Sugar-metal ion interaction: Crystal structure and spectroscopic study of potassium chloride complex with D-glucose, KCl·2C6H12O6

Potassium ion plays an important role in a variety of bioactivities, and many functions of potassium ion are exerted via coordination with saccharides. Up to now, the understanding of the biochemistry of K⁺/saccharides system is limited due to the lack of crystal structures of potassium ion-saccharide complexes. Herein, we have prepared single crystal of potassium chloride-α-D-glucose complex (KCl·2C₆H₁₂O₆) and its crystal structure has been successfully obtained. Potassium ion is coordinated to two α-D-glucose molecules. One α-D-glucose molecule provides 4α and 6β hydroxyl groups to coordinate to potassium ion, another one uses its 2α and 3β hydroxyl groups to coordinate to potassium ion. The single crystal structure of the complex exhibits some unusual structural features. K⋯K dimer is suggested to form because of shorter K⋯K distance (3.059 Å). Moreover, unusually short O⋯Cl distances between 2.3 and 2.5 Å are found in the crystal. Based on the crystal structure of the complex and the fact no free OH stretching vibrational absorption band is observed in FTIR spectra of the complex, assignment of hydrogen bonding linkage is achieved. Coordination with potassium ion brings about considerable structure variation on the glucose moiety of the complex. The structural changes can be reflected in the corresponding FTIR, Raman, FIR and THz spectra.