Exploring chirality and chiral recognition on the molecular level using spectroscopic and ab initio methods

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An object is chiral if its mirror image can not be superimposed on itself. Our right and left hands are the most familiar chiral objects we encounter in daily life. A chiral object interacts differently with another chiral entity, just in the same sense as a right hand can execute a proper hand shake with another right hand but not with a left hand. Nearly all important biological molecules are chiral. Chirality and chiral recognition are essential for living systems and are of fundamental importance in the life sciences.     The research in my group focuses on understanding the phenomena of chirality and chiral recognition on the molecular level using experimental infrared spectroscopic and ab initio methods. In the first two year granting period, we have successfully designed and constructed two highly sophisticated spectroscopic instruments for the high resolution infrared spectroscopic characterization of chiral recognition. One of them is a mid-infrared cavity ring down spectrometer in combination with a pulse slit jet expansion. The other is a mid-infrared rapid scan spectrometer coupled with a home made astigmatic mirror multipass cell. This provides fast real time scanning of a wide spectral range and complements the capability of our cavity ring down spectrometer. The high resolution infrared laser spectra of chiral clusters measured with the two instruments provide detailed and quantitative information about the structural and dynamical information of the chiral molecular complexes. In combination with our ab initio calculations, we learn about the roles that the hydrogen bonds and dispersion interactions play in chiral recognition. Our work may eventually lead to the formulation of new molecular models for chiral discrimination.     Complementary to our chiral recognition research, we have started to work on the absolute structural determinations of chiral molecules using Fourier transform vibrational circular dichroism spectroscopy and ab initio modeling. The goal is to explore the link between molecular structure and optical activity, and ultimately to develop a fingerprinting method for the identification of chiral molecules with a particular handedness.