Antiaromatic pentalene-based nanohoops and nanobelts (PANEL)

• Applicant: Professorin Dr. Birgit Esser
• Subject Area: Organic Molecular Chemistry - Synthesis and Characterisation
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 434040413

Conjugated nanohoops and -belts have long been of interest to organic chemists, theoreticians, materials engineers and physicists alike because of their cyclic conjugation, the radial orientation of their π-system, their rigid structure, size-dependent physical properties and host-guest chemistry. However, examples of antiaromatic nanohoops are scarce, and no antiaromatic nanobelts have been reported to date. The electronic properties of antiaromatic molecules are markedly different from those of aromatic compounds, manifested in higher HOMO and lower LUMO energies and a potential open-shell biradical character. The objectives of this proposal are to synthesize (1) conjugated nanohoops consisting of heteropentalene panels with strong antiaromatic character and (2) antiaromatic conjugated nanobelts based on pentalene substructures, as well as to investigate the antiaromaticity, electronic and potential open-shell character, structures and strain energies, optoelectronic, and host-guest properties of these novel nanohoops and nanobelts. The group has strong expertise in the synthesis of nanohoops incorporating dibenzopentalene panels, which, however, showed only moderate antiaromaticity. Based on this expertise, preliminary investigations on the synthesis of thienopentalenes as antiaromatic nanohoops panels as well as on the synthesis of macrocyclic precursors to pentalene-based antiaromatic nanobelts, the objectives of this proposal are feasible. The antiaromatic nanohoops and -belts should provide insight into the effect of conjugation on the antiaromaticity of the hoops or belts. Their properties could be exploited in future studies, in particular regarding a potential open-shell biradical character, which has become of increasing interest in recent years, not last for applications in spintronics and quantum computing.

• DFG Programme: Research Grants