Hydrogen Peroxide Insular Dodecameric and Pentameric Clusters in Peroxosolvate Structures

Synergism of primary and secondary interactions in a crystalline hydrogen peroxide complex with tin

Despite the significance of H2O2-metal adducts in catalysis, materials science and biotechnology, the nature of the interactions between H2O2 and metal cations remains elusive and debatable. This is primarily due to the extremely weak coordinating ability of H2O2, which poses challenges in characterizing and understanding the specific nature of these interactions. Herein, we present an approach to obtain H2O2-metal complexes that employs neat H2O2 as both solvent and ligand. SnCl4 effectively binds H2O2, forming a SnCl4(H2O2)2 complex, as confirmed by 119Sn and 17O NMR spectroscopy. Crystalline adducts, SnCl4(H2O2)2·H2O2·18-crown-6 and 2[SnCl4(H2O2)(H2O)]·18-crown-6, are isolated and characterized by X-ray diffraction, providing the complete characterization of the hydrogen bonding of H2O2 ligands including geometric parameters and energy values. DFT analysis reveals the synergy between a coordinative bond of H2O2 with metal cation and its hydrogen bonding with a second coordination sphere. This synergism of primary and secondary interactions might be a key to understanding H2O2 reactivity in biological systems.

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.

Peroxosolvate discovery method leads to first cocrystal with three energetic components

In spite of their exceptional performance, energetic peroxosolvates are rare. Research in this area is slowed by the poor availibility of concentrated hydrogen peroxide solutions. Presented here is an efficient peroxosolvate discovery method that is applied in the discovery of the first ternary cocrystal comprising only energetic components.

Fast Quantum Approach for Evaluating the Energy of Non-Covalent Interactions in Molecular Crystals: The Case Study of Intermolecular H-Bonds in Crystalline Peroxosolvates

Energy/enthalpy of intermolecular hydrogen bonds (H-bonds) in crystals have been calculated in many papers. Most of the theoretical works used non-periodic models. Their applicability for describing intermolecular H-bonds in solids is not obvious since the crystal environment can strongly change H-bond geometry and energy in comparison with non-periodic models. Periodic DFT computations provide a reasonable description of a number of relevant properties of molecular crystals. However, these methods are quite cumbersome and time-consuming compared to non-periodic calculations. Here, we present a fast quantum approach for estimating the energy/enthalpy of intermolecular H-bonds in crystals. It has been tested on a family of crystalline peroxosolvates in which the H∙∙∙O bond set fills evenly (i.e., without significant gaps) the range of H∙∙∙O distances from ~1.5 to ~2.1 Å typical for strong, moderate, and weak H-bonds. Four of these two-component crystals (peroxosolvates of macrocyclic ethers and creatine) were obtained and structurally characterized for the first time. A critical comparison of the approaches for estimating the energy of intermolecular H-bonds in organic crystals is carried out, and various sources of errors are clarified.

Comparison of Proton Acceptor and Proton Donor Properties of H2O and H2O2 in Organic Crystals of Drug-like Compounds: Peroxosolvates vs. Crystallohydrates

Two new peroxosolvates of drug-like compounds were synthesized and studied by a combination of X-ray crystallographic, Raman spectroscopic methods, and periodic DFT computations. The enthalpies of H-bonds formed by hydrogen peroxide (H₂O₂) as a donor and an acceptor of protons were compared with the enthalpies of analogous H-bonds formed by water (H₂O) in isomorphic (isostructural) hydrates. The enthalpies of H-bonds formed by H₂O₂ as a proton donor turned out to be higher than the values of the corresponding H-bonds formed by H₂O. In the case of H₂O₂ as a proton acceptor in H-bonds, the ratio appeared reversed. The neutral O∙∙∙H-O/O∙∙∙H-N bonds formed by the lone electron pair of the oxygen atom of water were the strongest H-bonds in the considered crystals. In the paper, it was found out that the low-frequency Raman spectra of isomorphous crystalline hydrate and peroxosolvate of N-(5-Nitro-2-furfurylidene)-1-aminohydantoin are similar. As for the isostructural hydrate and peroxosolvate of the salt of protonated 2-amino-nicotinic acid and maleic acid monoanion, the Raman spectra are different.

Non-covalent interactions of the hydroperoxo group in crystalline adducts of organic hydroperoxides and their potassium salts

X-ray diffraction of three new stable cocrystals of potassium salts of organic hydroperoxides with molecular hydroperoxides reveals strong charge-assisted ROO−⋯HOOR H-bonds.

Novel peroxosolvates of tetraalkylammonium halides: the first case of layers containing hydrogen-bonded peroxide molecules

The structures of Et4N+Cl−·2(H2O2) and Et4N+Br−·2(H2O2) formed by globose Et4N+ cations are the first examples of peroxosolvates with 2D layers containing H-bonded peroxides.

An H2 O2 Molecule Stabilized inside Open-Cage C60 Derivatives by a Hydroxy Stopper

An H₂ O₂ molecule was isolated inside hydroxylated open-cage fullerene derivatives by mixing an H₂ O₂ solution with a precursor molecule followed by reduction of one of carbonyl groups on its orifice. Depending on the reduction site, two structural isomers for H₂ O₂ @open-fullerenes were obtained. A high encapsulation ratio of 81 % was attained at low temperature. The structures of the peroxosolvate complexes thus obtained were studied by ¹ H NMR spectroscopy, X-ray analysis, and DFT calculations, showing strong hydrogen bonding between the encapsulated H₂ O₂ and the hydroxy group located at the center of the orifice. This OH group was found to act as a kinetic stopper, and the formation of the hydrogen bonding caused thermodynamic stabilization of the H₂ O₂ molecule, both of which prevent its escape from the cage. One of the peroxosolvates was isolated by HPLC, affording H₂ O₂ @open-fullerene with 100 % encapsulation ratio, likely due to the intramolecular hydrogen-bonding interaction.

The crystal structure of 2-amino-3-carboxypyridin-1-ium iodide hemihydrate, C6H8IN2O2.5

C6H8IN2O2.5, monoclinic, P2/n (no. 13), a = 9.8300(4) Å, b = 5.3338(2) Å, c = 17.4040(8) Å, β = 105.493(2)°, V = 879.36(6) Å3, Z = 2, R gt (F) = 0.0139, wR ref(F 2) = 0.0306, T = 150(2) K.

Efficient capturing of hydrogen peroxide in dilute aqueous solution by co-crystallization with amino acids

X-ray structure analyses of co-crystals of H2O2 and l-Phe, dl-Phe, or dl-Asp prepared in a dilute aqueous solution (30 wt%) indicated that multi-layer motifs including water molecule is important for highly efficient H2O2 capture in dilute solutions.

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.

dl-Piperidinium-2-carboxyl-ate bis-(hydrogen peroxide): unusual hydrogen-bonded peroxide chains

The title compound, C6H11NO2·2H2O2, is the richest (by molar ratio) in hydrogen peroxide among the peroxosolvates of aliphatic α-amino acids. The asymmetric unit contains a zwitterionic pipecolinic acid mol-ecule and two hydrogen peroxide mol-ecules. The two crystallographically independent hydrogen peroxide mol-ecules form a different number of hydrogen bonds: one forms two as donor and two as acceptor ([2,2] mode) and the other forms two as donor and one as acceptor ([2,1] mode). The latter hydrogen peroxide mol-ecule forms infinite hydrogen-bonded hydro-peroxo chains running along the c-axis direction, which is unusual for aliphatic α-amino acid peroxosolvates.

Stabilization of hydrogen peroxide by hydrogen bonding in the crystal structure of 2-aminobenzimidazole perhydrate

2-Aminobenzimidazole peroxosolvate – the third H₂O₂ crystalline adduct stabilized with the maximum possible number of hydrogen bonds formed by one hydrogen peroxide molecule.

Unusual isomorphism in crystals of organic solvates with hydrazine and water

Unusual isomorphism and isomorphous substitution in crystals of organic solvates with hydrazine and water are observed for the first time.

Cyclic dipeptide peroxosolvates: first direct evidence for hydrogen bonding between hydrogen peroxide and a peptide backbone

The crystal structures of cyclic dipeptide peroxosolvates provide valuable insight into the non-redox interaction of hydrogen peroxide with the peptide backbone.

Crystal structures of non-proteinogenic amino acid peroxosolvates: rare example of H-bonded hydrogen peroxide chains

Novel peroxosolvates of the non-proteinogenic amino acids sarcosine C₃H₇NO₂·H₂O₂ (1) and phenylserine C₉H₁₁NO₃·H₂O₂ (2) were prepared and their structures were determined by X-ray crystallography.

H2O2induced formation of graded composition sodium-doped tin dioxide and template-free synthesis of yolk–shell SnO2particles and their sensing application

This article introduces a SnO₂yolk–shell synthesis protocol based on hydrogen peroxide sol–gel processing.