Topology and Spin Alignment in Organic High-Spin Molecules

Organic high-spin molecules are ideal model compounds for organic magnetic materials such as organic superparaand ferro-magnets which have recently been attracting increasing interest [1]. The related experimental [2] and theoretical works [3] have been done to serve their molecular design for the last two decades. High-spin polycarbenes as organic high-spin systems, in spite of their highly chemical reactivity, are very important from the view point .of organic magnetism as well as of spin ordering/spin control in chemistry from the following reasons, (i) One of the most prominent features of the highspin polycarbenes is multi-electron open shell systems in the ground or low-lying excited states which arise from degenerate delocalized 7t orbitals and from o dangling orbitals localized at divalent carbon atoms, the latter orbitals being nearly degenerate with the highest half-filled K orbitals. (ii) The degeneracy of their n orbitals is governed by a particular connectivity of n electron network, i.e. by the topology of the rc electron network.