Intramolecular Coulomb repulsion and anisotropies of the repulsive Coulomb barrier in multiply charged anions

Journal Article · Sat Jul 08 04:00:00 EDT 2000 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.481842· OSTI ID:20217024

Wang, Xue-Bin ^[1]; Nicholas, John B ^[2]; Wang, Lai-Sheng ^[1]

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1. Department of Physics, Washington State University, 2710 University Drive, Richland, Washington 99352 (United States)
2. Theory, Modeling, and Simulation, W. R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, MS K1-83, P.O. Box 999, Richland, Washington 99352 (United States)

Photoelectron spectra of the three isomers of the benzene dicarboxylate dianion (o-, m-, and p-BDC{sup 2-}) were measured in the gas phase at five photon energies. Detachment features from the carboxylate groups and the {pi} electrons of the ring were clearly observed and distinguished. The electron binding energies were found to increase from the very small value of {approx}0.2 eV in o-BDC{sup 2-} to about 1.0 eV in p-BDC{sup 2-}, due to the reduced Coulomb repulsion as the two excess charges become farther apart. We found that the repulsive Coulomb barrier (RCB) for detaching electrons from the carboxylates decreases from o-BDC{sup 2-} to p-BDC{sup 2-}. However, the RCB for detaching the ring {pi} electrons was found to be significantly higher and remain constant for the three isomers. This distinct anisotropy in the RCB involving different detachment channels is related to the different intramolecular Coulomb repulsions experienced by electrons localized on the carboxylates and the ring. Theoretical calculations were performed to obtain the equilibrium structures of both the dianions and the monoanions and to gain insight into the intramolecular electrostatic interactions. The two carboxylates in m- and p-BDC{sup 2-} were shown to be in-plane with the ring whereas the strong Coulomb repulsion in o-BDC{sup 2-} forces the carboxylate groups out of the plane of the ring. The theoretical results clearly show the localized nature of the excess charges on the carboxylates and help us understand the intramolecular Coulomb repulsions within the three dianions. (c) 2000 American Institute of Physics.

• OSTI ID: 20217024
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 2 Vol. 113; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ANIONS
AROMATICS
COULOMB FIELD
ELECTRON DETACHMENT
EXPERIMENTAL DATA
MULTICHARGED IONS
PHOTOELECTRON SPECTROSCOPY