Rational Design of a Confacial Pentaoctahedron: Anisotropic Exchange in a Linear ZnIIFeIIIFeIIIFeIIIZnII Complex
Stephan Walleck, Mihail Atanasov, Jugen Schnack, Eckhard Bill, Anja Stammler, Hatmut Bogge, Thorstem
Chemistry A European Journal
The first confacial pentaoctahedron comprised of transition metal ions namely ZnIIFeIIIAFeIIIBFeIIIAZnII has been synthesized by using a dinucleating nonadentate ligand. The face-sharing bridging mode enforces short ZnII⋅⋅⋅FeIIIA and FeIIIA⋅⋅⋅FeIIIB distances of 2.83 and 2.72 Å, respectively. Ab-initio CASSCF/NEVPT2 calculations provide significant negative zero-field splittings for FeIIIA and FeIIIB with |DA|>|DB| with the main component along the C3 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 Jxy=+0.37, Jz=−0.32, DA=−1.21, EA=−0.24, DB=−0.35, and EB=−0.01 cm−1 supported by simulations of high-field magnetic Mössbauer spectra recorded at 2 K. The weak but ferromagnetic FeIIIAFeIIIB interaction arises from the small bridging angle of 84.8° being at the switch from anti- to ferromagnetic for the face-sharing bridging mode.
five face-sharing octahedra – a confacial pentaoctahedron