Template synthesis of copper complexes of dinucleating and tetranucleating macrocyclic ligands

The reaction of N,N′-dimethyl-N,N′ -trimethylenedi(3-aminomethyl-5-methylsalicylaldehydato)copper(II) with 1,3-diaminopropane in DMF afforded the [1 + 1] condensation product [Cu(L)] and the [2 + 2] condensation product [Cu₂(R)]. The dinucleating macrocyclic ligand (L)^2- has one N(amine)₂O₂ and one N(imine)₂O₂ metal-binding sites sharing two phenolic oxygen atoms and the tetranucleating macrocyclic ligand (R) ^4- has two N(amine)₂O₂ and two N(imine) ₂O₂ sites in an alternate arrangement in the macrocyclic framework. The mixture of [Cu(L)] and [Cu₂(R)] was treated with CuCl₂ to give [Cu₂(L)Cl₂] (1a) and [Cu ₄(R)Cl₄] (2a), which were separated based on different solubility in methanol. 1a and 2a were converted into [Cu ₂(L)](ClO₄)₂ (1b) and [Cu ₄(R)(dmf)₂](ClO₄)₄·2H ₂O (2b), respectively, by the treatment with AgClO₄. 1a and 1b each has a dinuclear core doubly bridged by the phenolic oxygen atoms. The crystal structure of [Cu₄(R)(dmf)₂](ClO ₄)₄·2DMF·H₂O·PrOH (PrOH = 2-propanol) (2b') was determined by X-ray crystallography. It has a dimer-of-dimers structure where each N(amine)₂O₂ entity accommodates one Cu ion in the usual tetradentate chelating mode, whereas each N(imine)₂O₂ entity assumes a spread shape to combine one Cu ion with its NO donor atoms and another Cu ion with the remaining NO donor atoms. 2b can be converted into 2a in the presence of chloride ion. Based on magnetic and visible spectral studies, 2a is supposed to have a folded structure of 2b with two Cu-Cl-Cu linkages.