Molecular Capture Using the Precipitate of Creaming-Down by (−)-Epigallocatechin-3-O-gallate

An aqueous solution of equimolecular amounts of 2-chloropyrimidine and (−)-epigallocatechin-3-O-gallate (EGCg) afforded a colorless block crystal, which was determined to be a 2 : 2 complex of 2-chloropyrimidine and EGCg by X-ray crystallographic analysis. The 2 : 2 complex was formed by the cooperative effect of three intermolecular interactions, π–π and CH–π interactions, and intermolecular hydrogen bonds. Upon formation of the 2 : 2 complex, a 2-chloropyrimidine molecule was captured by a hydrophobic space formed by the three aromatic rings of A, B, and B′ rings of two EGCg molecules. The molecular capture abilities of various heterocyclic compounds using EGCg were evaluated by ratio of the heterocyclic compounds included in the precipitates of complex of EGCg to the heterocyclic compounds used. The amount of the heterocyclic compounds was measured by an integrated value of corresponding proton signals in the quantitative 1H-NMR spectrum.