Insights into the Mechanism of the Reaction between Tetrachloro‐p‐Benzoquinone and Hydrogen Peroxide and their Implications in the Catalytic Role of Water Molecules in Producing the Hydroxyl Radial

Detailed mechanisms for the formation of hydroxyl or alkoxyl radicals in the reactions between tetrachloro‐p‐benzoquinone (TCBQ) and organic hydroperoxides are crucial for better understanding the potential carcinogenicity of polyhalogenated quinones. Herein, the mechanism of the reaction between TCBQ and H₂O₂ has been systematically investigated at the B3LYP/6‐311++G** level of theory in the presence of different numbers of water molecules. We report that the whole reaction can easily take place with the assistance of explicit water molecules. Namely, an initial intermediate is formed first. After that, a nucleophilic attack of H₂O₂ onto TCBQ occurs, which results in the formation of a second intermediate that contains an OOH group. Subsequently, this second intermediate decomposes homolytically through cleavage of the O? O bond to produce a hydroxyl radical. Energy analyses suggest that the nucleophilic attack is the rate‐determining step in the whole reaction. The participation of explicit water molecules promotes the reaction significantly, which can be used to explain the experimental phenomena. In addition, the effects of F, Br, and CH₃ substituents on this reaction have also been studied.     

Density Functional Theory Study on Hydrogen Bonding Interaction of Catechin-(H2O)n

Density functional theory B3LYP method with 6‐31G* basis set has been used to optimize the geometries of the catechin, water and catechin‐(H₂O)_n complexes. The vibrational frequencies have been studied at the same level to analyze these complexes. Six and eleven stable structures for the catechin‐H₂O and catechin‐(H₂O)₂ have been found, respectively. Theories of atoms in molecules (AIM) and natural bond orbital (NBO) have been utilized to investigate the hydrogen bonds involved in all the systems. The interaction energies of all the complexes corrected by basis set superposition error, are from ?13.27 to ?83.56 kJ/mol. All calculations also indicate that there are strong hydrogen‐bonding interactions in catechin‐water complexes. The strong hydrogen‐bonding contributes to the interaction energies dominantly. The O–H stretching motions in all the complexes are red‐shifted relative to that of the monomer.     

DFT study on the intermolecular interactions between Aun (n = 2–4) and thymine

Density functional B3LYP method with 6-31++G** basis set is applied to optimize the geometries of the luteolin, water and luteolin–(H₂O)_n complexes. The vibrational frequencies are also studied at the same level to analyze these complexes. We obtained four steady luteolin–H₂O, nine steady luteolin–(H₂O)₂ and ten steady luteolin–(H₂O)₃, respectively. Theories of atoms in molecules (AIM) and natural bond orbital (NBO) are used to investigate the hydrogen bonds involved in all the systems. The interaction energies of all the complexes corrected by basis set superposition error, are within −13.7 to −82.5 kJ/mol. The strong hydrogen bonding mainly contribute to the interaction energies, Natural bond orbital analysis is performed to reveal the origin of the interaction. All calculations also indicate that there are strong hydrogen bonding interactions in luteolin–(H₂O)_n complexes. The OH stretching modes of complexes are red-shifted relative to those of the monomer.     

Detection and mechanistic investigation of halogenated benzoquinone induced DNA damage by photoelectrochemical DNA sensor

Halogenated phenols are widely used as biocides and are considered to be possibly carcinogenic to humans. In this report, a previously developed photoelectrochemical DNA sensor was employed to investigate DNA damage induced by tetra-halogenated quinones, the in vivo metabolites of halogenated phenols. The sensor surface was composed of a double-stranded DNA film assembled on a SnO₂ semiconductor electrode. A DNA intercalator, Ru(bpy)₂(dppz)²⁺, was allowed to bind to the DNA film and produce photocurrent upon light irradiation. After the DNA film was exposed to 300 μM tetrafluoro-1,4-benzoquinone (TFBQ), the photocurrent dropped by 20%. In a mixture of 300 μM TFBQ and 2 mM H₂O₂, the signal dropped by 40%. The signal reduction indicates less binding of Ru(bpy)₂(dppz)²⁺ due to structural damage of ds-DNA in the film. Similar results were obtained with tetra-1,4-chlorobenzoquinone (TCBQ), although the signal was not reduced as much as TFBQ. Fluorescence measurement showed that TFBQ/H₂O₂ generated more hydroxyl radicals than TCBQ/H₂O₂. Gel electrophoresis proved that the two benzoquinones produced DNA strand breaks together with H₂O₂, but not by themselves. Using the photoelectrochemical sensor, it was also found that TCBQ covalently bound with DNA did not produce additional oxidative damage in the presence of H₂O₂. The combined photoelectrochemistry, gel electrophoresis, and fluorescence data revealed distinctive differences between TFBQ and TCBQ in terms of DNA adduct formation and hydroxyl radical generation.     

Thermodynamic parameters for the binding process of the OH<Superscript>−</Superscript> ion with the dissipative structures. Calorimetric and conductometric titrations

Conductometric and calorimetric titrations of Extremely Diluted Solutions (EDS) were performed by adding HCl or NaOH solutions. The aim of this study is to obtain further confirmation of the hypothesized presence, in the EDS, of molecular aggregates of water molecules. The measurements on the EDS evidenced some relevant differences compared to those on solutions with just water as solvent. The conductivity and the pH caused by adding the titrant, namely NaOH or HCl, were markedly different to those of the control solutions. We suppose that the preparation procedure of the EDS could produce non-equilibrium changes in the supramolecular structure of water. The experimental results were interpreted by considering the interactions that can take place between the OH⁻ or H₃O⁺ and the hypothesized molecular aggregates of water molecules i.e. dissipative structures. A comparison was made about the nature of the driving force that leads to the formation of the complexes between the two ions deriving from probes and the molecular aggregates of water molecules (dissipative structures). In this study, we have determined the thermodynamic parameters of association between molecular aggregates of water molecules (dissipative structures) in the EDS and OH⁻ or H₃O⁺ probe ions. The experimental results were interpreted by considering a favorable interaction between the H₃O⁺ and OH⁻ ions and the dissipative structures, due, probably, to steric hindrance and chemical affinity with the aggregates.     

Molecular dynamics simulation of the interaction between methyl benzotriazole and Cu2O crystal

In circulating water system , methyl benzotriazole (TTA) is one of the common corrosion inhibitors for copper. But the inhibition mechanisms have not been clearly understood so far. In different number of water molecules, the interaction between TTA and Cu₂O (copper surface) was investigated with molecular dynamics (MD) method. The results showed that the MD simulation result with water was more consistent with the experiment results. In different number of water molecules, the sequence of the interaction energies between TTA and Cu₂O (001) was ? E ₁ (150H₂O) > ? E ₁(200H₂O) > ? E ₁(100H₂O) > ? E ₁(50H₂O) > ? E ₁(0H₂O). The number of water molecules had an important influence on the interaction between corrosion inhibitors and Cu₂O crystal. From non‐bond energy and pair correlation functions, the interaction energies of the model system were mainly contributed by the non‐bond interaction. Strong adsorption could be raised by the Coulomb interaction between the negatively charged functional groups in TTA and the positive copper ions in the Cu₂O (001) face, and further interaction between aggressive media and copper could be restricted. So, copper corrosion could be avoided. Chemical bonds and non‐bond interactions were formed between TTA and Cu₂O (001) in different number of water molecules. Water molecules could not be ignored during the MD simulation, too. The results obtained here may provide theoretical supports for developing new corrosion inhibitors.     

Molecular interaction of H2 and H2O with borthiin: a theoretical study

A density functional theory at the B3LYP/6-311G(d,p) level was applied to investigate the impact of hydrogen and water molecules on borthiin. The calculated binding energies of complexes were corrected for the basis set superposition error. The changes in structural parameters and in chemical hardness values were calculated for borthiin interacting with H₂ and H₂O. The strength of the weak interaction between borthiin and the H₂ and H₂O molecules was analyzed using the topological properties according to the ??Atoms in Molecules?? theory by Bader. The factors influencing the strength of the interaction between the borthiin and the H₂ and H₂O molecules were considered in detail using the NBO analysis. The vibrational frequencies and the intensities of the B-H stretching bands were calculated. The nucleus independent chemical shift (NICS) method was used to study the aromaticity of borthiin and the complexes.     

Theoretical studies of O2−:(H2O)n clusters

The interaction of superoxide ion O₂^? with up to four water molecules [O₂^?: (H₂O)_n, n = 1, 2, 4] has been investigated using ab initio molecular orbital theory. The binding energy of O₂^?: H₂O is calculated to be ?20.6 kcal/mol in good agreement with gas phase experimental data. At the MP3/6-31G^* level the O₂^?:H₂O complex has a C_2v structure with a double (cyclic) hydrogen bond between O₂^? and H₂O. A C_s structure with a single hydrogen bond is only 0.7 kcal/mol less stable. Interaction of H₂O with the doubly occupied π^* orbital of O₂^? is preferred slightly over interaction with the singly occupied π^* orbital. Natural bond orbital analysis suggests that both electrostatic and charge transfer interactions are important in anionic complexes. The charge transfer occurs predominantly in the O₂^? → H₂O direction and is important in determining the relative stabilities of the different structures and states. Singly and doubly hydrogen-bonded structures for the O₂^?: (H₂O)₂ and O₂^?: (H₂O)₄ clusters were found to be similar in stability and the increase in binding of the cluster becomes smaller as each additional water molecule is added to the cluster.     

Theoretical Study on the Hydrogen Bonding Interactions in Complexes of 5‐Hydroxytryptamine with Water

The energies, geometries and harmonic vibrational frequencies of 1:1 5‐hydroxytryptamine‐water (5‐HT‐H₂O) complexes are studied at the MP2/6‐311++G(d,p) level. Natural bond orbital (NBO), quantum theory of atoms in molecules (QTAIM) analyses and the localized molecular orbital energy decomposition analysis (LMO‐EDA) were performed to explore the nature of the hydrogen‐bonding interactions in these complexes. Various types of hydrogen bonds (H‐bonds) are formed in these 5‐HT‐H₂O complexes. The intermolecular C4H5^5‐HT···O^w H‐bond in HTW3 is strengthened due to the cooperativity, whereas no such cooperativity is found in the other 5‐HT‐H₂O complexes. H‐bond in which nitrogen atom of amino in 5‐HT acted as proton donors was stronger than other H‐bonds. Our researches show that the hydrogen bonding interaction plays a vital role on the relative stabilities of 5‐HT‐H₂O complexes.     

Homonuclear chalcogen–chalcogen bond interactions in complexes pairing YO3 and YHX molecules (Y = S,Se; X = H,Cl, Br,CCH, NC,OH, OCH3): Influence of substitution and cooperativity

MP2/aug‐cc‐pVTZ calculations are performed on complexes of YO₃ (Y = S, Se) with a series of electron‐donating chalcogen bases YHX (X = H, Cl, Br, CCH, NC, OH, OCH₃). These complexes are formed through the interaction of a positive electrostatic potential region (π‐hole) on the YO₃ molecule with the negative region in YHX. Interaction energies of the binary O₃Y???YHX complexes are in the range of ?4.37 to ?12.09 kcal/mol. The quantum theory of atoms in molecules and the natural bond orbital analysis were applied to characterize the nature of interactions. It was found that the formation and stability of these binary complexes are ruled mainly by electrostatic effects, although the electron charge transfer from YHX to YO₃ unit also seems to play an important role. In addition, mutual influence between the Y???N and Y???Y interactions is studied in the ternary HCN???O₃Y???YHX complexes. The results indicate that the formation of a Y???N interaction tends to weaken Y???Y bond in the ternary systems. Although the Y???Y interaction is weaker than the Y???N one, however, both types of interactions seem to compete with each other in the HCN???O₃Y???YHX complexes. © 2016 Wiley Periodicals, Inc.     

Theoretical study of the effects of substitution,solvation, and structure on the interaction between nitriles and methanol

We report an investigation on intermolecular interactions in R? CN ··· H? OCH₃ (R = H, CH₃, F, Cl, NO₂, OH, SH, SCH₃, CHO, COCH₃, CH₂Cl, CH₂F, CH₂OH, CH₂COOH, CF₃, SCOCH₃, SCF₃, OCHF₂, CH₂CF₃, CH₂OCH₃, and CH₂CH₂OH) complexes using density functional theory. The calculations were conducted on B3LYP/6‐311++G** level of theory for optimization of geometries of complexes and monomers. An improper hydrogen bonding (HB) in the H₃CO? H ··· NC? R complexes was observed in that N atom of the nitriles functions acts as a proton acceptor. Furthermore, quantum theory of “Atoms in Molecules” (AIM) and natural bond orbital (NBO) method were applied to analyze H‐bond interactions in respective complexes. The electron density (ρ) and Laplacian (?²ρ) properties, estimated by atoms in molecules calculations, indicate that H ··· N bond possesses low ρ and positive ?²ρ values, which are in agreement with partially covalent character of the HBs, whereas O? H bonds have negative ?²ρ values. In addition, the weak intermolecular force due to dipole–dipole interaction (U) is also considered for analysis. The examination of HB in these complexes by quantum theory of NBO method fairly supports the ab initio results. Natural population analysis data, the electron density, and Laplacian properties, as well as, the ν(O? H) and γ(O? H) frequencies of complexes, calculated at the B3LYP/6‐311++G** level of theory, are used to evaluate the HB interactions. The calculated geometrical parameters and conformational analysis in water phase solution show that the H₃CO? H ··· NC? R complexes in water are more stable than that in gas phase. The obtained results demonstrated a strong influence of the R substituent on the properties of complexes. Numerous correlations between topological, geometrical, thermodynamic properties, and energetic parameters were also found. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Binuclear Uranium(VI) Complexes with a “Pacman” Expanded Porphyrin: Computational Evidence for Highly Unusual Bis‐Actinyl Structures

On the basis of uranyl complexes reacting with a polypyrrolic ligand (H₄L), we explored structures and reaction energies of a series of new binuclear uranium(VI) complexes using relativistic density functional theory. Full geometry optimizations on [(UO₂)₂(L)], in which two uranyl groups were initially placed into the pacman ligand cavity, led to two minimum‐energy structures. These complexes with cation–cation interactions (CCI) exhibit unusual coordination modes of uranyls: one is a T‐shaped ( T ) skeleton formed by two linear uranyls {O_exo?U₂?O_endo→U₁(?O_exo)₂}, and another is a butterfly‐like ( B ) unit with one linear uranyl coordinating side‐by‐side to a second cis‐uranyl. The CCI in T was confirmed by the calculated longest distance and lowest stretching vibrational frequency of U₂?O_endo among the four U?O bonds. Isomer B is more stable than T , for which experimental tetrameric analogues are known. The formation of B and T complexes from the mononuclear [(UO₂)(H₂L)(thf)] ( M ) was found to be endothermic. The further protonation and dehydration of B and T are thermodynamically favorable. As a possible product, we have found a trianglelike binuclear uranium(VI) complex having a O?U?O?U?O unit.     

Halogen bonding in mono- and dihydrated halobenzene

Density functional theory calculations were performed on halogen-bonded and hydrogen-bonded systems consisting of a halobenzene (XPh; X = F, Cl, Br, I, and At) and one or two water molecules, using the M06-2X density functional with the 6-31+G(d) (for C, H, F, Cl, and Br) and aug-cc-pVDZ-PP (for I, At) basis sets. The counterpoise procedure was performed to counteract the effect of basis set superposition error. The results show halogen bonds form in the XPh-H₂O system when X > Cl. There is a trend toward stronger halogen bonding as the halogen group is descended, as assessed by interaction energy and X•••O_w internuclear separation (where O_w is the water oxygen). For all XPh-H₂O systems hydrogen-bonded systems exist, containing a combination of CH•••O_w and O_wH_w•••X hydrogen bonds. For all systems except X = At the X•••H_w hydrogen-bonding interaction is stronger than the X•••O_w halogen bond. In the XPh-(H₂O)₂ system halogen bonds form only for X > Br. The two water molecules prefer to form a water dimer, either located around the C H bond (for X = Br, At, and I) or located above the benzene ring (for all halogens). Thus, even in the absence of competing strong interactions, halogen bonds may not form for the lighter halogens due to (1) competition from cooperative weak interactions such as C H•••O and OH•••X hydrogen bonds, or (2) if the formation of the halogen bond would preclude the formation of a water dimer. © 2018 Wiley Periodicals, Inc.     

Ligand Exchange in Pd(II)-NaCl-H<Subscript>2</Subscript>O and Pd(II)-HCl-H<Subscript>2</Subscript>O Systems: Quantum-Chemical Consideration

The behavior of potassium tetrachloropalladate(II) in media simulating biological liquids is studied. The rate of aquation in aqueous NaCl solutions is shown to be higher than the rate at which the Cl^? ligand enters the inner coordination sphere of the Pd atom. In HCl solutions, the formation of the Pd chloro complexes predominates due to protonation of water molecules in the composition of aqua complexes. The reactions of replacement of the ligands (H₂O molecules and H₃O⁺ ion) in the planar Pd(II) complexes by the chloride ion are studied by the ZINDO/1 method. All the complexes containing H₂O and H₃O⁺ ligands, except for [Pd(H₂O)₄]²⁺, contain intramolecular hydrogen bonds. The ZINDO/1 and RHF/STO-6G(d) calculations revealed “nonclassic” symmetrical O? H?O hydrogen bond in the [[Pd(H₂O)₃(H₃O)]³⁺ and trans-[Pd(H₂O)₂(H₃O)Cl]²⁺ complexes. The replacement of the H₃O⁺ ion by the Cl^? ion at the first three steps is thermodynamically more advantageous than the displacement of water molecules from the metal coordination sphere. The logarithms of stepwise stability constants of Pd(II) chloro complexes are found to correlate linearly with the enthalpies (ZINDO/1, PM3) of reactions of H₂O replacement by Cl^?.     

Five-coordinate dicarboxylate complexes of copper (+2) and zinc (+2)

A new dicarboxylic acid, LH₂ , derived from 2-[(2-hydroxy-3,5-dimethylphenyl) (phenyl)methyl]-4,6-dimethylphenol (1) was prepared by reacting it with methyl bromoacetate followed by alkaline hydrolysis. Two five-coordinate mononuclear complexes of L with zinc (+2) and copper (+2), [Zn(L)(py)₂(H₂O)]?·?H₂O?·?py (IV), and [Cu(L)(py)₂(H₂O)] (V), were prepared (py?=?pyridine) and characterized. The packing patterns of these two complexes are different and the H-bond interactions in their lattices are controlled by the presence or absence of water molecules. This difference arises from subtle change in the orientation of carbonyl groups of the carboxylates.     

Comparative analysis of blue‐shifted hydrogen bond versus conventional hydrogen bond in methyl radical complexes

Methyl radical complexes H₃C…HCN and H₃C…HNC have been investigated at the UMP2(full)/aug‐cc‐pVTZ level to elucidate the nature of hydrogen bonds. To better understand the intermolecular H‐bond interactions, topological analysis of electron density at bond critical points (BCP) is executed using Bader's atoms‐in‐molecules (AIM) theory. Natural bond orbital (NBO) analysis has also been performed to study the orbital interactions and change of hybridization. Theoretical calculations show that there is no essential difference between the blue‐shift H‐bond and the conventional one. In H₃C…HNC complex, rehybridization is responsible for shortening of the N? H bond. The hyperconjugative interaction between the single electron of the methyl radical and N? H antibonding orbital is up to 7.0 kcal/mol, exceeding 3.0 kcal/mol, the upper limit of hyperconjugative n(Y)→σ*(X–H) interaction to form the blue‐shifted H‐bond according to Alabugin's theory. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Dual Role of the 1,2,3‐Triazolium Ring as a Hydrogen‐Bond Donor and Anion–π Receptor in Anion‐Recognition Processes

Several bis(triazolium)‐based receptors have been synthesized as chemosensors for anion recognition. The central naphthalene core features two aryltriazolium side‐arms. NMR experiments revealed differences between the binding modes of the two triazolium rings: one triazolium ring acts as a hydrogen‐bond donor, the other as an anion–π receptor. Receptors 9²⁺?2BF₄ ^? (C₆H₅), 11²⁺?2BF₄ ^? (4‐NO₂?C₆H₄), and 13²⁺?2BF^4? (ferrocenyl) bind HP₂O₇^3? anions in a mixed‐binding mode that features a combination of hydrogen‐bonding and anion–π interactions and results in strong binding. On the other hand, receptor 10²⁺?2 BF₄ ^? (4‐CH₃O?C₆H₄) only displays combined Csp₂?H/anion–π interactions between the two arms of the receptors and the bound anion rather than triazolium (CH)⁺???anion hydrogen bonding. All receptors undergo a downfield shift of the triazolium protons, as well as the inner naphthalene protons, in the presence of H₂PO₄^? anions. That suggests that only hydrogen‐bonding interactions exist between the binding site and the bound anion, and involve a combination of cationic (triazolium) and neutral (naphthalene) C?H donor interactions. Theoretical calculations relate the electronic structure of the substituent on the aromatic group with the interaction energies and provide a minimum‐energy conformation for all the complexes that explains their measured properties.     

Light Emission in Water‐Containing Cocrystals: the Influence of Water Molecules on the Fluorescence Properties of a Schiff‐Base Molecule

In the presence or absence of water, a Schiff‐base compound, 4‐amino‐3‐(2‐(2‐hydroxybenzylidene)hydrazinyl)‐1H‐1,2,4‐triazole‐5(4H)‐thione ( HATT ), forms different crystalline states ( HATT , HATT ? 2 H₂O, and a lamellar structure, m‐HATT ? n H₂O), which show different luminescence emission properties. Herein, we investigate the emission of HATT and the role of water molecules. A water molecule, which acts as both a hydrogen‐bond acceptor and ‐donor, enlarges the distance between adjacent HATT molecules and hinders non‐radiative decay pathways.     

Nonperipherally Octa(butyloxy)‐Substituted Phthalocyanine Derivatives with Good Crystallinity: Effects of Metal–Ligand Coordination on the Molecular Structure,Internal Structure,and Dimensions of Self‐Assembled Nanostructures

To investigate the effects of metal–ligand coordination on the molecular structure, internal structure, dimensions, and morphology of self‐assembled nanostructures, two nonperipherally octa(alkoxyl)‐substituted phthalocyanine compounds with good crystallinity, namely, metal‐free 1,4,8,11,15,18,22,25‐octa(butyloxy)phthalocyanine H₂Pc(α‐OC₄H₉)₈ ( 1 ) and its lead complex Pb[Pc(α‐OC₄H₉)₈] ( 2 ), were synthesized. Single‐crystal X‐ray diffraction analysis revealed the distorted molecular structure of metal‐free phthalocyanine with a saddle conformation. In the crystal of 2 , two monomeric molecules are linked by coordination of the Pb atom of one molecule with an aza‐nitrogen atom and its two neighboring oxygen atoms from the butyloxy substituents of another molecule, thereby forming a Pb‐connected pseudo‐double‐decker supramolecular structure with a domed conformation for the phthalocyanine ligand. The self‐assembling properties of 1 and 2 in the absence and presence of sodium ions were comparatively investigated by scanning electronic microscopy (SEM), spectroscopy, and X‐ray diffraction techniques. Intermolecular π–π interactions between metal‐free phthalocyanine molecules led to the formation of nanoribbons several micrometers in length and with an average width of approximately 100 nm, whereas the phthalocyaninato lead complex self‐assembles into nanostructures also with the ribbon morphology and micrometer length but with a different average width of approximately 150 nm depending on the π–π interactions between neighboring Pb‐connected pseudo‐double‐decker building blocks. This revealed the effect of the molecular structure (conformation) associated with metal–ligand (Pb? N_isoindole, Pb? N_aza, and Pb? O_butyloxy) coordination on the dimensions of the nanostructures. In the presence of Na⁺, additional metal–ligand (Na? N_aza and Na? O_butyloxy) coordination bonds formed between sodium atoms and aza‐nitrogen atoms and the neighboring butyloxy oxygen atoms of two metal‐free phthalocyanine molecules cooperate with the intrinsic intermolecular π–π interactions, thereby resulting in an Na‐connected pseudo‐double‐decker building block with a twisted structure for the phthalocyanine ligand, which self‐assembles into twisted nanoribbons with an average width of approximately 50 nm depending on the intertetrapyrrole π–π interaction. This is evidenced by the X‐ray diffraction analysis results for the resulting aggregates. Twisted nanoribbons with an average width of approximately 100 nm were also formed from the lead coordination compound 2 in the presence of Na⁺ with a Pb‐connected pseudo‐double‐decker as the building block due to the formation of metal–ligand (Na? N_aza and Na? O_butyloxy) coordination bonds between additionally introduced sodium ions and two phthalocyanine ligands of neighboring pseudo‐double‐decker building blocks.     

A Theoretical Study of the Interaction of Hydrogen and Oxygen with Palladium or Gold Adsorbed on Pyridine‐Like Nitrogen‐Doped Graphene

The interaction of H₂ and O₂ molecules in the presence of nitrogen‐doped graphene decorated with either a palladium or gold atom was investigated by using density functional theory. It was found that two hydrogen molecules were adsorbed on the palladium atom. The interaction of these adsorbed hydrogen molecules with two oxygen molecules generates two hydrogen peroxide molecules first through a Eley–Rideal mechanism and then through a Langmuir–Hinshelwood mechanism. The barrier energies for this reaction were small; therefore, we expect that this process may occur spontaneously at room temperature. In the case of gold, a single hydrogen molecule is adsorbed and dissociated on the metal atom. The interaction of the dissociated hydrogen molecule on the surface with one oxygen molecule generates a water molecule. The competitive adsorption between oxygen and hydrogen molecules slightly favors oxygen adsorption.