Crystal structure and magnetic properties of Gd(2)([18]crown-6)(2)(OH)(2)(CH(3)CN)(2)[Ni(dmit)(2)](2) (dmit(2)(-) = 2-thioxo-1,3-dithiole-4,5-dithiolate) are reported. Gd(3+) ions (S = (7)/(2)) were introduced into the pi-spin network of [Ni(dmit)(2)](-) (S = (1)/(2)) complex as a binuclear supramolecular cation, Gd(2)([18]crown-6)(2)(OH)(2)(CH(3)CN)(2), in which two Gd([18]crown-6) units are bridged with two hydroxide ions. The weak antiferromagnetic interactions between Gd.Gd through hydroxide ions were observed, and [Ni(dmit)(2)](-) formed isolated monomers and dimers in the crystal.