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Ultralong Carbon–Carbon Bonds in Dispirobis(10‐methylacridan) Derivatives with an Acenaphthene, Pyracene, or Dihydropyracylene Skeleton
Author(s) -
Kawai Hidetoshi,
Takeda Takashi,
Fujiwara Kenshu,
Wakeshima Makoto,
Hinatsu Yukio,
Suzuki Takanori
Publication year - 2008
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.200702028
Subject(s) - covalent bond , single bond , molecule , bond length , dication , steric effects , crystallography , molecular geometry , chemistry , aryl , materials science , alkyl , stereochemistry , organic chemistry
Acenapthalene, pyracene, and dihydropyracylene attached to two units of spiroacridan are a novel class of hexaphenylethane (HPE) derivatives that have an ultralong C sp 3C sp 3bond (1.77–1.70 Å). These sterically challenged molecules were cleanly prepared by CC bond formation through two‐electron reduction from the less‐hindered dications. These ultralong bonds were realized based on several molecular‐design concepts including enhanced “front strain” through “multiclamping” by means of fusing or bridging aryl groups in the HPE molecule. The lengths of these ultralong bonds and their relation to the conformation (torsional angle) were also validated by means of theoretical calculations. Bond‐fission experiments revealed that the bonds are more easily cleaved than standard covalent bonds to produce the corresponding dication upon oxidation with an increase in the length of the CC bond.