CO2 Complex Research Articles

Theoretical investigation of the vibrational structure of the Ar–CO2 complex

We develop a new flexible-monomer two-body ab initio potential energy surface (PES) for the Ar−CO2 complex. The accuracy of this new potential function is validated by its agreement in the vibrational spectrum of the complex. Vibrational self-consistent field theory (VSCF) and vibrational configuration interaction (VCI) theory were employed to solve the complete vibrational Hamiltonian, including both intermolecular and intramolecular degrees of freedom. We observe excellent agreement with theoretical and experimental results for the vibrational energy levels in the Terahertz region. In the intramolecular region, we confirm the slight splitting of the bending modes of the CO2 monomer, where the in-plane bend is 0.83 cm−1 less energetic than the out-of-plane mode. We also explore the combination bands in the asymmetric stretching region of the CO2 monomer that involve the intermolecular motions, and show that these results compare favorably to the fundamental intermolecular vibrational energy levels.

Ensuring the strength of welded joints in laser welding of EP693 heat-resistant dispersion-hardening nickel alloy

The paper considers the process of creating a permanent connection from the EP693 heat-resistant alloy of the Ni-Cr-W-Co-Mo system used in the manufacture of components and parts of gas turbine engines by welding on the TruLaser Cell 7020 CO2 complex with pulse-periodic radiation. EP367 filler wire of the Ni—Mo—Cr—Mn system was used to obtain the weld. The influence of heat treatment on the structure and properties of the heat-affected zone and the weld was studied. Based on the research results, the weld structure and kinks obtained by laser welding was studied, weld physical and mechanical properties were identified, the maximum endurance limit for welded joints was determined at 2•106 cycles. The expediency of laser welding of the heat-resistant dispersion-hardening nickel alloy in the manufacture of shells for the turbine support and stator of gas turbine engines was determined. It was found that combined heat treatment (quenching and aging) provides optimal values of strength limits at room and elevated temperatures, as well as short-term strength of welded joints. Based on the strength calculation of the turbine support and stator of gas turbine engines and the obtained experimental data on the strength of welded joints made using laser welding with pulse-periodic radiation, the safety factor was 1.35 to 3.0. This technology is proposed to be introduced into production in the manufacture of parts and assemblies such as shells for the turbine support and stator of gas turbine engines in order to improve the quality of welds by reducing the time of high-temperature heating due to lower heat input.

Theoretical studies on complexes with ammonia: comparison with H2O complexes: hydrogen bonding

High-level theoretical results for structures, dissociation energies and vibrational frequencies of the ammonia complexes NH3–N2, NH3–CO, NH3–O2, NH3–NO, NH3–H2, NH3–F2, NH3–HF, NH3–Ne, NH3–Ar, NH3–CO2, NH3–N2O and NH3–NH3 are reported, and compared with results for corresponding complexes of H2O. While complexes of H2O with N2, CO, NO, Ne, Ar and NH3 are hydrogen bonded, of the complexes with NH3 only NH3-NH3 qualifies. However, for NH3–CO, NH3–N2 and NH3-Ne structures with weak hydrogen bonding are predicted by present theoretical results. Structures of H2, F2, HF, CO2 and N2O complexes with NH3 are similar to those with H2O, not hydrogen bonded, having AB face N of NH3. Their dissociation energies De are close to those of H2O-AB. Due to complex formation, some large changes are noted in vibrational frequencies and infrared intensities, especially for the NH3 dimer and for NH3–HF.

Tuning Oxygen Reduction Catalysis of Dinuclear Cobalt Polypyridyl Complexes by the Bridging Structure.

The four-electron oxygen reduction reaction (4e--ORR) is the mainstay in chemical energy conversion. Elucidation of factors influencing the catalyst's reaction rate and selectivity is important in the development of more active catalysts of 4e--ORR. In this study, we investigated chemical and electrochemical 4e--ORR catalyzed by Co2(μ-O2) complexes bridged by xanthene (1) and anthracene (3) and by a Co2(OH)2 complex bridged by anthraquinone (2). In the chemical ORR using Fe(CpMe)2 as a reductant in acidic PhCN, we found that 1 showed the highest initial turnover frequency (TOFinit = 6.8 × 102 s-1) and selectivity for 4e--ORR (96%) in three complexes. The detailed kinetic analyses have revealed that the rate-determining steps (RDSs) in the catalytic cycles of 1-3 have the O2 addition to [CoII2(OH2)2]4+ as an intermediate in common. In the only case that complex 1 was used as a catalyst, kcat depended on proton concentration because the reaction rate of the O2 addition to [CoII2(OH2)2]4+ was so fast as compared to that of the concerted PCET process of 1. Through X-ray, Raman, and electrochemical analyses and stoichiometric reactions, we found the face-to-face structure of 1 characterized by a slightly flexible xanthene was advantageous in capturing O2 and stabilizing the Co2(μ-O2) structure, thus increasing both the reaction rate and selectivity for 4e--ORR.

Thermally resilient cobalt ethylene polymerization catalysts under the joint influence of co-catalyst, gem-dimethyl substitution and ortho-cycloalkyl ring size

The N,N,N′-chelated 2-(1-arylimino)ethyl-8-arylimino-7,7-dimethyl-5,6- dihydroquinoline-cobalt (II) chloride complexes, Co1 (aryl = 2-(C5H9)-6-MeC6H3), Co2 (aryl = 2-(C6H11)-6-MeC6H3), Co3 (aryl = 2-(C8H15)-6-MeC6H3), Co4 (aryl = 2-(C5H9)-4,6-Me2C6H2), Co5 (aryl = 2-(C6H11)-4,6-Me2C6H2) and Co6 (aryl = 2-(C8H15)-4,6-Me2C6H3), have been isolated in reasonable yield using a simple one-pot method. The molecular structures of Co1 and Co5 emphasize not only the gem-dimethyl-substitution present in the carbocyclic-fused tridentate ligand but also the substantial steric properties exerted by the ortho-cycloalkyl groups. Complexes Co1 – Co6, on interaction with MAO, were highly active catalysts for ethylene polymerization reaching a maximum level of 9.21 × 106 g PE mol−1 (Co) h−1 at 70 °C for cyclopentyl-containing Co1 and Co4. Strictly linear polyethylenes with low molecular weights (Mw range: 9.25–38.5 kg mol−1) and narrow dispersities were generated with selectivities for vinyl-terminated polymers approaching quantitative levels. By comparison, polymerizations conducted using Co1 – Co6 with MMAO as co-catalyst proved less thermally stable and less active, with vinyl chain-end selectivity proving temperature dependent. Common to both MAO and MMAO, the most sterically hindered precatalyst Co6 incorporating an ortho-cyclooctyl group gave the highest molecular weight polymer of the series.

CO2 Derivatives of Molecular Tin Compounds. Part 2: Carbamato, Formato, Phosphinoformato and Metallocarboxylato Complexes

Single-crystal X-ray diffraction structures of organotin compounds bearing hemicarbonate and carbonate ligands were recently reviewed by us—“CO2 Derivatives of Molecular Tin Compounds. Part 1: Hemicarbonato and Carbonato Complexes”, Inorganics 2020, 8, 31—based on crystallographic data available from the Cambridge Structural Database. Interestingly, this first collection revealed that most of the compounds listed were isolated in the context of studies devoted to the reactivity of tin precursors towards carbon dioxide, at atmospheric pressure or under pressure, thus highlighting the suitable disposition of Sn to fix CO2. In the frame of a second part, the present review carries on to explore CO2 derivatives of molecular tin compounds by describing successively the complexes with carbamato, formato, and phosphinoformato ligands, and obtained from insertion reactions of carbon dioxide into Sn–X bonds (X = N, H, P, respectively). The last chapter is devoted to X-ray structures of transition metal/tin CO2 complexes exhibiting metallocarboxylato ligands. As in Part 1, for each tin compound reported and when described in the original study, the structural descriptions are supplemented by synthetic conditions and spectroscopic data.

Side-on Coordination in Isostructural Nitrous Oxide and Carbon Dioxide Complexes of Nickel.

A nickel complex incorporating an N2O ligand with a rare η2‐N,N′‐coordination mode was isolated and characterized by X‐ray crystallography, as well as by IR and solid‐state NMR spectroscopy augmented by 15N‐labeling experiments. The isoelectronic nickel CO2 complex reported for comparison features a very similar solid‐state structure. Computational studies revealed that η2‐N2O binds to nickel slightly stronger than η2‐CO2 in this case, and comparably to or slightly stronger than η2‐CO2 to transition metals in general. Comparable transition‐state energies for the formation of isomeric η2‐N,N′‐ and η2‐N,O‐complexes, and a negligible activation barrier for the decomposition of the latter likely account for the limited stability of the N2O complex.

Side‐on Coordination in Isostructural Nitrous Oxide and Carbon Dioxide Complexes of Nickel

AbstractA nickel complex incorporating an N2O ligand with a rare η2‐N,N′‐coordination mode was isolated and characterized by X‐ray crystallography, as well as by IR and solid‐state NMR spectroscopy augmented by 15N‐labeling experiments. The isoelectronic nickel CO2 complex reported for comparison features a very similar solid‐state structure. Computational studies revealed that η2‐N2O binds to nickel slightly stronger than η2‐CO2 in this case, and comparably to or slightly stronger than η2‐CO2 to transition metals in general. Comparable transition‐state energies for the formation of isomeric η2‐N,N′‐ and η2‐N,O‐complexes, and a negligible activation barrier for the decomposition of the latter likely account for the limited stability of the N2O complex.

Biological and electrochemical studies of Co2+, Ni2+, Cu2+, Zn2+ and Cd2+ metal complexes of Schiff base ligand derived from 4-amino benzoic acid and isonicotinic hydrazide

Ten metal complexes of Co2+, Ni2+, Cu2+, Zn2+ and Cd2+ were synthesized by two novel Schiff bases derived from condensation of m-pthalaldehyde with 4-amino benzoic acid and isonicotinic hydrazide. The as-synthesized metal complexes were characterized and explored by different spectroscopic techniques. FT-IR spectra have confirmed the presence of C=N bands as well as UV–Vis spectroscopy in both Schiff bases KM-1 and KM-2. All as-prepared compounds were evaluated for the antimicrobial activities against the Escherichia coli and Propionibacterium acnes. KM-1 and its metal complexes have shown efficient results compared to KM-2. The electrochemical study of M2+ complexes by cyclic voltammograms in electrolyte solution (Pt electrode) demonstrated electrochemically irreversible oxidative and reductive responses.

Characterizing hydrogen and tetrel bonds in clusters of CO2 with carboxylic acids.

The interaction between carbon dioxide and planar carboxylic acids has been investigated through the analysis of the microwave spectrum of the acrylic acid·CO2 complex and quantum chemical modeling of the R-COOH·(CO2)1,16 clusters, where R = H, CH2CH. As regards the 1 : 1 compounds, two species, involving the s-cis and s-trans conformers of acrylic acid were observed. For both of them, a similar bidentate interaction arises between the carbonyl group of CO2 and the carboxylic group of the organic acid, leading to the formation of a planar six-membered ring. The binding energy is estimated to be De ≃ 21 kJ mol-1, 1/3 being the energy contributions of the tetrel to hydrogen bonds, respectively. In the 1 : 16 clusters, the ring arrangement is broken, allowing for the interaction of the acid with several CO2 molecules. The CO2 molecules completely surround formic acid, whereas, in the case of acrylic acid, they tend to avoid the allyl chain.

Competitive tetrel bond and hydrogen bond in benzaldehyde-CO2: characterization via rotational spectroscopy.

The rotational spectrum of the 1 : 1 benzaldehyde-CO2 complex has been investigated using pulsed-jet Fourier transform microwave spectroscopy complemented with quantum chemical calculations. Two isomers, both characterized by one C⋯O tetrel bond (n → π* interaction) and one C-H⋯O hydrogen bond (n → σ* interaction), have been observed in the pulsed jet. Competition between the tetrel bond and the hydrogen bond has been disclosed by natural bond orbital analysis: isomer I is characterized by one dominating OCCO2⋯O tetrel bond (12.6 kJ mol-1) and a secondary (C-H)formyl⋯O hydrogen bond (2.2 kJ mol-1); by contrast, in isomer II the (C-H)phenyl⋯O hydrogen bond (7.6 kJ mol-1) becomes the dominant bond, while the OCCO2⋯O tetrel bond (5.8 kJ mol-1) becomes much weaker with respect to that of isomer I. Using intensity measurements the relative population ratio of the two isomers was estimated to be NI/NII ≈ 2/1.

Theoretical and experimental studies of the isotope effects for He–CO2 and Ne–CO2 complexes

In this work, we have studied the isotope effects for the He–CO2 and Ne–CO2 complexes by means of theoretical calculations and experimental measurements, which were carried out using a distributed quantum cascade laser to probe a pulsed supersonic jet expansion. Firstly, infrared spectra have been recorded for the He/Ne–12C18O2 complexes. Spectroscopic parameters including band origin ν0, rotational constants A, B, C, and centrifugal distortion constants ΔJK were obtained by fitting a Watson A-reduced Hamiltonian with 13 assigned rovibrational transitions for He–12C18O2. For Ne–12C18O2, the observed spectrum produces a set of spectroscopic parameters including the band origin, rotational constants and all the quartic centrifugal distortion constants with more than 100 rovibrational transitions (40 new transitions). Secondly, we have calculated the rovibrational energy levels, vibrational shifts, and rotational constants for the He/Ne–CO2 complexes based on potential energy surfaces (PESs) and bound state calculations for ground and vibrationally excited states. The obtained results show that the spectroscopic characteristics (vibrational shifts and rotational constants) for Ne–CO2 are analogous to those of Ar–CO2, while those for He–CO2 show some differences especially for the rotational constants. Finally, according to the available experimental data and our theoretical calculations, infrared spectra were predicted for six isotopologues with C2v symmetry of Ne–CO2 complex.

One-dimensional metal-organic nanowires-derived catalyst of carbon nanobamboos with encapsulated cobalt nanoparticles for oxygen reduction

One-dimensional (1D) metal-organic nanostructures hold great promise for preparing various 1D carbon/metal derivatives toward various electrocatalysis including oxygen reduction reaction (ORR); but it is challenging to synthesize them. Herein, 1D cobalt(Co)-metal-organic nanowires are prepared using the complex of Co2+ and 1, 2, 4-triazole. Direct carbonization of the as-prepared nanowires affords a well-defined structure of Co nanoparticles encapsulated inside the bamboo-liked 1D carbon nanostructure, i.e., carbon nanobamboos (Co@CNB). Owing to the outstanding electronic transport in bamboo-liked carbon structure, strong electronic coupling between the N-doped carbon and Co nanoparticles, the Co@CNB catalyst exhibits an excellent ORR performance comparable to the commercial Pt/C in alkaline solution. Density functional theory (DFT) calculations reveal that the Co@CNB can strengthen the adsorption of all adsorbates (O*, OH* and OOH*) compared with a carbon nanotube, benifical for oxygen protonation and thus enhancing the ORR activity. Moreover, it is possible to outperform Pt intrinsically if the curvature of carbon shell is high enough in Co@CNB. Lastly, the zinc-air battery (ZAB) fabricated with Co@CNB as the cathode catalyst shows a higher peak power density and better cycling durability than those of the ZAB with Pt/C; suggesting the great potential of Co@CNB as efficient electrocatalysts for metal-air batteries.

Synthesis, characterization and biological evaluation of thiazolyl azo ligand complexes with some metal ions

(E)-2-(benzo[d]thiazol-2-yliazenyl)-4-methoxyaniline was synthesized by reaction the diazonium salt of 2-aminobenzothiazole with 4-methoxyaniline. Identified of the ligand by spectral techniques (UV-Vis, FTIR, 1HNMR and LC-Mass) and microelemental analysis (C.H.N.S.O) are used to produce of the azo ligand. Complexes of (Co2+, Ni2+, Cu2+ and Zn2+) were synthesized and identified using atomic absorption of flame, elemental analysis, infrared and UV-Vis spectral process as well conductivity and magnetic quantifications. Nature of compounds produced have been studied followed the mole ratio and continuous contrast methods, Beer’s law followed during a concentration scope (1×10−4-3×10−4 mole/L). height molar absorptivity of compound solutions have been noticed. Analytical data showed that all the complexes out to 1:2 metal-ligand ratio. At the radix for physicochemical datum an octahedral structure have been described at compounds. other than the biological studies of all produced compounds was evaluation against different kinds of antimicrobial strains.

Revisiting the 2-imino-1,10-phenanthrolylmetal precatalyst in ethylene oligomerization: Benzhydryl-modified cobalt(II) complexes and their dimerization of ethylene

The ortho-benzhydryl substituted 2-imino-1,10-phenanthrolylcobalt(II) dichlorides Co1-Co8 have been prepared by the direct reaction of the corresponding compartmental ligands L1–L8 and cobalt(II) chloride with good yields. All the organic compounds (L1–L8) have been fully characterized by FT-IR, 1H/13C NMR spectroscopy and elemental analysis, and their corresponding cobalt complexes (Co1–Co8) have been characterized by FT-IR spectroscopy and elemental analysis, along with the single crystal X-ray diffraction for the representative complexes Co3, Co7 and Co8. On treatment with modified methylaluminoxane (MMAO), all the cobalt complexes Co1-Co8 display good activities (up to 3.25 × 105 g mol−1 (Co) h−1 at 50 °C) toward ethylene dimerization (C4 ranging from 92 to 100%), along with minor hexenes, in which the selectivity of 2-butene ranges from 55 to 84.4%. In comparison with their previous analogues, the current precatalysts bear bulkier substituents which are not beneficial to ethylene oligomerization.

Growth Pattern, Stability, and Properties of Complexes of C2H5OH and nCO2 (n = 1-5) Molecules: A Theoretical Study.

This work is dedicated to theoretically investigate the formation process of C2H5OH···nCO2 (n = 1–5) complexes and to shed light on the nature of interactions formed under the variation of CO2 concentration. It is found that CO2 molecules tend to locate around the polarized −OH group to interact with the lone pairs of the O atom. The interaction of ethanol with three CO2 molecules (C2H5OH···3CO2) induces the most stable structure in the sequence considered. The atoms in molecules (AIM), NCIplot, and natural bond orbital (NBO) analyses point out that the Oethanol···CCO2 tetrel bond overcomes hydrogen, chalcogen, and CO2···CO2 tetrel-bonded interactions and mainly contributes to the strength of C2H5OH···nCO2 (n = 1–5) complexes. All intermolecular interactions in the examined complexes are weakly noncovalent, and their positive cooperativity is evaluated to be slightly weaker than that of CO2 pure systems. SAPT2+ and molecular electrostatic potential (MEP) calculations indicate that the electrostatic force is the main factor underlying the attractive interplay in the complexes of C2H5OH and CO2.

The hazardous effects of the environmental toxic gases on amyloid beta-peptide aggregation: A theoretical perspective

Alzheimer's disease (AD) is one of the leading causes of dementia in elderly people. It has been well documented that the exposure to environmental toxins such as CO, CO2, SO2 and NO2 that are present in the air is considered as a hallmark for the progression of Alzheimer's disease. However, their actual mechanism by which environmental toxin triggers the aggregation of Aβ42 peptide at the molecular and atomic levels remain unknown. In this study, molecular dynamics simulation was carried out to study the aggregation mechanism of the Aβ42 peptide due to its interaction of toxic gas (CO, CO2, SO2 and NO2). During the 400 ns simulation, all the Aβ42 interacted toxic gas (CO, CO2, SO2, and NO2) complexes have smaller Root Mean Square Deviation values when compared to the Aβ42 peptide, which shows that the interaction of toxic gases (CO, CO2, SO2, and NO2) would increase the Aβ42 peptide structural stability. The radius of gyration analysis also supports that Aβ42 interacted CO2 and SO2 complexes have the minimum value in the range of 0.95 nm and 1.5 nm. It is accounted that the Aβ42 interacted CO2 and SO2 complexes have a greater compact structure in comparison to Aβ42 interacted CO and NO2 complexes. Furthermore, all the Aβ42 interacted toxic gas (CO, CO2, SO2, and NO2) complexes exhibited an enhanced secondary structural probability for coil and turn regions with a reduced α-helix probability, which indicates that the interaction of toxic gases may enhance the toxicity and aggregation of Aβ42.

The Highly Efficient Absorption of CO2 by a Novel DBU Based Ionic Liquid

A novel anion-functionalized protic ionic liquid (IL), [DBUH][Triz], has been synthesized from 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU) and 1,2,4-triazole (Triz). Density (ρ) and viscosity (η) of [DBUH][Triz] at different temperatures have been measured and the influence of temperature has been analyzed quantitatively. Then, the applications of [DBUH][Triz] in CO2 absorption have been investigated. It has been detected that this ionic liquid, which was easily prepared, shows excellent reversibility and a high absorption capacity, about 1.5 mol CO2 per 1 mol of IL (about 0.3 g CO2 per 1 g of IL). In addition, the influence of temperature, pressure and moisture on the absorption performance of [DBUH][Triz] has been studied separately, indicating that absorption is promoted by lower temperature and higher CO2 pressure. In addition, the mechanism of chemical absorption at two active sites has been deduced based on quantum-chemical calculations and 13C NMR spectra coupled with IR spectra. Furthermore, the equilibrium constant of chemical absorption (K) was calculated from the CO2 capacity at different temperatures (T) and a good linear relationship between the natural logarithm of the equilibrium constant ln K and 1/T was obtained with R2 of 0.996. From the slope and intercept of the fitted straight line, the molar reaction enthalpy change (ΔrHm) and molar reaction entropy change (ΔrSm) were analyzed, indicating that the capture of CO2 is an exothermic process and the IL–CO2 complex is less ordered than the pure ionic liquid.

The Ethylene-Carbon Dioxide Complex and the Double Rotor Model.

The infrared spectrum of the weakly bound C2H4-CO2 complex is investigated in the region of the ν3 fundamental band of CO2 (≈2350 cm-1), using a tunable OPO laser source to probe a pulsed supersonic slit jet expansion. The spacing of the various K-subbands in this perpendicular (ΔK = ±1) spectrum is very irregular, and the pattern of irregularity is quite different from that observed previously in another C2H4-CO2 band by Bemish et al. [ J. Chem. Phys. 1995 , 103 , 7788 ]. But by allowing for the different symmetry of the ν3 (CO2) upper vibrational state, both results can be strikingly well explained using the "double internal rotor" model as described by Bemish et al.

Solvent-Induced Structural Diversity and Magnetic Research of Two Cobalt(II) Complexes.

The solvent-induced topological and structural diversities of two Co(II) complexes, namely, [Co(L)2(SCN)2] (Co1) and [Co2(L)2(SCN)(OAc)3] (Co2) (L = 8-methoxyquinoline), were comparatively analyzed. Certain proportions of L, Co(OAc)2·4H2O, and NaSCN were mixed and dissolved in CH3OH at 60 °C to obtain complex Co1. Complex Co2, an asymmetric dinuclear compound, was obtained by simply replacing CH3OH with CH3CN as the solvent. The Co(II) ion in complex Co1 was coordinated by the N4O2 mode provided by two L ligands and two SCN– anions. The two Co(II) ions in Co2 were in the N2O4 and NO5 coordination environment and were linked by two μ2-OAc– bridges and one rare μ3-OAc– bridge. Weak interaction analysis revealed that complexes Co1 and Co2 exhibited 6-connected shp and 14-connected fcu nets, respectively. Magnetic studies showed that Co1 demonstrated single-ion magnet behavior under 2000 Oe. These behaviors are indicative of clearly field-induced single-ion magnetic behavior with Ueff = 34.7(2) K and τ0 = 2.7(2) × 10–7 s under 2000 Oe dc field, respectively. By contrast, Co2 lacked frequency dependence under zero-field conditions. Electrospray ionization mass spectrometry indicated that two complexes were stable in N,N-dimethylformamide.