Articles you may be interested inStructure and tunneling dynamics in a model system of peptide co-solvents: Rotational spectroscopy of the 2,2,2trifluoroethanolwater complex A comparison of the properties of 2,2,2-trifluoroethanol and 2,2,2-trifluoroethanol/water mixtures using different force fieldsThe microwave spectra of CF 3 CH 2 OH and CF 3 CH 2 OD have been investigated from 5 to 26 GHz with a pulsed-nozzle Fourier-transform microwave spectrometer and from 26 to 42 GHz with an electric resonance optothermal spectrometer. Tunneling of the OH proton between the two isoenergetic gauche conformations splits the observed transitions into two tunneling components. An effective rotation-tunneling Hamiltonian is used to fit the a-and b-type pure rotational and c-type torsional-rotational transitions for both isotopomers to better than 5 and 13 kHz for the OH and OD forms, respectively. The tunneling splittings determined from the fits for the OH and OD isotopomers are 5868.6952͑16͒ and 208.5037͑42͒ MHz, respectively. A structural analysis using the moments of inertia of the OH and OD isotopomers determines that the hydroxyl hydrogen is directed toward the fluorine with a F•••H separation of 2.561͑1͒ Å and a dihedral angle of ͑CCOH͒ϭ68.97͑6͒°. The observed tunneling splittings are fit to a double-minimum potential, giving gauche-gauche tunneling barriers of 763 and 720 cm Ϫ1 and OH torsional fundamental frequencies of 364 and 271 cm Ϫ1 for CF 3 CH 2 OH and CF 3 CH 2 OD, respectively. The uncertainties shown in parentheses throughout the paper are one standard deviation.

The J = 1 t 0 rotational transitions of the four isotopomers H314N11BF3, H314N10BF3, H315N11BF3 and H315NloBF3 of the archetypal donor-acceptor complex formed between ammonia and boron trifluoride have been detected with a pulsed-nozzle, Fourier-transform microwave spectrometer; by using a fast-mixing nozzle, H3NBF3 has been isolated in collisionless expansion before condensation can occur, thereby allowing the first detection of this elusive species in the gas phase.

The weakly bound dimer H3P...Cl2 has been isolated in a pulsed jet by keeping the highly reactive components H3P and Cl2 separate until the point at which they expand into the evacuated Fabry–Pérot cavity of a pulsed-nozzle Fourier-transform microwave spectrometer. The rotational spectra of the three symmetric-top isotopomers H3P...35Cl 35Cl, H3P...35Cl 37Cl, and H3P...37Cl 35Cl detected in this way have been analyzed to give the ground-state spectroscopic constants B0, DJ, DJK, χ1(Cl), and χ2(Cl). Comparison of the dimer properties determined from the spectroscopic constants of H3P...Cl2 with those of the hydrogen-bonded dimer H3P...HCl indicates that charge transfer is not predominant in the interaction of PH3 and Cl2. Some parallels in the properties of B...Cl2 and B...HCl are discussed for B=PH3 and HF.

The 110←111 transition of H2D+ was detected in a dc discharge in Ar–H2–D2 mixtures with liquid nitrogen cooling and an applied axial magnetic field. The transition frequency was determined to be 372 421.380±0.100 MHz. This transition is expected to be the most favorable one for radioastronomical detection of this very crucial ion in the interstellar medium.

The rotational spectra of six isotopomers of trimethylamine-alane have been observed by pulsed beam Fourier transform microwave spectroscopy. Hyperfine analyses of the symmetric top isotopomers, (CH&NAlH3, (CH3)3NAlD3, and (CH3)3l5NA1H3, determined the spectroscopic constants, BO, DJ, DJK, eQq(27A1), and eQq(14N). For (CH3)3NAlH3, BO = 2745.113(1) MHz, DJ = 643(24) Hz, DJK = 1372(250) Hz, eQq(27A1) = 25.032(6) MHz, and eQq(14N) = -3.777(5) MHz. Spectral assignments have also been made for the asymmetric top isotopomers, [(CH3)2l3CH3]NAlH3, (CH3)3NAlH2D, and (CH3)3NAlHD2. Substitution structural parameters of rNc = 1.487(2) and 6°C = 109.9(2)' are obtained from the microwave moments of inertia. With the assumption of rAlN = 2.063(7) A from an electron diffraction structure reported previously (Almenningen, A.; Gundersen, G.; Haugen, T.; Haaland, A. Acta Chem. Scand. 1972, 26, 3928) microwave substitution coordinates for the aluminum hydrogens give THAI = 1.585(2) A and OHAN = 98.1(6)'. The structure of (CH&NAlH3 is compared to the related complexes, H3A1NH3, H3NBH3, and (CH&NBH3. In the same series, bond orders calculated from measured values of eQq(27A1) and eQq("B) are compared to A1-N and B-N dative bond dissociation energies.