2-[Bis(2-hydroxyethyl)amino]acetonitrile (CN-dea) has been consider to be a useful ligand for the coordination chemistry. Two new polymorphs of copper(II) have been obtained from the reaction of copper(II) pivalate or isobutyrate with a ligand. The latter compound was obtained in 98% yield by reaction of diethanolamine with 2-chloroacetonitrile at room temperature. X-ray crystallography revealed the formation of two polymorphic modifications of complex [Cu(COO-dea)2], where COO-dea = COOH-polyalcoholamine (Fig.1). The crystals of both polymorphs are monoclinic, space group P21/c, but differ in unit cell parameters: a = 6.5973(4), b = 12.2194(7), c = 9.9637(10) Å, β = 102.847(7)°, V = 783.12(11) Å3 (I) when copper(II) pivalate has been used as starting component and a = 9.4832(8), b = 12.2965(9), c = 7.1719(7), β = 111.24 (12)°, V = 779.52(12) Å3 (II) in the case of copper(II) isobutyrate. Crystal structures of polymorphs revealed similar centrosymmetric complexes with a N2O4 4+2 square-bipyramidal coordination surrounding. The basal plane is formed by two nitrogen and two alcohol oxygen atoms from two COO-dea ligands, and monodentate carboxylic groups coordinate to the metal in axial positions. I II   Fig. 1. Molecular structure if polymorph I and II of complex [Cu(COO-dea)2]   The polymorphs differ by the conformation of a non-coordinated alcohol branch, which adopts gauche conformation in I (torsion angle N1-C-CO4 = 67.4o) and anti-conformation in II (torsion angle N1C-C-O4 = 178.2o) and result in different pattern of H-bonds in crystal. Thus, the process of complex formation results in the transformation of starting ligand CN-dea into COO-dea.       Acknowledgement. Authors thank the projects SCOPES IZ73Z0_152404/1 and CSSDT 15.817.02.06F for financial support.