Electron-overdoped Ag(II)F2: mixed-valence fluorides Ag(I)Ag(II)F3 and Ag(I)2Ag(II)F4

We have successfully prepared two novel mixed-valence compounds of silver, Ag(I)Ag(II)F3 and Ag(I)2Ag(II)F4. They may be considered to be long-sought strongly electron-overdoped Ag(II)F2. Their crystal structures indicate that both belong to the Class I (mixed-valence) family with frozen Ag(I) and Ag(II) valences. The measured Raman spectra are well-correlated with the theoretical ones. Density functional theory calculations reveal their smaller fundamental band gaps as compared to pristine AgF2, due to the presence of Ag(I) states in the valence band.