A nickel/N‐heterocyclic carbene catalytic system has been established for decarbonylative borylation of amides with B2nep2 by C−N bond activation. This transformation shows good functional‐group ...compatibility and can serve as a powerful synthetic tool for late‐stage borylation of amide groups in complex compounds. More importantly, as a key intermediate, the structure of an acyl nickel complex was first confirmed by X‐ray analysis. Furthermore, the decarbonylative process was also observed. These findings confirm the key mechanistic features of the acyl C−N bond activation process.
Keyed up: A Ni/N‐heterocyclic carbene (NHC) catalytic system has been established for the title reaction, which proceeds by C−N bond activation. As a key intermediate, the structure of an acyl nickel complex was confirmed by X‐ray analysis. The structure displays square‐planar geometry, stabilized by two NHC ligands in trans position. These findings confirm the key mechanistic features of the acyl C−N bond activation process. Boc=tert‐butoxycarbonyl, nep=neopentyl glycolato.
Boron–nitrogen heteroarenes hold great promise for practical application in many areas of chemistry. Enduring interest in realizing this potential has in turn driven perennial innovation with respect ...to these compounds’ synthesis. This Perspective discusses in detail the most recent advances in methods pertaining to the preparation of BN-isosteres of benzene, naphthalene, and their derivatives. Additional focus is placed on the progress enabled by these syntheses toward functional utility of such BN-heterocycles in biochemistry and pharmacology, materials science, and transition-metal-based catalysis. The prospects for future research efforts in these and related fields are also assessed.
BODIPY Fluorophores for Membrane Potential Imaging Franke, Jenna M; Raliski, Benjamin K; Boggess, Steven C ...
Journal of the American Chemical Society,
08/2019, Letnik:
141, Številka:
32
Journal Article
Recenzirano
Odprti dostop
Fluorophores based on the BODIPY scaffold are prized for their tunable excitation and emission profiles, mild syntheses, and biological compatibility. Improving the water-solubility of BODIPY dyes ...remains an outstanding challenge. The development of water-soluble BODIPY dyes usually involves direct modification of the BODIPY fluorophore core with ionizable groups or substitution at the boron center. While these strategies are effective for the generation of water-soluble fluorophores, they are challenging to implement when developing BODIPY-based indicators: direct modification of BODIPY core can disrupt the electronics of the dye, complicating the design of functional indicators; and substitution at the boron center often renders the resultant BODIPY incompatible with the chemical transformations required to generate fluorescent sensors. In this study, we show that BODIPYs bearing a sulfonated aromatic group at the meso position provide a general solution for water-soluble BODIPYs. We outline the route to a suite of 5 new sulfonated BODIPYs with 2,6-disubstitution patterns spanning a range of electron-donating and -withdrawing propensities. To highlight the utility of these new, sulfonated BODIPYs, we further functionalize them to access 13 new, BODIPY-based, voltage-sensitive fluorophores (VF). The most sensitive of these BODIPY VF dyes displays a 48% ΔF/F per 100 mV in mammalian cells. Two additional BODIPY VFs show good voltage sensitivity (≥24% ΔF/F) and excellent brightness in cells. These compounds can report on action potential dynamics in both mammalian neurons and human stem cell-derived cardiomyocytes. Accessing a range of substituents in the context of a water-soluble BODIPY fluorophore provides opportunities to tune the electronic properties of water-soluble BODIPY dyes for functional indicators.
Ca(BH
4
)
2
could reversibly store 9.6 wt% hydrogen based on the overall reaction of Ca(BH
4
)
2
→ 1/3CaB
6
+ 2/3CaH
2
+ 10/3H
2
. Formation of CaB
6
instead of elemental boron and/or high boranes (
...e.g.
CaB
12
H
12
) in the dehydrogenation process is crucial for rehydrogenation. Here, we reported two experimental protocols regarding how to form CaB
6
from the decomposition of Ca(BH
4
)
2
: (1) decomposition below the melting point,
e.g.
350 °C
via
CaB
2
H
6
to CaB
6
and (2) decomposition above the melting point,
e.g.
400 °C
via
elemental boron to CaB
6
.
The formation of CaB
6
from the thermal decomposition of Ca(BH
4
)
2
goes along two distinct routes,
i.e. via
CaB
2
H
6
or elemental boron as a reaction intermediate, depending on temperature.
We demonstrate that polymer electron acceptors with excellent all‐polymer solar‐cell (all‐PSC) device performance can be developed from polymer electron donors by using B←N units. By alleviating the ...steric hindrance effect of the bulky pendant moieties on the conjugated polymers that contain B←N units, the π–π stacking distance of polymer backbones is decreased and the electron mobility is consequently enhanced by nearly two orders of magnitude. As a result, the power conversion efficiency of all‐PSCs with the polymer acting as the electron acceptor is greatly improved from 0.12 % to 5.04 %. This PCE value is comparable to that of the best all‐PSCs with state‐of‐the‐art polymer acceptors.
From giver to taker: Incorporation of B←N units into polymer electron donors has resulted in a series of polymer electron acceptors. Extending the length of the repeating units of the conjugated polymers alleviates the effect of steric hindrance from the pendant groups and promotes the π–π stacking of the polymer backbones. The all‐polymer solar‐cell device shows a power conversion efficiency (PCE) exceeding 5.0 %.
•Amendment of either B or Si significantly alleviated Cd accumulation and toxicity in hydroponically-cultured rice plants.•There existed strong interaction between the two elements in rice tolerance ...to Cd toxicity.•Addition of B and Si alleviated Cd-induced oxidative stress by improving antioxidative systems.•Supplement of B and Si in Cd-treated plants downregulated the expression of Cd transporter genes.
Cadmium (Cd) is a highly toxic heavy metal for both animals and plants. Rice consumption is a major source of Cd intake for human. Minimization of Cd accumulation in rice is key to reduce Cd hazard to human. Here we showed alleviating effects of boron (B), silicon (Si) and their mixture on Cd accumulation and toxicity in hydroponically-cultured rice plants. Cd treatment (100 μM) led to Cd accumulation in roots and shoots, as well as significant reduction in plant growth. However, amendment of either B or Si significantly alleviated Cd accumulation and toxicity. Moreover, simultaneous supply of B and Si showed better alleviating effect. However, addition of B and Si alleviated Cd-induced oxidative stress in Cd-treated plants as reflected by reduced MDA, H2O2 and O2−, as well as increased activities of major antioxidant enzymes. Cd exposure induced the expression of Cd transporter genes of OsHMA2, OsHMA3, OsNramp1 and OsNramp5. In contrast, simultaneous supplement of B and Si in Cd-treated plants compromised the gene expression. Our results show that both B and Si alleviate Cd accumulation and toxicity by improving oxidative stress and suppressing Cd uptake and transport, and the two elements display joint effect.
The electrochemical reduction of CO2 to multi-carbon products has attracted much attention because it provides an avenue to the synthesis of value-added carbon-based fuels and feedstocks using ...renewable electricity. Unfortunately, the efficiency of CO2 conversion to C2 products remains below that necessary for its implementation at scale. Modifying the local electronic structure of copper with positive valence sites has been predicted to boost conversion to C2 products. Here, we use boron to tune the ratio of Cuδ+ to Cu0 active sites and improve both stability and C2-product generation. Simulations show that the ability to tune the average oxidation state of copper enables control over CO adsorption and dimerization, and makes it possible to implement a preference for the electrosynthesis of C2 products. We report experimentally a C2 Faradaic efficiency of 79 ± 2% on boron-doped copper catalysts and further show that boron doping leads to catalysts that are stable for in excess of ~40 hours while electrochemically reducing CO2 to multi-carbon hydrocarbons.
Photocatalytic H2O2 evolution through two‐electron oxygen reduction has attracted wide attention as an environmentally friendly strategy compared with the traditional anthraquinone or ...electrocatalytic method. Herein, a biomimetic leaf‐vein‐like g‐C3N4 as an efficient photocatalyst for H2O2 evolution is reported, which owns tenable band structure, optimized charge transfer, and selective two‐electron O2 reduction. The mechanism for the regulation of band structure and charge transfer is well studied by combining experiments and theoretical calculations. The H2O2 yield of CN4 (287 µmol h−1) is about 3.3 times higher than that of pristine CN (87 µmol h−1), and the apparent quantum yield for H2O2 evolution over CN4 reaches 27.8% at 420 nm, which is much higher than that for many other current photocatalysts. This work not only provides a novel strategy for the design of photocatalyst with excellent H2O2 evolution efficiency, but also promotes deep understanding for the role of defect and doping sites on photocatalytic activity.
Leaf‐vein‐like g‐C3N4 synthesized via a KBH4‐assisted thermal polycondensation strategy exhibits enhanced optical absorption, efficient charge carrier separation, and ample active sites, accordingly enabling excellent photocatalytic H2O2 evolution. The synergistic effect of B doping and defect sites on the improvement of catalyst performance is fully discussed by experiments and density functional theory calculations.
Inhibition of TICT can significantly increase the brightness of fluorescent materials. Accurate prediction of TICT is thus critical for the quantitative design of high‐performance fluorophores and ...AIEgens. TICT of 14 types of popular organic fluorophores were modeled with time‐dependent density functional theory (TD‐DFT). A reliable and generalizable computational approach for modeling TICT formations was established. To demonstrate the prediction power of our approach, we quantitatively designed a boron dipyrromethene (BODIPY)‐based AIEgen which exhibits (almost) barrierless TICT rotations in monomers. Subsequent experiments validated our molecular design and showed that the aggregation of this compound turns on bright emissions with ca. 27‐fold fluorescence enhancement, as TICT formation is inhibited in molecular aggregates.
A generalizable and reliable computational approach is formulated for modeling the twisted intramolecular charge transfer. Applying this approach in combination with experimental validations, azetidinyl‐substituted PRODAN and BODIPY derivatives were designed for bioimaging and aggregation‐induced emission (AIE) applications with enhanced performance.
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