COORDINATION OF Co(II), Ni(II), Cu(II), Zn(II), Cd(II) AND Hg(II) WITH THE NEW SCHIFF-BASE DERIVED FROM 4,5-DIHYDROXIPHTALALDEHIDE AND 2-AMINOTHIAZOLE

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1 OORDIATIO OF o(ii), i(ii), u(ii), Zn(II), d(ii) AD g(ii) WIT TE EW SIFF-BASE DERIVED FROM 4,5-DIYDROXIPTALALDEIDE AD 2-AMIOTIAZOLE Monica Iliş, Angela Kriza, Veronica Pop, Anca icolae ** abstract: A series of new complexes of type [ML 2].x 2O (where x = 0 for M = Zn(II), d(ii) and g(ii); x = 1 for M = o(ii), i(ii) and u(ii); L 2 is a Schiff-base derived from 4,5-dihydroxiphtalaldehide and 2-aminothiazole) have been prepared. The compounds were characterized by elemental analysis, IR and UV-VIS spectra, magnetic moments and thermal behaviour have been discussed. Introduction A great number of complexes of different transitional metallic ions with bidentate Schiffbases, derived from 2-aminothiazole and from different type of carbonylic compounds, have been reported. eterocyclic ligands containing nitrogen and sulf donor atoms have been extensively studied due to their biological applications, in particular as pesticides and drugs [1-4]. In order to obtain more information about the preparation conditions, the properties and the stereochemistry of the metallic chelates with Schiff-bases, derived from 2-aminothiazole, a new series of complexes of type [ML 2 ].x 2 O (x = 0 for M = Zn(II), d(ii) and g(ii); x = 1 for M = o(ii), i(ii), u(ii); L 2 is a Schiff-base derived to 2- aminothiazole and 4,5-dihydroxiphtalaldehide, has been prepared. Materials and Methods The chemicals were purchased from Aldrich and all manipulations were performed using materials as received. The IR spectra were recorded on a BIO-RAD FTIR 135 spectrophotometer using KBr pellets. Electronic spectra have been obtained by diffuse reflectance technique, using MgO as standard, with a UV-VIS arl Zeiss Jena spectrophotometer. The magnetic moments have been measured by the Faraday method. Thermal decomposition was studied with a MOM Q-1500 D derivatograph. Metallic ions were estimated by the AA 6 DA VARIA TETRO atomic absorbtion spectrophotometer and nitrogen has been determined by the Kjeldahl method. The Schiff-base (L 2 ) was prepared by mixing the methanolic solutions of 4,5- dihydroxiphtalaldehide and 2-aminothiazole (molar ratio 1:1) and refluxing for 2 h, on a water bath, filtered, washed with methanol, dried and recrystallized from methanol, with melting point at 210 o. Department of Inorganic hemistry, Faculty of hemistry, University of Bucharest ** Department of Organic hemistry, Faculty of hemistry, University of Bucharest Analele UniversităŃii din Bucureşti himie, Anul XIV (serie nouă), vol. I-II, pg opyright 2005 Analele UniversităŃii din Bucureşti

2 118 MOIA ILIŞ et al. The compounds were prepared by mixing, at room temperature, with stirring the methanolic solutions of Schiff-base derived from 4,5-dihydroxiphtalaldehide and 2- aminothiazole and the salt of the appropriate metallic ion, in molar ration 2:1. The p of the resulting solution was adjusted to about 7 by adding aqueous solution of a 2 O 3. By changing the p, coloured precipitates have been obtained. The precipitates were filtered, washed with methanol and were dried in vacuum. Results and Discussion The o(ii), i(ii), u(ii), Zn(II), d(ii) and g(ii) compounds with the Schiff-base derived from 4,5-dihydroxiphtalaldehide and 2-aminothiazole, were obtained as powers with high melting points and low solubility in organic solvents. Anal. for O 7 4 S 2 o: calc. (%) 9.80, o 10.31, found (%) 9.60, o 10; for O 7 4 S 2 i: calc. (%) 9.81, i 10.28, found (%) 9.50, i 9.98; for O 7 4 S 2 u: calc. (%) 9.73, u 11.04, found (%) 9.21, u 10.74; for O 6 4 S 2 Zn: calc. (%) 9.73, Zn 11.35, found (%) 9.32, Zn 11.00; for O 6 4 S 2 d: calc. (%) 8.99, d 18.05, found (%) 8.62, d 17.45; for O 6 4 S 2 g: calc. (%) 7.88, g 28.21, found (%) 7.42, g The elemental analysis for all these complexes are in agreement with the proposed formula [ML 2 ].x 2 O (where x = 0 for Zn(II), d(ii) and g(ii); x = 1 for o(ii), i(ii) and u(ii)). In order to get data concerning the ligand mode coordination to metallic ions, the IR spectra, on the cm -1 range, for free ligand and for complexes, have been carried out (Table 1). Table 1. The characteristic frequencies in IR (cm -1 ) for the ligand and complexes ompound ν = ν -O ν - ν -O ν -S ν -O phenolic exocyclic L 2: 11 8O 3 2S [ol 2]. 2O [il 2]. 2O [ul 2]. 2O [ZnL 2] [dl 2] [gl 2] In the spectrum of the free ligand, the sharp band at 1595 cm -1 can be assigned to the ν = vibration. In the spectrum of the complexes, this band is found at the lower values ( ν = 9-17 cm -1 ). The lowering of the ν = frequency in the complexes, indicates the coordination of the azomethine nitrogen atom at the metallic ion [5]. The coordination through the azomethinic nitrogen atom is supported by the shift of ν - (exocyclic) frequency to lower wave number ( ν = 9-18 cm -1 ) in the IR spectra of complexes compare to IR spectrum of the free ligand. The infrared spectrum of the free ligand shows a band at 1141 cm -1 assigned to the vibration frequency of the phenolic -O group. In the spectrum of the complexes, this band undergoes a positive shifts (with 7-17 cm -1 ) indicating that the Schiff-base is bonded to the metallic ions through the oxygen phenolic atoms [6-8]. The ν -S and ν -O are not affected by coordination to metallic ion.

3 OORDIATIO OF o(ii), i(ii), u(ii), Zn(II), d(ii) AD g(ii) 119 In addition, all IR spectra belonging to the o(ii), i(ii) and u(ii) compounds present an absorption band at 3415, 3407 and 3417 cm -1, confirming the existance of water molecules in the structure of the crystalline lattice [9]. The presence of the crystallizations water was indicated by the thermogravimetric analysis. The information reffering to the geometry of these complexes are obtained from the electronic spectra and from the value of the magnetic moments (Table 2). Table 2. Electronic spectra and magnetic moments of the [ML 2].x 2O complexes ompound ν (cm -1 ) Assignments µ eff (MB) π π* L n π* π π* n π* [ol 2]. 2O A T 1(P) A 2 4 T 1(F) π π* n π* [il 2]. 2O A 1g 1 B 2g A 1g 1 A 2g π π* n π* [ul 2]. 2O d xy d xz d xy d z π π* [ZnL 2] n π* π π* [dl 2] n π* π π* [gl 2] n π* In the electronic spectrum of the ligand there are two absorption bands assigned to π π* and n π* transitions [10, 11]. These transitions are found also in the spectra of the complexes, but they are shifted towards lower frequencies, confirming the coordination of the ligand at the metallic ions. In the electronic spectrum of [ol 2 ]. 2 O complex two new absorption bands at cm -1 and cm -1, are observed. These bands are assigned to 4 A 2 4 T 1 (P) and 4 A 2 4 T 1 (F) transitions, respectively [12]. These transitions indicate a square-planar geometry of the complexes. The observed magnetic moment, 2.30 MB [13] is in agreement with this structure. The electronic spectrum of [il 2 ]. 2 O complex shows two new bands at cm -1 and cm -1, which are attributed to 1 A 1g 1 A 2g and 1 A 1g 1 B 2g, respectively [12]. These transitions and the magnetic moments (µ eff = 0) suggest a square-planar stereochemistry [14]. In the electronic spectrum of the [ul 2 ]. 2 O complex was noticed the presence of a two new bands at cm -1 and cm -1, assigned to the d xy d xz, respectively d xy d z 2 transitions [12]. These transitions, as well as the measured value of the magnetic moment

4 120 MOIA ILIŞ et al. (1.82 MB) suggest a square-planar stereochemistry of the compound. We assumed for the Zn(II), d(ii) and g(ii) complexes a tetrahedral geometry [12]. The thermal behaviour of the compounds of o(ii) and i(ii) was studied by thermogravimetric analysis. The heating rate was 10 o /min, while the temperature interval was o. The weight losses are presented the Table 3. ompound [ol 2]. 2O [il 2]. 2O Table 3. Thermal behaviour of the prepared compounds Decomposing Temperature Weight losses stages range ( o Thermal effect ) (%) exo exo endo exo- 85 Residue (%) (o 3O 4) (io) The studied of o(ii) and i(ii) compounds are decomposing in two successive stages. The first stage of decomposition consisted in elimination of the crystallization water; the last stage is exotherme and corresponds to the burning of the organic components. From the weight losses registered in TG and TDG of the i(ii) compound, the following process of decomposition may be presented: 1. i O 7 4 S 2 (s) o i O 6 4 S 2 (s) + 2 O(g) 2. i O 6 4 S 2 (s) + 29O 2 (g) o io(s) + 22O 2 (g) + 2SO 2 (g) + 4O 2 (g) O(g) The above-mentioned data suggest the following structural formula (Figure 1): S O O O M O O O S Fig 1. The proposed structure for compounds onclusions In this article we present the results of a study of the new complexes of o(ii), i(ii), u(ii), Zn(II), d(ii) and g(ii) with Schiff-base derived from 4,5-dihydroxiphtalaldehide and 2-aminothiazole. The complexes were characterized as square-planar species of o(ii),

5 OORDIATIO OF o(ii), i(ii), u(ii), Zn(II), d(ii) AD g(ii) 121 i(ii), u(ii), and as tetrahedral species of Zn(II), d(ii) and g(ii) based on the chemical analysis, thermal behaviour, spectrometric and magnetic measurements. REFEREES 1. Dash., Pradhan J., (1991) Indian J,hem. Sect.A, Inorg., Bio-Inorg.,Phys., Theor.Anal.hem., 70, Rosamma T., Parameswaran G., (1992) J.Indian hem.soc., 69, Bhaskare.K., ankare P.P., (1995) J.Indian hem.soc., 72, Zaidi A. Aftab S., Zaidi A. Rehan S., Shaher S.A., Tabrez A., (1987) Indian J.hem Sect.A, 26, Percy G.., Thornton D.A., (1972) J.Inorg.ucl.hem., 34, Lewis J.W., Sandorfy., (1982) an.j.hem., 60, Gillard R.D., Mcleverts J.A., (1987) omprehensive oordination hemistry, Eds. Wilkinson, Pergamon Press, Oxford 8. Bhardway S., Ansari M.., Jain M.., (1987) Indian J.hem., 28A, akamoto K., (1978) Infrared and Raman Spectra of Inorganic and oordination ompounds, 3 rd Ed., John Wiley, ew York 10. Ito M., ata M., (1955) Bull.hem.Soc.Jpn., 28, Friedel R.A., Orchin M., )1958) Ultraviolet Spectra of Aromatic ompounds, John Wiley, ew York 12. Level A.B.P., (1984) Inorganic Electronic Spectroscopy, Elsevier Publishing ompany, Amsterdam 13. Sacconi L. et al., (1968), J.Am.hem.Soc., 84, olm R.M., (1961) J.Am.hem.Soc., 83, 468