Herstellung, Struktur und Eigenschaften neuartiger kettensubstituierter und chiraler Trimethincyanin‐Farbstoffe mit Indolin‐Endgruppen¹⁾

Abstract

Synthesis, Structure, and Properties of Novel Chain‐Substituted and Chiral Trimethine Cyanine Dyes with Indoline End Groups Synthesis and spectroscopic properties of the trimethine cyanine dyes 3, 8a, b , and 13a, b as well as 14a‐c with new substitution patterns are described. Constitutions and configurations of 3, 8a, b and 14c have been determined by X‐ray analyses (Figures 1, 2, and 6). Dye 3 exists in the previously unknown di‐cis ( E, E, Z, Z ) configuration along the methine chain. Attempts to prepare 3 in a base‐catalysed reaction unexpectedly led to the rearranged trimethine cyanine dyes 8a, b with a centre of chirality in one of the indoline end groups. Using this Wagner‐Meerwein rearrangement after resolution, the chiral heterocyclic quaternary salts ( S )‐ 12a‐ c have been prepared, from which the optically active trimethine cyanine dyes ( S,S )‐ 14a‐c have been obtained for the first time. The UV/VIS spectra of 3, 8a and 13a (Figure 7) as well as the CD spectra of 12a and 14a (Figures 3 and 4) are compared and discussed.