Molecular species containing two or more paramagnetic centers in close proximity may exhibit properties that are distinct from those of the individual centers. In these spin-coupled systems, the spin exchange interaction creates an array of new spin states within both the ground- and excited-state manifolds, thereby impacting magnetic as well as optical properties of the system. Our research explores the influence that changes in electronic structure due to spin exchange have on reactivity, specifically with regard to photo-induced electron and energy transfer processes. This presentation focuses on systems we have designed, consisting of a μ-oxo μ-carboxylatodiiron(III) core acceptor covalently linked to a Ru(II) polypyridyl donor, where the strength of spin coupling within the diiron(III) core can be modified by protonating the oxo bridging group. In these compounds, we can use Heisenberg spin exchange to alter the spin states available to the acceptor without changing its composition and/or structural properties. The synthesis and characterization of these assemblies will be presented. Previous work on related systems has suggested a connection between the strength of spin exchange and the rate constant for bimolecular electron transfer. We have used steady-state and time-resolved absorption and emission spectroscopies to further investigate such connection in these new donor-acceptor complexes; those results will be discussed.

Photo-induced electron and energy transfer in Heisenberg spin-coupled donor-acceptor complexes

251st National Meeting (2016)

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