Isomer-Specific Spectroscopy of Benzene-(H2O)n, n = 6,7: Benzene's Role in Reshaping Water's Three-Dimensional Networks.
The water hexamer and heptamer are the smallest sized water clusters that support three-dimensional hydrogen-bonded networks, with several competing structures that could be altered by interactions with a solute. Using infrared-ultraviolet double resonance spectroscopy, we record isomer-specific OH stretch infrared spectra of gas-phase benzene-(H2O)(6,7) clusters that demonstrate benzene's surprising role in reshaping (H2O)(6,7). The single observed isomer of benzene-(H2O)6 incorporates an inverted book structure rather than the cage or prism. The main conformer of benzene-(H2O)7 is an inserted-cubic structure in which benzene replaces one water molecule in the S4-symmetry cube of the water octamer, inserting itself into the water cluster by engaging as a π H-bond acceptor with one water and via C-H···O donor interactions with two others. The corresponding D(2d)-symmetry inserted-cube structure is not observed, consistent with the calculated energetic preference for the S4 over the D(2d) inserted cube. A reduced-dimension model that incorporates stretch-bend Fermi resonance accounts for the spectra in detail and sheds light on the hydrogen-bonding networks themselves and on the perturbations imposed on them by benzene.
†Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States.
Daniel P
DP
Tabor
‡Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, United States.|§Department of Chemistry, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, 739-8526, Japan.
Ryoji
R
Kusaka
‡Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, United States.
Patrick S
PS
Walsh
†Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States.
Edwin L
EL
Sibert
‡Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, United States.
Timothy S
TS
Zwier
benzene−water