Influence of temperature on the crystallization of Cu^II complex with tetradentate Schiff base

<p>The complex of copper(II) with N₂O₂ Schiff base, 2,2′-[1,3-propanediyl)bis(nitriloeth-1-yl-1-ylidene)]diphenol (<b>H</b>_<b>2</b><b>L</b>), has been synthesized from methanol. Crystallization of the complex was conducted at room temperature (20 °C) and at 4 °C. Carrying out the crystallization process at various temperatures leads to the formation of two different complexes CuL·MeOH (<b>1</b>) and [{Cu₂L₂}{CuL}₂]·2MeOH (<b>2</b>). The Schiff base and its complexes were characterized by elemental analysis, X-ray crystallographic techniques, spectroscopic (UV–Vis, IR), and thermal (TG\DSC) methods. Complex <b>1</b> crystallizes in the monoclinic space group <i>P2</i>_<i>1</i><i>/c</i>. The N₂O₂ core forms a tetrahedrally distorted square-planar geometry around the metal center. Crystallization of <b>2</b> took place in the centrosymmetric triclinic space group (<i>P</i>). In the structure of <b>2</b> there are two crystallographically different Cu^II ions, one is four-coordinate in a square planar geometry, whereas the second has a five-coordinate square pyramidal geometry. The complexes are stable at ambient temperature. After heating at first they lose methanol molecules, then the organic part undergoes gradual fragmentation and combustion.</p