Atomically Precise Multimetallic Semiconductive Nanoclusters with Optical Limiting Effects.

For the first time, multinuclear noble-metal clusters have been successfully stabilized by Ti-oxo clusters. Two unprecedented Ag6 @Ti16 -oxo nanoclusters with precise atomic structures were prepared and characterized. The octahedral Ag6 core has strong Ag-Ag bonds (ca. 2.7 Å), and is further stabilized by direct Ag-O-Ti coordination interactions. Moreover, as a result of different acidic/redox conditions in synthesis, the Ag6 core can adopt diverse geometric configurations inside the Ti16 -O shell. Correspondingly, structural differences greatly influence their optical limiting effects. The transmittance reduction activity of the clusters towards 532 nm laser shows a nearly linear concentration dependence, and can be optimized up to about 43 %. This work not only opens a new direction for multimetallic semiconductive nanoclusters with interesting optical properties, but also provides molecular models for important noble-metal/TiO2 heterogeneous materials.