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). This observation is supported by the occupation number of natural orbitals.