Capture of Sulfur Mustard by Pillar[5]arene: From Host-Guest Complexation to Efficient Adsorption Using Nonporous Adaptive Crystals

Sulfur mustard (SM) has been the most frequently used chemical warfare agent. Here, we present the efficient containment of SM and its simulants by per-ethylated pillar[5]arene (EtP5). EtP5 exhibited strong binding abilities toward SM and its simulants not only in solution but also in the solid state. The association constant (K-a) between SM and EtP5 was determined as (6.2 +/- 0.6) x 10(3) M-1 in o-xylene-d(10). Single crystal structure of SM@EtP5 showed that a 1:1 inclusion complex was formed, which was driven by multiple C-H center dot center dot center dot pi/Cl/S and S center dot center dot center dot pi interactions. In addition, activated crystal materials of EtP5 (EtP5 alpha) could effectively adsorb SM simulants at solid-vapor phase; powder X-ray diffraction patterns and host-guest crystal structures indicated that the uptake process triggered a solid-state structural transformation. More interestingly, the captured guest molecules could be stably contained in EtP5 alpha for at least 6 months in air at room temperature.