The Structure of the Hydrated Electron. Part 1. Magnetic Resonance of Internally Trapping Water Anions: A Density Functional Theory Study
| Autor: | I. A. Shkrob |
|---|---|
| Rok vydání: | 2007 |
| Předmět: |
Physics
FOS: Physical sciences Electron Solvated electron Molecular physics law.invention General Physics (physics.gen-ph) Physics - General Physics Solvation shell Atomic orbital law Density functional theory Water cluster Physics::Chemical Physics Physical and Theoretical Chemistry Spin (physics) Electron paramagnetic resonance |
| Zdroj: | The Journal of Physical Chemistry A. 111:5223-5231 |
| ISSN: | 1520-5215 1089-5639 |
| DOI: | 10.1021/jp068278m |
| Popis: | Density functional theory (DFT) is used to rationalize magnetic parameters of hydrated electron trapped in alkaline glasses as observed using Electron Paramagnetic Resonance (EPR) and Electron Spin Echo Envelope Modulation (ESEEM) spectroscopies. To this end, model water cluster anions (n=4-8 and n=20,24) that localize the electron internally are examined. It is shown that EPR parameters of such water anions (such as hyperfine coupling tensors of H/D nuclei in the water molecules) are defined mainly by the cavity size and the coordination number of the electron; the water molecules in the second solvation shell play a relatively minor role. An idealized model of hydrated electron (that is usually attributed to L. Kevan) in which six hydroxyl groups arranged in an octahedral pattern point towards the common center is shown to provide the closest match to the experimental parameters, such as isotropic and anisotropic hyperfine coupling constants for the protons (estimated from ESEEM), the second moment of the EPR spectra, and the radius of gyration. The salient feature of these DFT models is the significant transfer (10-20%) of spin density into the frontal O 2p orbitals of water molecules. Spin bond polarization involving these oxygen orbitals accounts for small, negative hyperfine coupling constants for protons in hydroxyl groups that form the electron-trapping cavity. In Part 2, these results are generalized for more realistic geometries of core anions obtained using a dynamic one-electron mixed qunatum/classical molecular dynamics model. Part 1 of 2; will be submitted to J Phys Chem A |
| Databáze: | OpenAIRE |
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