Search

The design of molecular functional materials with multi-step magnetic transitions has attracted considerable attention. However, the development of such materials is still infrequent and challenging. Here, a cyano-bridged square Prussian blue complex that exhibits a thermally induced four-step electron transfer coupled spin transition (ETCST) is reported. The magnetic and spectroscopic analyses confirm this multi-step transition. Variable-temperature infrared spectrum suggested the electronic structures in each phase and a four-step transition model is proposed. [ABSTRACT FROM AUTHOR]

Organic photoresponsive materials, which change their physical properties upon irradiation with light, are attracting tremendous scientific attention, as they offer a flexible and sustainable platform for developing various optoelectronic devices. In this work, photoinduced magnetization switching in two carbazole‐functionalized organic molecules, (9H‐carbazol‐9‐yl)(4‐chlorophenyl)methanone (ClPhCz) and (9H‐carbazol‐9‐yl)(2,4‐dichlorophenyl)methanone (DClPhCz) is reported for the first time. It was found that stabilization of the triplet excited state in those molecules is long enough for a net change in magnetic moment to be detected with a SQUID magnetometer. The change in magnetic moment upon excitation with a blue light laser was larger in ClPhCz, remaining high upon repeating the photoirradiation. In contrast, DClPhCz exhibited a smaller magnetic response, which gradually decreased upon repeating the experiment. [ABSTRACT FROM AUTHOR]

As a remote and non‐contact stimulus, light offers the potential for manipulating the polarization of ferroelectric materials without physical contact. However, in current research, the non‐contact write‐read (erase) process lacks direct observation through the stable current as output signal. To address this limitation, we investigated the photoinduced polarization switching capabilities of the cyanide‐bridged compound [Fe2Co] using visible light, leading to the achievement of rewritable polarization. By subjecting [Fe2Co] crystals to alternating irradiation with 785 nm and 532 nm light, the polarization changes exhibited a distinct square wave pattern, confirming the reliability of the writing and erasing processes. Initialization involved exposing specific crystal units to 532 nm light for storing "1" or "0" information, while reading was accomplished by scanning the units with 785 nm light, resulting in brief current pulses for "1" states and no current signal for "0" states. This research unveils new possibilities for optical storage systems, paving the way for efficient and rewritable data storage and retrieval technologies, such as the next‐generation memories. [ABSTRACT FROM AUTHOR]

Mechanically interlocked molecules (MIMs) including famous catenanes show switchable physical properties and attract continuous research interest due to their potential application in molecular devices. The advantages of using spin crossover (SCO) materials here are enormous, allowing for control through diverse stimuli and highly specific functions, and enabling the transfer of the internal dynamics of MIMs from solution to solid state, leading to macroscopic applications. Herein, we report the efficient self-assembly of catenated metal-organic frameworks (termed catena-MOFs) induced by stacking interactions, through the combination of rationally selected flexible and conjugated naphthalene diimide-based bis-pyridyl ligand (BPND), [MI(CN)2]− (M = Ag or Au) and Fe2+ in a one-step strategy. The obtained bimetallic Hofmann-type SCO-MOFs [FeII(BPND){Ag(CN)2}2]·3CHCl3 (1Ag) and [FeII(BPND{Au(CN)2}2]·2CHCl3·2H2O (1Au) possess a unique three-dimensional (3D) catena-MOF constructed from the polycatenation of two-dimensional (2D) layers with hxl topology. Both complexes undergo thermal- and light-induced SCO. Significantly, abnormal increases in the maximum emission intensity and dielectric constant can be detected simultaneously with the switching of spin states. This research opens up SCO-actuated bistable MIMs that afford dual functionality of coupled fluorescence emission and dielectricity. Incorporating spin crossover motifs into mechanically interlocked molecules offers various switchable properties. Here, the authors report two FeII catenated metal-organic frameworks that exhibit spin dependent luminescence and dielectric switching. [ABSTRACT FROM AUTHOR]

Light-induced polarization switchable molecular materials have attracted attention for decades owing to their potential remote manipulation and ultrafast responsiveness. Here we report a valence tautomeric (VT) complex with an enantiopure chiral ligand. By a suitable choice of counter anions, a significant improvement in photoconversion has been demonstrated, leading to novel photo-responsive polarization switching materials. [ABSTRACT FROM AUTHOR]

A pair of undescribed dihydrobenzofuran neolignan enantiomers, (+/−)-phybrenan A (1a/1b), two new benzofuran neolignans, phybrenan B and C (2 and 3), along with four known neolignans (4 − 7) were obtained from the plants of Phyllanthodendron breynioides P. T. Li. The planar structures of all isolates were demonstrated by the analysis of detailed spectroscopic evidence (NMR, HRMS, and IR), and the absolute configurations of novel neolignans were elucidated by combined calculated and experimental ECD data analysis. The neuroprotective activities of all benzofuran neolignans against sodium nitroprusside (SNP)-induced cell death were examined in rat pheochromocytoma PC12 cells. The results exhibited that three compounds (4 − 6) possessed remarkable neuroprotective activities at 10 µM, better than the positive drug edaravone. [ABSTRACT FROM AUTHOR]

In China, there is only one certified reference material (CRM) of organochlorine pesticide (OCPs) and three CRMs of polychlorinated biphenyls (PCBs) in soil. Internationally, there is one CRM of OCPs and two CRMs of PCBs in soil in Europe. The National Institute of Standards and Technology (NIST) of the USA, the National Metrology Institute of Japan (NMIJ), and the International Atomic Energy Agency (IAEA) have developed sediment CRMs for OCPs, PCBs and polycyclic aromatic hydrocarbons (PAHs). However, the matrix and contamination levels of CRMs of OCPs and PCBs do not match with the actual pollution of soil in China.In this study, according to the distribution of soil types, pollution levels of organic compounds and quality control requirements of soil samples, the typical soils were collected as candidates in China. According to the primary standard material specification, 6 CRMs of OCPs and PCBs in different soil types (GBW07469-GBW07474) have been developed. Based on the results from traditional methods including Gas Chromatography-Electron Capture Detector (GC-ECD), Gas Chromatography-Mass Spectrometry (GC-MS), Gas Chromatography-Tandem Mass Spectrometry (GC-MS/MS) and new techniques of Gas Chromatography-Isotope Dilution Mass Spectrometry (GC-IDMS), Gas Chromatography-Isotope Dilution Tandem-Mass Spectrometry (GC-IDMS-MS), certified values and expanded uncertainty for 8 OCPs and 7 PCBs are given. Meanwhile, a GC-ID-HRMS method was used to determine PCBs in candidate reference materials for comparison and validation. These CRMs cover most Chinese soil types, including cinnamon, paddy, yellow and meadow soil. The certified values of OCPs and PCBs in soils range from 3.9 μg/kg to 2.31 mg/kg. As the soils used for CRMs were collected from the field, the matrix and contamination levels of OCPs and PCBs are consistent with actual soils. The CRMs can be used in the quality control of OCPs and PCBs detection in soils of different pollution levels in different regions.

According to the proficiency testing program (CNCA-13-A14) held by the National Certification and Accreditation Committee of China (CNCA), analytical data for W, Sn, Cu, Pb, Zn, Mo, Sb and Bi in tungsten and tin ores provided by 58 analytical laboratories in 30 provinces and autonomous regions were evaluated. Robust statistics, an international general statistical method, and Z-scores were used for evaluating the testing ability of the laboratories. According to the criteria for satisfactory results (Z-scores ≤2), the overall satisfaction rate for 58 laboratories was 88% (51 laboratories) and 12% of laboratories had suspect and outlier results. As a whole, the satisfaction rate for Sb, Pb and Zn in tungsten and tin ores was high, among which all of the analytical results of Zn in Tin Ores were satisfactory; results of W, Bi were slightly worse. Results of tungsten were better than those for tin ores. Moreover, the determination methods in all laboratories and the reasons for the outlier results were analyzed. The results of proficiency testing were objectively reflected for the testing ability and technical levels of the geoanalytical laboratory. Due to the determined gap among different laboratories, it was suggested that proficiency testing should be held periodically to improve the analytical ability and ensure the reliability of analytical data.

To alleviate the energy and environmental crisis, in the last decades, energy harvesting by utilizing optical control has emerged as a promising solution. Here we report a polar crystal that exhibits photoenergy conversion and energy storage upon light irradiation. The polar crystal consists of dinuclear [CoGa] molecules, which are oriented in a uniform direction inside the crystal lattice. Irradiation with green light induces a directional intramolecular electron transfer from the ligand to a low-spin CoIII centre, and the resultant light-induced high-spin CoII excited state is trapped at low temperature, realizing energy storage. Additionally, electric current release is observed during relaxation from the trapped light-induced metastable state to the ground state, because the intramolecular electron transfer in the relaxation process is accompanied with macroscopic polarization switching at the single-crystal level. It demonstrates that energy storage and conversion to electrical energy is realized in the [CoGa] crystals, which is different from typical polar pyroelectric compounds that exhibit the conversion of thermal energy into electricity. Energy harvesting by utilizing optical control has emerged as a promising solution to alleviate energy and environmental crisis. However, it is challenging to realise nano-scale energy storage and conversion in the same material. Here the authors report a nonferroelectric molecular [CoGa] crystal that uses light as an external stimulus to exhibit photoenergy conversion and energy storage properties. [ABSTRACT FROM AUTHOR]

The majority of fat and impurities in animal tissues influence the analysis result for low concentration organic compounds. To overcome this issue, the animal sample was extracted by accelerated solvent extraction (ASE) with methylene chloride/acetone (V:V=1:1), which reduced the co-extraction lipids during the extraction process. Gel Permeation Chromatography (GPC) combined with solid phase extraction (SPE) was applied to remove lipids from the sample solution. The GPC can remove most of the macromolecular lipids in samples, and the SPE with florisil can sufficiently reduce fat and small molecule impurity. The accuracy and sensitivity of the method can be improved by this pretreatment process. The compounds, including 17 organochlorinated pesticides and 7 indicator polychlorinated biphenyls in animal tissue, can be simultaneously analysed by Gas Chromatography Mass Spectrometry. The recoveries of 25 of the target compounds were in the range of 81.6%-113.4% and the method detection limits for dry samples were 1.02-3.59 ng/g. These results were superior to those of the national standard. This method improved the purification effect of animal samples, reduced the method detection limit, and enhanced the accuracy. It can be used to quickly and accurately determine the low content of persistent organic pollutants in animals.

The pollution of grains is growing worse due to the soil environment being polluted. The pre-treatment for organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) detected in samples of rice, wheat, corn and soybean is a complicated process with a large amount of solvents, easily leading to volatile compound loss and effects on the accuracy of the analysis. Therefore, choosing a suitable extraction and purification method is very important to the determination of 25 OCPs and PCBs in grains with Gas Chromatography. In this paper, the extraction and purification procedures of this method have been improved greatly by optimizing the parameters of accelerated solvent extraction (ASE) and comparing gel permeation chromatography (GPC) and solid phase extraction (SPE) are described. In addition to soy products, such as soybean and black bean samples needed to be purified by GPC and SPE, most of the rice, wheat, corn and other cereal samples are purified by SPE alone. The sample was extracted with dichloromethane and acetone (V:V=1:1) by ASE (Florisil clean up in the extraction cell), cleaned up by SPE with only 9 mL n-hexane/ethylacetate (V:V=1:1) to recover all the target compounds. The problems of using a large amount of organic reagent and the highly toxic reagent were overcome. The method detection limits of 17 OCPs and 8 PCBs ranged from 0.07 to 0.3 μg/kg, better than the index in national standard method. The average recoveries of 25 OCPs and PCBs were 71.0%-112.0% in the solutions of low and high level contents of 0.69 μg/kg and 5.52 μg/kg. The relative standard deviations (RSDs) for all the compounds were 3.6%-16.7% (n=7). It was confirmed that the method was accurate and credible through determination of spiked rice samples and other grain samples. Compared with traditional methods, this method is simple and convenient to conduct with the advantages of high efficiency, rapidity and low cost. Thereby, it is feasible for the simultaneous determination of OCPs and PCBs in different kinds of grain samples.