The synthesis of nanomaterials is extremely sensitive to various factors under experimental conditions. Therefore, for controlling synthesis, it is important to ascertain comprehensively the relations between the conditions and nanomaterial properties. This study is intended to acquire the relations in data sets from combinatorial syntheses by means of an artificial neural network-based method toward property optimization. Recently, 3404 data sets were obtained systematically using microreactor-based combinatorial CdSe nanoparticle (NP) syntheses for examining condition–property relations. However, it is time-consuming to acquire the relations for the following reasons: (i) massiveness and complexity of the multivariate data sets, (ii) small numbers of points permitted for each experimental parameter to avoid ‘combination explosion’, and (iii) errors and missing data attributable to experimental reasons. In this work, an NN-based data analysis method was developed and applied for analyzing the data sets to acquire the relations. In the method, an exhaustive 1600 training processes and the following ensemble approach are performed for obtaining preferred NNs. Results show that NNs extract essential patterns on the condition–property relations on a realistic time scale. The trained NNs are capable of predicting the NP properties even for new experimental conditions with high accuracy. Moreover, data interpolation and sensitivity analysis based on the NNs provide us the relations as accessible descriptions such as multidimensional condition–property landscapes and key parameters for controlling the synthesis. Such information can guide us when optimizing the NP properties. Our approach is suitable to extract condition–property relations rapidly from the combinatorial synthesis data and is expected to be effective for various types of target materials, even with unknown properties, because of the flexibility of the NN analysis.

NBO-based CI/MP through-space/bond interaction analysis wasdeveloped to analyze specific orbital interactions under consideration of the effects of electron correlation. This treatment was applied to the analysis of stereoelectronic effects in S N 2 reactions of allyl bromide in which the effects of electron correlation play an important role (ammonia was used as the nucleophilic reagent). The S N 2 activation energy in allyl bromide is lower than that in propyl bromide, because both the -* and -* interactions in allyl bromide contribute equally to the stabilization of the transition state.

The local structure of copper nanoparticles grown in organic solution by reducing Cu(II) hexafluoroacetylacetonate [Cu(hfac)2] was studied as-grown by the Cu K-edge x-ray absorption near-edge structure (XANES). Comparison of the experimental XANES spectra with reference materials indicated small copper clusters are formed by ligand-exchange with oleylamine and subsequent reducing by diphenylsilane. The multiple-scattering (MS) calculation for various model clusters consisting of 13–135 atoms suggests that small (13–19 atom) Cu clusters are stabilized without a large deformation.

Even [n]­cumulenes with an even number n of double bonds are known to have degenerate helical frontier orbitals even in linear-chain structures. Theoretical analysis was conducted to separate one-handed helical orbitals from the others in cumulenes to determine their enantioselective chemical/physical properties. Donor ((NH2)3C−) and acceptor ((NO2)3C−) substituents separate the degenerate energy levels of right- and left-handed helical frontier orbitals in even [n]­cumulenes. Lone pairs (LPs) in the donor group can interact with helical orbitals on the cumulene backbone, leading to “LP–helical orbital” interactions. A difference in the manner of interaction between left- and right-handed orbitals, depending on the LP direction, breaks the mirror symmetry between them. Consequent energy splitting between left- and right-handed orbitals results in extraction of a one-handed helical frontier orbital only. This is the first example of extracting a one-handed helical frontier orbital while maintaining sufficiently large energy splitting in even [n]­cumulene in the framework of C 1 molecular symmetry by donor–acceptor substitutions.

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ABSTRACT:The concept of the stereoelectronic effect has been widely used for the elucidation of organic reaction mechanisms. However, a detailed analysis of this effect has not been developed, especially at the level of the ab initio molecular orbital method. In the present article, the through spacerbond interaction analysis was applied to the stereoelectronic effect at the level of the ab initio molecular orbital method. To obtain a reliable result for the through spacerbond interaction analysis, we introduced a novel procedure to cut off a specific through spacerbond interaction, that is, cutting off a specific integral is performed by increasing the absolute magnitude of the exponent in a Gaussian function. By this procedure, we can easily find a balance in cutting off the nuclear᎐electron attractions, the nuclear᎐nuclear repulsions, and the electron᎐electron repulsions. By using the above-mentioned procedure, we carried out a through spacerbond interaction analysis to the stereoelectronic effect for aminomethanol as a model molecule. As a result, the diagonal terms for the electron transfer play a more important role than do the off-diagonal terms. Since the diagonal term corresponds to the conventional steroelectronic effect, the obtained result is in accordance with the conventional model for the stereoelectronic effect. This result may give a novel insight into the stereoelectronic effect.

Elongation method was applied to determine the electronic structures of B-type poly(dG).poly(dC) DNA at the ab initio molecular orbital level as a first step toward the calculation of aperiodic DNA. The discrepancy in total energy between the elongation method and a conventional calculation was negligibly small in the order of 10(-8) hartreeat. for 14 G-C base pair model. The local density of states for 10 G-C base pair model estimated by the elongation method well reproduced the results by the conventional calculation. It was found that the band gap of the whole system is mainly due to the energy difference between the valence band of guanine and the conduction band of cytosine. Moreover, the electron transfer path through stacking G-C base pairs rather than sugar-phosphate backbones has been confirmed by the authors' calculations.

Wet chemical reduction of metal ions, a common strategy for synthesizing metal nanoparticles, strongly depends on the electric potential of the metal, and its applications to late transition metal clusters have been limited to special cases. Here, we describe copper nanoclusters grown by synchrotron radiolysis in concert with wet chemistry. The local structure of copper aggregates grown by reducing Cu(II) pentanedionate using synchrotron x-ray beam was studied in situ by x-ray absorption spectroscopy. A detailed analysis of the XANES and EXAFS spectra, compared with DFT calculations and full-potential non-muffin-tin multiple scattering calculations, identified the nanocluster as Cu 13 with icosahedral symmetry. The novel ''charged'' nanoclusters tightly bound to electron-donating amido molecules, which formed as a result of photo-induced deprotonation of ligand amines, were stabilized by irradiation. Monodispersive deposition of nanoclusters was enabled by controlling the type and density of ''monomers'', in remarkable contrast to the conventional growth of metallic nanoparticles.