keyword
MENU ▼
Read by QxMD icon Read
search

EPR

keyword
https://www.readbyqxmd.com/read/28346780/high-spin-polymers-ferromagnetic-coupling-of-s-1-hexaazacyclophane-units-up-to-a-pure-s-2-polycyclophane
#1
Lukasz Skorka, Piotr Kurzep, Timothée Chauviré, Lionel Dubois, Jean-Marie Mouesca, Vincent Maurel, Irena Kulszewicz-Bajer
Triarylamines oxidized to radical cations can be used as stable spins sources for the design of high-spin compounds. Here, we present the synthesis of the polyarylamine containing hexaazacyclophanes linked via meta-terphenyl bridges. Spins, created after the oxidation of the polymer, can be coupled magnetically in cyclophane moieties via meta-phenyl and along the polymer chain via meta-terphenyl units. The formation of quintet spin state was evidenced by pulsed-EPR nutation spectroscopy. Two exchange coupling constants via both couplers were determined experimentally and corresponded to J/k = 89 K in cyclophane moiety and j/k = 17 K via meta-terphenyl...
March 27, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28345918/direct-s0%C3%A2-t-excitation-of-a-conjugated-polymer-repeat-unit-unusual-spin-forbidden-transitions-probed-by-time-resolved-electron-paramagnetic-resonance-spectroscopy
#2
Deborah L Meyer, Florian Lombeck, Sven Huettner, Michael Sommer, Till Biskup
A detailed understanding of the electronic structure of semiconducting polymers and their building blocks is essential to develop efficient materials for organic electronics. (Time-resolved) electron paramagnetic resonance (EPR) is particularly suited to address these questions, allowing to directly detect paramagnetic states and to reveal their spin-multiplicity, besides its clearly superior resolution compared to optical meth- ods. We present here evidence for a direct S0→T optical excitation of distinct triplet states in the repeat unit of a conjugated polymer used in organic photovoltaics...
March 27, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28345728/embedding-1d-or-2d-cobalt-carboxylate-substrates-in-3d-coordination-polymers-exhibiting-slow-magnetic-relaxation-behaviors-crystal-structures-high-field-epr-and-magnetic-studies
#3
Nannan Mao, Biquan Zhang, Fan Yu, Xi Chen, Gui-Lin Zhuang, Zhenxing Wang, Zhongwen Ouyang, Tianle Zhang, Bao Li
By utilizing well-designed bifunctional ligands derived from 1H-imidazole-4,5-dicarboxylic acid, magnetic coordination polymers (CPs) that exhibit slow magnetic relaxation at the low temperature regions were constructed and further structurally characterized. In 1, 1D cobalt-carboxyl chains were stabilized in the final structure. In contrast, by adjusting the length of the substituted arms on imidazole-4,5-dicarboxylic acid, a novel 3D CP, 2 containing 2D 6(3) cobalt-carboxyl layer was obtained. A combination of Quantum Monte Carlo (QMC) simulations and the first-principles Density functional theory (DFT) calculations showed that compound 2 features weak ferro- and antiferro-magnetic coupling mechanisms with two different super-exchange paths of -/+/- for syn-anti carboxylate bridges and -/-/- for syn-syn carboxylate bridges...
March 27, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28345535/photoactivated-processes-in-optical-fibers-generation-and-conversion-mechanisms-of-twofold-coordinated-si-and-ge-atoms
#4
Luigi Giacomazzi, Layla Martin-Samos, Aziz Boukenter, Youcef Ouerdane, Sylvain Girard, Antonino Alessi, Nicolas Richard, Stefano de Gironcoli
In this work we present an extensive investigation of nanoscale physical phenomena related to oxygen-deficient centers (ODC) in silica and Ge-doped silica by means of first-principles calculations, including nudged-elastic band (NEB), electron paramagnetic resonance (EPR) parameters calculations, and many-body perturbation theory (GW and Bethe-Salpeter Equation) techniques. We show that by neutralizing positively charged oxygen monovacancies we can obtain model structures of twofold Si and Ge defects of which the calculated absorption spectra and singlet-to-triplet transitions are in excellent agreement with the experimental optical absorption and photo-luminescence data...
March 27, 2017: Nanotechnology
https://www.readbyqxmd.com/read/28344372/radicals-and-molecular-products-from-the-gas-phase-pyrolysis-of-lignin-model-compounds-cinnamyl-alcohol
#5
Lavrent Khachatryan, Meng-Xia Xu, Ang-Jian Wu, Mikhail Pechagin, Rubik Asatryan
The experimental results on detection and identification of intermediate radicals and molecular products from gas-phase pyrolysis of cinnamyl alcohol (CnA), the simplest non-phenolic lignin model compound, over the temperature range of 400-800 °C are reported. The low temperature matrix isolation - electron paramagnetic resonance (LTMI-EPR) experiments along with the theoretical calculations, provided evidences on the generation of the intermediate carbon and oxygen centered as well as oxygen-linked, conjugated radicals...
September 2016: Journal of Analytical and Applied Pyrolysis
https://www.readbyqxmd.com/read/28343065/interaction-of-a-chelating-agent-5-hydroxy-2-hydroxymethyl-pyridin-4-1h-one-with-al-iii-cu-ii-and-zn-ii-ions
#6
Massimiliano Peana, Serenella Medici, Valeria Marina Nurchi, Joanna I Lachowicz, Guido Crisponi, Eugenio Garribba, Daniele Sanna, Maria Antonietta Zoroddu
5-Hydroxy-2-(hydroxymethyl)pyridin-4(1H)-one ligand, an iron chelator, was evaluated for its coordination ability toward Al(III), Cu(II) and Zn(II) ions by using potentiometric, NMR, EPR and UV-Vis techniques. The behavior of the ligand with the non-essential Al(III) ion has been examined, as well as its potential influence on the homeostatic equilibria of the essential Cu(II) and Zn(II) ions. Structural information on the complex formation equilibria have been obtained from 1D and 2D NMR study. The donor atoms involved in the coordination of Al(III), Cu(II) and Zn(II) ions are (O, O) the same as for Fe(III) at physiological pH value, even if from the complexation competition study the ligand appears to be more selective toward Fe(III) ions supporting that it can be used as an iron chelating agent...
March 16, 2017: Journal of Inorganic Biochemistry
https://www.readbyqxmd.com/read/28342198/an-isolable-diboron-centered-diradical-with-a-triplet-ground-state
#7
Lei Wang, Yong Fang, Haochuan Mao, Yi Qu, Jiacheng Zuo, Zaichao Zhang, Gengwen Tan, Xinping Wang
Two new diboranes 2,6-bis(BMes2)mesitylene (1) and 3,3'-bis(BMes2)bimesitylene (3) were synthesized. Two-electron reduction of 1 with elemental potassium afforded the C-H activation product [(18-c-6)K(THF)2]2+*22- bearing a BC3 four-membered ring as colorless crystals, whereas the reduction of 3 with potassium led to the isolation of [(18-c-6)K(THF)2]2+*32-** as dark blue crystals. Both reduction products were characterized by structural and spectroscopic methods. The EPR spectroscopy and theoretical calculations reveal that the electron spin density of 32-** mainly resides on the two boron nuclei, and it features a triplet ground state, which was confirmed by SQUID measurements as well as theoretical calculations...
March 25, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28336897/three-dimensional-bioi-biox-x-cl-or-br-nanohybrids-for-enhanced-visible-light-photocatalytic-activity
#8
Yazi Liu, Jian Xu, Liqiong Wang, Huayang Zhang, Ping Xu, Xiaoguang Duan, Hongqi Sun, Shaobin Wang
Three-dimensional flower-like BiOI/BiOX (X = Br or Cl) hybrids were synthesized via a facile one-pot solvothermal approach. With systematic characterizations by X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), the Brunauer-Emmett-Teller (BET)specific surface area, X-ray photoelectron spectroscopy (XPS), and the UV-Vis diffuse reflectance spectra (DRS), the BiOI/BiOCl composites showed a fluffy and porous 3-D architecture with a large specific surface area (SSA) and high capability for light absorption...
March 14, 2017: Nanomaterials
https://www.readbyqxmd.com/read/28336314/non-linear-van-t-hoff-behavior-in-pulmonary-surfactant-model-membranes
#9
Ernanni D Vieira, Luis G M Basso, Antonio J Costa-Filho
Pulmonary surfactant exhibits phase coexistence over a wide range of surface pressure and temperature. Less is known about the effect of temperature on pulmonary surfactant models. Given the lack of studies on this issue, we used electron paramagnetic resonance (EPR) and nonlinear least-squares (NLLS) simulations to investigate the thermotropic phase behavior of the matrix that mimics the pulmonary surfactant lipid complex, i.e. the lipid mixture composed of dipalmitoyl phosphatidylcholine (DPPC), palmitoyl-oleoyl phosphatidylcholine (POPC) and palmitoyl-oleoyl phosphatidylglycerol (POPG)...
March 20, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28336129/labile-iron-potentiates-ascorbate-dependent-reduction-and-mobilization-of-ferritin-iron
#10
Charles Badu-Boateng, Sofia Pardalaki, Claude Wolf, Sonia Lajnef, Fabienne Peyrot, Richard J Naftalin
Ascorbate mobilizes iron from equine spleen ferritin by two separate processes. Ascorbate alone mobilizes ferritin iron with an apparent Km (ascorbate) ≈1.5mM. Labile iron >2μM, complexed with citrate (10mM), synergises ascorbate-dependent iron mobilization by decreasing the apparent Km (ascorbate) to ≈270μM and raising maximal mobilization rate by ≈5-fold. Catalase reduces the apparent Km(ascorbate) for both ascorbate and ascorbate+iron dependent mobilization by ≈80%. Iron mobilization by ascorbate alone has a higher activation energy (Ea=45...
March 21, 2017: Free Radical Biology & Medicine
https://www.readbyqxmd.com/read/28335271/distribution-of-iron-oxide-core-titanium-dioxide-shell-nanoparticles-in-vx2-tumor-bearing-rabbits-introduced-by-two-different-delivery-modalities
#11
Tamer Refaat, Derek West, Samar El Achy, Vamsi Parimi, Jasmine May, Lun Xin, Kathleen R Harris, William Liu, Michael Beau Wanzer, Lydia Finney, Evan Maxey, Stefan Vogt, Reed A Omary, Daniele Procissi, Andrew C Larson, Tatjana Paunesku, Gayle E Woloschak
This work compares intravenous (IV) versus fluoroscopy-guided transarterial intra-catheter (IC) delivery of iron oxide core-titanium dioxide shell nanoparticles (NPs) in vivo in VX2 model of liver cancer in rabbits. NPs coated with glucose and decorated with a peptide sequence from cortactin were administered to animals with developed VX2 liver cancer. Two hours after NPs delivery tumors, normal liver, kidney, lung and spleen tissues were harvested and used for a series on histological and elemental analysis tests...
August 3, 2016: Nanomaterials
https://www.readbyqxmd.com/read/28334523/transformable-nanomaterials-as-artificial-extracellular-matrix-for-inhibiting-tumor-invasion-and-metastasis
#12
Xiao-Xue Hu, Ping-Ping He, Guo-Bin Qi, Yu-Juan Gao, Yao-Xin Lin, Chao Yang, Pei-Pei Yang, Hongxun Hao, Lei Wang, Hao Wang
Tumor metastasis is one of the big challenges in cancer treatment and is often associated with high patient mortality. Until now, there is an agreement that tumor invasion and metastasis are related to degradation of extracellular matrix (ECM) by enzymes. Inspired by the formation of natural ECM and the in situ self-assembly strategy developed in our group, herein, we in situ constructed an artificial extracellular matrix (AECM) based on transformable Laminin (LN)-mimic peptide 1 (BP-KLVFFK-GGDGR-YIGSR) for inhibition of tumor invasion and metastasis...
March 23, 2017: ACS Nano
https://www.readbyqxmd.com/read/28327736/a-dnp-supported-solid-state-nmr-study-of-carbon-species-in-fluid-catalytic-cracking-catalysts
#13
Deni Mance, Johan van der Zwan, Marjolein E Z Velthoen, Florian Meirer, Bert M Weckhuysen, Marc Baldus, Eelco T C Vogt
A combination of solid-state NMR techniques supported by EPR and SEM-EDX experiments was used to localize different carbon species (coke) in commercial fluid catalytic cracking catalysts. Aliphatic coke species formed during the catalytic process and aromatic coke species deposited directly from the feedstock respond differently to dynamic nuclear polarization signal enhancement in integral and crushed FCC particles, indicating that aromatic species are mostly concentrated on the outside of the catalyst particles, whereas aliphatic species are also located on the inside of the FCC particles...
March 22, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28325789/sex-specific-differences-in-mitochondria-biogenesis-morphology-respiratory-function-and-ros-homeostasis-in-young-mouse-heart-and-brain
#14
Abdel Rahman M Khalifa, Engy A Abdel-Rahman, Ali M Mahmoud, Mohamed H Ali, Maha Noureldin, Saber H Saber, Mahmoud Mohsen, Sameh S Ali
Sex-specific differences in mitochondrial function and free radical homeostasis are reported in the context of aging but not well-established in pathogeneses occurring early in life. Here, we examine if sex disparity in mitochondria function, morphology, and redox status starts early and hence can be implicated in sexual dimorphism in cardiac as well as neurological disorders prevalent at young age. Although mitochondrial activity in the heart did not significantly vary between sexes, female brain exhibited enhanced respiration and higher reserve capacity...
March 2017: Physiological Reports
https://www.readbyqxmd.com/read/28322401/comparisons-of-mn2s2vs-bipyridine-as-redox-active-ligands-to-manganese-and-rhenium-in-l-l-m-co-3cl-complexes
#15
Allen M Lunsford, Kristina F Goldstein, Matthew A Cohan, Jason A Denny, Nattamai Bhuvanesh, Shengda Ding, Michael B Hall, Marcetta Y Darensbourg
The bipyridine ligand is renowned as a photo- and redox-active ligand in catalysis; the latter has been particularly explored in the complex Re(bipy)(CO)3Cl for CO2 reduction. We ask whether a bidentate, redox-active MN2S2 metallodithiolate ligand in heterobimetallic complexes of Mn and Re might similarly serve as a receptor and conduit of electrons. In order to assess the electrochemical features of such designed bimetallics, a series of complexes featuring redox active MN2S2 metallodithiolates, with M = Ni(2+), {Fe(NO)}(2+), and {Co(NO)}(2+), bound to M'(CO)3X, where M' = Mn and Re, were synthesized and characterized using IR and EPR spectroscopies, X-ray diffraction, cyclic voltammetry, and density functional theory (DFT) computations...
March 21, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28322256/ag-ago-nanoparticles-grown-via-time-dependent-double-mechanism-in-a-2d-layered-ni-pcp-and-their-antibacterial-efficacy
#16
Rashmi A Agarwal, Neeraj K Gupta, Rajan Singh, Shivansh Nigam, Bushra Ateeq
A simple synthesis route for growth of Ag/AgO nanoparticles (NPs) in large quantitative yields with narrow size distribution from a functional, non-activated, Ni (II) based highly flexible porous coordination polymer (PCP) as a template has been demonstrated. This template is a stable storage media for the NPs larger than the pore diameters of the PCP. From EPR study it was concluded that NPs were synthesized via two mechanisms i.e. acid formation and the redox activity of the framework. Size range of Ag/AgO NPs is sensitive to choice of solvent and reaction time...
March 21, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28321699/magnetic-edta-functionalized-cofe2o4-nanoparticles-edta-cofe2o4-as-a-novel-catalyst-for-peroxymonosulfate-activation-and-degradation-of-orange-g
#17
Lin Deng, Zhou Shi, Zhiyan Zou, Shiqing Zhou
EDTA functionalized CoFe2O4 nanoparticles (EDTA-CoFe2O4) synthesized using a facile one-pot solvothermal method were employed as catalysts to activate peroxymonosulfate (PMS) with Orange G (OG) as the target pollutant. Effects of operating parameters including initial solution pH, catalyst dosage, PMS dosage, and water matrix components such as Cl(-), NO3(-), CO3(2-), and humic acid were evaluated. A degradation efficiency of 93% was achieved in 15 min with 1 mM PMS and 0.2 g/L EDTA-CoFe2O4 catalyst, while only 57% of OG was degraded within 15 min in CoFe2O4/PMS system...
March 20, 2017: Environmental Science and Pollution Research International
https://www.readbyqxmd.com/read/28319797/non-enolisable-knoevenagel-condensate-appended-schiff-bases-metal-ii-complexes-spectral-characteristics-dna-binding-and-nuclease-activities
#18
Ammavasi Gubendran, Mookkandi Palsamy Kesavan, Srinivasan Ayyanaar, Liviu Mitu, Periyakaruppan Athappan, Jegathalaprathaban Rajesh
New Schiff base complexes [Cu(L(1))Cl] (1), [Ni(L(1))Cl] (2), [Zn(L(1))Cl] (3), and [Fe(L(2))H2OCl] (4) {L(1)=(4E)-3-(2-hydroxybenzylidene)-4-(2-hydroxyphenylimino)pentan-2-one, L(2)=2,2'-(1E,1'E)-(3-(2-hydroxybenzylidene)-pentane-2,4-diylidene)bis(azan-1-yl-1 idene)diphenol} have been synthesized and characterized by elemental analysis, UV-Vis, IR, FAB-mass, EPR, spectral studies and electrochemical studies, the ligands L(1) &L(2) were characterized by (1)H and (13)C NMR spectra. Complex 1 show a visible spectral d-d band near 600nm and display cyclic voltammetric quasireversible response for the Cu(II)/Cu(I) couple vs Ag/AgCl in DMSO...
March 16, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28319293/bis-gadolinium-complexes-for-solid-effect-and-cross-effect-dynamic-nuclear-polarization
#19
Monu Kaushik, Mian Qi, Adelheid Godt, Björn Corzilius
High-spin complexes act as polarizing agents (PAs) for dynamic nuclear polarization (DNP) in solid-state NMR spectroscopy and feature promising aspects towards biomolecular DNP. We present a study on bis(Gd-chelate)s which enable cross effect (CE) DNP owing to spatial confinement of two dipolar-coupled electron spins. Their well-defined Gd⋅⋅⋅Gd distances in the range of 1.2-3.4 nm allowed us to elucidate the Gd⋅⋅⋅Gd distance dependence of the DNP mechanism and NMR signal enhancement. We found that Gd⋅⋅⋅Gd distances above 2...
March 20, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28316540/x-ray-crystallographic-analysis-epr-studies-and-computational-calculations-of-a-cu-ii-tetramic-acid-complex
#20
Dimitrios Matiadis, Dimitrios Tsironis, Valentina Stefanou, Olga Igglessi-Markopoulou, Vickie McKee, Yiannis Sanakis, Katerina N Lazarou, Athanassios Chrissanthopoulos, Spyros N Yannopoulos, John M Markopoulos
In this work we present a structural and spectroscopic analysis of a copper(II) N-acetyl-5-arylidene tetramic acid by using both experimental and computational techniques. The crystal structure of the Cu(II) complex was determined by single crystal X-ray diffraction and shows that the copper ion lies on a centre of symmetry, with each ligand ion coordinated to two copper ions, forming a 2D sheet. Moreover, the EPR spectroscopic properties of the Cu(II) tetramic acid complex were also explored and discussed...
2017: Bioinorganic Chemistry and Applications
keyword
keyword
94905
1
2
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read
×

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"