MANGANESE (III)

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THE EFFECT OF VARYING SCHIFF'S BASES ON

THE MANGANESE Mn(III) COMPLEX

INTRODUCTION

A Schiff base is a functional group that is made up of carbon nitrogen double bond. The nitrogen atoms are linked to an aryl group, not to the hydrogen atoms. The general formula for Schiff's base is R1R2C=N-R3.The R3 is an aryl that makes the Schiff base to be a stalime mine [2]. A Schiff base is derived from aniline. It can be synthesised from different compounds, such as an aromatic amine. It can also be synthesised from carbonyl compound by nucleophilic addition, thus forming a hemiaminal. Schiff bases are used in various experiments to carry out different activities including studying the properties of various complexes and materials. This is to ensure that the correct results are obtained. For instance, the Schiff bases are used in this experiment to study different properties of different complexes used in the experiment, including the ligands Hydroxyacetophenone Nitrogen hydroxide (HappNOH), haptn, salen and hapbn.

The aim of the experiment is to determine the effect of varying the Schiff's base on the electronic structure and molecular structure. This determines the effect of varying the Schiff base on the properties of Mn (III) complex. As part of the practical, several complexes of the general formula were prepared and characterised, that is the [MN (SB) X].In this case SB represents one of the tetradentane Schiff base. The X represents an anion.

The complexes used in the study were square pyramidal with axial chloride ligands. All ligands used formed solid adduct, however none were as effective as salen which produced a pure crystalline product. Additionally, the attempt to prepare the Mn(II) Schiff's base by reducing the MN(III) complex using aqueous Pyridine resulted in decomposition of the complex. The Manganese salen complex that was formed (Figure 1) was then used for further testing of Manganese properties. These included the infrared spectra, line broadening spectra and solubility tests in Dimethylsulfoxide (DMSO) and dimethylformamide (DMF) [2].

Figure 1:

[Mn(Salen)Cl] [3]

EXPERIMENTAL

MATERIALS

The aldehydes were obtained from Aldrich Chemical Company. The ligands were prepared from the aldehyde and ethytenediamine by the method of Diehl [1]. All other materials were reagent grade and used without further purification.

METHOD

A 95% ethanol solution (500 ml) of H2SB (0.02 moles) and 9.8 g of Mn(C2H302) 2 . 4H20 (0.04 moles) were refluxed in air for 3 hours. The reaction mixture was evaporated to dryness in a rotary evaporator. The residue was extracted with hot (~ 60 ° C) distilled water (500mL) and filtered. Solid KCl (37g) was added to the filtrate to give a 1 M solution. A brown-red solid precipitate formed immediately and was collected on a filter and air dried. The crude solid was recrystallised from acetone-diethyl ether and dried at ll0oC over P2O5 in vacuo. The yield of pure [Mn(SB)CI] was generally around 50% based on the ligand used. This procedure was repeated using the ligands salen, HappNOH, hapbn and haptn, in 50% proportions.

The solubility of the manganese complex was tested by adding dimethyl sulphoxide (DMSO) and ...