The molecular structure of TbI₃, DyI₃, HoI₃ and ErI₃ as determined by synchronous gas-phase electron diffraction and mass spectrometric experiment assisted by quantum chemical calculations

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• 作者：Sergey A. Shlykov ; Nina I. Giricheva ; Elena A. Lapykina ; Georgiy V. Girichev ; Heinz Oberhammer
• 关键词：Lanthanide triiodides ; Gas electron diffraction ; Mass spectrometry ; Quantum chemical calculations ; Nuclear dynamics
• 刊名：Journal of Molecular Structure
• 出版年：2010
• 出版时间：20 August 2010
• 年：2010
• 卷：978
• 期：1-3
• 页码：170-177
• 全文大小：471 K

文摘

A first gas electron diffraction study of TbI₃, DyI₃, HoI₃ and ErI₃ has been carried out in combination with mass spectrometric vapour monitoring at 1117(10), 1117(10), 1132(10) and 1102(10) K, respectively. Up to 4 mol. % of dimeric species was observed in addition to the dominating monomeric molecules. The change of the thermal-averaged r_g-configuration parameters of the molecules in the series TbI₃ → ErI₃ reflect the lanthanide contraction. A low value of the shrinkage δ(I…I) even at such a high temperatures may be considered due to vibration effects in molecule whose equilibrium geometric nuclear structure is planar and which correspond to configurationally-averaged 4fⁿ electronic state. B3LYP and МР2 calculations performed in this work with large core potential for lanthanide atoms also resulted in equilibrium geometry of D_3h symmetry. According to the both quantum chemical methods applied the potential function the non-planar vibration is essentially anharmonic, which is therefore to be taken into account to correctly describe nuclear dynamics in molecules such as LnI₃. Different models applied in this study predict the equilibrium distance r_e(Ln–I) to be shorter than the thermal-averaged r_g(Ln–I) distance by 0.002–0.018(1) Å.