Structure, magnetic properties and DFT calculations of azido-copper(ii) complexes with different azido-bonding, nuclearity and dimensionality

Abstract

Four bridged-azido Cu(II) complexes were synthesized and structurally characterized: [Cu₂(Et₃en)₂(μ_1,1-N₃)₂(N₃)₂] (1), [Cu₂(ip₂en)₂(μ_1,1-N₃)₂(N₃)₂] (2), catena-[Cu₂(Et₂Meen)₂(μ_1,3-N₃)₃]ClO₄ (3) and catena-[Cu(ambza)(μ_1,1,3-N₃)₂] (4), where Et₃en = N,N,N′-triethyl-1,2-diaminoethane; ip₂en = N,N′-diisopropyl-1,2-diaminoethane; Et₂Meen = N,N-diethyl-N′-methyl-1,2-diaminoethane; and ambza = 2-aminobenzylamine. Single crystal X-ray crystallography revealed that complexes 1 and 2 are dinuclear with doubly bridged μ_1,1-N₃, whereas complexes 3 and 4 constitute polymeric species with an alternative sequence of single and double μ_1,3-N₃ bridges for 3 with a 1D chain, and triple μ_1,1,3-bridging azide in 4 with a 2D extended structure. Variable temperature magnetic susceptibilities over the temperature range of 2–298 K revealed a weak antiferromagnetic coupling (J = −1.8 cm⁻¹) for 1, and a ferromagnetic coupling with J values of 7.0 and 7.7 cm⁻¹, respectively, for complexes 2 and 4, respectively. Compound 3 shows a new topology for Cu(II) alternating chains [Cu(1)(μ_1,3-N₃)₂Cu(1′)]-(μ_1,3-N₃)-[Cu(2′)(μ_1,3-N₃)₂Cu(2′′)]-(μ_1,3-N₃)-[Cu(1)(μ_1,3-N₃)₂Cu(1′)]-… Three different coupling constants were obtained through a fitting procedure and by DFT calculations.