An imidazolate- and azide-bridged copper(II) coordination polymer consisting of alternating di- and mononuclear units

Using the Cu^II-imidazole(Him) complex [Cu(Him)₄Cl]Cl as the starting material, the imidazolate (im)- and azide-bridged Cu ^II coordination polymer [Cu₃(Him)₄(im) ₂(N₃)₄]_n was successfully obtained. Single-crystal X-ray analysis revealed that it possesses an im-bridged linear-chain structure consisting of alternating dinuclear units with a symmetric end-on azide-bridged [Cu(Iμ_1,1-N₃) ₂Cu]²⁺ core and mononuclear units. All of the Cu ions adopt a square pyramidal geometry with an azide at the Jahn-Teller elongated apical position. Some of the azides act as end-to-end interchain bridging ligands from the mononuclear unit to the nearest neighbouring dinuclear unit of the adjacent chain forming a two-dimensional network. Temperature-variable magnetic susceptibility measurements showed that it exhibits one-dimensional ferrimagnetic-like behaviour, which can be ascribed to two types of exchange couplings with opposite signs, namely a weak ferromagnetic coupling through the end-on azide bridges within the dinuclear units and a stronger antiferromagnetic coupling through the im bridges between the di- and the mononuclear units. The novel copper(II) coordination polymer [Cu₃(Him)₄(im) ₂(N₃)₄]_n is constructed with a combination of simple inorganic and organic bridging ligands, namely azide and imidazolate. It shows ferrimagnetic-like behaviour resulting from the coexistence of copper(II) di- and mononuclear units.