Discrete dinuclear complex to extended 2D compound in a Cu-azido system by controlling coligand stoichiometry: synthesis and magneto-structural correlations.

This article describes syntheses, structural characterizations and magnetic studies of two different Cu(II)-azido compounds, a discrete dinuclear complex and an extended 2D network. The compounds, [Cu(μ(1,1)-N3)(N3)(Me2en)]2 (1) and [Cu3(μ(1,1,1)-N3)2(μ(1,1,3)-N3)(μ(1,1)-N3)2(μ(1,3)-N3)(Me2en)]n (2), have been synthesized by controlling the relative concentration of the blocking ligand, N,N-dimethylethylenediamine (Me2en). Compound 1 is a dinuclear compound which is formed by a doubly asymmetric μ(1,1)-N3 bridging ligand, while 2 is a rare Cu-azido system where four different types of binding modes of azide ligands are present in a single compound. Compound 2 contains a hexanuclear core, where the Cu(II) centres are connected to each other by μ(1,1,1), μ(1,1) and μ(1,1,3) bridging azide ligands. The hexanuclear core acts as a secondary building block and further assembles via μ(1,3) and μ(1,1,3) azide groups, forming a 2D network in the crystallographic ac plane. Interestingly, temperature-dependent magnetic study suggests that the dinuclear compound 1 exhibits an antiferromagnetic interaction through the μ(1,1)-N3 bridge, which has also been supported by density functional theory (DFT) calculations. In the case of 2, an overall dominant ferromagnetic interaction is observed while antiferromagnetic interaction operates between the hexanuclear cores.