Chemistry Faculty Publications

Document Type



The water-containing clusters of oxindole (OI) and 3,4-dihydro-2(1H)-quinolinone (DQ) have been studied in the hydride stretch region of the infrared by the technique of resonant ion-dip infrared spectroscopy (RIDIRS). Both OI and DQ are constrained cis-amides with adjacent N-H and C=O groups between which water can form H-bonded bridges. The hydride stretch fundamentals of OI-W-n with n = 1-3 and DQ-W-n with n = 1, 2 without exception divide up into free OH stretch fundamentals near 3700 cm(-1) and a set of H-bonded bridge fundamentals in the 3200-3450 cm(-1) region. The bridge fundamentals show a distribution of intensities that reflects strong coupling among the XH oscillators in the bridge. When more than one water is involved in the bridge, the bridge fundamentals are unusually broad, with widths of 50-80 cm(-1) full width at half-maximum. Minimum-energy structures, binding energies, vibrational frequencies, and infrared intensities have been calculated by density functional theory with a Becke3LYP functional and a 6-31+G* basis set. The calculated infrared spectra match experiment well, confirming the bridge structures for the clusters. The form of the calculated normal modes provides insight into the nature of the bridge fundamentals.

Publication Date


Publication Title

Journal Of Physical Chemistry A


Start Page No.


End Page No.


Included in

Chemistry Commons