Project description
Cyclacenes, ring-shaped carbon compounds, synthesised for the first time
Cyclacenes are hoop-like polycyclic compounds where aromatic moieties are fused together to form ring structures. The unique chemical, electronic and structural properties of these ring-shaped carbon compounds render them attractive for use in organic electronics and spintronics. Despite decades of research efforts, it has not yet been possible to produce even a single representative of this substance class. The ERC-funded TACY project will pioneer new synthetic strategies to generate cyclacenes. The proposed approach is highly modular, allowing to structurally vary the belt-type precursors, and thus the cyclacenes, by placing different substituents at the rims. Project research, combined with state-of-the-art computational activities and molecular characterisation techniques, will provide unprecedented insight into the structure-property relationship of the conjugated zigzag topology in cyclacenes.
Objective
Cyclacenes, i.e. cyclic versions of acenes consisting of linearly fused benzene rings, were first discussed in 1954 by Heilbronner, but - despite considerable synthetic efforts over decades - have remained an elusive class of compounds. Theoretical investigations suggest that cyclacenes are highly reactive due to pronounced polyradical character and significant ring strain. All prior attempts to synthesise cyclacenes failed, mainly because the final synthetic step of establishing a fully conjugated π-system was energetically prohibitive. Despite these challenges, cyclacenes remain intriguing synthetic targets because of their unique chemical, electronic, and structural properties as well as their potential applications in organic (opto-)electronics or spintronics. In this collaborative project, we will develop novel synthetic approaches, which synergistically combine efficient and high-yielding synthetic strategies of belt-type precursors that we will transform to cyclacenes by extrusion of suitable leaving groups under cryogenic matrix isolation conditions, on surfaces, in the solid state, and ultimately even in solution. Our synthetic approach is highly modular and allows to structurally vary the belt-type precursors, and thus the cyclacenes, by placing different substituents at the rims, including peri-annulation or isosteric substitution of CH units by heteroatoms. This research, combined with state-of-the-art computational investigations and characterization even on the single-molecule level, will provide unprecedented insight into the structure-property relationship of the fully conjugated zigzag topology present in cyclacenes and address fundamental questions of chemical reactivity and the interplay of aromaticity, strain and polyradical character. This knowledge will finally allow us to synthesise interlocked structures based on cyclacenes and to apply cyclacenes in controlled reactions on surfaces for creating further elusive materials such as polyacenes.
Fields of science
Programme(s)
- HORIZON.1.1 - European Research Council (ERC) Main Programme
Topic(s)
Funding Scheme
ERC-SYG - ERC-SYGHost institution
69117 Heidelberg
Germany