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Photodetachment and Photoreactions of Substituted Naphthalene Anions in a Tandem Ion Mobility Spectrometer

Abstract

Substituted naphthalene anions (deprotonated 2-naphthol and 6-hydroxy-2-naphthoic acid) are spectroscopically probed in a tandem drift tube ion mobility spectrometer (IMS). Target anions are selected according to their drift speed through nitrogen buffer gas in the first IMS stage before being exposed to a pulse of tunable light that induces either photodissociation or electron photodetachment, which is conveniently monitored by scavenging the detached electrons with trace SF6 in the buffer gas. The photodetachment action spectrum of the 2-naphtholate anion exhibits a band system spanning 380-460\,nm with a prominent series of peaks spaced by 440 cm-1, commencing at 458.5 nm, and a set of weaker peaks near the electron detachment threshold corresponding to transitions to dipole-bound states. The two deprotomers of 6-hydroxy-2-naphthoic acid are separated and spectroscopically probed independently. The molecular anion formed from deprotonation of the hydroxy group possesses a photodetachment action spectrum similar to that of the 2-naphtholate anion with an onset at 470 nm and a maximum at 420 nm. Near threshold, a photoreaction with SF6 is observed with displacement of an OH group by an F atom. In contrast, the anion formed from deprotonation of carboxylic acid group features a photodissociation action spectrum, recorded on the CO2 loss channel, lying to much shorter wavelength with an onset at 360\,nm and maximum photo-response at 325 nm.

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Publication details

The article was received on 30 Nov 2018, accepted on 10 Jan 2019 and first published on 10 Jan 2019


Article type: Paper
DOI: 10.1039/C8FD00217G
Citation: Faraday Discuss., 2019, Accepted Manuscript

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    Photodetachment and Photoreactions of Substituted Naphthalene Anions in a Tandem Ion Mobility Spectrometer

    J. N. Bull, J. Buntine, M. Scholz, E. Carrascosa, L. Giacomozzi, M. H. Stockett and E. Bieske, Faraday Discuss., 2019, Accepted Manuscript , DOI: 10.1039/C8FD00217G

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