Intensity calculations on hypersensitive f-f transitions in nine-coordinate lanthanide systems of trigonal symmetry

Abstract

Dipole strength and intensity calculations are reported for a series of 4f-4f electronic transitions in Pr³⁺, Eu³⁺, Tb³⁺ and Ho³⁺ complexes of trigonal symmetry. These calculations are based on crystal field and intensity models which include both multipole-point charge and multipole-induced dipole lanthanide-ligand interactions. The ligand parameters appearing in these models are atomic charges, atomic dipolar polarizabilities and atomic positional coordinates. Term-to-term transitions are characterized according to (1) their magnetic dipole versus electric dipole character, (2) the mechanism principally responsible for their electric dipole strength and (3) their sensitivity to ligand structure. Where it is possible to make comparisons, the calculated intensity results for term-to-term transitions are in excellent qualitative and good semiquantitative agreement with experiment. The calculations reported here represent the first full scale computational test of a 4f-4f intensity model which includes both the Judd-Ofelt static coupling and Mason, Peacock and Stewart dynamic coupling (or ligand polarization) contributions to the electric dipole strengths of 4f-4f transitions in noncentrosymmetric lanthanide complexes.