Photoisomerization: New Complexes, Circular Dichroism, and the Faraday Effect

在光照下发生颜色变化的复合物被称为光致变色物。这些类型的化合物在不同的环境中有各种各样的应用，包括计算和光子材料。该研究项目致力于了解这些光致变色化合物（以及最终的材料）如何与光相互作用以产生颜色变化。大多数已知的光致变色化合物都是通过在超快时间尺度（皮秒）上发生的光触发分子重排而起作用的。关于分子如何将光能转化为势能从而引发分子重排，还有许多未解之谜。这项研究计划的一个新方面是发展新的光学实验技术，以监测分子在很短的时间尺度上的结构和磁性变化。新墨西哥大学（University of New Mexico）的杰弗里·拉克（Jeffrey Rack）教授正在开展一系列推广活动，鼓励学生从事STEM学科的职业。他对支持美国原住民学生、西班牙裔学生和女性的职业发展特别感兴趣。该项目提供仪器设计经验，以解决化学和物理之间的界面问题。该项目的多学科性质要求学生研究人员了解不同研究领域的文献贡献。美国国家科学基金会化学系化学结构、动力学和机制B项目的这项研究奖支持新墨西哥大学Jeffrey Rack教授的研究工作，该研究旨在研究一类新的过渡金属配合物，这种配合物在暴露于太阳辐射（光）下会改变结构和颜色。这些研究的重点是发现这种独特的发色团家族的动力学和热力学参数，这些发色团利用光在非常快的时间尺度上破坏和形成键。这些配合物的作用方式是结合的亚砜配体的激发态异构化。此外，还介绍了两种新的仪器技术。首先，Rack教授正在研究一种时间分辨的圆二色性的发展，以监测手性变化，不仅在过渡金属亚砜配合物中，而且在手性亚砜化合物中。其次，Rack教授正在开发一种法拉第旋转光谱仪器，用于监测化合物和材料中的磁场。该技术被用于监测分子光物理中三重态的产生和命运。新墨西哥大学（University of New Mexico）的杰弗里·拉克（Jeffrey Rack）教授开展了一系列推广工作，鼓励学生从事STEM学科的职业，并对支持美国原住民学生、西班牙裔学生和女性的职业发展特别感兴趣。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Complexes that undergo a change in color when exposed to light are termed photochromic. These types of compounds have a variety of applications in diverse settings including computing and photonic materials. This research program is dedicated to understanding how these photochromic compounds (and ultimately materials) interact with light to generate color changes. Most of the known photochromic compounds operate through a light-triggered molecular rearrangement that occurs on an ultrafast timescale (picosecond). There are many unanswered questions regarding how molecules convert light energy into potential energy to initiate molecular rearrangement. A new aspect of this research program is the development of new optical experimental techniques to monitor structural and magnetic changes in molecules on very short timescales. Professor Jeffrey Rack at the University of New Mexico is engaged in a series of outreach efforts to encourage students to pursue careers in STEM disciplines. He has a particular interest in supporting Native American students, Hispanic students, and women in their career development. The project provides experience in the design of instrumentation to address questions at the interface between chemistry and physics. The multidisciplinary nature of the project demand that the student researchers be aware of literature contributions in disparate research areas.This research award in the Chemical Structure, Dynamics and Mechanisms B Program within the Division of Chemistry at NSF supports the research efforts of Professor Jeffrey Rack at University of New Mexico to investigate a new class of transition metal complexes which change structure and color when exposed to solar radiation (light). These studies focus on discovering the kinetic and thermodynamic parameters for the action of this unique family of chromophores that utilize light to break and make bonds on a very fast timescale. The mode of action in these complexes is an excited state isomerization of the bound sulfoxide ligand. In addition, two new instrumental techniques are introduced. First, Professor Rack is studying the development of a time-resolved circular dichroism to monitor chirality changes, not only in transition metal sulfoxide complexes, but also in chiral sulfoxide compounds. Second, Professor Rack is developing a Faraday rotation spectroscopic instrument, which monitors magnetic fields in compounds and materials. This technique is used to monitor the creation and fate of triplet states in molecular photophysics. Professor Jeffrey Rack at the University of New Mexico is engaged in a series of outreach efforts to encourage students to pursue careers in STEM disciplines, and has a particular interest in supporting Native American students, Hispanic students, and women in their career development.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.