Organoantimony Dihydroperoxides: Synthesis, Crystal Structures, and Hydrogen Bonding Networks

Despite growing interest in the potential applications of p-block hydroperoxo complexes, the chemistry of inorganic hydroperoxides remains largely unexplored. For instance, single-crystal structures of antimony hydroperoxo complexes have not been reported to date. Herein, we present the synthesis of six triaryl and trialkylantimony dihydroperoxides [Me₃Sb(OOH)₂, Me₃Sb(OOH)₂·H₂O, Ph₃Sb(OOH)₂·0.75(C₄H₈O), Ph₃Sb(OOH)₂·2CH₃OH, pTol₃Sb(OOH)₂, pTol₃Sb(OOH)₂·2(C₄H₈O)], obtained by the reaction of the corresponding dibromide antimony(V) complexes with an excess of highly concentrated hydrogen peroxide in the presence of ammonia. The obtained compounds were characterized by single-crystal and powder X-ray diffraction, Fourier transform infrared and Raman spectroscopies, and thermal analysis. The crystal structures of all six compounds reveal hydrogen-bonded networks formed by hydroperoxo ligands. In addition to the previously reported double hydrogen bonding, new types of hydrogen-bonded motifs formed by hydroperoxo ligands were found, including infinite hydroperoxo chains. Solid-state density functional theory calculation of Me₃Sb(OOH)₂ revealed reasonably strong hydrogen bonding between OOH ligands with an energy of 35 kJ/mol. Additionally, the potential application of Ph₃Sb(OOH)₂·0.75(C₄H₈O) as a two-electron oxidant for the enantioselective epoxidation of olefins was investigated in comparison with Ph₃SiOOH, Ph₃PbOOH, t-BuOOH, and H₂O₂.

Electrochemical Behavior of Reduced Graphene Oxide Supported Germanium Oxide, Germanium Nitride, and Germanium Phosphide as Lithium-Ion Battery Anodes Obtained from Highly Soluble Germanium Oxide

Germanium and germanium-based compounds are widely used in microelectronics, optics, solar cells, and sensors. Recently, germanium and its oxides, nitrides, and phosphides have been studied as active electrode materials in lithium- and sodium-ion battery anodes. Herein, the newly introduced highly soluble germanium oxide (HSGO) was used as a versatile precursor for germanium-based functional materials. In the first stage, a germanium-dioxide-reduced graphene oxide (rGO) composite was obtained by complete precipitation of GeO2 nanoparticles on the GO from an aqueous solution of HSGO and subsequent thermal treatment in argon at low temperature. The composition of the composite, GeO2-rGO (20 to 80 wt.% of crystalline phase), was able to be accurately determined by the HSGO to GO ratio in the initial solution since complete deposition and precipitation were achieved. The chemical activity of germanium dioxide nanoparticles deposited on reduced graphene oxide was shown by conversion to rGO-supported germanium nitride and phosphide phases. The GeP-rGO and Ge3N4-rGO composites with different morphologies were prepared in this study for the first time. As a test case, composite materials with different loadings of GeO2, GeP, and Ge3N4 were evaluated as lithium-ion battery anodes. Reversible conversion–alloying was demonstrated in all cases, and for the low-germanium loading range (20 wt.%), almost theoretical charge capacity based on the germanium content was attained at 100 mA g−1 (i.e., 2595 vs. 2465 mAh g−1 for Ge3N4 and 1790 vs. 1850 mAh g−1 for GeP). The germanium oxide was less efficiently exploited due to its lower conversion reversibility.

Triphenyllead Hydroperoxide: A 1D Coordination Peroxo Polymer, Single-Crystal-to-Single-Crystal Disproportionation to a Superoxo/Hydroxo Complex, and Application in Catalysis

The synthesis, transformation, and application in catalysis of triphenyllead hydroperoxide, the first dioxygen lead complex, are described. Triphenyllead hydroperoxide is characterized by ²⁰⁷Pb nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and single-crystal X-ray diffraction, revealing the first one-dimensional (1D) coordination peroxo polymer. Photolytic isomorphous transformation of Ph₃PbOOH yields a mixed hydroxo/superoxo crystalline structure, the first nonalkali superoxo crystalline metal salt, which is stable up to 100 °C. Upon further photolysis, another isomorphous transformation of the superoxide to hydroxide is observed. These are the first single-crystal-to-single-crystal hydroperoxide-to-superoxide and then to hydroxide transformations reported to date. Photolysis of triphenyllead hydroperoxide yields two forms of superoxide-doped crystalline structures that are distinguished by widely different characteristic relaxation times. The use of Ph₃PbOOH as an easy-to-handle solid two-electron oxidant for the highly enantioselective epoxidation of olefins is described.

Crystalline Peroxosolvates: Nature of the Coformer, Hydrogen-Bonded Networks and Clusters, Intermolecular Interactions

Despite the technological importance of urea perhydrate (percarbamide) and sodium percarbonate, and the growing technological attention to solid forms of peroxide, fewer than 45 peroxosolvates were known by 2000. However, recent advances in X-ray diffractometers more than tripled the number of structurally characterized peroxosolvates over the last 20 years, and even more so, allowed energetic interpretation and gleaning deeper insight into peroxosolvate stability. To date, 134 crystalline peroxosolvates have been structurally resolved providing sufficient insight to justify a first review article on the subject. In the first chapter of the review, a comprehensive analysis of the structural databases is carried out revealing the nature of the co-former in crystalline peroxosolvates. In the majority of cases, the coformers can be classified into three groups: (1) salts of inorganic and carboxylic acids; (2) amino acids, peptides, and related zwitterions; and (3) molecular compounds with a lone electron pair on nitrogen and/or oxygen atoms. The second chapter of the review is devoted to H-bonding in peroxosolvates. The database search and energy statistics revealed the importance of intermolecular hydrogen bonds (H-bonds) which play a structure-directing role in the considered crystals. H2O2 always forms two H-bonds as a proton donor, the energy of which is higher than the energy of analogous H-bonds existing in isostructural crystalline hydrates. This phenomenon is due to the higher acidity of H2O2 compared to water and the conformational mobility of H2O2. The dihedral angle H-O-O-H varies from 20 to 180° in crystalline peroxosolvates. As a result, infinite H-bonded 1D chain clusters are formed, consisting of H2O2 molecules, H2O2 and water molecules, and H2O2 and halogen anions. H2O2 can form up to four H-bonds as a proton acceptor. The third chapter of the review is devoted to energetic computations and in particular density functional theory with periodic boundary conditions. The approaches are considered in detail, allowing one to obtain the H-bond energies in crystals. DFT computations provide deeper insight into the stability of peroxosolvates and explain why percarbamide and sodium percarbonate are stable to H2O2/H2O isomorphic transformations. The review ends with a description of the main modern trends in the synthesis of crystalline peroxosolvates, in particular, the production of peroxosolvates of high-energy compounds and mixed pharmaceutical forms with antiseptic and analgesic effects.

Identification of Barium Hydroxo-Hydroperoxostannate Precursor for Low-Temperature Formation of Perovskite Barium Stannate

A breakthrough "superoxide colloidal solution route" for low-temperature synthesis of barium and strontium stannate perovskites and their doped analogues was recently introduced. The synthesis starts from hydrogen peroxide-rich stannate solutions and yields a so-called "crystalline superoxide molecular cluster" that is converted by low temperature (<300 °C) to the respective perovskites. In this paper, the so-called "crystalline superoxide molecular cluster" is identified as a superoxide-free, barium trihydroxo(hydroperoxo)peroxostannate, BaSn(OH)₃(OOH)(OO) phase (BHHPS). EPR and Raman spectroscopy studies reveal the absence of superoxide in this crystalline phase. FTIR of the deuterated sample, ¹¹⁹Sn NMR, and elemental analysis uncovered the empirical formula, H₄O₇SnBa with two peroxides per each tin element. Rietveld refinement of the XRD confirms the BHHPS cubic phase with replacement of the perovskite oxygen atoms by the OH- and OOH-ligands and peroxobridging groups.

Mesoporous polycrystalline SnO2 framework synthesized by direct soft templating method for highly selective detection of NO2

SnO2 is one of the most studied oxide materials for gas sensing applications. Investigations have shown that SnO2 is sensitive to a wide range of gaseous compounds. However, its lack of selectivity remains an issue. Here, a mesoporous polycrystalline SnO2 framework was successfully synthesized using a soft templating method at ambient temperature and pressure. The prepared materials were characterized using x-ray diffraction analysis, high-resolution transmission electron microscopy, energy-dispersive x-ray spectroscopy, N2 sorption tests, and x-ray photoelectron spectroscopy. Gas sensing analyses were performed on two batches of the material calcined at 400 °C and 500 °C. The resultant materials were highly conductive at relatively low operating temperatures. The thermal annealing and operating temperatures of the materials had significant effects on their gas sensing response and selectivity. The structure calcined at 400 °C showed a very selective response of 407 to 1 ppm NO2. The superior sensing performance of the obtained mesoporous SnO2 framework is attributed to its small crystal size of 4-5 nm-less than double the thickness of the critical electron depletion layer-as well as its high surface area of 89 m2 g-1 and high pore volume of 0.12 cm3 g-1.

Crystalline Ammonium Peroxogermanate as a Waste-Free, Fully Recyclable Versatile Precursor for Germanium Compounds

High, nearly 100%, yield synthesis of ammonium peroxogermanate (APG), (NH₄)₆[Ge₆(μ-OO)₆(μ-O)₆(OH)₆]·6H₂O, is presented, and its crystal structure is determined by single crystal X-ray study. It comprises centrosymmetric hexanuclear peroxogermanate anions [Ge₆(μ-OO)₆(μ-O)₆(OH)₆]^6- with six μ-oxo- and six μ-peroxo groups forming negatively charged layers. The space between these layers is filled by ammonium cations and water molecules, forming a highly stable structure due to hydrogen bonding. Highly soluble macroporous amorphous germanium oxide (HSGO) is then synthesized by mild treatment of APG. The compound forms highly oversaturated metastable germanium oxide solution with a solubility of 100 g/L, over 20 times higher than the solubility of amorphous germanium oxide. HSGO solution is a versatile reagent that can react with basic and acidic reagents to give a diverse range of salts including, e.g., germanium sulfide, germanium hydrophosphate, and potassium germanate. In the absence of acid or base, the aqueous HSGO solution yields hexagonal germanium oxide under ambient conditions.

Vanadium Oxide Thin Film Formation on Graphene Oxide by Microexplosive Decomposition of Ammonium Peroxovanadate and Its Application as a Sodium Ion Battery Anode

Formation of vanadium oxide nanofilm-coated graphene oxide (GO) is achieved by thermally induced explosive disintegration of a microcrystalline ammonium peroxovanadate-GO composite. GO sheets isolate the microcrystalline grains and capture and contain the microexplosion products, resulting in the deposition of the nanoscale products on the GO. Thermal treatment of the supported nanofilm yields a sequence of nanocrystalline phases of vanadium oxide (V₃O₇, VO₂) as a function of temperature. This is the first demonstration of microexplosive disintegration of a crystalline peroxo compound to yield a nanocoating. The large number of recently reported peroxide-rich crystalline materials suggests that the process can be a useful general route for nanofilm formation. The V₃O₇@GO composite product was tested as a sodium ion battery anode and showed high charge capacity at high rate charge-discharge cycling (150 mAh g^-1 at 3000 mA g^-1 vs 300 mAh g^-1 at 100 mA g^-1) due to the nanomorphology of the vanadium oxide.

A solution-processed tin dioxide film applicable as a transparent and flexible humidity sensor

An all-solution-processed transparent tin oxide (SnO₂)-based humidity sensor was directly prepared on borosilicate glass (SnO₂–G) and a flexible polyethylene terephthalate (SnO₂–PET) substrate without using a template. The entire process included film deposition by a spin-spray process at 90 °C and subsequent hot water treatment (HWT) at 100 °C. The resistivity of the films dramatically decreased and had semiconductor characteristics after the HWT, even though the as-prepared SnO₂–G and SnO₂–PET samples were insulators. Based on the results, the variation of the resistivity could be attributed to the formation of a hydroxyl layer on the crystallized SnO₂ surface. With the help of the HWT on the SnO₂ films, the formation of tin hydroxyl derivatives provided mobile protons, which led to the variation of the electrical properties of SnO₂ at ambient conditions with different humidities. The sensitivity of the SnO₂–G-HWT and SnO₂–PET-HWT at 95% relative humidity (RH) was 35.2 and 3.5 times higher, respectively, than that at 5% RH. Both the sensitivity of the SnO₂–G-HWT and SnO₂–PET-HWT samples showed a good uptrend corresponding to the increase of RH at 20 ± 1 °C, and the response/recovery time of SnO₂–G-HWT and SnO₂–PET-HWT was 51/38 s and 69/47 s in the % RH range of 30–70% at 20 ± 1 °C, respectively.

An all-solution-processed transparent tin oxide (SnO₂)-based humidity sensor was directly prepared on borosilicate glass (SnO₂–G) and a flexible polyethylene terephthalate (SnO₂–PET) substrate without using a template.