Isomer-Selective Generation and Spectroscopic Characterization of Picolyl Radicals

Nitrogen-containing resonance-stabilized radicals such as the picolyl radical are important in combustion chemistry and astrochemistry. They have only been scarcely studied because an isomer-selective generation is often difficult. Herein, we present threshold photoelectron spectra of the three picolyl radical isomers, C₆ H₆ N, that were obtained with synchrotron radiation. The radicals were selectively generated by flash pyrolysis from aminomethylpyridine precursors through deamination. Ionization energies of 7.70, 7.59, and 8.01 eV were determined for 2-, 3-, and 4-picolyl, respectively. The observed vibrational structure was assigned to an in-plane deformation mode of the aromatic ring. The spectroscopic insight gained in this study can be used to distinguish different picolyl isomers in on-line combustion analysis, for example.