Lanthanide complexes of D-penicillamine: formation constants, spectral and thermal properties

Abstract

The complex-formation of lanthanide(III) elements with D-penicillamine have been investigated in acidic and neutral media. The macroscopic protonation constants of the ligand and the formation constants of [Ln.Pen]+, [Ln.Pen2]−, [Ln.Pen.OH] and [Ln.Pen.(OH)2]− complexes were determined from pH-metric data using the BEST computer program. Elemental analyses of the solid complexes indicate formation of 1 : 1 metal : ligand species. The binding sites in the complexes with the possible role of –COO−, –NH2 and –SH groups in the coordination have been discussed using infrared data. The complexes decompose in four steps as shown by their t.g. and d.t.a. analyses. A mechanism of decomposition is proposed which is supported by mass spectral data.