Networked-Cage Microcrystals for Evaluation of Host–Guest Interactions

We have developed a new synthetic protocol for the preparation of a microcrystalline powder (median size: X50 = 25 μm) of networked M6L4 cages 1a for the stationary phase of an affinity column on a greater than 50 g scale. Analogously to large single crystals 1b (X50 ≈ 0.5 mm), microcrystals 1a accommodate guest molecules tetrathiafulvalene (TTF) and fullerene (C60) at up to 32 and 35 wt %, respectively. Importantly, the host-guest interactions within networked cages could be evaluated in terms of the retention time from HPLC analysis by using microcrystals 1a as the stationary phase. In this way, favorable guests for networked cages 1 and even solution M6L4 cage 2 could easily be assessed by HPLC.