Elaboration of a Highly Porous Ru^II,II Analogue of HKUST‑1

When the dinuclear Ru^II,II precursor [Ru₂(OOCCH₃)₄] is employed under redox-inert conditions, a Ru^II,II analogue of HKUST-1 was successfully prepared and characterized as a phase-pure microcrystalline powder. X-ray absorption near-edge spectroscopy confirms the oxidation state of the Ru centers of the paddle-wheel nodes in the framework. The porosity of 1371 m²/mmol of Ru^II,II-HKUST-1 exceeds that of the parent compound HKUST1 (1049 m²/ mmol)

How Strong Is the Hydrogen Bond in Hybrid Perovskites?

Hybrid organic–inorganic perovskites represent a special class of metal–organic framework where a molecular cation is encased in an anionic cage. The molecule–cage interaction influences phase stability, phase transformations, and the molecular dynamics. We examine the hydrogen bonding in four AmBX₃ formate perovskites: [Am]­Zn­(HCOO)₃, with Am⁺ = hydrazinium (NH₂NH₃⁺), guanidinium (C­(NH₂)₃⁺), dimethylammonium (CH₃)₂NH₂⁺, and azetidinium (CH₂)₃NH₂⁺. We develop a scheme to quantify the strength of hydrogen bonding in these systems from first-principles, which separates the electrostatic interactions between the amine (Am⁺) and the BX₃^– cage. The hydrogen-bonding strengths of formate perovskites range from 0.36 to 1.40 eV/cation (8–32 kcalmol^–1). Complementary solid-state nuclear magnetic resonance spectroscopy confirms that strong hydrogen bonding hinders cation mobility. Application of the procedure to hybrid lead halide perovskites (X = Cl, Br, I, Am⁺ = CH₃NH₃⁺, CH­(NH₂)₂⁺) shows that these compounds have significantly weaker hydrogen-bonding energies of 0.09 to 0.27 eV/cation (2–6 kcalmol^–1), correlating with lower order–disorder transition temperatures

Wet Chemical Synthesis and a Combined X-ray and Mössbauer Study of the Formation of FeSb₂ Nanoparticles

Understanding how solids form is a challenging task, and few strategies allow for elucidation of reaction pathways that are useful for designing the synthesis of solids. Here, we report a powerful solution-mediated approach for formation of nanocrystals of the thermoelectrically promising FeSb₂ that uses activated metal nanoparticles as precursors. The small particle size of the reactants ensures minimum diffusion paths, low activation barriers, and low reaction temperatures, thereby eliminating solid–solid diffusion as the rate-limiting step in conventional bulk-scale solid-state synthesis. A time- and temperature-dependent study of formation of nanoparticular FeSb₂ by X-ray powder diffraction and iron-57 Mössbauer spectroscopy showed the incipient formation of the binary phase in the temperature range of 200–250 °C

Role of Amine–Cavity Interactions in Determining the Structure and Mechanical Properties of the Ferroelectric Hybrid Perovskite [NH₃NH₂]Zn(HCOO)₃

Dense formate frameworks with a perovskite-like architecture exhibit multiferroic behavior and tunable mechanical properties. In such materials, interactions between the protonated amine and the metal–formate cavity have a large impact on the mechanical properties. We use complementary single-crystal X-ray diffraction and ¹H solid state nuclear magnetic resonance spectroscopy to investigate amine–cavity interactions in [NH₃NH₂]­Zn­(HCOO)₃. The results suggest that these interactions can be described as salt bridges similar to those in proteins and artificially synthesized helical polymers, where ionic interactions and hydrogen bonds are present at the same time. Nanoindentation and high-pressure single-crystal X-ray diffraction were used to study the mechanical properties of [NH₃NH₂]­Zn­(HCOO)₃, yielding elastic moduli of <i>E</i>₀₀₁ = 26.5 GPa and <i>E</i>₁₁₀ = 24.6 GPa and a bulk modulus of <i>K</i> = 19 GPa. The mechanical properties suggest that, despite the relatively low packing density of [NH₃NH₂]­Zn­(HCOO)₃, the amine–cavity interactions strengthen the framework significantly in comparison with related materials

Synthesis and Properties of a Lead-Free Hybrid Double Perovskite: (CH₃NH₃)₂AgBiBr₆

The discovery of lead-free hybrid double perovskites provides a viable approach in the search for stable and environmentally benign photovoltaic materials as alternatives to lead-containing systems such as MAPbX₃ (X = Cl, Br, or I). Following our recent reports of (MA)₂KBiCl₆ and (MA)₂TlBiBr₆, we have now synthesized a hybrid double perovskite, (MA)₂AgBiBr₆, that has a low band gap of 2.02 eV and is relatively stable and nontoxic. Its electronic structure and mechanical and optical properties are investigated with a combination of experimental studies and density functional theory calculations

Synthesis and Properties of a Lead-Free Hybrid Double Perovskite: (CH₃NH₃)₂AgBiBr₆

The discovery of lead-free hybrid double perovskites provides a viable approach in the search for stable and environmentally benign photovoltaic materials as alternatives to lead-containing systems such as MAPbX₃ (X = Cl, Br, or I). Following our recent reports of (MA)₂KBiCl₆ and (MA)₂TlBiBr₆, we have now synthesized a hybrid double perovskite, (MA)₂AgBiBr₆, that has a low band gap of 2.02 eV and is relatively stable and nontoxic. Its electronic structure and mechanical and optical properties are investigated with a combination of experimental studies and density functional theory calculations