Water-mediated conformer optimization in benzo-18-crown-6-ether/water system

Abstract

The conformation of benzo-18-crown-6-ether (B18C6) and its encapsulation of water molecules in a supersonic beam are investigated by laser induced fluorescence (LIF), UV-UV hole-burning, IR-UV double resonance (IR-UV DR), and resonance-enhanced multiphoton ionization (REMPI) spectroscopy with the aid of density functional theory (DFT) calculations at the B3LYP/6-31+G* level. At least four B18C6 conformers and nine B18C6-(H2O)n (n = 1-4) clusters are identified in the supersonic beam. IR-UV DR spectra in the CH stretching region suggest that the four B18C6 conformers have different conformations from each other. In contrast, most of the nine B18C6-(H2O)n clusters have a very similar B18C6 conformation. IR-UV DR spectra in the OH stretching region provide quite clear pictures of the hydration networks formed on B18C6. In all four B18C6-(H2O)1 isomers, the water molecule is H-bonded to the two O atoms adjacent to the benzene ring in "bidentate" and "bifurcated" manners. One of the four B18C6-(H2O)1 isomers exhibits a large population, and further hydration networks are preferentially grown on this specific isomer.

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 ).…”

Vibrational Spectroscopy of Gas Phase Functional Molecules and Their Complexes Cooled in Supersonic Beams

“…As was described above, the flexibility is the key point of crown ethers and they are able to adjust their conformations to fit the size and the shape of the guest species. We show how the structural flexibility affects the dynamics of the encapsulation for two CEs;dibenzo-18-crown-6-ether (DB18C6) and benzo-18-crown-6-ether (B18C6) and their complexes with various neutral molecules ( Kusaka et al, 2007( Kusaka et al, , 2008( Kusaka et al, , 2009 Scheme 4. Dibenzo-18-Crown-6 (DB18C6, left) and Benzo-18-Crown-6(B18C6, right) Figure 14(a) shows the LIF spectrum of DB18C6 cooled in a supersonic jet (Kusaka et al, 2008).…”

“…We investigate how the difference in the flexibility affects its conformation as well as its complexation with water. Upper panel of Figure 19 shows LIF spectra of B16C6 in the band origin region observed without and with adding water vapor, respectively (Kusaka et al, 2009). Bands M1-M4 and A-I are due to bare B18C6 and the B18C6-(H 2 O) n complexes, respectively, because the addition of water vapor reduces the intensities of bands M1-M4 and increases bands A-I.…”

UV photodissociation spectroscopy of cryogenically cooled gas phase host–guest complex ions of crown ethers

“…[18][19][20][21][22][23][24][25][26][27] The cold gas phase complexes are generated either by the supersonic expansion technique for neutral complexes [18][19][20][21][22][23][24] or by the electrospray ionization (ESI)/cold ion-trap method for ionic complexes. [18][19][20][21][22][23][24][25][26][27] The cold gas phase complexes are generated either by the supersonic expansion technique for neutral complexes [18][19][20][21][22][23][24] or by the electrospray ionization (ESI)/cold ion-trap method for ionic complexes.…”

“…[18][19][20][21][22][23][24][25][26][27] The cold gas phase complexes are generated either by the supersonic expansion technique for neutral complexes [18][19][20][21][22][23][24] or by the electrospray ionization (ESI)/cold ion-trap method for ionic complexes. 20,22,23 In the present work, we report a study on host-guest complexes of CEs with protonated aromatic amines. Based on these studies, we reported that the conformations of CEs in the inclusion complexes are generally different from the most stable conformer of bare forms, because CEs will change their structures so that they can include the different size and structure of guest species in their cavities.…”