ANALYSIS OF DYNAMIC STRUCTURE WITH CHEMICAL SHIFT SIMULATION METHOD

在极其灵活的分子中确定显著填充的构象是一个长期感兴趣的问题。因此，需要开发一种有效的方法来分析柔性化合物的构象。NMR化学位移反映分子结构。因此，局部环境的变化会影响化学屏蔽，相邻取代基引起的原子核化学位移的变化提供了有关所研究的原子核相对于这些附近取代基的相对排列的有价值的信息。因此，附近取代基引起的化学位移变化可用于构象分析。从这个角度出发，我们发展了一种利用化学位移模拟技术对柔性有机化合物进行构象分析的有效方法。以下是该项目的结果。(1)极性官能团的磁屏蔽效应被成功地估计，并应用于灵活的化合物，包括环番，分子钳，及其超分子复合物的构象分析。(2)利用经典的线电流近似，建立了一个非常有用的卟啉环电流效应模型。结果表明，该模型能较好地解释溶液中Sn^（IV）卟啉二羧酸配合物的结构. (3)利用化学位移模拟技术进行构象分析的新方法被发现是非常有效的灵活的有机化合物的结构解析。

Determination of significantly populated conformers in extremely flexible molecules is a matter of long-standing interest. It is desirable to develop an efficient method for the conformational analysis of the flexible compounds. NMR chemical shifts reflect molecular structure. Hence, variation in the local environment affects chemical shieldings, and the change in chemical shifts of nuclei caused by adjacent substituents provides valuable information about the relative arrangement of the nuclei under study with respect to these nearby substituents. The chemical shift changes caused by the nearby substituents can thus be applicable for conformational analysis. From this point of view, we have developed an efficient method for conformational analysis of flexible organic compounds by using chemical shift simulation technique. The followings are the results of the project.(1) Magnetic shielding effects of polar functional groups were successfully estimated and were applied for the conformational analysis of the flexible compounds, including cyclophanes, molecular tweezers, and their supramolecular complexes.(2) A very useful model of porphyrin ring current effect was developed by using a classical line current approximation. It was found that the model can successfully elucidate the structures of several dicarboxylate complexes of Sn^<(IV)> porphyrins in solution.(3) The newly developed method for the conformational analysis by using chemical shift simulation technique was found to be highly efficient for the structure elucidation of flexible organic compounds.