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1.
Angew Chem Int Ed Engl ; 63(20): e202401766, 2024 May 13.
Artículo en Inglés | MEDLINE | ID: mdl-38477673

RESUMEN

Solar-thermal water evaporation is a promising strategy for clean water production, which needs the development of solar-thermal conversion materials with both high efficiency and high stability. Herein, we reported an ultra-stable cobalt(II)-organic assembly NKU-123 with light-generated radicals, exhibiting superior photothermal conversion efficiency and high stability. Under the irradiation of 808 nm light, the temperature of NKU-123 rapidly increases from 25.5 to 215.1 °C in 6 seconds. The solar water evaporator based on NKU-123 achieves a high solar-thermal water evaporation rate of 1.442 and 1.299 kg m-2 h-1 under 1-sun irradiation with a water evaporation efficiency of 97.8 and 87.9 % for pure water and seawater, respectively. A detailed mechanism study revealed that the formation of light-generated radicals leads to an increase of spin density of NKU-123 for enhancing the photothermal effect, which provides insights into the design of highly efficient photothermal materials.

2.
Angew Chem Int Ed Engl ; 63(6): e202318722, 2024 Feb 05.
Artículo en Inglés | MEDLINE | ID: mdl-38086781

RESUMEN

The rapid and accurate sensing of p-xylene, an essential raw material with a multi-billion-dollar market, in xylene mixture is of great significance in industry; however, the highly similar molecular structures, energy levels, and spectral characteristics of xylene isomers make the selective recognition extremely challenging. Metal-organic frameworks (MOFs) exhibiting tailorable pores and potential binding sites provide prospects for xylene sensing but a comprehensive understanding of the pore effect is still elusive, primarily due to the intricacies involved in the sensing process. Herein, we reported a robust bilanthanide MOF NKU-999-EuTb with precisely engineered pores to accommodate p-xylene, of which the binding sites were confirmed by single crystal X-ray diffraction and dynamic magnetic susceptibilities. NKU-999-EuTb exhibits high-performance in selective recognition for p-xylene towards its isomers. Through a systematical study, it was revealed that absorbing p-xylene into the pores governs the sensing performance. This work provides insights for developing advanced sensing materials for complex isomers.

3.
Int J Mol Sci ; 24(23)2023 Nov 24.
Artículo en Inglés | MEDLINE | ID: mdl-38069041

RESUMEN

Gastrointestinal cancer is a common clinical malignant tumor disease that seriously endangers human health and lacks effective treatment methods. As part of the innate immune defense of many organisms, antimicrobial peptides not only have broad-spectrum antibacterial activity but also can specifically kill tumor cells. The positive charge of antimicrobial peptides under neutral conditions determines their high selectivity to tumor cells. In addition, antimicrobial peptides also have unique anticancer mechanisms, such as inducing apoptosis, autophagy, cell cycle arrest, membrane destruction, and inhibition of metastasis, which highlights the low drug resistance and high specificity of antimicrobial peptides. In this review, we summarize the related studies on antimicrobial peptides in the treatment of digestive tract tumors, mainly oral cancer, esophageal cancer, gastric cancer, liver cancer, pancreatic cancer, and colorectal cancer. This paper describes the therapeutic advantages of antimicrobial peptides due to their unique anticancer mechanisms. The length, net charge, and secondary structure of antimicrobial peptides can be modified by design or modification to further enhance their anticancer effects. In summary, as an emerging cancer treatment drug, antimicrobial peptides need to be further studied to realize their application in gastrointestinal cancer diseases.


Asunto(s)
Antineoplásicos , Neoplasias Gastrointestinales , Neoplasias Gástricas , Humanos , Péptidos Antimicrobianos , Péptidos Catiónicos Antimicrobianos/farmacología , Péptidos Catiónicos Antimicrobianos/uso terapéutico , Péptidos Catiónicos Antimicrobianos/química , Neoplasias Gastrointestinales/tratamiento farmacológico , Antineoplásicos/farmacología , Antineoplásicos/uso terapéutico , Antineoplásicos/química , Neoplasias Gástricas/tratamiento farmacológico , Antibacterianos/farmacología
4.
Inorg Chem ; 59(17): 11930-11934, 2020 Sep 08.
Artículo en Inglés | MEDLINE | ID: mdl-32805992

RESUMEN

A series of 3D homologous metal-organic frameworks, [M(H0.5L)2] [M = Dy (1), Ho (2), Yb (3), Sm (4), Gd (5), and Y (6); H2L = 5-(1H-imidazol-1-yl)isophthalic acid], were isolated. In these complexes, the metal centers behave as hexacoordinated environments with distorted octahedral geometries, which is unusual in the lanthanide series, linking to each other and producing a fascinating 3D architecture. Magnetically, 1 features a field-driven dual-magnetic relaxation, which is rarely observed in high-dimensional coordination polymers. Analysis on the dilution sample (1@Y) and ab initio calculation unveil that the thermally assisted slow relaxation is mostly caused by the single-ion magnetism of DyIII itself.

5.
Mol Cell ; 48(2): 219-30, 2012 Oct 26.
Artículo en Inglés | MEDLINE | ID: mdl-22959273

RESUMEN

We describe the discovery of sno-lncRNAs, a class of nuclear-enriched intron-derived long noncoding RNAs (lncRNAs) that are processed on both ends by the snoRNA machinery. During exonucleolytic trimming, the sequences between the snoRNAs are not degraded, leading to the accumulation of lncRNAs flanked by snoRNA sequences but lacking 5' caps and 3' poly(A) tails. Such RNAs are widely expressed in cells and tissues and can be produced by either box C/D or box H/ACA snoRNAs. Importantly, the genomic region encoding one abundant class of sno-lncRNAs (15q11-q13) is specifically deleted in Prader-Willi Syndrome (PWS). The PWS region sno-lncRNAs do not colocalize with nucleoli or Cajal bodies, but rather accumulate near their sites of synthesis. These sno-lncRNAs associate strongly with Fox family splicing regulators and alter patterns of splicing. These results thus implicate a previously unannotated class of lncRNAs in the molecular pathogenesis of PWS.


Asunto(s)
Síndrome de Prader-Willi , Empalme del ARN/genética , ARN Largo no Codificante , ARN Nucleolar Pequeño , Secuencia de Bases , Línea Celular , Nucléolo Celular/genética , Nucléolo Celular/metabolismo , Cuerpos Enrollados/genética , Cuerpos Enrollados/metabolismo , Regulación de la Expresión Génica , Humanos , Intrones , Datos de Secuencia Molecular , Síndrome de Prader-Willi/genética , Síndrome de Prader-Willi/metabolismo , Factores de Empalme de ARN , ARN Largo no Codificante/genética , ARN Largo no Codificante/metabolismo , ARN Nucleolar Pequeño/genética , ARN Nucleolar Pequeño/metabolismo , Proteínas de Unión al ARN/genética , Proteínas de Unión al ARN/metabolismo , Proteínas Represoras/genética , Proteínas Represoras/metabolismo
6.
Sensors (Basel) ; 20(9)2020 Apr 25.
Artículo en Inglés | MEDLINE | ID: mdl-32344855

RESUMEN

Vehicle evaluation parameters, which are increasingly of concern for governments and consumers, quantify performance indicators, such as vehicle performance, emissions, and driving experience to help guide consumers in purchasing cars. While past approaches for driving cycle prediction have been proven effective and used in many countries, these algorithms are difficult to use in China with its complex traffic environment and increasingly high frequency of traffic jams. Meanwhile, we found that the vehicle dataset used by the driving cycle prediction problem is usually unbalanced in real cases, which means that there are more medium and high speed samples and very few samples at low and ultra-high speeds. If the ordinary clustering algorithm is directly applied to the unbalanced data, it will have a huge impact on the performance to build driving cycle maps, and the parameters of the map will deviate considerable from actual ones. In order to address these issues, this paper propose a novel driving cycle map algorithm framework based on an ensemble learning method named multi-clustering algorithm, to improve the performance of traditional clustering algorithms on unbalanced data sets. It is noteworthy that our model framework can be easily extended to other complicated structure areas due to its flexible modular design and parameter configuration. Finally, we tested our method based on actual traffic data generated in Fujian Province in China. The results prove the multi-clustering algorithm has excellent performance on our dataset.

7.
Clin Lab ; 65(3)2019 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-30868866

RESUMEN

BACKGROUND: In the present study, we mainly focused on miR-98-5p, which is shown to be dysregulated in various diseases. However, whether miR-98-5p is increased in the serum of asthma patients has never been explored. METHODS: The levels of miR-98-5p and IL-13 were determined in the serum of bronchial asthma children. ROC analysis was carried out to evaluate whether miR-98-5p could be used as a potential biomarker for children with bronchial asthma. RESULTS: The current study showed that the relative expression level of miR-98-5p in the asthmatic remission group and asthmatic acute group was significantly lower than that in the healthy control group, and the relative expression level of miR-98-5p in the asthmatic acute group was significantly lower than that in the asthmatic remission group. In children with acute asthma attacks, the levels of miR-98-5p in the moderate group and severe group were significantly lower than those in the mild group, and those in the severe group were significantly lower than those in the moderate group. Furthermore, the serum IL-13 levels in the asthma remission group and acute asthma group were significantly higher than those in the healthy control group, and the serum IL-13 levels in acute asthma group were significantly higher than those in asthma remission group. CONCLUSIONS: In summary, the current study suggests that miR-98-5p may affect the occurrence and development of bronchial asthma in children via affecting the expression of IL-13.


Asunto(s)
Asma/sangre , Interleucina-13/sangre , MicroARNs/sangre , Biomarcadores/sangre , Estudios de Casos y Controles , Niño , Preescolar , Femenino , Células HEK293 , Humanos , Masculino
8.
ACS Appl Mater Interfaces ; 15(51): 59502-59511, 2023 Dec 27.
Artículo en Inglés | MEDLINE | ID: mdl-38086739

RESUMEN

By immobilizing the metal complex on the substrate surface, our previous results have demonstrated that heterogeneous catalysts with well-dispersed active MNC (metal-nitrogen-carbon) sites can be prepared in a rational and efficient manner. In this study, we employed agarose aerogel (AA) as the substrate to illustrate a straightforward strategy for immobilizing ZnNx sites on the surface. Under relatively low temperatures, the amine group of the ligand condenses with the surface carbonyl group generated in situ, resulting in the surface immobilized Zn sites. This can be supported by the IR, PXRD, and XPS data. Comprehensive characterization methods, including synchrotron powder XRD and spherical aberration-corrected TEM, confirmed the absence of ZnNx site aggregation in the surface immobilization process, even with a high Zn content (up to 8 wt %). The immobilized ZnNx sites exhibited high catalytic performance in Knoevenagel condensation, and α,ß-unsaturated compounds were obtained with high yield in both batch and continuous flow reactions. AA-ZnNx-200 showed the best catalytic activity, which was processed under 200 °C with a Zn content of 4.62 wt %. The immobilized ZnNx sites activated both the aldehyde and nitrile substrates, which were quantitatively converted into the corresponding α,ß-unsaturated compounds, with water as the solvent at room temperature. In continuous flow reaction conditions, a conversion rate up to 99% can be achieved with malononitrile. This heterogeneous catalyst can be facilely produced with quantitative yield in a large scale from cheap starting material under mild conditions. No catalyst deactivation was observed after seven batch reaction cycles or 80 h of continuous flow reaction, indicating its high robustness under catalytic reaction conditions. This catalyst enables a separation-free, energy-saving, and environment-friendly production process, offering a practical way for the industrial production.

9.
Dalton Trans ; 52(30): 10372-10377, 2023 Aug 01.
Artículo en Inglés | MEDLINE | ID: mdl-37465927

RESUMEN

Light-induced substance conversion is highly promising for creating new radical-based compounds. Herein, we report an Er(III) coordination polymer [Er(CA)(ACA)(DMF)(H2O)]n (1) and its Y(III)-diluted analogue 1@Y (H2CA = 2,5-dichloro-3,6-dihydroxy-p-quinone, HACA = 9-anthracene carboxylic acid) with the light-induced transformation of the ligand to a radical. The χMT values of light-transformed products 1a and 1a@Y are higher than those of 1 and 1@Y, respectively, due to the formation of radicals by ultraviolet light irradiation, confirmed by EPR measurement as well. The effective energy barriers for magnetization reversal (Ueff) decrease from 72 K for 1 to 67 K for 1a, and from 117 K for 1@Y to 94 K for 1a@Y. This work not only provides a new light-conversion system but also reveals the nature of photo-induced variation of magnetic properties.

10.
Dalton Trans ; 53(1): 148-152, 2023 Dec 19.
Artículo en Inglés | MEDLINE | ID: mdl-38018387

RESUMEN

Photocontrolled magnetic properties are fundamental for the applications of molecular magnets, which have the features of high time and space resolution; however, such magnetic properties are highly challenging to be achieved owing to the weak light-matter interactions. Herein, the influence of in situ light irradiation on the field-induced magnetization dynamics of two Er(III) coordination polymers 1 and 2 with the same coordination skeletons but different halogen substituents was studied. 1 and 2, and their in situ photoexcited products 1a and 2a, display field-induced magnetization dynamics based on Orbach and/or Raman processes. The magnetization dynamics are fine-modulated by the synergetic effect of light irradiation and a ligand substituent, due to the charge re-distribution of the excited states of the ligand.

11.
Dalton Trans ; 51(2): 473-477, 2022 Jan 04.
Artículo en Inglés | MEDLINE | ID: mdl-34929729

RESUMEN

pH-Dependent self-assembly and structural transformation have been observed in a series of porous In(III)-MOFs, H3O[In3(pta)4(OH)2]·10H2O (NXU-1), [In(pta)2]·C3H10N (NXU-2) and [In(pta)2]·C3H10N (NXU-3) (H2pta = 2-(4-pyridyl)-terephthalic acid). The structural diversities of NXU-1-3 reveal that the pH value of the reaction plays a key role in the assembly of In-MOFs. NXU-1 with excellent stability exhibits highly selective CO2 adsorption over CH4 as compared to NXU-2 and NXU-3, owing to the presence of abundant multiple active sites unveiled by theoretical calculations.

12.
Dalton Trans ; 51(44): 17089-17096, 2022 Nov 15.
Artículo en Inglés | MEDLINE | ID: mdl-36314356

RESUMEN

Four air-stable mononuclear Co(II) complexes, with the formulas [Co(dapbh)(H2O)(CH3OH)] (1), [Co(Hdapbh)(N3)(CH3OH)]·(CH3OH) (2), [Co(H2aapbh)(CH3OH)2]·(NO3)2 (3) and [Co(H2bapbh)(H2O)(NO3)]·(NO3) (4), have been synthesized and structurally characterized by single crystal X-ray diffraction. In all of the complexes, the Co(II) centers constrained by the rigid pentadentate ligand H2LR with two protonable hydrogens adopt a heptacoordinated pentagonal-bipyramidal geometry. The combined analyses of magnetic data and ab initio calculations unveil large easy-plane magnetic anisotropies for these complexes (D = +37.338, +37.273, +41.138 and +41.139 cm-1 for 1-4, respectively), which indicate that the chemical alterations of the equatorial ligand and the ligand field strength in the axial positions synergistically fine-tune the magnitude of the D values. Magnetic investigations demonstrate the field-induced single-ion magnetic behavior in complexes 1, 2 and 4 with diverse energy barriers (Ueff) of 12.25 for 1, 44.15 for 2 and 48.72 K for 4, corresponding to the geometrical distortion of the heptacoordinated Co(II) ion. That is, the greatest deviation from the ideal D5h symmetry in 4 is responsible for the highest barrier.

13.
Dalton Trans ; 50(6): 2102-2111, 2021 Feb 14.
Artículo en Inglés | MEDLINE | ID: mdl-33491020

RESUMEN

A series of five mononuclear ß-diketonate-Dy(iii) complexes, with formulas Dy(ntfa)3(Br-bpy) (1), Dy(ntfa)3(Br2-bpy) (2), Dy(ntfa)3(5,5-(CH3)2-bpy) (3), Dy(ntfa)3(4,4-((CH3)3)2-bpy) (4) and Dy(ntfa)3(4,4-(CH3)2-bpy) (5) (ntfa = 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione, Br-bpy = 5-bromo-2,2'-bipyridine, Br2-bpy = 4,4'-dibromo-2,2'-bipyridine, 5,5-(CH3)2-bpy = 5,5'-di-methyl-2,2'-bipyridine, 4,4-((CH3)3)2-bpy = 4,4'-di-tert-butyl-2,2'-bipyridine, and 4,4-(CH3)2-bpy = 4,4'-di-methyl-2,2'-bipyridine), have been prepared by altering the capping N-donor coligands. Dy(iii) ions in all complexes possess N2O6 octa-coordinated environments, displaying a distorted square antiprismatic D4d symmetry in complexes 1-4, as well as a triangular dodecahedron D2d symmetry in 5. Magnetic investigations evidence the SIM behavior in the five complexes with the energy barriers (Ueff) of 104.19 K (1), 122.93 K (2), 84.20 K (3), 64.16 K (4) and 80.23 K (5) under zero applied dc field. The potential QTM effects in the title complexes are successfully suppressed in the presence of the extra applied fields. The crystal field parameters and orientations of the magnetic easy axes were obtained from the simulation of the magnetic data and the electrostatic model calculation. The distinct electronic effects originating from the subtle changes of the substituents on the capping N-donor coligands induce varying coordination microenvironments and geometries on the Dy(iii) sites, further drastically impacting the overall magnetic properties of the title complexes. The disparities of the uniaxial anisotropy and the magnetic dynamics for 1-5 have been elucidated by ab initio calculations as well.

14.
IEEE Trans Neural Netw Learn Syst ; 31(8): 2741-2751, 2020 08.
Artículo en Inglés | MEDLINE | ID: mdl-31425058

RESUMEN

Linking online identities of users among countless heterogeneous network services on the Internet can provide an explicit digital representation of users, which can benefit both research and industry. In recent years, user identity linkage (UIL) through the Internet has become an emerging task with great potential and many challenges. Existing works mainly focus on online social networks that consider inconsistent profiles, content, and networks as features or use sparse location-based data sets to link the online behaviors of a real person. To extend the UIL problem to a general scenario, we try to link the web-browsing behaviors of users, which can help to distinguish specific users from others, such as children or malicious users. More specifically, we propose a Siamese neural network (NN) architecture-based UIL (SAUIL) model that learns and compares the highest-level feature representation of input web-browsing behaviors with deep NNs. Although the number of matching and nonmatching pairs for the UIL problem is highly imbalanced, previous studies have not considered imbalanced UIL data sets. Therefore, we further address the imbalanced learning issue by proposing cost-sensitive SAUIL (C-SAUIL) model, which assumes higher costs for misclassifying the minority class. In the experiments, the proposed model is robust and exhibits a good performance on very large, real-world data sets collected from different regions with distinct characteristics.


Asunto(s)
Almacenamiento y Recuperación de la Información/métodos , Internet , Redes Neurales de la Computación , Navegador Web , Humanos , Almacenamiento y Recuperación de la Información/tendencias , Internet/tendencias , Navegador Web/tendencias
15.
Dalton Trans ; 49(7): 2300-2307, 2020 Feb 21.
Artículo en Inglés | MEDLINE | ID: mdl-32016242

RESUMEN

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.

16.
Chem Asian J ; 14(10): 1860-1869, 2019 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-30681283

RESUMEN

Four tetraphenylethylenes (2 a-d) containing an electron-rich 2,3,4,6-tetrahydro-1,6-dithia-3a-azaphenalene (THDTAP) moiety have been synthesized. The 2 a-d show aggregation-induced emission (AIE) with yellowish green photoluminescence (PL) in THF-H2 O (v/v, 1:9) solution and in the solid state. Compounds 2 a-d undergo 1,2-migratory shift in oxidative cyclodehydrogenation reactions to afford the unexpected products 3 a-d which display green PL in CH2 Cl2 solution and are non-emissive in the solid state. The PL intensities of 3 a-d are clearly enhanced in the presence of meta-chloroperoxybenzoic acid (mCPBA) owing to the oxidation of the S-atoms on the THDTAP moiety. In contrast, the PL of 2 a-d in THF-H2 O (v/v, 1:9) solution is quenched by adding mCPBA, ascribable to the oxidation of the C=C bond on the ethylene moiety. It is found that the absorption of 3 a-d is distinctly red-shifted from the UV/Vis region to the NIR region upon acidification, arising from the protonation of the N-atom on the THDTAP moiety. Furthermore, 3 a-d display nonlinear optical response (NLO) and optical limiting (OL) behaviour which is superior to that of the well-known OL material C60 .

17.
Life Sci ; 182: 80-84, 2017 Aug 01.
Artículo en Inglés | MEDLINE | ID: mdl-28625359

RESUMEN

ADP-ribosylation factor 6 (Arf6), a member of small GTPases ADP-ribosylation factor (Arf) family, expresses widely in mammalian cells and mainly regulates the functions of membrane traffic and actin remodeling. Current studies indicated that the activation and high expression of Arf6 protein may be significantly correlated with the invasion and metastasis of several tumors, such as breast cancer, pancreatic cancer, lung cancer, etc. Meanwhile, the ability of tumor invasion and metastasis can be suppressed when Arf6 activity is blocked by the inhibitors or small-interfering RNAs of Arf6. To explore the precisely potential mechanisms between Arf6 and the process of tumor invasion, metastasis and proliferation, we concludes the functions and potential signaling pathways of Arf6 in tumor cells and provides an overview about clinical prospects of Arf6 in the screening, diagnosis, treatment and evaluation of prognosis of neoplasms.


Asunto(s)
Factores de Ribosilacion-ADP/metabolismo , Proliferación Celular , Neoplasias/patología , Factor 6 de Ribosilación del ADP , Factores de Ribosilacion-ADP/antagonistas & inhibidores , Factores de Ribosilacion-ADP/genética , Animales , Humanos , Invasividad Neoplásica , Metástasis de la Neoplasia , Neoplasias/diagnóstico , Neoplasias/genética , Pronóstico , ARN Interferente Pequeño , Transducción de Señal
18.
Dalton Trans ; 46(23): 7556-7566, 2017 Jun 13.
Artículo en Inglés | MEDLINE | ID: mdl-28574547

RESUMEN

Based on two fluoro-substituted phenylacetate isomers, o-fluorophenylacetic acid (o-Hfpa) and p-fluorophenylacetic acid (p-Hfpa), two new Cu(ii)-azido compounds, [Cu(o-fpa)(N3)(C2H5OH)]n (1) and [Cu(p-fpa)(N3)(C2H5OH)]n (2), have been prepared, and structurally and magnetically characterized. Single-crystal structure analyses indicate that compounds 1 and 2 consist of 1D chain-like coordination networks in which adjacent copper cations are linked by the alternating triple-bridges of µ-1,1-azido, syn,syn-carboxylate and µ2-ethanol. For the two title compounds, the diverse charge distributions on the carboxyl groups caused by distinct substituent effects of the two phenylacetate coligands lead to the different structural parameters of intrachain Cu-Cu distances (3.218 Å for 1 and 3.168 Å for 2) and Cu-N-Cu angles (106.82° for 1 and 104.81° for 2), further resulting in the disparity of magnetic behaviors. The dominant ferromagnetic couplings between neighbouring Cu(ii) ions in the two compounds (J = 87.08 cm-1 for 1, J = 66.05 cm-1 for 2) are due to the counter-complementarity of the multiple superexchange pathways, contributing to the interesting plots of a ferromagnetic order (Tc = 11.0 K for 1, 9.5 K for 2) and slow magnetic relaxation that are rarely observed in most of the reported azido-Cu(ii) architectures. Heat-capacity experiments further emphasize the characteristic long-range ferromagnetic ordering in compounds 1 and 2. Magneto-structural relationships of 1 and 2 are investigated as well. Moreover, DFT calculations (using different methods and basis sets) have been performed on both compounds to provide a qualitative and quantitative theoretical explanation of their magnetic behavior.

19.
Dalton Trans ; 46(4): 1207-1217, 2017 Jan 24.
Artículo en Inglés | MEDLINE | ID: mdl-28054687

RESUMEN

Employing two benzoate derivatives with different numbers of non-coordinated fluoro-substituents, 2-fluorobenzoic acid (2-Hfba) and 2,6-difluorobenzoic acid (2,6-Hdfba), two new azido-copper coordination polymers, [Cu(2-fba)(N3)(CH3OH)]n (1) and [Cu(2,6-dfba)(N3)(CH3OH)]n (2), have been successfully isolated, and then structurally and magnetically investigated. Single crystal structure analysis demonstrates that the metal cations in the two resulting compounds are connected by the alternating triple-bridge of µ-1,1-azido, syn,syn-carboxylate and µ2-methanol, contributing to analogously linear 1D Cu(ii) chain-like motifs with slightly different intrachain and interchain geometric parameters. The fine-tuned structures lead to variant magnetic properties in the two title compounds. Although a dominant ferromagnetic coupling between adjacent Cu(ii) ions within each chain due to the counter-complementarity of the multiple superexchange pathways is observed in both compounds, the interesting plots of magnetic ordering and slow magnetic relaxation, which are rare in most of the reported azido-Cu(ii) architectures, only occur in compound 1, while 2 behaves as an antiferromagnet consisting of ferromagnetic Cu(ii) chains. The heat-capacity experiments further emphasize the characteristic long-range ferromagnetic ordering in 1 and the typical behavior of antiferromagnets in 2. Moreover, density functional theory (DFT) calculations (using different methods and basis sets) have been performed on both compounds to obtain the qualitatively theoretical interpretation of the magnetic behaviors.

20.
Org Lett ; 15(15): 3820-3, 2013 Aug 02.
Artículo en Inglés | MEDLINE | ID: mdl-23875630

RESUMEN

An efficient synthesis of quinoxalin-2(1H)-ones or spiro[cyclohexene-1,2'-imidazol]-4'-ones has been achieved in moderate to high yields by the visible light-induced and N-bromosuccinimide-mediated cyclization reaction of 2-azido-N-phenylacetamides at ambient temperature. Both the regioselectivity and the speed of cyclization are affected by the substituents attached to the phenyl ring. For example, quinoxalin-2-ones are produced as the main products when the substrates bear electron-withdrawing groups at the para-position of the phenyl ring; in contrast, spiro[cyclohexene-1,2'-imidazol]-4'-ones are obtained as the main products when the substrates bear electron-donating groups at the para-position.

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