Structural Study on 2,2′-(Methylimino)bis(N,N-Dioctylacetamide) Complex with Re(VII)O4- and Tc(VII)O4- by 1H NMR, EXAFS, and IR Spectroscopy


Structural Study on 2,2′-(Methylimino)bis(N,N-Dioctylacetamide) Complex with Re(VII)O4- and Tc(VII)O4- by 1H NMR, EXAFS, and IR Spectroscopy

Saeki, M.; Sasaki, Y.; Nakai, A.; Ohashi, A.; Banerjee, D.; Scheinost, A. C.; Foerstendorf, H.

The structures of the complex of 2,2'-(methylimino)bis(N,N-dioctylacetamide) (MIDOA) with M-(VII)O-4(-) (M = Re and Tc), which were prepared by liquid-liquid solvent extraction, were investigated by using H-1 nuclear magnetic resonance (NMR), extended X-ray absorption fine structure (EXAFS), and infrared (IR) spectroscopy. The H-1 NMR spectra of the complex of MIDOA with Re(VII)O-4(-) prepared in the organic solution suggest the transfer of a proton from aqueous to organic solution and the formation of the H(+)MIDOA ion. The EXAFS spectra of the complexes of H(+)MIDOA with Re(VII)O-4(-) and Tc(VII)O-4(-) show only the M-O coordination of the aquo complexes, suggesting that the chemical state of M(VII)O-4(-) was unchanged during the extraction process. The results from H-1 NMR and EXAFS, therefore, provide evidence of M(VII)O-4(-)center dot center dot center dot H(+)MIDOA complex formation in the organic solution. The IR spectra of Re(VII)O-4(-)center dot center dot center do!
t H(+)MIDOA and Tc(VII)O-4(-)center dot center dot center dot H(+)MIDOA were analyzed based on the structures and the IR spectra that were calculated at the B3LYP/cc-pVDZ level. Comparison of the observed and calculated IR spectra demonstrates that an intramolecular hydrogen bond is formed in H(+)MIDOA, and the M(VII)O-4(-) ion interacts with H(+)MIDOA through multiple C-H-n center dot center dot center dot O hydrogen bonds.

Keywords: liquid-liquid solvent extraction; solvent extraction process; Complexation; DFT

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Publ.-Id: 16767