Scandium triiodide, also known as scandium iodide, is an
inorganic compound with the formula ScI
3 and is classified as a lanthanide
iodide
An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. In everyday life, iodide is most commonly encountered as a component of iodized salt, which many governments mandate. Worldwide, iodine de ...
. This salt is a yellowish powder.
[Haeberle, N., 1973, Preparation of highly pure lanthanide iodides, Technisch-Wissenschaftliche Abhandlungen der Osram-Gesellschaft, v. 11, p. 285] It is used in metal halide lamps together with similar compounds, such as caesium iodide, because of their ability to maximize emission of UV and to prolong bulb life. The maximized UV emission can be tuned to a range that can initiate
photopolymer
A photopolymer or light-activated resin is a polymer that changes its properties when exposed to light, often in the ultraviolet or visible region of the electromagnetic spectrum. These changes are often manifested structurally, for example harden ...
izations.
Scandium triiodide adopts a structure similar to that of
iron trichloride
Iron(III) chloride is the inorganic compound with the formula . Also called ferric chloride, it is a common compound of iron in the +3 oxidation state. The anhydrous compound is a crystalline solid with a melting point of 307.6 °C. The colo ...
(FeCl
3), crystallizing into a rhombohedral lattice. Scandium has a coordination number of 6, while iodine has a coordination number of 3 and is trigonal pyramidal.
[Men'kov, A. A., Komissarova, L. N., 1964, X-ray study of scandium iodide, Zhurnal Neorganicheskoi Khimii, v. 9, p. 766]
The purest scandium triiodide is obtained through direct reaction of the elements:
[
: 2 Sc + 3 I2 → 2 ScI3
Alternatively, but less effectively, one can produce anhydrous scandium triiodide by dehydrating ScI3(H2O)6.
]
Further information
*Tomasz Mioduski, Cezary Gumiski, and Dewen Zeng "Rare Earth Metal Iodides and Bromides in Water and Aqueous Systems. Part 1. Iodides" Journal of Physical and Chemical Reference Data 2012, vol. 41, 013104-1 to 013104-63.
References
{{Iodides
Scandium compounds
Iodides
Metal halides