A new complex of manganese(II) with l-α-alanine: structure, spectroscopy and thermal study

Abstract

A polynuclear manganese(II) complex of l-α-alanine of the formula [Mn 4(ala) 4Cl 7(H 2O) 5]Cl·3H 2O (where ala= l-α-alanine) has been synthesized and characterized. An X-ray crystallographic study shows that the polymer consists of double linear chains. One chain contains alternately located Mn(1) and Mn(2) ions, and the other chain is built of Mn(3) and Mn(4) ions. Each independent manganese(II) ion is in an octahedral arrangements. Mn(1), Mn(2) and Mn(3) atoms display the same coordination environment being surrounded by two carboxylate oxygen atoms of α-alanine molecules, three chloride ions and one aqua ligand. In the coordination octahedron of the Mn(4) atom one chloride ion is replaced by a water molecule. In chains Mn(II) ions are joined alternately by a chloride ion or by two carboxylate bridges from different α-alanine molecules and one Cl − ion. Three non-coordinated water molecules and one chloride ion are located between the chains. The crystal structure is stabilized by an extensive system of hydrogen bonds. Thermogravimetric analysis shows this complex is stable to 353 K. Upon heating the complex loses molecules of water and is transformed into the suitable oxides. The IR spectra of free ligand and complex have been discussed.