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The interaction between aluminum cations and acetone is studied in the gas phase via photodissociation vibrational spectroscopy from 1100 to 2000 cm-1. Spectra of Al+(acetone)(N2) and ions with the stoichiometry of Al+(acetone)n (n=2-5) were measured. The experimental results are compared to DFT calculated vibrational spectra to determine the structures of the complexes. The spectra show a red shift of the C=O stretch and a blue shift of the CCC stretch which decrease as the size of the clusters increases. The calculations predict that the most stable isomer for n≥3 is a pinacolate in which oxidation of the Al+ enables reductive C-C coupling between two acetone ligands. Experimentally, pinacolate formation is observed for n=5, as evidenced by a new peak observed at 1185 cm-1 characteristic of the pinacolate C-O stretch.
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How the nature and charge of metal cations affect vibrations in acetone solvent molecules
Vibrational spectra of a series of gas-phase metal 1+ and 2+ ions solvated by acetone molecules are collected to investigate how the metal charge, number of solvent molecules and nature of the metal affect the acetone. The spectra of Cu+(Ace)(N2)2, Cu+(Ace)4, and M2+(Ace)4, where M = Co, Ni, Cu, and Zn are measured via photodissociation by monitoring fragment ion signal as a function of IR wavenumber. The spectra show a red shift of the C=O stretch and a blue shift of the C–C antisymmetric stretch. DFT calculations are carried out to provide the simulated spectra of possible isomers to be compared with the observed vibrational spectra, and specific structures are proposed. The red shift of the C=O stretch increases as the number of acetone molecules decreases. Higher charge on the metal leads to a larger red shift in the C=O stretch. Although all of the M2+ complexes have very similar red shifts, they are predicted to have different geometries due to their different electron configurations. Unexpectedly, we find that the calculated red shift in the C=O stretch in M+/2+(Ace) is highly linearly correlated with the ionization energy of the metal for a wide range of metal cations and dications.
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- Award ID(s):
- 2154391
- PAR ID:
- 10519076
- Publisher / Repository:
- RSC
- Date Published:
- Journal Name:
- Physical Chemistry Chemical Physics
- Volume:
- 26
- Issue:
- 4
- ISSN:
- 1463-9076
- Page Range / eLocation ID:
- 3101 to 3109
- Subject(s) / Keyword(s):
- vibrational spectroscopy intermolecular forces solvation
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D3CP05204D
