Molecular modelling studies on auxetic host-guest calix(4)arene systems

Abstract

Molecular mechanical tools were used in order to study idealistic systems built from calix[4]arene systems, that have been shown in previous studies to exhibit auxetic character. The mechanical properties were investigated using a number of molecular modelling techniques which involved a validation study which determines that the Compass force field found on the Cerius2-0FF platform was found to be most suitable. One particular area in chemistry where calix[n]arene systems are being investigated involves the trapping of small guest molecules. In particular, single calix[n]arenes have been extensively used for entrapment of small ions and molecules due to their cone shaped cavity (applications include use as sensors and in molecular separation). As a consequence of their auxetic nature, the idealised calix[4]arene networks investigated here, have an advantage over single calix[ n ]arenes in the sense that entrapped molecules could be released as and when needed by stretching the network in a single direction. Models of these "polycalix" systems were built and their mechanical properties were analysed. The potential of the single calix[4]arenes as hosts for neutral (as well as polar) guest molecules is a known property of these organic structures, and the study carried out confirmed that for a good number of these idealistic host-guest systems, the auxetic character in these networks was retained. Being the first reported study on "polycalix" host-guest systems, this report may be regarded as a preliminary study on these systems' properties, which is to be substantiated by further work.