One-dimensional coordination polymers constructed from di- and trinuclear {3d–4f} tectons. A new useful spacer in crystal engineering: 1,3-bis(4-pyridyl)azulene

Abstract

Four new heterometallic 3d–4f complexes have been obtained using bi- and trinuclear building blocks: ¹_∞[Ni(L¹)Gd(NO₃)₃(azbbpy)]·CH₃CN (1), [Zn(L¹)Eu(NO₃)₃(azbbpy)]·H₂O (2), ¹_∞[(CuL²)₂Gd(NO₃)₂(dca)] 3 and ¹_∞[(NiL²)₂Dy(H₂O)₄(oxy-bbz)]NO₃·3H₂O (4), [H₂L¹ = 1,3-propanediyl-bis(2-iminomethylene-6-methoxyphenol), H₂L² = 2,6-di(acetoacetyl)pyridine, azbbpy = 1,3-bis(4-pyridyl)azulene, dca⁻ = dicyanamide anion, and oxy-bbz = the dianion of the 4,4′-oxy-bis(benzoic) acid]. 1 and 2 represent the first complexes containing 1,3-bis(4-pyridyl)azulene as a ligand. 1, 3, and 4 are one-dimensional coordination polymers constructed from heterometallic nodes connected by the exo-dentate ligands. Helical chains are assembled in the case of 4. The analysis of the packing diagram for 1 reveals the occurrence of π–π stacking interactions established between the azulene rings from neighboring chains, which lead to supramolecular layers. The magnetic properties of 3 in the temperature range 1.9–300 K have been investigated. Intra-node ferromagnetic interactions are established between the Cu^II and Gd^III ions (J = +2.7 cm⁻¹, Ĥ = −J(Ŝ_Cu·Ŝ_Gd + Ŝ_Cu·Ŝ_Gd).