Isomeric effects in rod-shaped Au₂₀ clusters: a comparative study on near-infrared photothermal enhancement

In this work, we report two rod-shaped Au₂₀ clusters with distinct core configurations and 14 free electrons, offering an important atomically precise model to probe structure–property relationships. A key finding is that ligand-tuned shortening of Au–Au bonds and a slight structure distortion within the cluster core decisively enhance photothermal conversion efficiency and tune NIR-II emission. The most compact Au₂₀ architecture achieves a photothermal conversion efficiency of 25% and extends emission into the NIR-II window at 1190 nm. These results establish bond-length engineering as a powerful and generalizable design principle for tuning the functional properties of atomically precise metal nanoclusters, opening new avenues for the development of high-performance photothermal and luminescent materials.