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1.
The interaction of Cu2+ to the first 16 residues of the Alzheimer’s amyloid β peptide, Aβ(1–16) was studied by isothermal titration calorimetry at pH 7.2 and 37°C in aqueous solution. The Gholamreza Rezaei Behbehani
(GRB) solvation model was used to reproduce the enthalpies of interactions of Aβ(1–16) with glycine, Gly+Aβ(1–16), and Cu2+ ions, Cu2+ +Aβ(1–16), over the whole range of Cu2+ concentrations. The binding parameters recovered from the solvation model were attributed
to the structural change of Aβ(1–16) due to the glycine and Cu2+ interactions. It was found that there is a set of two identical binding sites for Cu2+ ions. p=2 indicates that the binding has positive cooperativity in the two binding sites. Aβ(1–16) structure is destabilized greatly as a result of binding to Cu2+ ions. 相似文献
2.
Three novel unsymmetric tridentate ligands, namely, ptmi (ptmi = 3-(1,10-phenanthroline-2-yl)-as-triazino[5,6-f]-5-methoxyisatin), pti (pti = 3-(1,10-phenanthroline-2-yl)-as-triazino-[5,6-f]isatin), ptni (ptni = 3-(1,10-phenanthroline-2-yl)-as-triazino[5,6-f]-5-nitroisatin), and their complexes [Ru(tpy)(ptmi)](ClO4)2 (tpy = 2,2′:6′,2″-terpyridine) (1), [Ru(tpy)(pti)](ClO4)2 (2), and [Ru(tpy)(ptni)](ClO4)2 (3) were prepared and characterized by elemental analysis, 1H NMR, ES–MS. The electrochemical behaviors were studied by cyclic voltammetry. The DNA-binding properties of these complexes
were investigated by the spectroscopic method, viscosity measurements, and thermal denaturation. Theoretical studies on these
complexes were also performed with the density functional theory (DFT) method. The experimental results showed that these
complexes bind to calf thymus (CT-DNA) in an intercalative mode. The order of DNA-binding affinities (A) of these complexes is A(1) < A(2) < A(3). The trend in the DNA-binding affinities of this series of complexes can be reasonably explained by the DFT calculations. 相似文献
3.
Limin Han Guangbin Zhang Ning Zhu Ruijun Xie Quanling Suo Meihua Luo Linhong Weng 《Journal of Cluster Science》2010,21(4):789-801
Two novel bimetallic complexes, [Cr(CO)3(η
6-C6H5)–C≡C–C6H4–Fc] (Fc = C5H5FeC5H4] (1) and [Cr(CO)3(η
6-C6H5)–C ≡ C–Fc–C(CH3)2–Fc] (3), were synthesized by the Sonogashira coupling reaction. By using of (1) and (3) as ligands to react with Co2(CO)8, two others novel polymetallic complexes, [Cr(CO)3(η
6-C6H5){Co2(CO)6-η
2-μ
2-C≡C–}–C6H4–Fc] (2) and [Cr(CO)3(η
6-C6H5){Co2(CO)6-η
2-μ
2-C≡C–}Fc–C(CH3)2–Fc] (4) were obtained. Four carbonyl complexes were characterized by elemental analysis, FT-IR, NMR and MS. The molecular structures
of complexes (1), (2) and (4) were determined by single crystal X-ray diffraction. The interactions among the ferrocenyl,
Cr(CO)3 and Co2(CO)6-η
2-μ
2-C≡C– units were investigated by cyclic voltammetry. 相似文献
4.
The conformational composition of gaseous MTMNB and the molecular structures of the rotational forms have been studied by
electron diffraction at 130∘C aided by results from ab initio and density functional theory calculations. The conformational potential energy surface
has been investigated by using the B3LYP/6-31G(d,p) method. As a result, six minimum-energy conformers have been identified.
Geometries of all conformers were optimized using MP2/6-31G(d,p), B3LYP/6-31G(d,p), and B3LYP/cc-pVTZ methods. These calculations
resulted in accurate geometries, relative energies, and harmonic vibrational frequencies for all conformers. The B3LYP/cc-pVTZ
energies were then used to calculate the Boltzmann distribution of conformers. The best fit of the electron diffraction data
to calculated values was obtained for the six conformer model, in agreement with the theoretical predictions. Average parameter
values (ra in angstroms, angle α in degrees, and estimated total errors given in parentheses) weighted for the mixture of six conformers
are r(C–C) = 1.507(5), r(C–C)ring, av = 1.397(3), r(C–S)av = 1.814(4), r(C–N) = 1.495(4), r(N–O)av = 1.223(3), ∠(C–C–C)ring = 116.0–122.5, ∠ C6–C4–C7 = 118.2(4), ∠ C–C–S = 113.6(6), ∠ C–S–C = 98.5(12), ∠ N–C–C4 = 121.9(3), ∠(O–N–C)av = 116.8(3), ∠ O–N–O = 127.0(4). Torsional angles could not be refined. Theoretical B3LYP/cc-pVTZ torsional angles for the
rotation about C–N bond, φC−N, were found to be 30.5–36.5∘ for different conformers. As to internal rotation about C–C and C–S bonds, values of φC−C = 68–118∘ and φC−S = 66–71∘ were obtained for the three most stable conformers with gauche orientation with respect to these bonds.
Some conclusions of this work were presented in a short communication in Russ. J. Phys. Chem. 2005, 79, 1701. 相似文献
5.
In this paper, evaluation of kinetic parameters (the activation energy – E,the pre-exponential factor – A and the reaction order – n) with simultaneous determination of the possible reaction mechanism of thermal decomposition of calcium hydroxide (portlandite),
Ca(OH)2 formed during hydration of commercial Portland-slag cement, by means of differential scanning calorimetry (DSC) in non-isothermal
conditions with a single heating–rate plot has been studied and discussed. The kinetic parameters and a mechanism function
were calculated by fitting the experimental data to the integral, differential and rate equation methods.
To determine the most probable mechanism, 30 forms of the solid-state mechanism functions, f(αc) have been tried. Having used the procedure developed and the appropriate program support, it has been established that the
non-isothermal thermal decomposition of calcium hydroxide in the acceleratory period (0.004<αc<0.554) can be described by the rate equation: d αc/dT=A/βexp(−E/RT)f(αc), which is based on the concept of the mechanism reaction:f(αc)=2(αc)1/2.
The mechanism functions as well as the values of the kinetic parameters are in good agreement with those given in literature.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
La0.8 A'0.2 MnO3+δ (A'=Sr, Ba, K, Cs) perovskites were studied by temperature-programmed reduction. The amount of non-stoichiometric oxygen was
found to decrease from δ=0.16 for LaMnO3+δ to δ=0.07 (Sr-), 0.06 (Ba-), 0.07 (K-) and 0.03 (Cs-) substituted manganites. The reducibility at low and mean-temperatures
(t<500°C) increased in the sequence La<(La, Sr)≈(La, Ba)<(La, Cs)<(La, K).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
B. N. Plakhutin 《Journal of Structural Chemistry》1997,38(1):1-9
The energy spectrum of the states that appear in structures of icosahedral (I,Ih symmetry with open electronic shells gN (dim g = 4; N = 1–7) is reported. The energies are obtained in terms of integral invariants (reduced matrix elements of electron-electron
interaction) Hk (g, g). The latter are analogs of the Slater-Condon parameters Fk(l,l) for atoms with the lN electronic configuration. A similar representation is proposed for the integrals mm’≨’) of electron-electron interaction
on the 4-fold degenerate g orbitals in the “standard” representation. The relation between the terms of the gN(I,Ih) configuration and the parent states of the orthogonal group O+(4) is discussed.
Translated fromZhurnal Strukturnoi Khimii, Vol. 38, No. 1, pp. 3–13, January–February, 1997. 相似文献
8.
Nina I. Giricheva Georgiy V. Girichev Yulia S. Medvedeva Sergey N. Ivanov Anna V. Bardina Vyacheslav M. Petrov 《Structural chemistry》2011,22(2):373-383
A combined gas-phase electron diffraction and quantum chemical (B3LYP/6-311+G**, B3LYP/cc-pvtz, MP2/cc-pvtz) study of molecular
structure of 2-nitrobenzenesulfonamide (2-NBSA) was carried out. Quantum chemical calculations showed that 2-NBSA has four
conformers, two of which are stabilized by intramolecular hydrogen bond. The latter (with the S–N bond in a close to orthogonal
position around the phenyl ring and differing from each other by staggered or eclipsed positions of the N–H and S=O bonds
in the SO2NH2 group) presented in a saturated vapor over 2-NBSA at T = 433 (3) K in commensurable amounts. Experimental internuclear distances (Ǻ) for the staggered conformer are (?): r
h1(C–H)av. = 1.071(9), r
h1(C–C)av. = 1.390(4), r
h1(C–S) = 1.789(8), r
h1(S=O)av. = 1.427(6), r
h1(S–N) = 1.644(6), r
h1(N–O)av. = 1.221(4), r
h1(C′–N) = 1.487(8), r
h1(N–H)av. = 1.014. Calculations at B3LYP/cc-pvtz level were performed to determine the structure and the energies of the transition
states between conformers. It was shown that the conformer structures of free molecule differ from those of a molecule stabilized
by intermolecular hydrogen bonds in a crystal. Influence of a substituent X (X = –CH3, –NO2) on conformational features of the ortho-substituted benzenesulfonamide was established. 相似文献
9.
Nina I. Giricheva Georgiy V. Girichev Yulia S. Medvedeva Sergey N. Ivanov Vyacheslav M. Petrov 《Structural chemistry》2012,23(3):895-903
A combined gas-phase electron diffraction and quantum chemical (B3LYP/cc-pVTZ, MP2/cc-pVDZ) study of molecular structure of
2,4,6-trinitrobenzenesulfonic acid (2,4,6-tri-NBSA) was carried out. Quantum chemical calculations showed that 2,4,6-tri-NBSA
possesses six conformers, which form three pairs of enantiomers with the relative energy of 0, 4.4/3.9, and 2.5/2.5 kcal/mol.
It was experimentally established that at T = 444(5) K a saturated vapor over 2,4,6-tri-NBSA is, predominantly (up to 93 mol.%), represented by a low-energy enantiomers
II and II′ characterized by intramolecular hydrogen bond between an H atom of the hydroxyl group and one of the O atoms of
the NO2 group. Experimental internuclear distances for the low-energy enantiomers are (?): r
h1(C–C)av. = 1.387(4), r
h1(C–S) = 1.811(6), r
h1(S=O)av. = 1.424(4), r
h1(S–O) = 1.579(4), r
h1(N–O)av. = 1.214(3), r
h1(C–N)av. = 1.491(5). Geometry of the conformer II points on existance of strong steric interactions between SO2OH group and two ortho-nitro groups. Analysis of the orbital interactions between the substituents and benzene ring was carried out. Geometric parameters
and energies of transition states between conformers were calculated (B3LYP). 相似文献
10.
K. Ramalingam R. Thiruneelakandan G. Bocelli L. Righi 《Transition Metal Chemistry》2012,37(3):265-270
The complexes trans-[Ni(4-MP)2(NCS)2]·MeCN (1) and trans-[Ni(3-MP)2(NCS)2] (2) (4-MP = tri(4-methylphenyl)phosphine, 3-MP = tri(3-methylphenyl)phosphine) were prepared and characterized by IR, UV–visible,
NMR spectra, CV, TGA and single crystal X-ray crystallography. Both the complexes have planar geometry and are diamagnetic.
The Ni–P distances in both complexes are relatively short as a result of strong back donation from nickel to phosphorus. The
phenyl rings in the 3-MP analogue (2) show increased pitching with reference to the plane formed by the ipso carbons due to increased steric effects. For complex
(2), the N–Ni–N and P–Ni–P angles are significantly lower than the almost linear N–Ni–N and N–Ni–P angles observed for both
complex (1) and trans-[Ni(PPh3)2(NCS)2]. This observation indicates that the 3-methylphosphine ligand forces complex (2) to distort towards a tetrahedral geometry. IR spectra of both complexes show strong bands around 2,090 cm−1 due to N-coordinated thiocyanate, while the electronic spectra contain d–d transitions around 452 nm. Cyclic voltammograms
show that the irreversible one-electron reduction potentials increase in the following order: trans- [Ni(PPh3)2(NCS)2] < trans- [Ni(3-MP)2(NCS)2] < trans-[Ni(4-MP)2(NCS)2], revealing the electron releasing effect of the methyl groups. The planar complexes exhibit interallogony in coordinating
solvents. 相似文献
11.
Pet'kov V. I. Orlova A. I. Kazantsev G. N. Samoilov S. G. Spiridonova M. L. 《Journal of Thermal Analysis and Calorimetry》2001,66(2):623-632
A5–4xZrxZr(PO4)3 (A=Na, K;0≤x≤1.25), Na1-xCd0.5xZr2(PO4)3 (0≤x≤1), Na5–xCd0.5xZr(PO4)3 (0≤x≤4) compositions which belong to the NZP structural family were synthesized using the sol-gel method. The lattice thermal
expansion of members of these rows were determined up to 600°C by high-temperature X-ray diffractometry. The axial thermal
expansion coefficients change from -5.8·10-6to 7.5·10-6 °C-1 (αa) and from 2.6·10–6 to 22·10–6 °C-1 (αc). These results, in addition to those for other NZP compounds allow us to explain their low thermal expansion. The mechanism
can be attributed to strongly bonded three-dimensional network structure, the existence of structural holes capable to damp
some of the thermal vibrations and anisotropyin the thermal expansion of the lattice.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
12.
The ground state and some lowest excited states of ozone are calculated by the semiempirical MNDO method using configuration
interaction to explain the Wulf absorption band and photodissociation of ozone. The results of calculations show that3A2(13A′’) is the lowest excited triplet state of O3; a transition to this state from the ground X1 A1 state is responsible for the weak Wulf absorption. The oscillator strength (f = 3.2·10-7) and the radiative lifetime of the A2 state (Τ = 0.01 s) are in agreement with recent ab initio calculations.
Translated fromZhumal Struktumoi Khimii, Vol. 38, No. 6, pp. 1067–1073, November–December, 1997. 相似文献
13.
Abstract The molecular and crystal structure of a 1:1 co-crystal of 4,4′-dimethyl-7,7′-bi([1,2,5]thiadiazolo[3,4-b]pyridylidene)–chloranilic acid, (1), has been determined by X-ray diffraction at the monoclinic space group P21/c with cell parameters of a = 8.422(6), b = 7.343(4), c = 16.112(7) ?, β = 104.988(8)°, V = 962.5(10) ?3 and Z = 2. In the crystal structure, two components connect via the intermolecular O–H···N hydrogen bonds [2.804(4) ?] and S···O
heteroatom interaction [2.945(3) ?] with R
2
2(7) couplings to form a unique and infinite one-dimensional supramolecular tape structure. The calculations of (1) at the HF/6-31G(d), MP2/6-31G(d), and B3LYP/6-31G(d) levels can almost reproduce X-ray geometry. In addition, the distances
of the intermolecular O–H···N and S···O interactions by MP2/6-31G(d) and B3LYP/6-31G(d) levels agree well with those in the
crystal. The calculated binding energies corrected BSSE and ZPE are −4.487 (HF), −7.473 (MP2), and −5.640 (B3LYP) kcal/mol.
The results suggest that the complex (1) is very stable and the dispersion interaction is significantly important for the attractive intermolecular interaction in
(1). The NBO analysis has revealed that the n(N) → σ*(O–H) interaction gives the strongest stabilization to the system and the major interaction for the intermolecular
S···O contact is n(O) → σ*(S–N).
Index Abstract In the crystal structure of the title compound, the molecules are linked by intermolecular O–H···N hydrogen bonds and short
S···O heteroatom interactions with R
2
2(7) couplings to construct a unique and infinite one-dimensional supramolecular tape structure.
相似文献
14.
Alkali phosphomolybdate glasses have been prepared by quenching melted mixtures of P2O5, MoO3 and A2O(A=Li, Na). The composition dependence of the transition temperature of glasses belonging to ternary A2O–(MoO3)2–P2O5 (A=Li, Na) systems is studied for several series of glasses corresponding to either a fixed A2O rate or a constant Mo/P ratio. The interpretation of the results is based on the presence of different types of molybdenum
and phosphorous structural groups and P–O–M (M=P, Mo) linkages in glasses.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
15.
S. S. Kim M. H. Baik K. C. Kang 《Journal of Radioanalytical and Nuclear Chemistry》2009,281(3):577-583
The solubilities of NpO2(s) in the KURT (KAERI Underground Research Tunnel) granitic groundwater with low ionic strength were measured experimentally
and calculated by a geochemical code. Then these results were compared with each other as well as with foreign results. The
concentrations of neptunium were measured as 6·10−8−2·10−8 mol/L at a pH = 9.5–11.1 and Eh = −0.2 V, and less than 5·10−9 mol/L at a pH = 11.8–13.0 and Eh = −0.3–0.44 V. The dominant aqueous species were presumed as Np(OH)x(CO3)y
4−x−2y complexes and Np(OH)4(aq) at pH = 9.5–13 under the Eh<−0.2 V reducing condition. 相似文献
16.
Zhang J.-J. Wang R.-F. Li J.-B. Liu H.-M. Yang H.-F. 《Journal of Thermal Analysis and Calorimetry》2000,62(3):747-755
The thermal decomposition of Eu2(BA)6(bipy)2 (BA=C2H5N–
2, benzoate; bipy=C10H8N2, 2,2'-bipyridine)and its kinetics were studied under the non-isothermal condition by TG-DTG, IR and SEM methods. The kinetic
parameters were obtained from analysis of the TG-DTG curves by the Achar method, the Madhusudanan-Krishnan-Ninan (MKN) method,
the Ozawa method and the Kissinger method. The most probable mechanism function was suggested by comparing the kinetic parameters.
The kinetic equation for the first stage can be expressed as: dα/dt=Aexp(–E/RT)3(1–α)2/3.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
17.
Viscosity B-coefficients for cesium chloride and lithium sulfate in methanol + water mixtures at 25 and 35 °C are reported. A general
treatment of the quasi-thermodynamics of viscous flow of electrolyte solutions is described. ΔG
3
Θ
(1→1′), the contribution made to the Gibbs energy of activation of the solution by the influence of the solute on the solvent,
is a function of solute–solvent interactions only; but, ΔH
3
Θ
(1→1′) and ΔS
3
Θ
(1→1′) also reflect the solvent–solvent interactions. In aqueous solution all alkali-metal ions except Li+ are sterically unsaturated, having solvent co-ordination numbers n<n
max , the maximum allowed sterically. Such complexes exchange molecules with the solvent more readily than saturated ones and
have energy–reaction co-ordinate diagrams in forms that explain the negative B or ΔG
3
Θ
(1→1′) values found in aqueous solution. Saturated complexes are the norm in non-aqueous solvents, and the ΔG
3
Θ
(1→1′) values are determined mainly by the secondary solvation. Behavior in mixed solvents reflects the transition from aqueous
to non-aqueous behavior across the range of solvent composition. 相似文献
18.
Hong-Liang Xu Shi-Ling Sun Shabbir Muhammad Zhong-Min Su 《Theoretical chemistry accounts》2011,128(2):241-248
Significant alkali-metal-doped effects on the structure and the first hyperpolarizability (β
0) of effective multi-nitrogen complexant tris[(2-imidazolyl)methyl]amine (TIMA) are investigated. Three imidazoles of TIMA
like three blades of propeller connect with methyls by the C–C single bonds. Because of the three C–C single-bond cooperative
rotations, the TIMA behaves with great flexibility, and it is a high-performance multi-nitrogen complexant for the alkali
metal doping. Thus, the new complexes Am-TIMA (Am = Li, Na, and K) with electride characteristic have diffuse excess electron than the reported electride-type system due to
the strong interaction between the complexant TIMA and alkali metal. For the first hyperpolarizability, three engaging electrides
Am-TIMA with the diffuse excess electrons exhibit considerably large β
0 values using the MP2 (full) method and the β
0 values of new electrides are greatly larger (3,464–29,705 times) than that (338 au) of TIMA. Surprisingly, the K-TIMA sets
a new record β
0 value to be 1.00 × 107 au which far exceeds than that (3,694–76,978 au) of the reported electride-type system Li@calix[4]pyrrole (J Am Chem Soc
127:10977–10981, 2005) and Lin−H−(CF2−CH2)3−H (n = 1, 2) (J Am Chem Soc 129:2967–2970, 2007) and 31,123 au of the organometallic system (J Am Chem Soc 121:4047–4053, 1999) Ru(trans-4,4′-diethylaminostyryl-2,2′-bipyridine)32+, as well as 1.23 × 106 au of the large donor-CNT systems (Nano Lett 8:2814–2818, 2008). Clearly, the alkali-metal-doped effect on the first hyperpolarizability is very dramatic for the high-performance multi-nitrogen
complexant TIMA. Considering simple possibility from molecule to material, the β
0 values of optimized Li-TIMA-dimer and Li-TIMA-tetramer are investigated by BHandHLYP method. Interestingly, results show
that the order of β
0 value is Li-TIMA-monomer < Li-TIMA-dimer < Li-TIMA-tetramer. So the new three-propeller-blade-shaped electrides can be considered
as candidates for high-performance nonlinear optical materials. 相似文献
19.
Dagmara Jacewicz Agnieszka Łapińska Aleksandra Dąbrowska Lech Chmurzyński 《Transition Metal Chemistry》2006,31(1):111-117
The kinetics of the reaction between gaseous CO2 and the cis-[Cr(phen)2(OH2)2]3+ ion leading to the formation of the carbonato complex ion, have been studied over the pH and temperature ranges: 3 < pH <
6 and 5 < T < 25 °C, respectively, at a constant ionic strength of 1 m (NaClO4). Investigations were carried out using the stopped-flow spectrophotometry technique in the UV–Vis range: 340–700 nm. The
major reactant species in the pH range studied was cis-[Cr(phen)2(OH)(OH2)]2+ ion, which underwent reaction with CO2 to form cis-[Cr(phen)2(OH2)(HCO3)]2+ ion. Subsequently, slower ring closure of the latter species to form the bidentate carbonato chelate was observed. The possible
mechanism has been discussed and the activation parameters ΔH† and ΔS† were also determined for the reaction studied. 相似文献
20.
P. Ganguly 《Journal of Chemical Sciences》2001,113(5-6):415-425
The prominent “1/3” effect observed in the Hall effect plateaus of two-dimensional electron gas (2DEG) systems has been postulated
to indicating 1/3 fractional charge quasiparticle excitations arising from electron-electron interactions. Tunneling shot-noise
experiments on 2DEF exhibiting fractional quantum Hall effect (FQHE) shows evidence for tunnelling of particles with eand
e/3 charges for a constant band mass. A “1/3” effect in the hydrogen molecule is seen in as much as its internuclear distance,d
H-H
= D− + D+, with |D+/D−| = 1/3. This is examined in terms of electron-electron interactions involving electron-and hole quasiparticles, (e-)and(h
+
), equivalent to those observed in FQHE shot -noise experiments. The(e/m) ratio of the (e−) and(h
+
) quasiparticles is kept at 1: −3. Instead of a 2DEG, these particles are treated as being in flat Bohr orbits. A treatment
in the language of charge-flux tube composites for the hydrogen atom as well as the hydrogen molecule is attempted. Such treatment
gives important insights into changes in chemical potential and bond energy on crossing a phase boundary during the atom-bond
transition as well as on models for FQHE itself. 相似文献