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Synthesis of a Double Helicene by a Palladium‐Catalyzed Cross‐Coupling Reaction: Structure and Physical Properties
Author(s) -
Kashihara Hitoshi,
Asada Toshio,
Kamikawa Ken
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201500074
Subject(s) - helicene , homo/lumo , racemization , palladium , chemistry , cyclic voltammetry , crystallography , catalysis , electrochemistry , photochemistry , molecule , stereochemistry , organic chemistry , electrode
For this study, twisted π‐extended helicene 1 and double helicene 2 with a helicene framework were synthesized through palladium‐catalyzed CH arylation or Suzuki–Miyaura coupling reaction. X‐ray crystallography revealed grossly twisted structures that were soluble in various conventional organic solvents. Optical properties based on UV/Vis and fluorescence spectra were measured. Electrochemical properties were also studied by measurements of cyclic voltammetry in 1 and 2 , which revealed their HOMO and the LUMO energies. Theoretical calculation supports their HOMO and LUMO energies and molecular orbitals. Furthermore, a racemization process of 2 predicted that the activation free energy at 300 K would be 31.8 kcal mol −1 by DFT calculation, which indicated the static helicity at 300 K.