Negative-ion photoelectron spectroscopy of the copper-aspartic acid anion and its hydrated complexes

Xiang Li (1) , Haopeng Wang (1) , K. H. Bowen (1) , Ana Martinez (2) , Jean-Yves Salpin (3) , Jean-Pierre Schermann (4)

1 BOWEN'S GROUP - Department of Chemistry
2 Instituto de Investigaciones en Materiales
3 LAMBE - Laboratoire Analyse et Modélisation pour la Biologie et l'Environnement
4 LPL - Laboratoire de Physique des Lasers

Negative ions of copper-aspartic acid Cu(Asp)⁻ and its hydrated complexes have been produced in the gas phase and studied by anion photoelectron spectroscopy. The vertical detachment energies (VDE) of Cu(Asp)⁻ and Cu(Asp)⁻(H₂O)_1,2 were determined to be 1.6, 1.95, and 2.20 eV, respectively. The spectral profiles of Cu(Asp)⁻(H₂O)1 and Cu(Asp)⁻(H₂O)₂ closely resembled that of Cu(Asp)⁻, indicating that hydration had not changed the structure of Cu(Asp)⁻ significantly. The successive shifts to higher electron binding energies by the spectra of the hydrated species provided measures of their stepwise solvation energies. Density functional calculations were performed on anionic Cu(Asp)⁻ and on its corresponding neutral. The agreement between the calculated and measured VDE values implied that the structure of the Cu(Asp)⁻ complex originated with a zwitterionic form of aspartic acid in which a copper atom had inserted into the N–H bond.

Domaines: Chimie-Physique [physics.chem-ph]

Xiang Li, Haopeng Wang, K. H. Bowen, Ana Martinez, Jean-Yves Salpin, et al.. Negative-ion photoelectron spectroscopy of the copper-aspartic acid anion and its hydrated complexes. Journal of Chemical Physics, 2010, 133 (8), pp.084303. ⟨10.1063/1.3466923⟩. ⟨hal-00514244⟩