Organometallics in cyanine chemistry -: Synthesis, reactivity and photophysical properties of some heptamethine merocyanine dyes

A one-pot reaction between lithium reagents of ketones and pentamethine cyanine dyes affords a series of seven-carbon merocyanines in good to excellent yields. In subsequent reactions with "soft" organolithium reagents they can be easily converted into anionic cyanine dyes, oxonols. The synthetic potential and limitations of this reaction are discussed. Absorption and fluorescence behavior of the studied merocyanines were found to depend on their substitution patterns and the solvent used. Based on the relationship between the absorption maxima and ET(30) (= solvent polarity parameter) constants, a different nature of the absorbing state in protic and non-protic solvents can be assumed. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).