Quantum chemical approaches for controlling and evaluating intramolecular magnetic interactions in organic diradicals

In this review, rational design strategies for pure organic high-spin molecules with strong intramolecular magnetic interactions are presented, mostly focusing on the design of ferromagnetically coupled organic diradicals. After brief introduction of the calculation procedure for intramolecular magnetic coupling constant J using density functional theory (DFT), classification and standardization of magnetic character of well-known stable radicals and coupler units are discussed. Following the development of general strategy for the design of organic high-spin diradical by means of the classification and standardization scheme, applicability of the strategy for making pendent-type organic polyradical using zigzag graphene nanoribbons backbone is demonstrated. In a computational point of view, a scaling procedure and an optimization of Hartree–Fock exact exchange ratio of a hybrid DFT functional for better prediction of the J of diradicals are discussed.