Syntheses and magnetic properties of Cu(ii)(hfac)2 and Mn(ii)(hfac)2 complexes of 4-pyridyl-substituted thioaminyl radicals

Abstract

Two types of Cu(II)(hfac)₂ and Mn(II)(hfac)₂ complexes of N-(4-pyridylthio)-4-ethoxycarbonyl-2,6-bis(4-chlorophenyl)phenylaminyl (1) and N-(4-pyridylthio)-2,4,6-tris(4-chlorophenyl)phenylaminyl (2) were prepared and their X-ray crystallographic and magnetic studies were performed. Mixtures of Cu(II)(hfac)₂ and 1 and Mn(II)(hfac)₂ and 2 in anhydrous heptane–benzene solution gave 1 : 2 complexes of M(II)(hfac)₂ (M = Cu, Mn) and 1 or 2 in 73–75% yields. For Cu(II)(hfac)₂(1)₂ and Mn(II)(hfac)₂(2)₂ X-ray crystallographic analyses were successfully performed. The magnetic behaviors for the two metal complexes were investigated with a SQUID magnetometer. The analyses for the χ_molTvs. T plots of Cu(II)(hfac)₂(1)₂ were carried out by the numerical diagonalization of the Heisenberg Hamiltonian matrix (4096 × 4096 matrix) for the four repeating units of the complex (12-spin system). The exchange interaction between the copper(II) ion and the thioaminyl radicals is ferromagnetic (J₁/k_B = +28 K) and the interactions between the complexes is antiferromagnetic (J₂/k_B = −13 K). The magnetic behavior of Mn(II)(hfac)₂(2)₂ complexes is well analyzed with the theoretical equation of a 1/2–5/2–1/2 three-spin system taking the intermolecular interaction (θ) into account. The exchange interaction between the Mn(II) ion and the thioaminyl radicals is antiferromagnetic (J/k_B = −4.2 K) and θ = −1.0 K. These magnetic behaviors could be well explained in terms of their crystal structures.