Premium
Synthesis and Photophysical Properties of Some Rigidized Hepta‐ and Nonamethine Mono‐ and Bis(merocyanines): Ring‐Opening of Quaternized 2‐Methylbenzothiazole
Author(s) -
Viteva Lilia,
Gospodova Tzveta,
Rashkova Jivka,
Abrahams Isaac,
Timtcheva Iliana,
Simova Svetlana,
Mazieres Marie Rose,
Wolf Jean Gérard
Publication year - 2007
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.200700125
Subject(s) - chemistry , merocyanine , regioselectivity , cyclopentene , ring (chemistry) , heteronuclear single quantum coherence spectroscopy , two dimensional nuclear magnetic resonance spectroscopy , stereochemistry , photochemistry , polymer chemistry , organic chemistry , photochromism , catalysis
We have developed a simple and efficient method for the synthesis of rigidized mono‐ and bis‐heptamethine merocyanines that contain one methine unit incorporated into a cyclopentene framework. The synthetic approach is based on C1/C5 regioselective nucleophilic addition of mono‐ and diketone lithium enolates to readily available pentamethine cyanines with inherent rigidity followed by a Hofmann elimination reaction. The new dyes react easily with heterocyclic benzothiazolium compounds containing an activated methyl group. Depending on the reaction conditions one or two reactive centres can be attacked, thus giving access to new merocyanine derivatives with a lengthened polymethine chain and/or ramified by a second heterocyclic unit. X‐ray crystallographic analysis reveals that the second heterocycle is incorporated via a sulfur bridge as a result of the opening of the benzothiazole ring. All new compounds were fully characterized by 1D and 2D NMR spectroscopic techniques ( 1 H, 13 C, DEPT, COSY, NOESY, HSQC with and without decoupling, HMBC). Their photophysical properties have been studied and correlated with solvent polarities. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)