Anion-Activated Bases and Nucleophiles Characterized by Photoelectron Spectroscopy

Negative ion photoelectron spectra at 20 K along with ab initio [CCSD­(T)] and M06-2X density functional theory calculations are reported for a series of six basic and nucleophilic pyridine derivatives with an anionic substituent [i.e., 3- and 4-PyrBX3 –, where X = F, 4-t-BuC6H4, 4-MeOC6H4, and 3,5-...

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Bibliographic Details
Published in:The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2023-10, Vol.127 (42), p.8828-8833
Main Authors: Dempsey, Stephen H., Cao, Wenjin, Wang, Xue-Bin, Kass, Steven R.
Format: Article
Language:English
Subjects:
A: Structure, Spectroscopy, and Reactivity of Molecules and Clusters
Anions
Chemical structure
Energy
INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Ions
Salts
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Summary:Negative ion photoelectron spectra at 20 K along with ab initio [CCSD­(T)] and M06-2X density functional theory calculations are reported for a series of six basic and nucleophilic pyridine derivatives with an anionic substituent [i.e., 3- and 4-PyrBX3 –, where X = F, 4-t-BuC6H4, 4-MeOC6H4, and 3,5-(MeO)2C6H3]. Vertical detachment energies (VDEs) of these charge-activated reagents span from 4.50–5.85 eV and are well reproduced by M06-2X/aug-cc-pVTZ and CCSD­(T)/maug-cc-pVTZ computations. Surprisingly, the VDEs are found to correlate with the SN2 reactivity of the PPh4 + salts of the substituted pyridine anions with 1-iodooctane in dichloromethane. This provides an experimental measure of the nucleophilicity of these charge-activated anions, which represent a new class of chemical reagent.
ISSN:1089-5639
1520-5215
DOI:10.1021/acs.jpca.3c04479