[M(III)(dmit)2](-)-coordinated Mn(III) salen-type dimers (M(III) = Ni(III), Au(III); dmit2- = 1,3-dithiol-2-thione-4,5-dithiolate): design of single-component conducting single-molecule magnet-based materials.

Four linear-type tetranuclear complexes, Mn(5-Rsaltmen){M(dmit)(2)} (R = MeO, M = Ni, 1a; M = Au, 1b; R = Me, M = Ni, 2a; M = Au, 2b), were synthesized and structurally characterized (5-Rsaltmen(2-) = N,N '-(1,1,2,2-tetramethylethylene)-bis(5-Rsalicylideneiminate), dmit(2-) = 1,3-dithiol-2-thione-4,5-dithiolate). These compounds crystallize in the same triclinic P1 space group (Z = 1) and have a similar molecular structure with a bridging array of [M-(dmit)-Mn-(O(Ph))(2)-Mn-(dmit)-M] and a packing feature where the respective sets of 1a/1b and 2a/2b are isomorphous. Intermolecular pi-pi/S...S contacts are observed between the coordinating M(dmit)(2) moieties to form zigzag stair-like columns along the a axis direction. Huckel calculations revealed a strong intermolecular dimerization within the Ni(dmit)(2) column that makes them magnetically silent even at room temperature. Nevertheless, 1a and 2a with M = Ni behave as semiconductors with sigma(r.t.) = 7 x 10(-4) S x cm(-1) and E(a) = 182 meV for 1a and sigma(r.t.) = 1 x 10(-4) S x cm(-1) and E(a) = 292 meV for 2a, while 1b and 2b with M = Au are insulators. As a result of the strong dimerization of the Ni(dmit)(2) anions, the magnetic properties of 1a are essentially identical to those of 1b and 2b, which can be described as isolated Mn(III) dimers, acting as single-molecule magnets (SMM). Meanwhile, the magnetic properties of 2a are dominated by the intermolecular Mn...Mn antiferromagnetic interactions via the singlet Ni(dmit)(2)(2-) dimer (J(Mn...Mn)/k(B) = -2.85 K), inducing a long-range antiferromagnetic order at T(N) = 6.4 K. The present systems are unique materials made of neutral single-component complexes that exhibit two major solid-state properties, that is, electrical conductivity and magnetism, varied as semiconductor/SMM for 1a, insulator/SMM for 1b and 2b, and semiconductor/antiferromagnet for 2a by tuning metal center and partial structural modification.