Spin Effects on the Excited-state Dynamics of Transition Metal Complexes

Michigan State University, East Lansing MI

Investigators

Abstract

In this project, funded by the Chemical Structure, Dynamics and Mechanisms B Program of the Chemistry Division, Professor James K. McCusker of the Department of Chemistry at Michigan State University will be exploring how certain aspects of the electronic structure of transition metal-based complexes manifest in their photo-induced chemical properties. The specific aspect being studied is electron spin, which is the origin of many properties that people are widely familiar with (e.g., magnetism) but whose influence on photochemical reactivity has not been elucidated. To achieve this goal, the research program will involve the synthesis and characterization of a range of chemical systems that have been designed to enable the establishment of a clear correlation between the spin properties of the system and the photo-induced properties that they exhibit. Working at the interface of synthetic organic and inorganic and experimental physical chemistry, the research will provide a fertile training ground for students to understand and appreciate the interconnection between these formally disparate subfields of chemistry while developing fundamental new insights into how a very basic component of atomic structure can be leveraged to create new molecular functionality for a wide variety of potential light-enabled applications. Conservation of angular momentum is a fundamental property of Nature. While its influence on certain aspects of molecular science are well known, this research program is asking the following: to what extent does this concept manifest in photo-induced chemical processes? To address this fundamental question, the research will involve the synthesis of a series of transition metal-based donor-acceptor complexes whose spin properties can be systematically varied, either by judicious choice of a single metal ion (e.g., replacement of Cr(III) by Co(III)) or by exploiting the temperature dependence associated with the spin ladder of a Heisenberg exchange-coupled polynuclear metal cluster. Characterization of the photo-induced electron and/or energy transfer dynamics will focus on steady-state and time-resolved spectroscopies, including variable-temperature ultrafast optical and x-ray methods. It is anticipated that the research will provide insight into how zero-field spin polarization manifests in the photophysics of molecular systems with the goal of demonstrating how consideration of these effects can suggest new approaches for the development of compositional platforms using spin as a design feature for creating and manipulating photo-induced molecular functionality. 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.