Studying manganese carbonyl photochemistry in a permanently porous metal-organic framework

Mn(diimine)(CO)(3)X (X = halide) complexes are critical components of chromophores, photo- and electrocatalysts, and photoactive CO-releasing molecules (photoCORMs). While these entities have been incorporated into metal-organic frameworks (MOFs), a detailed understanding of the photochemical and chemical processes that occur in a permanently porous support is lacking. Here we site-isolate and study the photochemistry of a Mn(diimine)(CO)(3)Br moiety anchored within a permanently porous MOF support, allowing for not only the photo-liberation of CO from the metal but also its escape from the MOF crystals. In addition, the high crystallinity and structural flexibility of the MOF allows crystallographic snapshots of the photolysis products to be obtained. We report these photo-crystallographic studies in the presence of coordinating solvents, THF and acetonitrile, showing the changing coordination environment of the Mn species as CO loss proceeds. Using time resolved experiments, we report complementary spectroscopic studies of the photolysis chemistry and characterize the final photolysis product as a possible Mn(ii) entity. These studies inform the chemistry that occurs in MOF-based photoCORMs and where these moieties are employed as catalysts.

Automated summary

We investigated the photochemical and chemical processes of Mn(diimine)(CO)(3)X (X = halide) complexes in permanently porous metal-organic frameworks (MOFs). We observed the photo-liberation of CO from the metal and its escape from the MOF crystals. Crystallographic snapshots of the photolysis products were obtained due to the high crystallinity and structural flexibility of the MOF. Time resolved experiments revealed complementary spectroscopic studies and characterized the final photolysis product as a possible Mn(ii) entity. These findings provide insights into the chemistry of MOF-based photoCORMs and catalysts.