13C-NMR-spektren von di- und trinuclearen polymethincyanin-farbstoffen |
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Authors: | W Grahn |
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Institution: | Fachbereich Chemie der Universität, D-3550 Marburg, LahnbergeGermany |
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Abstract: | 13C NMR chemical shifts are reported and assigned for two vinylogous series of polymethinecyanine dyes with indolenine- and benzothiazole nuclei. The influence of the heterocyclic groups and the chain length upon the chemical shifts of the methine carbons and upon the corresponding 1J13C1H-coupling constants has been studied. 13C chemical shifts of indolenine derivatives correlate with calculated π-electron densities. The combined application of 1H- and 13C NMR spectroscopy turns out to be a useful method for detecting steric hindrance in polymethine dyes. |
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