Modulated assembly and structural diversity of heterometallic Sn-Ti oxo clusters from inorganic tin precursors.

Through modulating the multidentate ligands, solvent environments, and inorganic tin precursors during the synthesis processes, we have successfully prepared a series of unprecedented heterometallic Sn-Ti oxo clusters with structural diversity and different physiochemical attributes. Initially, two Sn6Ti10 clusters were synthesized using trimethylolpropane as a structure-oriented ligand and SnCl·5HO as a tin source. Then, when a larger pentadentate ligand di(trimethylolpropane) was used instead of trimethylolpropane and aprotic acetonitrile solvent was introduced into the reaction system, four low-nuclearity Sn-Ti oxo clusters were discovered, including two Sn1Ti1, one Sn2Ti2 and one Sn2Ti6. Finally, two mixed-valence state clusters, SnII4SnIV2TiIV14 and SnII4SnIV4TiIV20, were obtained by transforming the tin precursor from SnCl·5HO to SnCl·2HO and adjusting the acetonitrile solution with trace acetic acid/formic acid. Sn8Ti20 is the highest-nuclearity heterometallic Sn-Ti oxo cluster to date. Moreover, comparative electrocatalytic CO reduction experiments were carried out, and it was concluded that the Sn8Ti20-decorated electrode showed the most satisfactory performance due to the influence of mixed-valence states of the Sn atoms and the charging effects provided by 20 Ti ions. This study presents important guiding significance for the design, synthesis and application optimization of functional heterometallic nanoclusters.