Syntheses and UV-visible spectroscopic properties of new ′fluorophilic′ fluorine- and perfluoroalkyl-substituted solvatochromic pyridinium N-phenolate betaine dyes

Syntheses and negative solvatochromism, of three new 'fluorophilic' fluorine- and perfluoroalkyl-substituted pyridinium N-phenolate betaine dyes 3-5 are described in order to obtain new zwitterionic dyes which should be less basic and better soluble in perfluorinated solvents than the solvatochromic standard betaine dyes 1 and 2, used to establish an empirical scale of solvent polarity, called the E-T (30) or E-T(N) scale. The new betaine dyes 3-5 were designed to allow an extension of the existing E-T (30) scale to new solvents. Copyright (C) 2001 John Wiley & Sons, Ltd.