Chromoionophoric Pyridinium‐<i>N</i>‐phenolate Betaine Dyes

Abstract

The halochromism of the crown-ether-substituted betaine dyes 1 is very sensitive to the cation size of the added electrolytes. The strongest hypsochromic shift of the longest- wavelength UVIVIS absorption results for n = 0 with Na⊕, n = 1 with K⊕, and n = 2 with Cs⊕. Thus, the dyes 1 may be useful as indicators.