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1.
Phys Chem Chem Phys ; 26(17): 13364-13373, 2024 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-38639921

RESUMO

In this study, we successfully synthesize palladium-decorated indium trioxide (Pd/In2O3) hybrid nanoclusters (NCs) using an advanced dual-target cluster beam deposition (CBD) method, a significant stride in developing high-performance ethanol sensors. The prepared Pd/In2O3 hybrid NCs exhibit exceptional sensitivity, stability, and selectivity to low concentrations of ethanol vapor, with a maximum response value of 101.2 at an optimal operating temperature of 260 °C for 6 at% Pd loading. The dynamic response of the Pd/In2O3-based sensor shows an increase in response with increasing ethanol vapor concentrations within the range of 50 to 1000 ppm. The limit of detection is as low as 24 ppb. The sensor exhibits a high sensitivity of 28.24 ppm-1/2, with response and recovery times of 2.7 and 4.4 seconds, respectively, for 100 ppm ethanol vapor. Additionally, the sensor demonstrates excellent repeatability and stability, with only a minor decrease in response observed over 30 days and notable selectivity for ethanol compared to other common volatile organic compounds. The study highlights the potential of Pd/In2O3 NCs as promising materials for ethanol gas sensors, leveraging the unique capabilities of CBD for controlled synthesis and the catalytic properties of Pd for enhanced gas-sensing performance.

2.
Foodborne Pathog Dis ; 2024 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-38900687

RESUMO

Methicillin-resistant Staphylococcus aureus (MRSA) can easily form biofilms on food surfaces, thus leading to cross-contamination, which is difficult to remove. Therefore, there is an urgent need to find alternatives with good antibacterial and antibiofilm effects. In this study, two indole sesquiterpene compounds, xiamycin (1) and chlorinated metabolite chloroxiamycin (2), were isolated from the fermentation liquid of marine Streptomyces sp. NBU3429 for the first time. The chemical structures of the two compounds were characterized by spectroscopic data interpretation, including 1D NMR and HRESIMS analysis. Antimicrobial test showed that chloroxiamycin (2) (minimum inhibitory concentration, MIC = 16 µg/mL) exhibited superior antibacterial activity than xiamycin (1) (MIC = 32 µg/mL) against MRSA ATCC43300. Moreover, compound (2) decreased the biofilm formation rate of MRSA ATCC43300 by 12.7%-84.6% in the concentration range of 32-512 µg/mL, which is relatively stronger than xiamycin (1) (4.1%-49.9%) as well. Antibacterial/antibiofilm mechanism investigation indicated that chloroxiamycin (2) could disrupt the cell wall and membrane of MRSA, inhibiting the production of biofilm extracellular polysaccharides. All these results illustrated that chloroxiamycin (2) is an effective antibacterial/antibiofilm agent, which makes it an attractive candidate for food preservatives.

3.
J Asian Nat Prod Res ; : 1-7, 2023 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-37712720

RESUMO

Two oxygenated ergostane-type steroids including one new compound, 3ß-hydroxy-5α,6ß-methoxyergosta-7,22-dien-15-one (1) along with a known analogue ergosta-6,22-dien-3ß,5α,8α-triol (2) were isolated from the crude extracts of the marine sponge-derived fungus Aspergillus sp. Their structures were elucidated on the basis of combined NMR and MS spectroscopic methods. Compound 1 was a marine ergostane-type steroid with two methoxy groups at C-5 and C-6, respectively. These oxygenated ergostane-type steroids were evaluated for their antibacterial activities against human or aquatic pathogens. Among them, compound 1 exhibited antibacterial activity against Staphylococcus aureus.

4.
Angew Chem Int Ed Engl ; 62(44): e202309108, 2023 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-37699125

RESUMO

One-step separation of C2 H4 from ternary C2 mixtures by physisorbents remains a challenge to combine excellent separation performance with high stability, low cost, and easy scalability for industrial applications. Herein, we report a strategy of constructing negative electrostatic pore environments in a stable, low-cost, and easily scaled-up aluminum MOF (MOF-303) for efficient one-step C2 H2 /C2 H6 /C2 H4 separation. This material exhibits not only record high C2 H2 and C2 H6 uptakes, but also top-tier C2 H2 /C2 H4 and C2 H6 /C2 H4 selectivities at ambient conditions. Theoretical calculations combined with in situ infrared spectroscopy indicate that multiple N/O sites on pore channels can build a negative electro-environment to provide stronger interactions with C2 H2 and C2 H6 over C2 H4 . Breakthrough experiments confirm its exceptional separation performance for ternary mixtures, affording one of the highest C2 H4 productivity of 1.35 mmol g-1 . This material is highly stable and can be easily synthesized at kilogram-scale from cheap raw materials using a water-based green synthesis. The benchmark combination of excellent separation properties with high stability and low cost in scalable MOF-303 has unlocked its great potential in this challenging industrial separation.

5.
Angew Chem Int Ed Engl ; 62(12): e202218590, 2023 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-36691771

RESUMO

Developing porous materials for C3 H6 /C3 H8 separation faces the challenge of merging excellent separation performance with high stability and easy scalability of synthesis. Herein, we report a robust Hofmann clathrate material (ZJU-75a), featuring high-density strong binding sites to achieve all the above requirements. ZJU-75a adsorbs large amount of C3 H6 with a record high storage density of 0.818 g mL-1 , and concurrently shows high C3 H6 /C3 H8 selectivity (54.2) at 296 K and 1 bar. Single-crystal structure analysis unveil that the high-density binding sites in ZJU-75a not only provide much stronger interactions with C3 H6 but also enable the dense packing of C3 H6 . Breakthrough experiments on gas mixtures afford both high separation factor of 14.7 and large C3 H6 uptake (2.79 mmol g-1 ). This material is highly stable and can be easily produced at kilogram-scale using a green synthesis method, making it as a benchmark material to address major challenges for industrial C3 H6 /C3 H8 separation.

6.
Small ; 18(23): e2200634, 2022 06.
Artigo em Inglês | MEDLINE | ID: mdl-35435324

RESUMO

The development of hydrogen sensors is of paramount importance for timely leak detection and remains a crucial unmet need. Palladium-based materials, well known as hydrogen sensors, still suffer from poisoning and deactivation. Here, a hybrid hydrogen sensor consisting of a Pd nanocluster (NC) film, a metal-organic framework (MOF), and a polymer, are proposed. The polymer coating, as a protection layer, endows the sensor with excellent H2 selectivity and CO-poisoning resistance. The MOF serves as an interface layer between the Pd NC film and the polymer layer, which alters the nature of the interaction with hydrogen and leads to significant sensing performance improvements, owing to the interfacial electronic coupling between Pd NCs and the MOF. The strategy overcomes the shortcomings of retarded response speed and degraded sensitivity induced by the polymer coating of a Pd NC film-polymer hybrid system. This is the first exhibition of a hydrogen-sensing enhancement mechanism achieved by engineering the electronic coupling between Pd and a MOF. The work establishes a deep understanding of the hydrogen-sensing enhancement mechanism at the nanoscale and provides a feasible strategy to engineer next-generation gas-sensing nanodevices with superior sensing figures of merit via hybrid material systems.


Assuntos
Estruturas Metalorgânicas , Nanoestruturas , Hidrogênio , Paládio , Polímeros
7.
Angew Chem Int Ed Engl ; 61(41): e202211523, 2022 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-35979632

RESUMO

Developing porous materials to overcome the trade-off between adsorption capacity and selectivity for C2 H2 /CO2 separation remains a challenge. Herein, we report a stable HKUST-1-like MOF (ZJU-50a), featuring large cages decorated with high density of supramolecular binding sites to achieve both high C2 H2 storage and selectivity. ZJU-50a exhibits one of the highest C2 H2 storage capacity (192 cm3 g-1 ) and concurrently high C2 H2 /CO2 selectivity (12) at 298 K and 1 bar. Single-crystal X-ray diffraction studies on gas-loaded ZJU-50a crystal unveil that the incorporated supramolecular binding sites can selectively take up C2 H2 molecule but not CO2 to result in both high C2 H2 storage and selectivity. Breakthrough experiments validated its separation performance for C2 H2 /CO2 mixtures, providing a high C2 H2 recovery capacity of 84.2 L kg-1 with 99.5 % purity. This study suggests a novel strategy of engineering supramolecular binding sites into MOFs to overcome the trade-off for this separation.

8.
Small ; 17(25): e2100862, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-34032374

RESUMO

Exploring signal amplification strategies to enhance the sensitivity of lateral flow immunoassay (LFIA) is of great significance for point-of-care (POC) testing of low-concentrated targets in the field of in vitro diagnostics. Here, a highly-sensitive LFIA platform using compact and hierarchical magneto-fluorescent assemblies as both target-enrichment substrates and optical sensing labels is demonstrated. The large-pored dendritic templates are utilized for high-density incorporation of both superparamagnetic iron oxide nanoparticles (IOs) and quantum dots (QDs) within the vertical channels. The hierarchical structure is built via affinity-driven assembly of IOs and QDs from organic phase with silica surface and mercapto-organosilica intermediate layer, respectively. The sequential assembly with central-radial channels enables 3D loading of dual components and separately controlling of discrete functionalities. After the alkyl-organosilica encapsulation and silica sealing, the composite spheres exhibit high stabilities and compatibility with LFIA for procalcitonin (PCT) detection. With the assistance of liquid-phase antigen-capturing, magnetic enrichment, and fluorescence-signal amplification, a limit of detection of 0.031 ng mL-1 for PCT is achieved with a linear range from 0.012 to 10 ng mL-1 . The current LFIA is robust and validated for PCT detection in real serum, which holds great diagnostic significance for precise guidance of antibiotic therapy with POC manner.


Assuntos
Sistemas Automatizados de Assistência Junto ao Leito , Pontos Quânticos , Coloides , Imunoensaio , Limite de Detecção
9.
Opt Lett ; 46(20): 5165-5168, 2021 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-34653142

RESUMO

Silicon photonics has become the preferred candidate for technologies applicable to multifarious fields. However, the applications are strictly limited by the intrinsic in-band photo effect of silicon. Herein, near-infrared photodetectors that break through the silicon bandgap by Er/O hyperdoping are fabricated, potentially extending their applications into telecommunications, low-light-level night vision, medical treatment, and others. Er/O-hyperdoped silicon was achieved as an infrared light absorption layer through ion implantation. The lattice damage caused by ion implantation was repaired by a deep cooling process in which high-temperature samples were cooled by helium flushing cooled by liquid nitrogen. Traditional junction and metallization processes were performed to form a photodiode. We demonstrate that the device has a spectral range up to the wavelength of 1568 nm, a maximum responsivity of 165 µA/W at 1310 nm, and 3 dB cutoff bandwidth up to 3 kHz. Finally, temperature-dependent optical-electrical characteristics were measured to demonstrate the activation mechanism of Er/O in silicon. This Letter proves silicon's potential in realizing extended infrared detection at room temperature, and it provides a possible way to fabricate infrared optoelectronics and signal processing integrated chips on a CMOS (complementary metal-oxide-semiconductor) platform.

10.
Angew Chem Int Ed Engl ; 60(47): 25068-25074, 2021 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-34529885

RESUMO

Porous materials for C2 H2 /CO2 separation mostly suffer from high regeneration energy, poor stability, or high cost that largely dampen their industrial implementation. A desired adsorbent should have an optimal balance between excellent separation performance, high stability, and low cost. We herein report a stable, low-cost, and easily scaled-up aluminum MOF (CAU-10-H) for highly efficient C2 H2 /CO2 separation. The suitable pore confinement in CAU-10-H can not only provide multipoint binding interactions with C2 H2 but also enable the dense packing of C2 H2 inside the pores. This material exhibits one of the highest C2 H2 storage densities of 392 g L-1 and highly selective adsorption of C2 H2 over CO2 at ambient conditions, achieved by a low C2 H2 adsorption enthalpy (27 kJ mol-1 ). Breakthrough experiments confirm its exceptional separation performance for C2 H2 /CO2 mixtures, affording both large C2 H2 uptake of 3.3 mmol g-1 and high separation factor of 3.4. CAU-10-H achieves the benchmark balance between separation performance, stability, and cost for C2 H2 /CO2 separation.

11.
J Am Chem Soc ; 142(1): 633-640, 2020 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-31838841

RESUMO

The separation of ethane (C2H6) from ethylene (C2H4) is of prime importance in the production of polymer-grade C2H4 for industrial manufacturing. It is very challenging and still remains unexploited to fully realize efficient C2H6/C2H4 separation in the emerging hydrogen-bonded organic frameworks (HOFs) due to the weak nature of hydrogen bonds. We herein report the benchmark example of a novel ultrarobust HOF adsorbent (termed as HOF-76a) with a Brunauer-Emmett-Teller surface area exceeding 1100 m2 g-1, exhibiting the preferential binding of C2H6 over C2H4 and thus highly selective separation of C2H6/C2H4. Theoretical calculations indicate the key role of the nonpolar surface and the suitable triangular channel-like pores in HOF-76a to sterically "match" better with the nonplanar C2H6 molecule than the planar C2H4, thus affording overall stronger multipoint van der Waals interactions with C2H6. The exceptional separation performance of HOF-76a for C2H6/C2H4 separation was clearly demonstrated by gas adsorption isotherms, ideal adsorbed solution theory calculations, and simulated and experimental breakthrough curves. Breakthrough experiments on HOF-76a reveal that polymer-grade ethylene gas can be straightforwardly produced from 50/50 (v/v) C2H6/C2H4 mixtures during the first adsorption cycle with a high productivity of 7.2 L/kg at 298 K and 1.01 bar and 18.8 L/kg at 298 K and 5.0 bar, respectively.

12.
Nanotechnology ; 31(19): 195201, 2020 May 08.
Artigo em Inglês | MEDLINE | ID: mdl-31968324

RESUMO

Nanoscale photoconductors often have extremely high gain in quantum efficiency but suffer from the difficulty to design the density of surface states that cause the high photogain. In this Letter, we created high-gain photoconductors by forming a core-shell PN junction in silicon nanowires via self-assembled molecular monolayer doping. The highly doped n-type shell deactivates all the surface states by filling with electrons so that the n-type shell as a well, instead of the surface states, captures and emits photogenerated minority electrons under ON/OFF light illumination. The corresponding excess majority holes are accumulated in the nanowire channel and thus modulate the channel width, resulting in the experimentally observed high photogain (∼108). The photoresponses of these phototransistors were systematically investigated as a function of the nanowire width and light illumination intensity. The results show that the nanowire channel is pinched off for the nanowires narrower than 73 nm due to the core-shell PN junction. We further derived analytical equations based on the PN junction device principle, finding the explicit gain equation that governs the photogain as a function of light intensity and other physical parameters of the nanowires. The explicit gain equations can fit well with the experimental data and allow us to design the core-shell nanowire phototransitors with desired performance.

13.
Immunopharmacol Immunotoxicol ; 41(1): 32-39, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30724631

RESUMO

Background: Dehydroxymethylepoxyquinomicin (DHMEQ) is a specific and potent inhibitor of nuclear factor-kappa B (NF-κB) and has been shown to possess promising potential as an anti-inflammation including anti-atopic dermatitis (AD)-like skin lesions. Objective: To further evaluate the activity of DHMEQ in vivo modified AD-like lesion model in BALB/c mice and in vitro AD-like lesion cell model in human keratinocytes. Materials and methods: In this study, in vivo modified AD-like lesion model in BALB/c mice was chronically induced by the repetitive and alternative application of 2,4-dinitrochlorobenzene (DNCB) and oxazolone (OX) on ears, and stratum corneum of the ear skin was additionally stripped off with surgical tapes before each challenge with DNCB/OX. Moreover, in vitro AD-like lesion cell model in human keratinocytes (HaCaT) achieved by stimulating HaCaT cells with tumor necrosis factor (TNF)-α plus interferon (IFN)-γ was used to investigate mechanisms of the action. Results: The lesions derived from the stratum corneum-removed AD-like lesion model reaches to peak as well as DHMEQ arrives to its efficacy a week earlier than the data previously obtained from the common AD-like lesion model. Results showed that the drug reduced the ear thickness, epidermal thickness, mast cell infiltration, and gene expressions of interleukin (IL)-4, IL-13, and interferon (IFN)-γ in ear tissues. It significantly inhibited the expression of cytokines IL-6 and IL-1ß, chemokines thymus and activation-regulated chemokine (TARC)/CCL17, and macrophage-derived chemokine (MDC)/CCL22 in the stimulated HaCaT cells. Discussion and conclusion: This study indicated that the action of DHMEQ's anti-AD like lesions might be related to its inhibition on NF-κB.


Assuntos
Anti-Inflamatórios/uso terapêutico , Benzamidas/uso terapêutico , Cicloexanonas/uso terapêutico , Dermatite Atópica/prevenção & controle , Epiderme/efeitos dos fármacos , NF-kappa B/antagonistas & inibidores , Animais , Linhagem Celular , Citocinas/antagonistas & inibidores , Citocinas/imunologia , Dermatite Atópica/imunologia , Dermatite Atópica/patologia , Dinitroclorobenzeno , Modelos Animais de Doenças , Epiderme/imunologia , Epiderme/patologia , Feminino , Humanos , Queratinócitos/efeitos dos fármacos , Queratinócitos/imunologia , Camundongos Endogâmicos BALB C , Fator de Necrose Tumoral alfa/imunologia
14.
Mikrochim Acta ; 186(12): 809, 2019 11 19.
Artigo em Inglês | MEDLINE | ID: mdl-31745742

RESUMO

An optical method is described for the ratiometric fluorometric determination of cyanide ions. It is based on the use of a mixture of aqueous solutions of blue-emitting carbon dots (CDs) and red-emitting gold nanoclusters (AuNCs). The presence of cyanide reduces the red fluorescence of the AuNCs through the formation of a stable complex [Au(CN)2-]. The blue emission of the CDs, in contrast, stays constant. Hence, the color of fluorescence changes from red to purple to blue. The ratio of the fluorescence intensities located at 612 and 438 nm varies over a wide range, with 2 linear responses ranges (from 8 nM to 12.5 µM, and from 12.5 to 75 µM). The method was applied to the determination and visual discrimination of cyanide in food and drink samples. Graphical abstract A ratiometric method for determination of cyanide detection is described that is based on mixing carbon dots (CDs) and gold nanoclusters (AuCNs). The presence of cyanide reduces the red fluorescence of the AuNCs through the formation of a stable complex Au(CN)2-. The blue emission of the CDs, in contrast, stays constant. The fluorescence intensity ratios show linear response to cyanide with a concomitant red-purple-blue fluorescence color change.

15.
Angew Chem Int Ed Engl ; 57(46): 15183-15188, 2018 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-30240522

RESUMO

Separation of propyne/propylene (C3 H4 /C3 H6 ) is more difficult and challenging than that of acetylene/ethylene (C2 H2 /C2 H4 ) because of their closer molecular sizes. A comprehensive screening of a series of metal-organic frameworks with broad types of structures, pore sizes, and functionalities was carried out. UTSA-200 was identified as the best separating material for the removal of trace C3 H4 from C3 H4 /C3 H6 mixtures. Gas sorption isotherms reveal that UTSA-200 exhibits by far the highest C3 H4 adsorption capacity (95 cm3 cm-3 at 0.01 bar and 298 K) and record C3 H4 /C3 H6 selectivity, which was mainly attributed to the suitable dynamic pore size to efficiently block the larger C3 H6 molecule whilst the strong binding sites and pore flexibility capture smaller C3 H4 . This material thus provides record purification capacity for the removal of C3 H4 from a 1:99 (or 0.1:99.9, v/v) C3 H4 /C3 H6 mixture to produce 99.9999 % pure C3 H6 with a productivity of 62.0 (or 142.8) mmol g-1 .

16.
Inorg Chem ; 55(15): 7214-8, 2016 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-27176900

RESUMO

A novel metal-organic framework (MOF), [Cu2L(H2O)2]·7DMF·4H2O [ZJU-40; H4L = 5,5'-(pyrazine-2,5-diyl)diisophthalic acid], with Lewis basic nitrogen sites has been constructed and structurally characterized. Owing to the combined features of high porosity, moderate pore sizes, and immobilized Lewis basic nitrogen sites, the activated ZJU-40a exhibits the second-highest gravimetric C2H2 uptake of 216 cm(3) g(-1) (at 298 K and 1 bar) among all of the reported MOFs so far. This value is not only much higher than that of the isoreticular NOTT-101a (184 cm(3) g(-1)), but also superior to those of two very promising MOFs, known as HKUST-1 (201 cm(3) g(-1)) and Co-MOF-74 (197 cm(3) g(-1)). Interestingly, the immobilized nitrogen sites in ZJU-40a have nearly no effect on the CO2 uptake, so ZJU-40a adsorbs a similar amount of CO2 (87 cm(3) g(-1)) compared with NOTT-101a (84 cm(3) g(-1)) at 298 K and 1 bar. As a result, ZJU-40a shows significantly enhanced adsorption selectivity for C2H2/CO2 separation (17-11.5) at ambient temperature compared to that of NOTT-101a (8-9), leading to a superior MOF material for highly selective C2H2/CO2 separation.

17.
Hu Li Za Zhi ; 63(1): 17-21, 2016 Feb.
Artigo em Zh | MEDLINE | ID: mdl-26813058

RESUMO

A dust explosion at the Formosa Fun Coast water park in Taiwan caused nearly 500 burn injury cases. One hundred of these cases involved burns over more than 20% of the total body surface area. This tragedy inundated hospitals across northern Taiwan with an unprecedented number of burn patients. Significant manpower and medical resources were targeted on related resuscitation and treatment efforts, with support and assistance provided by agencies and organizations nationwide. Most of the burn patients were young people in their teens and twenties, whose severe burns posed the greatest threat and challenge to their lives so far. Furthermore, their experience presented major psychosocial and physical health challenges. Patients received an array of clinical treatments such as debridement, skin grafting, dressing, and rehabilitation. Debilitating pain, skin damage, changes to body image, physical disabilities, helplessness, sadness, and anxiety have not only deeply affected the patients physically and psychologically but also created significant life stresses for their family members / companions, which requires counseling in order to facilitate emotional healing. Although burn patients gradually recover as they pass through the acute, recovery, and rehabilitation phases, they will face the challenges of lifelong rehabilitation after discharge. I hope that these young victims will take courage and be brave and strong in dealing with the difficulties and challenges of daily life and will embrace the future with hope as they enter the dawn of their new life.


Assuntos
Acidentes , Queimaduras/psicologia , Explosões , Adulto , Queimaduras/enfermagem , Queimaduras/reabilitação , Humanos , Sobreviventes , Taiwan
18.
Inorg Chem ; 54(23): 11511-9, 2015 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-26595115

RESUMO

Four asymmetric bis(dithienylethene-acetylide) platinum(II) complexes trans-Pt(PEt3)2(L1o)(L5o) (1oo), trans-Pt(PEt3)2(L2o)(L5o) (2oo), trans-Pt(PEt3)2(L3o)(L5o) (3oo), and trans-Pt(PEt3)2(L4o)(L5o) (4oo) with two different dithienylethene-acetylides (L1o-L5o) were designed to modulate stepwise, multistate, and multicolor photochromism by modifying ring-closure absorption wavelengths. Upon irradiation under UV light, 1oo converts only to 1oc without the observation of 1co and dually ring-closed species 1cc. In contrast, both mixed ring-open/closed species oc and co as well as dually ring-closed species cc are observed upon UV light irradiation of 2oo-4oo, implying that a substantial stepwise photochromic process occurs following 2oo-4oo → 2oc-4oc/2co-4co → 2cc-4cc. The conversion percentage of dually ring-closed species at the photostationary state (PSS) is progressively increased following 1cc (0%) → 2cc (40%) → 3cc (86%) → 4cc (>95%), coinciding with the progressive red-shift of ring-closure absorption bands in free L1c (441 nm) → L2c (510 nm) → L3c (556 nm) → L4c (591 nm). Particularly, compound 2 affords four states (2oo, 2co, 2oc, and 2cc) with different colors (colorless, purple, blue, and dark blue, respectively) through a selective photochemical cycloreversion process upon irradiation with appropriate wavelengths of light. Although stepwise photocyclization reactions 3oo → 3co/3oc → 3cc and 4oo → 4co/4oc → 4cc are observed, multicolor photochromism of 3oo and 4oo could not be achieved because ring-closure absorption bands between L3c/L4c and L5c are significantly overlapped. The stepwise photochemical processes are well demonstrated by NMR, UV-vis, and infrared (IR) spectroscopy and time-dependent density functional theory (TD-DFT) computational studies.

19.
J Am Chem Soc ; 136(17): 6207-10, 2014 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-24730649

RESUMO

We have realized a new porous metal-organic framework UTSA-76a with pyrimidine groups on the linker, exhibiting high volumetric methane uptake of ~260 cm(3) (STP) cm(-3) at 298 K and 65 bar, and record high working capacity of ~200 cm(3) (STP) cm(-3) (between 5 and 65 bar). Such exceptionally high working capacity is attributed to the central "dynamic" pyrimidine groups within UTSA-76a, which are capable of adjusting their orientations to optimize the methane packing at high pressure, as revealed by computational studies and neutron scattering experiments.


Assuntos
Metano/isolamento & purificação , Compostos Organometálicos/química , Pirimidinas/química , Adsorção , Modelos Moleculares , Porosidade , Pressão
20.
Acta Crystallogr Sect E Struct Rep Online ; 70(Pt 4): m124, 2014 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-24826090

RESUMO

The trinuclear title compound, [Fe3(C3H6S2)2(CO)7], is a mixed-valent Fe(I)/Fe(II) complex and crystallizes with two mol-ecules of similar configuration in the asymmetric unit. The three Fe atoms in each mol-ecule display a bent arrangement [Fe-Fe-Fe = 156.22 (4) and 157.06 (3)°]. Both outer Fe(I) atoms are six-coordinated in a distorted ocahedral coordination geometry defined by the bridging Fe(II) atom, three carbonyl C atoms and two bridging S atoms. The coordination number of the central Fe(II) atom is seven and includes bonding to the two outer Fe(I) atoms, four bridging S atoms and one carbonyl C atom. The resulting coordination polyhedron might be described as a highly distorted monocapped trigonal prism. In the crystal packing, the mol-ecules exhibit a chain-like arrangement parallel to [100] and [001], and the resulting layers are stacked along [010]. The cohesion of the structure is dominated by van der Waals inter-actions.

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