Pairs Of Nitrogen Atoms Research Articles

CHEMICAL TRANSFORMATIONS OF PYRROLO-1,5-BENZODIAZEPINE DERIVATIVES

One of the most important tasks in modern organic chemistry is search and development of simple synthesis methods and study of the chemical properties of new biologically active substances. Pyrrolo-1,5-benzodiazepine derivatives refer to an important class of nitrogen-containing heterocycles with a wide range of biological activities. Based on the structure of the synthesized 4,5-dihydropyrrolo[1,2,3-e,f][1,5]-benzodiazepin-6(7H)-ones, it can be concluded that they possess high reactivity towards chemical transformations. This work examines the chemical properties of these derivatives (hydrolysis, transesterification, restoration, alkylation, amidation) and evaluates the acid-base properties of pyrrolo-1,5-benzodiazepine derivatives. As a result of the research we obtained two values for ionization constants that correspond to the protonation of the amide group of the diazepine ring and the indole part of the molecule. Protonation of the amide group of the diazepine ring can occur either on the nitrogen atom or the oxygen atom. However, O-protonation is more likely. In this case the mesomeric bonding of the electron pair of nitrogen atom with π/r-electron sextet of the benzene ring is not disrupted. These data provide valuable information on the reliance of the biological activity of the compound on its chemical structure and its chemical properties. The prospects for studying the biological activity of synthesized pyrrolo-1,5-benzodiazepine derivatives for their further use in medical practice is demonstrated.

Synergistic sulfur-doped tri-metal phosphide electrocatalyst for efficient hydrazine oxidation in water electrolysis: Toward high-performance hydrogen fuel generation

Replacing the slow anodic oxygen evolution reaction with the hydrazine (N2H4) oxidation reaction (HzOR) is a promising strategy for achieving energy-efficient hydrogen (H2) fuel production in water electrolyzer systems. Therefore, developing efficient electrocatalysts for the HzOR, in combination with the cathodic hydrogen evolution reaction, is essential for achieving high H2 fuel generation rates and advancing N2H4 fuel cell technology. In this study, we fabricated NiCoFe oxide derived from a metal-organic framework, followed by the physical mixing and carbonization of S and P. The strong intrinsic activity of S-doped tri-metal phosphide (TMP) against the HzOR is evidenced by its role in the chemisorption of N2H4 on its surface, where a dative link is formed between the electrons of the lone pair of nitrogen atoms in N2H4 and the empty orbitals of the metals in the TMP alloy. Using this process, we demonstrated the high performance of flow cell electrolysis for overall water and hydrazine oxidation by assembling the S-TMP||S-TMP electrode as both the anode and cathode of the electrolyzer. The resulting cell voltage was 0.35 V for HzOR and 1.53 V for overall water splitting, and the electric current density reached 10 mA·cm−2, with high stability over 20 h. The electrolyzer efficiency was significantly superior to that of electrolyzers constructed using other types of dual-purpose electrocatalysts as catalyst pairs. Furthermore, the overall effectiveness of the electrolyzer was comparable to that of electrolyzers incorporating two distinct, well-established, single-purpose electrocatalyst pairs for the water and hydrazine splitting reactions.

Structures and stability of I2 and ICl complexes with pyridine: Ab initio and DFT study.

Theoretical investigation of thermodynamic stability and bonding features of possible isomers of the molecular and ionic complexes of pyridine with molecular iodine and iodine monochloride IX (X = I,Cl) is presented. M06-2X DFT functional is found to provide bond distances and dissociation energies which are close to those obtained at high-level ab initio CCSD(T)/aug-cc-pvtz//CCSD/aug-cc-pvtz benchmark computations for the most stable isomers, formed via donation of a lone pair of nitrogen atom of pyridine to the iodine atom. These isomers are by 23-33 kJ mol-1 (in case of I2) and by 39-56 kJ mol-1 (in case of ICl) more stable than other molecular complexes. T-shaped π-σ* bonded isomers turn out to be energetically comparable with van der Waals bound compounds. Among the ionic isomers, structures featuring [IPy2]+ cation with I3 - or ICl2 - counterions are more stable. Oligomerization favors ionic isomers starting from the tetrameric clusters of the composition (IX)4Py4.

Interaction between dirhodium(II) tetraacetate and PAMAM dendrimer grafted onto magnetite nanoparticles: Effects on magnetic properties

In this study, we report on fabrication and characterization of a novel magnetic nanocarrier based on association of magnetite nanoparticles (NPs) with poly(amidoamine) (PAMAM) dendrimers loading dirhodium(II) tetraacetate complex (DiRh(II)). The pristine magnetite NP was coated with ATPS (3-aminopropyltriethoxysilane). The interaction between PAMAM dendrimer and DiRh(II) and its effects on magnetic properties were investigated. The magnetite spinel phase is confirmed via x-ray diffraction (XRD) and Raman spectroscopy data analysis. A mean crystallite size of 9.5 ± 0.3 nm of magnetite particles is assessed from XRD data, which is close to the values obtained via dynamic light scattering (DLS) and transmission electron microscopy micrographs. Our findings strongly suggest that the Rh(II) ions interact with lone electron pairs of nitrogen atoms in amide-II and primary amines of PAMAM surface-terminated moieties. The onset of an absorption peak at 283 nm in DiRh(II) containing sample, assigned to σRh-L→σ∗Rh-Rh electronic transition, revealed a direct interaction between Rh(II) ions and L moieties of PAMAM dendrimer. Magnetization results indicate that the presence of DiRh(II) attached to PAMAM dendrimer leads to the strong weakening of magnetic dipole–dipole interactions in ATPS- and ATPS + PAMAM coated magnetite nanoparticles.

Cu(II) complexes as catalyst precursors in the process of selective hydrogenation of diene hydrocarbons

The reaction of copper(II) acetate with 3-furancarboxylic acid (Hfur) and 5-nitro-2-furancarboxylic acid (Hnfur) with participation of 4-phenylpyridine (phpy) in acetonitrile resulted in mononuclear complexes [Cu(L)2(phpy)2(H2O)]·solv (L = fur (1), nfur (2); solv = phpy (1)) whose structures were determined by direct single crystal X-ray analysis. According to X-ray data, the complexing component in 1 and 2 is in a distorted square-pyramidal environment (CuN2O3); the pyramid base is formed by monodentate-bound oxygen atoms of fur-/nfur- anions and a pair of nitrogen atoms of the phpy moieties, while the water molecule occupies an axial position. It was found for the first time that copper nanoparticles immobilized on the surface of γ-Al2O3 obtained by chemical reduction of 1 and 2 (pre-deposited on the surface from solution) with sodium tetrahydroborate show high selectivity of monohydrogenation of tricyclo[5.2.1.02,6]deca-3,8-diene (dicyclopentadiene, DCPD) to give tricyclo[5.2.1.02,6]dec-4-ene (5,6-dihydrocyclopentadiene, DHDCPD). The catalytic activity tests show high selectivity (up to 100 %) of the catalysts studied in the reaction of partial hydrogenation to DHDCPD under continuous process conditions even at high conversion values (up to 96 %) and with hydrogen present in excess. Thermal behavior of 1 and 2 was studied by simultaneous thermal analysis (STA).

Photodegradation of crystal violet dye in water using octadecylamine-capped CdS nanoparticles synthesized from Cd(II) N,N′-diarylformamidine dithiocarbamates and their 2,2-bipyridine adducts

Cadmium(II) complexes of N,N′-diarylformamidine dithiocarbamate of the general formula [Cd-(L)2] (L = N,N'-bis(2,6-dimethylphenyl)formamidine dithiocarbamate L1 (1), N,N'-bis(2,6-disopropylphenyl)formamidine dithiocarbamate L2 (2), N'-(2,6-dichlorophenyl-N-(2,6-dimethylphenyl)formamidine dithiocarbamate L3 (3), N'-(2,6-dichlorophenyl)-N-(2,6-diisopropylphenyl)formamidine dithiocarbamate L4 (4) and their 2,2-bipyridine (bipy) adducts, [Cd-(L1)2bipy] (5), [Cd-(L2)2bipy] (6), [Cd-(L3)2bipy] (7), [Cd-(L4)2bipy] (8)) have been synthesized and characterized using various spectroscopic and analytical techniques. For one of the 2,2-bipyridine adducts, the molecular structure was determined using single crystal X-ray structure as a six-coordinate Cd(II) complex in which two pairs of sulfur atoms from two dithiocarbamate ligands and a pair of nitrogen atoms from bipy completed the distorted octahedral geometry. Complexes 1, 3 and 5 were used as single source precursors for formation of octadecylamine capped cadmium nanoparticles, CdS1, CdS3 and CdS5. HR-TEM images of as-synthesized CdS1, CdS3 and CdS5 particles are nano-spherical in shape with size distributions ranging between 4 and 9 nm. The as-synthesized CdS nanoparticles were used as photocatalysts for degradation of crystal violet, with degradation efficiency of 75-84% and rate constants of 0.0050, 0.0043 and 0.0039 min−1 for CdS1, CdS3 and CdS5, respectively.

Synthesis, Biological Activity of Trimethoprim derivative and the Complexes

This study demonstrates the synthesis of new ligands derived from trimethoprim with their Iron(III) and copper (ll) complexes. At the beginning, preparing new ligands, the first namly N, N’-(5-(3,4,5-trimethoxybenzyl)pyrimidine-2,4-diyl)bis(3,4,5-trihydroxy benza mide)and the Ligand second namly N, N’-(((5-(3,4,5-trimethoxybenzyl)pyrimidine-2,4-diyl) bis(azanediyl))bis(carbonthioyl) bis(3,4,5-trihydroxybenzamide) which prepared by nucleophilic addition of trimethoprim to Gallic chloride and prepared also by nucleophilic addition of trimethoprim to the Solution of Ammonium thiocyanate and Gallic chloride. Ferric Ion (III) and Copperic Ion (ll) complexes have been prepared with molar ratio [1:2]. The synthesis ligands have been characterized by Uv-Visible, FT-IR, 1HNMR, 13CNMR and EI-mass, while the complexes have been characterized by elemental analysis, Uv-Visible, FT-IR, Conductivity measurements and thermogravemtric (TgA) analysis. The ligands acts as multiple sites coordinating with ferric ion and copper ion, Via lone pair of nitrogen atom of NHC= and phenolic oxygen. In Vitro, the ligands and complexes have been tested for their growth Inhibitory activity against Gram negative bacteria Salmonella Spp and Gram Positive Staphylococcus Spp. The results of the test indicate that the synthesized compounds possessed a high inhibition effectiveness comparative with trimethoprim.

Correlations between spectroscopic data for charge-transfer complexes of two artificial sweeteners, aspartame and neotame, generated with several π-acceptors

Charge-transfer (CT) interaction of two artificial sweeteners, aspartame (Asp) and neotame (Neo), with three organic π-acceptors was investigated by UV–visible and Infrared (IR) spectrophotometric measurements. The target sweeteners interacted with the 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), chloranilic acid (CA), and picric acid (PA) molecules in methanol solvent at room temperature. Spectral results suggest that the unshared electron pair of nitrogen atoms (-NH2 in Asp molecule, and -NH in Neo molecule) donate electronic charge to the aromatic ring of the acceptor (Asp→acceptor; Neo → acceptor) forming the CT complex via a n → π* transition. The 1:1 Benesi-Hildebrand method was used to calculate several spectroscopic data, such as the formation constant (KCT) and the molar extinction coefficient (εmax), and other physical parameters. The correlation test indicates strong relationships among several of the physical parameters.

Effect of alkyl substituent on molecular configuration in a Cu(II) complex: Synthesis of Cu and CuO nanoparticles using a single, solid-source precursor

A new hydrazone-type ligand, methyl 4-(pyridine-4yl-methylene) hydrazinecarboxylate (C8H9N3O2; 4-pymc) and its Cu(II) complex [Cu(4-pymc)2(CH3COO)2(H2O)] (1) were prepared and characterized. The structure of 1 comprises monomers in which Cu is five-coordinated with a distorted square pyramidal structure. Oxygen atoms of two monodentate acetate anions and a pair of nitrogen atoms from pyridine rings form the basal plane. The apical position is filled by a water molecule. Further, the TEM images demonstrated successful preparation of both Cu (~35 nm) and CuO (~95 nm) nanoparticles (NPs) using the single source as-prepared Cu(II) complex via a thermal decomposition approach simply by changing the atmospheric conditions (i.e., vacuum and air atmospheres) under which the Cu(II) complex was calcined for 1 h at 400 °C. Furthermore, the TG-DTA studies indicate that 1 underwent endo- followed by exo-thermic decomposition to form CuO as the end residue in an air atmosphere. The production of Cu and CuO NPs was corroborated by powder x-ray diffraction (PXRD) analysis. The sharp and high intensity PXRD peaks of the calcined samples corroborated that the formed NPs had no impurity and high crystallinity. Furthermore, both ligand and Cu(II) complex showed photoluminescence properties. Also, we demonstrated that the prepared 1 can act as a single, solid-source precursor to form both Cu and CuO NPs.

Design of new pincer fullerene ligands thorough [2+3] cycloaddition of the azomethine ylides to fullerene cage: a DFT study

ABSTRACTWe have investigated [2+3] cycloaddition reactions occurred thorough the addition of 1,3-dipoles, azomethine ylide derivatives (RHC-NH+-CHR–), to [6, 6] ring fusion bonds of a fullerene C60 cage, in order to design new pincer fullerene ligands. The negative values of [2+3] cycloaddition reaction energies indicate the exothermic character of formation of the considered pincer fullerenes. Exploring of the effects of nature of the flanking arms on fullerene pincer ligands based on the frontier molecular orbital analysis (FMO) indicates that reaction energies well correlate with HOMO of 1,3 dipoles. The pincer-ligated metal complexes obtained by the addition of transition metals to the pincer bites. Natural bonding orbital analyses (NBO) are performed to investigate the delocalisation of the localised bonds and lone pairs of donor nitrogen atoms and the transition metals in the considered pincer-ligated metal complexes. Based on our results, the strongest interaction among all the interactions is due to the delocalisation of electrons from lone pairs of central nitrogen atoms to the LP* of the transition metal, following by the lone pairs of nitrogen atoms in the flanking arms.

Theoretical study on prismatic (N6)n (n=16–35) molecules

As a continuation of our study on the stability of pure nitrogen molecules, twenty members of the (N6)n (n = 16–35) molecular sequence with D3h or D3d symmetry alternatively are studied in this work. The structures and energies are examined at the B3LYP/cc‒pvDZ computational level. “Natural Bond Orbital (NBO)” and “Atom In Molecule (AIM)” analyses are performed to investigate the bonding properties and the electronic topologies of the prismatic molecules. The van der Waals forces or the dispersion interactions are identified to be the dominant stabilizing factor for large prismatic nitrogen cages. The van der Waals forces interweave with covalent bonds to form a dense network which tightly bind nitrogen atoms at grid points, and consequently, to make the prismatic (N6)n molecules stable. The mechanism of generating van der Waals forces in the prismatic molecules is the focus of this paper. Geometrically, all the polygons on the prismatic surface are boat hexagons except the two caps. The van der Waals forces or dispersion interactions occur only between the nitrogen atoms at positions 1′,4′ of the boat hexagon on the surface. The atom‒atom proximity effect of nitrogen atoms at the positions 1′,4′ leads to the van der Waals interaction. Topologically, van der Waals forces are generated by partial overlap of sp3 hybrid orbitals of lone pairs of nitrogen atoms at positions 1′,4’. These large prism‒shaped nitrogen cages may also be novel beeline nanotubes which is environmentally friendly. This work is expected to open up a bright prospect of the study and applications of nitrogen nanofibers.

Linewidth broadening and tunneling of excitons bound to N pairs in dilute GaAs:N

The exciton bound to a pair of nitrogen atoms situated at nearby lattice sites in dilute GaAs:N provides an energetically uniform electronic system, spectrally distinct from pairs with larger or smaller separations, and can even be grown with a uniform pair orientation in the crystal. We use photoluminescence excitation spectroscopy on an ensemble of N pairs to study the narrow continuous energy distribution within two of the individual exchange- and symmetry-split exciton states. Inhomogeneous linewidths of 50–60 μeV vary across the crystal on a mesoscopic scale and can be 30 μeV at microscopic locations indicating that the homogeneous linewidth inferred from previous time-domain measurements is still considerably broadened. While excitation and emission linewidths are similar, results show a small energy shift between them indicative of exciton transfer via phonon-assisted tunneling between spatially separated N pairs. We numerically simulate the tunneling in a spatial network of randomly distributed pairs having a normal distribution of bound exciton energies. Comparing the ensemble excitation-emission energy shift with the measured results shows that the transfer probability is higher than expected from the dilute pair concentration and what is known of the exciton wavefunction spatial extent. Both the broadening and the exciton transfer have implications for the goal of pair-bound excitons as a single- or multi-qubit system.

MODIFICATION OF EXPANDED PERLITE WITH ORTHOPHENANTHROLINE FOR FORMATION OF ACTIVE SITES FOR ACID DYES: PREPARATION AND CHARACTERIZATION

The expanded perlite (aluminosilicate naturally acid) has been modified with orthophenanthroline (Lewis base). The material was characterized by TG/DTA, XRD and IR. The thermogravimetric curve of the modified expanded perlite presented a lower thermal stability due to the orthophenanthroline and showed 13,6% of mass loss total. However, pure expanded perlite presented only 2,3% of the mass loss. The DTA curve showed endothermic event characteristic of the presence of orthophenanthroline. For XRD analysis is visualized, the presence of reflections in the diffractogram relating to the modified material of orthophenanthroline peaks of crystallinity since no modification perlite is an amorphous material. The band regarding absorption vibration of Si-O group appears at lower wavenumbers than in the unmodified material. So there was an interaction between the OH groups of silanols of perlite groups with unshared electron pairs of nitrogen atoms and C=C bonds (also rich in electrons) in the chemical structure of orthophenanthroline as a result of a hydrogen bond between these groups. thus perlite was modified through the interaction of its acid sites (Si-OH) with Lewis basic sites of orthophenanthroline.

DFT Study of the Interaction of Trialkylamines with $$\hbox {Ni}_{4}$$ Ni 4 -Clusters

This research studies binding of trialkylamine derivatives to the multiplicity optimized \(\hbox {Ni}_{4}\)-clusters using theoretical approaches. The goal is to understand the interaction behavior on the metal surface and provide some key points important to the corrosion problems. The results show that trialkylamine derivatives are able to establish N–Ni bond through either short or long diagonal of \(\hbox {Ni}_{4}\)-cluster. Of the studied triethylamine, tripropylamine, and tributylamine, the last derivative in series shows highest binding energy. TAAs/\(\hbox {Ni}_{4}\)-cluster complexes with \(M=5\) show special electronic charge transfer that stabilizes the complex. According to this analysis for natural charges, therefore, the nature of metal–ligand (e.g., N–Ni) interactions that underlay TAAs/\(\hbox {Ni}_{4}\)-cluster complexes can be elucidated. Possible correlation between interaction strength, polarizability, nitrogen’s atomic charge and the orbitals energy gaps is also investigated. The results of natural bond orbital analysis explore the strong charge transfer from lone pair of nitrogen atom to \(\sigma ^{*}\) and \(n^{*}\) orbitals of the clusters. The trialkylamines in this work are weaker corrosion inhibitor on the small nickel cluster than the previously studied aromatic nitrogen containing compounds like pyridine.

Effective enhancement on methanol adsorption in Cu-BTC by combination of lithium-doping and nitrogen-doping functionalization

Grand canonical Monte Carlo method (GCMC) simulation combined with density functional theory calculation was used to investigate the adsorption in Cu-BTC, with nitrogen- and lithium-doping functionalization in order to understand the underlying performance of MOFs in methanol adsorption. A new N-doping structure, 3N–CuBTC, was theoretically constructed by replacing the carbon atoms with hydrogen connection in the organic linkers by nitrogen atoms. 3N–CuBTC shows higher methanol capacity in the measured pressure range due to the increased dispersive interactions caused by the lone electron pair of nitrogen atoms. Another Li-doping structure, 3Li–3N–CuBTC, was fabricated by doping Li atoms on the base of 3N–CuBTC. 3Li–3N–CuBTC demonstrated higher methanol capacity due to the stronger interaction between the induced Li atoms and methanol molecules. Furthermore, these two results can be attributed to the new adsorption sites created by N- and Li-doping, as revealed by the more exothermic binding energies on N-sites (− 49.37 kJ mol−1) and Li-sites (− 122.28 kJ mol−1) than Cu-sites (− 40.62 kJ mol−1). According to the simulation results, it can be concluded that both functionalized Cu-BTCs are capable of enhancing the methanol adsorption capacity of the framework at pressure from 0 to 14 kPa at 298 K.

P 060 - New radical-regulatory properties of tryptophan and its derivatives

The effects provoked by ionizing radiation or metabolic disturbances in a living organism result in hyperproduction of reactive species, including O-, C- and N-centered organic and inorganic radicals. Further transformations of such radicals lead to activation of free-radical processes causing damage to biologically relevant molecules. Such processes account for and/or participate in the development of cardiovascular, neurodegenerative, oncological and inflammatory diseases. So, radical-regulatory activity of substances should be mainly associated with their high reactivity towards different types of organic radicals. The subject of this study was investigation of new type tryptophan and its derivatives interactions with O- and C-centered radicals being formed during radiation- and peroxide-induced transformations of organic compounds and with N-centered 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical. Tryptophan and its derivatives displayed the antioxidant properties due to the ability of these compounds to reduce O-centered organic radicals via the reaction of electron transfer from the lone pair of nitrogen atoms. We have found that substances under study can add and oxidize C-centered organic radicals. Serotonin and 5-hydroxytryptophan are characterized by moderate reactivity toward the N-centered DPPH radical as compared with that of classical antioxidants.

Manifestation of the gauche effect in conformers of benzenesulfonic acid hydrazide

Conformational properties of a benzenesulfonic acid hydrazide molecule and its para-nitro and para-methyl derivatives, which have found wide application as porofors and biologically active compounds, are studied. It is found that the benzenesulfonic acid hydrazide molecule has six conformers with relative energies of 0//0 kcal/mol, 0.34//0.98 kcal/mol, 2.51//2.25 kcal/mol, 2.54//2.56 kcal/mol, 2.90//3.28 kcal/mol, 6.64//6.43 kcal/mol (MP2//DFT(B3LYP) with the cc-pVTZ basis set), each conformer has enantiomer. The conformers differ from each other in the relative orientation of the fragments of the–SO2NHNH2 group, the energies of the frontier orbitals, the direction and value of the dipole moments. It is shown that the introduction of a nitro or methyl group into the para-position practically does not affect the conformational properties of the sulfonyl hydrazide group. Change in the structure of benzenesulfonic acid hydrazide during the crystal–gas transition is considered and it is revealed that in the crystal the conformation similar in structure to one of the high-energy conformers of the free molecule is stabilized. The NBO analysis of the electron density distribution is performed and it is shown that the occurrence of the gauche effect in all conformers of the molecules under study can be interpreted by the manifestation of the total action of strong anomeric effects between the lone pairs of nitrogen atoms and antibonding orbitals of S=O, N–H, C–S, and N–S bonds.

Electronic structure of nickel porphyrin NiP: Study by X-ray photoelectron and absorption spectroscopy

Energy distributions and properties of the occupied and empty electronic states for a planar complex of nickel porphyrin NiP are studied by X-ray photoemission and absorption spectroscopy techniques. As a result of the analysis of the experimental spectra of valence photoemission, the nature and energy positions of the highest occupied electronic states were determined: the highest occupied state is formed mostly by atomic states of the porphine ligand; the following two states are associated with 3d states of the nickel atom. It was found that the lowest empty state is specific and is described by the σ-type b1g MO formed by empty \(Ni3{d_{{x^2} - {y^2}}}\)-states and occupied 2p-states of lone electron pairs of nitrogen atoms. This specific nature of the lowest empty state is a consequence of the donor–acceptor chemical bond in NiP.

Theoretical study addressing the effects of tautomerism and explicit/implicit water molecules on NQR and NMR parameters of tetrazole-5-thione.

DFT/B3LYP calculations were employed to study the effects of tautomerism and explicit/implicit water molecules on Nuclear Quadrupole Resonance (NQR) and Nuclear Magnetic Resonance (NMR) tensors of nitrogen nuclei in tetrazole-5-thione structure. The obtained results revealed that nuclear quadrupole coupling constant (χ) and isotropic chemical shielding (σiso ) values of nitrogen nuclei in tetrazole ring of five possible tautomeric forms of tetrazole-5-thione, i.e. two thione forms called tautomers A and E and three thiol forms called tautomers B, C, and D, were functions of resonance energy(E2 ) values of nitrogen lone pairs. Furthermore, it was observed that by increasing participation of lone pairs of nitrogen atoms in the ring resonance interactions, the σiso values around them were increased, while their χ and qzz values were decreased. However, the results indicated that with exception of tautomer B, the order of qzz and χ values of nitrogen nuclei in tetrazole ring was exactly opposite of the order of resonance energy values for the same nitrogen nuclei in all tautomers and their mono-hydrated complexes. In addition, a significant decrease was noticed in χ and qzz values when a water molecule was put in different positions near the tetrazole ring in tautomers A-E. The mentioned result can be attributed to hydrogen bond formation between nitrogen nuclei and the oxygen of water. In mono-hydrated complexes, the σiso values around nitrogen atoms acting as hydrogen donors in hydrogen bond formation (N-H….OH2 ) were decreased, while its values were increased for nitrogen atoms acting as hydrogen acceptors in hydrogen bond formation(N….H-OH). Copyright © 2016 John Wiley & Sons, Ltd.

Adsorption of Acetonitrile on Platinum and its Effects on Oxygen Reduction Reaction in Acidic Aqueous Solutions—Combined Theoretical and Experimental Study

Combined theoretical and experimental study of acetonitrile (AcN) adsorption on platinum was performed and its effects on the kinetics of oxygen reduction reaction in HClO4 and H2SO4 solutions were examined. Using periodic density functional theory calculations, it was shown that AcN molecule can interact with Pt surface either through the unsaturated π electron system or via lone electron pair of nitrogen atom. In both cases, adsorption energy decreases upon increasing coverage, while the modification of electronic structure of Pt surface is localized to the adsorption site. By combining the results of the DFT calculations with the results of blank cyclic voltammetry and rotating disk electrode voltammetry in O2-saturated solutions, it was concluded that the effects of AcN on Pt surface chemistry and ORR kinetics are primarily steric in nature. Resulting measured ORR activities of polycrystalline platinum in the presence of AcN are due to the combination of (i) suppression of (bi)sulfate adsorption (in H2SO4 solution), (ii) suppression of surface oxidation (in both H2SO4 an HClO4 solution), and (iii) site blockage by adsorbed AcN (or products of its electrochemical transformations).