Rational Design of a Confacial Pentaoctahedron: Anisotropic Exchange in a Linear ZnII FeIII FeIII FeIII ZnII Complex.

Abstract

The first confacial pentaoctahedron comprised of transition metal ions namely ZnIIFeIII AFeIII BFeIII AZnII has been synthesized by using a dinucleating nonadentate ligand. The face‐sharing bridging mode enforces short ZnII⋅⋅⋅FeIII A and FeIII A⋅⋅⋅FeIII B distances of 2.83 and 2.72 Å, respectively. Ab‐initio CASSCF/NEVPT2 calculations provide significant negative zero‐field splittings for FeIII A and FeIII B with |D A|>|D B| with the main component along the C 3 axis. Hence, a spin‐Hamiltonian comprised of anisotropic exchange, zero‐field, and Zeeman term was employed. This allowed by following the boundary conditions from the theoretical results the simulation in a theory‐guided parameter determination with J xy=+0.37, J z=−0.32, D A=−1.21, E A=−0.24, D B=−0.35, and E B=−0.01 cm−1 supported by simulations of high‐field magnetic Mössbauer spectra recorded at 2 K. The weak but ferromagnetic FeIII AFeIII B interaction arises from the small bridging angle of 84.8° being at the switch from anti‐ to ferromagnetic for the face‐sharing bridging mode.