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    Enhanced ORR Activity of Carbon Defects via Substituent-modulated Electronic Perturbation
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    Abstract:
    Fine-tuning of the p z orbital of carbon defects by ligand-modulated electronic perturbation can lead to peak ORR catalytic activity.
    Keywords:
    Carbon fibers
    Field substituent parameters of 26 substituents were calculated by ab initio calculations at the level of CBS-4M. The field substituent parameters, along with resonance substituent parameter σR, group electronegativity ι, and polarizability parameter σα, correlate well with stabilization energies (SE) of ketenimines, isocyanides, and nitriles, providing useful information about substituent electronic effects on the stability of ketenimines, isocyanides, and nitriles.
    Electronegativity
    Citations (7)
    Abstract The nature of inductive substituent effect on the gas phase acidity of several series of aliphatic carboxylic acids with rigid molecular skeletons was analyzed using the recently proposed quantum chemical approach based on the theory of proton affinity proposed by Longuet‐Higgins. The results of the analysis suggest that the substituent induced variation of the acidity is in all series due to electrostatic field‐effect which in the gas phase can reasonably be characterized by Kirkwood–Westheimer theory. Copyright © 2007 John Wiley & Sons, Ltd.
    Taft equation
    Quantum chemical
    Inductive effect
    Chemical polarity
    Citations (4)
    Abstract Ring and ester proton chemical shifts in six series of substituted methyl pyridinecarboxylates have been measured. Results for ring protons ortho and para to the substituent can generally be accounted for by additive substituent, ester and nitrogen effects. Shifts for protons meta to the substituent, when compared with analogous shifts in monosubstituted benzenes, provide evidence of substituent–nitrogen interactions. In particular, a special effect is noted for series where both the proton and substituent are adjacent to the nitrogen. The origin of this effect is discussed. The ester proton results lead to essentially the same conclusions. Although this probe is much less sensitive to substituent effects, the same special effect is evident for the methyl 6‐X‐picolinate series.
    Chemical shift
    Citations (18)
    Abstract Additivity of substituent effects in the methyl-triphenylphosphonium system with substituents on different phenyl groups is tested. Results show that additive linear free energy relationships can be applied to describe multiple substituent effects in this system.
    Additive function
    Citations (0)
    Abstract The quantum mechanically calculable Q descriptor is shown to be a potent quantifier of chemical reactivity in complex molecules – it shows a strong correlation to experimentally derived field effects in non‐aromatic substrates and Hammett σ m and σ p parameters. Models for predicting substituent effects from Q are presented and applied, including on the elusive pentazolyl substituent. The presented approach enables fast computational estimation of substituent effects, and, in extension, medium‐throughput screening of molecules and compound design. An experimental dataset is suggested as a candidate benchmark for aiding the general development and comparison of electronic structure analyses. It is here used to evaluate the experimental quantum chemistry (EQC) framework for chemical bonding analysis in larger molecules.
    Quantum Chemistry
    Quantum chemical
    Hammett equation
    Reactivity
    Citations (14)