Development of the Crystallization-free Crystallography Method Using Porous Complexes

摘要

This review describes a newborn method for the single crystal X-ray analysis of non-crystalline or trace amount of compounds in which single crystal samples are prepared without recrystallization of the target compounds. In this method, porous coordination networks are employed as ‘crystalline sponges’ that can absorb target compounds from a contacting solution and orient them in the pores so that the structures of incorporated guest molecules can be analyzed by X-ray diffraction. Since the target compounds are delivered as a solution, they are needed to be neither crystal nor solid. Furthermore, the single crystal sample can be reproducibly prepared using only a 100 μm-sized host crystal, which allows nano-to-microgram scale X-ray analysis of non-crystalline compounds. With this technique, the crystal structure of guaiazulene, a natural hydrocarbon, has been determined with only 50 ng an amorphous sample. Combination with analytical HPLC system resulted in the development of a prototypical LC-SCD (liquid chromatography-single crystal diffraction) analysis. Here the principle, scope, and limitation of this ‘crystalline sponge method’ are shown with examples of the X-ray analysis including natural and synthetic compounds.