Two new hexanuclear octahedral cyanido-bridged clusters, {[Cd-II(bpy)(2)](4)[W-IV(CN)(8)](2)}center dot 10H(2)O (Cd4W2) and {[Cd-II(bpy)(2)](4)[Mo-IV(CN)(8)](2)}center dot 10H(2)O (Cd4Mo2), have been obtained and characterized structurally and photomagnetically. Both compounds show a very rare and reversible single-crystal-to-single-crystal transformation upon dehydration accompanied by marked color changes in the case of Cd4W2. Moreover, irradiation of Cd4Mo2 using 436 nm light induces a reversible photomagnetic effect due to the LIESST-like singlet-triplet transition at the Mo-IV center. Analogous photomagnetic experiments for Cd4W2 did not lead to any significant change of its magnetic moment.