[MIII(dmit)2]--Coordinated MnIII Salen-Type Dimers (MIII = NiIII, AuIII; 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)}](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 P (1) over bar 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 . cm(-1) and E-a = 182 meV for 1a and sigma(r.t.) = 1 x 10(-4) S . 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 la 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)(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.