共查询到20条相似文献,搜索用时 46 毫秒
1.
Nobuyuki Tanaka 《Journal of Thermal Analysis and Calorimetry》1996,46(3-4):1021-1031
The instantaneous elastic moduli for a nylon-6 monofilament were derived on strain recoveries right after creep, stress relaxation, and rapid elongation,E
c
,E
s
andE
e
, respectively. It was found that during strain recoveryE
s
(>E
e
) andE
e increase monotonically with increasing load,m
1, on the sample. The extrapolated value of Es atm
1=0 g is almost equal to Young's modulus, 4.06 GPa. The value ofE
c also increased with increasingm
1, and atm
1=600 g (1.93 t cm–2) reached about 14 GPa. The endothermic heat change right after creep, stress relaxation or rapid elongation,Q, was negligibly small. For comparison,E
s
,E
c
andQ were also investigated for silicone rubber. It was found thatE
s (53.8 M Pa at the draw ratioD=1.2) decreased abruptly atD=1.3. In the range ofD=1.4–1.9,E
s was only 22.6 MPa. In the case of stress relaxation,Q increased with increasingD from 4 J mol–1 (atD=1.2) to 56 J mol–1 (atD=1.9). FurthermoreE
c (5.58 MPa atm
1=133.8 g (429.4 kg cm–2)) increased gradually with increasing m1 and attained 16.6 MPa atm
1=548.4 g (1.76 t cm–2). In the case of creep,Q was in the range of 0–11.5 J mol–1 and larger when larger loads,m
2 were removed during the later stages of creep.Dedicated to Professor Bernhard Wunderlich on the occasion of his 65th birthdayThe author wishes to thank Mr. Keizi Igarashi and Mr. Tetsuya Yasui for helping in the experiments. 相似文献
2.
Ligand-field spectra of tetrahedral CoX
4
2–
and octahedral Cr(NCS)
6
3–
were measured in a number of solvents. Care was taken to ensure complete formation of the anionic species to be investigated. Considerable variations in intensity were found for complexes with highly polarizable ligands. For Co(NCS)
4
2–
the oscillator strength of the4T1(P) transition in aqueous solution was only about 1/5 that in a number of organic solvents, with little variation in these solvents. For Cr(NCS)
6
3–
the intensities are highest in aqueous solution, and some variation is observed for the nonaqueous solvents. These data for the chromium complex correlate at least qualitatively with variations of the excited state lifetimes in these solvents. Nonlinear changes of intensities in solvent mixtures can be taken as an indication of preferential solvation of the anionic complex by nonaqueous solvent molecules. The reported results are a strong indication of large differences in solvent/solute interactions between water and the nonaqueous solvents. 相似文献
3.
Dr. E. Schollmeyer Dipl.-Chem. M. Sodnik Prof. Dr. H. Herlinger 《Colloid and polymer science》1976,254(11):951-956
Zusammenfassung Wählt man zur Beschreibung einfacher färberischer Systeme die Thermodynamik der irreversiblen Prozesse, so erhält man Gleichungen für den Diffusionsprozeß. Man hat es in diesem vereinfachten Modell mit drei unabhängigen Diffusionskoeffizienten zu tun, wobei einer davon den SelbstdiffusionskoeffizientenD von Wasser im Substrat beschreibt. Durch experimentelle Untersuchungen mittels Tracer-Technik wurdeD bei verschiedenen Polymeren in der Größenordnung von 4 · 10–10 cm2 · sec–1 bestimmt. Dieser Befund wird durch eine parakristalline Wasserstruktur im Polymer interpretiert. Die scheinbaren AktivierungsenergienE
a
für diesen Diffusionsprozeß liegen mit ca. 6 kcal · Mol–1 etwas höher als im Wasser (4,2 kcal · Mol–1) und sprechen dafür, daß wegen der Kleinheit des diffundierenden Teilchens die Bewegung der Kettensegmente des Polymers nicht inE
a
enthalten ist.
Mit 3 Abbildungen und 1 Tabelle 相似文献
Summary If the thermodynamics of irreversible processes is used to describe simple dyeing systems, equations for the diffusion process are obtained. This simplified model contunius three independent diffusion coefficients, one. of them describing the self-diffusion coefficientD of water in the substrate. By means of experimental investigations using tracer technics for diverse polymersD was found to be about 4 · 10–10 cm2 · sec 1. This result is interpreted by means of a paracrystalline structure of the water in the polymer. The apparent activation energiesE a of this diffusion process, being about 6 kcal · Mol–1, are a little greater than in water (4,2 kcal · Mol–1), indicating that the movement of the chain-segments of the polymer is not contained inE a , because of the smallness of the diffusing particles.
Mit 3 Abbildungen und 1 Tabelle 相似文献
4.
Résumé Les paramètres D et E de molécules dans l'état triplet sont calculés par double perturbation au premier ordre par rapport à l'hamiltonien de corrélation de P. S. Epstein, et à l'hamiltonien d'interaction dipolaire spin-spin. On montre que les seules configurations diexcitées triplets fournissant une contribution non nulle sont celles où les orbitales occupées par un seul électron dans le plus bas triplet deviennent vides ou doublement occupées. On trouve ainsi pour le naphtalène D= 0,090 cm–1, E=–0,014 cm–1 (exp = D=0,100 cm–1, E=–0,014 cm–1). La polarisation de spin seule donne D=0,113 cm–1, E= –0,027 cm–1. La contribution du 2ème ordre par rapport à la perturbation due à la corrélation est évaluée à 10% de D total.
Travail effectué dans les cadres de la Convention N-67-34217-00-480-75-01 de la Direction des Recherches et Moyens d'Essais (Responsable: Prof. B. Pullman). 相似文献
Calculation of the dipolar spin-spin interaction by double perturbation theory in moleculesApplication to the triplet states of hydrocarbons
A double perturbation calculation of D and E parameters of molecular triplet states is performed in first order with respect both to correlation (as defined by P. S. Epstein) and dipolar spin-spin interaction. A non zero contribution is obtained from diexcited triplet configurations only if the singly occupied orbitals of the lowest triplet configuration become either empty or doubly occupied. Results are for Naphtalene: D=0.090 cm–1, E=–0.014 cm–1 (exp: D=0.100 cm–1, E=–0.014 cm–1). Spin polarization alone yields D=0.113 cm–1, E=–0.027 cm–1. The correlation second order contribution for D is estimated to 10% of the over-all value.
Zusammenfassung Es wird eine Berechnung des D- und E-Parameters molekularer Triplettzustände im Rahmen einer zweifachen Störungsrechnung bis zur ersten Ordnung durchgeführt, und zwar sowohl in bezug auf die Korrelation (wie definiert von P. S. Epstein) als auch die dipolare Spin-Spin-Wechselwirkung. Der Beitrag zweifach angeregter Triplettkonfigurationen ist nur dann von Null verschieden, wenn die beiden in der Grundkonfiguration einfach besetzten Orbitale entweder gar nicht oder doppelt besetzt sind. Die Ergebnisse für Naphthalin sind: D=0,090 cm–1, E=–0,014 cm–1 (exp.: D=0,100 cm–1, E=–0,014 cm–1), während die Spinpolarisation allein D=0,113 cm–1, E=–0,027 cm–1 liefert. Der Beitrag der Korrelation zu D in zweiter Ordnung wird auf 10% des Gesamtwertes geschätzt.
Travail effectué dans les cadres de la Convention N-67-34217-00-480-75-01 de la Direction des Recherches et Moyens d'Essais (Responsable: Prof. B. Pullman). 相似文献
5.
The title Schiff base ligand, H2L, and its complex [CuL] have been prepared and characterized by elemental analysis and i.r. spectroscopy. The electrochemical properties of the single crystal [CuL]·0.5C2H4Cl2 have been investigated by cyclic voltammetry (c.v.). Upon scanning at negative and positive potentials, two reduction and two oxidation waves were observed at E
1/2
0 = –0.47 and –0.77 V and E
1/2
0 = 1.10 and 1.39 V, respectively. Two K
com values for the reduction and oxidation process are 1.2×105 and 8.0×104, respectively, and indicate that the deprotonated ligand, L, has the ability to stabilize the mixed valent states of both CuIICuI and CuIICuIII. The crystal structure has been solved by X-ray diffraction, with a final R = 0.0653. Wound around a copper atom, the effectively tetradentate chain ligand, L, coordinates only via its two imino and two phenolate groups at both ends of the chain. The geometry, D
2d symmetry, is best described as trans 'N2O2' square-planar with slight tetrahedral distortion. The reason, why the mononuclear [CuL] unit can display two c.v. waves in each process, has been explained on the basis of configuration interchange between mono- and dinuclear units in c.v. electrolyte solution. 相似文献
6.
Yuichiro Tada Masakatsu Ueno Noriaki Tsuchihashi Kiyoshi Shimizu 《Journal of solution chemistry》1994,23(9):973-987
The limiting molar conductances ° of potassium deuteroxide KOD in D2O and potassium hydroxide KOH in H2O were determined at 5 and 45°C as a function of pressure to clarify the difference in the temperature, pressure and isotope effects on the proton jump between an OD– (OH–) and a D3O+ (H3O+) ion. The excess conductances of the OD– ion in D2O and the OH– ion in H2O,
E
0
(OD-) and
E
0
(OH-), increase with increasing temperature and pressure as in the case of the excess deuteron and proton conductances,
E
0
(D+) and
E
0
(H+). However, the temperature effect on the excess conductance is larger for the OD–(OH–) ion than for the D3O+ (H3O+) ion but the pressure effect is much smaller for the OD– (OH–) ion than for the D3O+ (H3O+) ion. These findings are correlated with larger activation energies and less negative activation volumes found for the OD– (OH–) ion than for the D3O+ (H3O+) ion. Concerning the isotope effect, the value of
E
0
(OH-)/
E
0
(OD-) deviates considerably from
at each temperature and pressure in contrast with that of
E
0
(H+)/
E
0
(D+), although both of them decrease with increasing temperature and pressure. These results are discussed mainly in terms of the difference in repulsive force between the OD– (OH–) or the D3O+ (H3O+) ion and the adjacent water molecule, the difference in strength of hydrogen bonds in D2O and H2O, and their variations with temperature, pressure, and isotope. 相似文献
7.
U. Berzinsh M. Gustafsson J. Persson 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1993,27(2):155-158
The hyperfine structure (hfs) of181Ta has been investigated using laser radio-frequency double resonance and high resolution laser spectroscopy on collimated atomic beams. The magnetic dipole and electric quadrupole hyperfine structure coupling constants of the 5d
4
6
s 6D
3/2, 5/2, 7/2, 9/2 metastable states have been determined using radio-frequency spectroscopy. In the 5d
4 6s
6
D
1/2 metastable state and the excited 5d
3 6s 6p
4
D
3/2,6
D
5/2, 9/2 as well as the unidentified 28 182.6 cm–1 and 30 021.2 cm–1 states, hfs constants have been obtained from high resolution laser spectroscopy. A radio-frequency converter has been developed in order to reach the frequency region 2.7–10 GHz. 相似文献
8.
The heats of solution of the sodium n-alkyl sulfonates from methyl to octyl have been measured at 25°C in water, D2O, and three alcohol-rich mixtures with water, all at solute concentrations low enough so that solute-solute interaction is negligible. Methylene-group contributions to the enthalpies of transfer are readily identified. Collation with the results of earlier studies of enthalpies of transfer leads to the conclusion that methylene-group enthalpies of transfer can be identified as follows: 0.87 kcal-mole–1 for transfers to the gas phase from water and –0.035 kcal-mole–1 for transfers to D2O from H2O, independent of the solute type provided only that methylene-group contributions can be identified in the data. Compared to other solvents, water is about as lipophilic as dimethylsulfoxide or a mixture of 27 moles of water with 73 moles of methanol. However, the range of the interactions between different groups on a given solute molecule seems to be much greater in water than in any of the other solvents studied, making it more difficult to identify group contributions to solvation in water. Another example of the complexity of the solvation of alkyl groups in water is encountered when one compares the solvation enthalpy of hexane in various solvents with some of the above results. 相似文献
9.
Malcolm E. Tessensohn Melvyn Lee Prof. Dr. Hajime Hirao Prof. Dr. Richard D. Webster 《Chemphyschem》2015,16(1):160-168
Voltammetric experiments with 9,10‐anthraquinone and 1,4‐benzoquinone performed under controlled moisture conditions indicate that the hydrogen‐bond strengths of alcohols in aprotic organic solvents can be differentiated by the electrochemical parameter ΔEpred=|Epred(1)?Epred(2)|, which is the potential separation between the two one‐electron reduction processes. This electrochemical parameter is inversely related to the strength of the interactions and can be used to differentiate between primary, secondary, tertiary alcohols, and even diols, as it is sensitive to both their steric and electronic properties. The results are highly reproducible across two solvents with substantially different hydrogen‐bonding properties (CH3CN and CH2Cl2) and are supported by density functional theory calculations. This indicates that the numerous solvent–alcohol interactions are less significant than the quinone–alcohol hydrogen‐bonding interactions. The utility of ΔEpred was illustrated by comparisons between 1) 3,3,3‐trifluoro‐n‐propanol and 1,3‐difluoroisopropanol and 2) ethylene glycol and 2,2,2‐trifluoroethanol. 相似文献
10.
Half-wave potentials of the one-electron electrochemical oxidation (E
1/2
ox) of hydroquinolines with different degrees of heterocycle hydrogenization as well as containing substituents of various natures in the benzene ring and heterocycle have been measured. Linear correlations betweenE
1/2
ox and the values of the Hammett polar -constants form- andp-substituents in dihydroquinolines and related sulfur-containing dithiolthiones were established. The character of the variation ofE
1/2
ox in the series of hydroquinolines was found to correlate with the characteristic features of the inhibiting action of these compounds in the liquid-phase oxidation of various hydrocarbons. However, in contrast to phenolic antioxidants for hydroquinolines, there is no dependence of the retardation period onE
1/2
oxin the oxidation of hydrocarbons at temperatures higher than 100 °C.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 610–613, April, 1994. 相似文献
11.
A hollow cathode arc discharge in hydrogen has been used for the purpose of chromium oxide reduction, the solid oxide being placed inside the anode. Mass transport from the oxide to the gas phase and excitation conditions in the plasma have been investigated. The results show that a substantial amount of oxide is transferred to the gas phase with subsequent reduction and deposition inside the cathode cavity, in the form of a pure metal. The residual part condenses on the discharge chamber wall as an amorphous substance, containing 50–60% of Cr metal, and on the anode surface under the form of a mixture of chromium oxide and metal crystals (10%). From spectroscopic investigations it follows that, inside the anode zone, total Cr concentration in the gas phase is of the order of 1014 cm–3, the excitation temperature of the atoms and ions being 4500 and 5500 K, respectively, and the ionization temperature being about 6000 K.Notation
I
absolute spectral line intensity (W cm–2 sr–1)
-
emission coefficient (W cm–3 sr–1)
-
A
relative absorption
-
absorption coefficient (cm–1)
-
L
plasma diameter (mm)
-
f
tk
oscillator strength
-
D
full Doppler width (cm–1)
-
S(
0
L)
Ladenburg-Levy function
-
wave number (cm–1)
-
k
pl
mass transport rate (mol cm–2 s–1)
-
k
th
thermal reduction rate (mol cm–2 s–1)
-
u
ion mobility (mm V–1 s–1 )
-
E
electric field strength (V mm–1)
-
drift velocity (cm s–1) 相似文献
12.
Summary Computer-aidedKnudsen cell mass spectrometry is used for thermodynamic investigations on liquid ternary Fe1–x(Ni5/6Cr1/6)x alloys. The thermodynamic excess properties have been determined by means of the Digital Intensity-Ratio (DIR) method. Liquid ternary Fe1–x(Ni5/6Cr1/6)x alloys are characterized by exothermic molar heats of mixingH
E, negative molar excessGibbs energiesG
E, and negative molar excess entropiesS
E. At 1850 K, the minimumH
E value is –3120 J/mol (42.3 at.% Fe), the minimumG
E value is –2540 J/mol (30 at.% Fe), and the minimumS
E value is –0.44 J/(mol K) (60 at.% Fe). At 1850 K, the thermodynamic activities of Fe show slight negative deviations from the ideal behaviour for alloys with a Fe-content of less than 75 at.%, and ideal behaviour for the Fe-rich alloys (x
Fe>0.75).
Thermodynamische Parameter flüssiger ternärer Fe1–x(Ni5/6Cr1/6)x-Legierungen
Zusammenfassung Die Thermodynamik flüssiger ternärer Fe1–x(Ni5/6Cr1/6)x-Legierungen wurde mit Hilfe der computerunterstützten Knudsenzellen-Massenspektrometrie studiert. Die thermodynamische Auswertung der experimentellen Untersuchungen erfolgte nach der digitalen Intensitätsverhältnismethode (DIR). Flüssige ternäre Fe1–x(Ni5/6Cr1/6)x-Legierungen zeigen exotherme molare MischungswärmenH E, negative molareGibbssche ZusatzenergienG E, und negative molare ZusatzentropienS E. Bei 1850 K sind die Minimumswerte fürH E –3120 J/mol (42.3 At.% Fe), fürG E –2540 J/mol (30 At.% Fe) und fürS E –0.44 J/(mol K) (60 At.% Fe). Bei 1850 K zeigen die thermodynamischen Aktivitäten von Fe bei Legierungen mit einem Fe-Gehalt von höchstens 75 At.% leichte negative Abweichungen vom idealen Verhalten, die Fe-reichsten Legierungen (x Fe>0.75) verhalten sich hingegen nahezu ideal.相似文献
13.
Self-diffusion of Co2+ ions in CoBr2 and CoI2 is reported in the concentration range of 10–5 to 0.25M in 1% agar gel at 25 °C. The deviations observed between the experimental and theoretical values of diffusion coefficients are explained by considering different types of interactions occurring in the ion-gel water system. The applicability of the transition state theory to the diffusion of ZnSO4 in agar gel medium is tested by varying the temperature as well as the gel concentration at high concentration of the electrolyte. The activation energy E and D
0 value decrease with increasing gel concentration in agreement with the theory. 相似文献
14.
Summary The displacement of chloride ligands from -cis-chloro-aquoethylenediamine-N,N-diacetatocobalt(III) in nonacidic aqueous solutions was followed conductimetrically at 30–45° and the products of aquation were characterised by conductance, spectral and ion-exchange techniques. The rate constants for aquation in aqueous media and in 1 : 4 v : v mixed solvents at 25° are: 4.0 × 10–5 s–1 in H2O, 2.71 × 10–5 s–1 in MeOH : H2O, 2.74 × 10–5 s–1 in EtOH: H2,O and 2.58 × 10–5 s–1 n in Me2CO : H2O. The corresponding H* and S* values have also been evaluated. Solvent polarity has a marked influence on the rate of chloride ion release. The aquation rate constants and the activation parameters have been correlated with solvent parameters,e.g. D, Y-values, Dimroth's ET and Kosower's Z-values and, based on these correlations, a dissociative interchange (Id) mechanism is proposed rather than dissociative as observed for some other cobalt(III) complexes.Senior author. 相似文献
15.
Zusammenfassung Eine polarographische Methode zur Bestimmung der 2,2-Dicinchoninsäure in 15%iger Ammoniumacetatlösung als Grundelektrolyt wurde ausgearbeitet. Der zweistufigen Reduktion entsprechen zwei polarographische Stufen, deren Halbstufenpotentiale gegen die gesättigte KalomelelektrodeE
1/2=–0,74 V undE
1/2=–1,28 V betragen.Die charakteristischen zwei Maxima wurden mit 0,5%iger Gelatinelösung beseitigt und der Sauerstoff mit elektrolytisch hergestelltem Wasserstoff entfernt.Die lineare Abhängigkeit des Diffusionsstromes für beide Stromstufen der Säure in zwei Konzentrationsbereichen —von 1·10–4- bis 3·10–4-m und von 0,5·10–3-bis 3·10–3-m —wurde festgestellt.
Summary A polarographic method has been developed for the determination of 2,2-dicinchonic acid in 15% ammonium acetate solution as fundamental electrolyte. The two-stage reduction is shown by two polarographic stages, whose half-stage potentials as referred to the saturated calomel electrode amount toE 1/2=–0.74 V andE 1/2=–1.28 V.The two characteristic maxima were removed by 0.05% gelatin solution and the oxygen was eliminated by means of hydrogen produced electrolytically. The linear dependence of the diffusion current for both current stages of the acid were established in two concentration ranges —from 1·10–4 to 3·10–4 M and from 0.5·10–3 to 3·10–3 M.
Résumé Mise au point d'une méthode polarographique pour doser l'acide dicinchonine-2, 2 en solution dans l'acétate d'ammonium à 15% comme électrolyte support. La réduction en deux temps correspond à deux vagues polarographiques, dont les potentiels de demi-vague par rapport à l'électrode au calomel saturée s'élèvent àE 1/2= – 0,74 V etE 1/2=–1,28 V.On élimine les deux maximums caractéristiques par une solution de gélatine à 0,05% et l'oxygène par l'hydrogène préparé électrolytiquement. Mise en évidence d'un rapport linéaire entre le courant de diffusion pour les deux vagues de courant de l'acide dans les deux domaines de concentration: de 1·10–4 à 3·10–4 M et de 0,5·10–3 à 3·10–3 M.相似文献
16.
Results of studying the spectral and luminescent properties of Eu3+ ions upon homogeneous excitation of POCl3–SnCl4–-UO2+
2–Eu3+ and D2O–235UO2+
2–Eu3+ solutions by -particles are presented. It was found that the radioluminescence intensity of Eu3+ ions in both solvents increases proportionally to the energy input by -particles. The yield of radioluminescence photons from europium ions in the POCl3–SnCl4–UO2+
2–Eu3+ solutions is more than nine times as high as that in D2O–UO2+
2–Eu3+. The radiation-chemical yields of excited 5
D
0 states of Eu3+ ions are 0.74 ± 0.07 and 0.18 ± 0.02 ions/100 eV in POCl3–SnCl4–UO2+
2–Eu3+ and D2O–UO2+
2–Eu3+ solutions, respectively. 相似文献
17.
Joseph C. P. Koo Janice S. W. Lam Gregory A. Chass Ladislaus L. Torday Andras Varro Julius Gy. Papp 《Journal of Molecular Structure》2003,620(2-3):231-255
The sidechain conformational potential energy hypersurfaces (PEHS) for the γL, βL, αL, and αD backbone conformations of N-acetyl-
-aspartate-N′-methylamide were generated. Of the 81 possible conformers initially expected for the aspartate residue, only seven were found after geometric optimizations at the B3LYP/6-31G(d) level of theory. No stable conformers could be located in the δL, L, γD, δD, and D backbone conformations. The ‘adiabatic’ deprotonation energies for the endo and exo forms of N-acetyl-
-aspartic acid-N′-methylamide were calculated by comparing their optimized relative energies against those found for the seven stable conformers of N-acetyl-
-aspartate-N′-methylamide. Sidechain conformational PEHSs were also generated for the estimation of ‘vertical’ deprotonation energies for both endo and exo forms of N-acetyl-
-aspartic acid-N′-methylamide. All backbone–sidechain (N–H−O–C) and backbone–backbone (N–HO=C) hydrogen bond interactions were analyzed. A total of two backbone–backbone and four backbone–sidechain interactions were found for N-acetyl-
-aspartate-N′-methylamide. The deprotonated sidechain of N-acetyl-
-aspartate-N′-methylamide may allow the aspartyl residue to form strong hydrogen bond interactions (since it is negatively charged) which may be significant in such processes as protein–ligand recognition and ligand binding. As a primary example, the molecular geometry of the aspartyl residue may be important in peptide folding, such as that in the RGD tripeptide. 相似文献
18.
Dr. Sergei V. Chapyshev Dr. Denis V. Korchagin Dr. Mikhail F. Budyka Dr. Tatiana N. Gavrishova Dr. Patrik Neuhaus Prof. Dr. Wolfram Sander 《Chemphyschem》2012,13(11):2721-2728
The UV (λ>305 nm) photolysis of triazide 3 in 2‐methyl‐tetrahydrofuran glass at 7 K selectively produces triplet mononitrene 4 (g=2.003, DT=0.92 cm?1, ET=0 cm?1), quintet dinitrene 6 (g=2.003, DQ=0.204 cm?1, EQ=0.035 cm?1), and septet trinitrene 8 (g=2.003, DS=?0.0904 cm?1, ES=?0.0102 cm?1). After 45 min of irradiation, the major products are dinitrene 6 and trinitrene 8 in a ratio of ~1:2, respectively. These nitrenes are formed as mixtures of rotational isomers each of which has slightly different magnetic parameters D and E. The best agreement between the line‐shape spectral simulations and the experimental electron paramagnetic resonance (EPR) spectrum is obtained with the line‐broadening parameters Γ(EQ)=180 MHz for dinitrene 6 and Γ(ES)=330 MHz for trinitrene 8 . According to these line‐broadening parameters, the variations of the angles Θ in rotational isomers of 6 and 8 are expected to be about ±1 and ±3°, respectively. Theoretical estimations of the magnetic parameters obtained from PBE/DZ(COSMO)//UB3LYP/6‐311+G(d,p) calculations overestimate the E and D values by 1 and 8 %, respectively. Despite the large distances between the nitrene units and the extended π systems, the zero field splitting (zfs) parameters D are found to be close to those in quintet dinitrenes and septet trinitrenes, where the nitrene centers are attached to the same aryl ring. The large D values of branched septet nitrenes are due to strong negative one‐center spin–spin interactions in combination with weak positive two‐center spin–spin interactions, as predicted by theoretical considerations. 相似文献
19.
The direct electrochemical reduction of hemin, protoporphyrin(IX) iron(III) chloride, ligated with strong or weak heterocyclic bases, was investigated in the ionic liquids (IL), 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) and 1-octyl-3-methylimidazolium hexafluorophosphate ([omim][PF6]), using cyclic voltammetry and chronocoulometry. Hemin complexed with N-methylimidazole (NMI) or with pyridine had E1/2 values slightly (4–59 mV) more positive in IL (without electrolyte) than in methanol (1.0 M electrolyte) using a gold electrode. NMI-ligated hemin had a lower E1/2 than pyridine-ligated hemin in either IL, consistent with the stronger electron donor characteristic of NMI. [Bmim][PF6] solutions consistently yielded E1/2 values 30 mV more negative than [omim][PF6] solutions. The diffusion coefficients Do of hemin in the IL ranged between 1.50 and 2.80×10−7 cm2 s−1, while the heterogeneous electron-transfer rate constants ks ranged between 3.7 and 14.3×10−3 cm s−1. Cyclic voltammetry of hemin adsorbed to a gold surface through 4,4′-bispyridyl disulfide (AT4) linkages showed a large positive shift in the oxidation wave, indicating that adsorption stabilizes the reduced hemin state. The surface concentration Γo of the adsorbed hemin was determined to be 1.21×10−10 mol cm−2, indicating the presence of one or more complete monolayers of hemin. These findings suggest that while hemin is electrochemically active in IL, its behavior is modified by the ligand field strength and surface adsorption phenomena. 相似文献
20.
We have performed ab initio fourth-order Møller–Plesset perturbation theory calculations in the framework of the supermolecule approach on the vertical excitation spectra of the weakly bound van der Waals N2–He dimer. They indicate a ``T-shaped' stablest ground N2(X1g+)–He(1S) electronic state with a well depth, De, of 21.63 cm–1 at a minimum distance, Re, of 3.44 Å and zero-point vibration correction, Do, of 7.07 cm–1. They also indicate a ``T-shaped' stablest excited conformer with Re=3.25 Å, De=36.85 cm–1 and Do=17.06 cm–1 for the N2(B3g)–He(1S) triplet electronic level. In order to investigate the use of less-demanding correlation methods, test density functional theory calculations using the mPW1PW exchange–correlation functional are also presented for comparison. 相似文献