The effect of hetero-atoms on spin exchange coupling pathways (ECPs): a computational investigation.

The effect of heteroatoms on exchange coupling pathways and the presence of more than one coupling paths are investigated. The lone pairs of sp 2 -hybridized heteroatoms contribute to aromaticity but do not play any pivotal role in the spin coupling between two spin centers. A conceptual model to describe this behavior of heteroatoms has been introduced, and we name it as the hetero-atom blocking effect. With the occurrence of two π-orbital exchange coupling pathways (ECPs) via bridgehead heteroatoms (B-, N-, O-, or S-), the magnetic exchange coupling constants ( J ) can be viewed as a signed sum of different individual pathways. The effect of σ-electron coupling is also investigated in this work.