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 Delta or Lambda [Ru(bpy)3, ClO4](+) or Delta or Lambda [Ru(bpy)3ppy](+) (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(-), [Mn(II)Cr(III)(ox)3](-))n and ([Ru(bpy)2ppy](+), [M(II)Cr(III)(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, Delta or Lambda, as the template cation. We have determined the structure of ([DeltaRu(bpy)3][ClO4][DeltaMnDeltaCr(ox)3])n and ([LambdaRu(bpy)2ppy](+), [LambdaMn(II)LambdaCr(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(-), [Mn(II)Cr(III)(ox)3](-))n at 2 K is reported.