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.Neodimijev(III) kompleks s acenokumarolom pripravljen je mješajući vodenu otopinu neodimijevog(III) nitrata i liganda u molarnom omjeru metala i liganda 1:3. Kompleks je karakteriziran i identificiran elementarnom analizom, konduktometrijom, IR, 1H NMR, masenom spektroskopijom, DTA i TGA. Analize ukazuju na sastav kompleksa NdR3.6H2O, gdje je R = C19H14NO6-. Reakcija neodimij(III) s acenokumarolom praćena je spektrofotometrijski. U pH području 3,0 do 7,5 utvrđeno je postupno stvaranje triju kompleksa, NdR2+, NdR2+ i NdR3. Konstante ravnoteže za 1:1, 1:2 i 1:3 komplekse bile su log K1 = 6,20 0,06, log K2 = 3,46 0,07, odnosno log K3 = 2,58 0,05
