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1.
F. Rubio F. García H. D. Burrows A. A. C. C. Pais A. J. M. Valente M. J. Tapia J. M. García 《Journal of polymer science. Part A, Polymer chemistry》2007,45(9):1788-1799
The interaction between trivalent lanthanide ions and poly(1,4,7,10,13‐pentaoxacyclopentadecan‐2‐yl‐methyl methacrylate), PCR5, in aqueous solution and in the solid state have been studied. In aqueous solution, evidence of a weak interaction between the lanthanides and PCR5 comes from the small red shift of the Ce(III) emission spectra and the slight broadening of the Gd(III) EPR spectra. From the Tb(III) lifetimes in the presence of H2O and D2O the loss of one or two water coordinated molecules is confirmed when Tb(III) is bound to PCR5. An association constant of the order of 200 M?1 was obtained for a 1:1 (lanthanide:15‐crown‐5) complex from the shift of the polymer NMR signals induced by Tb(III). A similar association constant is obtained from the differences of the molar conductivity of Ce(III) solution at various concentrations in presence and absence of PCR5. When Tb(III) is adsorbed on PCR5 membranes, lifetime experiments in H2O and D2O confirm the loss of 5 or 6 water coordinated molecules indicating that in solid state the lanthanide(III)‐PCR5 interaction is stronger than in solution. The adsorption of Ce(III) in PCR5 membranes shows a Langmuir type isotherm, from which an equilibrium constant of 39 M?1 has been calculated. SEM shows that the membrane morphology is not much affected by lanthanide adsorption. Support for lanthanide ion–crown interactions comes from ab initio calculations on 15‐crown‐5/La(III) complex. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1788–1799, 2007 相似文献
2.
The oxidative cleavage of several hydroquinones dimethylethers with nitric acid- impregnated manganese dioxide, in methylene chloride solution at room temperature, gave the corresponding quinones in 76–95% yield. 相似文献
3.
In this paper an application of a reaction field theory of solvent effects has been made to study proton transfer mechanisms in hydrogen bonded systems coupled to an environment. The latter is simulated with reaction fields having variable strength and direction (defined with respect to the supermolecule's total dipole moment direction), together with superposed uniform external electric fields. Changes in proton potential curves and some other properties of a model water dimer and a water trimer are reported. The results are discussed in relation to relevant phenomena in biology and biochemistry, namely proton relay systems in enzymatic catalysis. 相似文献
4.
Dihydronaphthopyran-5,10-diones 7,13, 16 and their corresponding dihydronaphthopyran-5,6-diones 8, 14,17 have been obtained starting from Michael adducts of 2-hydroxy- and 2-hydroxy-7-methoxy-1,4-naph-thoquinone ( 1, 9 ). An efficient synthesis of hydroxyhydrolapachol ( 4 ) employing 2-hydroxy-3-(3-oxobutyl)-1,4-naphthoquinone ( 5 ) is described. 相似文献
5.
A simple electrostatic analysis is given of the virtual charge (solvaton) model to represent the environment effect on the electronic wave function of a solute immersed in a polarizable surrounding. New features of this model are found. The classical aspects are discussed and secondly the quantal implications are considered. A correct Hartree-Fock-like operator is derived which represents an electron in a molecular orbital subjected to the average effect of the other electrons and to the reaction field produced by the virtual charges on the atomic centers.A general formalism based on the preceding model is presented in appendix. The final equations have a form similar to Newton's equation to represent a solvated electron. Unlike some other theories in this field, there is no cut-off involved in the evaluation of the molecular integrals. 相似文献
6.
Recently, Ye, Tapia and Zhang (1991) demonstrated that Mizuno—Todd—Ye's predictor—corrector interior-point algorithm for linear programming maintains the O(
L)-iteration complexity while exhibiting superlinear convergence of the duality gap to zero under the assumption that the iteration sequence converges, and quadratic convergence of the duality gap to zero under the assumption of nondegeneracy. In this paper we establish the quadratic convergence result without any assumption concerning the convergence of the iteration sequence or nondegeneracy. This surprising result, to our knowledge, is the first instance of a demonstration of polynomiality and superlinear (or quadratic) convergence for an interior-point algorithm which does not assume the convergence of the iteration sequence or nondegeneracy.Supported in part by NSF Grant DDM-8922636 and NSF Coop. Agr. No. CCR-8809615, the Iowa Business School Summer Grant, and the Interdisciplinary Research Grant of the University of Iowa Center for Advanced Studies.Supported in part by NSF Coop. Agr. No. CCR-8809615, AFOSR 89-0363, DOE DEFG05-86ER25017 and ARO 9DAAL03-90-G-0093.Supported in part by NSF Grant DMS-9102761 and DOE Grant DE-FG05-91ER25100. 相似文献
7.
An ab-initio gaussian lobe function study of the structure and some molecular properties of the HPO molecule is reported. By a partial optimization of the geometrical structure the following equilibrium structure parameters are found: rPO = 1.536 Å; rPH = 1.475 Å; the bond angle is found to be close to 102° with a bending force constant of 0.58 mdyne/Å. The dipole moment, effective charges and quadrupole term components at various bond angles are reported. The wavefunction of the equilibrium geometry is available from the authors upon request. 相似文献
8.
Second order perturbation theory (SOP) has been used to introduce electronic correlation effects on CNDP/2 calculated quantities like stabilization energy, proton potential curves, intermolecular dependence on distance and orientation. The HCHO…H2O' model has been studied. The SOP energy as a function of the RO…O' distance introduces changes in the potential minima which amount to 14% of the CNDO/2 value and in the asymmetry of the potential energy curve. For the proton curve, an extra stabilization energy of 4 kcal/mole at the minimum is found as well as changes in the shape of the potential curve. Effects on orientation dependence are also reported. 相似文献
9.
A quantum-mechanical reaction field theory of solvent effects is proposed. It contains as a limiting case Onsager's model. It leads to an effective, non-linear, hamiltonian for the molecule in solution and hence to a tool for studying changes in charge distributions and molecular properties. Numerical examples are given. 相似文献
10.
Lucía Tapia Yolanda Prez Michael Bolte Josefina Casas Jordi Sol Roberto Quesada Ignacio Alfonso 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(36):12595-12598
Acidic microenvironments in solid tumors are a hallmark of cancer. Inspired by that, we designed a family of pseudopeptidic cage‐like anionophores displaying pH‐dependent activity. When protonated, they efficiently bind chloride anions. They also transport chloride through lipid bilayers, with their anionophoric properties improving at acidic pH, suggesting an H+/Cl? symport mechanism. NMR studies in DPC micelles demonstrate that the cages bind chloride within the lipid phase. The chloride affinity and the chloride‐exchange rate with the aqueous bulk solution are improved when the pH is lowered. This increases cytotoxicity towards lung adenocarcinoma cells at the pH of the microenvironment of a solid tumor. These properties depend on the nature of the amino‐acid side chains of the cages, which modulate their lipophilicity and interactions with the cell membrane. This paves the way towards using pH as a parameter to control the selectivity of cytotoxic ionophores as anticancer drugs. 相似文献