Characterisation of geometric isomers of europium chlorides with 2,2′-bipyridine based on X-ray diffraction, luminescence and quantum chemical data

Abstract

A low-temperature high-resolution luminescence study of the EuCl₃bpy₂(H₂O) _n isomers has been carried out. The Eu³⁺ luminescence spectra of all geometric isomers were recorded over the spectral range which includes transitions from the ⁵D₀ excited state to the ⁷F_0–4 ground state manifolds and from the ⁵D₁ excited state to the ⁷F_0–2 ground state manifolds. Analysis of the Eu³⁺ transitions observed in the luminescence spectra shows that the Eu³⁺ ion occupies a spectroscopic site symmetry that approaches a C_{2 v} symmetry with distortion towards C₂ or lower symmetry. The structural features and distortions of the Eu³⁺ coordination polyhedron in these geometric isomers were described based on the X-ray crystallographic data as well. The splitting patterns and energies found of the ⁷F_0–4 manifolds have been used to calculate the crystal field parameters (CFPs) of the Eu³⁺ ions in these geometric isomers. In addition the mutual influence of the ligands as well as the relative stability of geometric isomers of the [EuCl₃bpy₂(H₂O)₂]⁺ cation in the gas phase was analyzed within DFT calculations.

Keywords:

• luminescence
• crystal field
• lanthanide
• trans effect
• optical spectroscopy

Acknowledgements

The authors thank Professor V.F. Zolin for providing the program for CFP calculation and Professor M.F. Ried for helpful discussions. This study was financially supported by the Russian Foundation for Basic Research (Grants no. 09-03-00603, 09-03-12065, 10-03-00898) and the Foundation of the President of the Russian Federation (Federal Program for the Support of Young Doctors, Grant MD-237.2010.3 and MK-6026.2008.9).

Notes

Supplementary material can be viewed online.