Communication: vibrational study of a benzyl carbanion: deprotonated 2,4-dinitrotoluene.

The bare deprotonated 2,4-dinitrotoluene [DNT-H](-) anion, formed by electrospray ionization and trapped in a Paul ion-trap, has been investigated by IR multiple photon dissociation (IRMPD) spectroscopy and quantum chemical calculations at the B3LYP∕6-311++G** level. IRMPD spectra were recorded in the 950-1800 cm(-1) fingerprint range and interpreted by comparison with the calculated IR absorption spectra for different low-lying isomers. The sampled [DNT-H](-) species is found to involve deprotonation at the methyl group, yielding a benzyl carbanion 1', previously described as an amine complex in solution and here characterized by vibrational spectroscopy as an unperturbed gaseous species. Anion 1' is the most stable species among [DNT-H](-) isomers.