Construction of acetate-bridged dicopper(II) hybrid organic–inorganic networks with calix[4]arene-derived nitrogenous ligands

Abstract

The reactions of mono-, bis- and tetrapicolyl-p-tert-butylcalix[4]arene derivatives functionalised in the phenolic positions (L 1 –L 4 ) with copper(II) acetate resulted in the formation of discrete complexes or extended coordination polymers. The centrosymmetric dimer [Cu2(μ-O2CCH3)4(L 1 )2] 1, obtained with monodentate L 1 , has square pyramidal coordination around the copper centres and a cone conformer of monopicolyl-calix[4]arene acting as an axial ligand, with a molecule of acetonitrile hosted within its cavity. The potentially bidentate L 2 acts as a monodentate ligand, affording the complex [Cu2(μ-O2CCH3)4(L 2 )2] 2, which based on spectroscopic and combustion analysis data has a similar coordination sphere around Cu(II). Compound L 3 bridges two dicopper units in the coordination polymer [Cu2(μ-O2CCH3)4(μ-L 3 )] n 3, with the calixarene hosting a molecule of tetrahydrofuran. Finally, compound L 4 reacts with 4 equivalents of copper(II) acetate, presumably generating a two-dimensional coordination polymer formulated as [{Cu2(μ-O2CCH3)4}2(L 4 )] 4.