Close Non-Bonded Contacts: Effects on Structure and Conformational Reactions

在这个由化学部化学结构、动力学和机制B计划资助的NSF项目中，小罗伯特·帕斯卡教授。杜兰大学化学系的一种新型化合物，这种化合物含有相互作用的官能团，这些官能团在非常紧密的非键接触和/或相互作用的分子表面上，接触程度随着构象的不同而变化。其中一些分子可能会显示出键长和非键长缩短的“世界纪录”。这些化合物中的许多具有在自然界中基本上未知的非常不寻常的形状。这项研究在本质上是基础的，将提高我们对化学键的理解。这些化合物还可能具有独特的手性和光物理性质，使它们成为手性催化剂、手性传感器或有机电子材料的候选者。它们还对化学和生物科学中广泛使用的计算方法的准确性进行了严格的测试。这项研究非常适合于培训各级实验室化学家，包括科学上代表不足的基团的学生。In-环番、复杂的多苯基芳香族分子和包含强相互作用表面的多环芳香族结构有一个共同的特征：常规和色散校正密度泛函理论(DFT)计算对它们的描述截然不同，但这些方法中哪种方法更符合实验？(1)所提出的In，In-环番分子含有沿着分子中心轴非常紧密地挤压在一起的官能团，但两种类型的DFT计算给出了显著不同的原子间距离。(2)所提出的多苯芳烃具有手性最低能构象，但两种密度泛函理论计算给出的外消旋势垒截然不同。(3)具有相互作用的芳香族多环的分子可以采用不同的构象，以最大化或最小化分子内的van der Waals相互作用，但两种类型的密度泛函计算给出了它们相互转化的非常不同的平衡常数。X射线结晶学、动态核磁共振光谱、手性载体上的层析分辨率和平衡常数的核磁共振测定被用来判断各种计算方法的准确性。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

In this NSF project, funded by the Chemical Structure, Dynamic & Mechanism B Program of the Chemistry Division, Professor Robert Pascal, Jr. of the Department of Chemistry at Tulane University prepares new compounds that contain interacting functional groups in very close, but non-bonded contact and/or interacting molecular surfaces whose extent of contact varies with conformation. Some of these molecules are likely to exhibit "world record" shortening of bond distances and non-bonded contact distances. Many of these compounds have highly unusual shapes that are essentially unknown in the natural world. The research is fundamental in nature and will improve our understanding of chemical bonding. These compounds may also possess unique chiroptical and photophysical properties that would make them candidates for chiral catalysts, chiral sensors, or organic electronic materials. They also provide stringent tests of the accuracy of computational methods that are widely used in the chemical and biological sciences. The research is ideal for the training of laboratory chemists at all levels, including students from underrepresented groups in science.In,in-cyclophanes, complex polyphenyl aromatic molecules, and polycyclic aromatic structures containing strongly interacting surfaces share a common feature: conventional and dispersion-corrected density functional theory (DFT) calculations describe them quite differently, but which of these methods better agrees with experiment? (1) The proposed in,in-cyclophanes contain functional groups pressed very close together along the central axes of the molecules, but the two types of DFT calculations give significantly different interatomic distances. (2) The proposed polyphenyl aromatics have chiral lowest-energy conformations, but the two types of DFT calculations give very different barriers for racemization. (3) The proposed molecules with interacting aromatic polycycles may adopt distinct conformations that either maximize or minimize intramolecular van der Waals interactions, but the two types of DFT calculations give very different equilibrium constants for their interconversion. X-ray crystallography, dynamic NMR spectroscopy, chromatographic resolution on chiral supports, and NMR determination of equilibrium constants are being employed to judge the accuracy of the various computational methods.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.