Coordination versus solvation in Al(+)(benzene)(n) complexes studied with infrared spectroscopy
Kimberly N Reishus1, Antonio D Brathwaite, Jonathan D Mosley
1Department of Chemistry, University of Georgia , Athens, Georgia 30602, United States.
The Journal of Physical Chemistry. A
|March 13, 2014
Summary
Singly charged aluminum-benzene complexes show unique vibrational patterns. Three benzene molecules primarily coordinate around the aluminum cation, with a fourth acting as a solvent.
Area of Science:
- Physical Chemistry
- Spectroscopy
- Computational Chemistry
Background:
- Aluminum-benzene cation complexes are of interest for understanding metal-ligand interactions.
- Previous studies have explored similar metal-aromatic systems.
Purpose of the Study:
- To characterize the structures and vibrational spectra of aluminum-benzene cation complexes (Al+)(benzene)n, where n = 1-4.
- To elucidate the coordination behavior of benzene molecules around a central aluminum cation.
Main Methods:
- Production of ions via laser vaporization in a pulsed supersonic expansion.
- Mass selection and infrared laser photodissociation spectroscopy.
- Density functional theory (DFT) calculations for structures, energetics, and vibrational spectra.
Main Results:
- Observed C-H stretching bands in spectra resemble the Fermi triad of benzene.
- Strong bands for C-C ring motion (ν19) and out-of-plane hydrogen bend (ν11) were identified.
- Hydrogen bend is blue-shifted, while C-C ring distortion shows a slight red-shift compared to benzene.
Conclusions:
- Experimental and computational data suggest three benzene molecules coordinate around the Al+ cation.
- The Al+(benzene)4 complex includes a fourth benzene molecule acting as a second-sphere solvent.
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