Coordination Of Nitrogen Atom Research Articles

2,6-Bis(5-(tert-butyl)-1H-pyrazol-3-yl)pyridine: Effects of the Peripheral Aliphatic Side Chain on the Coordination of Actinides(III) and Lanthanides(III).

To improve our understanding of the interaction mechanism in trivalent lanthanide and actinide complexes, studies with structurally different hard and soft donor ligands are of great interest. For that reason, the coordination chemistry of An(III) and Ln(III) with 2,6-bis(5-(tert-butyl)-1H-pyrazol-3-yl)pyridine (C4-BPP) has been explored. Time-resolved laser fluorescence spectroscopy (TRLFS) studies have revealed the formation of [Cm(C4-BPP)n]3+ (n = 1-3) (log β1' = 7.2 ± 0.4, log β2' = 10.1 ± 0.5, and log β3' = 11.8 ± 0.6) and [Eu(C4-BPP)m]3+ (m = 1-2) (log β1' = 4.9 ± 0.2 and log β2' = 8.0 ± 0.4). The absence of the [Eu(C4-BPP)3]3+ complex shows a more favorable complexation of Cm(III) over that of Eu(III). Additionally, complementary NMR measurements have been conducted to examine the M(III)-N bond in Ln(III) and Am(III) C4-BPP complexes. 15N NMR data have revealed notable differences in the chemical shifts of the coordinating nitrogen atoms between the Am(III) and Ln(III) complexes. In the Am(III) complex, the coordinating nitrogen atoms have shown a shift by 260 ppm, indicating a higher fraction of covalent bonding in the Am(III)-N bond compared with the Ln(III)-N bond. This observation aligns excellently with the differences in the stability constants obtained from TRLFS studies.

Synthesis, Characterisation, Hirshfeld Surface Analysis, Magnetic Susceptibility, DFT Calculations, pkCSM Profile, and Biological Activities of Novel Mono‐, Di‐, and Multinuclear Cobalt (II) Complexes

AbstractThis study explores the synthesis and diverse properties of newly synthesised water‐soluble cobalt (II) complexes (1–3). Analysis of the complexes through various methods, including Hirshfeld surface analysis, reveals distinctive intermolecular interactions, particularly robust H‐bonding contributions to crystal packing. 2D fingerprint plots provide quantitative insights into supramolecular interactions, while TGA‐DSC analysis elucidates multi‐step decomposition processes, mainly involving organic moieties. FT‐IR and SCXRD confirm the structures of the complexes. Magnetic susceptibility measurements show paramagnetic behaviour in all complexes. FMO calculations expose HOMO‐LUMO gaps and charge transfer processes, with NBO analysis emphasizing the significance of chloride, nitrogen, and oxygen atoms in coordination. In addition, pkCSM profile was carried out. The biological properties of the complexes reveal potent antibacterial activity for 2 and 3 against Gram‐positive and Gram‐negative bacteria. Despite lower antibacterial efficacy compared to standard antibiotics, their water solubility suggests potential human pharmacological applications. In terms of anti‐inflammatory activity, all three complexes exhibit concentration‐dependent prevention of ovalbumin denaturation, with 2 being the most effective. Compound 3, despite having seven carboxyl groups, exhibits the weakest anti‐inflammatory effect, potentially attributed to complex formation obscuring these groups. Furthermore, all complexes display antioxidant activities; 1 and 2 are greater than BHT in the ferric thiocyanate assay.

Tuning Redox Behavior of Sulfur Cathodes Via Ternary-Coordinated Single Fe Atom in Lithium-Sulfur Batteries.

Modulating the coordination configuration of single Fe atom has been an efficient strategy to strengthen the redox dynamics for lithium-sulfur batteries (LSBs) but remains challenging. Herein, the single Fe atom is functioned with nitrogen and carbon atoms in the first shell, and simultaneously, oxidized sulfur (─SOx) in the second shell, which presents a lower antibonding state and well address the redox activity of sulfur cathodes. In the ternary-coordinated single Fe atom catalyst (FeN2C2-SOx-NC), the binary structure of FeN2C2 provides a lower Fe-S bonding strength and d-p orbital hybridization, which obviously optimizes the adsorption and desorption behavior of sulfur species during the reduction and oxidation reaction processes. Simultaneously, the ─SOx redistributes the electron density of the coordinating nitrogen atoms, which possesses high electron-withdrawing ability and develops electrocatalytic activity. As a result, the sulfur cathodes with FeN2C2-SOx-NC present an excellent high-rate cyclic performance, accompanied by a capacity decay rate of 0.08% per cycle for 500 cycles at 4.0 C. This study provides new insights for optimizing the redox dynamics of sulfur cathodes in LSBs at the atomic level.

Impact of the hybridization form of the coordinated nitrogen atom on the electrocatalytic water oxidation performance of copper complexes with pentadentate amine-pyridine ligands.

The field of molecular catalysts places a strong emphasis on the connection between the ligand structure and its catalytic performance. Herein, we changed the type of coordinated nitrogen atom in pentadentate amine-pyridine ligands to explore the impact of its hybridization form on the water oxidation performance of copper complexes. In the electrochemical tests, the copper complex bearing dipyridine-triamine displayed an apparently higher rate constant of 4.97 s-1, while the copper complex with tripyridine-diamine demonstrated overpotential reduction by 56 mV and better long-term electrolytic stability.

Synthesis, structure and optoelectronic properties of iridium(III) complexes bearing a four-membered Ir-N-C[sbnd]N chelate structure

Herein four novel iridium(III) complexes (tfpmd)2Ir(dpppy) (Ir1a, tfpmd = 2-(4-(trifluoromethyl) phenyl) pyrimidine, dpppy = P,P-diphenyl-N-(pyridin-2-yl)phosphinic amide), (tfpmd)2Ir(dppq) (Ir1b, dppq = P,P-diphenyl-N-(quinolin-2-yl)phosphinic amide), (tfpqz)2Ir(dpppy) (Ir2a, tfpzq = 4-(4-(trifluoromethyl) phenyl) quinazoline) and (tfpqz)2Ir(dppq) (Ir2b) were synthetized, and their structures, opto-physical, and electro-chemical properties were investigated in detail. The crystal structure shows that these complexes exhibit pseudo-octahedral geometry around iridium atom coordinated by C, N atoms from cyclometalated and ancillary ligands. Interestingly, two coordinated nitrogen atoms from the ancillary ligand form an unusual quaternary ring with the central iridium ion. Ir1a and Ir1b emit pure-green light with Commission Internationale de L'Eclairage (CIE) color coordinates of (0.25, 0.67) and (0.22, 0.67), respectively, in CH2Cl2 solution. With the increase of the degree of conjugation of the cyclometalated ligand from tfpmd to tfpqz, the luminescence of complexes Ir2a and Ir2b is greatly red-shifted, and pure-red emission with CIE coordinates of (0.66, 0.34) and (0.66, 0.34), respectively, is obtained. The photophysical behaviors were reasonably explained by quantum chemical calculations. The calculation results shows that their emission is ascribed to the mixed 3MLCT (metal-ligand charge transfer, dπ(Ir)→π*(cyclometalated ligand)) and 3LLCT (ligand-ligand charge transfer, π(ancillary ligand)→π*(cyclometalated ligand)) states. Owing to their good thermal and electrochemical stabilities, organic light emitting diode (OLED) devices with dual-emitting layer structure and a space interlayer were fabricated and exhibited high electroluminescent properties and mild efficiency roll-off (14%-21%).

Steric effect on the photoreaction of chromium(III) porphyrin complexes with imidazole ligands

The steric effect in the photoreaction and ligand substitution reaction of axially coordinated imidazole ligands in chromium(III) porphyrin complexes was investigated in toluene. Imidazole ligands that have various alkyl substituents at the carbon atom [Formula: see text] to the coordinating nitrogen atom were used. The quantum yield of the photodissociation reaction of the axial imidazole ligand shows a remarkable steric effect. Reflecting the steric bulkiness, the magnitude of the quantum yield is isopropyl > ethyl > methyl > (H). The steric effect also appears in the thermal ligand substitution reactions. The mechanism of the steric effect on reactivity will be discussed in terms of the steric hindrance between the porphyrin ligand and the alkyl substituents of imidazole.

Zinc(II) Complex Containing Oxazole Ring: Synthesis, Crystal Structure, Characterization, DFT Calculations, and Hirshfeld Surface Analysis.

A new complex of Zn(II), with 5-chloro-2-methylbenzoxazole ligand (L), has been synthesized by the reaction of zinc dichloride with the ligand (L= C8H6ClNO) in ethanol solution: dichloridobis(5-chloro-2-methyl-1,3-benzoxazole)-zinc(II), C16H12Cl4N2O2Zn. The synthesized complex has been fully characterized by elemental analysis, molar conductivity, FT‑IR, UV‑Vis, and single-crystal X-ray diffraction (XRD). The XRD analysis reveals that the complex has a 1:2 metal-to-ligand ratio. The zinc(II) complex has a distorted tetrahedral geometry with two coordinated nitrogen atoms from the ligand. Density Functional Theory (DFT) calculations were performed at the B3LYP level of theory using the LANL2DZ basis set for metal complex and the6-31G(d)basis set for non-metal elements to determine the optimum geometry structure of the complex, and the calculatedHOMOandLUMOorbital energies were presented. A natural bond orbital (NBO) analysis was carried out on the molecules to analyze the atomic charge distribution before and after the complexation of the ligand. The Hirshfeld surface mapped over dnorm, shape index, and curvature exhibited strongH...Cl/Cl...H and H...H intermolecular interactions as the principal contributors to crystalpacking.

Review: Elaboration, structure, and mechanical properties of oxynitride glasses

AbstractOxynitride glasses are glasses where threefold coordinated nitrogen atoms substitute for twofold oxygen ones, hence resulting in a larger interatomic cross‐linking degree. Such glasses were first observed at the grain boundary in silicon nitride ceramics, where they govern the high‐temperature behavior. Later, they were prepared as bulk materials and motivated numerous researches, thanks to their large viscosity, glass transition range, elastic moduli, hardness, and fracture toughness among inorganic and non‐metallic glasses. In different chemical systems that were investigated, the synthesis routes and the sources for these exceptional mechanical properties are reviewed. Oxynitride glasses are not easy to process and suffer from the loss of transparency as nitrogen is incorporated over some critical content. Nevertheless, they are attractive “specialty” glasses in various niche areas, thanks to their large refractive index and dielectric constant, improved chemical durability, high softening point, etc., and majorly to their exceptional mechanical properties.

Insights into the Complexation Mechanism of a Promising Lipophilic PyTri Ligand for Actinide Partitioning from Spent Nuclear Fuel.

The challenging issue of spent nuclear fuel (SNF) management is being tackled by developing advanced technologies that point to reduce environmental footprint, long-term radiotoxicity, volumes and residual heat of the final waste, and to increase the proliferation resistance. The advanced recycling strategy provides several promising processes for a safer reprocessing of SNF. Advanced hydrometallurgical processes can extract minor actinides directly from Plutonium and Uranium Reduction Extraction raffinate by using selective hydrophilic and lipophilic ligands. This research is focused on a recently developed N-heterocyclic selective lipophilic ligand for actinides separation to be exploited in advanced Selective ActiNide EXtraction (SANEX)-like processes: 2,6-bis(1-(2-ethylhexyl)-1H-1,2,3-triazol-4-yl)pyridine (PyTri-Ethyl-Hexyl-PTEH). The formation and stability of metal-ligand complexes have been investigated by different techniques. Preliminary studies carried out by electrospray ionization mass spectrometry (ESI-MS) analysis enabled to qualitatively explore the PTEH complexes with La(III) and Eu(III) ions as representatives of lanthanides. Time-resolved laser fluorescence spectroscopy (TRLFS) experiments have been carried out to determine the ligand stability constants with Cm(III) and Eu(III) and to better investigate the ligand complexes involved in the extraction process. The contribution of a 1:3 M/L complex, barely identified by ESI-MS analyses, was confirmed as the dominant species by TRLFS experiments. To shed light on ligand selectivity toward actinides over lanthanides, NMR investigations have been performed on PTEH complexes with Lu(III) and Am(III) ions, thereby showing significant differences in chemical shifts of the coordinating nitrogen atoms providing proof of a different bond nature between actinides and lanthanides. These scientific achievements encourage consideration of this PyTri ligand for a potential large-scale implementation.

Nitrogen Balance on Ni-N-C Promotor for High-Energy Lithium-Sulfur Pouch Cells.

The viability of lithium-sulfur (Li-S)batteries toward real implementation directly correlates with unlocking lithium polysulfide (LiPS) evolution reactions. Along this line, designing promotors with the function of synchronously relieving LiPS shuttle and promoting sulfur conversion is critical. Herein, the nitrogen evolution on hierarchical and atomistic Ni-N-C electrocatalyst, mainly pertaining to the essential subtraction, reservation and coordination of nitrogen atoms, is manipulated to attain favorable Li-S pouch cell performances. Such rational evolution behavior realizes the "nitrogen balance" in simultaneously regulating the Ni-N coordination environment, Ni single atom loading, abundant vacancy defects, active nitrogen and electron conductivity, and maximizing the electrocatalytic activity elevation of Ni-N-C system. With such merit, the cathode harvests favorable performances in a soft-packaged pouch cell prototype even under high sulfur mass loading and lean electrolyte usage. A specific energy density up to 405.1Wh kg-1 is harvested by the 0.5-Ah-level pouch cell.

Di-Pyridine-Containing Macrocyclic Triamide Fe(II) and Ni(II) Complexes as ParaCEST Agents.

Fe(II) and Ni(II) paraCEST contrast agents containing the di-pyridine macrocyclic ligand 2,2',2″-(3,7,10-triaza-1,5(2,6)-dipyridinacycloundecaphane-3,7,10-triyl)triacetamide (DETA) are reported here. Both [Fe(DETA)]2+ and [Ni(DETA)]2+ complexes were structurally characterized. Crystallographic data revealed the seven-coordinated distorted pentagonal bipyramidal geometry of the [Fe(DETA)]·(BF4)2·MeCN complex with five coordinated nitrogen atoms from the macrocyclic ring and two coordinated oxygen atoms from two amide pendant arms. The [Ni(DETA)]·Cl2·2H2O complex was six-coordinated in nature with a distorted octahedral geometry. Four coordinated nitrogen atoms were from the macrocyclic ring, and two coordinated oxygen atoms were from two amide pendant arms. [Fe(DETA)]2+ exhibited well-resolved sharp proton resonances, whereas very broad proton resonances were observed in the case of [Ni(DETA)]2+ due to the long electronic relaxation times. The CEST peaks for the [Fe(DETA)]2+ complex showed one highly downfield-shifted and intense peak at 84 ppm with another shifted but less intense peak at 28 ppm with good CEST contrast efficiency at body temperature, whereas [Ni(DETA)]2+ showed only one highly shifted intense peak at 78 ppm from the bulk water protons. Potentiometric titrations were performed to determine the protonation constants of the ligand and the thermodynamic stability constant of the [M(DETA)]2+ (M = Fe, Co, Ni, Cu, Zn) species at 25.0 °C and I = 0.15 mol·L-1 NaClO4. Metal exchange studies confirmed the stability of the complexes in acidic medium in the presence of physiologically relevant anions and an equimolar concentration of Zn(II) ions.

Bis(2-pyridyl)diimine as a naked eye colorimetric fluorescence turn off probe selectively for Fe(II) ions as a consequence of energy changes in the electronic states upon complexation

Bis(pyridyl)diimine, (1E,1′E)-N,N'-(ethane-1,2-diyl)bis(1-(pyridin-2-yl)methanimine) (L) has coordinating nitrogen atoms in effective positions to form stable chelates with metal ions and is capable of capturing a range of transition metal ions. However, the selective colorimetric response of Fe(II) by using L was observed. Colourless to purple coloured transition resulted on complexation of L with Fe(II) ions selectively and was not affected by the presence of other transition metal ions including Fe(III) ions. Photoluminescence studies have shown the quenching of emission maxima corresponding to L in the presence of Fe(II) ions along with appearance of new peaks at higher wavelength regions. Appearance of a specific color change, which can be visualized by naked eye and an added photophysical feature involving quenching of emission spectra, particularly for Fe(II) are associated with the changes in the electronic state energies of L upon complexation with Fe(II). Thermodynamic estimation of complex stability was done by determining the binding constant of the complex, which was found to be 7.2 × 1010 M−2 using Yoe Jones method. A binding ratio of 1:2 for L and Fe2+ was determined experimentally with help of mole ratio method, which hinted at the geometrical possibilities of the complex of L with Fe(II).). Limit of detection (LOD) for the identification of Fe(II) ions with L was determined using colorimetric naked eye method and was found to be 25 μM. Further L was also used to detect Fe(II) in real sample i.e. river water. NMR analysis supported the low spin state of Fe(II) in the Fe(II)-L complex. Anticipated geometry of the Fe(II)-L complex was optimized using Gaussian09 software through the B3LYP method, which upon investigation of the energies of frontier molecular orbitals, provided the details related to the electronic properties associated with the complexation of Fe(II) and L.

Identifying TM-N4 active sites for selective CO2-to-CH4 conversion: A computational study

Electrochemical CO2 reduction reaction (CO2RR) to generate CH4 is more desirable than CO. Herein, we investigate the potential of CO2-to-CH4 conversion on the representative single-atom catalysts (SACs), single transition metal atom with four coordinated nitrogen atoms embedded in graphene (TM-N4) by first-principle calculations. Interestingly, the CH4 product can be formed more favorably on TM-N4 through the key intermediate of *HCOOH instead of the traditional *CO. Among all TM-N4 candidates, Mn-, Fe-, and Ru-N4 stand out with the low limiting potentials of −0.31, −0.42, and −0.30 V, respectively. The analysis of electronic structures and charge variation shed light on the CO2RR activity origin. Moreover, it is suggested that Mn-N4 and Ru-N4 possess high CH4 selectivity owing to the suppressed hydrogen evolution reaction (HER), while the dominant HER prohibits the CH4 formation on Fe-N4. This work will provide more insights into the underlying mechanism of CO2RR and promote the explorations of TM-N4 for CO2-to-CH4 conversion.

Synergistic Catalysis of the Synthesis of Ammonia with Co-Based Catalysts and Plasma: From Nanoparticles to a Single Atom.

In this study, a series of Co nanoparticles (NPs) with different sizes and Co single-atom catalysts (SACs) with different cobalt-nitrogen coordination numbers (Co-N2, Co-N3, and Co-N4) were synthesized and applied to the synthesis of ammonia catalyzed by plasma at low temperatures and atmospheric pressures. Under the same reaction conditions, the yield of nitrogen obtained from the reduction to ammonia over a series of Co NP catalysts varies with the Co particle size. The smaller the size of the Co NPs, the greater the number of exposed active centers, and the catalytic activity is higher. Among the Co SACs, the best catalyst was Co-N2 with two coordinated nitrogen atoms, and the ammonia yield was 181 mg·h-1·gcat-1. The experimental and theoretical calculations were consistent in that a low Co-N coordination number was beneficial to the adsorption and dissociation of N2, thereby enhancing the reduction activity of N2 and promoting the increase of ammonia production.

O-Directed C-H functionalization via cobaltacycles: a sustainable approach for C-C and C-heteroatom bond formations.

This review focuses on providing comprehensive highlights of the recent advances in the field of cobalt-catalysed C-H functionalization and related synthetic concepts, relying on these through oxygen atom coordination. In recent years, 3d transition metal (Fe, Co, Cu & Ni) catalysed C-H functionalization reactions have received immense attention on account of its higher abundance and low cost, as compared to noble metals such as Ir, Rh, Ru and Pd. Among the first-row transition metals, cobalt is one of the extensively used metals for sustainable synthesis due to its unique reactivity towards the functionalization of inert C-H bonds. The functionalization of the inert C-H bond necessitates a proximal directing group. In this context, strongly coordinating nitrogen atom directed C-H functionalizations have been well explored. Nevertheless, strongly coordinating nitrogen-containing scaffolds, such as pyridine, pyrimidine, and 8-aminoquinoline, have to be installed and removed in a separate process. In contrast, C-H functionalizations through weakly coordinating atoms, such as oxygen, are largely underdeveloped. Since the oxygen atom is a part of many readily available functional groups, such as aldehydes, ketones, carboxylic acids, and esters, it could be used as directing groups for selective C-H functionalization reactions without any modification. Thus, the use of 3d transition metals, such as cobalt, along with weakly coordinating (oxygen) directing groups for C-H functionalization reactions are more sustainable, especially for the large-scale production of pharmaceuticals in industries. During the last decade, notable progress has been made using this concept. Nonetheless, almost all the reports are restricted to the formation of C-C and C-N bond. Therefore, there is a wide scope for developing this area for the formation of other bonds, such as C-X (halogens), C-B, C-S, and C-Se.

S6 N2 O15 -A Nitrogen-Poor Sulfur Nitride Oxide, and the Anhydride of Nitrido-tris-Sulfuric Acid.

The reaction of hexachlorophosphazene, P3N3Cl6, with SO3 leads to the new sulfur nitride oxide S6N2O15. The compound displays an extraordinarily low nitrogen content and exhibits a bicyclic cage structure according to the formulation N{S(O)2O(O)2S}3N, with both nitrogen atoms in trigonal planar coordination of sulfur atoms. Interestingly, the new nitride oxide can be also seen as the anhydride of nitrido‐tris‐sulfuric acid, N(SO3H)3.

Physicochemical profile of Os (III) complexes with pyrazine derivatives: From solution behavior to DNA binding studies and biological assay

New series of osmium(III) complexes with pyrazinamide (PZA) and its analogues (PTCA, PAOX) were synthesized. The physicochemical features in the solid phase have been identified and confirmed using elemental analysis, mass spectrometry, spectroscopic techniques (FT-IR, 1H NMR) and thermogravimetric analysis. Based on the studies we confirmed bidentate nature of selected pyrazine derivatives and proven involvement azomethine and amine nitrogen atoms in coordination of metal ion. In particular, complex (2) is more stable than (1) and (3), retaining thermal stability up to 120 °C. After one stage dehydration process, the simultaneous destruction of Os(III) complexes architecture was observed with immediate decomposition and elimination of pyrazine derivatives. The acid-base equilibria studies of newly synthesized Os(III) complexes were carried out by combined pH-metric-spectrophotometric and potentiometric titrations in the aqueous solution. Os(III) complexes exhibited rich redox chemistry as demonstrated by cyclic voltammetry. The cyclic voltammograms revealed a well-defined redox couples which correspond to reversible, single-electron OsIII → OsII reduction within ‐1.152 to ‐1.374 V vs Ag/AgCl and OsIII → OsIV oxidation within 0.460–0.831 V vs Ag/AgCl. The binding ability of bioactive ligand and their Os(III) complexes with Calf Thymus DNA (CT-DNA) were investigated by spectrophotometric titration. The observed hypsochromic and bathochromic shifts with simultaneous hyperchromic effect confirmed mixed mode of interaction with biological target. Biological activity of Os(III) complexes, i.e. antimicrobial, cytotoxic, haemolytic and photodynamic potential were studied.

Fine-tuning of charge transport properties of porphyrin donors for organic solar cell

To address the enhancing request of appropriate photovoltaic materials for application in renewable energy resources, an attempt has been made herein to design and investigate the novel porphyrin-based donors with higher transport properties. The interesting furan-linked porphyrin donor (FPD) and thiophene-linked porphyrin donor (TPD) containing Zn metal atom have been previously synthesized and applied into the organic solar cell. Inspired by this fascinating finding, we suggest a new set of porphyrin-based donors with high charge transport properties via designing molecular scaffolds with different numbers of coordinated nitrogen atoms (FPD-Nx and TPD-Nx, x = 0–4) and various types of metal atoms (FPD-M and TPD-M, M = Fe, Co, Ni, Cu, and Zn). Then, the structural, electronic, optical, and charge transport properties of the designed donors have been studied and compared with the available experimental results. Our calculations reveal that the FPD-N2, TPD-N2, FPD-Co, and TPD-Co porphyrins possess the planar structures, proper energy levels in reference to the PCBM acceptor, high open-circuit voltage (VOC), and excellent charge transport properties which make them ideal donors that are used in organic solar cells. Accordingly, our predicted donors represented the improvement in the structural and transport properties which may lead to organic solar cells with high power conversion efficiency. Consequently, this approach can be useful for further improving the efficiency of porphyrin donors in organic solar cells.

Twisted paddlewheel rhodium complexes: Contribution of central and axial chirality to ECD, VCD, and NMR spectra.

Dirhodium complexes bearing N-substituted chiral amino acid ligands are investigated. These complexes have an unusual twisted paddlewheel structure, showing inherent chirality. We would like to demonstrate that parallel application of chiroptical spectroscopic methods (ECD and VCD) and NMR spectroscopy combined with quantum chemical calculations constitutes a powerful tool to determine the configuration of the complexes unequivocally. Two chiroptical methods are needed to determine the absolute configuration: ECD for the coordinated nitrogen atom and VCD for the rhodium core. A quick to use NMR method is also presented: Upon the coordination of small molecules in the axial position, the relative configuration of both the rhodium core and the nitrogen atom can be determined simultaneously by studying spatial proximities provided by 1D NOE spectra.

Complete catalytic cycle of NO decomposition on a silicon-doped nitrogen-coordinated graphene: Mechanistic insight from a DFT study

The abatement of NO with efficient technology and low operation cost is still a challenging mission worldwide. By application of DFT calculations, we systematically investigate the complete catalytic cycles of NO conversion on the single Si atom doped in four pyridinic N at the divacancy site of graphene. The effects of O2, CO and water in exhausted gas are considered. The SiN4G catalyst is highly active to NO while CO is essential for recovering the catalyst surface after NO decomposition. The catalyst shows resistance to water which is a positive effect for NO abatement technology. Furthermore, the synergy between the Si atom and coordinating nitrogen atoms greatly enhances the catalytic activity towards NO reactions. This metal-free catalyst exhibits higher catalytic activity for both NO reduction and oxidation in mild conditions compared with those catalysts doped only with Si or coordinated only with N on graphene. With presence of O2, NO oxidation only requires 0.2 eV activation energy, while NO reduction also occurs easily in the absence of O2. Both oxidation and reduction reactions are exothermic processes. Therefore, incorporating Si and N on graphene could provide a low-cost and highly efficient method of fabricating catalyst for large-scale reaction of NO abatement.