Foldamer Scaffolds for Electron Transport – FOSET

The project will identify optimal conditions for fast and efficient electron transfer across long distances along the foldamer axis. For this purpose, photo-induced electron transport in individual foldamer helices will be assessed using steady-state and ultrafast time-resolved spectroscopies. The effect of parameters such as foldamer length, the presence of units designed to promote electron hopping vs. superexchange, or the presence of guests that selectively bind a recognition module within the helix will be determined. Methods will be developed to organize highly ordered foldamer arrays in two and three dimensions, and design intermolecular interactions to promote lateral electron transfer between foldamers, i.e. perpendicular to foldamer axes in preparation for electron transfer in bulk materials. Foldamer mediated electron transport in single molecule layer assemblies both along and perpendicular to the foldamer axis will be determined by conductive-AFM and optimized. Conditions under which guest binding to a foldamer monolayer results in a signal that is easily detected and amplified will be determined. The project will involve two partners both located on the University of Bordeaux campus. It builds upon an advanced expertise of Partner 2, led by Dr. Dario Bassani, in assessing electron transport properties in organic materials and upon ground breaking achievements in foldamer design and synthesis by Partner 1, led by Dr. Ivan Huc.

- The synthesis of very long foldamers (up to 96 units) has been optimized to become a routine procedure..
- The first foldamer monolayers have been prepared paving the way to conductivity measurements through and across foldamer monolayers on surfaces.
- Photo-induced electron transfer studies between a donor and acceptor at the two ends of a foldamer showed extremely fast transfer across long distances and very long lived charge separated states. Such phenomena are relevant in photovoltaic devises.
- An original development concerns the control over energy transfer between two chromophores at the ends of a flexible rod by winding of a foldamer helix around the rod. Several rods-like molecules have been produced and energy transfer has been shown to be fast and efficient when the two chromophores can come in near proximity due to the rod flexibility. On the contrary, the addition of a foldamer that winds around the rod imposed a linear extended conformation of the latter that keeps apart the two chromophores thus disfavoring energy transfer. This system allows to monitor conformational dynamics of the rod.

The project intends to mark a step change in the field and innovate by exploiting the robustness and the high level of structural predictability of aromatic amide foldamers to construct novel efficient electron transport materials.

Three manuscripts in preparation

Foldamers are synthetic oligomers that adopt folded conformations inspired by the structures of biopolymers. The FOSET project stems from recent major advances in foldamer research: (i) the stepwise organic synthesis of aromatic amide oligomers that fold into very long (5-10 nm) and conformationally robust helices; (ii) the unanticipated discovery that electrons are transported along these helices at very high rates (ps range) and with low attenuation as a function of length; and (iii) the development of highly selective receptors for organic acids and for monosaccharides from hollow helical molecular containers based on similar aromatic amide backbones. The FOSET project aims at exploring the scope of foldamer mediated electron transport in solution and on solid supports and at exploiting it in the development of novel sensors for challenging and biologically relevant guests such as sugars. It intends to mark a step change in the field and innovate by exploiting the robustness and the high level of structural predictability of aromatic amide foldamers to construct novel efficient electron transport materials. The project will identify optimal conditions for fast and efficient electron transfer across long distances along the foldamer axis. For this purpose, photo-induced electron transport in individual foldamer helices will be assessed using steady-state and ultrafast time-resolved spectroscopies. The effect of parameters such as foldamer length, the presence of units designed to promote electron hopping vs. superexchange, or the presence of guests that selectively bind a recognition module within the helix will be determined. Methods will be developed to organize highly ordered foldamer arrays in two and three dimensions, and design intermolecular interactions to promote lateral electron transfer between foldamers, i.e. perpendicular to foldamer axes in preparation for electron transfer in bulk materials. Foldamer mediated electron transport in single molecule layer assemblies both along and perpendicular to the foldamer axis will be determined by conductive-AFM and optimized. Conditions under which guest binding to a foldamer monolayer results in a signal that is easily detected and amplified will be determined. The project will involve two partners both located on the University of Bordeaux campus. It builds upon an advanced expertise of Partner 2, led by Dr. Dario Bassani, in assessing electron transport properties in organic materials and upon ground breaking achievements in foldamer design and synthesis by Partner 1, led by Dr. Ivan Huc. The FOSET project holds the potential of enabling a paradigm shift in the field of sensor integration for organic electronics. It will benefit from a particularly fertile local economic and scientific context thanks to the recently approved ElorPrintTech Equipex project for printable organic electronics.