Electron-Withdrawing Effects in the Photodissociation of CH2ICl To Form CH2Cl Radical, Simultaneously Viewed Through the Carbon K and Chlorine L2,3 X‑ray Edges

Zheyue Yang; Kirsten Schnorr; Aditi Bhattacherjee; Pierre-Louis Lefebvre; Michael Epshtein; Tian Xue; John F Stanton; Stephen R Leone

doi:10.1021/jacs.8b08303

Journal article

Electron-Withdrawing Effects in the Photodissociation of CH2ICl To Form CH2Cl Radical, Simultaneously Viewed Through the Carbon K and Chlorine L2,3 X‑ray Edges

Zheyue Yang, Kirsten Schnorr, Aditi Bhattacherjee, Pierre-Louis Lefebvre, Michael Epshtein, Tian Xue, John F Stanton and Stephen R Leone

Journal of the American Chemical Society, Vol.140(41), pp.13360-13366

10/17/2018

DOI: 10.1021/jacs.8b08303

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Abstract

A fundamental chlorine-containing radical, CH2Cl, is generated by the ultrafast photodissociation of CH2ICl at 266 nm and studied at both the carbon K edge (∼284 eV) and chlorine L2,3 edge (∼200 eV) by femtosecond X-ray transient absorption spectroscopy. The electronic structure of CH2Cl radical is characterized by a prominent new carbon 1s X-ray absorption feature at lower energy, resulting from a transition to the half-filled frontier carbon 2p orbital (singly occupied molecular orbital of the radical; SOMO). Shifts of other core-to-valence absorption features upon photodissociation of CH2ICl to yield ·CH2Cl indicate changes in the energies of core-level transitions of carbon and chlorine to the σ*(C–Cl) valence orbital. When the C–I bond breaks, loss of the electron-withdrawing iodine atom donates electron density back to carbon and shields the carbon 1s core level, resulting in a ∼0.8 eV red shift of the carbon 1s to σ*(C–Cl) transition. Meanwhile, the 2p inner shell of the chlorine atom in the radical is less impacted by the iodine atom removal, as demonstrated by the observation of a ∼0.6 eV blue shift of the transitions at the chlorine L2,3 edges, mainly due to the stronger C–Cl bond and the increased energy of the σ*(C–Cl) orbital. The results suggest that the shift in the carbon 1s orbital is greater than the shift in the σ*(C–Cl) orbital upon going from the closed-shell molecule to the radical. Ab initio calculations using the equation of motion coupled-cluster theory establish rigorous assignment and positions of the X-ray spectral features in the parent molecule and the location of the SOMO in the CH2Cl radical.

Details

Title: Subtitle: Electron-Withdrawing Effects in the Photodissociation of CH2ICl To Form CH2Cl Radical, Simultaneously Viewed Through the Carbon K and Chlorine L2,3 X‑ray Edges
Creators: Zheyue Yang - Lawrence Berkeley National Laboratory
Kirsten Schnorr - Lawrence Berkeley National Laboratory
Aditi Bhattacherjee - Lawrence Berkeley National Laboratory
Pierre-Louis Lefebvre - Quantum Theory Project, Departments of Chemistry and Physics
Michael Epshtein - Lawrence Berkeley National Laboratory
Tian Xue - Lawrence Berkeley National Laboratory
John F Stanton - Quantum Theory Project, Departments of Chemistry and Physics
Stephen R Leone - Department of Physics
Resource Type: Journal article
Publication Details: Journal of the American Chemical Society, Vol.140(41), pp.13360-13366
DOI: 10.1021/jacs.8b08303
ISSN: 0002-7863
eISSN: 1520-5126
Publisher: American Chemical Society
Grant note: DOI: 10.13039/100006151, name: Basic Energy Sciences, award: DE-AC02-05CH11231, DE-FG02-07ER15884; DOI: 10.13039/501100001663, name: Volkswagen Foundation
Language: English
Date published: 10/17/2018
Academic Unit: Chemistry
Record Identifier: 9984216676602771

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