Abstract:
Ruthenium(II) polypyridine sulfoxide complexes are photochromic. Excitation within the 3MLCT absorption manifold yields a charge-separated state, which prompts S-to-O isomerization on the picosecond timescale. The reverse O-to-isomerization can occur photochemically, but always thermally as it is metastable on the ground state potential energy surface. Electrochemical and Absorption data show that these isomers show remarkable differences in electronic structure. Ultrafast transient absorption spectroscopy reveals the mechanistic details of this isomerization. Moreover, photocrystallographic data shows that these molecular rearrangements can occur within the crystalline state and that this reactivity is determined by the identity of the weakly coordinating anion. Lastly, we will discuss efforts to reproduce this chemistry on iron, which introduces the idea that isomerization can stabilize one spin state over another