Bond lengths of 4f1 and 5d1 states of Ce3+ hexahalides

Ligand and solvent effects on the bond length shift experienced by complexes of lanthanide ions upon 4f -> 5d excitation, addressed by means of ab initio embedded cluster calculations, are presented on the clusters (CeF6)(3-), (CeCl6)(3-), and (CeBr6)(3-) in solid elpasolites, in liquid acetonitrile and in vacuo. Previous predictions of bond length shortening upon 4f -> 5d((t2g)) excitation seem to be general and, in particular, chloride and bromide compounds in liquid solution are predicted to be good candidates for excited-state EXAFS measurements of the distortion signs. A quantitative analysis of contributions to the bond length shifts is presented, which shows the importance of ligand field effects and points out insufficiencies in the Judd-Morrison model proposed to account for 4f -> 5d transitions in crystals. (c) 2004 Elsevier Inc. All rights reserved.