Static and Dynamic Magnetic Properties of a Co(II)‐Complex with N₂O₂Donor Set – A Theoretical and Experimental Study

Abstract

A representative Co(II) based single ion magnet (SIM) with N 2 O 2 donor set and distorted pseudo-tetrahedral geometry has been synthesized and characterized to study the atomic and electronic structure. DC magnetometry results have been evaluated by means of a phenomenological Hamiltonian approach regarding zero field splitting (ZFS) parameters and compared with results from ab-initio multi-reference CASSCF (complete active space self-consistent field) calculations and qualitative ligand field theory (AILFT). Profound investigation of spin-lattice relaxation with the variation of temperature (from 1.8 to about 8 K) and magnetic field (at 14 different fields from zero up to 1 T) have been performed based on AC magnetometry. Under an applied dc magnetic field, spin-lattice relaxation occurs via a direct process with T 2 temperature dependence due to limited heat transfer at very low temperature and above 5 K relaxation by an Orbach process with an energy barrier of U eff � 80 K dominates.

Kink distortion of the pseudo-S4 axis in pseudotetrahedral [N2O2] bis-chelate cobalt(ii) single-ion magnets leads to increased magnetic anisotropy

“…2,3 A notable group among them are compounds in a (pseudo-)tetrahedral coordination environment due to the relatively large and tunable range of their spin-reversal barrier. Several examples of such cobalt( ii )-based SIMs with [S 4 ], 4 [N 4 ], 5,6 and [N 2 O 2 ] donor sets 7,8 have been reported over the past years. For the magnetic behavior of these SIMs, the single-ion magnetic anisotropy associated with zero-field splitting plays a crucial role.…”