Rotational spectrum and structure of Ne-C₆H₆-H₂O, an aromatic sandwich

Abstract

Low J(J=1→5) rotational spectra of seven isotopomers of Ne-C₆H₆-H₂O trimer have been observed with a Balle/Flygare Fourier transform microwave spectrometer. The trimer is found to be a symmetric top with a B₀, D_J, and D_JK in the parent of 959.3504(1) MHz, 2.425(2) kHz, and 13.385(5) kHz. The benzene is sandwiched between Ne and H₂O, both of which lie on the C₆ axis of benzene. Substitution analysis gives the neon and oxygen distances from the trimer center of mass (c.m.) to be 3.324 and 3.454 Å, respectively. The Ne to c.m. (C₆H₆) and c.m. (C₆H₆) to c.m. (H₂O) distances thereby determined are 3.391 and 3.334 Å, respectively. Those in the corresponding dimers are 3.458 and 3.329 Å, giving a decrease in the trimer of 0.067 Å in the Ne to c.m. (C₆H₆) distance and an increase of 0.005 Å in c.m. (C₆H₆) to c.m. (H₂O). Otherwise the state of the water in the dimer does not appear to be materially affected by addition of the Ne.