Para-acylcalix[6]arenes: their synthesis, per-O-functionalisation, solid-state structures and interfacial assembly properties

The para-acylcalix[6]arenes bearing butanoyl, hexanoyl and octanoyl chains have been synthesized by Friedel-Crafts acylation of the parent calixarene. Persubstitution at the phenolic face was achieved to yield the methoxy-diethoxy, ethoxycarbonylmethoxy, methoxycarboxylic acid and butoxysulphonate derivatives. In the case of the derivatives, 5,11,17,23,29,35-hexa-octanoyl-37,38,39,40,41,42-hexa-methoxy-diethoxy-calix[6]arene, 5,11,17,23,29,35-hexa-butanoyl-37,38,39,40,41,42-hexaethoxycarbonyl methoxy-calix[6]arene and 5,11,17,23,29,35-hexa-octanoyl-37,38,39,40,41,42-hexaethoxycarbonyl methoxy-calix[6]arene the solid state structures were determined and show inclusion of two ester groups in the cavity. While for the para-acylcalix[6]arenes no stable monolayers can be formed at the air-water interface, stable monolayers are formed with the methoxy-diethoxy, ethoxycarbonylmethoxy, methoxycarboxylato compounds which show apparent molecular areas in the range 150-200 (2) depending on the length of the acyl chains.