High-Resolution Photoelectron Spectroscopy of the Pyridinide Isomers

26 July 2019, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Isomer-specific, high-resolution photoelectron spectra of cryogenically-cooled pyridinide anions obtained using slow photoelectron velocity-map imaging are presented. New vibrational structure in the detachment spectrum of para-pyridinide is resolved, and the spectra of meta- and ortho-pyridinide are reported for the first time. These spectra yield electron affinities of 1.4797(5), 1.4473(5), and 0.8669(7) eV for the para-, meta- and ortho-pyridyl radicals, respectively, as well as a number of vibrational frequencies for each neutral isomer. While most of the resolved structure in all three spectra is readily assigned by comparison to B3LYP/6-311+G* Franck-Condon simulations, the para-pyridinide spectrum shows newly-resolved fine structure attributed to anharmonic coupling within the vibrational manifold of the corresponding neutral radical. Isomeric trends in the photoelectron angular distributions are rationalized by approximating the detached anion orbitals as superpositions of s, p, and d-like hydrogenic orbitals, based on an application of Sanov’s generalized mixing model [J. Chem. Phys. 141, 124312 (2014)]. The presented experimental and theoretical results are used to address the relative energies of the anion and neutral isomers, as well as the site-specific bond dissociation energies of pyridine.

Keywords

radicals
spectroscopy
vibrational spectroscopy
anharmonicity
pyridyl
pyridine

Supplementary materials

Title
Description
Actions
Title
pyridyl SI 3 submission
Description
Actions

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