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

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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.