Hydrolysis of imidazolidine ligands mediated by CuII: Mononuclear, tetranuclear and 1D CuII-amine complexes

The potential ability of HL1 [2-(1,3-dimethylimidazolidin-2-yl)phenol] and H3L2 [2,2′-(2-(2-hydroxyphenyl)imidazolidin-1,3-diyl)diethanol] to act as ligands towards copper(II) was tested under different reaction conditions. These essays show that both HL1 and H3L2 are unstable in the presence of CuII, suffering total imidazolidine ring hydrolysis and yielding amine complexes. In this way, four different copper(II) complexes could be isolated, depending on the reaction conditions, the ligand itself and the counterions present in the medium. Accordingly, the complexes [Cu(am1)(H2O)(OAc)2]n (1) (am1 = N,N′-dimethylethylenediamine), [Cu(am1)(H2O)2(p-O2C-C6H4-CO2)]n (2), [Cu(am1)2(NO3)2] (3) and [Cu4(am2)2(OAc)8]·CH3CN·2H2O (4) (am2 = N,N′-bis(2-hydroxyethyl)ethylenediamine) were obtained as the main products of the hydrolytic processes. The crystallographic characterisation of all of them shows great structural diversity. Thus, 1 is a mono-aqua bridged coordination polymer and 2 is a terephthalate bridged zig-zag chain, while 3 and 4 are discrete mononuclear and tetranuclear complexes, respectively. Magnetic characterisation of 1, 2 and 4 reveals different behaviours, with magnetic exchanges varying from weak ferromagnetic (2) to quite strong antiferromagnetic (4). The magnetic study of 1 is remarkable, as it constitutes, as far as we know, the first mono-aqua bridged copper(II) chain magnetically analysed, being an antiferromagnetic system.

Graphical abstractImidazolidine ligands, derived from diamines and salicylaldehyde, suffer total hydrolysis in the presence of CuII, yielding coordination polymers, mononuclear or tetranuclear amine complexes as a function of the amine and the counterion present in the reaction medium.Figure optionsDownload full-size imageDownload as PowerPoint slide