Preparation and Characterization of Cobalt (II)- Complexes of 4-Hydroxybenzaldehyde Semicarbazone and Amino Acid Esters Ligands

Cobalt (II) complexes with mixed ligands including 4-hydroxybenzaldehyde semicarbazone (HBSCH) and esters of amino acids A {phenol glycine ester (GlyP), phenol alanine ester (AlaP), 2-aminophenol glycine ester (GlyA) and 2-aminophenol alanine ester (AlaA)} have been prepared and characterized by physical chemical techniques. General formulaes [Co(HBSCH)(A)2(NO3)]NO3, [Co(HBSCH)(A)2(NO3)2], [Co(HBSCH)2(A)(NO3)]NO3 and [Co(HBSCH)2(A)(NO3)2] have been proposed for the complexes prepared in neutral medium. Whereas, the Preparation and Characterization of Cobalt (II)Complexes ... 12 formulaes [Co(HBSC)(A)2] and [Co(HBSC)2(A)] have been proposed for the complexes prepared in basic medium (where HBSC = deprotonated HBSCH ligand). The study suggested that all the complexes had octahedral geometries. INTRODUCTION Cobalt is known to be one of the trace elements essential to human nutrition. It is present in meat and dairy products and in vitamin B12. It is an important substance that can prevented the disease known as precious anemia, in which the blood was depleted of a dequate numbers of its carrying red cells [1]. The chemistry of transition metal complexes of semicarbazones has been receiving considerable attention because of their biological activities and providing models for metal ligand bonding sites in several enzymes [2-4]. In the solid state, these semicarbazones were existed in the keto form (Figure 1a). In solution, however, they were known to tautomerize into the enol form (Figure 1b). Complexation usually took place through the N and O donor atoms [2,5-8], resulting in the formation of a five-membered chelate ring (Figure 1c and 1d). Figure 1: Semicarbazone ligand and its coordination compound Amino acids and their derivatives have been used for different purposes [9-13]. A good deal of work has been reported on the formation of amino acid esters chelates involving ligands containing different donating atoms such as nitrogen, oxygen and sulfur [14-20]. Coordination compounds of mixed ligands were of a considerable importance in the field of metalloenzymes and biological activities in addition to other purpose [21-26]. Hence a large number of coordination compounds containing mixed ligands with transition and non-transition metal ions have been reported recently [27-30]. Due to the importance of semicarbazone, amino acid esters and mixed ligands complexes we took a humble part in the chemistry of their complexes. Recently, some articles (a) (b)