123rd General Meeting of the KCS

Type Award Lecture in Division
Area Current Advances in Reaction Dynamics
Room No. Room 305+306
Time THU 15:40-16:10
Code PHYS1-1
Subject Circular dichroism spectroscopy of chiral molecules and ions in the isolated gas phase
Authors Nam Joon Kim
Department of Chemistry, Chungbuk Natioanl University, Korea
Abstract CD spectra measured in solution represent only the average CD values of all conformational isomers. In contrast, the CD spectroscopy of molecules or ions in the isolated gas phase can provide conformation-selective CD values without influence of solvent molecules. We have developed an efficient CD spectroscopic technique that can be used to measure the CD spectra of cold chiral molecules and ions in the gas phase. Using this CD technique, we investigated the induced circular dichroism (ICD) phenomena of jet-cooled chiral complexes. Although CD is generally observed for chiral molecules, achiral molecules can have CD when they are bound with a chiral molecule through noncovalent interactions, which is denoted as ICD. ICD has been extensively employed to investigate the structures and binding properties of various host-guest complexes. We obtained the first isomer-selective ICD spectra of jet-cooled phenol complexes with (–)-methyl L-lactate (PhOH-(–)ML). The ICD values of the two conformers have different signs and magnitudes, which were explained by differences both in the geometrical asymmetries of PhOH bound to (–)ML and in the electronic coupling strengths between PhOH and (–)ML. Comparing the ICD values of various PhOH complexes with other chiral molecules, we identified the physical properties that might govern the differences in their ICD values. Recently, we have also developed a new technique to measure the CD spectra of molecular ions produced by electrospray ionization using cryogenic cold ion spectroscopy. We will discuss the potential application of this technique to larger biomolecular systems.
E-mail namjkim@chungbuk.ac.kr