Theoretical investigation on two different mechanisms of fulleropyrrolidine formation

International audienceFulleropyrrolidine synthesis by photo-addition of glycine methyl ester (GME) to [60] fullerene has been recently realized and experimentally studied. Two possible hypotheses were suggested for its formation pathway, but there was no consensus about the most favorable one. Thus, in order to find the most probable mechanism, we performed a detailed theoretical investigation of the reaction between GME and [60] fullerene studying both mechanisms suggested experimentally. The first hypothesis involves two additions of two GME radicals in two steps to C-60 followed by a NH3 departure, whereas the second one involves azomethine ylide formation in a first step and followed by a cycloaddition to [60] fullerene. All the transition states and the intermediates in the reaction steps for both mechanisms were determined. The energetic profiles of both mechanisms were drawn and compared. Several levels of theory were used for the purpose, with the aim to investigate which low-cost level is sufficient to settle and which mechanism is probably involved. For the purpose, semiempirical (AM1), DFT on geometries optimized at AM1 level, and finally DFT on geometries optimized at DFT level were considered. At DFT level, GGA (PBE), hybrid (PBE0) and meta-GGA (M06-2X) were used, with a 6-31+ G(d) basis set. We proved that the release of NH3 and the ring formation step in the first mechanism require a higher energy barrier compared to the second mechanism reaction steps like tautomerization and H2O departure. Thus, we can conclude that the second mechanism involving in a first step the azomethine ylide formation is more favorable than the first mechanism. The interest in using in a first step a semiempirical determination of reaction paths is highlighted, and the choice of the exchange-correlation functional is discussed

Adsorption of CO₂ on ZSM-5 Zeolite: Analytical Investigation via a Multilayer Statistical Physics Model

In this paper, a synthesized zeolite (ZSM-5) is used as an adsorbent to analyze the adsorption phenomenon of carbon dioxide. This investigation, based on the statistical physics treatment, applied the multilayer model with saturation to understand the CO2 adsorption on four samples, namely M-ZSM-5 (M = Na+, Mg2+, Zn2+, La3+), at various temperatures T = 0 °C, 30 °C and 60 °C. The modeling results indicated that CO2 adsorption occurred via a non-parallel orientation on the ZSM-5 surface. The CO2 adsorption capacities varied from 26.14 to 28.65 cm3/g for Na-ZSM-5, from 25.82 to 27.97 cm3/g for Mg-ZSM-5, from 54.82 to 68.63 cm3/g for La-ZSM-5 and from 56.53 to 74.72 cm3/g for Zn-ZSM-5. Thus, Zn-ZSM-5 exhibits the highest adsorption amount. The analysis of the adsorption energies shows that the adsorption of CO2 on ZSM-5 zeolite is a physisorption phenomenon that could be controlled thanks to the energy parameters obtained via the numerical findings using the multilayer statistical model. Finally, the distribution of site energy was determined to confirm the physical character of the interactions between adsorbate/adsorbent and the heterogeneity of the zeolite surface

Photoionization of Benzophenone in the Gas Phase: Theory and Experiment

International audienc