Abstract
The reaction of bis-[2-amino-4-pheny1-5-thiazolyl] disulfide with 5-nitro-salicylaldehyde in absolute ethanol resulted in the formation of a new Schiff base ligand H2L (1). Characterization of the ligand was performed by FT-IR, 1H NMR, 13C NMR, UV-Vis, elemental analysis and single crystal X-ray diffraction. The ligand, (1), possesses a disulfide –S–S– bridge of 2.1121 (3) ? length, and the molecule adopts a cis-conformation around this bond. In the crystal structure of (1), an intramolecular O–H···N hydrogen bond with D… A distance of 2.69 (3) ? was present. The reaction of (1) with Co(NO3)2·6H2O and CuCl2·2H2O in methanol afforded the corresponding metal complexes. The obtained solids were further investigated by elemental analysis and UV-Vis titration that confirmed the formation of [CoL] and [ClCuHL] complexes. However, recrystallizaion of the Co(II) complex in dimethylsulfoxide caused the complete hydrolysis of the imine bond and afforded a Co(II) complex in which two 5-nitro-salicylaldehyde and two DMSO molecules were coordinated to the central metal in an octahedral fashion. This structure (2) was also confirmed by single crystal X-ray analysis.
Highlights
Schiff bases are compounds with the structure consisting of a C=N bond, generally formed by condensation of an amine and active carbonyl group, initially developed by Hugo Schiff [1] [2]
They argue that the hydrolysis is dependent on several factors, and was observed such as the pH of the reaction medium, the size of the chelate rings formed by the diamine fragment of the Schiff base, the coordinating ability of the counter anions, the nature of the metal ions, and the effect of carbonyl compounds [27]-[34]
Elemental analysis was carried out using a Perkin-Elmer 2400(II) CHN analyzer. 1H NMR and 13C NMR spectra were recorded with a Bruker Avance 300 spectrometer using DMSO-d6 as solvent
Summary
Schiff bases are compounds with the structure consisting of a C=N bond, generally formed by condensation of an amine and active carbonyl group, initially developed by Hugo Schiff [1] [2]. Schiff base ligands are synthesized and form complexes with almost all metal ions in various oxidation states [3] [4]. These metal complexes can be used in catalytic reactions and as models for biological systems. We noticed that a disulfide compound is obtained as a byproduct during the preparation of bis-[2amino-4-pheny1-5-thiazolyl] sulfide by following the procedure reported by Dodson and King [35]. These two products may be separated by means of column chromatography. A drawing of the principle products characterized in this report, [ClCuHL] and the hydrolysis product (2) 77
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