Dynamics of CHFClBr and CDFClBr Inside a Thiomethylated Cryptophane, Studied by 19F−H CSA-DD Cross-Correlated Relaxation and 2H Quadrupolar Relaxation Measurements

Chiral recognition by fullerenes: CHFClBr enantiomers in the C82cage

Theoretical studies of complexes of the enantiomers of CHFClBr with C₈₂-3 show that the too large guests are stabilized in the C₈₂cage by electrostatic interactions. The sign of v(CH) stretching vibration of S-CHFClBr@C₈₂-3 in the VCD spectrum is reversed as compared to that of the free guest. Spectra of the complexes exhibit differences.

Synthesis of enantiopure, trisubstituted cryptophane-A derivatives

The efficient synthesis of enantiopure, trisubstituted cryptophane-A derivatives, organic host molecules with unusually high xenon affinity, is reported. Synthesis and chromatographic separation of (±) tri-Mosher's acid substituted cryptophane diastereomers gave ready access to the enantiopure cryptophanes, which are critical components in the design of enantiomerically pure (129)Xe biosensors. Hyperpolarized (129)Xe NMR spectroscopy identified single resonances for both trisubstituted cryptophane diastereomers that were separated by 9.5 ppm. This highlights opportunities for using enantiopure xenon biosensors in the simultaneous detection of (129)Xe in different biochemical environments.

Progress toward the first observation of parity violation in chiral molecules by high-resolution laser spectroscopy

Parity violation (PV) effects in chiral molecules have so far never been experimentally observed. To take up this challenge, a consortium of physicists, chemists, theoreticians, and spectroscopists has been established and aims at measuring PV energy differences between two enantiomers by using high-resolution laser spectroscopy. In this article, we present our common strategy to reach this goal, the progress accomplished in the diverse areas, and point out directions for future PV observations. The work of André Collet on bromochlorofluoromethane (1) enantiomers, their synthesis, and their chiral recognition by cryptophanes made feasible the first generation of experiments presented in this article.

Vibrational analyses for CHFClBr and CDFClBr based on high levelab initiocalculations

Anharmonicity corrections to the harmonic vibrational spectra of CHFClBr and its deuterated isotopomer were computed by means of variational and perturbational approaches. A comparison of both methods is provided. Based on CCSD(T)/aug-cc-pVTZ electronic structure calculations excellent agreement with experimental data was obtained. Absolute mean deviations are in the range of about 4 cm(-1) for the fundamental modes, while slightly larger values of about 7 cm(-1) were found for the first vibrational overtones. In addition, vibrationally averaged structural parameters are provided for both molecules. The calculations will serve as a future starting point for parity-violation effects in vibrational transitions in these chiral molecules.

Chlorofluoroiodomethane as a potential candidate for parity violation measurements

CHFClI is among the more favorable molecules for parity violation (PV) measurements in molecules. Despite the fact that calculated PV effects are two orders of magnitude smaller than in some organometallic compounds, CHFClI displays interesting features which could make possible a new experimental PV test on this molecule. Indeed, ultrahigh resolution spectroscopy using an ultrastable CO(2) laser is favored by several intrinsic properties of this molecule. For example, the high vapor pressure of CHFClI allows investigation by supersonic beam spectroscopy. Indeed, the spectroscopic constants have been accurately determined by microwave and millimetre wave spectroscopy. This is important for the subsequent selection of an appropriate absorption band of CHFClI that could be brought to coïncide with the absorption of CO(2). Partially resolved (+)- and (-)-CHFClI enantiomers with respectively 63.3 and 20.5% ee's have been recently prepared and analyzed by molecular recognition using chiral hosts called cryptophanes. Finally, the S-(+)/R-(-) absolute configuration was ascertained by vibrational circular dichroïsm (VCD) in the gas phase.

Diagrammatic Formulation of the Kinetic Theory of Fluctuations in Equilibrium Classical Fluids. V. The Short Time Approximation for the Memory Function

The correlation function for density fluctuations in a monatomic fluid obeys a formally exact kinetic equation containing a memory function. A previously derived short time approximation (STA) for this memory function is tested by comparing its predictions with the results of molecular dynamic simulations of a dense Lennard-Jones fluid at a variety of temperatures. This approximation takes into account the contribution to the correlation function of uncorrelated repulsive binary collisions. The qualitative changes of predicted correlation functions with temperature and wave vector are generally correct. The major exception to this is the transverse current correlation function for small wave vector. The quantitative accuracy is better at short times than long times and better at high temperatures than low temperatures. The major failing of the STA is its underestimation of the amplitudes of the negative dips in the current autocorrelation functions and of the temperature dependence of the amplitudes of the dips. Despite its deficiencies in predicting the time dependence of current correlation functions, the STA gives accurate results for the self-diffusion coefficient and the shear viscosity coefficient at the highest temperatures studied.

Chiral Trialkanolamine-Based Hemicryptophanes: Synthesis and Oxovanadium Complex

[reaction: see text] A novel class of chiral hemicryptophane hosts has been synthesized in diastereoisomerically pure form, namely, M-(R,R,R)-1a/P-(S,S,S)-1a and M-(S,S,S)-1b/P-(R,R,R)-1b. The C3-symmetrical precursor 9 was prepared, using either (R)- or (S)-glycidyl nosylate, repectively, as the chiral pool reactant and subsequently cyclized (trimerized) in the presence of Sc(OTf)3. The four stereoisomers were fully characterized and displayed two pairs of mirror-image CD spectra, which were used to determine their absolute configuration. The formation of the oxovanadium(V) complex of hemicryptophane 1a is also reported.