title: An organometallic route to long helicenes.
abstract: Along with the recent progress in the development of advanced synthetic methods, the chemical community has witnessed an increasing interest in promising carbon-rich materials. Among them, helicenes are unique 3D aromatic systems that are inherently chiral and attractive for asymmetric catalysis, chiral recognition and material science. However, there have been only limited attempts at synthesizing long helicenes, which represent challenging targets. Here, we report on an organometallic approach to the derivatives of undecacyclic helicene, which is based on intramolecular [2 + 2 + 2] cycloisomerization of aromatic hexaynes under metal catalysis closing 6 new cycles of a helicene backbone in a single operation. The preparation of nonracemic compounds relied on racemate resolution or diastereoselective synthesis supported by quantum chemical (density functional theory) calculations. The fully aromatic [11]helicene was studied in detail including the measurement and theoretical calculation of its racemization barrier and its organization on the InSb (001) surface by STM. This research provides a strategy for the synthesis of long helical aromatics that inherently comprise 2 possible channels for charge transport: Along a pi-conjugated pathway and across an intramolecularly pi-pi stacked aromatic scaffold.
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of Czech Republic, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic.
authors.forename: Petr
authors.initials: P
authors.lastname: Sehnal
authors.forename: Irena G
authors.initials: IG
authors.lastname: Stará
authors.forename: David
authors.initials: D
authors.lastname: Saman
authors.forename: Milos
authors.initials: M
authors.lastname: Tichy
authors.forename: Jirí
authors.initials: J
authors.lastname: Mísek
authors.forename: Josef
authors.initials: J
authors.lastname: Cvacka
authors.forename: Lubomír
authors.initials: L
authors.lastname: Rulísek
authors.forename: Jana
authors.initials: J
authors.lastname: Chocholousová
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Vacek
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Goryl
authors.forename: Marek
authors.initials: M
authors.lastname: Szymonski
authors.forename: Ivana
authors.initials: I
authors.lastname: Císarová
authors.forename: Ivo
authors.initials: I
authors.lastname: Stary
mesh_terms: D016252:Microscopy, Scanning Tunneling; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry*; D011083:Polycyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism; D013816:Thermodynamics
chemical_list: D009942:Organometallic Compounds; D011083:Polycyclic Compounds; C031660:helicenes