Molecular transformations for direct synthesis of thorium dioxide films

New Th(IV) complexes with high volatility were synthesized and applied as molecular single-source precursors for chemical vapor deposition (CVD) of ThO${}_2$ thin films. The change in the steric profile of alkoxide ligands and concomitant reduction in the molecular weight of [Th(L)${}_2$(OR)${}_2$] (1-OR, R=iso-propyl (1-O${}^i$Pr) or tert-butyl (1-O${}^t$Bu), L=N-(4,4,4-trifluorobut-1-ene-3-one)-methoxyethylamide)) had a profound effect on the vapor pressure (at 10${}^{-5}$ mbar) evident in the drop in sublimation temperature to 100 °C for the iso-propoxide derivative against 130 °C observed for the tert-(1-O${}^t$Bu). Hirshfeld surface analysis of both complexes showed different degrees of intermolecular H⋅⋅⋅F interactions responsible for the observed differences in the volatilities of the two complexes. Both mixed-ligand compounds (1-O${}^i$Pr, 1-O${}^t$Bu) were applied in the CVD process to deposit thorium oxide thin films without any carrier or reactive gas that verified their suitability as single-source precursors to ThO${}_2$ coatings. Thin films of ThO${}_2$ were grown at 500 °C and 600 °C on Si/SiO${}_2$ substrates, which showed presence of C, N, and F presumably originating from the incorporation of ligand fragments in the growing CVD deposits. Subsequent calcination of CVD-grown ThO${}_2$ films at 800 °C in air led to phase pure ThO${}_2$ coatings with uniform morphology. (© 2024 The Author(s). Zeitschrift für anorganische und allgemeine Chemie published by Wiley-VCH GmbH)