Design of high-spin organic molecules

The question of how to design high-spin organic molecules now reduces to the problem of how to arrange within a molecule many singly occupied degenerate orbitals that are orthogonal to one another. 

ORGANIC MOLECULES HAVING MANY DEGENERATE ORBITALS 

A straightforward answer to the above question would be a consideration of molecular symmetry. According to group theory, doubly degenerate molecular orbitals, denoted by the symbol e, can arise if a given molecule has one three-fold or higher axis of rotation, or if it has D2d symmetry. It is well 

The double degeneracy of NBMOs in m-[8] has nothing to do with the geometrical symmetry of the molecule, but, rather, with the connectivity of the two radical centres, or the phase relationship of the atomic orbitals in the conjugated system. Therefore, the term topological symmetry has been proposed to describe the connectivity of the carbon atoms carrying the 71-electrons and the periodicity of the 71-orbitals in this class of non-Kekule hydrocarbons. 

The Longuet-Higgins theory based on Huckel MO theory and Hund s rule was pioneering work in the area of molecular design of high-spin alternant hydrocarbons and has been appreciated for its predictability. 

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Intra- and inter-molecular spin alignment the conceptual framework of organic molecular magnets 182 Design of high-spin organic molecules 185 Exchange interaction 186... 

Organic building blocks for magnetism - design of high-spin organic molecules 109... 

Figure 14.32 C shows the NBMOs of m-xylylene, another prototype high-spin system. This structure also has two more than non- atoms. As such, its NBMO are non-disjoint, and a triplet state for the biradical is preferred. In our discussion of organic magnetic materials in Section 17.3 we will see that this /non- approach to predicting spin states can be extended to a remarkable degree, allowing the rational design of very high-spin organic molecules.

Design of ferromagnetic coupling among organic free radicals and high-spin molecules in molecular assemblies... 

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