Makoto Fujita

Crystalline Sponge Method: X-ray Analysis without Crystallization on the Microgram Scale

X-ray single crystal diffraction (SCD) analysis has the intrinsic limitation that the target molecules must be obtained as single crystals.  Here, we report a new protocol for SCD analysis that does not require the crystallization of the sample.  In our method, tiny crystals of porous complexes are soaked in the solution of a target, where the complexes can absorb the target molecules.  The crystallographic analysis clearly determines the absorbed guest structures along with the host frameworks.  As the SCD analysis is carried out with only one tiny crystal, the required sample amount is of the nano-to-microgram order.  With chiral guests, the space group of the crystal turned into chiral (C2 or P1), enabling the determination of absolute configuration of the guests from the anomalous scattering from the host ZnI₂ component.  We demonstrate that even ~50 ng of a sample is enough to be analyzed.  When combined with high performance liquid chromatography (HPLC), multiple fractions were directly characterized, establishing a prototypical LC-SCD analysis.