5,11,17,23‐Tetrakis[(p‐carboxyphenyl)azo]‐25,26,27,28‐tetrahydroxy Calix[4]arene: Crystal Structure and pH Sensing Properties

Abstract

Treatment of 5,11,17,23-tetrakis[(p-carboxyphenyl) X-ray analysis of 2•4DMF revealed that its calix[4]arene core adopts a flattened cone conformation in which opposed phenyl groups take parallel or sharply inclined positions. The intra-and intermolecular hydrogen-bonding interactions and the π…π interactions form a 2D hydrogen-bonded wavelike network. Compound 2 had a unique reversible color change in a wide pH range from 1 to 13.5 and showed interesting pH sensing properties.