New Polynuclear Coordination Compounds Based on 2-(Carboxyphenyl)iminodiacetate Anion: Synthesis and X-rays Crystal Structures

In the present work, novel polymeric copper(II) coordination compounds, namely [Cu2(cpida)(H2O)4][Cu(cpida)]center dot 3H2O (1) (cpida3- = 2-(carboxyphenyl)iminodiacetate anion) and Na[Cu(cpida)] (3), were synthesized and characterized using infrared spectroscopy, thermogravimetric analysis, elemental analysis, and single-crystal X-ray diffraction. Compound 1 was obtained by slowly evaporating an aqueous solution of H3cpida, copper(II) sulfate, and NaOH at room temperature. The structural characterization revealed that 1 is an ionic entity formed by the [Cu(cpida)]- anion and the [Cu2(cpida)(H2O)4]+ cation, both of polymeric 1D structure. Compound 3 was prepared under similar conditions from copper perchlorate and crystallized via acetone diffusion. It is a coordination polymer formed by the [Cu(cpida)]- units, and the sodium cation is present in the structure, counterbalancing the anion charge. Depending on the crystallization conditions, it was possible to obtain other solvation forms of these structures. Starting from the conditions of compound 1, via the diffusion of ethanol, [Cu2(cpida)(H2O)4][Cu(cpida)]center dot H2O center dot 1/2EtOH (2) was precipitated, while a hydrate form of compound 3 with the formula Na[Cu(cpida)]center dot 2H2O (4) was obtained via methanol diffusion.