Crystallinity, sheet structure and textural properties are not significantly affected by the plasma treatment. However, it should be noted that an intensive treatment of the clay lowers the pH of the suspension, which subsequently induces an acid attack of the clay. In such case, the specific surface area of the clay increases. This study demonstrates that gliding arc plasma treatments can be used to activate clay minerals for environmental application. 相似文献
30.
Sakey Ravindra Kokkarachedu Varaprasad V. Rajinikanth Antoine F. Mulaba-Bafubiandi Koduri Venkata Surya Ramam 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):1230-1240
Design of silver nanoparticles containing poly(N-isopropylarclamide) (PNIPAAm) hydrogels were prepared by free-radical polymerization of N-isopropylarclamide as an environmentally sensitive monomer and MBA as a crosslinker in an aqueous medium. The embedded silver nanocomposite hydrogels (AgNCH) structure were characterized by, UV-Vis, FTIR, DLS, TEM and X-ray analysis. Curcumin loading and release characteristics were performed for PNIPAAm hydrogel, silver ions loaded hydrogels as well as silver nanocomposite hydrogels. These curcumin loaded silver nanocomposite hydrogels exhibit excellent antibacterial action on Escherichia coli (E. coli). Therefore, the present study clearly provides novel antimicrobial hydrogels which are potentially useful in biomedical applications. 相似文献