Molecular second-order measurements

In this study we have described theoretical calculations, syntheses, optical spectra, ground-state dipole moment measurements, and measurements of molecular second-order hyperpolarizability coefficients (/J) for new stilbene and azobenzene derivatives containing a methylsulfonyl group as the electron acceptor. We have shown that theoretical calculations can be used to predict the ratio of molecular hyperpolarizabilities between similar compounds, and that these gas phase calculations underestimate /J, probably as a result of the valence basis set used in the calculations. 

A-priori, given that FLC phases possess polar order, and the DOBAMBC structure should possess a substantial molecular second order hyperpolarizability P, it seems reasonable that %(2) of a material such as DOBAMBC in the FLC phase might be large. Measured values of the second harmonic generation efficiencies of DOBAMBC and of several other FLC materials, however, indicate that in fact the dcff of FLCs is very small relative to LiNb03. 

Table 6. Molecular second-order NLO results for ruthenium alkynyl and vinylidene complexes measured at two wavelengths ...

K. D. Singer, A. F. Garito, Measurements of molecular second order optical susceptibihties using dc induced... 

In the majority of reports, researchers have employed the EFISH or HRS teeh-niques to measure molecular second-order nonlinearities of organometallies. The earliest studies in this field were of metal carbonyl-derived complexes, but sinee these reports, the majority of the measurements have been of metallocenyl, metal alkynyl or related complexes, which can be synthesized in high yield by... 

Singer, K.D. and Garito, A.F. (1981) Measurements of molecular second order optical susceptibilities using dc induced second harmonic generation. 

As the medium is still further diluted, until nitronium ion is not detectable, the second-order rate coefficient decreases by a factor of about 10 for each decrease of 10% in the concentration of the sulphuric acid (figs. 2.1, 2.3, 2.4). The active electrophile under these conditions is not molecular nitric acid because the variation in the rate is not similar to the correspondii chaise in the concentration of this species, determined by ultraviolet spectroscopy or measurements of the vapour pressure. " ... 

Chemoinformatics (or cheminformatics) deals with the storage, retrieval, and analysis of chemical and biological data. Specifically, it involves the development and application of software systems for the management of combinatorial chemical projects, rational design of chemical libraries, and analysis of the obtained chemical and biological data. The major research topics of chemoinformatics involve QSAR and diversity analysis. The researchers should address several important issues. First, chemical structures should be characterized by calculable molecular descriptors that provide quantitative representation of chemical structures. Second, special measures should be developed on the basis of these descriptors in order to quantify structural similarities between pairs of molecules. Finally, adequate computational methods should be established for the efficient sampling of the huge combinatorial structural space of chemical libraries. 

Despite the relative simplicity of the kinetics of molecular chlorination, there has so far been only one measurement of the rate coefficient with a heterocyclic compound and the need for more work in this area is indicated. Marino265 found that chlorination of thiophene by chlorine in acetic acid at 25 °C gave the second-order rate coefficient of 10.0 1.5, so that thiophene is 1.7 x 109 times as reactive as benzene in this reaction and this large rate spread is clearly consistent with the neutral and hence relatively unreactive electrophile. 

It is seen that the result obtained is sensitive to both the molecular symmetry and the strength of collision y, which is a quantitative measure of the degree of correlation. However, the latter affects only correction to the Hubbard relation which appears in the second order in (t))2 linear dependence of product on (L/)2 for any y, but the slope of the lines differs by a factor of two, being minimal for y=l and maximal for y=0. In principle, it is possible to calculate corrections of the higher orders in (t))2 and introduce them into (2.91). In practice, however, this does not extend the application range of the results due to a poor convergence of the perturbation theory series. 

An important goal of this study is to characterize the noncentrosymmetric arrangement of the azobenzene branches in dendrimers and the effect of these dendrimers on macroscopic second-order susceptibihty. The NLO activity of the dendrimers can be characterized by their molecular hyperpolarizabihty. The hyper-Rayleigh scattering (HRS) method is a reliable way of measuring the mol-... 

Using the alternating deposition of the amphiphiles with a carboxyl substituent and arachidic add, noncentrosymmetric LB films (hetero Y-type) were prepared, and molecular orientation and second-order optical nonlinearity in the LB films were evaluated with the linear dichroism [4] and the second-harmonic generation (SHG) measurements, respectively. The SHG measurement procedure is mentioned in the section 1.3. 

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