Two monometallic and three bimetallic ruthenium acetonitrile (RuMeCN) complexes are presented and fully characterized. All of them are built from the same skeleton [FTRu(bpy)(MeCN)]$^{2+}$, in which FT is a fluorenyl-substituted terpyridine ligand and bpy is the 2,2′-bipyridine. The crystal structure of [FTRu(bpy)(MeCN)](PF$_6$)$_2$ is presented. A careful spectroscopic analysis allows establishing that these 5 RuMeCN complexes can be identified as the product of the photoreaction of 5 related RuNO complexes, investigated as efficient nitric oxide (NO) donors. Based on this set of complexes, the mechanism of the NO photorelease of the bimetallic complexes has been established through a complete investigation under irradiations performed at 365, 400, 455, and 490 nm wavelength. A two-step (A → B → C) kinetic model specially designed for this purpose provides a good description of the mechanism, with quantum yields of photorelease in the range 0.001–0.029, depending on the irradiation wavelength. In the first step of release, the quantum yields (ϕ$_{AB}$) are always found to be larger than those of the second step (ϕ$_{BC}$), at any irradiation wavelengths.