Theoretical Analysis of Low Energy Electronic Transitions of Actinide Complexes Including Spin–Orbit Effects

Low‐energy electronic transitions in four actinide complexes are analyzed via complete active space wavefunction calculations including the spin–orbit (SO) interaction. Ground‐ and excited‐state wavefunctions are analyzed via SO natural orbitals. The transitions are characterized via SO natural transition orbitals as well as changes in the electronic entropy of the states involved, changes in the occupation number vectors, and the integrated modulus of the density change. For the complexes [U(N,N′‐bis[(4,4′‐dimethylamino)salicylidene]−1,2‐phenylenediamine)], [CmClMeH(2,2)IAM], and [Es(HOPO)], the calculated photophysical data are considered in comparison with available experimental data. The complex [U(N,N′‐bis[(4,4′‐dimethylamino)salicylidene]‐1,2‐phenylenediamine)] is analyzed with respect to its absorption spectrum. The circularly polarized luminescence (CPL) of the chiral complex [CmClMeH(2,2)IAM] is also modeled and agrees qualitatively with the available experimental CPL spectrum. The study highlights challenges for the computational study of transitions in actinide complexes with strong SO coupling as well as the potential utility of the electronic structure analysis tools applied in this work.