Dynamic Processes in Annulenes

量子化学研究的重点是[4 n]-和[4 n +2]轮烯的动力学过程的机制，包括构象变化，价异构化，键移动，和配置的变化。 通过采用密度泛函理论，耦合簇理论，和多组态量子力学方法的组合，这些过程的详细机制将被确定。 将计算的能垒与测量的能垒进行比较。对扭转偶联键移位机制在轮烯中的构型变化的范围的研究将使得能够详细比较Mobius，闭合壳层与平面，开壳层键移位在系统中，例如[12]-和[16]轮烯。 这将提供关于影响这些过程的障碍的因素的信息。 此外，将检查[4 n +2]轮烯（例如[10]-和[14]-）和[4 n]轮烯（例如[12]-）中的非平面键移位。 这种键转移过渡态将在闭壳层系统和单线态双自由基中进行研究。 这项工作将建立扭转偶联键转移作为轮烯化学的基本机制，并确认莫比乌斯芳香性存在于母体轮烯中。 它还将阐明平面的、键均衡形式的较大[4 n]轮烯的双自由基性质和反芳族特征的程度，并将能够识别新的莫比乌斯芳族物种以及新的轮烯异构体，这些都是可行的合成目标。由于该项目借鉴了学生在大二有机化学中学习的基本概念--芳香性、分子轨道理论、休克尔规则和周环反应--因此它代表了让学生参与研究的绝佳机会。考虑到弗朗西斯科大学的学生人数，特别有可能培训科学领域代表性不足的群体成员，特别是妇女和西班牙裔学生。 学生将获得各种计算技术的经验，此外，他们将学习如何处理一个研究项目，从搜索文献和制定问题，到展示和出版工作。在卡斯特罗-卡尼研究小组工作过的大多数本科生已经继续（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未来将成为量子力学应用于解决化学问题的专家的学生提供培训来加强网络基础设施。

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.