RESUMEN
This investigation demonstrates that a series of (highly) substituted acephenanthrylenes (APs) 2, benzo[l]acephenanthrylene 3, and dicyclopenta[cd,mn]pyrene 4 are easily prepared by palladium-catalyzed cycloaromatization of 2,3-diethynylbiphenyls 1. The first nonpyrolysis synthesis of 4 by two-fold cycloaromatization was achieved in a high yield. This synthetic protocol has two crucial advantages: facile introduction of various substituents and efficient extension of the AP backbone.
RESUMEN
In the search for efficient and inexpensive electrocatalysts for the hydrogen evolution reaction (HER), the hydrogen binding energy is often used as a descriptor to represent the catalytic activity. The success of this approach relies on the Brønsted-Evans-Polanyi (BEP) relationship. In this study, we used constant electrode potential density functional theory calculations to examine this relationship. Eight fcc metals with a low hydrogen adsorption concentration of 1/9 were used as the model systems. We found that the HER kinetic barriers are indeed correlated to the . Both the s of the hollow site and less favourable top site correlate to the kinetic barriers; however, the correlation is better for the latter. This behaviour leads to a set of equations for estimating the HER kinetic barriers with improved accuracy that can be used to predict the HER performance of the materials with a low hydrogen adsorption concentration. This work demonstrates the importance of calculating the of a suitable adsorption site to establish good BEP relationships.
RESUMEN
To replace the oxygen evolution reaction with thermodynamically more favorable and economically more profitable methane and ethane (the major components of natural gas) electrochemical partial oxidation, we employed constant electrode potential density functional theory calculations to screen 20 one-dimensional metal-organic frameworks containing heteroatom-substituted benzene as electrocatalysts. By computing the Pourbaix diagrams, O-H binding energies, and C-H activation barriers, we determined that although none of these catalysts were able to activate methane, one was able to hydroxylate ethane to ethanol with facile kinetics, making it a promising electrocatalyst for natural gas oxidation.
RESUMEN
1-Butyl-3-methylimidazolium hexafluorophosphate ([C4MIM][PF6])/DNA and 1-methyl-3-propylimidazolium hexafluorophosphate ([C3MIM][PF6])/DNA mixtures were prepared and characterized by high-pressure infrared spectroscopy. Under ambient pressure, the imidazolium C2-H and C4,5-H absorption bands of [C4MIM][PF6]/DNA mixture were red-shifted in comparison with those of pure [C4MIM][PF6]. This indicates that the C2-H and C4,5-H groups may have certain interactions with DNA that assist in the formation of the ionic liquid/DNA association. With the increase of pressure from ambient to 2.5 GPa, the C2-H and C4,5-H absorption bands of pure [C4MIM][PF6] displayed significant blue shifts. On the other hand, the imidazolium C-H absorption bands of [C4MIM][PF6]/DNA showed smaller frequency shift upon compression. This indicates that the associated [C4MIM][PF6]/DNA conformation may be stable under pressures up to 2.5 GPa. Under ambient pressure, the imidazolium C2-H and C4,5-H absorption bands of [C3MIM][PF6]/DNA mixture displayed negligible shifts in frequency compared with those of pure [C3MIM][PF6]. The pressure-dependent spectra of [C3MIM][PF6]/DNA mixture revealed spectral features similar to those of pure [C3MIM][PF6]. Our results indicate that the associated structures of [C4MIM][PF6]/DNA are more stable than those of [C3MIM][PF6]/DNA under high pressures.