Graphene-Oxide-Mediated Photothermal Ring-Closing Metathesis: A Gateway for Organelle Imaging Probes.

Photothermal effect using mild light irradiation has emerged as an interesting strategy in modern synthetic chemistry due to its rapid reaction with high selectivity and spatiotemporal control over conventional heating. However, applying photothermal conversion to carry out organic reactions efficiently using carbon nanomaterials remained largely uncharted. To address this, herein, we report for the first time, graphene oxide (GO) as the photothermal agent to perform ring-closing metathesis (RCM) under 940 nm NIR LED light, as well as solar simulator and natural sunlight, using Grubbs-II catalyst to rapidly synthesize dihydro-pyrroles in high yield with excellent GO recyclability. Theoretical calculation unveiled that this photothermal RCM efficiency originated from the cumulative synergy between substrate-GO absorption energy, activation barrier, and nonradiative relaxation rate which emerged as the predominant contributor for the overall reaction outcome. The RCM product can be further functionalized through Pd-catalyzed Heck coupling to forge various fluorophores for efficient imaging of endoplasmic reticulum (ER), mitochondria, and Golgi apparatus (GA) in HCT-116 colon cancer cells. This GO-mediated photothermal RCM can open a new direction toward synthesizing complex organic molecules with ease and high yield for biomedical applications.