Cd(II) complexes with N-acetylcysteine (H2NAC), selenourea (SeU), and thiourea (TU) in solution were investigated using NMR and XAS spectroscopic techniques.
From the Cd K-edge EXAFS spectrum of a Cd(II)-SeU methanol solution at 200 K containing CCd(II)=0.1 M and CSeU≥0.4 M, the local structure of a Cd(SeU)4 tetrahedral species with Cd-Se bond distance of was determined. NMR measurement of this solution shows a single sharp peak at 578 ppm, which is in agreement with the reported speciation. For Cd(II)-SeU solutions with a lower concentration of selenourea, a mixture of species was observed.
NMR spectra of Cd(II)-TU solutions revealed a mixture of species at low TU/Cd(II) mole ratios. The structures of these complexes were determined using Cd K-edge EXAFS spectroscopy, LIII-edge XANES, and NMR.
Cd(II)-N-acetylcysteine solutions with CCd(II) = 0.1 M and NAC/Cd(II) mole ratios of 2.0–20.0 at pH = 7.5 and 11.0 have been investigated. They show a mixture of CdS3O3, CdS3O, and CdS4 species at low NAC concentration and species at high NAC concentration.