Novel Heterometallic Polymers Induced by Host-Guest Cations: X-ray Structures of [(18-crown-6)KAgWS4]n and [{ (18-crown-6)Ba(DMF)4}(Ag2W2S8)]n

Abstract

α-Keto acids have characteristic unpleasant smell and chemical instability, which makes the usages of the materials difficult for pharmaceutical purposes. However, the inclusion compounds of the acids with cyclodextrins have no or slight smell and are chemically stable. Especially, an inclusion compound of optically active s-α-keto-β-methylvaleric acids (S-KMV) kept its activity for at least 120 days at room temperature, unlike its salt of basic amino acid. We tried to investigate the solid state structure of the inclusion compounds S-KMV / β-CD by the use of CPMAS ¹³C NMR spectroscopy. The comparison of the spectra of S-KMV / β-CD and KMV·1/2Ca·H₂O suggested that the S-KMV molecule is not so tightly included inside the β-CD cavity, but as a result of rotational isomerism restriction, it exists in a single conformer.