To expand the field of new cyanide materials of the 5d elements, we incorporated the [Os(CN)(6)](3-) anion into PB architectures in combination with the Co-II cation. Herein, we report the first example of a photomagnetic PB analog containing Os-III ions. In a similar vein as the prototypical CoFe PB analogs, this compound exhibits a wide variety of properties including Charge Transfer Induced Spin Transition (CTIST), Temperature Induced Excited Spin State Trapping (TIESST), and magnetic ordering.