Expanding the 3d-4f heterometallic chemistry of the (py)2CO and pyCOpyCOpy ligands: structural, magnetic and Mössbauer spectroscopic studies of two FeII–GdIII co mplexes

Abstract

Complex [Fe^IIGd^III{pyCO(OEt)pyCOH(OEt)py}₃](ClO₄)₂ (1) crystallizes in the Cc space group and contains one hexacoordinate ferrous ion and one enneacoordinate Gd^III ion. Complex [Fe₂^IIGd^III{pyCO(OEt)py}₄(NO₃)(H₂O)][Gd(NO₃)₅]_0.5(ClO₄) (2) crystallizes in the C2/c space group and contains two hexacoordinate ferrous ions and one octacoordinate Gd^III ion. Both complexes have been prepared by the metal-assisted ethanolysis of ligands di-2,6-(2-pyridylcarbonyl)pyridine (pyCOpyCOpy, dpcp) and di-2-pyridyl ketone ((py)₂CO, dpk), which exhibit similar structures. Mössbauer spectroscopic studies of 2 revealed the presence of two quadrupole-split doublets of equal intensities, each assigned to a ferrous site. These doublets exhibit similar isomer shifts (δ₁ = 1.14 mm s⁻¹, δ₂ = 1.11 mm s⁻¹) but quite different quadrupole splittings (ΔE_Q1 = 3.55 mm s⁻¹, ΔE_Q2 = 2.74 mm s⁻¹). Magnetic studies revealed weak ferromagnetic Fe^II–Gd^III interactions for both complexes (J_FeGd = +0.68 cm⁻¹, D_Fe = 12.0 cm⁻¹ for 1 and J_FeGd = +0.03 cm⁻¹, J_FeFe = −1.73 cm⁻¹ for 2, according to the -JS_iS_j spin-Hamiltonian formalism).