Search

We reported herein a novel gold(I) bifluoride complex, LAuHF2, supported by a sterically bulky ligand (L, tBuXantphos), displays exceptional reactivity toward hydrodefluorination (HDF) and hydrosilylation of CO2 in the presence...

New linkages for covalent organic frameworks (COFs) have been continuously pursued by chemists as they serve as the structure and property foundation for the materials. Developing new reaction types or modifying known linkages have been the only two methods to create new COF linkages. Herein, we report a novel strategy that uses H3PO3 as a bifunctional catalyst to achieve amine-linked COFs from readily available amine and aldehyde linkers. The acidic proton of H3PO3 catalyzes the imine framework formation, which is then in situ reduced to the amine COF by the reductive P-H moiety. The amine-linked COF outperforms its imine analogue in promoting Knoevenagel condensation because of the more basic sites and higher stability.

Metalation of covalent organic frameworks (COFs) is a critical strategy to functionalize COFs for advanced applications yet largely relies on the pre-installed specific metal docking sites in the network, such as porphyrin, salen, 2,2′-bipyridine, etc. We show in this study that the imine linkage of simple imine-based COFs, one of the most popular COFs, readily chelate transition metal (Ir in this work) via cyclometalation, which has not been explored before. The iridacycle decorated COF exhibited more than 10-fold efficiency enhancement in (photo)catalytic hydrogen evolution from aqueous formate solution than its molecular counterpart under mild conditions. This work will inspire more functional cyclometallated COFs to be explored beyond catalysis considering the large imine COF library and the rich metallacycle chemistry., This study describes cyclometallation as a new metal binding mode for imine-based COFs. The iridacycle decorated COF could be used for catalytic hydrogen evolution from aqueous formate solution with high stability and high efficacy.

This work reports the synthesis and characterization of a new C^N-based cycloplatinated(II) fluoride complex, [Pt(ppy)(PPh3)F] (2; ppy = 2-phenylpyridinate), involving a Pt-F bond. The new complex is highly luminescent in the green area with a high quantum yield of 94.6% at 77 K. A comparison study of the heavier halogen derivatives reveals a descending emission quantum yield order of F > Cl > Br > I. Time-dependent density functional theory calculations ascribe the decreased emission efficiency to the decreasing trend of an intraligand (IL) transition from F to I, which accounts for the major radiative pathway. In addition, 2 is capable of the fluorinating alkyl halides, leading to Csp3-F bond formation at room temperature.

Covalent organic frameworks (COFs) are a rapidly developing class of materials that has been of immense research interest during the last ten years. Numerous reviews have been devoted to summarizing the synthesis and applications of COFs. However, the underlying dynamic covalent chemistry (DCC), which is the foundation of COFs synthesis, has never been systematically reviewed in this context. Dynamic covalent chemistry is the practice of using thermodynamic equilibriums to molecular assemblies. This Critical Review will cover the state-of-the-art use of DCC to both synthesize COFs and expand the applications of COFs. Five synthetic strategies for COF synthesis are rationalized, namely: modulation, mixed linker/linkage, sub-stoichiometric reaction, framework isomerism, and linker exchange, which highlight the dynamic covalent chemistry to regulate the growth and to modify the properties of COFs. Furthermore, the challenges in these approaches and potential future perspectives in the field of COF chemistry are also provided.

Two-dimensional urea- and thiourea-containing covalent organic frameworks (COFs) were synthesized at ambient conditions at large scale within 1 h in the absence of an acid catalyst. The site-isolated urea and thiourea in the COF showed enhanced catalytic efficiency as a hydrogen-bond-donating organocatalyst compared to the molecular counterparts in epoxide ring-opening reaction, aldehyde acetalization, and Friedel-Crafts reaction. The COF catalysts also had excellent recyclability.

Histone deacetylase 6 (HDAC6) is a multifunctional cytoplasmic enzyme involved in diverse cellular processes such as intracellular transport and protein quality control. Inhibition of HDAC6 can alleviate defects in cell and rodent models of certain diseases, particularly neurodegenerative disorders, including Alzheimer's disease and amyotrophic lateral sclerosis. However, while HDAC6 represents a potentially powerful therapeutic target, development of effective brain-penetrant HDAC6 inhibitors remains challenging. Recently, [18F]EKZ-001 ([18F]Bavarostat), a brain-penetrant positron emission tomography (PET) radioligand with high affinity and selectivity toward HDAC6, was developed and evaluated preclinically for its ability to bind HDAC6. Herein, we describe the efficient and robust fully automated current Good Manufacturing Practices (cGMP) compliant production method. [18F]EKZ-001 quantification methods were validated in nonhuman primates (NHP) using full kinetic modeling, and [18F]EKZ-001 PET was applied to compare dose-occupancy relationships between two HDAC6 inhibitors, EKZ-317 and ACY-775. [18F]EKZ-001 is cGMP produced with an average decay-corrected radiochemical yield of 14% and an average molar activity of 204 GBq/μmol. We demonstrate that a two-tissue compartmental model and Logan graphical analysis are appropriate for [18F]EKZ-001 PET quantification in NHP brain. Blocking studies show that the novel compound EKZ-317 achieves higher target occupancy than ACY-775. This work supports the translation of [18F]EKZ-001 PET for first-in-human studies. ispartof: ACS CHEMICAL NEUROSCIENCE vol:11 issue:7 pages:1093-1101 ispartof: location:United States status: published

A family of cationic cycloplatinated(II) complexes [Pt(dfppy)(P^P)]Cl, dfppy = 2-(2,4-difluorophenyl)pyridine, incorporating bisphosphine ligands, P^P = bis(diphenylphosphino)methane (1, dppm), 1,2-bis(diphenylphosphino)ethane (2, dppe) and 1,2-bis(diphenylphosphino)benzene (3, dppbz), was prepared. The complexes were characterized by means of several analytical and spectroscopic methods. These complexes displayed acceptable stability in the biological environments which was confirmed by NMR, HR ESI-MS and UV-vis techniques. The antiproliferative properties of these complexes were evaluated by National Cancer Institute (NCI) at National Institutes of Health (NIH) against 60 different human tumor cell lines such as leukemia, melanoma, lung, colon, brain, ovary, breast, prostate and kidney. These complexes showed higher cytotoxicity than cisplatin against a wide variety of cancer cell lines such as K-562 (leukemia), HOP-92 (lung), HCT-116 (colon), OVCAR-8 (ovarian), PC-3 (prostate), MDA-MB-468 (breast), and melanoma cancer cell lines. Complex 3 as the most potent compound in this study furnished an excellent anti-proliferative activity compared to the cisplatin against Hela, SKOV3, and MCF-7 cancer cell lines. The main mode of the interaction of 1–3 with DNA was also determined using molecular docking studies.

A practical and efficient synthetic procedure to novel chromeno[3,2-d]oxazoles through a one-pot sequential multistep process is presented. This procedure proceeds efficiently in propylene carbonat...

New linkages for covalent organic frameworks (COFs) have been continuously pursued by chemists as they serve as the structure and property foundation for the materials. Developing new reaction types or modifying known linkages have been the only two methods to create new COF linkages. Herein, we report a novel strategy that uses H

A new covalent organic framework (COF) based on imine bonds was assembled from 2-(4-formylphenyl)-5-formylpyridine and 1,3,6,8-tetrakis(4-aminophenyl)pyrene, which showed an interesting dual-pore structure with high crystallinity. Postmetallation of the COF with Pt occurred selectively at the N donor (imine and pyridyl) in the larger pores. The metallated COF served as an excellent recyclable heterogeneous photocatalyst for decarboxylative difluoroalkylation and oxidative cyclization reactions.

This work reports the synthesis and characterization of a new C^N-based cycloplatinated(II) fluoride complex [Pt(ppy)(PPh(3))F] (2, ppy = 2-phenylpyridinate), involving a Pt‒F bond. The new complex is highly luminescent in green area with a high quantum yield of 94.6% at 77K. A comparison study of the heavier of halogen derivatives reveals a descending emission quantum yield order of F > Cl > Br > I. Time-dependent density functional theory (TD-DFT) calculations ascribe the decreased emission efficiency to the decreasing trend of intra ligand (IL) transition from F to I, which accounts for the major radiative pathway. In addition, 2 is capable of the fluorinating alkyl halides leading to Csp(3)‒F bond formation at room temperature.

Histone deacetylase 6 (HDAC6) is a multifunctional cytoplasmic enzyme involved in diverse cellular processes such as intracellular transport and protein quality control. Inhibition of HDAC6 can alleviate defects in cell and rodent models of certain diseases, particularly neurodegenerative disorders, including Alzheimer’s disease and amyotrophic lateral sclerosis. However, while HDAC6 represents a potentially powerful therapeutic target, development of effective brain-penetrant HDAC6 inhibitors remains challenging. Recently [(18)F]EKZ-001 ([(18)F]Bavarostat), a brain-penetrant positron emission tomography (PET) radioligand with high affinity and selectivity towards HDAC6, was developed and evaluated preclinically for its ability to bind HDAC6. Herein, we describe the efficient and robust fully automated current good manufacturing practices (cGMP) compliant production method. [(18)F]EKZ-001 quantification methods were validated in non-human primates (NHP) using full kinetic modelling and [(18)F]EKZ-001 PET was applied to compare dose-occupancy relationships between two HDAC6 inhibitors, EKZ-317 and ACY-775. [(18)F]EKZ-001 is cGMP produced with an average decay-corrected radiochemical yield of 14 % and an average molar activity of 204 GBq/μmol. We demonstrate that a two-tissue compartmental model and Logan graphical analysis are appropriate for [(18)F]EKZ-001 PET quantification in NHP brain. Blocking studies show that the novel compound, EKZ-317, achieves higher target occupancy than ACY-775. This work supports the translation of [(18)F]EKZ-001 PET for first-in-human studies.

“Configurational isomerism” is an important approach found in naturally occurring chlorophylls to modulate light harvesting function without significant structural changes; however, this feature has been seldom applied in design of antenna ligands for lanthanide (Ln) sensitization. In this work, we introduced a bioinspired approach by orientation of β-dilactone moieties on porphyrinates, namely cis-/trans-porphodilactones, to modulate the energy transfer process from the lowest triplet excited state of the ligand (T1) to the emitting level of ytterbium(III) (2F5/2, Yb*). Interestingly, near-infrared (NIR) emission of Yb(III) could be switched “on” by the cis-porphodilactone ligand, while the trans-isomer renders Yb(III) emission “off” and the ratio of quantum yields is ∼8. Analysis of the structure–photophysical properties relationship suggests that the significant emission difference is correlated to the energy gaps between T1 and Yb* (1152 cm–1 in the cis- vs −25 cm–1 in the trans-isomer). More interest...

We describe the synthesis of β-fluorinated porpholactones by oxidation of the fluorinated CC bond of the pyrrolic subunit in porphyrin using the “RuCl3 + Oxone®” protocol. The electron-withdrawing effects of β-fluorine on the absorption, fluorescence, phosphorescence and redox properties of the β-fluoroporpholactones were studied. A potential application of the β-fluoroporpholactones was demonstrated in sensitizing near-IR (NIR) emissive ytterbium, giving a high quantum yield (58%) and long luminescence time (525 μs) in CD2Cl2.

INTRODUCTION: Glucose has been deemed the driving force of tumor growth for decades. However, research has shown that several tumors metabolically shift towards glutaminolysis. The development of radiolabeled glutamine derivatives could be a useful molecular imaging tool for visualizing these tumors. We elaborated on the glutamine-derived PET tracers by developing two novel probes, namely [(18)F]fluorophenylglutamine and [(18)F]fluorobiphenylglutamine MATERIALS AND METHODS: Both tracers were labelled with fluorine-18 using our recently reported ruthenium-based direct aromatic fluorination method. Their affinity was evaluated with a [(3)H]glutamine inhibition experiment in a human PC-3 and a rat F98 cell line. The imaging potential of [(18)F]fluorophenylglutamine and [(18)F]fluorobiphenylglutamine was tested using a mouse PC-3 and a rat F98 tumor model. RESULTS: The radiosynthesis of both tracers was successful with overall non-decay corrected yields of 18.46 ± 4.18 % (n=10) ([(18)F]fluorophenylglutamine) and 8.05 ± 3.25 % (n=5) ([(18)F]fluorobiphenylglutamine). In vitro inhibition experiments showed a moderate and low affinity of fluorophenylglutamine and fluorobiphenylglutamine, respectively, towards the human ASCT-2 transporter. Both compounds had a low affinity towards the rat ASCT-2 transporter. These results were endorsed by the in vivo experiments with low uptake of both tracers in the F98 rat xenograft, low uptake of [(18)F]FBPG in the mice PC-3 xenograft and a moderate uptake of [(18)F]FPG in the PC-3 tumors. CONCLUSION: We investigated the imaging potential of two novel PET radiotracers [(18)F]FPG and [(18)F]FBPG. [(18)F]FPG is the first example of a glutamine radiotracer derivatized with a phenyl group which enables the exploration of further derivatization of the phenyl group to increase the affinity and imaging qualities. We hypothesize that increasing the affinity of [(18)F]FPG by optimizing the substituents of the arene ring can result in a high-quality glutamine-based PET radiotracer. ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE: We hereby report novel glutamine-based PET-tracers. These tracers are tagged on the arene group with fluorine-18, hereby preventing in vivo defluorination, which can occur with alkyl labelled tracers (e.g. (2S,4R)4-[(18)F]fluoroglutamine). [(18)F]FPG shows clear tumor uptake in vivo, has no in vivo defluorination and has a straightforward production. We believe this tracer is a good starting point for the development of a high-quality tracer which is useful for the clinical visualization of the glutamine transport.

A practical and efficient synthetic procedure to novel chromeno[3,2

To conclude the design principle for high-performance erbium-based single-ion magnets (SIMs), two half-sandwich type erbium complexes 1Er [(LOMe)Er(COT)] (LOMe = [(η5-C5H5)Co{P([double bond, length as m-dash]O)(OMe)2}3], COT = cyclooctatetraenyl) and 2Er [(THF)2(OAr)Er(COT)] (Ar = 2,6-Dipp2C6H3, Dipp = 2,6-diisopropylphenyl) were synthesized, and structurally and magnetically characterized. Both of them exhibited SIM behavior. Their magnetic relaxation behaviours were further elucidated by ab initio calculations and near-IR emission spectroscopy. The results demonstrated that an axial ligand with a weaker electron-donating effect was preferential to construct high blocking barrier erbium-based SIMs.

The combination of continuous flow technology with immobilizing of only 0.13 mol% of triflic acid (TfOH) on silica-encapsulated superparamagnetic iron oxide nanoparticles (SPIONs) under solvent-free conditions successfully provided a powerful, efficient, and eco-friendly route for the synthesis of plasticizers. The turnover frequency value in micro-flow conditions varied in the range of 948.7 to 7384.6 h−1 compared to 403.8 to 3099 h−1 for in-flask. This technique works efficiently, encouraging future applications of micro-flow nano-catalysis in green chemistry.

This study developed a facile and efficient synthetic strategy to construct quaternary chiral centers at the α-position of imines and ketones. High regioselectivity and diastereoselectivity were achieved through the synergetic effect of electron-withdrawing directing groups and N-tert-butyl sulfinamide as chiral auxiliaries. Either of them could be removed under the optimized conditions without any epimerization.

We report a series of highly NIR emissive Yb complexes, in which the Yb is sandwiched between an octafluorinated porphyrinate antenna ligand and a deuterated Kläui ligand, and one of the complexes has an unprecedented quantum yield of 63%., The design of highly near-infrared (NIR) emissive lanthanide (Ln) complexes is challenging, owing to the lack of molecular systems with a high sensitization efficiency and the difficulty of achieving a large intrinsic quantum yield. Previous studies have reported success in optimizing individual factors and achieving high overall quantum yields, with the best yield being 12% for Yb(iii). Herein we report a series of highly NIR emissive Yb complexes, in which the Yb is sandwiched between an octafluorinated porphyrinate antenna ligand and a deuterated Kläui ligand, which allowed optimization of two factors in the same system, and one of the complexes had an unprecedented quantum yield of 63% (estimated uncertainty 15%) in CD2Cl2 with a long lifetime (τ obs) of 714 μs. Systematic analysis of the structure–photophysical properties relationship suggested that porphyrinates are effective antenna ligands with a sensitization efficiency up to ca. 100% and that replacement of the high-energy C–H oscillators in porphyrinate and Kläui ligands significantly improves the intrinsic quantum yield up to 75% (τ obs/τ rad), both of which contribute to enhancing the NIR emission intensity of Yb(iii) up to 25-fold. Besides the high luminescence efficiency, these Yb complexes have other attractive features such as excitation in the visible range and large extinction coefficients which make these Yb(iii) complexes outstanding optical materials in the NIR region.

A tricoordinated gold(I) chloride complex, tBuXantphosAuCl, supported by a sterically bulky 9,9-dimethyl-4,5-bis(di-tert-butylphosphino)xanthene ligand (tBuXantphos) was synthesized. This complex features a remarkably longer Au-Cl bond length [2.632(1) Å] than bicoordinated linear gold complexes (2.27-2.30 Å) and tricoordinated XantphosAuCl [2.462(1) Å]. Single-crystal X-ray diffraction analysis of a cocrystal of tBuXantphosAuCl and pentafluoronitrobenzene (PFNB) and UV-vis spectroscopic titration experiments revealed the existence of an anion-π interaction between the Cl anion ligand and PFNB. Stoichiometric reaction between PFNB and tBuXantphosAuOtBu, after replacement of Cl by a more nucleophilic tBuO anion ligand, showed higher reactivity and para selectivity in the transformation of C-F to C-OtBu bond, distinctively different from that when only KOtBu was used (ortho selectivity) under the identical condition. Mechanistic studies including density functional theory calculations suggested a gold-mediated nucleophilic ligand attack of the C-F bond pathway via an SNAr process. On the basis of these results, using trimethylsilyl derivatives TMS-X (X = OMe, SEt, NEt2) as the nucleophilic ligand source and the fluorine acceptor, catalytic transformation of the C-F bond of aromatic substrates to the C-X (X = O, S, N) bond was achieved with tBuXantphosAuCl as the catalyst (up to 20 turnover numbers).

For this paper, according to the statistics of water resources amounts and utilization needs, we carried out a water resources security preliminary evaluation from the following points of view: water consumption balance analysis, available water resources analysis, supply-demand water resources balance analysis, and overall water resources security analysis for the Yellow River Basin in 2009. The results of the research show that the consumption rate in 2009 was 75.5% for the Yellow River Basin. The total amount of local water in the Yellow River Basin was 58.210 billion m3, but both the supply water and the amount of available water are very low. Meanwhile, from the point of view of net water consumption, the deficit water resource amounts to16.763 billion m3, and in view of the size of the water supply, the deficit water resources amounts to 16.12 billion m3. The current deficit has been created by over-exploiting groundwater, squeezing ecological water consumption, re-using wastewater, and utilizing brackish water, sea water. Therefore, the water supply in the Yellow River Basin is not sustainable, and so it is not secure. As there exist issues in terms of the water resource and in terms of socioeconomic security and ecological security in the Yellow River Basin, we can conclude that the present Yellow River water resource is not reliable, which means that this water resource may not be able to meet future normal demands for living, production, and ecology maintenance.

Porous electrodes commonly exhibit much higher charge–discharge capacities than normal electrodes due to their large surface areas. Some factors such as pore size (pore diameter) and wall thickness also influence the electrochemical behavior of porous electrodes in lithium-ion batteries (e.g. the rate of Li-ion intercalation). Here we investigated how the pore length influenced the charge–discharge capacities by using mesoporous Co3O4 with various particle sizes synthesised via controlling the particle size of SBA-15 templates. The capacity and rate capability of porous Co3O4 were increased with reduction in particle size.

Based on monthly mean temperature and precipitation data for 53 years, from 1957 to 2009, recorded at the Zhangweinan River Basin and five main meteorological stations around it, the non-parametric Mann-Kendall trend test method and cumulative anomaly methods were adopted to analyze the long-term trends here of such key meteorological elements as annual mean temperature, maximum temperature, minimum temperature and precipitation; the corresponding Hurst index was calculated; and future change trends for various meteorological elements were predicted. The results of the analyses indicate that: there is an inconspicuous downward trend in annual precipitation for the Zhangweinan River Basin, with large decreases appearing in summer, with an M-K slope of -11.82 mm/10a; the annual mean temperature rises more significantly, and the M-K slope of the whole Basin's annual mean temperature reaches 0.17°C/10a, the temperature increase being significant in spring and winter. According to the Hurst Index calculations, the annual mean temperature and precipitation series show strong continuity in the Zhangweinan River Basin, which indicates that the future trend will be consistent with that of the past. These research results will not only help provide evidence for the climate change in the Zhangweinan River Basin but can also lay the foundation for further studies on water resources security evaluation in conditions of climate change.

Activation of the C–F bond by transition-metal catalysts not only advances fundamental understanding of the formation and reactivity of organometallic fluoride complexes but also provides a potential approach to partially fluorinated organic compounds from readily available perfluorinated bulk chemicals. Hydrodefluorination (HDF) is regarded as a simple but important reaction among various C–F functionalizations, which features a mechanistic diversity as model reactions for C–F bond activations. Following Lentz and Braun’s review (Angew Chem Int Ed 52, 3328–3348, 2013), we review transition-metal-mediated HDF reactions according to periodic table from group 3–12 metals.