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1.
A series of tris(2-aminoethylamine) (tren) capped iron(II) porphyrins has been synthesized and characterized and their affinities for dioxygen and carbon monoxide measured. The X-ray structure of the basic scaffold with nickel inserted in the porphyrin is also reported. All the ligands differ by the nature of the group(s) attached to the secondary amine functions of the cap. These various substitutions were introduced to probe if a hydrogen bond with these secondary amine groups acting as the donor could rationalize the high affinity of these myoglobin models. This work clearly indicates that the cage structure of the tren predominates over all the other appended groups with the exception of p-nitrophenol. 相似文献
2.
Carme Rovira Karel Kunc Jürg Hutter Pietro Ballone Michele Parrinello 《International journal of quantum chemistry》1998,69(1):31-35
Minimum-energy structures of O2, CO, and NO iron–porphyrin (FeP) complexes, computed with the Car–Parrinello molecular dynamics, agree well with the available experimental data for synthetic heme models. The diatomic molecule induces a 0.3–0.4 Å displacement of the Fe atom out of the porphyrin nitrogen (Np) plane and a doming of the overall porphyrin ring. The energy of the iron–diatomic bond increases in the order Fe(SINGLE BOND)O2 (9 kcal/mol) < Fe(SINGLE BOND)CO (26 kcal/mol) < Fe(SINGLE BOND)NO (35 kcal/mol). The presence of an imidazole axial ligand increases the strength of the Fe(SINGLE BOND)O2 and Fe(SINGLE BOND)CO bonds (15 and 35 kcal/mol, respectively), with few structural changes with respect to the FeP(CO) and FeP(O2) complexes. In contrast, the imidazole ligand does not affect the energy of the Fe(SINGLE BOND)NO bond, but induces significant structural changes with respect to the FeP(NO) complex. Similar variations in the iron–imidazole bond with respect to the addition of CO, O2, and NO are also discussed. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 69: 31–35, 1998 相似文献
3.
Reflected shock tube studies of high-temperature rate constants for CH3 + O2, H2CO + O2, and OH + O2
Srinivasan NK Su MC Sutherland JW Michael JV 《The journal of physical chemistry. A》2005,109(35):7902-7914
The reflected shock tube technique with multipass absorption spectrometric detection of OH-radicals at 308 nm, corresponding to a total path length of approximately 2.8 m, has been used to study the reaction CH3 + O2 CH2O + OH. Experiments were performed between 1303 and 2272 K, using ppm quantities of CH3I (methyl source) and 5-10% O2, diluted with Kr as the bath gas at test pressures less than 1 atm. We have also reanalyzed our earlier ARAS measurements for the atomic channel (CH3 + O2 --> CH3O + O) and have compared both these results with other earlier studies to derive a rate expression of the Arrhenius form. The derived expressions, in units of cm3 molecule(-1) s(-1), are k = 3.11 x 10(-13) exp(-4953 K/T) over the T-range 1237-2430 K, for the OH-channel, and k = 1.253 x 10(-11) exp(-14241 K/T) over the T-range 1250-2430 K, for the O-atom channel. Since CH2O is a major product in both reactions, reliable rates for the reaction CH2O + O2 --> HCO + HO2 could be derived from [OH]t and [O]t experiments over the T-range 1587-2109 K. The combined linear least-squares fit result, k = 1.34 x 10(-8) exp(-26883 K/T) cm3 molecule(-1) s(-1), and a recent VTST calculation clearly overlap within the uncertainties in both studies. Finally, a high sensitivity for the reaction OH + O2 --> HO2 + O was noted at high temperature in the O-atom data set simulations. The values for this obtained by fitting the O-atom data sets at later times (approximately 1.2 ms) again follow the Arrhenius form, k = 2.56 x 10(-10) exp(-24145 K/T) cm3 molecule(-1) s(-1), over the T-range, 1950-2100 K. 相似文献
4.
Torrens F 《Molecules (Basel, Switzerland)》2004,9(8):632-649
Parametrization of a molecular-mechanics program to include terms specific for five- and six-coordinate transition metal complexes results in computer-simulated structures of heme complexes. The principal new feature peculiar to five and six coordination is a term that measures the effect of electron-pair repulsion modified by the ligand electronegativity and takes into account the different structural possibilities. The model system takes into account the structural differences of the fixing centre in the haemoglobin subunits. The customary proximal histidine is added. The prosthetic group heme IX is wholly considered in our model. The calculations show clearly that certain conformations are much more favourable that others for fixing O2. From the O2 binding in haemoglobin, myoglobin and simple Fe porphyrin models it is concluded that the bent O2 ligand is best viewed as bound superoxide O2-. Axial ligands are practically free-rotating. A small modification of the model in both crystal and protein matrix affects the orientation of the ligands in experimental systems. 相似文献
5.
COx(x=1,2)and O2 chemistry play key roles in tackling global severe environmental challenges and energy issues.To date,the efficient selective electrocatalytic transformations of COx-carbon chemicals,and O2-hydrogenated products are still huge challenges.Single-atom catalysts(SACs)as atomic-scale novel catalysts in which only isolated metal atoms are dispersed on supports shed new insights in overcome these obstacles in COx and O2 chemistry,including CO oxidation,CO2 reduction reaction(CO2RR),oxygen reduction reaction(ORR),and oxygen evolution reaction(OER).In this review,the unique features and advanced synthesis strategies of SACs from a viewpoint of fundamental synthesis design are first highlighted to guide future strategy design for controllable SAC synthesis.Then,the to-date reported CO2RR,CO oxidation,OER,and ORR mechanism are included and summarized.More importantly,the design principles and design strategies of improving the intrinsic activity,selectivity,and stability are extensively discussed and the engineering strategy is classified as neighbor coordination engineering,metal-atom engineering,and substrate engineering.Via the comprehensive review and summary of state-of-the-art SACs,the synthesis–structure–property–mechanism–design principle relation can be revealed to shed lights into the structural construction of SACs.Finally,we present an outlook on current challenges and future directions for SACs in COx and O2 chemistry. 相似文献
6.
Kohei Saito Yuya Watabe Takashi Fujihara Toshiyuki Takayanagi Jun-ya Hasegawa 《Journal of computational chemistry》2020,41(11):1130-1138
Spin-inversion mechanisms in O2 binding to a model heme complex, consisting of Fe(II)-porphyrin and imidazole, were investigated using density-functional theory calculations. First, we applied the recently proposed mixed-spin Hamiltonian method to locate spin-inversion structures between different total spin multiplicities. Nine spin-inversion structures were successfully optimized for the singlet–triplet, singlet–quintet, triplet–quintet, and quintet–septet spin-inversion processes. We found that the singlet–triplet spin-inversion points are located around the potential energy surface region at short Fe–O distances, whereas the singlet–quintet and quintet–septet spin-inversion points are located at longer Fe–O distances. This suggests that both narrow and broad crossing models play roles in O2 binding to the Fe-porphyrin complex. To further understand spin-inversion mechanisms, we performed on-the-fly Born-Oppenheimer molecular dynamics calculations. The reaction coordinates, which are correlated to the spin-inversion dynamics between different spin multiplicities, are also discussed. 相似文献
7.
Crystals of the two-coordinate palladium(0) complex 1 bearing the new N-heterocyclic carbene ligand, ITmt, directly and rapidly fixed both O2 and CO2 from air to produce the corresponding palladium(II) peroxocarbonate complex 2. The present reaction consists of dioxygenation of the palladium(0) complex 1 to the palladium(II) peroxo complex 3 and the subsequent CO2 insertion to produce the peroxocarbonate complex 2. Reaction of the crystals of 1 with air was monitored by microscopic IR spectroscopy to confirm the sequence of the two-step solid-state reaction. The unique reactivity of solid 1 toward air was explained in terms of the structural features of the carbene ligand, ITmt. 相似文献
8.
V. D. Nissenbaum V. V. Rozanov V. N. Gel'man E. Z. Golosman A. M. Rubinshtein S. V. Krashennikov V. I. Yakerson 《Russian Chemical Bulletin》1978,27(10):1972-1977
Conclusions The relation between the thermodesorption parameters for Co, CO2, and H2O and the activity of copper oxide-zinc-aluminum-calcium catalysts has been discussed. It is suggested that high catalytic activity is associated with high CO, and low CO2 and H2O, adsorption on the nonuniform surface. The thermodesorption parameters are determined by the oxidation-reduction treatment to which the catalyst has been subjected.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2233–2238, October, 1978.For Communication 12, cf. [1]. 相似文献
9.
《Journal of Coordination Chemistry》2012,65(20):3662-3675
The structure of 1 consists of [Cu(HCp)(phen)(H2O)]2+ (HCp is ciprofloxacin and phen is 1,10-phenanthroline), two acetates, and four free water molecules. In each cation, copper displays a distorted square pyramid, coordinated to ring 3-carboxylate and 4-oxo oxygen from HCp, two nitrogens from phen, and one water molecule. There are five water molecules in each discrete complex with one coordinated to Cu center, and the other four linked to each other by intermolecular hydrogen bonds. Two uncoordinated acetates make the compound neutral. The complex exhibits higher DNA binding compared to HCp at the same conditions by fluorescence and viscosity measurements. Combining its structure with the DNA-binding result, the binding mechanism may be explained by intercalation. Moreover, 1 shows significant cleavage of DNA in the presence of a reducing agent, such as ascorbate by gel electrophoresis using supercoiled pBR322 DNA in Tris-HCl buffer (pH 7.4). The complex also has a higher activity against Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Klebsiella pneumoniae than HCp. 相似文献
10.
The divalent thulium complex [Tm(Cpttt)2] (Cpttt = 1,2,4-tris(tert-butyl)cyclopentadienyl) reacts with CO to afford selective CO reductive dimerization and trimerization into ethynediolate (C2) and ketenecarboxylate (C3) complexes, respectively. DFT calculations were performed to shed light on the elementary steps of CO homologation and support a stepwise chain growth. The attempted decoordination of the ethynediolate fragment by treatment with Me3SiI led to dimerization and rearrangement into a 3,4-dihydroxyfuran-2-one complex. Investigation of the reactivity of the C2 and C3 complexes towards other electrophiles led to unusual functionalization reactions: while the reaction of the ketenecarboxylate C3 complex with electrophiles yielded new multicarbon oxygenated complexes, the addition of CO2 to the ethynediolate C2 complex resulted in the formation of a very reactive intermediate, allowing C–H activation of aromatic solvents. This original intermolecular reactivity corresponds to an unprecedented functionalization of CO-derived ligands, which is induced by CO2.The divalent thulium complex [Tm(Cpttt)2] activates CO to form reductive CO dimerization or trimerization products. These complexes further react with electrophiles, including CO2, yielding multicarbon oxygenates and original C–H activation products. 相似文献
11.
Gas isotope ratio mass spectrometers usually measure ion current ratios of molecules, not atoms. Often several isotopologues contribute to an ion current at a particular mass‐to‐charge ratio (m/z). Therefore, corrections have to be applied to derive the desired isotope ratios. These corrections are usually formulated in terms of isotope ratios (R), but this does not reflect the practice of measuring the ion current ratios of the sample relative to those of a reference material. Correspondingly, the relative ion current ratio differences (expressed as δ values) are first converted into isotopologue ratios, then into isotope ratios and finally back into elemental δ values. Here, we present a reformulation of this data reduction procedure entirely in terms of δ values and the ‘absolute’ isotope ratios of the reference material. This also shows that not the absolute isotope ratios of the reference material themselves, but only product and ratio combinations of them, are required for the data reduction. These combinations can be and, for carbon and oxygen have been, measured by conventional isotope ratio mass spectrometers. The frequently implied use of absolute isotope ratios measured by specially calibrated instruments is actually unnecessary. Following related work on CO2, we here derive data reduction equations for the species O2, CO, N2O and SO2. We also suggest experiments to measure the required absolute ratio combinations for N2O, SO2 and O2. As a prelude, we summarise historic and recent measurements of absolute isotope ratios in international isotope reference materials. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
12.
Haack P Limberg C Tietz T Metzinger R 《Chemical communications (Cambridge, England)》2011,47(22):6374-6376
The first structural characterisation of a copper-carbondisulfide complex revealed a hitherto unknown binding mode for CS(2): it interacts with two metal centres (Cu(I)) simultaneously via both C=S π bonds. DFT calculations showed that complex formation occurs mainly due to a donation of electron density from the copper centres into the C=S π* orbitals. 相似文献
13.
A structural and functional mimic of the galactose oxidase (GOase) enzyme active-site by a copper complex supported over a sterically demanding ligand having [N2O2] donor sites is reported. Specifically, the binding of the histidine (496 and 581) and tyrosine (272 and 495) residues to the copper center in a square-pyramidal fashion in the active-site of galactose oxidase (GOase) enzyme has been modeled in a copper complex, ([(3-tert-butyl-5-methyl-2-hydoxybenzyl)(3'-tert-butyl-5'-methyl-2'-oxobenzyl)(2-pyridylmethyl)]amine)Cu(OAc)) (1b), stabilized over a sterically demanding ligand in which the two phenolate-O atoms mimicked the tyrosine binding while an amine-N and pyridyl-N atoms emulated the histidine binding to the metal center, similar to that in the enzyme active-site. Furthermore, the copper complex 1b is found to be an effective functional model of the enzyme as it efficiently catalyzed the chemoselective oxidation of primary alcohols to aldehydes in high turnover numbers under ambient conditions. An insight into the nature of the active-species was obtained by EPR and CV studies, which in conjunction with the DFT studies, revealed that the active-species is an anti-ferromagnetically coupled diamagnetic radical cation, (1)1b+, obtained by one electron oxidation at the equatorial phenolate-O atom of the ligand in the 1b complex. 相似文献
14.
In our developing world, carbon dioxide has become one of the most abundant greenhouse gases in the atmosphere. It is a stable, inert, small molecule that continues to present significant challenges toward its chemical activation as a useful carbon end product. This tutorial review describes one approach to the reduction of carbon dioxide to carbon fuels, using cobalt and nickel molecular catalysts, with particular focus on studying the thermodynamics and kinetics of CO(2) binding to metal catalytic sites. 相似文献
15.
Fachinetti G Funaioli T Marchetti F 《Chemical communications (Cambridge, England)》2005,(23):2912-2914
The reaction with water of acyldicarbonyl-Ru(II) complexes relevant to ruthenium catalysed ethene hydrocarbonylation with CO/H2O is shown to consist of a nucleophilic attack and to proceed via coordination of propionate and CO to the Ru(II) species. 相似文献
16.
《Surface and interface analysis : SIA》2005,37(7):633-640
Metastable impact electron spectroscopy (MIES), ultraviolet photoelectron spectroscopy (UPS(HeI)) and x‐ray photoelectron spectroscopy (XPS) were applied to study the interaction of O2, CO and CO2 with Co films at room temperature. The films were produced on Si(100) surfaces under the in situ control of MIES, UPS and scanning tunnelling microscopy (STM). For O2, dissociative adsorption takes place initially and then incorporation of oxygen starts at exposures of ~5 L. Comparison of the MIES and UPS spectra with those published for CoO shows that near‐stoichiometric CoO films can be obtained by co‐deposition of Co and O2. The CO is adsorbed molecularly up to a maximum coverage of ~0.6 monolayer, with the C‐end pointing towards the surface. The CO2 adsorption is dissociative, resulting in the formation of Co–CO bonds at the surface. The resulting oxygen atoms are mostly incorporated into the Co layer. For all studied molecules the interaction with Co is similar to that with Ni. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
17.
Pulsed laser photolysis of O3 in a large excess of N2 has been used to generate O(3P) atoms in the presence of OCS. By observing chemiluminescence from the small fraction of electronically excited SO2 formed in the reaction of SO with O3, rate constants of (1.7 ± 0.2) × 10?14 and (8.7 ± 1.6) × 10?14 cm3/molecule sec have been determined at 296 ± 4 K for the reactions and In addition, it has been shown that any reaction between SO and OCS has a rate constant 10?14 cm3/molecule sec. 相似文献
18.
《Sensors and Actuators》1984,5(3):181-186
A gas sensor based on polymer-covered interdigitated electrodes is described and some preliminary results for CO, CO2, CH4 and H2O are presented. It is known that the permittivity and conductivity of a polymer such as polyphenylacetylene (PPA) changes slightly upon absorption of gases. To measure this sensitivity, interdigitated electrode structures were fabricated with an area of 1.2×1.6 mm2 and electrode widths and distances of 10 μm; the structures were covered with 0.77 μm PPA. Measurements were performed at room temperature for frequencies between 100 Hz and 100 kHz and pressures between 0 and 20 mmHg. 相似文献
19.
B Horn C Limberg C Herwig M Feist S Mebs 《Chemical communications (Cambridge, England)》2012,48(66):8243-8245
Reaction of a nickel(0) carbonyl complex, K(2)[L(tBu)NiCO](2), with N(2)O generates a cyclic carbonate compound composed of six [Ni(II)(CO(3))K](+) units. The same product can also be obtained using O(2) as the oxidant in a solid-state/gas reaction. These conversions represent unique examples of a nickel-bound CO oxidation by N(2)O and O(2), respectively. 相似文献
20.
An activation energy of Ea=213.73 kJ mol–1 has been determined for the thermal decomposition of SmC2O4Cl to SmOCl, CO and CO2. The result is predictable on the basis of the Kahwa-Mulokozi expression + for the activation energy and its extended interpretation.
On study leave from the university of sokoto, Nigeria. 相似文献
Zusammenfassung Für den thermischen Zerfall von SmC2O4Cl in SmOCl, CO und CO2 wurde eine Aktivierungsenergie vonE a=213.73 kJ.mol–1 ermittelt. Dieses Ergebnis kann auf der Basis der Kahwa-Mulokozi-Beziehung für die Aktivierungsenergie und ihrer erweiterten Interpretation vorhergesagt werden.
On study leave from the university of sokoto, Nigeria. 相似文献