Synthesis of a 1,3-bis(indoaniline)-derived calix[4]arene as an optical sensor for calcium ion

Abstract

A new chromogenic artificial receptor, a 1,3-bis(indoaniline)-derived calix[4]arene, has been prepared, the ethyl acetate derivative of which shows a selective Ca²⁺-induced pronounced colour change (wavelength change >100 nm) with an association constant of the order of 10⁶ in 99% EtOH.