Structure of hydrated clusters of dibenzo-18-crown-6-ether in a supersonic jet—encapsulation of water molecules in the crown cavity

Abstract

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-(H(2)O)(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-(H(2)O)(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-(H(2)O)(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-(H(2)O)(1) cluster.

Infrared spectroscopy of gas-phase hydrated K+:18-crown-6 complexes: Evidence for high energy conformer trapping using the argon tagging method

“…The minimum energy structure of neutral (18c6)H 2 O, shown in Fig. 1 [19,20], where H 2 O was also bound to the 18c6 moiety via a bidentate hydrogen bond, the symmetric and asymmetric splitting was found to be ∼68-83 cm −1 .…”

Binding selectivity of dibenzo-18-crown-6 for alkali metal cations in aqueous solution: A density functional theory study using a continuum solvation model

“…The geometries of those initial conformers were fully optimized by a series of theoretical calculations at the HF/3-21 G, HF/6-31 G, B3LYP/6-31 G, and then B3LYP/6-31 + G(d) levels. The optimization at the B3LYP/6-31 + G(d) level has been successfully employed to predict the lowest energy structures of DB18C6(H 2 O) n (n = 0-4) [43], B18C6(H 2 O) n (n = 0-1) [29], M + -DB18C6 [7], and M + -18C6(H 2 O) n (M = Li, Na, K, Rb, and Cs, n = 0-4) [10,32,33]. The local minimum structures in aqueous solution were obtained by re-optimizing those optimized structures at the B3LYP/6-31 + G(d) level using the CPCM model and UAKS radii.…”

Binding water to a PEG-linked flexible bichromophore: IR spectra of diphenoxyethane-(H2O)n clusters, n = 2-4

“…24,39,40,42,[44][45][46][47][48][49] The highest frequency transition at 3715 cm −1 is readily assignable to a free OH-stretch fundamental. The transitions at 3683 and 3550 cm −1 are similar to those observed in the DPOE-H 2 O spectrum 24 (Figure 1(b) and dotted lines in Figure 6(a)), consistent with a similar primary binding site to DPOE in which one water acts as a double donor bridge between an ether O-atom on one ring and the π cloud on the other (OH · · · π at 3683 cm −1 and OH · · · O at 3550 cm −1 ).…”