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 a structure-oriented ligand and SnCl₄·5H₂O 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, Sn^II₄Sn^IV₂Ti^IV₁₄ and Sn^II₄Sn^IV₄Ti^IV₂₀, were obtained by transforming the tin precursor from SnCl₄·5H₂O to SnCl₂·2H₂O 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 CO₂ 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 Ti⁴⁺ ions. This study presents important guiding significance for the design, synthesis and application optimization of functional heterometallic nanoclusters.