tert-Butyl(tert-butoxy)zinc hydroxides: hybrid models for single-source precursors of ZnO nanocrystals

Abstract

Alkylzinc alkoxides, [RZnOR']4, have received much attention as efficient precursors of ZnO nanocrystals (NCs), and their "Zn4O4 " heterocubane core has been regarded as a "preorganized ZnO". A comprehensive investigation of the synthesis and characterization of a new family of tert-butyl(tert-butoxy)zinc hydroxides, [(tBu)4 Zn4 (μ3-OtBu)x (μ3-OH)4-x], as model single-source precursors of ZnO NCs is reported. The direct reaction between well-defined [tBuZnOH]6 (16) and [tBuZnOtBu]4 (24) in various molar ratios allows the isolation of new mixed cubane aggregates as crystalline solids in a high yield: [(tBu)4 Zn4 (μ3-OtBu)3 (μ3-OH)] (3), [(tBu)4Zn4 (μ3-OtBu)2 (μ3-OH)2] (4), [(tBu)4 Zn4 (μ3-OtBu)(μ3-OH)3] (5). The resulting products were characterized in solution by (1) H NMR and IR spectroscopy, and in the solid state by single-crystal X-ray diffraction. The thermal transformations of 2-5 were monitored by in situ variable-temperature powder X-ray diffraction and thermogravimetric measurements. The investigation showed that the Zn-OH groups appeared to be a desirable feature for the solid-state synthesis of ZnO NCs that significantly decreased the decomposition temperature of crystalline precursors 3-5.

Keywords: alkoxides; hydroxides; zinc; zinc oxide.