Analysis and Simulation of EPR Spectra of Photoexcited Triplet States

Multiple Pathways in the Triplet States Population for a Naphthalenediimide‐C60 Dyad

“…Indeed, energy transfer occurs with a projection of the 3 C 60 * polarization pattern onto the ZFS frame of NDI. [80] The polarization pattern seems to be consistent with an energy transfer in a fixed conformation (likely the folded conformation, see further), as the simulation is nicely obtained with a single set of population of the ZFS sublevels. Given that the Y-axis (intermediate component) of a methanofullerene is along the symmetry C 2 axis of the C 61 structure, [78] and the Z-axis of NDI is perpendicular to the molecular plane while the X-axis along the two amido nitrogens (see Scheme 1).…”

“…Possibly, a different conformation of the molecule (likely with much smaller probability) can lead to a higher interaction between the two groups and a larger CS character. The polarization shape points to a population of the ZFS states, not to a polarization of the Zeeman states, [80] which is compatible with a population mechanism based on ISC (possible mechanisms are regular ISC, spin-orbit charge transfer intersystem crossing, SOCT-ISC, or a charge recombination from a triplet state). By excluding the presence of hot triplet states after such a long delay, we tentatively assign this triplet to a state with partial localization of the spin density both on the C 60 and on the NDI.…”

“…[81] In this case the folded conformation brings the Y-axes of the two moieties to be almost parallel, and the intermediate population of 3 C 60 * (relative to the Y triplet component, see Table 1 and see Figure 6b) is transferred to the Y component of 3 NDI*. [80] If we assume that the other two pair of axes (X's and Z's) are parallel, the spin polarization of NDI is that of 3 C 60 , not that obtained by ISC from 1 NDI*.…”