Theoretical design of a high-spin organic molecule

Quantum chemistry calculations may rationalise the search for pure organic ferromagnets. Neutral molecules based on two rings coupled through a central C–C bond were tested. The triplet ground state is evidenced by a positive singlet–triplet splitting, which ranges between 0.2 and 2 eV. Using dimer geometries found in organic radicals as a model for the intermolecular interactions, it was found that a triplet or a quintet ground state is stable against the low-spin state of the dimer. Consequently, this series of molecules, were its synthesis possible, appears to be attractive for building new organic ferromagnets.