A new (μ₃-carbonato)tricopper(II) complex with symmetry related equilateral triangular array of metal centers; structure and magnetism

Abstract

Using an unsymmetrical N-tridentate (2-pyridyl)alkylamine ligand methyl[2-(2-pyridyl)ethyl](2-pyridylmethyl)amine (mpepma), a new tricopper(II) complex [{(mpepma)Cu(OClO₃)}₃(μ₃-OCO₂)][ClO₄] (1), having triply bridging μ₃-carbonate group, with three symmetry related triangular array of copper(II) centers has been synthesized. In 1, each copper ion is five-coordinate (almost perfect square pyramidal) by three nitrogens from the ligand (two pyridyl and an amine) and an oxygen atom of the carbonate group in the equatorial plane and by an oxygen atom of the perchlorate ion in the apical position. Magnetic susceptibility data (2-300 K) were fitted using the Hamiltonian: H^{^}= gμ_BH(S₁+S₂+S₃)-J(S₁S₂+S₁S₃+S₂S₃), which corresponds to a triangular array of spins, corrected with a zJ' intertrimer interaction or zero-field splitting within the ground state, to fit low temperature data. It is concluded that the copper(II) ions in 1 are ferromagnetically coupled. The best parameters obtained are g = 2.11, J = 18 ± 1 cm^-1, zJ' = -0.36 ± 0.02 cm^-1 or D = 0.50 ± 0.05 cm^-1.