Understanding solid-state photoswitching in [Re(OMe2-bpy)(CO)3(η1-NO2)] crystals via in situ photocrystallography

Abstract

Single-crystal-to-single-crystal nitro → nitrito isomerism is reported for the novel rhenium(I)-bipyridine complex [Re(OMe₂-bpy)(CO)₃(η¹-NO₂)], achieving a maximum conversion of 66% to a photoinduced nitrito-(η¹-NO) isomer under continuous illumination. The 3D X-ray structure of the photoinduced isomer is determined by steady-state and psuedo-steady-state photocrystallographic methods, providing insight into the structural changes required to accommodate photoswitching. Photocrystallographic kinetic studies follow the progress of photoswitching with time, determining a reaction rate constant of k = 0.38(2) min⁻¹ at 150 K. Linkage isomerism is fully-reversible on warming, and pseudo-steady-state experiments confirm that the photoexcited state is retained, at measurable occupancy, up to a temperature of 240 K. These results confirm the validity of combining photoactive linkage isomer and Re(I) photocatalyst chemistries, and the detailed determination of the photoexcited state structure will facilitate the future design of new photoactive Re(I) crystals for a range of applications.