Auxiliary Atomic Relay Center Facilitates Enhanced Magnetic Couplings in Blatter’s Radical

The recent accomplishments in obtaining the strong ferromagnetic exchange interactions in organic diradicals have made the field quite fascinating and even more promising towards its technological applications. In this context, herein we report a unique combination of remarkably strong ferromagnetic exchange interactions coupled with the molecular rigidity utilizing super-stable Blatter’s radical as a spin source. The planar analogues of the parent Blatter’s radical obtained by annulation with a chalcogen coupled to nitronyl nitroxide (NN) are investigated using density functional theory (DFT) along with the wave function based multi-configurational self-consistent field (MCSCF) methods e.g. CASSCF/NEVPT2. The calculations reveal phenomenal modulation in exchange couplings upon annulation such that remarkably strong ferromagnetic interactions are realized especially for a certain class of the Blatter - nitronyl nitroxide diradicals. The modulation of spin spin interactions is rationalised by variation in spin density distribution and molecular torsional angles. We demonstrate that annulation in OMMs opens an additional coupling pathway via auxiliary X-atom acting as atomic relay center which strongly manipulates the magnitude of exchange couplings.