Scanning Tunneling Microscopy on Complex Formation of Cyclodextrins and on Their Catalytic Mechanism for Selective Organic Synthesis

点击翻译按钮获取中文摘要

Scanning tunneling microscopy (STM) on cyclodextrins and their complexes with various guests has been achieved to obtain molecular-level information on these attractive cyclic oligosaccharides. By choosing appropriate conditions for the STM measurements, clear images of molecular structures of cyclodextrins were for the first time obtained. Typical examples are the images of (1) parent cyclodextrins, (2) the complexes with ethylene glycol, (3) complexes with adamantanecarboxylate, (4) cyclodextrin derivatives having a glucose branch, (5) the complexes with phenol, and (6) the complexes with chloroform. The complexes in the items (5) and (6) are directly associated with the selective organic synthesis which was previously found by the authors. The present results should greatly facilitate the molecular design of cyclodextrin complexes which have desired physicochemical and catalytic properties. It was also found that cyclodextrins have specific activities for self-aggregation. The structures of the aggregates are highly dependent on the kind of guest compounds, cyclodextrin derivatives, and substrates, indicating the possibility of artificial control of the aggregation (and thus the preparation of nano-structures assemblies of cyclodextrins).