2019年度 物質生命理工学科コロキウム

Host-guest Complexes of Chiral & Achiral Metalloporphyrin Dimers: Stereochemical Structure & Application by MD, ECD, 1H-NMR
Prof. Nina Berova

日時/場所	2019年 4月　22日（月）　13:30-15:00 L-821

詳細

講師にProf. Nina Berova (Columbia University) をお招きして、以下の内容でご講演いただきます。皆様お誘い合わせのうえご参加ください。
＊申込不要・参加無料・学生、学外の方の聴講歓迎

Host-guest Complexes of Chiral & Achiral Metalloporphyrin Dimers: Stereochemical Structure & Application by MD, ECD, 1H-NMR
Prof. Nina Berova (Columbia University)

Metalloporphyrin dimers continue to attract a great attention due to growing interest for development of more versatile chiroptical sensors at supramolecular level. In most cases two metalloporphyrin macrocycles (Zn(II)P) are attached to achiral linker, thus forming an achiral tweezer receptor. If their coordination to chiral bidentate substrate proceeds as the stereodifferentiating process two porphyrins adopt a chiral mutual disposition and are able to interact through the space. In response to this situation it may appear an exciton split electronic CD (couplet), usually very intense and observable on a submicroscale level. Such ECD profile possesses a great diagnostic power regarding the absolute configuration of chiral natural products, drugs and other synthetic substrates. However, sometimes the metal coordination results to a mixture of chiral host-guest complexes of great conformational diversity. In such case a theoretical conformational analysis and ECD simulations are desirable in order to rationalize the experimental results. More recent studies also on chiral tweezers hosts and achiral guests revealed that the conformational analysis in these cases might be more challenging task than expected, since even subtle spatial changes either in the guest molecule or in chiral host, or in both, may profoundly affect the ECD response. It is not surprising therefore, that the versatile porphyrin-based receptors continue to stimulate more studies towards chiral sensing and development of new stereodynamic probes.
In the lecture we will also discuss an intriguing chiral switch, namely a two-step helicity inversion upon complexation between a chiral tweezer host, the Zn(II)bisporphyrin derivative of (1R, 2R)- diphenylethylenediamine, and achiral aliphatic diamines of different length and stoichiometry. We will present as well some unpublished results. They are based on Molecular Dynamics (MD) simulations, ab initio geometry optimization and theoretical calculations of electronic CD (ECD) by TD-DFT along with 1H-NMR experimental analysis and interpretation in the light of porphyrin ring-current effect phenomenon.

本件に関するお問い合わせは、コロキウム委員（東、内田）までお願いいたします。

ポスター