Raman, IR, UV-vis and EPR characterization of two copper dioxolene complexes derived from L-dopa and dopamine.
The anionic complexes [Cu(L(1-))3](1-), L(-)=dopasemiquinone or L-dopasemiquinone, were prepared and characterized. The complexes are stable in aqueous solution showing intense absorption bands at ca. 605 nm for Cu(II)-L-dopasemiquinone and at ca. 595 nm for Cu(II)-dopasemiquinone in the UV-vis spectra, that can be assigned to intraligand transitions. Noradrenaline and adrenaline, under the same reaction conditions, did not yield Cu-complexes, despite the bands in the UV region showing that noradrenaline and adrenaline were oxidized during the process. The complexes display a resonance Raman effect, and the most enhanced bands involve ring modes and particularly the nuCC+nuCO stretching mode at ca. 1384 cm(-1). The free radical nature of the ligands and the oxidation state of the Cu(II) were confirmed by the EPR spectra that display absorptions assigned to organic radicals with g=2.0005 and g=2.0923, and for Cu(II) with g=2.008 and g=2.0897 for L-dopasemiquinone and dopasemiquinone, respectively. The possibility that dopamine and L-dopa can form stable and aqueous-soluble copper complexes at neutral pH, whereas noradrenaline and adrenaline cannot, may be important in understanding how Cu(II)-dopamine crosses the cellular membrane as proposed in the literature to explain the role of copper in Wilson disease.
Laboratory of Environmental Physical Chemistry, Department of Chemistry, CCE, Londrina State University, Londrina, PR 86051-990, Brazil. barreto@uel.br
Wagner J
WJ
Barreto
Sônia R G
SR
Barreto
Rômulo A
RA
Ando
Paulo S
PS
Santos
Eduardo
E
DiMauro
Thiago
T
Jorge
D002725:Chloroform / Q000737:chemistry; D003300:Copper / Q000737:chemistry*; D004298:Dopamine / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D004837:Epinephrine / Q000032:analysis; D005609:Free Radicals; D006863:Hydrogen-Ion Concentration; D007980:Levodopa / Q000032:analysis*; D008024:Ligands; D008670:Metals / Q000737:chemistry; D009638:Norepinephrine / Q000032:analysis; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet / Q000379:methods*; D013059:Spectrum Analysis, Raman / Q000379:methods*
D005609:Free Radicals; D008024:Ligands; D008670:Metals; D007980:Levodopa; D003300:Copper; D002725:Chloroform; D010100:Oxygen; D004298:Dopamine; D009638:Norepinephrine; D004837:Epinephrine