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DOI: 10.1055/s-0028-1083374
Dendritic Triphenylmethylium and Tetraphenylmethane Compounds
Publikationsverlauf
Publikationsdatum:
11. Februar 2009 (online)
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Abstract
Stilbenoid dendrimers possessing a methanol or methane core are prepared using Wittig-Horner reactions. The dendritic tris(stilbenyl)carbinols 3a-c are converted into the corresponding methylium salts 3′a-c on treatment with trifluoroacetic or tetrafluoroboric acid. The extended cross-conjugation in the dendritic methylium ion 3′c results in a long-wavelength absorption (λmax = 697 nm) whereas the conjugated model systems 3′a and 3′b are red-shifted (λmax = 772 nm and 748 nm, respectively). Charge delocalization in the cations is evident from the low-field shifts of the ¹³C NMR signals. In contrast to the dark-blue dyes 3′a-c, the tris(stilbenyl)carbinols and tetrakis(stilbenyl)methane derivatives 3a-c and 7 exhibit long-wavelength absorption bands in the UV region.
Key words
stilbene - charge delocalization - Wittig-Horner reaction - olefination - dendrimers - dyes
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