Magnetic Modulation in Heteroallene and Heterocumulene Based tert-butyl Nitroxide Diradicals: Spin Delocalization and Conformation Play Crucial Roles.

We have theoretically investigated the magnetic properties of heteroallene (>C=C=X-) and heterocumulene (>C=C=C=X-) based tert-butyl nitroxide diradicals (X is P/As). Calculation of magnetic exchange coupling constant (J) shows ferromagnetic interaction in heteroallene based diradicals. Whereas, in heterocumulene based diradicals, tuning of J value from antiferro- to ferro-magnetic state is observed from Z- to E- isomer.

Magnetic and transport properties of conjugated and cumulated molecules: the π-system enlightens part of the story.

We have investigated the intramolecular magnetic exchange coupling constants (J) for a series of nitronyl nitroxide diradicals connected by a range of linear conjugated and cumulene couplers focusing on the unusual π-interaction properties within the couplers. Distance between radical centers, spin density within the couplers, as well as the dihedral angles between the radical centers and the plane of the coupler influence the strength of magnetic coupling. We also establish that with the increase in the length of the coupler, the strength of magnetic interaction in conjugated and cumulated systems varies in a different way.

A Perspective on Designing Chiral Organic Magnetic Molecules with Unusual Behavior in Magnetic Exchange Coupling.

A total of nine diradical-based organic chiral magnetic molecules with allene and cumulene couplers have been theoretically designed, and subsequently, their magnetic property has been studied by density functional theory. It is found that with an increase in length of the coupler, a remarkable increase in spin density within the coupler takes place. An increase in the length of the coupler reduces the energy of LUMO, and a smaller HOMO-LUMO gap facilitates stronger magnetic coupling and thereby a higher magnetic exchange coupling constant (J).