Date and Time: Friday, 10th August, 2018, from 15:00 to 16:30
Place: IMRAM East Building 1, 3rd Floor Meeting Room #307, Katahira Campus, Tohoku University

Lecturer: Prof. Reiko ODA(Research Director, CNRS-CBMN / University of Bordeaux, France)
Title: Kinetic evolution of Chiral nanometric molecular assemblies: Molecular chirality to supramolecular chirality

Outline：
A vast number of examples of chiral nanostructures exist in nature such as nucleic acids, proteins or protein assemblies, inspiring chemists to design synthetic macromolecules with well-defined architectures and functions. The crystallography and modelling approaches are strong allies for logical design of such structures based on intra-inter molecular interaction. Meanwhile, it is much more difficult to predict and design the chiral structure formation based on molecular assemblies, usually more than 10 times larger than molecular helices, of the order of a few tens of nanometer in their pitches, due to the difficulty to obtain the molecular information at atomic scale for these structures. Not only because of the difficulty to crystalize these molecules while keeping the information of chiral packing but also the complex combination of cooperative weak interactions make it difficult to predict their assembling mechanisms. It is also sometimes shown that these objects evolves with time with a very slow time constant (needs days to reach equilibrium). We have previously shown that non-chiral di-cationic surfactant self-assemble to multi-bilayers to form helices in the presence of dianions, tartrate. Depending on the enantiomeric excess (ee) of the tartrate, the pitches vary from small (~60 nm) for ee = 1 to micrometers for ee = ~0.3 then to infinite (no helicity) for ee = 0.1,2 In this study, we follow the formation of these nanohelices of various sizes using the ensemble of techniques, CD, VCD, XRD, FT-IR, and cryo TEM. We have shown that the large twisted ribbons with micrometric pitches grow from the merging of smaller helices with nanometric pitches while the molecular organization increases with time, therefore leading to the increase in VCD, and the decrease in CD along with the pitch increase. The ensemble of data shed light on understanding how these helical molecular assemblies are formed resulting in the chirality enhancement.