All Alkoxide Sol–Gel Route to CoO-TiO2 Nano-Powders

The molecular alkoxide, ErNb₂(OPrⁱ)₁₃ was prepared by metathesis with 2KNb(OPrⁱ)₆, KOPrⁱ and ErCl₃, and structurally determined by single-crystal X-ray diffraction techniques. Each molecule contains a central Er³⁺-ion coordinated by six OPrⁱ groups of which one is terminal. On each side is an Nb⁵⁺-ion coordinated by six OPrⁱ groups placed, one via a double alkoxo-bridge and the other via a triple alkoxo-bridge. It is isostructural with LaNb₂(OPrⁱ)₁₃, in spite of the large difference in ionic radius between Er³⁺ and La³⁺ (16%). The compound was characterized by its IR- and UV-vis-NIR-spectroscopic fine structures, and found to be structurally intact in hexane:isopropanol solution.