Application of Water-Soluble Titanium Complexes as Precursors for Synthesis of Titanium-Containing Oxides via Aqueous Solution Processes

The growing significance of nanocrystalline inorganic functional materials in the fields of catalysis, electronics, and energy conversion together with the increasing demand of the society for safer, softer, and "greener" technologies has drawn considerable attention of the researchers toward water-based solution processes for synthesis of such materials. In this respect complex oxides, containing d(0)-transition metals, such as Ti, Nb, Ta, or Si represent an outstanding challenge. for materials chemists due to the extremely narrow range or almost complete absence of suitable precursor compounds compatible with aqueous systems. In the recent 10 years, a remarkable progress has been achieved in the development of new water-soluble complexes of titanium and considerable experience was accumulated in the application of these compounds for synthesis of nanocrystalline titanium-containing materials. The essential knowledge of coordination chemistry of such water-soluble titanium complexes is reviewed in this work, which succeeded to identify the key structural features responsible for stability of the compounds against hydrolysis and to provide guidelines for synthesis of these complexes. Finally, an extensive overview of highly selective aqueous solution based synthesis of TiO2 polymorphs as well as complex oxide materials with the help of the novel water-soluble titanium complexes is provided.