Photoreversible Molecular Motion of stpyCN Coordinated to fac-[Re(CO)₃(NN)]⁺ Complexes

In this work, efficient trans ⇌ cis photoswitchings of 4-(4-cyano)styrylpyridine (stpyCN) coordinated to organometallic bipyridyl tricarbonyl rhenium(I) complexes, fac-[Re(CO)₃(NN)( trans-stpyCN)]⁺, where NN = 2,2'-bipyridine (bpy) or 4,4'-dimethyl-2,2'-bipyridine (dmb), are described. For both complexes, the true trans-to- cis quantum yields determined by ¹H NMR spectroscopy are similar at 313, 334, and 365 nm irradiations (Φ _{trans→ cis}^{true(313-365 nm)} ∼ 0.45), with a small decrease at 404 nm (Φ _{trans→ cis}^{true(404 nm)} ∼ 0.37). The investigated complexes also exhibit significant quantum yields for the reversible cis-to- trans photoreactions (Φ _{cis→ trans}^{(255 nm)} = 0.22). The luminescent properties of these complexes were also analyzed in different media to elucidate a key role of the ³IL_stpyCN state in photophysical and photochemical processes, giving new insights on their intriguing photobehavior.