Molecular structure of TmCl₃ by synchronous electron diffraction and mass spectrometric experiment

Abstract

The molecular structure of lanthanide trihalides has been discussed since 1959, when the first electron diffraction data were obtained for LaHal₃ and NdHal₃ [1]. The diffraction pattern was initially interpreted [1] with the assumption that the molecules have a planar structure. Later, more elaborate procedures for recording and interpreting electron diffractograms led to structure determination for three lanthanide trifluorides (PrF₃, GdF₃, HoF₃) [2], six trichlorides (LaCl₃, PrCl₃, GdCl₃, TbCl₃, H0Cl₃, LuCl₃) [3-7], three tribromides (LaBr₃, GdBr₃, LuBr₃) [8, 9], and five triiodides (Prl₃, Ndl₃, Gdl₃, Lul₃ [10], Cel₃ [11]). It was found that all of these molecules have an effective nonplanar configuration. An attempt was made to trace the tendencies of bond angle variation for the equilibrium configuration in the series LaHal₃-LuHal₃ and LnF₃-LnI₃ [12]. This molecular structure study performed on TmCl₃ is aimed to clarify details of molecular structure variation in the second half of the LnCl₃ series.