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1.
Zeus A. De los Santos Sean MacAvaney Katina Russell Christian Wolf 《Angewandte Chemie (International ed. in English)》2020,59(6):2440-2448
We have developed an optical method for accurate concentration, er, and dr analysis of amino alcohols based on a simple mix‐and‐measure workflow that is fully adaptable to multiwell plate technology and microscale analysis. The conversion of the four aminoindanol stereoisomers with salicylaldehyde to the corresponding Schiff base allows analysis of the dr based on a change in the UV maximum at 420 nm that is very different for the homo‐ and heterochiral diastereomers and of the concentration of the sample using a hypsochromic shift of another absorption band around 340 nm that is independent of the analyte stereochemistry. Subsequent in situ formation of CuII assemblies in the absence and presence of base enables quantification of the er values for each diastereomeric pair by CD analysis. Applying a linear programming method and a parameter sweep algorithm, we determined the concentration and relative amounts of each of the four stereoisomers in 20 samples of vastly different stereoisomeric compositions with an averaged absolute percent error of 1.7 %. 相似文献
2.
Daniela Cappello Denis A. B. Therien Prof. Dr. Viktor N. Staroverov Prof. Dr. François Lagugné-Labarthet Prof. Dr. Joe B. Gilroy 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(23):5994-6006
We develop the chemistry of boron difluoride hydrazone dyes (BODIHYs) bearing two aryl substituents and explore their properties. The low-energy absorption bands (λmax=427–464 nm) of these dyes depend on the nature of the N-aryl groups appended to the BODIHY framework. Electron-donating and extended π-conjugated groups cause a redshift, whereas electron-withdrawing groups result in a blueshift. The title compounds were weakly photoluminescent in solution and strongly photoluminescent as thin films (λPL=525–578 nm) with quantum yields of up to 18 % and lifetimes of 1.1–1.7 ns, consistent with the dominant radiative decay through fluorescence. Addition of water to THF solutions of the BODIHYs studied causes molecular aggregation which restricts intramolecular motion and thereby enhances photoluminescence. The observed photoluminescence of BODIHY thin films is likely facilitated by a similar molecular packing effect. Finally, cyclic voltammetry studies confirmed that BODIHY derivatives bearing para-substituted N-aryl groups could be reversibly oxidized (Eox1=0.62–1.02 V vs. Fc/Fc+) to their radical cation forms. Chemical oxidation studies confirmed that para-substituents at the N-aryl groups are required to circumvent radical decomposition pathways. Our findings provide new opportunities and guiding principles for the design of sought-after multifunctional boron difluoride complexes that are photoluminescent in the solid state. 相似文献
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Unprecedented Oxidative Addition and Metal‐Only Lewis Pair Chemistry of Antimony Trihalides 下载免费PDF全文
Prof. Dr. Holger Braunschweig Dr. Rian D. Dewhurst Florian Hupp Dr. Justin Wolf 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(5):1860-1862
Reaction of the zero‐valent platinum complex [Pt(PCy3)2] with SbF3 generates the cationic diplatinum stibenium complex [{(Cy3P)2Pt}2(μ‐SbF2)]+, the first unsupported metal‐only Lewis pair containing an antimony‐centered Lewis acid. In contrast, SbCl3 undergoes oxidative addition to [Pt(PCy3)2], resulting in the dihalostibanyl complex trans‐[PtCl(SbCl2)(PCy3)2], the first example of oxidative addition of an antimony–halide bond to a transition metal. 相似文献
5.
Dr. İlhan Sevim Dr. Wolf Matthias Pankau Prof. Dr. Günter von Kiedrowski 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(41):9032-9035
We re-evaluate our claim of a high diastereoselectivity in the self-relicating Diels–Alder reaction between maleimide 1 and fulvene 3 . It was shown that the system has a diastereoselectivity of 1.8:1 for NN-4 : NX-4 , which is contrary to the 16:1 ratio claimed by Dieckmann et al. The analysis of 1H NMR monitoring of the reaction revealed that both replicators show sigmoidal growth which is typical for auto-catalytic systems. 相似文献
6.
Julia Leitl Dr. Andrew R. Jupp Dr. Evi R. M. Habraken Verena Streitferdt Dr. Peter Coburger Dr. Daniel J. Scott Prof. Dr. Ruth M. Gschwind Prof. Dr. Christian Müller Dr. J. Chris Slootweg Prof. Dr. Robert Wolf 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(35):7788-7800
Salt metathesis of 1-methyl-2,4,6-triphenylphosphacyclohexadienyl lithium and chlorobis(pentafluorophenyl)borane affords a 1-phospha-7-bora-norbornadiene derivative 2 . The C≡N triple bonds of nitriles insert into the P−B bond of 2 with concomitant C−B bond cleavage, whereas the C≡C bonds of phenylacetylenes react with 2 to form λ4-phosphabarrelenes. Even though 2 must formally be regarded as a classical Lewis adduct, the C≡N and C≡C activation processes observed (and the mild conditions under which they occur) are reminiscent of the reactivity of frustrated Lewis pairs. Indeed, NMR and computational studies give insight into the mechanism of the reactions and reveal the labile nature of the phosphorus–boron bond in 2 , which is also suggested by detailed NMR spectroscopic studies on this compound. Nitrile insertion is thus preceded by ring opening of the bicycle of 2 through P−B bond splitting with a low energy barrier. By contrast, the reaction with alkynes involves formation of a reactive zwitterionic methylphosphininium borate intermediate, which readily undergoes alkyne 1,4-addition. 相似文献
7.
Daniela Cappello Dr. Ryan R. Maar Prof. Dr. Viktor N. Staroverov Prof. Dr. Joe B. Gilroy 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(24):5522-5529
The creation of dimeric boron difluoride complexes of chelating N-donor ligands is a proven strategy for the enhancement of the optoelectronic properties of fluorescent dyes. We report dimers based on the boron difluoride hydrazone (BODIHY) framework, which offer unique and sometimes unexpected substituent-dependent absorption, emission, and electrochemical properties. BODIHY dimers have low-energy absorption bands (λmax=421 to 479 nm, ϵ=17 200 to 39 900 m −1 cm−1) that are red-shifted relative to monomeric analogues. THF solutions of these dimers exhibit aggregation-induced emission upon addition of water, with emission enhancement factors ranging from 5 to 18. Thin films of BODIHY dimers are weakly emissive as a result of the inner-filter effect, attributed to intermolecular π-type interactions. BODIHY dimers are redox-active and display two one-electron oxidation and two one-electron reduction waves that strongly depend on the N-aryl substituents. These properties are rationalized using density-functional theory calculations and X-ray crystallography experiments. 相似文献
8.
Ian Drake Gregoire Cardoen Andrew Hughes Kebede Beshah Kenneth L. Kearns Tianlan Zhang John Reffner Casey Wolf Ralph Even 《Journal of polymer science. Part A, Polymer chemistry》2019,57(13):1373-1388
A polyurea macromer (PUM) was synthesized and dispersed in basic conditions to form self‐assembled nanoparticles (<20 nm dispersions, up to 30 wt % aq. soln.). These nanoparticles enabled surfactant‐free emulsion polymerization to form hybrid polyurea‐acrylic particles despite the absence of a measureable water‐soluble fraction. The Tg of the starting PUM material was a strong function of the PUM's extent of neutralization and hydration (varying between 100 °C and >175 °C) due to changes in hydrogen and ionic bonding. Two separate hybrid polyurea‐acrylic emulsion systems were prepared: one by direct polymerization of (meth)acrylic monomers in the presence of the nanodispersion and a second by a physical blend of PUM nanodispersion with an acrylic latex control. The direct polymerization method resulted in a hybrid emulsion particle size that developed by a mechanism resembling conventional emulsion polymerization and was unlike that described for seeded polyurethane dispersion systems. Film hardness was shown to increase with increasing coating thickness for the hybrid film prepared by direct polymerization. The resulting mechanical properties could be explained by applying mechanical models for a composite foam structure. These results were unprecedented for normal elastomer films. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1373–1388 相似文献
9.
Julian P. Edwards William J. Wolf Robert H. Grubbs 《Journal of polymer science. Part A, Polymer chemistry》2019,57(3):228-242
Cyclic polymers have drawn considerable interest for their peculiar physical properties in comparison to linear polymers, despite their equivalent compositions. Synthetically, cyclic polymers can be accessed through either macrocyclic ring‐closure or by ring‐expansion polymerization, but the main challenge with either method is the production of highly pure cyclic polymer samples. This highlight describes advances in the area of cyclic polymer synthesis, with a particular focus on ring‐expansion metathesis polymerization. Methods for characterizing cyclic polymers and assessing their purity are also discussed in order to emphasize the need for additional robust and reliable methods for synthesizing and studying topologically complex macromolecules. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 228–242 相似文献
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