Solvation and Speciation of Cobalt(II). A Theoretical X-Ray Absorption and RIXS Study

Abstract

<p>The X-ray spectroscopic signatures of solvated Co<sup>2+</sup> ions mimicking the aqueous solution of CoCl<sub>2</sub> are investigated accounting for multiconfigurational as well as spin-orbit coupling effects. To this end the RASSCF/RASSI methodology with second order corrections due to dynamical correlation (RASPT2) is employed. Emphasis is put on the identification of spectral signatures of different species in octahedral, [Co(H<sub>2</sub>O)<sub>6</sub><sub>-</sub><sub>x</sub>Cl<sub>x</sub>]<sup>(2</sup><sup>-</sup><sup>x)+</sup>, and tetrahedral, [Co(H<sub>2</sub>O)<sub>4</sub><sub>-</sub><sub>x</sub>Cl<sub>x</sub>]<sup>(2</sup><sup>-</sup><sup>x)+</sup>,coordination. X-ray absorption spectra show distinct differences in the L<sub>3</sub> band only. Here, the best agreement is obtained for the hexa-aqua complex [Co(H<sub>2</sub>O)<sub>6</sub>]<sup>2+</sup>. For better identification it is proposed to use RIXS spectroscopy, which shows pronounced species-dependent inelastic features.</p><p><br></p>

Ethylammonium nitrate enhances the extraction of transition metal nitrates by tri‐n‐butyl phosphate (TBP)

“…In pure EAN, the species is [Co(NO 3 ) 4 ] 2− , as discussed in Section 3.2. In water, the species is known to be [Co(H 2 O) 6 ] + 30‐32 . As the water content increased, the spectra gradually shifted and the intensity decreased.…”

“…The UV-Vis absorption spectra of Co(II) in water, EAN, and their mixtures are presented inFigure 2. The Co(II) species in water is known to be [Co (H 2 O 6 )] 2+ [30][31][32]. In EAN, the spectrum of Co(II) has a similar shape as that of [Co(H 2 O 6 )] 2+ , but it is red-shifted for 31 nm and the intensity is much higher.…”