Tuning Heterocalixarenes to Improve Their Anion Recognition: A Computational Approach.

We have explored and analyzed the physical factors through which noncovalent interactions in anion sensing based on calixarene-type hosts can be tuned, using dispersion-corrected DFT and Kohn-Sham molecular orbital (KS-MO) theory in conjunction with a canonical energy decomposition analysis (EDA). We find that the host-guest interaction can be enhanced through the introduction of strongly electron-withdrawing groups at particular positions of the arene and triazine units in the host molecule as well as by coordination of a metal complex to the arene and triazine rings. Our analyses reveal that the enhanced anion affinity is caused by increasing the electrostatic potential in the heterocalixarene cavities. This insight can be employed to further tune and improve their selectivity for chloride ions.