Design, synthesis, and structural study of mono- and polynuclear Cu(II) iminodiacetate complexes

The synthesis of three structurally distinct copper(II) coordination compounds was conducted under different pH conditions, employing iminodiacetic acid (IDAH2) as the ligand. In a neutral medium, compound 1 was obtained as a two-dimensional ionic coordination polymer with the formula {(NH2(CH3)2)2[Cu3(IDA)4]·1.75H2O}n, featuring layered [Cu3(IDA)4]n 2n- anions stabilized by hydrogen bonding networks (pH= 6-6.5). In a basic medium (pH= 8-8.5), compound 2 was isolated as a neutral 2D molecular coordination polymer, {[Cu3(IDA)2(IDAH)2]·5H2O}n, based on trinuclear copper units bridged by bi- and monodeprotonated ligands. Acidic conditions (pH= 3) led to the formation of compound 3,((CH3)2OH)2[Cu(IDA)2]·[Cu(IDAH)2]. The compound exhibits an ionic structure composed of a neutral and anionic mononuclear complexes, charge-balanced by protonated dimethylether cations. The observed structural diversity is attributable to the various deprotonation states of the ligand, in association with the nature of the outer-sphere components. A detailed investigation into the infrared (IR) spectra of the compounds provided substantial evidence supporting the proposed coordination modes and hydrogen-bonding interactions. These interactions have been demonstrated to play a pivotal role in the formation of extended supramolecular architectures in all three compounds.