Observing Coordination and Reactivity between an Organohalide and Cesium Lead Halide Nanoparticles via DOSY and ROSY NMR

Cesium lead halide (CsPbX3, X = Cl, Br, I) nanoparticles have an inorganic core with the propensity for ion exchange that is surrounded by a labile ligand capping shell which facilitates ligand exchange, two characteristics that are important for chemical reactions and heterogeneous catalysis. This study followed a model reaction between the organohalide 2-Bromododecanoic Acid (2-Br) and four different oleic acid (OAc), oleyl amine (OAm) capped CsPbBr3-xIx in-situ with 2D diffusion ordered nuclear magnetic resonance spectroscopy (DOSY) and relaxation ordered spectroscopy (ROSY). The observed diffusion coefficient (D) and relaxation time (T1) changes measured in DOSY and ROSY, respectively, indicated 2-Br binding and reactions at the CsPbBr3-xIx interface, forming a more bromine rich inorganic product, and both an elimination (2-dodecenoic acid, 2-DDAc), or halide exchanged organic product (2-Iodododecanoic acid, 2-I). Photoluminescence spectroscopy was also used to monitor the reactions. The results indicate that the reactions proceed without the need for any external light activation, however when photoactivated, a preference towards the 2-I formation was observed.