Bond lengths of image and image states of image hexahalides

Ligand and solvent effects on the bond length shift experienced by complexes of lanthanide ions upon image excitation, addressed by means of ab initio embedded cluster calculations, are presented on the clusters (image, image, and image in solid elpasolites, in liquid acetonitrile and in vacuo. Previous predictions of bond length shortening upon image 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 image transitions in crystals.