Infrared Spectroscopy of Cluster Anions Containing Aromatic Molecules

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Infrared Spectroscopy of Cluster Anions
Containing Aromatic Molecules
J. Mathias Weber, JILA, NIST, and Department of
Chemistry and Biochemistry,University of
Colorado, Boulder, CO 80309-0440
Rationale Little structural information is
available on interaction motifs of anionic
clusters involving aromatic molecules.
Significance (examples) Interaction of
important anions (e.g. O2-) with functional
groups in proteins hydration of large charge
distributions substitution chemistry and
supramolecular assemblies anion molecular
recognition Approach Infrared spectroscopy of
mass selected cluster ions in a molecular beam
Some key questions
How do aromatic molecules interact with anions ?
What are the interaction motifs in substituted
benzenes?
How are aromatic anions solvated ?
Example ring-bound isomers of Cl-?C6FnH6-n
vs.
Example C6F6- monohydrate has two weak H-bonds
the anionis strongly distorted from theplanar
geometry of the neutral.
Example O2-?C6H6 structure dictated by p
orbital of O2- interaction is preferentially
with one CH group, only weakly tethered to a
neighboring CH.
H-bonded isomers of Cl-?C6FnH6-n ...H-bonding
is strongly preferred, even at high levels of
fluorination, where the electrostatic potential
is positive at the ring.