The conditions for the photogeneration of NO linkage isomers at room temperature are studied. By pulsed laser irradiation in the blue spectral range the long-lived Ru-ON isomer can be generated at room temperature, which is crucial for potential applications such as holography and data storage. Using static and time-resolved spectroscopy (UV/Vis and IR) we give evidence that the liftime of the Ru-(η 2-(NO)) isomer is a decisive parameter for the formation of Ru-ON isomer at high temperature due to a two-step isomerization mechanism Ru-NO → Ru-(η 2-(NO)) → Ru-ON. Furthermore, we report the low temperature structures for each isomer, which were revealed by photocrystallography.