Cluster-based copper(ii) coordination polymers with azido bridges and chiral magnets

Abstract

Three homochiral layered complexes, [Cu₃(R-chea)₂(N₃)₆]_n (1), [Cu₃(S-chea)₂(N₃)₆]_n (2) (chea = 1-cyclohexylethylamine) and [Cu₃(S-phpa)₂(N₃)₆]_n (3) (phpa = 1-phenylpropylamine), and three novel cluster-based coordination polymers, [Cu₆(1,2-pn)₄(N₃)₁₂]_n (4) (1,2-pn = 1,2-diaminopropane), {[Cu₈(en)₄(N₃)₁₆]·H₂O}_n (5) (en = ethylenediamine) and [Cu₆(N-Ipren)₂(N₃)₁₂]_n (6) (N-Ipren = N-isopropylethylenediamine), have been synthesized by the self-assembly reactions of Cu(NO₃)₂·3H₂O, NaN₃ and small organic amine ligands. Their crystal structures are determined by single-crystal X-ray diffraction. Complexes 1–3 are composed of neutral 2D brick wall networks with only end-on azido bridges. Complexes 4 and 5 are 3D coordination polymers featuring copper–azido clusters and [Cu(diamine)₂]²⁺ units which are linked by the azido bridges. Complex 6 is a 3D coordination framework based on the hexanuclear copper(II) clusters [Cu₆(N₃)₁₂(N-Ipren)₂]. Magnetic studies show that complexes 1–3 are interesting chiral ferromagnets with the magnetic transition temperature at ca. 5.0 K. Complexes 4 and 5 show ferromagnetic coupling in the copper–azido cluster units and antiferromagnetic interaction between neighboring units, while complex 6 shows ferromagnetic ordering at 3.2 K.