Long-chain dicarboxylic acids, that is, diacids containing 6 to 18 carbon atoms, are industrially used as monomers for a wide range of polymers, coatings, adhesives, and lubricants. Adipic acid, in particular, is a 2.5 billion kilogram commodity chemical used in the production of nylon 6.6.
1. Bis(trimethylammonium) alkane diiodides dynamically encapsulate dicarboxylic acids through intermolecular hydrogen bonds between the I- anions of the hosts and the carboxylic OH groups of the guests.
2. A selective recognition is realized when the size of the I-···HOOC(CH2/CF2)nCOOH···I- superanion matches the dication alkyl chain length.
3. Dynamic recognition is also demonstrated in solution, where the presence of the size-matching organic salt boosts the acid solubility profile, thus allowing efficient mixture separation. |