Electronic Structure and Molecular Properties of the Heptacyanorhenate [Re(CN)₇]^3- and [Re(CN)₇]^4- Complexes

Abstract

We report scalar relativistic and Dirac scattered wave (DSW) calculations on the heptacyanorhenate [Re(CN)7](3-) and Re(CN)7(4-) complexes. Both the ground and lowest excited states of each complex split by spin-orbit interaction by about 0.3 eV. The calculated molecular electronegativities chi indicate that the open-shell complex is less reactive than the closed-shell complex, in agreement with experimental observations. The calculations indicate that the ground state spin density is highly anisotropic and that spin-orbit effects are responsible for the magnetic anisotropy of the molecular g tensor of the Re(CN)7(3-) complex. The calculated optical electronic transitions for both complexes with a polarizable continuum model using a time-dependent density functional (TDDFT)/B3LYP formalism are in reasonable agreement with those observed in the absorption spectrum.

Magnetic anisotropy of transition metal and lanthanide ions in pentagonal bipyramidal geometry

“…26 For the Re IV homologue, g ⊥ = 1.759 and g ‖ = 3.66 have been found. 27,28 Somewhat less anisotropic g was observed for a PBP W III derivative with mixed carbonyl/cyanide ligand set, cis -[W(CN) 5 (CO) 2 ] 2− , but EPR was recorded in solution. 29…”

Origin of Dissimilar Single-Molecule Magnet Behavior of Three MnII2MoIIIComplexes Based on [MoIII(CN)7]4–Heptacyanomolybdate: Interplay of MoIII–CN–MnIIAnisotropic Exchange Interactions

“…Due to a very strong ligand field, all orbitally degenerate 4d and 5d complexes have a low spin of S = 1 / 2 with no ZFS effect, requiring S > 1 / 2 . Examples are given by [Mo III (CN) 7 ] 4– and [Re IV (CN) 7 ] 3– pentagonal-bipyramidal complexes, [Ru III (CN) 6 ] 3– and [Os III (CN) 6 ] 3– octahedral complexes, and some trigonal-pyramidal Mo and W complexes . It is important to note that isolated complexes of this type cannot exhibit single-ion magnet behavior due to the absence of the ZFS anisotropy for the S = 1 / 2 spin.…”

Advances in bonding and properties of inorganic systems from relativistic calculations in Latin America

“…Also, spin‐orbit effects are responsible for the magnetic anisotropy of the [Re(CN) 7 ] 3− complex. Consequently, the incorporation of relativistic corrections are essential for a good description of optical electronic transitions …”