Molecular (photo)switch: A WCo photomagnetic discrete complex can be prepared through the self-assembly of preformed building blocks. [Co(bik)3][{W(CN)8}3{Co(bik)2} 3]×2 H2O×13 CH3CN (see figure) exhibits a thermally-induced electron-transfer-coupled spin transition between the two states: {{{\rm {\rm Co}}{{{\rm {\rm II}}\hfill \atop {\rm {\rm HS}}\hfill}}}}WV↔{{{\rm {\rm Co}}{{{\rm {\rm III}}\hfill \atop {\rm {\rm LS}}\hfill}}}}W IV. It also shows photomagnetic effects at low temperature.