Dynamic Processes in Annulenes

本文提出的量子化学研究重点研究了[4N]-和[4N2]环烯的构象变化、价异构化、键移动和构型变化等动力学过程的机理。通过结合密度泛函理论、耦合团簇理论和多组态量子力学方法，将确定这些过程的详细机制。计算的势垒将与测量的势垒进行比较。对环烯构型变化的扭转偶联键位移机制范围的研究将使在[12]-和[16]环烯等体系中Mobius、闭壳和平面开壳键位移的详细比较成为可能。这将提供有关影响这些进程障碍的因素的信息。此外，还将考察[4N 2]环烯(例如[10]-和[14]-)和[4N]环烯(例如[12]-)中的非平面键移动。这种键移动的过渡态将在闭壳系统和单重态双自由基中进行研究。这项工作将建立扭转偶联键移作为环烯化学的基本机理，并证实母体环烯中存在Mobius芳香性。它还将阐明较大的[4N]环烯的平面键平衡形式的双自由基性质和抗芳香性程度，并将能够识别新的Mobius芳香族物种以及作为可行的合成目标的新的环烯异构体。因为这个项目借鉴了学生在二年级有机化学中学到的基本概念-芳香性、分子轨道理论、休克尔规则和周环反应-它代表了一个让学生参与研究的绝佳机会。考虑到旧金山大学的学生人数，培训代表不足的群体的科学成员，特别是女性和拉美裔学生的潜力尤其大。学生将获得各种计算技术方面的经验，此外，他们还将学习如何处理研究项目，从搜索文献和提出问题，到提出和出版工作。在卡斯特罗-卡尼研究小组工作的大多数本科生已经(或正在申请)在其他机构攻读高级学位。这里概述的项目将通过为学生提供培训来加强网络基础设施，这些学生将成为未来将量子力学应用于解决化学问题的专家。

The quantum chemical study proposed here focuses on the mechanisms of the dynamic processes in [4n]- and [4n+2]annulenes which include conformational changes, valence isomerizations, bond shifting, and configuration changes. By employing a combination of DFT, coupled cluster theory, and multi-configurational quantum mechanical methods, detailed mechanisms for these processes will be determined. The computed energy barriers will be compared with measured ones. Investigation of the scope of twist-coupled bond shifting mechanism for configuration change in annulenes will enable a detailed comparison of Mobius, closed-shell vs. planar, open-shell bond shifting in systems such as [12]- and [16]annulene. This will provide information regarding factors influencing the barriers for these processes. In addition, non-planar bond shifting in [4n+2]annulenes (e.g. [10]- and [14]-) and [4n]annulenes (e.g. [12]-) will be examined. This bond-shifting transition states will be studied in both closed-shell systems and singlet diradicals. This work will establish twist-coupled bond shifting as a fundamental mechanism in annulene chemistry and confirm that Mobius aromaticity exists in parent annulenes. It will also clarify the diradical nature and degree of antiaromatic character of planar, bond-equalized forms of larger [4n]annulenes and will enable the identification of new Mobius aromatic species as well as new annulene isomers that are viable synthetic targets.Broader Impacts. Because this project draws on fundamental concepts that students learn in sophomore organic chemistry-aromaticity, molecular orbital theory, the Huckel rule, and pericyclic reactions-it represents an excellent opportunity to engage students in research. Given the student population at the University of San Francisco, there is particular potential for training members of under-represented groups in science, especially women and Hispanic students. Students will gain experience in a wide variety of computational techniques and, in addition, they will learn how to approach a research project, from searching the literature and formulating questions, to presenting and publishing the work. The majority of undergraduates who have worked in the Castro-Karney research group have gone on to (or are applying to) pursue advanced degrees at other institutions. The project outlined here will enhance cyberinfrastructure by providing training for students who will be future experts in the application of quantum mechanics to the solution of chemical problems.