Selectivity of amides by host-guest inclusion

The mechanism of selectivity by enclathration of four amides, N-methylformamide (NMF), dimethylformamide (DMF), N-methylacetamide (NMA) and dimethylacetamide (DMA), has been investigated by employing a bulky, flexible host. We measured the two-component selectivity curves for a mixture of amides, whose proportions in the crystals were determined by H-1 NMR spectroscopy. The crystal structures of the single guest inclusion compounds were elucidated and analyzed. The subtle changes in the torsional flexibility of the host were correlated to the selectivity. The packing factor, which represents the occupied vs. available space by the guest in the crystal structures correlates with the measured selectivities.