Abstract: Recently there has been an increased interest in the development of small molecule electrooxidation catalysts such as (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), for multistep electrochemical alcohol oxidation. TEMPO and its structural derivatives provide a method for electrochemically oxidizing short chain alcohols and various sugars to the corresponding aldehydes and ketones under metal free and mild aqueous conditions. Recent efforts have focused on the design of highly active TEMPO derivatives that that operate under a range of oxidation potentials; however, attempts to design novel nitroxyl radical-containing electrooxidation catalysts are often driven by molecular intuition and are therefore restricted by a limited understanding of structure-activity relationships in nitroxyl radical species. Consequently, there remains a need for fundamental studies to identify structural and electronic predictors of catalytic activity in structural analogues of TEMPO.
We have recently employed a combination of electroanalytical techniques and DFT computations to develop a descriptive model that correlates the electrocatalytic activity of nitroxyl radical catalysts to their redox potentials under aqueous conditions. Based on fundamental insights derived from this model, we have designed several highly active and promiscuous catalytic materials in the form of redox polymers capable of oxidizing a wide range of primary and secondary alcohols as well as several amines. In addition, we have recently aimed at enhancing the selectivity of nitroxyl radical catalysts by incorporating highly active TEMPO derivatives into the active site of an artificial thermostable protein.