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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.

The all-(E)-configured tetrastilbenylmethanes 3a−e and 5a,b can be obtained by fourfold Wittig−Horner reactions. The tetrahedral arrangement of these compounds guarantees independent stilbenoid chromophores with a high chromophore density. Apart from (E)/(Z) isomerization reactions, irradi-