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

Abstract

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 structure-oriented ligand and SnCl4·5H2O as tin source. Then, when the larger pentadentate ligand di(trimethylolpropane) was used instead of trimethylolpropane and aprotic acetonitrile solvent was introduced in the reaction system, four low-nuclearity Sn-Ti oxo clusters were discovered, including two Sn1Ti1, one Sn2Ti2 and one Sn2Ti6. Finally, two mixed-valence states clusters, SnII4SnIV2TiIV14 and SnII4SnIV4TiIV20, were obtained by transforming the tin precursor from SnCl4·5H2O to SnCl2·2H2O and adjusting acetonitrile solution with trace acetic acid/formic acid. Thereinto, Sn8Ti20 is the highest-nuclearity heterometallic Sn-Ti oxo cluster to date. Moreover, comparative electrocatalytic CO2 reduction experiments were carried out, and it was concluded that Sn8Ti20 decorated electrode showed the most satisfactory performance due to the influence of mixed-valence states of Sn atoms and the charging effects provided by 20 Ti4+ ions. This study presents important guiding significance for the design, synthesis and application optimization of functional heterometallic nanoclusters.