| Institution: | 1. Institute of Inorganic Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius Väg 16 C, 10691 Stockholm, Sweden;2. Institute of Inorganic Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany;3. Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany;4. Institute of Theoretical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany;5. Max-Planck-Institute for Solid-State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany |
| Abstract: | The admixture of CeO2, Ce, CeCl3, and MoO3 with an excess of LiCl as flux in evacuated silica ampules leads to large black single crystals as well as a black microcrystalline powder of Ce3Cl3MoO6] after tempering at 850 °C for three days. The title compound crystallizes in the hexagonal space group P63/m (a=934.93(4), c=538.86(2) pm) with two formula units per unit cell. The crystal structure consists of rather unusual trigonal-prismatic MoO6]6− units besides Ce3+ ions in a tetra-capped trigonal-prismatic coordination, formed by four Cl− and six O2− ions. The black color is related to an optical band gap of 1.35(2) eV, which was determined by diffuse reflectance spectroscopy and confirmed by theoretical calculations. The low band gap between the 4f1 state of cerium (HOMO) and the 5d0 state of molybdenum (LUMO) gave rise to the idea of electronic excitation between these two states by IR irradiation, creating a drop in the resistivity of the material, which was detected by appropriate measurements. |
