CHEXTAN · Chiral expression and transfer at the nanoscale

Final Activity Report Summary - CHEXTAN (Chiral expression and transfer at the nanoscale)

The CHEXTAN Marie Curie Research Training Network carried out work which created chiral nanostructures using chemical and physical phenomena by exploiting an understanding of the interactions between molecules themselves and between molecules and surfaces, and explored the influence of chirality on the resulting nanostructures. The results showed how transfer of chirality can be understood, how it can be observed at the nanoscale, and its possible implications in useful materials systems. New chiral molecular systems were designed and prepared. Organic molecules were the source of chirality in the systems studied, and state-of-the-art diastereoselective synthesis was used for their generation. Chiral compounds with functional aromatics (porphyrins and phthalocyanines), radicals, thiols, amphiphiles and amino acid derivatives were prepared by the contracted researchers, providing them with expertise in the preparation and characterisation (with spectroscopic techniques, including circular dichroism) of the chiral compounds. In particular, molecular modelling and solid state crystallographic investigations yielded important information concerning the conformation of the molecules and their dynamic possibilities. The molecules prepared were adsorbed onto surfaces to form isolated species, monolayers and multilayers, and the chirality was tracked during the process of formation of the monolayers. Ultrahigh vacuum deposition and characterisation of molecules and their layers on metals was performed in order to understand the fundamental factors that control chiral expression at surfaces. Model chiral surfaces were be created by the organic vapour deposition of chiral molecules onto well-defined metal surfaces in ultra-clean vacuum conditions. In depth characterisation of the chiral motif and the ordering was carried out using sophisticated surface sensitive spectroscopies to yield a nanoscale description of the system. Theory was also used to help the interpretation of the experimental results. The Langmuir trough is another extremely useful tool for organising chiral molecules and investigating the interactions between them, and the Brewster angle microscope a tremendous aid in studying the mono- and multilayers that exist. The method was taught to researchers from complementary groups in order to ascertain the similarities and differences in using this organisation tool and the other ones used in the other groups in the network. Self-assembled monolayers provide a convenient and well tested structural starting point for much of the work carried out under non-UHV conditions. The formation of monolayers at the graphite-liquid interface were explored using STM, and the effects of position and number of stereogenic centres was explored. Functionalisation of the technologically relevant surface SiOx/Si was explored as a support for templated and directional chiral organisation. Deposition assisted by stamps using soft lithographic techniques was achieved. New ways of transferring chirality were uncovered, which are useful for materials systems. A new surface-based reaction leading to chiral covalent nanostructures was revealed, which has subsequently led to the investigation of surface polymerizations in many other research groups. This result is important for the development of chiral catalysts at surfaces. The lithography of DNA on surfaces was developed, a feat which has far-reaching possibilities in composite chiral systems for different applications. The group of trained researchers coming from the network have a unique inter- and multidisciplinary view of chirality in all kinds of materials. Much of the research carried out in the network can be found summarised in the book 'Chirality at the nanoscale' published by Wiley-VCH, as well as in a special issue of Chemical Society Reviews on Nanoscale Chirality published in March 2009. In both of these volumes, researchers from the CHEXTAN network contributed importantly.

Data: CORDIS, © European Union