Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, and ACCEL (JST) , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
IUCrJ. 2016 Feb 12;3(Pt 2):139-51. doi: 10.1107/S2052252515024379. eCollection 2016 Mar 1.
Crystalline sponges are porous metal complexes that can absorb and orient common organic molecules in their pores and make them observable by conventional X-ray structure analysis (crystalline sponge method). In this study, all of the steps in the crystalline sponge method, including sponge crystal preparation, pore-solvent exchange, guest soaking, data collection and crystallographic analysis, are carefully examined and thoroughly optimized to provide reliable and meaningful chemical information as chemical crystallography. Major improvements in the method have been made in the guest-soaking and data-collection steps. In the soaking step, obtaining a high site occupancy of the guest is particularly important, and dominant parameters for guest soaking (e.g. temperature, time, concentration, solvents) therefore have to be optimized for every sample compound. When standard conditions do not work, a high-throughput method is useful for efficiently optimizing the soaking conditions. The X-ray experiments are also carefully re-examined. Significant improvement of the guest data quality is achieved by complete data collection at high angle regions. The appropriate disorder treatment of the most flexible ZnI2 portions of the host framework and refinement of the solvents filling the remaining void are also particularly important for obtaining better data quality. A benchmark test for the crystalline sponge method toward an achiral molecule is proposed with a guaiazulene guest, in which the guest structure (with ∼ 100% site occupancy) is refined without applying any restraints or constraints. The obtained data quality with R int = 0.0279 and R 1 = 0.0379 is comparable with that of current conventional crystallographic analysis for small molecules. Another benchmark test for this method toward a chiral molecule is also proposed with a santonin guest. The crystallographic data obtained [R int = 0.0421, R 1 = 0.0312, Flack (Parsons) = -0.0071 (11)] represents the potential ability of this method for reliable absolute structure determination.
多孔金属配合物晶体海绵可在其孔道中吸附和定向常见的有机分子，并用常规 X 射线结构分析（晶体海绵法）对其进行观察。在这项研究中，对晶体海绵法的所有步骤（包括海绵晶体的制备、孔溶剂交换、客体浸泡、数据收集和晶体学分析）进行了仔细的检查和彻底的优化，以提供可靠和有意义的化学信息，作为化学晶体学。该方法在客体浸泡和数据收集步骤方面取得了重大改进。在浸泡步骤中，获得客体的高占据率尤为重要，因此必须针对每个样品化合物优化主导参数（例如温度、时间、浓度、溶剂）。当标准条件不适用时，高通量方法可用于有效地优化浸泡条件。还仔细重新检查了 X 射线实验。通过在高角度区域完全收集数据，实现了客体数据质量的显著提高。对于获得更好的数据质量，适当处理主体框架中最灵活的 ZnI2 部分的无序和对填充剩余空隙的溶剂的精修也非常重要。通过使用guaiazulene 客体提出了一种针对非手性分子的晶体海绵法的基准测试，其中客体结构（占据率约为 100%）无需施加任何限制或约束即可进行精修。获得的 R int = 0.0279 和 R 1 = 0.0379 的数据质量与当前小分子的常规晶体学分析相当。还提出了另一种针对手性分子的该方法的基准测试，使用 santonin 客体。获得的晶体学数据[R int = 0.0421，R 1 = 0.0312，Flack（Parsons）= -0.0071（11）]代表了该方法用于可靠绝对结构确定的潜在能力。
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