|演 題||「Putting Molecular Clusters to Work in Analytical Chemistry: Quantitative Chiral Analysis using the Chiral Tag Method」|
|日 時||2023年12月11日(月) 16:00|
|講演者||Prof. Brooks H. Pate（University of Virginia)|
Determining the structures of weakly bound molecular clusters remains a significant challenge in physical chemistry. These clusters are typically produced in pulsed jet expansions as a mixture of cluster sizes and isomers. The analysis of this complex mixture requires a spectroscopy method that offers high spectral resolution, to reduce spectral overlap issues, and high sensitivity to molecular structure so that confident structure assignments can be made for the species present. Beyond these experimental challenges, there is a need for theoretical methods that can identify the cluster isomers on a complex potential energy surface and accurately calculate their physical and spectroscopic properties to aid analysis of the experiments. Broadband molecular rotational spectroscopy has emerged as an exceptionally powerful experimental tool for the study of molecular clusters. New analysis strategies that exploit the intensity stability of chirped-pulse Fourier transform microwave spectrometers will be presented. For example, in the study of water clusters, an isotope dilution method can be used to assign the cluster size to each transition observed in the spectrum making it easier to analyze the full rotational spectrum. This approach has been used to extend the identification of water clusters up to N=16. The special challenges of structure determination of molecular clusters formed between chiral molecules will be a focus of this presentation. The process of chiral recognition in the pulsed jet expansion is of particular interest. The nature of cluster formation is important to applications of cluster spectroscopy to quantitative chiral analysis using the chiral tag method. Results from several studies show that chiral tag rotational spectroscopy provides accurate measurements of the enantiomeric excess (EE) from racemic to enantiopure samples. The nature of cluster formation means that it is possible to measure the EE without any need for performing spectroscopic analysis. This feature makes chiral tag rotational spectroscopy a powerful alternative to chiral chromatography in analytical chemistry. Applications of this chiral analysis technique to problems in pharmaceutical chemistry will be presented.
倉持 光、瀬川 泰知（2023年度コロキウム委員）