PYRIDINIUM N-PHENOLATE BETAINE DYES AND THEIR APPLICATION TO THE CHARACTERIZATION OF THE POLARITY OF SOLVENTS .22. SYNTHESES AND UV VIS SPECTROSCOPIC PROPERTIES OF SOLVATOCHROMIC, HALOCHROMIC, AND CHIRO-SOLVATOCHROMIC PYRIDINIUM N-PHENOLATE BETAINE DYES WITH 4 STEREOGENIC CENTERS/

Syntheses (Schemes 1-3), negative solvatochromism (Table 1), cation-in duced negative halochromism (Table 2), and chiro-solvatochromism (Tabl es 3 and 4) of the new crown ether-substituted chiral pyridinium N-phe nolate betaine dyes 18a, b and 28a, b, each possessing four stereogeni c centers, are described. The absolute configuration at the four stere ogenic centers of the chiral betaine dyes has been confirmed by X-ray crystal structure analysis of the intermediate phenol 14a (Figure 1). Solutions of the chiral betaine dyes 18a, b and 28a, b, prepared by ad dition of monochiral amines and amino alcohols to solutions of the sal ts 17a, b and 27a, b in ethanol, exhibit in some cases small but signi ficant chiro-solvatochromic band shifts of up to Delta lambda = 10-12 nm (Tables 3 and 4), caused by chiral recognition of the monochiral gu est molecules.