Competition between N and O: use of diazine N-oxides as a test case for the Marcus theory rationale for ambident reactivity

Links among the Fukui potential, the alchemical hardness and the local hardness of an atom in a molecule

This paper presents a brief summary of the difficulty that resides in the definition of the elusive concept of local chemical hardness. We argue that a definition of local hardness should be useful to a reactivity principle and not just as a mere definition. We then continue with a formal discussion about the benefits and difficulties of using the Fukui potential, which is interpreted as an alchemical derivative (alchemical hardness), as descriptor of local hardness of molecules. Computational evidence shows that the alchemical hardness is at least as good a descriptor as the combination of other two well-stabilized descriptors of local hardness, such as the Fukui function and grand canonical local hardness. Although our results are auspicious for the alchemical hardness as descriptor of local hardness, we finish by calling the attention of the community on the importance of discussing the raison d'être of a local hardness function and its main characteristics. We suggest that an axiomatic construction of local hardness could be they way of constructing a local hardness which is both useful and free of arbitrariness.

Molecularly Compensated Pre-Metallation Strategy for Metal-Ion Batteries and Capacitors

The use of a sacrificial cathode additive as a pre-metallation method could ensure adequate metal sources for advanced energy storage devices. However, this pre-metallation technique suffers from the precise regulation of decomposition potential of additive. Herein, a molecularly compensated pre-metallation (Li/Na/K) strategy has been achieved through Kolbe electrolysis, in which the electrochemical oxidation potential of a metal carboxylate is manipulated by the bonding energy of the oxygen-metal (O-M) moiety. The electron-donating effect of the substituent and the low charge density of the cation can dramatically weaken the O-M bond strength, further bringing out the reduced potential. Thus, sodium acetate exhibits a superior pre-sodiation feature for sodium-ion battery accompanied with a large irreversible specific capacity of 301.8 mAh g^-1 , remarkably delivering 70.6 % enhanced capacity retention in comparison to the additive-free system after 100 cycles. This methodology has been extended to construct a high-performance lithium-ion battery and a lithium/sodium/potassium-ion capacitor.