Fixation of CO2 in air: Synthesis and crystal structure of a μ3-CO3-bridged tricopper(II) compound

A novel trinuclear copper(II) compound [{(L3)Cu(OClO3)}3(μ3-OCO2)][ClO4] has been synthesised using an N-tridentate symmetrical pyridylalkylamine ligand, N-methyl-N,N-bis(2-pyridylmethyl) amine (L3). The structure of the complex has been determined by X-ray crystallography; it is found to crystallise in the hexagonal space group P63/m with a = 13·936(2), b = 13·936(2), c = 14·895(3) Å, α = β = 90°, γ = 120°. The complex possesses a 6̅ symmetry axis passing through the carbon atom of the triply bridging carbonate ion, with the three symmetry related copper ions connected to one another through the oxygen atoms from the bridging carbonato group, giving an equilateral triangular array of copper centres. Each copper ion has distorted square pyramidal environment with the basal plane formed by three nitrogen atoms of the ligand L3 and the oxygen atom of the bridging carbonato group. The apical position at each copper is provided by the weak oxygen coordination from the perchlorate ion.