Structural and Magnetic Diversity Based on Different Imidazolate Linkers in Cu(II)-Azido Coordination Compounds

This
Article reports the syntheses, structural characterization,
and magnetic studies of four different Cu­(II)-azido compounds based
on imidazole or substituted imidazole ligand. The compounds, [Cu2(μ1,1-N3)2(EtimiH)4(ClO4)2] (1) (EtimiH =
2-ethylimidazole), [Cu2(μ-Meimi–)­(MeimiH)2(μ1,1-N3)2(μ1,3-N3)]n (2) (MeimiH = 2-methylimidazole; μ-Meimi– is the bridging mononegative anion of 2-methylimidazole),
[Cu2(μ-imi–)­(imiH)2(μ1,1-N3)2(μ1,3-N3)]n (3), and [{Cu2(μ1,1-N3)2(μ1,3-N3)­(μ-imi–)­(imiH)3}·H2O]n (4) (imiH = imidazole; μ-imi– = bridging
mononegative anion of imidazole), have been synthesized by the self-assembly
of Cu­(II) salts, azide ion, and the corresponding imidazole bridging
ligands. By changing the substitution on the second linker (imidazole
or substituted imidazole) and varying synthetic conditions, diverse
structural and magnetic features have been achieved in compounds 1–4. Compound 1 has a double
end-on azido bridged dinuclear core, while the other compounds (2–4) have 2D networks. Compound 2 and 3 contain 1D chains with alternate μ1,1-N3 and μ-Meimi– bridging,
and such chains are further connected through a μ1,3-N3 bridge to result in the formation of the 2D network.
Compound 4 is a novel 2D coordination polymer consisting
of a zigzag 1D coordination chain having (μ1,1-N3)2, μ-imi–, and (μ1,3-N3)2 bridging groups and the chains
undergo bridging through a μ1,3-N3 group
resulting in the 2D network. Temperature dependent magnetic measurements
show diverse magnetic properties of 1–4. Such versatile magnetic behaviors have been correlated to the respective
bridging mode of azide and the corresponding imidazole bridging ligands.