Investigating Metal-Metal Bond Polarization in a Heteroleptic Tris-Ylide Diiron System.

This article describes the synthesis, characterization, and S-atom transfer reactivity of a series of -symmetric diiron complexes. The iron centers in each complex are coordinated in distinct ligand environments, with one (Fe) bound in a pseudo-trigonal bipyramidal geometry by three phosphinimine nitrogens in the equatorial plane, a tertiary amine, and the second metal center (Fe). Fe is coordinated, in turn, by Fe, three ylidic carbons in a trigonal plane, and, in certain cases, by an axial oxygen donor.

Spin-Orbit versus Hyperfine Coupling-Mediated Intersystem Crossing in a Radical Pair.

While spin-orbit coupling (SOC) is typically the dominant interaction that couples singlet and triplet states within individual chromophores, hyperfine coupling (HFC) becomes important in multichromophoric systems, particularly in relation to the radical pair mechanism. Here, we use TD-DFT to calculate the spin-orbit coupling and hyperfine coupling between the first singlet and triplet charge transfer states of the radical pair Pyrene and ,-dimethylaniline. We show that, as the intermolecular donor-acceptor distance grows, SOC decays to zero (as one would expect) because singlet and triplet states are characterized by identical orbitals in space, while the HFC remains comparatively constant.