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1.
We report absorption spectra from the ground state to the photoexcited triplet state of platinum porphin (PtP) in single crystals of n-octane (C8) and n-decane (C10) at 4.2 K, with and without a magnetic field. For PtP in C10 the same transition was studied in emission. From the experiments, values are derived of the spin-orbit coupling parameter Z, the crystal field splitting δ and the orbital angular momentum A for PtP in the two hosts: Z = 76 ± 2 cm?1 (C8, C10), δ = 71 ± 1 cm?1 (C8), 55 ± 1 cm?1 (C10) and A = 1.6 ± 0.1 (C8, C10). For the ratio of the in-plane and the z-polarized electric dipole transition moments we obtain ¦Mx,y¦/¦Mz¦=76± 0.3 (C8).  相似文献   

2.
The average downward collisional energy transfer (<ΔEdown>) is obtained for highly vibrationally excited tert-butyl chloride, both undeuterated and per-deuterated, with Kr, N2, CO2, and C2H4 bath gases, at ca. 760 K. Data are obtained using the technique of pressure-dependent very low-pressure pyrolysis. Reactant internal energies to which the data are sensitive are in the range 200–250 kJ mol?1. For C4H9Cl, the <ΔEdown> values (cm?1) are 255 (Kr), 265 (N2), 440 (CO2), and 585 (C2H4), and for C4D9Cl, 245 (N2), 370 (CO2), and 540 (C2H4). The uncertainties in these values are ca. 20% (40% for Kr); the uncertainties in the deuteration ratios are 10–15%. The value for Kr is in agreement with theoretical predictions of a biased random walk model for internal energy change in monatomic/substrate collisions. The effect of deuteration of <ΔEdown> is also in accord with that predicted by a modification of the theory. Extrapolated highpressure rate coefficients for the thermal decomposition of reactant are 1013.6 exp(-187 kJ mol?1/RT) s?1 (C4H9Cl) and 1014.2 exp(?196 kJ mol?1/RT) s?1 (C4D9Cl), in accord with other studies and the expected isotope effect.  相似文献   

3.
The 300 K reactions of O2 with C2(X 1Σ+g), C2(a 3 Πu), C3(X? 1Σ+g) and CN(X 2Σ+), which are generated via IR multiple photon dissociation (MPD), are reported. From the spectrally resolved chemiluminescence produced via the IR MPD of C2H3CN in the presence of O2, CO molecules in the a 3Σ+, d 3Δi, and e 3Σ? states were identified, as well as CH(A 2Δ) and CN(B 2Σ+) radicals. Observation of time resolved chemiluminescence reveals that the electronically excited CO molecules are formed via the single-step reactions C2(X 1Σ+g, a 3Πu) + O2 → CO(X 1Σ+ + CO(T), where T denotes are electronically excited triplet state of CO. The rate coefficients for the removal of C2(X 1Σ+g) and C2(a 3Πu) by O2 were determined both from laser induced fluorescence of C2(X 1Σ+g) and C2(a 3Πu), and from the time resolved chemiluminescence from excited CO molecules, and are both (3.0 ± 0.2)10?12 cm3 molec?1 s?1. The rate coefficient of the reaction of C3 with O2, which was determined using the IR MPD of allene as the source of C3 molecules, is <2 × 10?14 cm3 molec?1 s?1. In addition, we find that rate coefficients for C3 reactions with N2, NO, CH4, and C3H6 are all < × 10?14 cm3 molec?1 s?1. Excited CH molecules are produced in a reaction which proceeds with a rate coefficient of (2.6 ± 0.2)10?11 cm3 molec?1 s?1. Possible reactions which may be the source of these radicals are discussed. The reaction of CN with O2 produces NCO in vibrationally excited states. Radiative lifetime of the ā 2Σ state of NCo and the ā 1Πu(000) state of C3 are reported.  相似文献   

4.
The potential energy surfaces of N8 clusters were investigated by density functional theory (DFT) and a possible synthesis reaction pathway for N8 (CS) was suggested. The species involved were fully optimized up to the B3LYP/6‐311+G* level of theory. Relative energies were further calculated at the QCISD/6‐311+G*//B3LYP/6‐311+G* level. The reaction rate constants of these steps from the 1 (N5+?N3?, complex, CS) to 2 (N8, CS), 2 (N8, CS) to 3 (N8, CS), 3 (N8, CS) to 4 (N8, D2d), and 4 (N8, D2d) to 5 (N8, CS) reactions were predicted by the VTST theory. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1334–1339, 2001  相似文献   

5.
New cadmium(II) complexes with phosphine telluride ligands of the type CdX2(R3PTe)n [X?=?ClO4?, n?=?4: R?=?n-Bu (1), Me2?N (2), C5H10?N (3), C4H8?N (4) or OC4H8?N (5); X?=?Cl, n?=?2: R?=?n-Bu (6), Me2?N (7), C5H10?N (8), C4H8?N (9) or OC4H8?N (10)] have been synthesized and characterized by elemental analyses, IR and multinuclear (31P, 125Te, and 113Cd) NMR spectroscopy. In particular, the solution structures of these complexes were confirmed by 113Cd NMR at low temperature, which displays a quintuplet for each of the perchlorate complexes and a triplet for each of the chloride complexes due to coupling with four and two equivalent phosphorus atoms, respectively, indicating a four-coordinate tetrahedral geometry for the metal center. These multiplet features were further accompanied by one bond Te–Cd couplings, clearly showing that the ligand is coordinated to the metal through tellurium. The results are discussed and compared with those obtained for closely related phosphine chalcogenide analogs.  相似文献   

6.
Nitrogenase cofactors can be extracted into an organic solvent to catalyze the reduction of cyanide (CN?), carbon monoxide (CO), and carbon dioxide (CO2) without using adenosine triphosphate (ATP), when samarium(II) iodide (SmI2) and 2,6‐lutidinium triflate (Lut‐H) are employed as a reductant and a proton source, respectively. Driven by SmI2, the cofactors catalytically reduce CN? or CO to C1–C4 hydrocarbons, and CO2 to CO and C1–C3 hydrocarbons. The C? C coupling from CO2 indicates a unique Fischer–Tropsch‐like reaction with an atypical carbonaceous substrate, whereas the catalytic turnover of CN?, CO, and CO2 by isolated cofactors suggests the possibility to develop nitrogenase‐based electrocatalysts for the production of hydrocarbons from these carbon‐containing compounds.  相似文献   

7.
The proton transfer equilibrium reactions involving 3-penten-2-one, 3-methyl-3-buten-2-one, crotonic acid and methacrylic acid were carried out in an ion cyclotron resonance (ICR) spectrometer. The semiempirical method MNDO, used to estimate the heats of formation for 14 protonated [C5H9O]+ and [C4H7O2]+ ions and the energetic aspect of the fragmentations of metastable [C6H12O]+. and [C6H12O2]+. ions, leads to the conclusion that the ions corresponding to protonation at the carbonyl oxygen are the most stable. Thus the experimentally determined heats of formation of protonated olefinic carbonyl compounds can be attributed to the following structures: [CH3COHCHCHCH3]+ (δHf = 490 KJ mol?1), [CH3COHC(CH3)CH2]+ (δHf = 502 KJ mol?1), [HOCOHCHCHCH3]+ (δHf = 330 KJ mol?1) and [HOCOHC(CH3)CH2]+ (δHf = 336 KJ mol?1).  相似文献   

8.
Imidazole base was crystallized with different aromatic carboxylic acids 2,4-dihydroxybenzoic acid, 5-chlorosalicylic acid, and 1,8-naphthalic acid, affording three new binary molecular organic salts of [(C 3 H 5 N 2 + )·(C 7 H 5 O 4 )] (1), [(C 3 H 5 N 2 + )·(C 7 H 4 O 3 Cl )] C 7 H 5 O 3 Cl (2), and [(C 3 H 5 N 2 + ) (C 12 H 7 O 4 )] (3). Proton transfer occurs from the COOH of carboxylic acid to nitrogen of imidazole in all complexes (1-3), leading to the hydrogen bond N-H…O in all structures. To our knowledge, the recognition pattern between the carboxylic acid group and imidazole (acid-imidazole synthon) is less well-studied so far. The cooperation among COOH, COO and imidazolium cation functional groups for the observed hydrogen bond synthons is examined in the three structures. Generally, the strong N-H…O and O-H…O hydrogen bonds define supramolecular architecture and connectivity within chains, while weaker C-H…O hydrogen bonds play the dominant role in controlling the interactions between layers in these novel organic salts. Thermal stability of these compounds has been investigated by thermogravimetric analysis (TGA) of mass loss.  相似文献   

9.
Values for 〈ΔEdown〉, the average downward energy transferred from the reactant to the bath gas upon collision, have been obtained for highly vibrationally excited undeuterated and per-deuterated isopropyl bromide with the bath gases Ne, Xe, C2H4, and C2D4, at ca. 870 K. The technique of pressure-dependent very low-pressure pyrolysis (VLPP) was used to obtain the data. For C3H7Br, the 〈ΔEdown〉 values (cm?1) are 490 (Ne), 540 (Xe), 820 (C2H4), and 740 (C2D4), and for C3D7Br, 440 (Ne), 570 (Xe), 730 (C2H4), and 810 (C2D4). The uncertainties in these values are ca. ±10%. The 〈ΔEdown〉 values for the inert bath gases Ne and Xe show excellent agreement with the theoretical predictions of the semi-empirical biased random walk model for monatomic/substrate collisional energy exchange [J. Chem. Phys., 80 , 5501 (1984)]. The relative effects of deuteration of the reactant molecule on 〈ΔEdown〉 also compare favorably with the predictions of this theoretical model. Extrapolated high-pressure rate coefficients (s?1) for the thermal decomposition of reactant are 1013.6±0.3 exp(?200 ± 8 kJ mol?1/RT) for C3H7Br and 1013.9±0.3 exp(?207 ± 8 kJ mol±1/RT) for C3D7Br, which are consistent with previous studies and the expected isotope effect.  相似文献   

10.
The heat capacities of Ln(Me2dtc)3(C12H8N2) (Ln = La, Pr, Nd, Sm, Me2dtc = dimethyldithiocarbamate) have been measured by the adiabatic method within the temperature range 78–404 K. The temperature dependencies of the heat capacities, C p,m [La(Me2dtc)3(C12H8N2)] = 542.097 + 229.576 X ? 27.169 X 2 + 14.596 X 3 ? 7.135 X 4 (J K?1 mol?1), C p,m [Pr(Me2dtc)3(C12H8N2)] = 500.252 + 314.114 X ? 17.596 X 2 ? 0.131 X 3 + 16.627 X 4 (J K?1 mol?1), C p,m [Nd(Me2dtc)3(C12H8N2)] = 543.586 + 213.876 X ? 68.040 X 2 + 1.173 X 3 + 2.563 X 4 (J K?1 mol?1) and C p,m [Sm(Me2dtc)3(C12H8N2)] = 528.650 + 216.408 X ? 16.492 X 2 + 12.076 X 3 + 4.912 X 4 (J K?1 mol?1), were derived by the least-squares method from the experimental data. The heat capacities of Ce(Me2dtc)3(C12H8N2) and Pm(Me2dtc)3(C12H8N2) at 298.15 K were evaluated to be 617.99 and 610.09 J K?1 mol?1, respectively. Furthermore, the thermodynamic functions (entropy, enthalpy and Gibbs free energy) have been calculated using the obtained experimental heat capacity data.  相似文献   

11.
Liquid multi‐ion systems made by combining two or more salts can exhibit charge ordering and interactions not found in the parent salts, leading to new sets of properties. This is investigated herein by examining a liquid comprised of a single cation, 1‐ethyl‐3‐methylimidazolium ([C2mim]+), and two anions with different properties, acetate ([OAc]?) and bis(trifluoromethylsulfonyl)imide ([NTf2]?). NMR and IR spectroscopy indicate that the electrostatic interactions are quite different from those in either [C2mim][OAc] or [C2mim][NTf2]. This is attributed to the ability of [OAc]? to form complexes with the [C2mim]+ ions at greater than 1:1 stoichiometries by drawing [C2mim]+ ions away from the less basic [NTf2]? ions. Solubility studies with molecular solvents (ethyl acetate, water) and pharmaceuticals (ibuprofen, diphenhydramine) show nonlinear trends as a function of ion content, which suggests that solubility can be tuned through changes in the ionic compositions.  相似文献   

12.
The colorless complex anions triphenylcyanoborate ((C6H5)3CNB?), azide (N3?), and monothiophosphate (PO3S3?) have been determined in an acidic aqueous medium through colorimetric exchange on solid mercuric chloranilate surface. The released colored chloranilate ion absorbing at 530 nm responds linearly in the range 3–100 ppm for PO3S3? and N3? ions and in the range 8–200 ppm for (C6H5)3CNB? ion. The reaction is pH dependent and equilibration is achieved within an hour.  相似文献   

13.
Complex Chemistry of Polyfunctional Ligands. XXXIII. IR, FIR and Raman-Spectroscopic Studies on Metaltricarbonyl Derivatives of Tetradendate P- and As-Ligands in the Region 2000–150 cm?1 The IR- (2000–250 cm?1), FIR- (350–150cm?1) and RAMAN -spectra (2000–150 cm?1) of the tetradendate ligands C[CH2E(C6H5)2]4 (E = P, As) and of the complexes of the type cis-M(CO)3(R2ECH2)3C(CH2ER2) (M = Cr, Mo, W; E = P, As; R = C6H5) have been obtained. A comparison of the spectra of these compounds and consideration of previously reported data of analogous compounds allowed the assignment of all ligand vibrations. After localisation of the ligand vibrations an assignment of the v (CO) (A1 + E), δ (MCO) (A1 + 2E, v (MC) (A1 + E) and v (ME) (A1) modes was possible for the coordination polyhedra cis-M(CO)3)E3 (point group C3v). The v(ME) (E) modes were unobserved by its very low frequency.  相似文献   

14.
This article describes supramolecular interactions induced in a high molecular weight dithiocarbamate, padtc, by its design. Synthesis, spectral studies involving zinc, cadmium and mercury, padtc, and adducts with tmed, such as [Zn(padtc)2] (1), [Zn(padtc)2(tmed)]?·?C6H5CH3?·?0.5(H2O) (2), [Cd(padtc)2] (3), [Cd(padtc)2(tmed)]?·?C6H5CH3?·?0.36(H2O) (4), [Hg(padtc)2]?·?H2O (5), [Hg(padtc)2(2,2′-bipy)]?·?H2O (6), [Hg(padtc)2(1,10-phen)]?·?H2O (7), and [Hg(padtc)2(oxine)]?·?H2O (8) (where padtc??=?N,N′-(iminodiethylene)bisphthalimidedithiocarbamate, 1,10-phen?=?1,10-phenanthroline, tmed?=?tetramethylethylenediamine, 2,2′-bipy?=?2,2′-bipyridine, oxine?=?8-hydroxyquinoline) along with the single crystal X-ray structural analysis of [Zn(padtc)2(tmed)]?·?C6H5CH3?·?0.5(H2O) (2) and [Cd(padtc)2(tmed)]?·?C6H5CH3?·?0.36(H2O) (4) are reported. All the complexes were characterized by IR, NMR (1H and 13C), and thermogravimetric study. The IR spectra of the complexes show the contribution of the thioureide form to the structures. In 13C NMR spectra, the most important thioureide (N13CS2) carbon signals are observed at 210–212?ppm. Single crystal X-ray structural analyses of 2 and 4 show the presence of extensive supramolecular interactions stabilizing the solid-state structure. Both zinc and cadmium are in a distorted octahedral environment with MS4N2 chromophores. VBS of Zn and Cd are 1.76 and 1.98, respectively, supporting the correctness of the determined structure and the valence of the central metal ions.  相似文献   

15.
Tetraphenylbismuth(V) derivatives of the general formula Ph4BiX [X = OSO2C6H4Me-4, OC6H2(NO2)3-2,4,6, OC6H2(NO2-4)(Br2-2,6), OSO2C6H3(OH)(COOH)] react with methyl acrylate in the presence of palladium dichloride (1:3:0.04 molar ratio) in acetonitrile at 20°C to form the cross-coupling products, methyl cinnamate (0.17–0.54 mol mol?1 starting bismuth compound) and methylhydrocinnamate (0.10–0.73 mol mol?1), diphenyl (0.06–0.80 mol mol?1), and benzene (0.02–0.36 mol mol?1). The highest C-phenylating activity is shown by Ph4BiOSO2C6H4Me-4. The mechanisms with the palladium-catalyzed cross-coupling reactions are suggested.  相似文献   

16.
Bare FeO+ reacts in the gas phase with benzene at collision rate (k = 1.3 × 10?9 cm3 molecule?1 s?1), giving rise to the formation of Fe(C6H4)+/H2O(5%), Fe(C5H6)+/CO(37%), Fe(C5H5)+/CO/H. (2%), and Fe+/C6H5OH (56%). Neither the reaction rate nor the product distribution are subject to a significant kinetic isotope effect, thus, ruling out several mechanistic variants described in the literature to the operative for ‘analogous’ arene oxidation processes in solution. A mechanism is suggested which is in keeping with the experimental findings, and which also accounts for some remarkable results obtained, when two [Fe, C6,H6H6O]+ isomers are generated and subjected to a neutralization-re-ionization experiment in the gas phase.  相似文献   

17.
The synthesis of the half-sandwich compound Na[(C5H5)Ni{P(S)(CH3)2}2] is described. The anions [(C5H5)Ni{P(S)R2}2]?, 1a (R = OCH3) and 1b (R = CH3) react as bidentate sulfur ligands with [Ni2(C5H5)3]+, giving nickelocene and weakly paramagnetic dinuclear complexes of the type [(C5H5)Ni{P(S)R2}2Ni(C5H5)] (2a,b). In these compounds, the P(S)R2 units form NiPSNi bridges in such a fashion as to generate a (C5H5)NiP2 and a (C5H5)NiS2 unit. A temperature-dependent singlettriplet spin equilibrium is observed, which is essentially localized on the (C5H5)NiS2 side. Accordingly, the position of the cyclopentadienyl peak of the (C5H5)Ni unit bound to the two sulfur donor centers displays a very large temperature dependence in the 1H NMR spectra. MO model calculations (EHT) for P(S)H2?, [(C5H5)Ni{P(S)H2}2]? (1c), [(C5H5)Ni{P(S)H2}2Ni(C5H5)] (2c) and its isomer 3c allow the observed spin crossover to be explained as a consequence of the pronounced π-donor properties of the sulfur centers and allow predictions for related complexes.The green complexes 2a,b isomerize completely and irreversibly in a first-order reaction to yield the diamagnetic red compounds [{(C5H5)NiP(S)R2}2] (3a,b), in which each (C5H5)Ni unit is coordinated to one P and one S donor atom. The rate constant of isomerization of 2a, k (7.6 ± 0.3) × 10?4s?1 at 306 K, and the energy of activation, Ea 76 kJ mol?1, have been determined. The rate of isomerization is independent of the solvent, and crossover experiments verify that the isomerization is an intramolecular process without involvement of the monomeric units [(C5H5)NiP(S)R2].  相似文献   

18.
Three kinds of trinuclear metal string complexes, [Ni3(dpa)4(L1)2]?·?H2O?·?C2H5OH (L1?=?(E)-3-(2-hydroxyl-phenyl)-acrylic acid) (1), [Ni3(dpa)4(L2)2]?·?2C2H5OC2H5 (L2?=?(E)-3-(3-hydroxyl-phenyl)-acrylic acid) (2) and [Ni3(dpa)4(L3)2]?·?3CH2Cl2?·?1.5CH3OH (L3?=?(E)-3-(4-hydroxyl-phenyl)-acrylic acid) (3). (dpa??=?bis(2-pyridyl)amido), have been synthesized. The structures of 1 and 2 have been analyzed by the X-ray single-crystal diffraction showing hydrogen-bonded networks.  相似文献   

19.
The silver nanoparticles doped poly-glycine composite membrane was prepared by cyclic voltammetry on the surface of the glassy carbon electrode (GCE). The morphology and electrochemical properties were characterized by scanning electron microscopy and cyclic voltammetry, respectively, and in detail, the electrochemical behaviors of the norepinephrine (NE) on this membrane were studied. The results showed that the membrane had good catalytic properties for the oxidative–reductive reaction of NE. NE had a couple of sensitive oxidative-reductive current peaks. The reductive peak currents were linearly with its concentration in the range of 1.90?×?10?7 to 7.00?×?10?6 and 7.00?×?10?6 to 1.00?×?10?4?mol l?1, and the linear regressive equations were i pc (A)?=?3.73?×?10?6?+?0.70C (mol l?1), i pc (A)?=?9.83?×?10?5?+?0.12C (mol l?1), respectively, with the relate coefficient (r) of 0.9926 and 0.9944. The detection limit was 1.2?×?10?7?mol l?1 (S/N?=?3), which could be used to determine the content of NE and at the same time, eliminate the interference of the ascorbic acid (AA). The proposed method had high sensitivity, good selectivity and stability.  相似文献   

20.
The effect of the addition of 2-methoxyethanol on the critical micelle concentration (cmc) and on the degree of counterion dissociation (??) of butanediyl-1,4-bis(tetradecyldimethylammonium bromide) gemini surfactant, [C14H29N+(CH3)2?C(CH2)4?CN+(CH3)2C14H29,2Br?] (referred as 14?C4?C14,2Br?), has been studied by varying the compositions of the 2-methoxyethanol + water mixed solvent media (0 to 50?%). To determine various thermodynamic parameters of micellization, on the basis of the mass?Caction model for micelle formation, the experiments were performed at selected compositions of the mixed solvent at four temperatures ranging between 25?°C and 50?°C. Furthermore, the air/bulk surface tensions of the pure and mixed media were determined, and a successful attempt was made to correlate the cohesive energy density described through the Gordon parameter with the values of Gibbs energy of micellization.  相似文献   

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