To elucidate the relation between structural and magnetic properties, we have synthesized molecular materials having both Cotton effects and a ferromagnetic long range order. Such optically active 3D molecule-based magnets were rationally designed using the enantioselective template effect of optically active cations, namely A or A [Ru(bpy)(3), ClO4](+) or Delta or Delta [Ru(bpy)(3)ppy](+) (bpy = bipyridine; ppy = phenylpyridine). Such cations are able to template the formation of optically active 3D anionic networks in which transition metal ions (Cr Mn) and (Cr-Ni) are connected by oxalate ligands (ox). Following this strategy, we described the synthesis of {[Ru-(bpy)(3)](2+), ClO4-, [(MnCrIII)-Cr-II(ox)(3)](-)}(n), and {[Ru(bpy)(2)ppy](+), [(MCrIII)-Cr-II(ox)(3)](-)}(n), with M-II = Mn-II, Ni-II in their optically active forms. In these 3D networks, all of the metallic centers have the same configuration, A or A, as the template cation. We have determined the structure of {[Delta Ru(bpy)(3)][ClO4][Delta Mn Delta Cr(ox)(3)]}(n), and {[Lambda Ru(bpy)(2)ppy](+), [Lambda Mn(II)Lambda Cr-III(ox)(3)](-)}(n), by X-ray diffraction studies. These optically active networks show the Cotton effect and long-range ferromagnetic order at low temperatures. The magnetic circular dichroism of {[Ru(bpy)(3)](2+), ClO4-, [(MnCrIII)-Cr-II(ox)(3)](-)}(n), at 2 K is reported.