[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Recent research advances on conjugated polymers for photovoltaic devices have focused on creating low band gap materials, but a suitable band gap is only one of many performance criteria required for a successful conjugated polymer. This work focuses on the design of two medium band gap (∼2.0 eV) copolymers for use in photovoltaic cells which are designed to possess a high hole mobility and low highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels. The resulting fluorinated polymer PBnDT−FTAZ exhibits efficiencies above 7% when blended with [6,6]-phenyl C61-butyric acid methyl ester in a typical bulk heterojunction, and efficiencies above 6% are still maintained at an active layer thicknesses of 1 μm. PBnDT−FTAZ outperforms poly(3-hexylthiophene), the current medium band gap polymer of choice, and thus is a viable candidate for use in highly efficient tandem cells. PBnDT−FTAZ also highlights other performance criteria which contribute to high photovoltaic efficiency, bes...

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Fluorine Substituted Conjugated Polymer of Medium Band Gap Yields 7% Efficiency in Polymer-Fullerene Solar Cells

Organic chemists have always been fascinated by the cyclopropane subunit.1 The smallest cycloalkane is found as a basic structural element in a wide range of naturally occurring compounds.2 Moreover, many cyclopropane-containing unnatural products have been prepared to test the bonding features of this class of highly strained cycloalkanes3 and to study enzyme mechanism or inhibition.4 Cyclopropanes have also been used as versatile synthetic intermediates in the synthesis of more functionalized cycloalkanes5,6 and acyclic compounds.7 In recent years, most of the synthetic efforts have focused on the enantioselective synthesis of cyclopropanes.8 This has remained a challenge ever since it was found that the members of the pyrethroid class of compounds were effective insecticides.9 New and more efficient methods for the preparation of these entities in enantiomerically pure form are still evolving, and this review will focus mainly on the new methods that have appeared in the literature since 1989. It will elaborate on only three types of stereoselective cyclopropanation reactions from olefins: the halomethylmetal-mediated cyclopropanation reactions (eq 1), the transition metal-catalyzed decomposition of diazo compounds (eq 2), and the nucleophilic addition-ring closure sequence (eqs 3 and 4). These three processes will be examined in the context of diastereoand enantiocontrol. In the last section of the review, other methods commonly used to make chiral, nonracemic cyclopropanes will be briefly outlined.

Stereoselective Cyclopropanation Reactions

Recent Advances in Asymmetric Catalytic Metal Carbene Transformations.

Vacuum pyrolysis of 5-silaspiro[4.4]nona-2,7-diene (5a), UV irradiation of silacyclopent-3-ene (6), and vacuum pyrolysis of 6 resulted in the formation of 1-silacyclopenta-2,4-diene (1a) characterized by its IR and UV-vis spectra. The 3,4-dimethyl analogue 1b was generated by vacuum pyrolysis of 5b, the 2,3,7,8-tetramethyl derivative of 5a. Photoreversible interconversion of 1a with 1-silacyclopent-3-ene-1,1-diyl (2a) 1-silacyclopenta-1,3-diene (3a), and 1-silacyclopenta-1,4-diene (4a) and the analogous interconversion of 1b with 3,4- dimethyl-1-silacyclopent-3-ene-1,1-diyl (2b), 3,4-dimethyl-1-silacyclopenta-1,3-diene (3b), and 1,3-dimethyl-1-sila cyclopenta-1,4-diene (4b) have been observed upon irradiation at selected wavelengths

Matrix isolation of silacyclopentadienes: UV-visible and IR spectra and photochemical interconversion

Room temperature observation of geh2 and the first time-resolved study of some of its reactions

This review deals with inorganic, organometallic, and organic compounds, as well as with elements, that on the basis of their electronic structure and their reactions can be regarded formally as analogues of carbenes. These “carbene analogues” include in particular the compounds of monovalent boron, aluminum, nitrogen, and phosphorus; those of divalent silicon, germanium, tin, and lead; atomic oxygen; atomic sulfur; and atomic selenium. The preparation and chemical properties of the carbenes and their analogues are compared.

Inorganic, Organometallic, and Organic Analogues of Carbenes

Recently, the molecular structures of germanium dichloride and germanium dibromide have been communicated. On the basis of available experimental structural data, the geometries for several other carbene analogues have been predicted, among them silicon dichloride and silicon dibromide. Here the molecular structures of these two molecules are reported.

Oleg M. Nefedov

Papers

Matrix isolation of silacyclopentadienes: UV-visible and IR spectra and photochemical interconversion

Room temperature observation of geh2 and the first time-resolved study of some of its reactions

Inorganic, Organometallic, and Organic Analogues of Carbenes

Molecular structure of silicon dichloride and silicon dibromide from electron diffraction combined with mass spectrometry

Germylene and Stannylene Anion-Radicals: Generation and Electronic Structure