Design and Demonstration of Ferromagnetic Exchange Interactions in Organic Molecules

Strategy of how to endow organic molecules with many half-filled orthogonal orbitals has been studied systematically. In principle, parallel alignment of the two spins can become favored in π-conjugated diradicals, if the radical centers are placed in phase with the spin polarization of the intervening π-bonds. Studies of a wide variety of non-Kekulé hydrocarbons and the heteroatom analogues by EPR spectroscopy and magnetic susceptibility/magnetization measurements have revealed, however, that only a part of them related in connectivity to trimethylenemethane have high-spin ground states. Some super-high-spin polycarbenes, polynitrenes and persistent trinitroxides from these laboratories will be discussed in some detail.