Catalyzing Singlet Fission by Transition Metals: Second versus Third Row Effects.

The synthesis and characterization of platinum(II) and palladium(II) complexes bearing two (dimers Pt(L)Cl and Pd(L)Cl), one (monomers Pt(L)(L)Cl and Pd(L)(L)Cl), or no (reference compounds Pt(L)Cl and Pd(L)Cl) pentacene-based pyridyl ligands are presented. Photophysical properties of the dimers are probed by means of steady-state and time-resolved transient absorption measurements in comparison to the monomer and model compounds. Our results document that despite enhanced spin-orbit coupling from the presence of heavy atoms, intramolecular singlet fission (iSF) is not challenged by intersystem crossing.