Effect of the distant substituent on the slow magnetic relaxation of the mononuclear Co(ii) complex with pincer-type ligands

Abstract

A hexacoordinated complex [Co(pydm)₂](mdnbz)₂ from the family of pincer complexes was prepared and structurally characterized. The complex behaves as an S = 3/2 spin system with a considerable zero-field splitting parameter D/hc ∼ +50 cm⁻¹. The AC susceptibility measurements show a slow magnetic relaxation with three relaxation channels: at the low-frequency (LF), intermediate-frequency (IF) and high-frequency (HF) domains. At T = 2.0 K and an external field B_DC = 0.25 T, the relaxation times of the individual modes are τ(LF) = 282 ms, τ(IF) = 3.1 ms, and τ(HF) = 0.16 ms, and the mole fractions of the slowly relaxing species are x(LF) = 0.19, x(IF) = 0.45, and x(HF) = 0.37. A comparison with the analogous complex [Co(pydm)₂](dnbz)₂ possessing a demethylated counter anion and identical metal cation shows that even small modifications in the composition of SIMs are no longer underestimated for the slow magnetic relaxation.