Hexacyanometalates [B-III(CN)(6))](3-) react with Lewis acids [AL](2+) or A(2+) to give either oligonuclear complexes with high-spin ground states [B-III(CN-A(II)L)(6))](9+) or three-dimensional (3D) networks with variable Curie temperature T-C. We report the magnetic properties of (i) an heptanuclear complex [Cr(CN-Ni(tetren)(6)] (ClO4)(9) (tetren is tetraethylenepentamine) exhibiting a S = 15/2 ground state and (ii) a series of hexacyanometalates-based magnets, with T-C ranging from 9K to room temperature. We present the magnetic dichroic properties of some of the 3D materials, in the visible and in the X-ray range.