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1.
The nature of halogen bonds of the Y?X‐?‐π(C6H6) type (X, Y=F, Cl, Br, and I) have been elucidated by using the quantum theory of atoms in molecules (QTAIM) dual‐functional analysis (QTAIM‐DFA), which we proposed recently. Asterisks (?) emphasize the presence of bond‐critical points (BCPs) in the interactions in question. Total electron energy densities, Hb( r c), are plotted versus Hb( r c)?Vb( r c)/2 [=(?2/8m)?2ρb( r c)] for the interactions in QTAIM‐DFA, in which Vb( r c) are potential energy densities at the BCPs. Data for perturbed structures around fully optimized structures were used for the plots, in addition to those of the fully optimized ones. The plots were analyzed by using the polar (R, θ) coordinate for the data of fully optimized structures with (θp, κp) for those that contained the perturbed structures; θp corresponds to the tangent line of the plot and κp is the curvature. Whereas (R, θ) corresponds to the static nature, (θp, κp) represents the dynamic nature of the interactions. All interactions in Y?X‐?‐π(C6H6) are classified by pure closed‐shell interactions and characterized to have vdW nature, except for Y?I‐?‐π(C6H6) (Y=F, Cl, Br) and F?Br‐?‐π(C6H6), which have typical hydrogen‐bond nature without covalency. I?I‐?‐π(C6H6) has a borderline nature between the two. Y?F‐?‐π(C6H6) (Y=Br, I) were optimized as bent forms, in which Y‐?‐π interactions were detected. The Y‐?‐π interactions in the bent forms are predicted to be substantially weaker than those in the linear F?Y‐?‐π(C6H6) forms.  相似文献   

2.
The hydrogen-hydrogen nonbonded potential which may be derived from the calculated interactions between hydrogen molecules has been obtained. The best three-parameter Buckingham function gave an RMS error of 0.18 kcal/mol in fitting Price and Stone's ab initio data for 130 pairs of hydrogen molecules, which may be compared with an RMS error of 0.74 kcal/mol using the parameters in the MM2 force field. Burton's basis set is also considered. A better fit to these data requires that the angular relationship between the bonds be included. The data for hydrogen as well as experimental data for chlorine show that these atoms appear “larger” normal to the bond axis than along the axis, and this is probably also the case for other atoms. When simple angular terms are added it is possible to fit the Price and Stone data set with an RMS error of less than 0.06 kcal/mol. The preferred function was: V = [a0 + a1(sin θ1 + sin θ2)4 + a2r]e?3r ? [c0 + c1(1 + sinθ1sinθ2)]/r5. Deficiencies in the current ab initio data are discussed.  相似文献   

3.
A dissociative force field for all-atomistic molecular dynamics calculations has been developed to investigate impact fracture of polymers accompanying dissociation of chemical bonds of polymer main chain. Energy of dimer molecules was evaluated as a function of both bond-length b and bond-angle θ by CASPT2 calculations, whose quality is enough to describe dissociation of chemical bonds. Because we found that the bond dissociation energy D decreases with increasing bond-angle, we employed the Morse-type function VBond(b, θ) = {DVAngle(θ)}[1 − exp{−α(bb0) − β(bb0)2}] where a quartic function VAngle(θ) = k1(θθ0) + k2(θθ0)2 + k3(θθ0)3 + k4(θθ0)4 . This function reproduced well the CASPT2 potential energy surface in a wide range of b and θ. The parameters have been obtained for four popular glassy polymers, polyethylene, poly(methyl methacrylate), poly(styrene), and polycarbonate. © 2019 Wiley Periodicals, Inc.  相似文献   

4.
The wavefunction of a decaying state is expressed in terms of complex coordinates as ψ(p) = a(θ)ψ o(p) + b(θ)x(p), where the square integrable θo(p) and x(p) contain the localized and asymptotic information respectively. From Fano theory, we derive the relationship of a(?) and b(?) to the energy and width of the resonance state. This forms the basis for a new variatfonal principle for optimization of trial functions in the complex coordinate—energy plane.  相似文献   

5.
The intermolecular interactions existing at three different sites between phenylacetylene and LiX (X = OH, NH2, F, Cl, Br, CN, NC) have been investigated by means of second‐order Møller?Plesset perturbation theory (MP2) calculations and quantum theory of “atoms in molecules” (QTAIM) studies. At each site, the lithium‐bonding interactions with electron‐withdrawing groups (? F, ? Cl, ? Br, ? CN, ? NC) were found to be stronger than those with electron‐donating groups (? OH and ? NH2). Molecular graphs of C6H5C?CH···LiF and πC6H5C?CH···LiF show the same connectional positions, and the electron densities at the lithium bond critical points (BCPs) of the πC6H5C?CH···LiF complexes are distinctly higher than those of the σC6H5C?CH···LiF complexes, indicating that the intermolecular interactions in the C6H5C?CH···LiX complexes can be mainly attributed to the π‐type interaction. QTAIM studies have shown that these lithium‐bond interactions display the characteristics of “closed‐shell” noncovalent interactions, and the molecular formation density difference indicates that electron transfer plays an important role in the formation of the lithium bond. For each site, linear relationships have been found between the topological properties at the BCP (the electron density ρb, its Laplacian ?2ρb, and the eigenvalue λ3 of the Hessian matrix) and the lithium bond length d(Li‐bond). The shorter the lithium bond length d(Li‐bond), the larger ρb, and the stronger the π···Li bond. The shorter d(Li‐bond), the larger ?2ρb, and the greater the electrostatic character of the π···Li bond. © 2012 Wiley Periodicals, Inc.  相似文献   

6.
Five new complex compounds of the formula Ln(phen)2(NO3)3 were prepared. The X‐ray structural analyses indicate that they crystallize isostructurally in the monoclinic space group C2/c (no. 15) with cell dimensions for example for Pr(phen)2(NO3)3: a = 11.194(1) Å, b = 18.095(2) Å, c = 13.101(2) Å, β = 100.52(1)°, V = 2609.1(6) Å3, Z = 4. The crystal structures consist of [Ln(phen)2(NO3)3] complex molecules. The rare earth atoms are coordinated by four N atoms of two phen ligands and six O atoms of three nitrato groups to complete a distorted bicapped dodecahedron. The [Ln(phen)2(NO3)3] complex molecules are assembled via π‐π stacking interactions between the neighboring phen ligands to form 1D columnar chains, which are then arranged in the crystal structures according to pseudo 1D close‐packed patterns.  相似文献   

7.
The time‐dependent quantum wave packet and the quasi‐classical trajectory (QCT) calculations for the title reactions are carried out using three recent‐developed accurate potential energy surfaces of the 11A′, 13A′, and 13A″ states. The two commonly used polarization‐dependent differential cross sections, dσ00/dωt, dσ20/dωt, with ωt being the polar coordinates of the product velocity ω′, and the three angular distributions, Pr), Pr), and Prr), with θr, Φr being the polar angles of the product angular momentum, are generated in the center‐of‐mass frame using the QCT method to gain insight into the alignment and the orientation of the product molecules. Influences of the potential energy surface, the collision energy, and the isotope mass on the stereodynamics are shown and discussed. Validity of the QCT calculation has been examined and proved in the comparison with the quantum wave packet calculation. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010  相似文献   

8.
We use quantum theory of atoms in molecules (QTAIM) and the stress tensor topological approaches to explain the effects of the torsion φ of the C‐C bond linking the two phenyl rings of the biphenyl molecule on a bond‐by‐bond basis using both a scalar and vector‐based analysis. Using the total local energy density H( r b), we show the favorable conditions for the formation of the controversial H–H bonding interactions for a planar biphenyl geometry. This bond‐by‐bond QTAIM analysis is found to be agreement with an earlier alternative QTAIM atom‐by‐atom approach that indicated that the H–H bonding interaction provided a locally stabilizing effect that is overwhelmed by the destabilizing role of the C‐C bond. This leads to a global destabilization of the planar biphenyl conformation compared with the twisted global minimum. In addition, the H( r b) analysis showed that only the central torsional C‐C bond indicated a minimum for a torsion φ value coinciding with that of the conventional global energy minimum. The H–H bonding interactions are found to be topologically unstable for any torsion of the central C‐C bond away from the planar biphenyl geometry. Conversely, we demonstrate that for 0.0° < φ < 39.95° there is a resultant increase in the topological stability of the C nuclei comprising the central torsional C‐C bond. Evidence is found of the effect of the H–H bonding interactions on the torsion φ of the central C‐C bond of the biphenyl molecule in the form of the QTAIM response β of the total electronic charge density ρ( r b). Using a vector‐based treatment of QTAIM we confirm the presence of the sharing of chemical character between adjacent bonds. In addition, we present a QTAIM interpretation of hyperconjugation and conjugation effects, the former was quantified as larger in agreement with molecular orbital (MO) theory. The stress tensor and the QTAIM H atomic basin path set areas are independently found to be new tools relevant for the incommensurate gas to solid phase transition occurring in biphenyl for a value of the torsion reaction coordinate φ ≈ 5°. © 2015 Wiley Periodicals, Inc.  相似文献   

9.
Two new potassium vanadium phosphates have been prepared and their structures have been determined from analysis of single crystal X-ray data. The two compounds, K3(VO)(V2O3) (PO4)2(HPO4) and K3(VO)(HV2O3)(PO4)2(HPO4), are isostructural, except for the incorporation of an extra hydrogen atom into the nearly identical frameworks. The structures consist of a three-dimensional network of [VO]n chains connected through phosphate groups to a [V2O3] moiety. Magnetic susceptibility experiments indicate that in the case of the di-hydrogen compound, there are no significant magnetic interactions between the three independent vanadium (IV) centers. Crystal data: for K3(VO)(V2O3)(PO4)2 (HPO4), Mr = 620.02, orthorhombic space group Pnma (No. 62), a = 7.023(4) Å, b = 13.309(7) Å, c = 14.294(7) Å, V = 1336(2) Å3, Z = 4, R = 5.02%, and Rw = 5.24% for 1238 observed reflections [I > 3σ(I)]; for K3(VO)(HV2O3)(PO4)2(HPO4), Mr = 621.04, orthorhombic space group Pnma (No. 62), a = 6.975(3) Å, b = 13.559(7) Å, c = 14.130(7) Å, V = 1336(1) Å3, Z = 4, R = 6.02%, and Rw = 6.34% for 1465 observed reflections [I > 3σ(I)].  相似文献   

10.
Two polymorphs of a zero‐dimensional (molecular) zinc phosphate with the formula [Zn(2,2′‐bipy)(H2PO4)2]2 have been synthesized by a mild hydrothermal route and their crystal structures were determined by single crystal X‐ray diffraction (triclinic, space group (No. 2), Z = 2, α‐form: a = 8.664(1), b = 8.849(2), c = 10.113(2) Å, α = 97.37(2)°, β = 100.54(2)°, γ = 100.98(2)°, V = 737.5(3) Å3; β‐form: a = 7.5446(15), b = 10.450(2), c = 10.750(2) Å, α = 67.32(3)°, β = 81.67(3)°, γ = 69.29(3)°, V = 731.4(3) Å3). Both structures consist of distorted trigonal‐bipyramidal ZnO3N2 units condensed with PO2(OH)2 tetrahedra through common vertices giving rise to dimers [Zn(2,2′‐bipy)(H2PO4)2]2. The structures are stabilized by extensive inter‐ and intramolecular hydrogen bond interactions. Both modifications display subtle differences in their packing originating from the hydrogen bond interactions as well as π…π interactions between the organic ligands.  相似文献   

11.
The crystal structures of an unexpected carbon dioxide inserted carbamidiphenylthiophosphinic anhydride and l‐[(4‐nitrophenyl) sulfonyl]‐trans‐2, 5‐pyrrolidinedicarboxylic acid methyl ester were determined by X‐ray analysis. They crystallized in the space group P21(#4) with a =0.9550(2), b = 0.9401(4), c= 1.2880(2) nm, β= 107.74°, V= 1.1013 (5) nm3, Dcaled= 1.349 g/cm3, Z = 2 and P212121(# 19) with a = 1.4666(2), b = 0.7195(2), c = 1.6339(2) nm, V = 1.7240(7) nm3, Dcaled = 1.434 g/cm3, Z = 4, respectively. Through the investigation of these two crystal structures, the mechanistic insights into this unexpected carbon dioxide insertion in the reaction of trans‐2,5‐disubstituted pyrrolidine with diphenylthiophosphoryl chloride in the presence of potassium carbonate were disclosed.  相似文献   

12.
Topological properties of potential energy and electronic density distribution on five reaction paths X+H2→XH+H (X=H, N, HN, H2C, NC) are investigated at the level of UMP2/6–311G(d,p). It has been found that in the region of the reaction paths studied, where B(rc)|s>0 [B(rc)|s is the product of ρ(rc) and ∇2ρ(rc) at the point of reaction process, i.e., B(rc)|s=ρ(rc)∇2 ρ(rc)] is basically the same as the region of V′(s)<0[V′(s) is the second derivative of potential energy with respect to the reaction coordinate, i.e., V′(s)=d2V/ds2], and the point with maximum B(rc)|s is almost coincident with the point of minimum V′(s). It can be concluded from the calculated results that there is a good correlation between the topological properties of potential energy and electronic density distribution along the reaction path. The structure transition state of such collinear reactions may be determined by topological analysis of electronic density. © 1997 John Wiley & Sons, Inc. J Comput Chem 18: 1167–1174  相似文献   

13.
By studying the thermal condensation of melamine, we have identified three solid molecular adducts consisting of melamine C3N3(NH2)3 and melem C6N7(NH2)3 in differing molar ratios. We solved the crystal structure of 2 C3N3(NH2)3?C6N7(NH2)3 ( 1 ; C2/c; a=21.526(4), b=12.595(3), c=6.8483(14) Å; β=94.80(3)°; Z=4; V=1850.2(7) Å3), C3N3(NH2)3?C6N7(NH2)3 ( 2 ; Pcca; a=7.3280(2), b=7.4842(2), c=24.9167(8) Å; Z=4; V=1366.54(7) Å3), and C3N3(NH2)3?3 C6N7(NH2)3 ( 3 ; C2/c; a=14.370(3), b=25.809(5), c=8.1560(16) Å; β=94.62(3)°; Z=4; V=3015.0(10) Å3) by using single‐crystal XRD. All syntheses were carried out in sealed glass ampoules starting from melamine. By variation of the reaction conditions in terms of temperature, pressure, and the presence of ammonia‐binding metals (europium) we gained a detailed insight into the occurrence of the three adduct phases during the thermal condensation process of melamine leading to melem. A rational bulk synthesis allowed us to realize adduct phases as well as phase separation into melamine and melem under equilibrium conditions. A solid‐state NMR spectroscopic investigation of adduct 1 was conducted.  相似文献   

14.
Two coordination polymers, [Co(phen)(oba)(H2O)2] ( 1 ) and [Cd3(phen)3(oba)2(Hoba)2(H2O)2] ( 2 ) (oba = 4, 4′‐oxybis(benzoate), phen = 1, 10‐phenanthroline) have been synthesized under hydrothermal conditions. Complex 1 crystallizes in monoclinic, P21/n, a = 7.543(6), b = 33.05(2), c = 9.902(5)Å, β = 103.69(2)°, V = 2398(3)Å3, Z = 4; 2 in monoclinic, P2/n, a = 15.11(1), b = 10.069(8), c = 28.02(2)Å, β = 101.83(1)°, V = 4174(5)Å3, Z = 2. X‐ray single‐crystal diffraction investigations shows that the complexes 1 and 2 consist of helical chains, which are further assembled into layers and networks via supramolecular interactions such as π—π stacking interactions and hydrogen bonds, respectively. The results indicate that the coordination environment is one of the most important factors for assembly of single‐stranded helical chains into double‐stranded helical chains via supramolecular interactions.  相似文献   

15.
16.
We propose a new exactly solvable ring‐shaped potential V(r,θ) = ?(α/r) + (σ/r2) + β cos2θ/(r2sin2θ). The exact bound‐state solutions are presented explicitly. The creation and annihilation operators are established directly from the normalized radial wave functions. We present two important recurrence relations among the diagonal matrix elements and obtain some explicit expressions of mean values of rk (8 ≥ k ≥ ?11). The exact form of continuum states is also obtained analytically. Comments are made on the calculation formula of phase shifts and the analytical properties of the scattering amplitude. It is interesting to find that the exact form of continuum states will reduce to that of the bound states at the poles of the scattering amplitude. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005  相似文献   

17.
In modern cancer therapy the clinical application of platinum‐based drugs is more and more limited by the occurrence of intrinsic or acquired resistances. In this context the potential use of dinuclear platinum complexes in chemotherapy is increasingly relevant. The novel complexes Pd(Bzdpa)Cl2, Pd2(C4H8(dpa)2)Cl4, and Pt2(C4H8(dpa)2)Cl4 allow a direct comparison of mono‐ and dinuclear palladium and platinum complexes respectively deriving from a 2,2′‐dipyridylamine (Hdpa) ligand system. They were characterized by single crystal X‐ray analysis as well as infrared spectroscopy and elemental analysis. The cisplatin analogous mononuclear palladium complex Pd(Bzdpa)Cl2 ( 1 ) (Bzdpa: (2,2′‐dipyridylbenzyl)amine) belongs to a range of 2,2′‐dipyridylamine‐based compounds which were extensively studied in our laboratories. 1 crystallizes in the orthorhombic space group Pna21 with a = 13.722(3), b = 13.457(3), c = 9.483(2), V = 1751.1(6) Å3, and Z = 4. The metal binding motif of 1 was expanded by a flexible butyl‐linker to form the tetradentate C4H8(dpa)2 ligand. The resulting isotypic dinuclear complexes Pd2(C4H8(dpa)2)Cl4·2CH3CN ( 2 ) and Pt2(C4H8(dpa)2)Cl4·2CH3CN ( 3 ) crystallize in the triclinic space group with a = 7.8427(2), b = 8.7940(2), c = 11.7645 (3), α = 79.219(2)°, β = 84.033(2)°, γ = 87.744(2)°, V = 792.58(3) Å3 ( 2 ) and a = 7.831(5), b = 8.814(5), c = 11.817(5), α = 79.271(5)°, β = 83.571(5)°, γ = 88.063(5)°, V = 796.3(8) Å3 ( 3 ), both with one centrosymmetrical molecule in the unit cell.  相似文献   

18.
Molecular dynamics and Rotational Isomer State/Monte Carlo techniques with a Dreiding 1.01 Force Field are employed to study the excimer formation of isolated 1,3‐di(1‐pyrenyl)propane and the probe adsorbed into a low‐density polyethylene (LDPE) matrix model. The probability of formation of each molecular conformer at several temperatures was calculated using these theoretical techniques. Conformational statistical analysis of the four torsion angles (ϕ1, ϕ2, θ1, θ2) of Py3MPy showed that the angles —C—Car— (ϕ1, ϕ2) present two states c ± = ±90°; and the angles —C—C— (θ1, θ2), the three trans states = 180°, g ± = ±60°. The correlation of θ1θ2 torsion angles showed that the most probable pairs were g+g and gg+ for the excimer‐like specimens, although these angles are distorted because of interactions with the polymer matrix. The temperature dependence of the excimer‐formation probability revealed that this process was thermodynamically controlled in the isolated case. When the probe was adsorbed into the LDPE matrix, the excimer formation process was reversed at T = 375 K. At T >  375 K, the behavior was similar to the isolated case but, at T < 375 K, excimer formation probability increased with temperature as found experimentally by steady‐state fluorescence spectroscopy. This temperature was coincident with the onset of the LDPE melting process, determined experimentally by thermal analysis.  相似文献   

19.
Ag6(VIVO)2(PO4)2(P2O7) was obtained by reaction of Ag3PO4 and (VO)2P2O7 (sealed ampoule, 550 °C, 3 d). The crystal structure of the new mixed ortho‐pyrophosphate was determined from X‐ray single‐crystal data [Pnma, Z = 4, a = 12.759(3) Å, b = 17.340(4) Å, c = 6.418(1) Å, R1 = 0.071, wR2 = 0.184 for 3174 unique reflections with Fo > 4σ(Fo), 141 variables]. Ag+ ions are located in between layers [(VIVO)2(PO4)2(P2O7)]6–. Equilibrium relations of the new phosphate to neighboring phases were determined. The electronic structure of the (VIV≡O)2+ group was investigated by polarized electronic absorption spectroscopy (ν̃1a = 9450 cm–1, ν̃1b = 9950 cm–1, ν̃2 = 14750 cm–1), EPR spectroscopy [X‐ and Q‐band, powder and single crystal, orthorhombic crystal g‐tensor with g1 = 1.9445(3), g2 = 1.9521(3), g3 = 1.9695(3)], and magnetic measurements (powder, μexp/μB = 1.71, Θp = –1.7 K).  相似文献   

20.
运用三足四齿配体三(2-甲基吡啶)胺(TPA)或三(2-甲基苯丙咪唑)胺(TBA),得到两个双核铁(III)配合物,[Fe2L22-O)(μ2-p-NH2-C6H4COO)]3+ (L = TPA, 1 和 L = TBA, 2)。两个配合物均为单斜晶系,空间群为P2(1)/c.晶胞参数 1: a = 1.4529(4), b = 1.6622(5), c = 2.0625(6) nm, β= 100.327(5)º, V = 4.900(3) nm3, z = 4, F(000) = 2344, 分子量Mr = 1142.91, Dc = 1.549 g/cm3, R1 = 0.0544, R2 = 0.0962. 2: a = 1.3378(4), b = 2.1174(7), c = 2.4351(7) nm, β= 97.315(6)º, V = 6.842(4) nm3, z = 4, F (000) = 3116, 分子量Mr = 1505.08, Dc = 1.444 g/cm3, R1 = 0.0793, R2 = 0.1623. 在两个双核铁(III)配合物中,中心的三价铁和配体TPA或TBA上的四个氮原子和两个氧原子通过不同的桥形成一个畸变的八面体构型。  相似文献   

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