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Polyanionic Aryl Ether Metallodendrimers Based on Cobaltabisdicarbollide Derivatives. Photoluminescent Properties

16-04-2013 14-06-54

E. J. Juárez-Pérez, C. Viñas, F. Teixidor, R. Santillan, N. Farfán, A. Abreu, R. Yépez and R. Núñez* Macromolecules, 2010, 43 (1), pp 150–159 Fluorescent Fréchet-type poly(aryl ether) dendrimers that incorporate the 1,3,5-triphenylbenzene as core molecule and 3, 6, 9, or 12 terminal allyl ether groups have been prepared in very good yield by following the Fr echet convergent approach. Regiospecific hydrosylilation reactions on the allyl ether functions with the cobaltabisdicarbollide derivative Cs[1,10-μ-SiMeH-3,30-Co(1,2-C2B9H10)2] lead to different generations of Fréchet-type polyanioic metallodendrimers decorated with 3, 6, and 9 cobaltabisdicarbollide units. Starting dendrimers exhibit photoluminescence properties at room temperature under ultraviolet irradiation; nevertheless, after functionalization with cobaltabisdicarbollide derivatives, the fluorescence properties are quenched. Products are fully characterized by FTIR, NMR, and UV-vis spectroscopies. For metallodendrimers, the UV-vis absorptions have been a good tool for estimating the experimental number of cobaltabisdicarbollide units peripherally attached to the dendrimeric structure and consequently to corroborate the unified character of the dendrimers. Because of the anionic character of these compounds and the boron-rich content, we actually focus our research on biocompatibility studies and potential applications.

In search of an optimized electrolyte for Na-ion batteries

16-04-2013 13-52-25

Alexandre Ponrouch,*ac Elena Marchante,ac Matthieu Courty,bc Jean-Marie Tarasconbc and M. Rosa Palac ın*ac

Energy Environ. Sci., 2012,5, 8572-8583

DOI: 10.1039/C2EE22258B

Electrolytes are essential for the proper functioning of any battery technology and the emerging Na-ion technology is no exception. Hence, a major focus on battery research is to identify the most appropriate formulation so as to minimize interface reactions and enhance both cell performances and safety aspects. In order to identify suitable electrolyte formulations for Na-ion chemistry we benchmarked various electrolytes containing diverse solvent mixtures (cyclic, acyclic carbonates, glymes) and Na-based salts having either F-based or perchlorate anions and measured viscosity, ionic conductivity, and thermal and electrochemical stability. The binary EC:PC solvent mixture has emerged as the best solvent formulation and has been used to test the performance of Na/hard carbon cells with both NaClO4 and NaPF6 as dissolved salts. Hard carbon electrodes having reversible capacities of 200 mA h g−1 with decent rate capability and excellent capacity retention (>180 cycles) were demonstrated. Moreover, DSC heating curves demonstrated that fully sodiated hard carbon cycled in NaPF6–EC:PC exhibits the highest exothermic onset temperature and nearly the lowest enthalpy of reaction, thus making this electrolyte most attractive for the development of Na-ion batteries.

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