scholarly journals Complexes of Glycolic Acid with Nitrogen Isolated in Argon Matrices. II. Vibrational Overtone Excitations

Molecules ◽  
2019 ◽  
Vol 24 (18) ◽  
pp. 3245 ◽  
Author(s):  
Iwona Kosendiak ◽  
Jussi M.E. Ahokas ◽  
Justyna Krupa ◽  
Jan Lundell ◽  
Maria Wierzejewska
Keyword(s):  
Glycolic Acid ◽  
Structural Changes ◽  
Near Infrared ◽  
Theoretical Calculations ◽  
Vibrational Overtone ◽  
Highly Sensitive ◽  
The Matrix ◽  
Argon Matrices ◽  
Site Selective ◽  
Different Levels

Structural changes of glycolic acid (GA) complex with nitrogen induced by selective overtone excitation of the νOH mode were followed in argon matrices using FTIR spectroscopy. For the most stable SSC1 complex present in different trapping sites directly upon deposition site, selective changes in the νOH region were achieved upon near-infrared irradiation. Simultaneously, new conformers of the GA…N2 complex were formed, giving rise to several sets of bands in the νOH and νC=O regions of the spectra. Both position and intensity of new absorptions appeared to be highly sensitive on the wavelength of radiation used, as well as on the annealing of the matrix. Based on theoretical calculations at different levels of theory, an assignment of the observed bands is proposed and discussed.

scholarly journals Complexes of Glycolic Acid with Nitrogen Isolated in Argon Matrices. I. Structures and Thermal Effects

Molecules ◽  
2019 ◽  
Vol 24 (18) ◽  
pp. 3262
Author(s):  
Iwona Kosendiak ◽  
Jussi M.E. Ahokas ◽  
Justyna Krupa ◽  
Jan Lundell ◽  
Maria Wierzejewska
Keyword(s):  
Glycolic Acid ◽  
Complex Structure ◽  
Molecular Complexes ◽  
Nitrogen Molecule ◽  
Stable Complex ◽  
Structure Variation ◽  
The Matrix ◽  
Different Temperatures ◽  
Argon Matrices ◽  
Site Selective

Molecular complexes between glycolic acid and nitrogen were studied in a low-temperature argon matrix with FTIR spectroscopy, and supported by MP2 and BLYPD3 calculations. The calculations indicate 11 and 10 stable complex structures at the MP2 and BLYPD3 levels of theories, respectively. However, only one hydrogen-bonded complex structure involving the most stable SSC conformer of glycolic acid was found experimentally, where the nitrogen molecule is bound with the carboxylic OH group of the SSC conformer. The complex shows a rich site structure variation upon deposition of the matrix in different temperatures and upon annealing experiments, which provide interesting prospects for site-selective chemistry.

scholarly journals IDENTIFICATION OF ACOUSTIC EMISSION SOURCES IN A POLIMER COMPOSITE MATERIAL UNDER THE CYCLE TENSION LOADING

2021 ◽  
pp. 19-27
Author(s):  
A. A. Bryansky ◽  
◽  
O. V. Bashkov ◽  
Keyword(s):  
Acoustic Emission ◽  
Structural Changes ◽  
Destructive Testing ◽  
Local Formation ◽  
Adhesion Failure ◽  
Highly Sensitive ◽  
The Matrix ◽  
Tension Loading ◽  
Non Destructive ◽  
Ae Signals

The structure of polymer composite materials (PCM) provides high mechanical properties but, at the same time, is highly sensitive to the formation of internal defects. Therefore, when designing, manufacturing products, and assessing their reliability in service, much attention is paid to the methods of non-destructive testing, among which the method of acoustic emission (AE) has proven itself to study structural changes in material under external influence. The paper deals with the identification of typical damages in fiberglass samples made of T11-GVS9 glass fiber cloth and DION 9300 FR binder and tested under cyclic tension using the AE method. In the work, the authors solved the problem of selecting the AE informative parameters and used a clustering method to identify the nature and the formation kinetics of the AE sources. The authors performed clustering using the Kohonen self-organization map (SOM) with the Fourier spectra calculated for the AE signals recorded during cyclic tests. Based on the peak frequencies analysis of the produced clusters, the researchers determined their nature and calculated the periods of critical accumulation. When characterizing the AE sources, the authors used the peak frequencies analysis of the wavelet spectra performed for different levels of decomposition. The authors determined the damage accumulation stages of samples during testing based on own research and research by other authors’ results. The study established that registration of AE signals identified as adhesion failure can be used to identify the onset of the material destruction and characterized the local formation of micro-damages in the matrix and fracture of fibers can be used to predict the destruction of PCM.

Theoretical and experimental studies of palladium-catalyzed site-selective C(sp3)−H bond functionalization enabled by transient ligands

2017 ◽  
Author(s):  
Haibo Ge ◽  
Lei Pan ◽  
Piaoping Tang ◽  
Ke Yang ◽  
Mian Wang ◽  
...  
Keyword(s):  
Bond Activation ◽  
Theoretical Calculations ◽  
Experimental Studies ◽  
Bond Functionalization ◽  
Aliphatic Ketones ◽  
Site Selectivity ◽  
Mechanistic Investigation ◽  
Palladium Catalyzed ◽  
Metal Catalyzed ◽  
Site Selective

Transition metal-catalyzed selective C–H bond functionalization enabled by transient ligands has become an extremely attractive topic due to its economical and greener characteristics. However, catalytic pathways of this reaction process on unactivated sp<sup>3</sup> carbons of reactants have not been well studied yet. Herein, detailed mechanistic investigation on Pd-catalyzed C(sp<sup>3</sup>)–H bond activation with amino acids as transient ligands has been systematically conducted. The theoretical calculations showed that higher angle distortion of C(sp2)-H bond over C(sp3)-H bond and stronger nucleophilicity of benzylic anion over its aromatic counterpart, leading to higher reactivity of corresponding C(sp<sup>3</sup>)–H bonds; the angle strain of the directing rings of key intermediates determines the site-selectivity of aliphatic ketone substrates; replacement of glycine with β-alanine as the transient ligand can decrease the angle tension of the directing rings. Synthetic experiments have confirmed that β-alanine is indeed a more efficient transient ligand for arylation of β-secondary carbons of linear aliphatic ketones than its glycine counterpart.<br><br>

scholarly journals Substituent Effects on EI-MS Fragmentation Patterns of 5-Allyloxy-1-aryl-tetrazoles and 4-Allyl-1-aryl-tetrazole-5-ones; Correlation with UV-Induced Fragmentation Channels

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3282
Author(s):  
Alina Secrieru ◽  
Rabah Oumeddour ◽  
Maria L. S. Cristiano
Keyword(s):  
Theoretical Calculations ◽  
Substituent Effects ◽  
Radical Cations ◽  
Electronic Effects ◽  
Diverse Range ◽  
The Matrix ◽  
Electron Impact Mass ◽  
Fragmentation Patterns ◽  
Tetrazole Derivatives ◽  
Impact Mass

1,4- and 1,5-disubstituted tetrazoles possess enriched structures and versatile chemistry, representing a challenge for chemists. In the present work, we unravel the fragmentation patterns of a chemically diverse range of 5-allyloxy-1-aryl-tetrazoles and 4-allyl-1-aryl-tetrazolole-5-ones when subjected to electron impact mass spectrometry (EI-MS) and investigate the correlation with the UV-induced fragmentation channels of the matrix-isolated tetrazole derivatives. Our results indicate that the fragmentation pathways of the selected tetrazoles in EI-MS are highly influenced by the electronic effects induced by substitution. Multiple pathways can be envisaged to explain the mechanisms of fragmentation, frequently awarding common final species, namely arylisocyanate, arylazide, arylnitrene, isocyanic acid and hydrogen azide radical cations, as well as allyl/aryl cations. The identified fragments are consistent with those found in previous investigations concerning the photochemical stability of the same class of molecules. This parallelism showcases a similarity in the behaviour of tetrazoles under EI-MS and UV-irradiation in the inert environment of cryogenic matrices of noble gases, providing efficient tools for reactivity predictions, whether for analytical ends or more in-depth studies. Theoretical calculations provide complementary information to articulate predictions of resulting products.

scholarly journals A multicolor and ratiometric fluorescent sensing platform for metal ions based on arene–metal-ion contact

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Anna Kanegae ◽  
Yusuke Takata ◽  
Ippei Takashima ◽  
Shohei Uchinomiya ◽  
Ryosuke Kawagoe ◽  
...  
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Near Infrared ◽  
Molecular Design ◽  
Theoretical Calculations ◽  
Probe Design ◽  
One Pot ◽  
Fluorescent Sensing ◽  
Sensing Platform ◽  
Ratiometric Detection

AbstractDespite continuous and active development of fluorescent metal-ion probes, their molecular design for ratiometric detection is restricted by the limited choice of available sensing mechanisms. Here we present a multicolor and ratiometric fluorescent sensing platform for metal ions based on the interaction between the metal ion and the aromatic ring of a fluorophore (arene–metal-ion, AM, coordination). Our molecular design provided the probes possessing a 1,9-bis(2′-pyridyl)-2,5,8-triazanonane as a flexible metal ion binding unit attached to a tricyclic fluorophore. This architecture allows to sense various metal ions, such as Zn(II), Cu(II), Cd(II), Ag(I), and Hg(II) with emission red-shifts. We showed that this probe design is applicable to a series of tricyclic fluorophores, which allow ratiometric detection of the metal ions from the blue to the near-infrared wavelengths. X-ray crystallography and theoretical calculations indicate that the coordinated metal ion has van der Waals contact with the fluorophore, perturbing the dye’s electronic structure and ring conformation to induce the emission red-shift. A set of the probes was useful for the differential sensing of eight metal ions in a one-pot single titration via principal component analysis. We also demonstrate that a xanthene fluorophore is applicable to the ratiometric imaging of metal ions under live-cell conditions.

Highly Sensitive Near-Infrared Imaging of Peroxynitrite Fluxes in Inflammation Progress

2021 ◽  
Vol 93 (5) ◽  
pp. 3035-3041
Author(s):  
Zhao Wang ◽  
Weiwei Wang ◽  
Pengzhan Wang ◽  
Xinjian Song ◽  
Zhiqiang Mao ◽  
...  
Keyword(s):  
Near Infrared ◽  
Infrared Imaging ◽  
Near Infrared Imaging ◽  
Highly Sensitive

scholarly journals Structure-Activity Relationships of Sandalwood Odorants: Synthesis of a New Campholene Derivative

2010 ◽  
Vol 5 (9) ◽  
pp. 1934578X1000500
Author(s):  
Iris Stappen ◽  
Joris Höfinghoff ◽  
Gerhard Buchbauer ◽  
Peter Wolschann
Keyword(s):  
Structural Changes ◽  
Great Influence ◽  
Complete Loss ◽  
Side Chain ◽  
Side Chains ◽  
Quaternary Carbon ◽  
Structural Modifications ◽  
Structure Activity ◽  
Highly Sensitive ◽  
Sandalwood Odorants

Structural modifications of natural (-)-( Z)-β-santalol have shown that the sandalwood odor impression is highly sensitive, even to small structural changes. Particularly, the substitution of the quaternary carbon is of great influence on the scent. Epi-compounds with side chains in the endo-position possess sandalwood odor in only a few derivatives, whereas modifications at this side chain, as well as modification at the bicyclic ring systems mostly lead to a complete loss of sandalwood fragrance.

Effects of Metal Stress on Visible/Near-Infrared Reflectance Spectra of Vegetation

2011 ◽  
Vol 347-353 ◽  
pp. 2735-2738 ◽  
Author(s):  
Guang Yu Chi ◽  
Yi Shi ◽  
Xin Chen ◽  
Jian Ma ◽  
Tai Hui Zheng
Keyword(s):  
Heavy Metal ◽  
Structural Changes ◽  
Near Infrared ◽  
Leaf Surface ◽  
Spectral Response ◽  
Spectral Characteristics ◽  
Surface Characteristics ◽  
Heavy Metal Stress ◽  
Metal Stress ◽  
Near Infrared Reflectance

Vegetation which suffers from heavy metal stresses can cause changes of leaf color, shape and structural changes. The spectral characteristics of vegetation leaves is related to leaf thickness, leaf surface characteristics, the content of water, chlorophyll and other pigments. So the eco-physiology changes of plants can be reflected by spectral reflectance. Studies on the spectral response of vegetation to heavy metal stress can provide a theoretical basis for remote sensing monitoring of metal pollution in soils. In recent decades, there are substantial amounts of literature exploring the effects of heavy metals on vegetation spectra.

Effects of age and maternal reactivity on the stress response of the pituitary-adrenocortical axis and the sympathetic nervous system in neonatal pigs

1999 ◽  
Vol 68 (3) ◽  
pp. 519-526 ◽  
Author(s):  
E. Kanitz ◽  
W. Otten ◽  
G. Nürnberg ◽  
K. P. Brüssow
Keyword(s):  
Stress Reactivity ◽  
Acth Stimulation Test ◽  
Acth Stimulation ◽  
Acth Challenge ◽  
Neonatal Pigs ◽  
Age Related ◽  
Highly Sensitive ◽  
Function Test ◽  
Adrenal Response ◽  
Different Levels

AbstractThe study was conducted to investigate the adreno cortical capacity after injection of ACTH and the sensitivity of the pituitary and the adrenal to immobilization in neonatal pigs at different ages. Furthermore, the endocrine reactivity of the offspring was compared with the stress reactivity of their mothers. Four piglets were selected from each of six different litters and subjected to an immobilization test and an adrenal function test using synthetic ACTH1-24 at the ages of 7, 21 and 35 days; the six sows were also subjected to restraint and an ACTH stimulation test. Plasma β-endorphin, norepinephrine and epinephrine concentrations were measured in blood samples taken 2 min after restraint and cortisol concentrations were measured 60 min after ACTH administration. A highly sensitive adrenal response was demonstrated in both sows and piglets and adrenal reactivity showed also a considerable consistency over time within sows. In neonatal pigs, the cortisol response to ACTH was greatest on day 7 and decreased up to day 35. Plasma epinephrine and norepinephrine levels after the 2-min immobilization were also higher at day 7 compared with the other ages (P < 0·01). Piglets from sows, classified as high reacting according to their cortisol or epinephrine response, also showed significantly higher cortisol levels after ACTH challenge at all ages and significantly higher epinephrine levels after restraint at day 7 than piglets from low reacting sows. The results show an age-related change of pituitary-adrenocortical and sympatho-adrenomedullary responses in neonatal pigs and an absence of a stress hyporesponsive period at all ages studied. The results also indicate different levels of excitability in the offspring depending on the maternal stress reactivity.

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