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91.
92.
Harry Biron Christiane Grller-Walrand Stephan De Jaegere 《Chemical physics letters》1973,20(6):581-585
A quantitative comparison between the excitation and absorption spectra of Eu3+ in aqueous solution is given which leads to the conclusion that fluorescence quantum yields are independent of the excitation wavelength. Use is made therefore of the series of homologous lines 5D3, 5D2, 5D1, 5D0 → 7F1. 相似文献
93.
Gerald Koitz Walter Fabian Hans-Werner Schmidt Hans Junek 《Monatshefte für Chemie / Chemical Monthly》1981,112(8-9):973-985
The synthesis of several 2-aminopyridines is described. The reaction of tetracyanoethylene with 3-imino-propane-carbonitrile gives 2-amino-3,4,5-tricyano-pyridines with alkyl and aryl-substituents, resp., in position 6. Nucleophilic substitution of 2-amino-6-chloro-3,5-dicyanopyridines and 2-amino-6-chloro-3,4,5-tricyano-pyridines with phenolates leads to a variety of pyridines. Spectroscopical data of absorption and fluorescence are presented and the influence of the cyano groups is discussed. The results are in good agreement with quantum chemical calculations (PPP).
Herrn Univ-Prof. Dr.A. Holasek zum 60. Geburtstag gewidmet. 相似文献
94.
95.
96.
Wolfgang M. Schmidt 《Monatshefte für Mathematik》1986,102(1):27-58
Very general hypersurfaces in 4 contain r
2+(4/9) integer points in any ball of radiusr>1. As a consequence, an irreducible algebraic hypersurface in
n
(wheren4) which is not a cylinder and is of degreed, contains c(d, n)r
n–1–(5/9) integer points in a ball of radiusr. This improves on the known boundc(d, n)r
n–(3/2).Meinem verehrten Lehrer Professor E. Hlawka zum siebzigsten Geburtstag gewidmetWritten with partial support from NSF-MCS-8211461. 相似文献
97.
98.
The static dipole polarizabilities,
D
, have been studied for the ions O2–, F–, Na+, Mg2+, Cl–, K+ and Ca2+ in the crystals NaF, KF, NaCl, KC1, MgO and CaO. The starting zero-order wave functions have been generated using various exchange- and exchange-correlation potentials in order to study the effect of these potentials on
D
. The direct contribution to the dipole polarizability,
o
D
, has been determined by the uncoupled Hartree-Fock method. Self-consistency effects have been included by the geometric approximation. The crystal potential is incorporated using the Watson sphere model. Good agreement between theoretical and experimental results are found for those self-consistent potentials which exclude self-interaction. 相似文献
99.
Single-molecule studies that allow to compute pKa values, proton affinities (gas-phase acidity/basicity) and the electrostatic energy of solvation have been performed for a heterogeneous set of 26 organic compounds. Quantum mechanical density functional theory (DFT) using the Becke-half&half and B3LYP functionals on optimized molecular geometries have been carried out to investigate the energetics of gas-phase protonation. The electrostatic contribution to the solvation energies of protonated and deprotonated compounds were calculated by solving the Poisson equation using atomic charges generated by fitting the electrostatic potential derived from the molecular wave functions in vacuum. The combination of gas-phase and electrostatic solvation energies by means of the thermodynamic cycle enabled us to compute pKa values for the 26 compounds, which cover six distinct chemical groups (carboxylic acids, benzoic acids, phenols, imides, pyridines and imidazoles). The computational procedure for determining pKa values is accurate and transferable with a root-mean-square deviation of 0.53 and 0.57 pKa units and a maximum error of 1.0 pKa and 1.3 pKa units for Becke-half&half and B3LYP DFT functionals, respectively. 相似文献
100.
D. L. Schmidt H. B. Smith M. Yoshimine M. J. Hatch 《Journal of polymer science. Part A, Polymer chemistry》1972,10(10):2951-2966
A new class of zwitterionic monomers were prepared in which the positive and negative sites are cyclic sulfonium and phenolate. Thermal polymerization occurs by phenolic anionic attack upon the aliphatic carbon α to the sulfonium sulfur. Polymerization proceeds with ring opening and net loss of charge to form nonionic polymers. The monomeric zwitterions are generally hydrated, crystalline solids that are soluble in water or alcohol. Chlorination of the aromatic portion of the molecule yields nonhydrated species. The polymerizations of 1-(4-hydroxy-3-methylphenyl)tetrahydrothiophenium hydroxide inner salt (dihydrate) and 1-(3,5-dichloro-4-hydroxyphenyl)tetrahydrothiophenium hydroxide inner salt were studied. The latter monomer gave a polymer with M?n of 46,000 when a nucleophile was present as an initiator. The physical properties of this polymer were determined. Cyclization appears to be the main mechanism of termination in the polymerization of zwitterions. 相似文献