A chemical theory for molecules at electrochemical interfaces

What is it about?

Over the past decade, chemists across diverse disciplines have become increasingly excited about using electrodes as tunable functional groups. This excitement stems from the ability to modulate the chemical properties of molecules immobilized on electrode surfaces simply by applying voltage. Elucidating the role of voltage is essential when designing applications of this intriguing technique. By establishing a connection between the applied voltage with the corresponding number of electrons, we present fractional charge density functional theory coupled with a model electrode and a continuum model solvent (FC-DFT+) – a powerful quantum chemical method constructed within the canonical ensemble – for predicting the voltage-induced shift of molecular properties. Guided by FC-DFT+ calculations for 4-mercaptobenzonitrile, we provide a theoretical framework for unraveling the two main effects of applied voltage, namely electro-inductive and electric field effects, for a comprehensive understanding of the net voltage effect. We further demonstrate the general applicability of FC-DFT+ by predicting the trend of nitro stretching frequency by 4-nitrobenzenethiol and the Lewis adduct formation by 4-mercaptopyridine, each of which is dominated by electro-inductive and electric field effect, respectively.

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Photo by Blaz Erzetic on Unsplash

Photo by Blaz Erzetic on Unsplash