sc9b07650_si_001.pdf (1.33 MB)
Ionic Liquid Stabilized 2,2,6,6-Tetramethylpiperidine 1‑Oxyl Catalysis for Alcohol Oxidation
journal contribution
posted on 2020-03-09, 14:06 authored by Min Li, Kevin Klunder, Emmy Blumenthal, Matthew B. Prater, Jack Lee, John E. Matthiesen, Shelley D. MinteerN-Oxyl reagents, particularly 2,2,6,6-tetramethylpiperidine
1-oxyl (TEMPO), have been extensively used for alcohol oxidations.
While TEMPO-mediated oxidations are kinetically and thermodynamically
favorable in high-pH electrolytes, base-induced degradation often
results in significant loss of catalytic activity. Herein, we demonstrate
enhanced alkaline stability of a TEMPO derivative in ionic liquids
(ILs). By incorporating TEMPO in an imidazole-anchored IL, no loss
of current was observed at pH 10.0 after 2.0 h during the oxidation
of butanol and glycerol, while TEMPO in polycaprolactone (PCL), a
patternable binder material, degraded 58.5% and 67.1%, respectively.
The stability enhancement was further demonstrated by analyzing the
conversion of glycerol in an 800 μL electrochemical cell using
bulk chemical analysis techniques. Successive cycles of glycerol oxidation
indicated 14-fold stability enhancement by applying IL in a TEMPO
electrode composite in comparison to PCL. The strategy demonstrated
here provides an opportunity to prepare catalytic systems with enhanced
stability. Further, this method provides the ability to convert what
are typically homogeneous catalysts to heterogeneous systems.