Phosphorus has been successfully fused into a classic rhodamine framework, in which it replaces the bridging oxygen atom to give a series of phosphorus‐substituted rhodamines (PRs). Because of the electron‐accepting properties of the phosphorus moiety, which is due to effective σ*–π* interactions and strengthened by the inductivity of phosphine oxide, PR exhibits extraordinary long‐wavelength fluorescence emission, elongating to the region above 700 nm, with bathochromic shifts of 140 and 40 nm relative to rhodamine and silicon‐substituted rhodamine, respectively. Other advantageous properties of the rhodamine family, including high molar extinction coefficient, considerable quantum efficiency, high water solubility, pH‐independent emission, great tolerance to photobleaching, and low cytotoxicity, stay intact in PR. Given these excellent properties, PR is desirable for NIR‐fluorescence imaging in vivo. 相似文献
The first highly diastereoselective and enantioselective catalytic asymmetric Michael addition of cyclic azomethine ylides with nitroalkenes have been developed to diastereodivergently generate either the syn or anti adducts by employing N,O‐ligand/Cu(OAc)2 and N,P‐ligand/Cu(OAc)2 catalytic systems. Both catalytic systems exhibit broad substrate applicability to afford the corresponding Michael adducts in good to excellent yields, with excellent levels of diastereo‐ (up to 99:1 diastereomeric ratio) and enantioselectivities (up to >99 % enantiomeric excess). Importantly, the chiral 1,7‐diazaspiro[4.4]nonane diastereomer derivatives can be easily obtained in good yields through facile NaBH4 reduction of the Michael adducts. 相似文献
This article describes a fluorescent molecularly imprinted polymer (MIP) capable of selective fluorescent turn-on recognition of the tumor biomarker α-fetoprotein. The technique is making use of amino-modified Mn-doped ZnS quantum dots (QDs) as solid supports, 4-vinylphenylboronic acid and methyl methacrylate as the functional monomers, γ-methacryloxypropyl trimethoxysilane as the grafting agent, and α-fetoprotein as a template. A graft imprint is created on the surface of the QDs. The functional monomers are shown to play an important role in the formation of the binding sites and in preventing nonspecific protein binding. The resulting MIP-QDs display a good linear response to α-fetoprotein in the 50 ng · L−1 to 10 μg · L−1 concentration range, and the limit of detection is 48 ng · L−1. In our perception, the method has a wide scope in that it may be adapted to various other glycoproteins.
The N–H bond activation product [PNP]‐FeI(PMe3)2 ( 2 ) was obtained at room temperature by the reaction of diphosphinito [PNP] pincer ligand ((Ph2P(C6H4))2NH ( 1 )) with Fe(PMe3)4. Treatment of 1 with Co(PMe3)4, CoCl(PMe3)3 and CoMe(PMe3)4 afforded the same N–H bond activation product [PNP]‐CoI(PMe3)2 ( 3 ). In order to have a better understanding of the mechanism of formation of 3 , in situ IR and 1H NMR spectroscopic investigations were conducted.The reaction of 1 with Ni(PMe3)4 afforded the ligand replacement complex 4 while a [PNP]‐NiIIMe complex 5 was obtained via deprotonation through the reaction of 1 with NiMe2(PMe3)3. The molecular structures of 2 – 4 were confirmed by X‐ray diffraction analysis. 相似文献
Plants that absorb silicon may induce isotope fractionation that causes relative abundance changes in biogeochemical processes in organisms and environment. Silicon isotopes (28Si, 29Si, and 30Si) were determined with high precision using multicollector inductively coupled plasma mass spectrometer. In the present study, the silicon isotope composition was determined in maize and corresponding soil was collected from Zhejiang Province, China. The δ30Si values were from ?2.7 to 3.3‰ in the plant tissues. The isotope fractionation between precipitated and dissolved silicon was 0.9976 and the silicon isotope fractionation in the plants was appeared to be Rayleigh-like process. The fractionation factors between the whole plants and the soil–water-soluble fractions were estimated to be 0.9989, indicating the presence of biochemical silicon isotope fractionation. The active uptake of silicon appeared to play an important role through which the heavy silicon isotopes were preferentially absorbed and transferred to the aboveground plant tissues. However, the roles of a passive mechanism for silicon uptake could not be ruled out through which the light silicon isotopes preferentially precipitated in various plant tissues. 相似文献
A global chemical profiling based quality evaluation approach using ultra performance liquid chromatography with tandem quadrupole time‐of‐flight mass spectrometry was developed for the quality evaluation of three rhubarb species, including Rheum palmatum L., Rheum tanguticum Maxim. ex Balf., and Rheum officinale Baill. Considering that comprehensive detection of chemical components is crucial for the global profile, a systemic column performance evaluation method was developed. Based on this, a Cortecs column was used to acquire the chemical profile, and Chempattern software was employed to conduct similarity evaluation and hierarchical cluster analysis. The results showed R. tanguticum could be differentiated from R. palmatum and R. officinale at the similarity value 0.65, but R. palmatum and R. officinale could not be distinguished effectively. Therefore, a common pattern based on three rhubarb species was developed to conduct the quality evaluation, and the similarity value 0.50 was set as an appropriate threshold to control the quality of rhubarb. A total of 88 common peaks were identified by their accurate mass and fragmentation, and partially verified by reference standards. Through the verification, the newly developed method could be successfully used for evaluating the holistic quality of rhubarb. It would provide a reference for the quality control of other herbal medicines. 相似文献
Fullerene‐based liquid crystalline materials have both the excellent optical and electrical properties of fullerene and the self‐organization and external‐field‐responsive properties of liquid crystals (LCs). Herein, we demonstrate a new family of thermotropic [60]fullerene supramolecular LCs with hierarchical structures. The [60]fullerene dyads undergo self‐organization driven by π–π interactions to form triple‐layer two‐dimensional (2D) fullerene crystals sandwiched between layers of alkyl chains. The lamellar packing of 2D crystals gives rise to the formation of supramolecular LCs. This design strategy should be applicable to other molecules and lead to an enlarged family of 2D crystals and supramolecular liquid crystals. 相似文献
Conjugated microporous polymers (CMPs), with the virtue of high porosity and optoelectronic activity, are attracting increasing research interest and have been used in various environmental and energy areas. Efficient synthesis and the exploitation of new functionalities are the research hotspots in the CMPs research area. Covalent triazine frameworks (CTFs) synthesized by CF3SO3H catalyzed trimerization reactions show properties quite alike to CMPs and this method avoids the use of noble metal catalysts. In this study, a series of novel fluorescent covalent triazine‐based frameworks (F‐CTFs) is prepared using different tetra‐cyano compounds as the starting monomers. Both porosity and fluorescence properties of the F‐CTFs can be adjusted by the monomer structure. Gas adsorption measurement reveals that F‐CTF1 with the largest surface area of 896 m2 g−1 shows the highest CO2 uptake of 3.29 mmol g−1 at 273 K and 1.13 bar among the polymers. Taking advantages of their large surface areas and strong fluorescence, these F‐CTFs could be used as efficient chemical sensing agents for various nitroaromatic compounds as well.
Cu/Ag(I) were introduced into iodoplumbate systems to produce two new heterometallic iodoplumbates with viologen as templates, i.e. (PV)2(Pb2Cu2I10) (1) and [(BV)(Pb2AgI7)]n (2) (PV2+ = propyl viologen, BV2+ = benzyl viologen), in which the common connection of PbI6 units have been remarkably altered. In (PV)2(Pb2Cu2I10) (1), two PbI6 octahedra are bridged by two CuI4 tetrahedra via face-sharing to give a (Pb2Cu2I10)4? cluster, but the ternary one-dimensional polymeric (Pb2AgI7)n2n? of [(BV)(Pb2AgI7)]n (2) is assembled from edge-sharing AgI4 tetrahedra and PbI6 octahedra. Their optical band gaps and fluorescence were also discussed. The absorption edges of haloplumbates could be engineered by introduction of suitable conjugated molecules as templates. 相似文献