This work describes as ynthetica pproachw here an on-planar aromatic heterocyclic [7]helicene is compressedt oy ield ah etero[8]circulene containing an inner antiaromatic cyclooctatetraene (COT) core. This [8]circulene consists of four benzene rings and four heterocyclic rings, and it is the first heterocyclic[ 8]circulenec ontaining three differenth eteroatoms. The synthetic pathway proceeds via at he flattened dehydro-hetero[7]helicene, which is partially ah elicene and partially ac irculene:i ti s non-planar and helically chiral as helicenes, and contains a COT motif like [8]circulenes. The antiaromaticity of the COT core is confirmed by nucleusi ndependent chemical shift (NICS) calculations. The planarizationf rom ah elically p-conjugated[ 7]helicene to af ully planar heterocyclic [8]circulene significantly alterst he spectroscopicp roperties of the molecules.P ost-functionalization of the [7]helicenes and the [8]circulenes by oxygenation of the thiophene rings to the corresponding thiophene-sulfones allows an almost complete fluorescence emission coverage of the visible region of the opticals pectrum (400-700 nm).

The dynamic interplay between two types of chiral structures; fully conjugated racemic hetero[7]helicenes and DNA strands prone to fold into G‐quadruplex structures is described. Both the [7]helicenes and the G‐quadruplex DNA structures exist in more than one conformation in solution. We show that the structures interact with and stabilise each other, mutually amplifying and stabilising certain conformations at increased temperatures. The [7]helicene ligands L1 and L2 stabilise the parallel conformation of k‐ras significantly, whereas hybrid (K+) and antiparallel (Na+) h‐telo G‐quadruplexes are stabilised upon conformational switching into altered G‐quadruplex conformations. Both L1 and L2 induce parallel G‐quadruplexes from hybrid structures (K+) and L1 induces hybrid G‐quadruplexes from antiparallel conformations (Na+). Enantioselective binding of one helicene enantiomer is observed for helicene ligand L2, and VTCD melting experiments are used to estimate the racemisation barrier of the helicene.