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31.
Prof. Dr. Holger Braunschweig Dr. Rian D. Dewhurst Prof. Dr. J. Oscar C. Jiménez‐Halla Dr. Eduard Matito Jonas H. Muessig 《Angewandte Chemie (International ed. in English)》2018,57(2):412-416
The reaction of tetraiododiborane (B2I4) with trans‐[Pt(BI2)I(PCy3)2] gives rise to the diplatinum(II) complex [{(Cy3P)(I2B)Pt}2(μ2:η3:η3‐B2I4)], which is supported by a bridging diboranyl dianion ligand [B2I4]2?. This complex is the first transition‐metal complex of a diboranyl dianion, as well as the first example of intact coordination of a B2X4 (X=halide) unit of any type to a metal center. 相似文献
32.
Conclusions The authors have synthesized a number of mono-, di-, and tri-substituted 1,3-dioxanes by condensing 1,3-diols, tertiary alcohols, and olefins with aliphatic, aromatic, and heterocyclic aldehydes and ketones in the presence of an electrophilic catalyst, KU-2-8 cation-exchange resin.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2354–2357, October, 1968. 相似文献
33.
Prof. Eduard Donath 《Monatshefte für Chemie / Chemical Monthly》1893,14(1):93-108
Ohne Zusammenfassung 相似文献
34.
Baer M Schreiner E Kohlmeyer A Rousseau R Marx D 《The journal of physical chemistry. B》2006,110(8):3576-3587
The inverse temperature transition (ITT) of a biomimetic model for elastin, capped GVG(VPGVG) in liquid water, is investigated by a comprehensive classical molecular dynamics study. The temperature dependence of the solvation structure and dynamics of the octapeptide are compared using three common force fields, CHARMM, GROMOS, and OPLS. While these force fields differ in quantitative detail, they all predict this octapeptide to undergo a "folding transition" to closed conformations upon heating and a subsequent "unfolding transition" to open conformations at still higher temperatures, thus reproducing the ITT scenario. The peptide kinetics is analyzed within the reactive flux formalism applied to the largest-amplitude mode extracted from principal component analysis, and the solvent's dielectric fluctuations are obtained from the total water dipole autocorrelations. Most importantly, preliminary evidence for an intimate coupling of peptide folding/unfolding dynamics, and thus the ITT, and dielectric relaxation of bulk water is given, possibly being consistent with a "slave mode" picture. 相似文献
35.
Güell M Matito E Luis JM Poater J Solà M 《The journal of physical chemistry. A》2006,110(40):11569-11574
Our research group has recently defined two new aromaticity indexes based on the analysis of electron delocalization in aromatic species using the quantum theory of atoms-in-molecules. One of these indexes is the para-delocalization index (PDI) that measures the electronic delocalization between para-related carbon atoms in six-membered rings. In this paper, we show that this index can be partitioned into individual molecular orbital contributions. We have applied this PDI decomposition to several polycyclic aromatic hydrocarbons showing that this partitioning provides new insight into the origin of aromaticity. 相似文献
36.
Sulfuryl diazide, O(2)S(N(3))(2), previously described as an "exceedingly explosive" compound, has been isolated and characterized by IR (Ar matrix, gas) and Raman (solid) spectroscopy, and its structure has been determined by X-ray crystallography. It has a melting point of -15 °C and can be handled in small quantities in gas, liquid, and solid states. Vibrational spectroscopic studies suggest the presence of only one conformer in both gas and solid states, and the X-ray crystallography revealed an anti conformation of the two azido groups with respect to the NSN plane. Calculations predict the anti (C(2)) conformer to be 6.6 kJ mol(-1) lower in energy than the syn (C(s)) one at the CBS-QB3 level of theory. The related chlorosulfuryl azide, ClSO(2)N(3), has also been prepared and characterized by IR and Raman spectroscopy. 相似文献
37.
Eduard B. BenetskiyCarsten Bolm 《Tetrahedron: Asymmetry》2011,22(3):373-378
Starting from inexpensive materials and following simple protocols various N-phosphorylated sulfoximines and sulfinamides have been synthesized. The newly prepared compounds were then applied as chiral ligands in asymmetric transition metal catalysis. Phosphorus triamide-type ligands derived from (S)-glutamic acid were found to be the most efficient stereoselectors in enantioselective palladium-catalyzed allylic substitutions (up to 97% ee). On the other hand, diamidophosphite-type structures stemming from (S)-proline were the best ligands in rhodium-catalyzed hydrogenation reactions (up to 84% ee). 相似文献
38.
The concepts of conjugation and hyperconjugation play an important role to provide an explanation for several fundamental phenomena observed in organic chemistry. Because these effects cannot be directly measured experimentally, their assessment became a primary concern for chemists from the very beginning. In general, the stabilization produced by both phenomena has been studied by means of isodesmic reactions and energy based analysis such as the energy decomposition analysis. In recent years, electronic delocalization measures have been successfully applied to elucidate the nature of chemical bonding and the aromatic character of all kind of molecules. Because conjugation and hyperconjugation stabilizations are strongly linked to the concept of electron delocalization, this paper will give an account of both effects from the point of view of electronic delocalization measures calculated within the framework of the quantum theory of atoms in molecules. In particular, we focus our attention in the controversial case of the stabilization by conjugation in 1,3-butadiyne and 1,3-butadiene. Unexpectedly, theoretical calculations based on the scheme proposed by Kistiakowsky to quantify the extent of stabilization due to conjugation predicted that the conjugation of 1,3-butadiyne was zero. Subsequent energetic analyses contradicted this observation. These studies pointed out the presence of hyperconjugation stabilization in the hydrogenated product of 1,3-butadiyne and 1,3-butadiene that were used as reference systems in the Kistiakowsky's scheme. Consequently, the extra stabilization of 1-butyne due to hyperconjugation hides the stabilization by conjugation of 1,3-butadiyne. Our results based on electron delocalization measures confirm both the presence of conjugation in 1,3-butadiene and 1,3-butadiyne and hyperconjugation stabilization in their respective hydrogenated products, 1-butene and 1-butyne. 相似文献
39.
40.
Improved Spectral Coverage and Fluorescence Quenching in Donor–acceptor Systems Involving Indolo[3‐2‐b]carbazole and Boron‐dipyrromethene or Diketopyrrolopyrrole 下载免费PDF全文
Adis Khetubol Sven Van Snick Melissa L. Clark Eduard Fron Eduardo Coutiño‐González Arvid Cloet Koen Kennes Yuliar Firdaus Maarten Vlasselaer Volker Leen Wim Dehaen Mark Van der Auweraer 《Photochemistry and photobiology》2015,91(3):637-653
A novel π‐conjugated triad and a polymer incorporating indolo[3,2‐b]‐carbazole (ICZ) and 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) were synthesized via a Sonogashira coupling. Compared to the parent BODIPY the absorption and fluorescence spectrum were for both compounds broader and redshifted. The redshift of the fluorescence and the decrease of the fluorescence quantum yield and decay time upon increasing solvent polarity were attributed to the formation of a partial charge‐transfer state. Upon excitation in the ICZ absorption band the ICZ fluorescence was quenched in both compounds mainly due to energy transfer to the BODIPY moiety. In a similar ICZ–π–DPP polymer (where DPP is diketopyrrolopyrrole), a smaller redshift of the absorption and fluorescence spectra compared to the parent DPP was observed. A less efficient quenching of the ICZ fluorescence in the ICZ–π–DPP polymer could be related to the unfavorable orientation of the transition dipoles of ICZ and DPP. The rate constant for energy transfer was for all compounds an order of magnitude smaller than predicted by Förster theory. While in a solid film of the triad a further redshift of the absorption maximum of nearly 100 nm was observed, no such shift was observed for the ICZ–π–BODIPY polymer. 相似文献