Electronic structure and magnetic properties of naphthalene- and stilbene-diimide-bridged diuranium(V) complexes: a theoretical study.

Abstract

The magnetic exchange coupling between two diuranium(V) ions exhibiting the 5f1-5f1 configuration in diimide-bridged complexes [Cp3UV]2(μ-L) (L = stilbene-, naphthalene-diimide) has been investigated theoretically using relativistic ZORA/DFT calculations. Using two different hybrid PBE0 and B3LYP functionals, combined with the broken symmetry (BS) approach, we found that the BS states of both naphthalene and stilbene complexes have lower energy than the corresponding high-spin (HS) triplet ones. The B3LYP/BS estimated exchange coupling J constants (- 16.1 vs. - 9.0cm-1 respectively for the naphthalene and stilbene complexes) corroborate well with those obtained previously for other pentavalent diuranium(V) diimide-bridged systems. The computed J value is found to be sensitive to π-network linking the two magnetic U(V) centers. The natural spin density distributions and molecular orbital analyses explain well the antiferromagnetic character of these compounds and clarify the crucial role of the π aromatic spacer in promoting spin polarization and delocalization favoring the magnetic coupling. Furthermore, the effective involvement of the 6d/5f metal orbitals in metal-ligand bonding plays an important role for the magnetic communication between the two active U(V) 5f electrons. Graphical abstract.