Europium-151 and iron-57 nuclear resonant vibrational spectroscopy of naturally abundant KEu(iii)Fe(ii)(CN)₆ and Eu(iii)Fe(iii)(CN)₆ complexes

Abstract

We have measured and analyzed the first combined 151Eu and 57Fe nuclear resonant vibrational spectroscopy (NRVS) for naturally abundant KEu(III)[Fe(II)(CN)6] and Eu(III)[Fe(III)(CN)6] complexes. Comparison of the observed 151Eu vs. 57Fe...

X-ray and Nuclear Spectroscopies to Reveal the Element-Specific Oxidation States and Electronic Spin States for Nanoparticulated Manganese Cyanidoferrates and Analogs

“…For example, it is one of the most important medications on the World Health Organization's List of Essential Medicines [21]. In general, it has a chemical formula of Fe III 4 [Fe II (CN) 6 ] 3 •xH 2 O, with a cubic crystal lattice which has an atomic arrangement of -Fe II -C-N-Fe III -N-C-Fe II -in each dimension (similar to those shown in the references [19,20,22]). A quarter of Fe(II) centers along with CN − ions have to be absent from the crystal lattice in order to maintain a ratio of Fe(III):[Fe II (CN) 6 ] 4− = 4:3 to realize the electrical neutrality of PB [23].…”

“…In chemistry and bioinorganic chemistry, for example, this technique has uncovered Fe-S/P/Cl, Fe-CO/CN/NO and Fe-H/D vibrational modes inside various inorganic complexes as well as dilute iron enzymes [28], and has thus become an excellent pinpointing tool to study iron-specific electronic and structural properties, including iron oxidation state(s) and coordination environments. For PB-like compounds, it can pinpoint the features attributable to the N-bound hs-Fe(III) or those to the C-bound ls-Fe(II) [22,28].…”

“…In comparison, KFe[Co(CN) 6 ] had an hs-Fe(II) bound to the in the N position and an ls-Co(III) bound to the C position. For NRVS, 57 Fe labelled (NH 4 ) 2 Mg [ 57 Fe(CN) 6 ] and K 57 Fe[Co(CN) 6 ] were first presented as the two standards to illustrate the nature of the two "peaks" in the natural PB NRVS [22,28]. Then, non-labelled K 2 Mn[Fe(CN) 6 ] was measured with regional NRVS where only the energy regions around the resonant peak and the Fe-CN vibrational peak were measured [22,28].…”

“…For NRVS, 57 Fe labelled (NH 4 ) 2 Mg [ 57 Fe(CN) 6 ] and K 57 Fe[Co(CN) 6 ] were first presented as the two standards to illustrate the nature of the two "peaks" in the natural PB NRVS [22,28]. Then, non-labelled K 2 Mn[Fe(CN) 6 ] was measured with regional NRVS where only the energy regions around the resonant peak and the Fe-CN vibrational peak were measured [22,28]. For discussion, the previously measured regional spectra for KGd[Fe(CN) 6 ] and KEu[Fe(CN) 6 ] [22] are also cited and compared with K 2 Mn[Fe(CN) 6 ].…”

“…Then, non-labelled K 2 Mn[Fe(CN) 6 ] was measured with regional NRVS where only the energy regions around the resonant peak and the Fe-CN vibrational peak were measured [22,28]. For discussion, the previously measured regional spectra for KGd[Fe(CN) 6 ] and KEu[Fe(CN) 6 ] [22] are also cited and compared with K 2 Mn[Fe(CN) 6 ]. From the NRVS results, we concluded that the nanoparticulated manganese cyanidoferrates K 2 Mn[Fe(CN) 6 ] as well as KGd[Fe(CN) 6 ] and KEu[Fe(CN) 6 ] [22] have an ls-Fe(II) which occupies the C-bound position in the [Fe(CN) 6 ] 4− ion while the complexed Fe in K 57 Fe[Co(CN) 6 ] has an hs-Fe(II) which takes the N-bound position to the [Co(CN) 6 ] 3− ion.…”