Zoran Mazej

This study presents a detailed study on the effect of presence of 1,1,1,3,3,3‐hexafluoroisopropanol (HFIP) on redox‐mediated Diels–Alder reaction between anthracenes and chalcones induced by oxidation by Ag ^II SO ₄ . The introduction of even a minimal amount, 1% (v/v), of HFIP is shown to have a significant effect on the reaction rate. The optimization of the DA reaction protocol in the examined system leads to substantial rise of yields (up to 25 times) or reduction of reaction time (up to >100 times), allowing facile synthesis of cycloadducts from poorly active reactants which are otherwise difficult to obtain. Experimental and computational results point to the role of HFIP as the enhancement of solubilization of (Anth) ^+• through complexation of the [Ag ^I SO ₄ ] ⁻ counterion, while the alcohol itself does not interact strongly with radical cations involved in the reaction.

We investigate the electronic structure of AgF 2 , AgFBF 4 , AgF, and Ag 2 O using x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS) at the Ag L 3 edge. XAS results were compared with density functional theory computations of the spectra, allowing an identification of main features and an assessment of the theoretical approximations. Our RIXS measurements reveal that AgF 2 exhibits charge-transfer (CT) excitations and d d excitations, analogous to those observed in La 2 CuO 4 . We propose to use the ratio of d d to CT spectral weight as a measure of the covalence of the compounds and provide explicit equations for the weights as a function of the scattering geometry for crystals and powders. The measurements at the metal site L 3 edge and previous measurement in the ligand K edge reveal a striking similarity between the fluoride and cuprate materials, with fluorides somewhat more covalent than cuprates. These findings support the hypothesis that silver fluorides are an excellent platform to mimic the physics of cuprates, providing a promising avenue for exploring high- T c superconductivity and exotic magnetism in quasi-two-dimensional ( AgF 2 ) and quasi-one-dimensional ( AgFBF 4 ) materials.

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.

As Ag ²⁺ is such a powerful oxidizer, not many open-shell transition metal cations can resist its neighborhood. Here we introduce AgCoF ₅ , a rare representative of the transition metal–Ag ²⁺ fluoride family.

In fluorides, the M⁴⁺ cations of M = Ti, V, Cr, Mn, Ge, Sn, and Pb favour the octahedral coordination of six F ligands. Some examples of M⁴⁺ with larger cations (M = Zr, Hf, W) in octahedral coordination are also known. If not enough F ligands are available to have isolated M^IVF₆ octahedra, they must share their F ligands. The crystal structures of such fluoride metalates (IV) show the variety of possible structural motifs of the zero-dimensional oligomeric anions [M₂F₁₁]³⁻ (M = Ti, Cr), [M₃F₁₅]³⁻ (M = Zr, Hf), [M₃F₁₆]⁴⁻ (M = Ge), [M₄F₁₈]²⁻ (M = Ti, W), [M₄F₁₉]³⁻ (M = Ti), [M₄F₂₀]⁴⁻ (M = Ti), [M₅F₂₃]³⁻ (M = Ti), [M₆F₂₇]³⁻ (M = Ti), [M₆F₂₈]⁴⁻ (M = Ti), [M₈F₃₆]⁴⁻ (M = Ti, Mn), [M₁₀F₄₅]⁵⁻ (M = Ti) to one-dimensional chains ([MF₅]⁻)_∞ (M = V, Ti, Cr, Ge, Sn, Pb), double chains ([M₂F₉]⁻)_∞ (M = Ti, Mn), columns ([M₃F₁₃]⁻)_∞ (M = Ti), ([M₄F₁₉]³⁻)_∞ (M = Ti), ([M₇F₃₀]²⁻)_∞ (M = Ti), ([M₉F₃₈]²⁻)_∞) (M = Ti), two-dimensional layers ([M₂F₉]⁻)_∞ (M = Cr), ([M₈F₃₃]⁻)_∞ (M = Ti), and three-dimensional ([M₆F₂₇]³⁻)_∞ (M = Ti) architectures. A discrete monomeric [M₂F₉]⁻ anion with two M^IVF₆ octahedra sharing a common face has not yet been experimentally demonstrated, while two examples containing discrete dimeric [M₂F₁₀]²⁻ anions (M = Ti) with two M^IVF₆ octahedra sharing an edge are still in question.

DFT calculations and Raman spectroscopy measurements indicate that pressure induces in Na ₂ CuF ₄ a phase transition from variants of the Sr ₂ PbO ₄ post-perovskite structure to a novel Th ₃ P ₄ -like polymorph whose properties closely mimic those of Mg ₂ SiO ₄ .