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The synthesis and spectroscopic investigation of aza‐crown ethers with anthraquinone‐ and 1‐aminoanthraquinone‐functionalized side chains are described. Cation‐induced shifts in the UV/VIS absorption spectra of the ligands dissolved in propylene carbonate are observed only for Li+ among the alkali metal ions and for Mg2+ among the alkaline earth metal ions as well as for Ag+ and Tl+. Only hypsochromic shifts of the absorption spectra of anthraquinone‐bearing aza‐crown ethers are observed on protonation. The variations of the extinction coefficients are discussed with respect to the sequence of protonation of the different amino groups.
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Ossowski et al. (1990) studied this question.
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