SPECTROSCOPIC INVESTIGATION OF COPPER (II) COMPLEX WITH MIXED LIGANDS, ASPARTIC ACID AND UREA V.POP, L.DAVID 1, CECILIA SIMUŢ 2, SANDA FILIP 2, M.DRĂGAN 1 University of Bucharest, Department of Inorganic Chemistry, Bucharest, Romania 1 Babeş-Bolyai University, Faculty of Physics, Cluj-Napoca, Romania 2 University of Oradea, Faculty of Science, Department of Physics, Oradea, Romania The copper (II) with mixed ligands, L-aspartic acid and urea, Cu(II)(urea)(L-asp) H 2 O was synthesised and investigated by IR and electronic spectroscopy. In the IR spectrum of the studied complex appears the ν(o-h) absorption band at 3492 cm -1 which indicate the coordination of H 2 O molecule in apical position at the Cu (II) ion. The comparative analysis of the IR spectra for the ligands and the complex, indicate the coordination of the metallic centre to the oxygen and nitrogen atoms of the L-aspartic molecule due to the shift of the ν as (C-O) and ν(n-h) stretching vibrations with 61 cm -1, respectively 330 cm -1. The metallic ion binds the amino nitrogens atoms of the urea ligand due to the shift of the ν(n-h) vibrations with 47 cm -1. The geometry around the metallic centre is octahedral confirmed by two absorption bands in the electronic spectrum at 399 nm and 700 nm.
1. Introduction The copper (II) complexes with amino acids are very much investigated [1-3] for their polymer structure and because they represents simple models systems for the study of the magnetic interactions. The antioxidants properties of some metal-protein, their cardio-protecting and neurons-modelling activity are a consequence of the implication in different biological functions, which influenced the electronic transfer, the oxygen transport and the oxidation of the substances [4,5]. In this paper, the copper (II) with mixed ligands, L-aspartic acid and urea, Cu(II)(urea)(L-asp)H 2 O (Fig.1.) have been synthesised and investigated by IR and electronic spectroscopic methods. These methods give information on the Cu(II) coordination to the ligands and the local symmetry around the metallic centre. 2. Experimental The Cu(II)(urea)(L-asp)H 2 O complex was synthesised started from an intermediary CuU compound to which one was added an aqueous solution of amino-acid at a much basic ph then the isoelectric point, regulated with NaOH in ratio 1(AA):1NaOH (Table 1.). IR spectra were recorded in the 4000-400 cm -1 range with a Carl Zeiss Jena model UR-20 spectrophotometer using the KBr pellets and nujol techniques. Electronic spectra were performed in aqueous solutions within a range of λ=200-800 nm using an Unicam UV-Visible with Vision Software V 3.20. 18
Fig. 1. The structure of the Cu(II)UAsp complex. Table 1. Analytical data of the synthesised compound. Compound Colour Cu (%) N (%) C (%) H (%) Obs. CuUAsp blue 16.3 18.3 18.8 5.2 exp. 16.5 18.1 18.6 5.4 calc. 3. Results and discussion 3.1. IR spectra The coordination of the metallic centre to the oxygen and nitrogen atoms of the L-aspartic molecule is indicated by the shift of the ν s (C-O) and ν as (C-O)+NH 2 stretching vibrations for the Cu(II) complex (Fig.2) compared to those of the ligands. Fig. 2. IR spectra for the Asp ligand, CuU and CuUAsp complexes. 19
The metallic ion binds the amino nitrogen atoms of the urea ligand due to the shift of the ν(n-h) vibrations. The ν(o-h) absorption band at 3492 cm -1 for CuUAsp (Table 2), arises from the coordination of H 2 O molecule in apical position at the Cu (II) ion. Table 2. IR data for the mixed ligands and the Cu(II) complex. Band ν(o-h) ν(n-h) ν(ch 2 ) ν as (C-O)+NH 2 ν s (C-O) Position (cm -1 ) Urea 3346.8-1680.6 1465.6 Asp - 3010 2866 1690 1306 CuUAsp 3492 3340 2980 1629 1231 3.2. UV-spectra For the CuUAsp complex, the geometry around the metallic centre is hexacoordinate in a octahedric geometry as indicates the two absorption bands from the electronic spectrum [6], at 399 nm and 700 nm (Fig.3.). UV spectrum of CuUAsp complex is similar to those of Cu(L-asp)(o-phen), (650 nm) [7], characteristic to chromophores CuN 3 O 3, the aspartato anion acting as tridentate ligand for the same metallic centre [8]. Fig.3. Electronic spectra of the CuAsp and CuUAsp complexes. 20
4. Conclusions The coordination of the copper (II) to the mixed ligands arises from the shift of the ν s (C-O), ν as (C-O)+NH 2 and ν(n-h) stretching vibrations for the Cu(II) complex compared to those of the ligands and from the appearance of the ν(o-h) absorption band in the IR spectrum of complex. The local symmetry around the Cu(II) is octrahedral for CuUAsp complex as suggested the electronic data. 5. References [1] H.L. Lin, Z.X. Zhu, Z.X. Gu,Y.T. Chen, Polyhedron, 15 (19), 1996, p. 3241; [2] T. Szabó- Plánka, A. Rockenbauer, L. Korecz,, Polyhedron, 18, 1999, p. 1969; [3] A. Mangunson, I. Frapart, M. Abrahamsson, O. Horner, B. Akermark, L.C. Sun, J.J. Girerd, J. of Amer. Chem. Soc., 121(1) 1999, p. 89; [4] C. Place, E.M. Zimmermann, G. Gulliot, C. Bois, J. Chottard, Inorg. Chem, 37, 1998, p. 4030; [5] Y. Chen, R. Pasquinelli, M. Ataai, R. Koepsel, A. Kortes, R.R. Shepherd, Inorg. Chem., 39, 2000, p. 1180; [6] B.J.Hathaway, Comprehensive Coordination Chemistry, Ed. Pergamon Press, vol. 5, 1987, p. 674; [7] L. Antolini, G. Marcotrigiano, L Menabue, G.C. Pellacani, M. Salladini, M. Sola, Inorg.Chem, 24, 1985, p. 3621-3626; [8] G. Formicka-Kozolowska, H. Kozlowski, B. Jezowska-Trzebiatowska, Inorg. Chim. Acta, 1, 1997, p. 24-25. 21