Molecular Recognition in Organic Crystals

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1.Chiral recognition mechanism of trisphenylcarbamates of cellulose which are effective chiral stationary phases for HPLC was investigated using NMR spectroscopy. The phenylcarbamate derivatives are soluble in chloroform and exhibited chiral discrimination for several enantiomers in NMR as well as in HPLC.The binding geometry and dynamics between the derivatives and enantiomers were investigated on the basis of spin-lattice relaxation time, ^<1H> NMR titrations, and intermolecular NOEs. On the basis of these results, combined with molecular modeling, the chiral discrimination mechanism was reasonably explained.2.Poly ((4-carboxyphenyl) acetylene) and poly ((4-dihydroxyborophenyl) acetylene) were found to exhibit the induced circular dichroism (ICD) based on the helical structures by the complexation with chiral molecules for instance, chiral amines and sugars, respectively. The polyacetylenes can be used as a novel probe for determining the chirality of amines or sugars.3.The crystal structures of several adducts of the bis (resorcinol) and bis (pyridine) derivatives of anthracene or anthraquinone were determined by X-ray analysis. Anthracene-bis (resorcinol) compound forms molecular sheets consisting of hydrogen-bonded chains. All the adducts show a strong tendency to form columns, which are constructed via self-assembly of hydrogen-bonded one-dimensional or two-dimensional networks.4.X-ray crystallographic studies were carried out for conglomerates and racemic compounds, and enantiomerically pure salts of chiral primary amines with achiral acids. The results suggest that the formation and the assembly of 2_1-columns between conglomerate salts and racemic compound salts are governed by van der Waals interaction between the 2_1 columns.