Ion-molecular equilibria in lanthanide triiodide vapors and formation enthalpies of LnI4− and Ln2I7− ions (Ln = La, Ce, Pr, Gd, Tb, Tm, and Lu)

• Published in: International journal of mass spectrometry Vol. 435; pp. 188 - 194
• Main Authors: Motalov, V.B., Dunaev, A.M., Kudin, L.S., Butman, M.F., Krämer, K.W.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-01-2019
• Subjects: Formation enthalpy; Ion-molecular equilibrium; Knudsen effusion mass spectrometry; Lanthanide triiodides; Negative ions; Lanthanide triiodides; Negative ions; Formation enthalpy; Ion-molecular equilibrium; Knudsen effusion mass spectrometry
• ISSN: 1387-3806; 1873-2798
• DOI: 10.1016/j.ijms.2018.11.012

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•Pure lanthanide triiodides and their mixtures were studied by KEMS.•LnI4– and Ln2I7– ions were identified as charged vapor constituents.•Enthalpies of ion-molecular reactions were calculated.•Standard formation enthalpies of ions were determined.
Ion-molecular equilibria LaI4– + LnI3 = LnI4– + LaI3, Ln2I7– = LnI3,cr + LnI4– (Ln = Ce, Pr, Gd, Tb, Tm, and Lu), and 3LaBr4– + 4LaI3 = 3LaI4– + 4LaBr3 in vapors over the LaI3-CeI3-PrI3-GdI3, LaI3-GdI3-TbI3-TmI3, and LaI3-LaBr3 mixtures and the pure lanthanide triiodides were studied in the temperature range of 700–1050 K by Knudsen effusion mass spectrometry. The equilibrium constants were measured and the reaction enthalpies were calculated by the techniques of the second and third laws of thermodynamics. The standard formation enthalpies of ions, ΔfH°(298.15 K) (in kJ mol–1), were determined to be –832 ± 21 (LaI4–), –834 ± 23 (CeI4–), –834 ± 25 (PrI4–), –812 ± 24 (GdI4–), –813 ± 25 (TbI4–), –817 ± 23 (TmI4–), –806 ± 25 (LuI4–), –1399 ± 45 (La2I7–), –1402 ± 46 (Ce2I7–), –1417 ± 47 (Pr2I7–), –1356 ± 47 (Gd2I7–), –1365 ± 47 (Tb2I7–), –1366 ± 46 (Tm2I7–), and –1322 ± 47 (Lu2I7–).