p-tert-Butyl thiacalix[4]arenes functionalized at the lower rim by o-, m-, p-amido and o-, m-, p-(amidomethyl)pyridine fragments as receptors for α-hydroxy- and dicarboxylic acids

Abstract A series of new p - tert -butyl thiacalix[4]arenes with o -, m -, p -amido and o -, m -, p -(amidomethyl)pyridine substituents at the lower rim in cone , partial cone , and 1,3- alternate conformations were synthesized. The ability of the obtained compounds to recognize the α-hydroxy (glycolic, tartaric) and dicarboxylic (oxalic, malonic, succinic, fumaric, and maleic) acids was investigated by UV–vis spectroscopy. Also, the efficiency and selectivity of binding, the association constants log  K a (10 2 to 10 7  M −1 ) and the stoichiometry were determined for the complexes of p - tert -butyl thiacalix[4]arenes with the acids. The receptors based on p - tert -butyl thiacalix[4]arenes with (amidomethyl)pyridine substitutes are most efficient in complexation in many cases.