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The thallium halides include monohalides, where thallium has oxidation state +1, trihalides where thallium generally has oxidation state +3 and some intermediate halides with mixed +1 and +3 oxidation states. These materials find use in specialized optical settings, such as focusing elements in research spectrophotometers. Compared to the more common zinc selenide-based optics, materials such as thallium bromoiodide enable transmission at longer wavelengths. In the infrared, this allows for measurements as low as 350 cm−1 (28 µm), whereas zinc selenide is opaque by 21.5 µm and ZnSe optics are generally only usable to 650 cm−1 (15 µm). == Monohalides == The monohalides all contain thallium with oxidation state +1. Parallels can be drawn between the thallium(I) halides and their corresponding silver salts, for example thallium(I) chloride and bromide are light sensitive and thallium(I) fluoride is more soluble in water than the chloride and bromide. ;Thallium(I) fluoride :TlF is a white crystalline solid, with a mp of 322 °C. It is readily soluble in water unlike the other Tl(I) halides. The normal room temperature form has a similar structure to α-PbO which has a distorted rock salt structure with essentially five coordinate thallium, the sixth fluoride ion is at 370 pm. At 62 °C it transforms to a tetragonal structure. This structure is unchanged up to pressure of 40 GPa.〔U.Haussermann, P.Berastegui, S.Carlson, J.Haines, and J.Leger ''Angewandte Chemie'', 31, pp. 4760 (2001)〕:The room temperature structure has been explained in terms of interaction between Tl 6s and the F 2p states producing strongly antibonding Tl-F states. The structure distorts to minimise these unfavourable covalent interactions.〔A-V Mudring Eur. J. Inorg. Chem. 2007, 882〕 ;Thallium(I) chloride :TlCl is a light sensitive, white crystalline solid, mp 430 °C. The crystal structure is the same as CsCl. ;Thallium(I) bromide :TlBr is a light sensitive, pale yellow crystalline solid, mp 460 °C. The crystal structure is the same as CsCl. ;Thallium(I) iodide :At room temperature TlI is a yellow crystalline solid, mp 442 °C. The crystal structure is a distorted rock salt structure known as the β-TlI structure. At higher temperatures the colour changes to red with a structure the same as CsCl.抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Thallium halides」の詳細全文を読む スポンサード リンク
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