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Infrared Predissociation Spectroscopy of M+(C6H6)1−4(H2O)1−2Ar0−1 Cluster Ions, M = Li, Na

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journal contribution
posted on 2011-05-05, 00:00 authored by Jordan P. Beck, James M. Lisy
Infrared predissociation (IRPD) spectra of Li+(C6H6)1−4(H2O)1−2Ar0−1 and Na+(C6H6)2−4(H2O)1−2Ar1 are presented along with ab initio calculations. The results indicate that the global minimum energy structure for Li+(C6H6)2(H2O)2 has each water forming a π-hydrogen bond with the same benzene molecule. This bonding motif is preserved in Li+(C6H6)3−4(H2O)2Ar0−1 with the additional benzene ligands binding to the available free OH groups. Argon tagging allows high-energy Li+(C6H6)2−4(H2O)2Ar isomers containing water−water hydrogen bonds to be trapped and detected. The monohydrated, Li+ containing clusters contain benzene−water interactions with varying strength as indicated by shifts in OH stretching frequencies. The IRPD spectra of M+(C6H6)1−4(H2O)1−2Ar are very different for lithium-bearing versus sodium-bearing cluster ions emphasizing the important role of ion size in determining the most favorable balance of competing noncovalent interactions.

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