Thermochimica Acta 421 (2004) 153–162 Study of the ternary complexes of copper with salicylidene-2- aminothiophenol and some amino acids in the solid state Ahmed A. Soliman a,b,∗ , Gehad G. Mohamed b a Department of Chemistry, Faculty of Science, UAE University, Al-Ain, P.O. Box 17551, AbuDhabi, United Arab Emirates b Departmentof Chemistry, Faculty of Science, Cairo University, Giza, Egypt Received 27 December 2003; received in revised form 29 February 2004; accepted 5 March 2004 Abstract The ternary complexes of copper (II) with salicylidene-2-aminothiophenol (L) and glycine, alanine, valine and histidene amino acids have been studied in solution and in solid state. The mixed ligand complexes have been isolated and characterized based on elemental analyses, IR, UV-Vis, mass spectra, magnetic moment and thermal analysis (TGA). The isolated complexes were found to have the formula [M (L)(AA)] and the copper has the five coordinated square bipyramidal distorted trigonal bipyramidal (SBPTBP) geometry. The thermal stability of the complexes was studied and the weight losses were correlated with the mass fragmentation pattern. In all cases the amino acid moiety is removed first followed by the Schiff base moiety leaving CuO as the metallic residue. The metallic residue was also confirmed by powder XRD powder diffraction. The kinetics of the thermal decompositions of the complexes was studied and the thermodynamic parameters were reported. © 2004 Elsevier B.V. All rights reserved. Keywords: Copper; Schiff base; Amino acids; Thermal study 1. Introduction A large number of Schiff bases and their complexes have been studied for their interesting and important properties, e.g. their ability to reversibly bind oxygen [1], catalytic activity in the hydrogenation of olefins [2], transfer of an amino group [3], photochromic properties [4], complexing ability towards some toxic metals [5] On the other hand, the interaction between metal ions and amino acids is of con- siderable interest as models for metal–protein reactions and models in a variety of biological systems [6]. The ternary complexes of the Schiff bases and amino acids with metal ions bear the importance of both Schiff bases and amino acids. In addition, these species may be considered as rela- tively simple models for ternary enzyme/metal ion/inhibitor [7]. On the other hand Cu(II) complexes have extensively been studied in recent years. Their flexibility, facility of preparation and capacity of stabilizing unusual oxidation ∗ Corresponding author. Tel.: +971-507-132451; fax: +971-376-71291. E-mail addresses: ahmedsoliman2@hotmail.com, ahmedsoliman2@uaec.ac.ae (A.A. Soliman). states can explain their successful performance in mimick- ing peculiar geometries around the metal, leading to very interesting spectroscopic properties and varied reactivities [8–10]. The complexity of the stereochemistry of Cu(II) complexes is well known [11–13]. Owing to the plastic- ity of the coordination sphere, which is well-known as a feature of copper, Cu(II) ion forms a variety of complexes with coordination number 4–6 [14]. The geometries around the central Cu(II) atom are controlled primarily by the combinations of various ligands and the steric constrains in the ligand itself. For example, five-coordinate Cu(II) com- plexes, in most cases take on many different geometries ranging between square pyramidal (SP) and trigonal bipyra- midal (TBP) [15]. The stereochemistry of five-coordinated Cu(II) complexes has been reviewed and discussed com- prehensively by Hathaway [16,17]. Cu(II) complexes with tridentate [17–23] and tetradentate [24] Schiff base ligands were reported. In the five coordinate systems, the cop- per atom achieves distorted square pyramidal or distorted trigonal bipyramidal geometries. The binary complexes of copper with salicylidene-2- aminothiophenol was studied by the first author and oth- ers [20]. Herein, we report the synthesis, characterization 0040-6031/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.tca.2004.03.010