TEMPO in Solution, Melted, Solid, and Adsorbed on a Silica Surface: A Paramagnetic NMR Study
Year: 2025
Type: article
Abstract: ABSTRACT TEMPO (2,2,6,6‐tetramethyl‐1‐piperidinyloxy) is a stable radical that is phenomenologically interesting and of high importance in synthesis and catalysis. This radical has been studied extensively with EPR and used as a spin tag for biological materials and to probe hydrogen bonding. The NMR properties of TEMPO have not yet been reported. This contribution describes that all 1 H and 13 C NMR signals of TEMPO are visible in the paramagnetic NMR spectra. The 1 H NMR spectra of TEMPO solutions have a chemical shift range of 50 ppm and require only 8 scans. The 13 C NMR signals are localized within a chemical shift range of 2600 ppm and are obtained within 30 minutes. Samples prepared with different solvents and TEMPO concentrations have been investigated, and it has been demonstrated that all solvents undergo chemical shift changes due to the presence of TEMPO and adduct formation in the case of CDCl 3 . The impact of TEMPO on the 31 P chemical shift of PPh 3 is studied. Higher concentrations of TEMPO in solution lead to narrower signals and the molten substance, measured at 60°C, represents the culmination of this trend. It is demonstrated with paramagnetic solid‐state NMR that TEMPO adsorbs on a silica surface and displays the chemical shift and linewidth features of a dilute solution of TEMPO.
Source: Chemistry - A European Journal
Authors: Ehsan Shakeri, Gabrielle E. Harmon‐Welch, Sara A. C. MacWade, Vladimir I. Bakhmutov, Janet Blümel
Institution: Texas A&M University
Language: English
Subfield: Spectroscopy
Field: Chemistry
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,640
OpenAlex ID: W4416824660