Imaging Technique with Liquid Crystals of Halogen‐Containing 3,6‐Distyrylpyridazines (=3,6‐Bis(2‐phenylethenyl)pyridazines)

Abstract

The 3,6-bis{(1E)-2-[4-(dodecyloxy)phenyl]ethenyl}pyridazine (1a) was regio-and stereoselectively brominated or chlorinated to the (Z,Z)-compounds 3 and 6, respectively. The conjugated core of these systems represents a mesogen for smectic (and nematic) liquid crystals and, moreover, a chromophore with an absorption at the UV/VIS border. Irradiation and efficient intersystem crossing to the triplet state leads to isomerization reactions (Z,Z) ! (E,Z) in solution as well as in the thermotropic LC phases. Since (E,Z)-configurations are only tolerated to a very small extent by the mesophases, the photoinduced transition S ! N ! I of 6 can be used as an imaging technique.

Fluorophobic Effect Promoting Lamellar Self‐Assembly of Donor Acceptor Dyes

“…In addition, due to the fact that E/Z mixtures of the merocyanines were employed in the current study, we surmised that an increasing amount of bent Z isomer should decrease the mesophase stability in a similar fashion as was reported previously by Meier, Lakehal, Sworakowski, Bobrovsky, and Saïdi‐Besbes albeit to a smaller extent because the respective double bond is not located in the centre of the merocyanine in contrast to the previously reported stilbenes, azobenzenes and the like. The results in Figure suggest that the amount of E ‐isomer indeed contributes to the mesophase range and stability.…”

Incorporation of pyridazine rings in the structure of functionalized π-conjugated materials

“…Halogenated 3,6-distyrylpyridazines derivatives 155 and 156 have been also synthesized by the same team (Scheme 31). 70 For Scheme 26 Scheme 27 these compounds, liquid crystal and photoisomerisation properties are observed. An increase of the (E,Z)/(Z,Z) ratio to a certain limit leads to the breakdown of the smectic phase S c .…”