Development of New Chemical Triggers for Spin-State Switching

Colorado State University, Fort Collins CO

Investigators

Abstract

In this project funded by the Chemical Structure, Dynamics and Mechanism B program of the Chemistry Division, Professor Matthew Shores of Colorado State University is investigating new transition metal complexes whose physical (spin) properties are linked to the presence of guest molecules. This research aims to support the development of (1) inexpensive colorimetric sensors for colorless anions of biological (phosphates, chloride) and/or environmental (nitrate, cyanide, perchlorate) significance; and (2) new magnetic resonance contrast agents that reversibly turn on when interacting with target molecules. The project will support magnetic collaborations between the PI and 7 other research groups who do not have ready access to sensitive magnetic measurement techniques and data interpretation experience. Potential societal benefits include the discovery of new anion sensors and turn-on magnetic resonance contrast agents as well as a cross disciplinary training ground for graduate and undergraduate students. The project focuses on controlling the spin-states of first-row transition metal complexes via secondary, non-covalent interactions such as hydrogen bonding. The aim is to switch reliably between low- and high-spin states, in both directions, with a variety of chemical triggers. The research involves design and synthesis of new Fe(II), Fe(III) and Co(II) complexes, solid state and solution phase structural and magnetic characterization, and guest binding studies monitored by UV-Visible and NMR spectroscopies. Toward increasing environmental stability of promising molecules, cellulose-based hybrid materials are targeted where anion-dependent spin-state switching is expected to persist at the surface-solution interface. Incorporating anion-dependent spin-state switching properties to paper-based devices generates an opportunity for new sensors, easy to use, with wide portability and easy (visual) detection, suitable for wide distribution to citizens to estimate exposure to anionic pollutants.