Hexacyanometalates [BIII(CN)6)]3- react with Lewis acids [AL]2+or A2+to give either oligonuclear complexes with high-spin ground states [BIII(CN-AIIL)6)]9+or three-dimensional (3D) networks with variable Curie temperature TC. We report the magnetic properties of (i) an heptanuclenr 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 TCranging 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.