Matrix isolation vibrational circular dichroism spectroscopic studies of chiral molecules and solvent effects.

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Nearly all important biological molecules are chiral. In fact, the chemistry of life is built almost exclusively on left-handed amino acids and right-handed sugars, a pattern known as the 'homochirality of life'. Pharmaceuticals are often chiral since in many cases only drugs with the correct handedness are capable of executing a proper 'hand shake' at the receptor site. Our research focuses on understanding the phenomena of chirality and chiral recognition using experimental spectroscopic and ab initio methods.     Presently, we are pursuing two distinct yet inter-linked research programs. One centers on the gas phase high resolution spectroscopy of chiral molecular clusters and the other one focuses on condensed phase studies using vibrational circular dichrosim (VCD) spectroscopy. VCD spectroscopy has emerged in recent years as a viable tool for the determination of absolute and conformational structures of chiral molecules. VCD studies of conformationally flexible chiral molecules, however, experience severe limitations since their VCD spectra tend to be broad and with few features because of conformational distributions and solute-solvent interactions. We propose to implement a matrix isolation assembly into the VCD spectrometer to significantly enhance the sensitivity of VCD spectroscopy for the investigations of multiconformational chiral molecules. We further propose to use matrix isolation technique to prepare small solute-solvent clusters for VCD spectroscopic studies in order to probe solute-solvent intermolecular interactions in a step wise manner. In particular, we will study how chirality, i.e.VCD signal strength, is transferred to an achiral solvent, such as water, through intermolecular interactions with a chiral molecule.      The results will be of significant interest to a large group of chemists who practice synthetic organic chemistry, bioanalytical chemistry, and environmental chemistry. A delay in obtaining this important instrument would be a severe setback for us to pursue our innovative idea and will hamper our efforts to lead and to contribute significantly to this exciting new field.