Spin-State Switching and Conductivity in Metal Complexes with Non-Innocent Ligands

Florida State University, Tallahassee FL

Investigators

Abstract

In this project funded by the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, a collaborative research team led by Professor Mykhailo Shatruk of the Department of Chemistry and Biochemistry and Professor Stephen O Hill of the Department of Physics at Florida State University will study stimuli-responsive molecules. These molecules are formed by surrounding transition metal ions by organic groups (ligands) capable of inducing a change in the magnetic state at the metal center. Magnetic state switching in molecular solids is largely unexplored and holds potential to develop into stimuli-responsive materials that could be used in new sensors and catalytic systems. The project will also explore the use of these molecules for the preparation of solids that combine magnetic state switching with electrical conductivity. Such multifunctional materials can be useful for the design of next-generation electronic devices and light-activated switches. The project will provide diverse research experiences to graduate and undergraduate students, including students from groups underrepresented in physical sciences. The outreach efforts include organizing nationwide undergraduate summer schools in magnetism and magnetic resonance spectroscopy. This project targets the synthesis and extensive characterization of spin-state switching materials based on the combination of Fe(II) ions with non-innocent (redox-active) organic ligands. The mechanism of the spin-state transition induced by a reversible electron transfer between an outer-sphere moiety and the coordinated ligand is largely unexplored. Establishing conditions that lead to such spin-state switching phenomena may open a new class of stimuli-responsive molecules, capable of translating temperature-, pressure-, or light-induced outer-sphere electron transfer into dramatic changes in the magnetic and structural states of the system. The team will systematically explore the design and synthesis of such complexes, followed by their detailed characterization by X-ray structural analysis, magnetic property measurements, and various types of magnetic resonance spectroscopy. The behavior of complexes will be studied under various external perturbations to establish the conditions that lead to spin-state switching. These stimuli-responsive molecules will be co-crystallized with anionic organic radicals to obtain hybrid multifunctional materials that combine spin-state switching with electrical conductivity. Changes in the spin configuration at the metal center typically lead to significant atomic displacements that propagate through the entire structure. The possibility to translate such structural perturbations at the magnetically active metal center to the organic substructure and modulate conductivity via spin-state switching is especially appealing if it can be stimulated by light irradiation. Beyond the discovery of a new class of stimuli-responsive complexes and materials, the findings expected from this project will be also of value to the areas of catalysis and bioinorganic chemistry. 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.