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1.
Inorg Chem ; 2020 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-32039592

RESUMO

The detection and reusage of transition-metal ions play a crucial role in human health and environmental protection. Recently, various analytical methods and substances have been successfully applied to probe or sense silver ions; however, rare representative examples have been presented regarding the simultaneous detection of silver and silver recycling with the elemental silver powder form. Herein, an unparalleled sensing mechanism for silver ions and recycling silver in its elemental form is exemplified by a fluorescent trinuclear zinc coordination cluster possessing the dual function of colorimetric sensing of silver and responding cupric ions. A Schiff-base-based trinuclear zinc coordination cluster, 1, with formula Zn3(L1)2(CH3COO)2(H2O)2, has been successfully synthesized by the initial exploration of multidentate ligand H2L1-((E)-2,4-di-tert-butyl-6-((2-hydroxy-3-methoxybenzy-lidene)amino)phenol) with various metal ions under self-assembly reactions. Complex 1 is highly fluorescent in solution and as a solid, in addition to acting as a fluorescence sensor toward AgI in ethanol media. Compound 1 displays distinctive sensing of AgI through the fluorescence quenching effect at 576 nm and signal augment at 446 nm over 11 kinds of cations in the absence of interference. The proposed sensing mechanism is attributed to the ligands in 1 which interact with AgI; the ligands undergo oxidation cyclization reaction, leading to the formation of 2 with the formula Zn3(L2)4(CH3COO)2·2CH3CH2OH·H2O, and AgI reduction to elemental Ag powder. Compound 1 presents specific selectivity and sensitivity for AgI in ethanolic solution with a detection limit of 0.1722 µM. The orange color of 1 changes to colorless during the mixing of a small amount of AgI, revealing its potential practical application in naked-eye detection of AgI. Furthermore, 2 exhibits obvious fluorescence emission at 448 nm (λex = 380 nm) and selectively responds to CuII over 11 kinds of metal ions with the fluorescence "turn-off" owing to the formation of 3 in ethanolic solution; it also has a detection limit of 0.0226 µM.

2.
Dalton Trans ; 49(7): 2300-2307, 2020 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-32016242

RESUMO

In the presence of different nitrogen-rich ligands, two energetic MOFs with formulas [Ag(tza)]n (1) and [Ag(atza)]n (2) (Htza = tetrazole-1-acetic acid and Hatza = (5-amino-1H-tetrazole-1-yl) acetic acid) were successfully synthesized and characterized. X-ray single crystal structure analysis shows that both 1 and 2 have 2D layer-like topologies. The experimental and theoretical evaluations reveal the promising properties of both energetic compounds, such as prominent heats of detonation, high thermal stabilities, good sensitivities and excellent detonation performances. In contrast to 1, interestingly, the introduction of the amino group in 2 leads to various coordination modes of the ligands and different stacking patterns of the frameworks, resulting in the observation of the shorter Ag-O, Ag-Ag, C-N, N-N, and N[double bond, length as m-dash]N bond lengths in 2. Consequently, 2 features superior heats of detonation and thermostability compared to 1. The nonisothermal thermokinetic parameters are obtained by using the Kissinger and Ozawa methods, while the standard molar enthalpies of formation are calculated from the determination of constant volume combustion energies. In addition, both compounds were explored as practical additives to promote the thermal decomposition of ammonium perchlorate (AP). This work may provide an effective approach for manipulating the energetic properties and thermostability of high-energy compounds via the perturbation of energetic groups.

3.
Chemistry ; 2020 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-32074403

RESUMO

The first isolable silylene-germylene complex 5 was assembled by a salt metathesis reaction between the germylene anion 3 and N-heterocyclic chlorosilylene 4, and structurally characterized. The central structure of 5 demonstrates a remarkable gauche-bent geometry with the silylene and germylene units, which are interconnected by a Si-Ge bond with the distance of 2.4498(9) Å. This value is not only perceptibly longer than the distances known in doubly bonded germasilenes, and also slightly longer than those in germylsilanes. The DFT calculations on 5 confirmed a nearly nonpolar SiI -GeI single bond nature and its bonding orbital, as well as the aromatiity of C3NGe-rings in 3 and 5. The latter increases molecular stability of 3 and 5, and makes the preparation of silylene-germylene complex 5 a reality.

4.
Sci Rep ; 10(1): 525, 2020 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-31949196

RESUMO

Begomoviruses can modify their transmission vector, Bemisia tabaci, to benefit their spread, although this may not always be the case. Here, the new begomovirus Ramie mosaic virus (RaMoV) and its vector B. tabaci MED, which is dominant in China and many regions of the world, were used as a model to examine direct and indirect interaction and virus transmission by B. tabaci MED of different sexes. No significant direct or indirect effects of RaMoV were observed in B. tabaci MED females, although RaMoV could shorten the life span of B. tabaci MED females by up to 4 days. A test of RaMoV transmission by different sexes of B. tabaci MED showed that there was higher virus transmission efficiency by females than males. Overall, RaMoV is transmitted by B. tabaci MED in a sex-dependent manner, and further research is needed to uncover the mechanism of the difference in RaMoV transmission by different sexes of B. tabaci.

5.
J Exp Bot ; 71(1): 204-218, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31587067

RESUMO

Meiotic recombination plays a central role in maintaining genome stability and increasing genetic diversity. Although meiotic progression and core components are widely conserved across kingdoms, significant differences remain among species. Here we identify a rice gene ABERRANT GAMETOGENESIS 1 (AGG1) that controls both male and female gametogenesis. Cytological and immunostaining analysis showed that in the osagg1 mutant the early recombination processes and synapsis occurred normally, but the chiasma number was dramatically reduced. Moreover, OsAGG1 was found to interact with ZMM proteins OsHEI10, OsZIP4, and OsMSH5. These results suggested that OsAGG1 plays an important role in crossover formation. Phylogenetic analysis showed that OsAGG1 is a plant-specific protein with a highly conserved N-terminal region. Further genetic and protein interaction analyses revealed that the conserved N-terminus was essential for the function of the OsAGG1 protein. Overall, our work demonstrates that OsAGG1 is a novel and critical component in rice meiotic crossover formation, expanding our understanding of meiotic progression. This study identified a plant-specific gene ABERRANT GAMETOGENESIS 1 that is required for meiotic crossover formation in rice. The conserved N-terminus of the AGG1 protein was found to be essential for its function.

6.
J Mater Chem B ; 8(3): 515-522, 2020 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-31840711

RESUMO

The development of magnetic iron oxide nanoparticles with novel topological magnetic domain structures, such as the vortex-domain structure, is a promising strategy for improving the application performance of conventional superparamagnetic iron oxides while maintaining their good biocompatibility. Here, we fabricated a new kind of magnetic-vortex nanoparticles, i.e., ellipsoidal magnetite nanoparticles (EMPs), for cancer magnetic hyperthermia. The magnetization configurations and switching behaviours of the EMPs were analyzed by analytical simulations and Lorentz TEM, demonstrating the magnetic vortex structures of both single and coupled EMPs. The EMP treatment of 4T1 cells exposed to an alternating magnetic field (AMF) induced a significant decrease in the cell viability by ∼51.5%, which indicated a much higher cytotoxic effect in comparison with commercial superparamagnetic iron oxides (Resovist, ∼12.0%). In addition, the in vivo high efficacy of 4T1 breast tumor inhibition was also achieved by using EMP-mediated magnetic hyperthermia. Our results not only provide a new type of magnetic-vortex nanoparticles for efficient hyperthermia but also enrich the family of magnetic iron oxide nanoparticles for various biomedical applications.

7.
Dalton Trans ; 49(3): 808-816, 2020 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-31854400

RESUMO

Complexation of dysprosium(iii) ions with a multidentate hydrazone ligand, N-[(E)-pyridin-2-ylmethylideneamino]pyridine-2-carboxamide (L), in the presence of different ß-diketonate coligands, leads to the formation of two novel DyIII dimers, with formulas Dy2(BTFA)4(L)2 (1) and Dy2(TTA)4(L)2 (2) (BTFA = 3-benzoyl-1,1,1-trifluoroacetone and TTA = 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedionate). They exhibit slightly different coordination geometries around DyIII centers and discrepant binuclear motifs - as a result of altering the ß-diketonate coligands - which has an impact on the magnetic interactions between metal centers, the local tensor of anisotropy on each DyIII site and their relative orientations, therefore contributing to distinct magnetization dynamics. Compared to 2, complex 1 exhibits a more significant slow magnetic relaxation of SMM behavior in the absence of a dc field. The QTM effect is effectively repressed under a static field, resulting in the energy barriers of 57 K for 1 and 38 K for 2. Ab initio calculations clarify that, strong single-ion magnetic anisotropies exist in both complexes, whereas intermetallic ferromagnetic interaction and antiferromagnetic interaction are observed in 1 and 2, respectively, therefore resulting in dissimilar magnetization dynamics.

8.
Biosens Bioelectron ; 148: 111795, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31665673

RESUMO

In this work, a high-efficiency electrochemiluminescence (ECL) ternary system was constructed for ultrasensitive assay of insulin based on hollow porous graphitic carbon nitride (HP-C3N4) as novel luminophore, S2O82- as coreactant and tri-metallic AuPtAg as coreaction accelerator. Specifically, in comparison with C3N4-based bulk nanomaterials, the as-prepared HP-C3N4 exhibits high luminous efficiency though decreased inner filter effect and minimized inactive ECL emitter. Noteworthy, tri-metallic AuPtAg, possessing the superiority of Au, Pt and Ag, was first used as coreaction accelerator to significantly enhance ECL intensity of HP-C3N4 and S2O82-. As a consequence, with the resultant ECL ternary (HP-C3N4/S2O82-/AuPtAg) system as aptasensing platform, a high-intense initial ECL signal was achieved. Subsequently, ferrocene-labeled quenching probe (Fc-HP2) as ECL quencher was used to quench the initial signal and achieve the low-background noise. Eventually, in the presence of insulin, the target-induced triple-helix molecular switch and Nb.BbvCI-assisted DNA walker amplification were executed to recover a strong ECL signal by releasing Fc-HP2 from the electrode surface. As expected, the constructed aptasensor presents an excellent sensitivity and selectivity for detecting insulin range from 0.05 pg mL-1 to 100 ng mL-1 with a detection limit of 17 fg mL-1. This work provides a new avenue for developing highly efficient HP-C3N4 based ECL ternary system as well as ultrasensitive ECL aptasensors for bioanalysis.

9.
Pest Manag Sci ; 2019 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-31840379

RESUMO

BACKGROUND: Ecosystem services are key to human survival. In agriculture, they offer potential to intensify production while reducing reliance on hazardous inputs, including pesticides. Nectar plants can nourish natural enemies of pests and thereby promote the ecosystem service of biological control. To date, however, the selection of optimal plants has been reliant on laborious testing of multiple candidate species for use in each new agroecosystem. We report a hybrid meta-analysis of published literature, employing Bayesian network analysis. RESULTS: The hybrid meta-analysis identified the particular plant and parasitoid traits that were most predictive of promoted or suppressed parasitoid longevity. Integrating trait effects identified a combination of plant-parasitoid traits that had the highest impact on parasitoid longevity: compound umbel or raceme inflorescence form and shallow corolla, together with high potential fecundity of the parasitoid. CONCLUSION: Unlike earlier analyses focusing on taxonomic categories, we analysed effect sizes in relation to the ecological traits of parasitoids and plants. This generated the first generalizable guidelines for selecting nectar plants as well as appropriate parasitoid targets for the enhancement of biological control. Within the guidelines, optimal outcomes resulted when plants with compound umbel or raceme inflorescences and shallow corollas were combined with fecund parasitoids. More widely, this type of ecological trait-based meta-analysis opens a new avenue for optimising the delivery of other types of ecosystem services. This article is protected by copyright. All rights reserved.

10.
Chem Commun (Camb) ; 55(97): 14661-14664, 2019 Dec 18.
Artigo em Inglês | MEDLINE | ID: mdl-31746846

RESUMO

We report the first bromine-bridged dinuclear [Dy(Cy3PO)2(µ-Br)(Br)2]2·2C7H8 single-molecule magnet with an effective energy barrier of 684 K and magnetic hysteresis below 3 K. The asymmetric DyIII centres present two unique stereoisomeric octahedral coordination environments depending on the cis/trans disposition of the Cy3PO ligands, leading to the orthogonality of the easy magnetic axes that annihilates the dipolar interactions.

11.
J Mater Chem B ; 7(46): 7406-7414, 2019 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-31710067

RESUMO

Photoimmunotherapy has attracted much attention recently for the treatment of metastatic tumors. The development of smart nanocomposites for imaging-guided therapies is needed to improve the efficacy of cancer treatment. Herein, a PEGylated nanocomposite was developed for photothermal-immunotherapy. In particular, this nanocomposite was formulated by hybridizing Fe3O4 nanoparticles (FNPs) with reduced-graphene oxide (rGO) through electrostatic interaction, modified by PEG-NH2 on the surface of FNPs/rGO. The FNPs/rGO-PEG nanocomposites are excellent agents for photothermal therapy (PTT) under irradiation by an 805 nm laser. This nanocomposite could promote the activity of the host antitumor immune response efficiently because of the reduction of tumor-associated macrophages by the incorporation of FNPs. In our experiments, we observed FNPs/rGO-PEG based PTT induced immunogenic cell death accompanied by the release of danger-associated molecular patterns. We also found that FNPs/rGO-PEG + laser irradiation of animal tumors could activate dendritic cells (DCs) in tumor draining lymph nodes. In vivo antitumor studies revealed that FNPs/rGO-PEG nanocomposites, when combined with laser irradiation, could result in desirable photothermal effects and destroy primary tumors. Moreover, intratumoral injection of FNPs/rGO-PEG nanocomposites into 4T1 orthotopic mouse breast tumors, in combination with near-infrared laser irradiation, significantly increased the median survival time of tumor-bearing animals. FNPs/rGO-PEG nanocomposites could also be used for magnetic resonance imaging, which may lead to a MRI-guided photothermal-immunotherapy for metastatic cancers. This study could lead to a cancer treatment strategy that combines PTT with immunotherapies using FNPs/rGO-PEG nanocomposites.

12.
Dalton Trans ; 48(43): 16384-16394, 2019 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-31633710

RESUMO

A family of new structurally manipulable pentagonal-bipyramidal (PBP) DyIII SMMs, with formulas [Dy(Hbpen)(Cl)3] (1), [Dy(Hbpen)Cl(OPhBr2NO2)2] (2), [Dy(Hbpen)(OPhCl2NO2)3] (3) and [Dy(Mbpen)(Cl)3] (1CH3), were controllably prepared based on a H-substituted amine-based ligand N,N'-bis(2-pyridylmethyl)-ethylenediamine (Hbpen) or a CH3-substituted amine-based ligand N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)-ethylenediamine (Mbpen) and are compared with the reported imine-based DyIII analogues (1'-3'). Upon fine-modulating the type of nitrogen donor on the pentagon plane, the electronic effect is efficiently implemented to significantly modify the magnetic anisotropy and SMM behavior of PBP complexes. Notably, the amine-based 2 shows a three-fold improved energy barrier and an observable hysteresis opening up to 3 K. 1 and 1CH3 exhibit slower relaxation and enhanced anisotropy compared to the imine-based analogue, accompanied by the reorientation of magnetic easy axes. Conversely, poor magnetic properties are observed in 3 after the reduction of imine. The changes in SMM behavior and uniaxial anisotropies are rationalized by both experimental and theoretical studies. The H-substituted amine has formally a larger magnitude of negative charge than imine due to the polarized N-H σ bond. However the repulsion generated by the sp3 N of amine towards the DyIII ion is also affected by the orientation of lone pair electrons. The present work provides a feasible way to rationally optimize the SMM performance of DyIII complexes, highlighting the importance of the electronic properties of an equatorial donor in controlling the quantum tunneling and the magnetic relaxation of PBP DyIII-SMMs.

13.
Sci Total Environ ; 693: 133440, 2019 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-31374492

RESUMO

Point sources are important routes through which pollutants enter rivers. It is important to identify the characteristics of and trace the origins of water pollutants. In this study, an artificial intelligence system called the integrated long short-term memory network (LSTM), using cross-correlation and association rules (Apriori), was used to identify the characteristics of water pollutants and trace industrial point sources of pollutants. Water quality monitoring data from Shandong Province, China, were used to verify the applicability of the artificial intelligence system using a cross-correlation method to develop a water quality cross-correlation map. The map was used to identify highly correlated pollutants affecting water quality, then the association rules (Apriori) were used to track the pollutants to industries common in the study area. The highly correlated water pollutants and relevant industries were used as inputs for the LSTM to determine how well the LSTM traced sources of water pollutants. The results showed that (1) changes in water quality were affected in different ways by different industries and different distributions and production cycles of the pollutant point sources; (2) water quality correlation maps can be used to identify regular and abnormal fluctuations in point source pollutant emissions by identifying changes in water quality characteristics and frequent itemsets in water quality indices can be used to trace the industries that most strongly affect water quality; and (3) the LSTM accurately traced point sources of future changes in water quality. In conclusion, the artificial intelligence scheme described here can be applied to aquatic systems.

14.
J Environ Manage ; 248: 109259, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31325792

RESUMO

Lake eutrophication is characterized by a variety of indicators, including nitrogen and phosphorus concentrations, chemical oxygen demand, chlorophyll levels, and water transparency. In this study, a multidimensional similarity cloud model (MSCM) is combined with a random weighting method to reduce the impacts of random errors in eutrophication monitoring data and the fuzziness of lake eutrophication definitions on the consistency and reliability of lake eutrophication evaluations. Measured samples are assigned to lake eutrophication levels based on the cosine of the angle between the cloud digital characteristics vectors of each sample and those of each eutrophication grade. To field test this method, the eutrophication level of Nansi Lake in Shandong Province was evaluated based on monitoring data collected in 2009-2016. Results demonstrate that, in 2009 and in 2011-2015, the upper lake of Nansi Lake exhibited moderate eutrophication while the lower lake exhibited mild eutrophication. In 2010, 2016, elevated concentrations of total nitrogen and total phosphorus led to an increase in the eutrophication level of the lower lake, matching that of the upper lake. Based on the results of these field tests, we conclude that the MSCM presented in this study provides a more flexible and effective method for evaluating lake eutrophication data than the existing multidimensional normal cloud model.


Assuntos
Monitoramento Ambiental , Lagos , China , Clorofila , Eutrofização , Nitrogênio , Fósforo , Reprodutibilidade dos Testes
15.
PeerJ ; 7: e6951, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31149404

RESUMO

Resuscitation-promoting factors (Rpf) are a class of muralytic enzymes, which participate in recovery of dormant cells and promoting bacteria growth in poor media. In the present study the expression vector of the rpf-1 gene from an oil-degrading bacterium Rhodococcus erythropolis KB1 was constructed and expressed in Escherichia coli. The expressed protein was purified by Ni2+-affinity chromatography, and showed muralytic activity when measured with 4-methylumbelliferyl-ß-D-N,N',N″-triacetyl chitotrioside as substrate. Addition of purified Rpf-1 to R. erythropolis culture efficiently improved bacterial cell growth. The purified protein also increased resuscitation of viable but nonculturable cells of R. erythropolis to culturable state. The conserved amino acid residues including Asp45, Glu51, Cys50, Thr60, Gln69, Thr74, Trp75 and Cys114 of the Rpf-1 were replaced with different amino acids. The mutant proteins were also expressed and purified with Ni2+-affinity chromatography. The muralytic activities of the mutant proteins decreased to different extents when compared with that of the wild type Rpf-1. Gln69 was found to play the most important role in the enzyme activity, substitution of Gln69 with lysine (Q69K) resulted in the greatest decrease of muralytic activity. The other amino acid residues such as Asp45, Glu51, Cys50 and Cys114 were also found to be very important in maintaining muralytic activity and biological function of the Rpf-1. Our results indicated that Rpf-1 from R. erythropolis showed muralytic activities and weak protease activity, but the muralytic activity was responsible for its growth promotion and resuscitation activity.

16.
Inorg Chem ; 58(12): 8198-8207, 2019 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-31185542

RESUMO

Host-Guest interaction is crucial to the sensitivity of heterogeneous sensors. Here, a series of isomorphic three-dimensional lanthanide metal-organic frameworks (Ln-MOFs), [Ln(TCBA)(H2O)2]2·DMF [H3TCBA = tris(3'-carboxybiphenyl)amine; Ln = Tb (1), Eu (2), and Gd (3); DMF = dimethylformamide] was synthesized and characterized, in which the propeller-like TCBA3- ligands adopt special torsional link between Tb(III) ions to form one-dimensional triangular channels. Optical experiments show that 1 exhibits bright green luminescence with an overall quantum yield of 26%, a 5D4 lifetime of 478 µs, and can act as an excellent heterogeneous fluorescent sensor to detect 2,4,6-trinitrophenol (TNP) explosive with an extremely low detection limit of 1.64 ppb. Because the confined channels within 1 exhibit matched dimensions toward TNP and feature multiple guest-response sites including rich π-conjugated groups, electron-donating N centers, and open metal nodes, strong host-guest interactions between 1 and TNP are captured and accurately determined by online microcalorimetry, which provides a distinctive thermodynamic perspective to understand the heterogeneous sensing behaviors. Additionally, the finely modulated heterometallic isomorphism [Tb0.816Eu0.184(TCBA)(H2O)2]2·DMF emits bright white light when excited at 380 nm and could potentially be used as single-phase white light-emitting diode phosphors materials.

17.
Artigo em Inglês | MEDLINE | ID: mdl-31216617

RESUMO

Spatial patterns of water quality trends for 45 stations in control units of the Shandong Province, China during 2009-2017 were examined by a non-parametric seasonal Mann-Kendall's test (SMK) for dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), permanganate index (CODMn), total phosphorus (TP) and ammonia nitrogen (NH3-N). The DO concentration showed significant upward trends at approximately half of the stations, while other parameters showed significant downward trends at more than 40% of stations. The stations with downward trends presented significant spatial autocorrelation, and were mainly concentrated in the northwest and southwest regions. The relationship between the landscape characteristics and water quality was explored using stepwise multiple regression models, which indicated the water quality was better explained using landscape pattern metrics compared to the percentage of land use types. Decreased mean patch area and connectedness of farmland will promote the control of BOD, COD and CODMn, whereas the increased landscape percentage of urban areas were not conducive to the water quality improvement, which suggested the sprawling of farmland and urban land was not beneficial to pollution control. Increasing the grassland area was conducive to the reduction of pollutants, while the effect of grassland fragmentation was reversed.


Assuntos
Poluentes Químicos da Água/análise , Agricultura , Amônia/análise , Análise da Demanda Biológica de Oxigênio , China , Monitoramento Ambiental , Pradaria , Oxigênio/análise , Fósforo/análise , Análise Espacial , Urbanização , Qualidade da Água
18.
Dalton Trans ; 48(22): 7844-7852, 2019 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-31073565

RESUMO

We showcase the coordination anion substitution effect on the relaxation dynamics of defect dicubane Zn2Dy2 tetranuclear clusters. On utilization of the coordination similarity of acetate and nitrate anions, we successfully isolated two defect dicubane Zn2Dy2 tetranuclear clusters with formulas [Zn2Dy2(L)4(NO3)2(CH3OH)2]·2CH3COCH3 (1) and [Zn2Dy2(L)4(CH3COO)2(CH3CH2OH)2]·4CH3COCH3 (2), where L denotes the fully deprotonated H2L ligand (E)-4-(tert-butyl)-2-((2-hydroxy-3-methoxybenzylidene)amino)phenol. Such a subtle change in the coordination anion around the DyIII site imposes a significant effect on the distinct relaxation dynamics in 1 and 2. Their magnetic properties were characterized through SQUID magnetometry and theoretical calculations to determine the effective energy barrier, energy levels, magnetic anisotropy and intracluster magnetic exchange coupling interactions. Both tetramers display frequency dependence of the out-of-phase ac magnetic susceptibility signal under zero applied dc field associated with single-molecule magnetic behaviour. The effective energy barriers of 1 and 2 are 108 and 40 cm-1, respectively. Theoretical calculations suggest that the different relaxation dynamics between them are mainly ascribed to the variation of the coordination anion around the DyIII site.

19.
ACS Appl Mater Interfaces ; 11(9): 9233-9238, 2019 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-30762334

RESUMO

It is an enormous challenge to construct high-energy-density materials meeting simultaneously requirements of high energy and excellent stability. In this work, the reaction of a Ag(I) ion with a nitrogen-rich ligand, 1 H-tetrazole-5-acetic acid (H2tza), leads to a novel Ag7-cluster metal-organic framework, [Ag7(tza)3(Htza)2(H2tza)(H2O)] (1), with remarkable high-energy content, stability, and insensitivity. Dramatically, the heating-dehydrated process of 1 produces a new stable energetic material, [Ag7(tza)3(Htza)2(H2tza)] (1a), which features superior energy and undiminished safety performance compared to those of 1.

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