Tetracyanoethylene-based organic magnets

Abstract

Several classes of organic magnets based upon the tetracyanoethenide radical anion, [TCNE].^–, either unbound, µ, and µ₄ bonded to zero, two and four metal sites have been reported. The putative µ₄ bonded V(TCNE)_x room temperature magnet has been extended to include M(TCNE)_x (M = Mn, Fe, Co, Ni) magnets. M for this class of magnets is assigned to be in the divalent oxidation state. A σ-[TCNE]₂^2– dimer intermediate has been isolated. The intrachain magnetic coupling for the 1-D coordination polymers having [TCNE].^– µ-bridge bonded to [Mn^IIIporphyrins]⁺ is discussed in the context of a structure–function correlation arising from the dihedral angle between the [Mn^IIITPP]⁺’s MnN₄ and [TCNE]^.– mean planes and the magnitude of magnetic coupling. This correlation is ascribed to the increasing importance of the σ-Mn^III d_z²/[TCNE]^.– p_z overlap with decreasing dihedral angle.