Acta Pharm. 54 (2004) 119-131

Stability of the complexes of some lanthanides with coumarin derivatives. II. Neodymium(III)-acenocoumarol

IRENA P. KOSTOVA,^1* ILIA I. MANOLOV² and  MARITZA K. RADULOVA³

irenakostova@yahoo.com

¹Department of Chemistry, Faculty of Pharmacy, Medical University, Sofia 1000, Bulgaria
²Department of Industrial Pharmacy, Faculty of Pharmacy, Medical University, Sofia 1000, Bulgaria
³ Department of Technology, Faculty of Pharmacy, Medical University, Sofia 1000, Bulgaria

A complex of neodymium(III) with 4-hydroxy-3-[1-(4-nitrophenyl)-3-oxobutyl]-2H-1-benzopyran-2-one (acenocoumarol) was synthesized by mixing water solutions of neodymium(III) nitrate and the ligand (metal to ligand molar ratio of 1:3). The complex was characterized and identified by elemental analysis, conductivity, IR, ¹H NMR and mass spectral data. DTA and TGA were applied to study the composition of the compound. Elemental and mass spectral analysis of the complex indicated the formation of a compound of the composition NdR₃x6H₂O, where R = C₁₉H₁₄NO₆^-. The reaction of neodymium(III) with 4-hydroxy-3-[1-(4-nitrophenyl)-3-oxobutyl]-2H-1-benzopyran-2-one was studied in detail by the spectrophotometric method. The stepwise formation of three complexes, vis., NdR²⁺, NdR₂⁺ and NdR₃ was established in the pH region studied (pH 3.0-7.5). The equilibrium constants for 1:1, 1:2 and 1:3 complexes were determined to be log K₁ = 6.20 ± 0.06; log K₂ = 3.46 ± 0.07 and log K₃ = 2.58 ± 0.05, respectively.

Keywords: neodymium(III) complex, 4-hydroxy-3-[1-(4-nitrophenyl)-3-oxobutyl]-2H-1-benzopyran-2-one, stability