title: Complex formation of neptunium(V) with 4-hydroxy-3-methoxybenzoic acid studied by time-resolved laser-induced fluorescence spectroscopy with ultra-short laser pulses.
abstract: The complex formation of neptunium(V) with 4-hydroxy-3-methoxybenzoic acid (vanillic acid) was studied by time-resolved laser-induced fluorescence spectroscopy with ultra-short laser pulses using the fluorescence properties of 4-hydroxy-3-methoxybenzoic acid. A 2:1 complex of neptunium(V) with 4-hydroxy-3-methoxybenzoic acid was found. The stability constant of this complex was determined to be logbeta(210) = 7.33 +/- 0.10 at an ionic strength of 0.1 mol/l (NaClO(4)) and at 21 degrees C. The determination of the stability constant required an investigation of the excited-state proton transfer of 4-hydroxy-3-methoxybenzoic acid over the whole pH range. It was realized that 4-hydroxy-3-methoxybenzoic acid undergoes excited-state reactions only at pH values below 5. At pH values above 5 stability constants can be determined without kinetic calculation of the proton transfer.
authors: Forschungszentrum Rossendorf, Institute of Radiochemistry, P.O. Box 510119, D-01314 Dresden, Germany. d.vulpius@fz-rossendorf.de
authors: D
authors: D
authors: Vulpius
authors: G
authors: G
authors: Geipel
authors: L
authors: L
authors: Baraniak
authors: G
authors: G
authors: Bernhard
mesh_terms: D006863:Hydrogen-Ion Concentration; D007477:Ions; D007700:Kinetics; D007834:Lasers; D008027:Light; D008956:Models, Chemical; D009405:Neptunium / Q000737:chemistry*; D011199:Potentiometry; D011522:Protons; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013696:Temperature; D013997:Time Factors; D014641:Vanillic Acid / Q000737:chemistry*
chemical_list: D007477:Ions; D011522:Protons; D009405:Neptunium; D014641:Vanillic Acid