Structure of hydrated clusters of dibenzo-18-crown-6-ether in a supersonic jet : Encapsulation of water molecules in the crown cavity
The structure of dibenzo-18-crown-6-ether (DB18C6) and its hydrated clusters has been investigated in a supersonic jet. Two conformers of bare DB18C6 and six hydrated clusters (DB18C6–(H2O)n) were identified by laser induced fluorescence, fluorescence detected UV–UV hole-burning and IR–UV double-resonance spectroscopy. The IR–UV double resonance spectra were compared with the IR spectra obtained by quantum chemical calculations at the B3LYP/6-31+G* level. The two conformers of bare DB18C6 are assigned to “boat” and “chair I” forms, respectively, among which the boat form is dominant. All the six DB18C6–(H2O)n clusters with n = 1–4 have a boat conformation in the DB18C6 part. The water molecules form a variety of hydration networks in the boat-DB18C6 cavity. In DB18C6-(H2O)1, a water molecule forms the bidentate hydrogen bond with the O atoms adjacent to the benzene rings. In this cluster, the water molecule is preferentially hydrogen bonded from the bottom of boat-DB18C6. In the larger clusters, the hydration networks are developed on the basis of the DB18C6- (H2O)1 cluster.
Physical Chemistry Chemical Physics
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Royal Society of Chemistry
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Graduate School of Science