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.
Barreto
Wagner J
WJ
Laboratory of Environmental Physical Chemistry, Department of Chemistry, CCE, Londrina State University, Londrina, PR 86051-990, Brazil. barreto@uel.br
Barreto
Sônia R G
SR
Ando
Rômulo A
RA
Santos
Paulo S
PS
DiMauro
Eduardo
E
Jorge
Thiago
T
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