title: Benzo-Fused Double [7]Carbohelicene: Synthesis, Structures, and Physicochemical Properties.
abstract: A benzo-fused double [7]carbohelicene (D7H) was synthesized through a regioselective cyclodehydrogenation of a tetranaphthyl-p-terphenyl-based precursor. The twisted (D7H-1) and anti-folded (D7H-2) conformers of D7H were separated by recrystallization, and their double helicene structures with overlapping terminal benzene rings were unambiguously elucidated by X-ray crystallography. A record-high isomerization barrier (46.0 kcal mol-1) in double helicenes was estimated based on density functional theory (DFT) calculation, which resulted in the excellent conformational stability of D7H. The physicochemical properties of D7H-1 and D7H-2 were investigated by UV/Vis absorption spectroscopy and cyclic voltammetry, displaying the variation of electronic structure upon conformational changes. The optical resolution of the racemic D7H-1 was carried out by chiral HPLC, offering enantiopure D7H-1-(P,P) and D7H-1-(M,M), which were further characterized by circular dichroism spectroscopy.
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany.
authors.forename: Yunbin
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany.
authors.forename: Xiao-Ye
authors.initials: XY
authors.lastname: Wang
authors.affiliation: Department of Chemistry and Chemical Engineering, Xiamen University, 361005, Xiamen, China.
authors.forename: Pi-Xian
authors.initials: PX
authors.lastname: Peng
authors.affiliation: Department of Chemistry and Chemical Engineering, Xiamen University, 361005, Xiamen, China.
authors.forename: Xin-Chang
authors.initials: XC
authors.lastname: Wang
authors.affiliation: Department of Chemistry and Chemical Engineering, Xiamen University, 361005, Xiamen, China.
authors.forename: Xiao-Yu
authors.initials: XY
authors.lastname: Cao
authors.affiliation: Center for Advancing Electronics Dresden (CFAED), Department of Chemistry and Food Chemistry, Technische Universität Dresden, 01062, Dresden, Germany.
authors.forename: Xinliang
authors.initials: X
authors.lastname: Feng
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Müllen
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany.
authors.forename: Akimitsu
authors.initials: A
authors.lastname: Narita
keywords: carbohelicenes; cyclodehydrogenation; double helicenes; isomerization barrier; optical resolution