The Rate of Host-guest Complex Formation of Some Calixarene Derivatives Towards Neutral Aromatic Guests

Abstract

In order to determine the factors controlling the response time of the selective chemical sensors, the dissociation dynamics of the complexes of cailx[4]arene with p-chloro-trifluoromethyl-benzene was studied with molecular dynamics calculations. The calculated reaction rates show a contradictory temperature dependence in the absence or presence of tert-butyl substituent at the upper rim of calixarene host molecules. While the dissociation rate increases with the temperature in the case of calix[4]arene host, it decreases at higher temperature when tBu-calix[4]arene host is applied. The weak interaction energies and the low activation energy of the dissociation process validate that the complex equilibrium is rather thermodynamically controlled. Overall, the formation-decomposition processes of calix[4]arene host with p-chloro-trifluoromethyl-benzene guest seems to be a few tens faster then the case when tBu-calix[4]arene host is applied. This observation supports applications of the calix[4]arene rather than tBucalix[4]arene as host molecules in chemical sensors with short response time. This finding can contribute to the development of high-speed sensitive chemical sensors.