| Abstract
| - Selectively deuterated, dodecyloxy substituted stilbenoid dendrimers of the first and secondgeneration were synthesized by a convergent synthesis, using the Wittig−Horner reaction. The photochemistry and the fluorescence in the different crystalline and liquid crystalline phases were investigated.Molecules deuterated at the α-position of the alkoxy chains were used to study the photoreactions in theneat phases by 1H NMR. Reactions of the double bonds are exclusively observed in the liquid crystalphases. No photoreactions occur in the crystalline state. The mobility of the dendrimers was studied bymeans of 2H solid-state NMR spectroscopy. The onset of the photochemistry for dendrimer 1 [all-(E)-1,3,5-tris[2-(3,4,5-tridodecyloxyphenyl)ethenyl]benzene] corresponds to the increasing mobility at the Cr/LCtransition. The first generation dendrimers still show large angle motion, whereas dendrimers of the secondgeneration 2 [all-(E)-1,3,5-tris(2-{3,5-bis[2-(3,4,5-tridodecyloxyphenyl)ethenyl]phenyl}ethenyl)benzene] arerestricted to librational motions. Photochemical conversion and fluorescence quenching for first and secondgeneration dendrimers 1 and 2 increase with increasing molecular motion and reach a maximum in theisotropic phase.
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