Cd(ii) and Cu(ii) coordination polymers constructed from the expanded 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene ligand: conventional and ultrasound-assisted synthesis, crystal structure, luminescence and magnetic properties

Abstract

A 3D open inorganic/organic framework, {[Cd(μ-L)(μ₃-SO₄)(H₂O)]·H₂O}_n (1) [L = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene] was synthesized by the reaction of CdSO₄·8H₂O with L. The treatment of Cu(NO₃)₂·3H₂O with the same N,N′-donor ligand in two different solvent mixtures, methanol/dichloromethane (2) and methanol/chloroform (3), afforded two new ladder-like coordination polymers of formula {[Cu(μ-L)(μ-NO₃)(NO₃)]·solv}_n [solv = CH₂Cl₂ (2) and CHCl₃ (3)]. The non-interpenetrated ladder motifs 2 and 3 enclathrate the uncoordinated solvent molecules. Crystalline coordination polymers 1 and 3 were also successfully prepared by a sonochemical method under different reaction conditions. Our results indicate that the size of the particles is dependent on the irradiation time. 1 and 3 exhibit intense luminescent emissions in the solid state at room temperature. Cryomagnetic measurements of 3 show the occurrence of a ferromagnetic interaction between the copper(II) ions through the double oxo-nitrate bridge together with a very weak inter-ladder antiferromagnetic interaction [J = +4.93(2) cm⁻¹, g = 2.10(1) and Θ = −0.567(5) K].