Here we discuss how charge transfer triplet states can be modulated by spin elaboration. We have probed the lowest-energy excited-state manifolds of a series radical (S = ½ NitronylNitroxide = NN) elaborated (t-Bu2bpy)Pt(Cat-Bridge-NN) complexes using variable-temperature magnetic circular dichroism (MCD) spectroscopy. Optical excitation into the low-energy ligand-to-ligand charge transfer (LL’CT) bands leads to a near quantitative electron transfer from the Cat donor to the bpy acceptor, creating open-shell charge separated states. This provides a convenient platform for facilitating the excited state exchange coupling between the three discrete spins (NN, SQ, and bpy radical). A critical excited state magnetic exchange mixing is observed between the excited “sing-doublet” (|S1,1/2&gt;) and “trip-doublet” (|T1,1/2&gt;) states, providing a means of accessing the T1 triplet of the bpy-Cat chromophore that is otherwise inaccessible in non-radical elaborated molecules. We show how exchange modulation of the excited state wavefunction leads to (1) dramatically different NN, SQ, and bpy radical spin populations relative to the ground state (2) the onset of magnetooptical activity, and (3) magnetic exchange control of chromophore triplet lifetimes. The results are discussed in terms of quantum entanglement of remote spin centers, efficient spin polarization transfer, and wavefunction control of excited state lifetimes.

Exchange-modulated spin polarizing triplet states

254th National Meeting (2017)

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