• Epstein Wong opublikował 5 miesięcy, 1 tydzień temu

    The Peruvian stick insect Oreophoetes peruana is the only known animal source for unsubstituted quinoline in nature. When disturbed, these insects discharge a defensive secretion containing quinoline. Analysis of samples obtained from l-[2′,4′,5′,6,’7′-2H5]tryptophan-fed stick insects demonstrated that the insects convert it to [5,6,7,8-2H4]quinoline by removing the 2′-CH moiety in the indole ring of tryptophan. Analogous experiments using l-[1′-15N]tryptophan and l-[1′-15N,15NH2]tryptophan showed that the indole-N atom is retained while the α-amino group is eliminated during the biosynthesis. Mass spectra recorded from quinoline derived from [2-13C1]tryptophan-fed insects indicated that the α-carbon atom of tryptophan is incorporated as the C-2 atom of the quinoline ring.We report an efficient catalytic protocol that chemoselectively reduces nitroarenes to arylamines, by using methylhydrazine as a reducing agent in combination with the easily synthesized and robust catalyst tris(N-heterocyclic thioamidate) Co(III) complex [Co(κS,N-tfmp2S)3], tfmp2S = 4-(trifluoromethyl)-pyrimidine-2-thiolate. A series of arylamines and heterocyclic amines were formed in excellent yields and chemoselectivity. High conversion yields of nitroarenes into the corresponding amines were observed by using polar protic solvents, such as MeOH and i PrOH. Among several hydrogen donors that were examined, methylhydrazine demonstrated the best performance. Preliminary mechanistic investigations, supported by UV-vis and NMR spectroscopy, cyclic voltammetry, and high-resolution mass spectrometry, suggest a cooperative action of methylhydrazine and [Co(κS,N-tfmp2S)3] via a coordination activation pathway that leads to the formation of a reduced cobalt species, responsible for the catalytic transformation. In general, the corresponding N-arylhydroxylamines were identified as the sole intermediates. Nevertheless, the corresponding nitrosoarenes can also be formed as intermediates, which, however, are rapidly transformed into the desired arylamines in the presence of methylhydrazine through a noncatalytic path. On the basis of the observed high chemoselectivity and yields, and the fast and clean reaction processes, the present catalytic system [Co(κS,N-tfmp2S)3]/MeNHNH2 shows promise for the efficient synthesis of aromatic amines that could find various industrial applications.The bulk photovoltaic effect in noncentrosymmetric materials is an intriguing physical phenomenon that holds potential for high-efficiency energy harvesting. Here, we study the shift current bulk photovoltaic effect in the transition-metal dichalcogenide MoS2. We present a simple automated method to guide materials design and use it to uncover a distortion to monolayer 2H-MoS2 that dramatically enhances the integrated shift current. Using this distortion, we show that overlap in the Brillouin zone of the distributions of the shift vector (a quantity measuring the net displacement in real space of coherent wave packets during excitation) and the transition intensity is crucial for increasing the shift current. The distortion pattern is related to the material polarization and can be realized through an applied electric field via the converse piezoelectric effect. This finding suggests an additional method for engineering the shift current response of materials to augment previously reported methods using mechanical strain.In this study, the thermal, mechanical, and chemical equilibrium conditions are derived for binary solid-liquid equilibrium under the effect of an electric field. As an example, the effect of an electric field on the water/glycerol solid-liquid phase diagram is computed over the complete mole fraction range. We show that the application of an electric field can affect the composition dependent freezing and precipitating processes, changing freezing and precipitating temperatures and changing the eutectic point temperature and mole fraction.Nitrosyl metal complexes (M-NO), in which nitrosyl ligands are coordinated to transition-metal ions, have been studied from the viewpoints of physiological activity, catalytic activity, and photosensitivity. The structural flexibility and electric polarization of the nitrosyl ligand are attractive characteristics. Herein we show a photoswitchable nonlinear-optical (NLO) crystal based on a dysprosium-iron nitrosyl assembly. This crystal is composed of a one-dimensional chain structure in the polar Pna21 space group. Because of spontaneous electric polarization, it exhibits a NLO effect of second harmonic generation (SHG). The SHG signal reversibly changes by alternate irradiation with 473 and 804 nm laser lights. The observed photoreversible switching effect on SHG is caused by photoinduced linkage isomerization of the metal nitrosyl sites, i.e., M-N+═O ↔ M-O═N+. Such an optically switchable NLO crystal should be useful for optical devices such as optical filters and optical shutters as well as probes in SHG microscopy.In this research, six neonicotinoid analogs derived from l-proline were synthesized, characterized, and evaluated as insecticides against Xyleborus affinis. Most of the target compounds showed good to excellent insecticidal activity. To the best of our knowledge, this is the first report dealing with the use of enantiopure l-proline to get neonicotinoids. These results highlighted the compound 9 as an excellent candidate used as the lead chiral insecticide for future development. Additionally, molecular docking with the receptor and compound 9 was carried out to gain insight into its high activity when compared to dinotefuran. Finally, the neurotoxic evaluation of compound 9 showed lower toxicity than the classic neonicotinoid dinotefuran.There is still dispute over the stability of endohedral metallofullerenes (EMFs) M2C2n, and recently, multiform lutetium-based dimetallofullerenes have been dropped in experiments. The thermodynamic stabilities of Lu2C86 EMFs are revealed by density functional theory (DFT) in conjunction with statistical thermodynamic analyses. Inevitably, besides the experimentally reported Lu2@C2v(63751)-C86, Lu2@C s (63750)-C86, and Lu2@C s (63757)-C86, other three metal carbide clusterfullerenes, Lu2C2@D2d(51591)-C84, Lu2C2@C1(51383)-C84, and Lu2C2@C s (id207430)-C84, rather than Lu2@C86 are first characterized as thermodynamically stable isomers of Lu2C86. Specially, the C s (id207430)-C84 is a newly non-classical fullerene containing one heptagon, which is stabilized via encaging Lu2C2. Another interesting phenomenon is that the outer fullerene cages of thermodynamically stable Lu2C82-88 molecules are geometrically connected through C2 addition/loss and Stone-Wales (SW) transformation, suggesting a special relationship between thermodynamic stabilities and geometries of Lu2C82-88 EMFs. Furthermore, the electronic configurations of (Lu2)4+@C864- and (Lu2C2)4+@C844- were confirmed. A significantly stable two-center two-electron (2c-2e) Lu-Lu σ single bond is formed in Lu2@C86. By comparing M-M bonds in M2@C2v(63751)-C86 (M = Sc, Y, La, and Lu), two significant factors, the valence atomic orbital (ns) of metal atoms and radius of M2+, are found to determine the stability of the M-M bond in the C2v(63751)-C86. Additionally, the simulated UV-vis-NIR spectra of thermodynamically stable Lu2C86 isomers were simulated, which further disclose their electronic features.The electric power sector in the United States faces many challenges related to climate change. On the demand side, climate change could shift demand patterns due to increased air temperatures. On the supply side, climate change could lead to deratings of thermal units due to changes in air temperature, water temperature, and water availability. Past studies have typically analyzed these risks separately. Here, we developed an integrated, multimodel framework to analyze how compounding risks of climate-change impacts on demand and supply affect long-term planning decisions in the power system. In the southeast U.S., we found that compounding climate-change impacts could result in a 35% increase in installed capacity by 2050 relative to the reference case. Participation of renewables, particularly solar, in the fleet increased, driven mostly by the expected increase in summertime peak demand. Such capacity requirements would increase investment costs by approximately 31 billion (USD 2015) over the next 30 years, compared to the reference case. These changes in investment decisions align with carbon emission mitigation strategies, highlighting how adaptation and mitigation strategies can converge.Nitrogen/fluorine codoping of rutile TiO2 was recently reported to be effective for introducing visible-light absorption, and the resultant TiO2N,F worked efficiently as an O2 evolution photocatalyst in a Z-scheme water-splitting system. Although an increase in the amount of nitrogen doped into rutile TiO2 lattice in the presence of fluorine was experimentally demonstrated, the role of fluorine in the system remained unclear. Here, we report a computational study on TiO2N,F through the construction of supercell models with substitutional defects to reveal the atomic arrangement of the material and the electronic band structure. Calculations for all possible structures of nitrogen/fluorine and nitrogen/oxygen-vacancy relative positions revealed that the defect complexes were preferentially located on the (110) plane and that the distance between defects did not have a strong correlation with the formation energy. The present work also showed that although fluorine did not directly contribute to the narrowing of the band gap of TiO2N,F, the fluorine activity of the synthetic atmosphere promotes the formation of substitutional defect complexes of nitrogen/fluorine for anion sites. This eventually increases the amount of nitrogen incorporated into the rutile TiO2 lattice and also results in reduction of the amount of oxygen vacancy, which is in qualitative agreement with our previous result of transient absorption measurement for rutile TiO2N,F. The role of fluorine in TiO2N,F is thus clarified through our systematic first-principles calculations.An accurate description of electron transport at a molecular level requires a precise treatment of quantum effects. These effects play a crucial role in determining the electron transport properties of single molecules, which can be challenging to simulate classically. Here we introduce a quantum algorithm to efficiently calculate electronic current through single-molecule junctions in the weak-coupling regime. We show that a quantum computer programmed to simulate vibronic transitions between different charge states of a molecule can be used to compute electron-transfer rates and electronic current. In the harmonic approximation, the algorithm can be implemented using Gaussian boson sampling devices, which are a near-term platform for photonic quantum computing. We apply the algorithm to simulate the current and conductance of a magnesium porphine molecule. The algorithm provides a means for better understanding the mechanism of electron transport at a molecular level, which paves the way for building practical molecular electronic devices.

Szperamy.pl
Logo
Enable registration in settings - general
Compare items
  • Total (0)
Compare
0