Structure and magnetic interaction in organic radical crystals. 6. Spin-transfer crystals: A theoretical study

The nature of the spin exchange interaction in half-filled bands of one-dimensional (1-D) stacks of mixed molecular radical crystals (MMRC) with the general formula ...R * ....H....R * ....H.... (R * is a π radical, and H is a diamagnetic polycyclic molecule) has been investigated theoretically. The intermolecular interaction is accompanied by spin transfer from R * to H and determines the spin-spin interaction within the 1-D stacks of the MMRCs. The nature and the magnitude of the magnetic interaction in these structures are investigated using the band theory. At a given topology and geometry of the MMRC stacks the antiferromagnetic interaction in the parent molecular radical crystals...R * ....R * .... becomes ferromagnetic in the MMRCs and vice versa. It was found that the effective exchange integral J e f f of MMRCs, belonging to a given group with one and the same radical but different H, is proportional to the diamagnetic susceptibility Χ(H). A new topological effect of the exchange interaction in MMRCs is formulated.