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Structural Changes on Twofold Oxidation of Tetrakis(dimethylamino)‐ p ‐benzoquinone: A Sterically Overcrowded Electron‐Rich “Chair” Compound Turns into a “Twist” Dicyanine Salt
Author(s) -
Bock Hans,
Rupper Klaus,
Näther Christian,
Havlas Zdenek
Publication year - 1991
Publication title -
angewandte chemie international edition in english
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 0570-0833
DOI - 10.1002/anie.199111801
Subject(s) - dihedral angle , steric effects , chemistry , dication , bent molecular geometry , quinone , twist , benzoquinone , crystallography , cyanine , molecule , salt (chemistry) , stereochemistry , photochemistry , hydrogen bond , organic chemistry , quantum mechanics , fluorescence , physics , geometry , mathematics
On account of the four bulky (H 3 C) 2 N‐substituents the tetrakis (dimethylamino)‐ p ‐benzoquinone molecule is electron‐rich and sterically overcrowded. It has a chair conformation in which the OC groups are bent 12° above and below the central C 4 plane. Oxidation with SbCl 5 /CH 2 Cl 2 leads to a dication‐bis (hexachloroantimonate), which is distorted to a twist conformation with dihedral angles of 35° by formation of two cyanine chains R 2 NCC(O)CNR 2 ⊕ ; at the same time the quinone CC bonds are stretched from 137 to 146 pm (see structure on the right).