Double exchange in the charge-transfer states of [Cr2(OH)3(tmtame)2]3+

The exchange splittings in the ground and ligand-to-metal charge transfer (LMCT) states of the dimer [Cr2(OH)3(tmtame)2]3+ (tmtame=1,1,1–tris(aminomethyl)ethane) are derived from optical absorption spectroscopy. The ground-state splitting is antiferromagnetic, whereas the energy ordering of the lowest observed LMCT states is ferromagnetic. This is a new situation. It is due to the dominant direct interactions between metal-centered orbitals, which leads to a double-exchange situation in the LMCT electron configurations.