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1.
The first vertical electron affinities EA of 13 series of molecules and free radicals D(X i ) n are related to the inductive (σ I ), resonance (σ R ? ), and polarization (σα) parameters of substituents X i by the dependences EA = EA H + aΣσ I + bΣσ R/? + cΣσα: In radical anions D(X i ) n , compared to radical cations D(X i ) n , the polarization interaction is weaker or similar in magnitude but has an opposite sign. The previously unknown resonance parameters σ R ? of substituents SiMe3 and CH2SiMe3 bound to the radical anion center H2C=CH were calculated.  相似文献   

2.
LRM (Low Rank Modification) is a mathematical method that produces eigenvalues and eigenstates of generalized eigenvalue equations. It is similar to the perturbation expansion in that it assumes the knowledge of the eigenvalues and eigenstates of some related (unperturbed) system. However, unlike perturbation expansion, LRM produces correct results however large the modification of the original system. LRM of finite-dimensional systems is here generalized to the combined (external and internal) modifications. Parent n-dimensional system A n containing n eigenvalues λ i and n eigenstates \({| {\Phi_i}\rangle}\) is described by the generalized n × n eigenvalue equation. In an external modification system A n interacts with another ρ-dimensional system B ρ which is situated outside the system A n . In an internal modification relatively small σ-dimensional subsystem of the parent system A n is modified. Modified system C n+ρ that contains external as well as internal modifications is described by the generalized (n + ρ) × (n + ρ) eigenvalue equation. This system has (n + ρ) eigenvalues \({\varepsilon_s}\) and (n + ρ) corresponding eigenstates \({| {\Psi_s}\rangle}\) . In LRM this generalized (ρn) × (ρn) eigenvalue equation is replaced with a (nonlinear) (ρ + σ) × (ρ + σ) equation which produces all eigenvalues \({\varepsilon_s \notin \left\{ {\lambda_i}\right\}}\) and all the corresponding eigenstates \({| {\Psi_s}\rangle }\) of C n + ρ. Another equation produces remaining solutions (if any) that satisfy \({\varepsilon_s \in \left\{ {\lambda_i}\right\}}\) . Those two equations produce exact solution of the modified system C n + ρ. If (ρσ) is small with respect to n, this approach is numerically much more efficient than a standard diagonalization of the original generalized eigenvalue equation. Unlike perturbation expansion, LRM produces exact results, however large modification of the parent system A n .  相似文献   

3.
By alkylation of 3,6-dihydrooxyphthalonitrile with 1-bromodecane and by reaction of 4,5-diaminophthalodinitrile with acetic acid were synthesized respectively 3,6-didecyloxyphthalonitrile (A) and 2-methyl-5,6-dicyanobenzimidazole (B). The random condensation of the dinitriles obtained provided unsymmetrical phthalocyanines of A 3 B, AABB, and AB 3 type. Their spectral characteristics were investigated.  相似文献   

4.
Formalism is developed in which contributions of binary and ternary interactions towards free energy of a mixture of low-spin (A) and high-spin (B) isomers of spin crossover compounds as well as effects of ordering are taken into account. Parameters characterising non-ideality in this formalism are the excess free energy (ΔF ex) and absolute asymmetries (Δ A , Δ B ) of splittings of free energy levels. The excess free energy characterises the effects of binary interactions whereas asymmetries arise from ternary interactions. According to this model, the plateau in the spin crossover transition curve originates from the phenomenon of ordering taken into account in the Gorsky-Bragg-Williams approximation.  相似文献   

5.
The crystal and molecular structure of bis(1-vinylimidazole)diacetatozinc (C14H18N4O4Zn), a highly effective antidote and antihypoxic drug, was determined [R1 0.0335 for 8902 unique reflections with I > 2σ(I) and wR2 0.0931 for all 10 752 unique reflections]. The triclinic unit cell contains two independent molecules of the complex, A and B. These molecules have short contacts O?H-C. The zinc atoms in molecules A and B have distorted tetrahedral coordination with the coordination sites occupied by the imidazole nitrogen atoms and acetate oxygen atoms. The lengths of the Zn-N bonds (2.019–2.050 Å) and Zn-O bonds with three acetate groups (1.956–1.958 Å) are typical for zinc complexes, whereas the Zn-O3 bond with one of the acetate groups in molecule A is somewhat longer, 2.009(1) Å; also, there is an additional contact of the zinc atom with the carbonyl oxygen atom of this group (Zn-O4 2.498 Å).  相似文献   

6.
Oxepin and azepin are heterocyclic compounds with a seven-membered ring, which are present in the main skeleton of many anti-depressive drugs. Planar configuration instability due to the pseudo Jahn-Teller effect (PJTE) in oxepin, azepin and six their halogen substituted derivatives were investigated as an original PJTE study. Optimization and the following frequency calculations in these two series illuminated that all of these eight compounds were unstable in high-symmetry planar (with C 2v symmetry) configuration and their structures were puckered to lower C s symmetry stable geometry. Moreover, the vibronic coupling interaction between 1 A 1 ground and the first 1 B 1 excited states via (1 A 1 + 1 A 1 + 1 B 1) ? b 1 and (1 A 1 + 1 B 1 + 1 A 1 ) ? b 1 PJTE problems were the reasons for the symmetry breaking phenomenon and non-planarity of the seven-member ring in those series. Finally, numerical fitting of the adiabatic potential energy surface (APES) cross-sections along the b 1 puckering coordination was employed to estimate the vibronic coupling constants of PJTE problems for all the considered compounds.  相似文献   

7.
It has been shown that, in order to accomplish frontal photopolymerization in the mode of a self-sustained travelling wave, it is necessary to use compositions that are optically transparent behind the front and experience the onset of gelling at a minimal degree of polymerization, e.g., systems based on oligoether (meth)acrylates. With the use of a composition containing oligocarbonate methacrylate and the o-benzoquinone-amine photoinitiator system, frontal photopolymerization in a layer of more than 100 mm in thickness was experimentally revealed. It was shown that the photoinitiator and monomer conversion fronts synchronously propagate into the layer. It was found that the coordinate of the leading edge of the monomer conversion front h is related to the irradiated time τ by the equations h = A 1 log τ ? B and h = A 2 τ ? B at the first and the second step of frontal polymerization, respectively. It was found that the thickness of the area of the formulation layer in which the condition h = A 1 logτ ? B is fulfilled is equal to the width of the photoinitiator and monomer conversion front. A general equation of motion of the coordinate of the photoinitiator conversion label in the layer of a liquid photopolymerizable composition during sustained frontal photopolymerization was proposed for describing experimental data.  相似文献   

8.
The products of 4′,5′-dibromobenzo-15-crown-5 (I) cyanation by the Rosenmund-Braun reaction are studied by the 1H NMR and IR spectroscopy methods. X-ray diffraction analysis of two isolated products, i.e., di(4′,5′-dicyanobenzo-15-crown-5) 1.6 hydrate {(CN)2B15C5}2 · 1.6H2O (IIa) and 4′,5′-dicyanobenzo-15-crown-5,4′-cyano-5′-cyano(bromo)benzo-15-crown-5 dihydrate (CN)3.85Br0.15(B15C5)2 · 2H2O (III) is performed. Crystals IIa are monoclinic, a = 15.882(2) Å, b = 11.412(2) Å, c = 18.484(3) Å, β = 100.717(3)°, V = 3291.7(9) Å3, Z = 4, space group P21/c, R = 0.0746 for 4775 reflections with I > 2σ(I). Crystals III are monoclinic, a = 15.956(3) Å, b = 11.425(2) Å, c = 18.865(4) Å, β = 99.32(3)°, V = 3394(1) Å3, Z = 4, space group P21/c, R = 0.0692 for 2070 reflections with I > 2σ(I). Compounds IIa and III have similar structures with two crystallographically independent molecules in each (A and B in IIa; C and D in III). Four of the five O atoms of a macrocycle in molecules A and C form hydrogen bonds with the water molecules. The latter molecules lie above and below the cycle plane at a distance of ~2 Å from this plane. The A and C molecules have identical conformations (TTG TTG TTG TTG TTC) that differ from those of molecules B (TTG TGG STT SSG TTC) and D (TTC TSG STT SSG TTC).  相似文献   

9.
A series of para-substituted aromatic aminonitrones p-RC6H4C(NH2)=N+(Me)O (R = NMe2, H, Br, Cl, CF3) have been prepared. Acidity constants of the conjugate acids RC6H4C(NH2)N+(Me)OH at 25°C in a EtOH–H2O mixture (5: 95) have been determined by potentiometric titration. A linear correlation between log (kR/kH) and σpara values has been revealed, and a ρ298para) parameter has been determined as of 0.635.  相似文献   

10.
An Hand der denkbar einfachsten chemischen Reaktion\(A\underset{2}{\overset{1}{\longleftrightarrow}}B\) wird gezeigt, daß die Geschwindigkeitskoeffizienten (Gk)k 1 undk 2 sowie ihr Quotient, also die Gleichgewichtskonstante (Glk)K=k 1/k 2,keine Eigene xistenz beistzen. Sie werden erst dann physikalischwinklich und sinnvoll, wenn sie mit ihrenStoffgrößen gepaart sind, ink 1 A undk 2 B und Geschwindigkeiten, inKA=B zum Gleichgewichte.  相似文献   

11.
The bimolecular and termolecular complexes involving PO2Cl and XCN/C6H6 (X = F, Cl, Br) were designed to form the π-hole pnicogen bonds and σ-hole halogen bonds, to compare the two types of interactions and investigate the mutual influences between them. PO2Cl was used as simultaneous π-hole and σ-hole donor; it can interact with electron donor to form π-hole pnicogen bond and σ-hole halogen bond. The π-hole interactions are stronger than the σ-hole interactions, in both the bimolecular and the termolecular complexes. Comparing the mutual effects of the π-hole interactions and σ-hole interactions, the π-hole interaction has a greater influence on the σ-hole interaction than vice versa. With the addition of σ-hole halogen bond, the V S,max value outside the π-hole region of PO2Cl becomes decreasingly positive, resulting in a weaker π-hole interaction. With the addition of π-hole pnicogen bond, the V S,max value outside the σ-hole region of PO2Cl becomes small, also resulting in a weaker σ-hole interaction. The π-hole pnicogen bond and σ-hole halogen bond weaken each other, i.e., there is a negative cooperative effect in the termolecular complexes.  相似文献   

12.
Linear isotherm regularity works very well for fluids at high densities, and it has been shown that it is compatible with the EOSs based on statistical–mechanical theory. On the other hand, at low densities, the first few terms of virial EOS have the most contribution to express the deviations from ideal behavior. For finding similarities between dense and dilute states, experimental pvT data of 14 fluids (He, Ne, Ar, Kr, H2, O2, N2, CO, NH3, CH3OH, CH4, C2H4, C2H6 and C3H8) are examined. Comparing the thermal dependencies of the attraction and repulsion terms (A and B) of the LIR with the second and third virial coefficients (B 2 and B 3) in liquid and supercritical regions (0.7 < T r < 3.0) shows a remarkable similarity. Square-well potential is applied to examination and comparison of theoretical results with experimental results. It is shown that in liquid and supercritical regions, (1) the short-range potential governs among particles in dense fluids, and the long-range interactions become important in the less dense fluid, (2) similar to Boyle temperature, T B, in dilute state, there is a temperature as TB (in dense fluids) that the attractive forces and the repulsive forces acting on the dense-fluid particles balance out; thus, probably there is a maximum σ (molecular diameter) at nearly 2T c (TB), and (3) in the liquid and supercritical regions (0.7 < T r < 3.0), in the first-order approximation, there are no significant interactions higher than triple interactions in dense-fluid particles.  相似文献   

13.
The electrochemical behavior of Ni cermet electrode with CeO2 ? x additive in contact with YSZ electrode was studied by means of impedance spectroscopy in H2, H2O, CO2, CO, He, and Ar gas media of various composition within the temperature range of 700 to 950°C. Near the equilibrium potential, the electrochemical impedance spectra of the studied electrodes indicate to three stages of electrode reaction. The polarization conductivity of the low-frequency stage of electrode reaction (σlf) is characterized with the following regularities: (a) temperature dependence of σlf has a positive slope in Arrhenius coordinates; (b) σlf increases upon replacement of gas mixture with lower mutual diffusion coefficient by mixture with higher mutual diffusion coefficient, while polarization conductivity values of other stages remain practically invariable; (c) concentration relationships of 1/σlfrecorded for constant activity of oxygen in the gas phase are linear in the 1/σlf vs. 1/P CO 2 (P CO) coordinates; (d) no low-frequency stage of the electrode reaction is observed upon electrochemical inflow (outflow) of the gas reagents (reaction products) to (from) the test electrodes (current passing through closely pressed specimens and central specimen impedance measurement); and (e) no change in the gas flow rate affects σlf value. The observed regularities were explained by assuming the gas diffusion nature of the low-frequency stage of the electrode reaction. The gas diffusion layer thickness was estimated.  相似文献   

14.
Structural parameters and IR spectra of the (1A1//C4v)-PcLuCl, (2B2//C4v)-PcYbCl, and (8A2//C4v)-PcGdCl molecules, (2A2//C4v)-Pc+LuCl, (3B1//C4v)-Pc+YbCl, and (9A1//C4v)-Pc+GdCl cations, (1Ag//D2h)-PcLuCl2LuPc dimer, and PcLuCl···PcLuCl coaxial molecular pair have been simulated using the DFT (U) PBE0/SDD method. The PcLnCl (Ln = Lu, Yb, Gd) molecules have exhibited the equilibrium Ln–N bond length of 222, 223, and 230 pm, the Ln–Cl bond length of 245, 246, and 253 pm, the dipole moment of 4.73, 4.57, and 4.84 D directed from Cl to Ln, and ionization potential of 6.6 eV. β-Decay (1A1//C4v)-Pc177LuCl → (1A1//C4v)-(Pc177mHfCl)+ occurs with no significant change of the charge on the metal atom.  相似文献   

15.
Critical phenomena of liquid phase stratification in ternary systems are considered. Models of the T-x 1-x 2 phase diagrams with critical and tricritical liquid solution points and isothermal diagrams over the corresponding interinvariant intervals are given.  相似文献   

16.
The influence of silver myristate used as a precursor of silver nanoparticles on the direct current conductivity σ dc of epoxy polymer within the concentration range of ≤0.8 wt % was investigated. The value of direct current conductivity was determined on the basis of analysis of the frequency dependence of complex permittivity within the frequency range of 10?2–105 Hz. The temperature dependence of σ dc is composed of two regions. The dependence corresponds to the Vogel-Fulcher-Tammann empirical law σ dc = σ dc0exp{?DT 0/(T-T 0)} (where T 0 is the Vogel temperature and D is the strength parameter) at temperatures higher than the glass transition temperature T g. At the same time, T 0 does not depend on the concentration of nanoparticles. The Arrhenius temperature dependence characterized by activation energy about 1.2 eV is observed at temperatures lower than T g. The observed shape of the temperature dependence is related to the change in the mechanism of conductivity after “freezing” of ionic mobility at temperatures lower than T g. The value of σ dc is increased as the concentration of nanoparticles is raised within the temperature range of T > T g. The obtained dependence of σ dc on silver myristate concentration is similar to the root one, indicating the absence of percolation within the studied range of concentrations.  相似文献   

17.
The rate constants were determined for a number of reactions of nucleophilic addition of para-substituted benzamidoximes 4-RC6H4C(NH2)=NOH to cis-[PtCl2(EtCN)2] at 23°C in acetone. A linear correlation between log (k R/k H) and σ para was found, and reaction constant ρ296 para ) was calculated. The prepared compounds were characterized by IR, 1H NMR, and HR ESI+-MS.  相似文献   

18.
We have studied the transition from an Arrhenius-like to a non-Arrhenius-like structural relaxation behavior in fragile glass-forming liquids. This transition is denoted by the temperature TA that usually occurs above the melting point Tm and the dynamic crossover temperature TB. Recent studies reveal that TA is a characteristic temperature related with the dynamical properties of the system. However, its unambiguous determination is not easy. In this work, a method to obtain the temperature TA from the experimental data of α-relaxation time is presented. The obtained TA is compared with the cooperativity onset temperature Tx extracted from the bond strength–coordination number fluctuation model. The result reveals that TA is close to Tx for fragile liquids. From the result of the present analyses combined with the linear relation Tx \(\propto\) T0, where T0 is the Vogel temperature, the Arrhenius crossover phenomenon in fragile liquids is linked to the low-temperature structural relaxation dynamics.  相似文献   

19.
A density functional theory investigation on the structural and bonding properties of B3S n ?/0 (n = 2–4) series has been performed. Based on B3LYP and CCSD(T) calculations, we present the linear D ∞h B3S2 ? (1, 3Σg) and D ∞h B3S2 (2, 2Πu), the Y-shaped C 2v B3S3 ? (3, 1A1) and C 2v B3S3 (4, 2B2), and perfectly planar structures C 2v B3S4 ? (5, 1A1) and C 2v B3S4 (6, 2B2) that contain rhombic B2S2 rings. The 16 ground-state structures are planar with linear “B–B–B” core, in which the first and the second S atoms prefer to bond terminally to the terminal B, and the third S atom bonds to the center B, however, when the third S atom is added with the fourth, the atoms tend to be in the bridging positions of two adjacent B atoms. The growth pattern of B3S n ?/0 (n = 2–4) clusters helps to understand the structural properties of the other small boron sulfide clusters. Bonding analyses reveal that a dual or single three-center one-electron (3c–1e) π hypervalent bonds located over the “B–B–B” core of D ∞h B3S2 ? (1) and B3S2 (2), respectively. While C 2v B3S4 ? (5) and B3S4 (6) with rhombic B2S2 rings as the center with –BS and –S units all possess 4c–4e bonds (o-bonds) in the rhombic B2S2 rings.  相似文献   

20.
The binuclear copper(II) complexes with acyldihydrazones formed by 1,4-cyclohexanedicarboxylic acid and salicylaldehyde or 2-hydroxyacetophenone were synthesized and studied. The structure of the complex with 1,4-cyclohexanedicarboxylic acid bis(salicylidene)hydrazone (H4L1) [Cu2L1(Py)2] was studied by X-ray diffraction. The crystals are triclinic: a = 8.1852(4) Å, b = 8.5157(5) Å, c = 11.6553(7) Å, α = 80.678(3)°, β = 70.041(4)°, γ = 74.803(3)°. Space group \(P\bar 1\), Z = 1. The number of symmetrically independent reflections with I > 2(σ(I)) is 2245, R = 0.0395; R w = 0.0917. The complex contains two equivalent copper atoms located at a 10.772 Å distance from each other. The coordination polyhedra have a square geometry and are involved in the intermolecular π/π-stacking. The EPR spectra of solutions of the binuclear complexes show an isotropic signal of seven HFS lines (g = 2.113–2.118, A Cu ≈ 38 G), indicating interaction between the unpaired electrons and the two equivalent copper nuclei. The possible exchange interaction channels were analyzed.  相似文献   

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