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The Δ 2,2′ ‐Bi(2 H ‐1,4‐benzothiazine) Structural Motif of Red Hair Pigments Revisited: Photochromism and Acidichromism in a Unique Four‐State System
Author(s) -
Leone Loredana,
Crescenzi Orlando,
Napolitano Alessandra,
Barone Vincenzo,
d'Ischia Marco
Publication year - 2012
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201200673
Subject(s) - photochromism , chemistry , dication , protonation , benzothiazine , cationic polymerization , photochemistry , spectroscopy , solid state , structural motif , stereochemistry , polymer chemistry , molecule , organic chemistry , ion , biochemistry , physics , quantum mechanics
Abstract Complete spectral and computational characterization of Δ 2,2′ ‐bi(2 H ‐1,4‐benzothiazine) (BBTZ) demonstrated that the structures of the stable yellow form and the photogenerated red form were assigned incorrectly and should be revised to the cis ( Z ) and trans ( E ) isomers, respectively. A blue elusive dication generated upon further protonation of the violet cationic form was also identified by UV spectroscopy and DFT calculations. On the basis of these data, BBTZ can be appreciated as a robust four‐state system for various applications.