Investigating Coordination and Reactivity between an Organohalide and Cesium Lead Halide Nanoparticles via Two-Dimensional DOSY and ROSY NMR

Cesium lead halide (CsPbX3, X = Cl, Br, I) nanoparticles have an inorganic core with propensity for ion exchange that is surrounded by a labile organic capping shell that facilitates ligand exchange, two characteristics that are important for interfacial reactions and heterogeneous catalysis. This study followed a model reaction between 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 coefficients (D) and relaxation times (T1) change measured in DOSY and ROSY revealed fast 2-Br coordination, then reaction with the CsPbBr3-xIx , resulting both a bromine rich inorganic product, and both an elimination (2-dodecenoic acid, 2-DDAc) and 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.