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91.
92.
Dr. Perumal Venkatesan Dr. Margarita Cerón Dr. Enrique Pérez-Gutiérrez Armando E. Castillo Dr. Subbiah Thamotharan Fernando Robles Dr. Maxime A. Siegler Prof. M. Judith Percino 《ChemistryOpen》2019,8(4):483-496
Experimental and theoretical insights into the nature of intermolecular interactions and their effect on optical properties of 1-allyl-4-(1-cyano-2-(4-dialkylaminophenyl)vinyl)pyridin-1-ium bromide salts ( I and II ) are reported. A comparison of optical properties in solution and in the solid-state of the salts ( I and II ) with their precursors ( Ia and IIa ) is made. The experimental absorption maxima (λmax) in CHCl3 is at 528 nm for I and at 542 nm for II , and a strong bathochromic shift of ∼110 nm is observed for salts I and II compared with their precursors. The absorption bands in solid-state at ∼627 nm for I and at ∼615 nm for II that are assigned to charge transfer (CT) effect. The optical properties and single crystal structural features of I and II are explored by experimental and computational tools. The calculated λmax and the CT are in good agreement with the experimental results. The intermolecular interactions existing in the crystal structures and their energies are quantified for various dimers by PIXEL, QTAIM and DFT approaches. Three types of interactions, (i) the cation⋅⋅⋅cation interactions, (ii) cation⋅⋅⋅anion interactions and (iii) anion⋅⋅⋅anion interactions are observed. The cationic moiety is mainly destabilized by C−H⋅⋅⋅N/π and π⋅⋅⋅π interactions whereas the cation and anion moiety is predominantly stabilized by strong C−H⋅⋅⋅Br− interactions in both structures. The existence of charge transfer between cation and anion moieties in these structures is established through NBO analysis. 相似文献
93.
Nickel oxide and chromium-doped nickel oxide (Ni0.95Cr0.03O1−δ
) were prepared by thermal decomposition of nitrates. The obtained NiO and Ni0.95Cr0.03O1−δ
samples were utilized as sensing electrodes (SEs) in yttria-stabilized zirconia (YSZ)-based sensors for detection of NO2 at 800 °C under wet condition (5 vol.% H2O). While the mixed-potential-type planar sensor attached with NiO-SE gave rather large NO2 sensitivity, the sensor attached with Ni0.95Cr0.03O1−δ
-SE exhibited fast recovery rate with an acceptable sensitivity. The Δemf (electromotive force) of the sensors varied linearly
with NO2 concentration in the examined range of 50–400 ppm on a logarithmic scale. Based on the results of measurements for polarization,
complex impedance and gas phase catalysis, the fast recovery was attributable to the high rate for the anodic reaction of
O2 at the Ni0.95Cr0.03O1−δ
/YSZ interface, and the lower NO2 sensitivity was caused by both the high rate for the anodic reaction of O2 and the high degree for the gas phase conversion of NO2 to NO. 相似文献
94.
95.
Methanol-swollen Nafion beads were used as microreactors to control the photochemical reaction pathways. Product selectivity in three unimolecular reactions, namely, the photo-Fries rearrangement of naphthyl esters, Norrish Type I reaction of 1-phenyl-3-p-tolyl-propan-2-one and Norrish Type I and Type II reactions of benzoin alkyl ethers were examined. The influence of cations over the photodimerization of acenaphthylene and cross-photodimerization between acenaphthylene and N-benzyl maleimide included within Nafion were also examined. The photochemical behaviors of the above substrates were significantly altered within Nafion compared with their solution photochemistry. Of particular interest, the product distributions were found to depend on the counter cations of Nafion. 相似文献
96.
A series of amidoketophosph(on)ates of general structure PhCH2OCONHCH(R)COCHR'(CH2)n(O)P(O2-)(O)R' (R = H, CH3; R' = H, CH3; n = 0, 1; R' = H, CH3, Et, Ph) have been prepared as a potential source of beta-lactamase inhibitors. The phosphonates (n = 0) were obtained by means of the Arbuzov reaction while most of the phosphates were achieved from reaction of phosph(or/on)ic acids with the appropriate diazoketone PhCH2OCONHCH(R)COCR'N2. The electrophilicity of the carbonyl group in the resulting phosph(on)ates was assessed by the degree of hydration in aqueous solution, determined from NMR spectra. These compounds inhibited typical class C and class D beta-lactamases, particularly the latter group, but showed no activity against class A enzymes. To enhance the carbonyl electrophilicity, an alpha-difluorinated analogue (R = H, CHR' = CF2, n = 0, R' = Et) was also prepared, but no enhanced inhibitory activity was observed. All evidence suggested that these compounds inhibited in the carbonyl form rather than by formation of tetrahedral adducts at the beta-lactamase active site. They show promise as leads to specific class D beta-lactamase inhibitors. 相似文献
97.
Treatment of 1 equiv of 1,3-bis(bromomethyl)benzene and 2,6-bis(bromomethyl)pyridine with 1 equiv of indole in the presence of NaH in THF afforded the symmetrical cyclophanes 1 and 2. Using similar methodology, cylindrical cyclophanes 3 and 4 were obtained from 2 equiv of 1,3,5-trimethyl-2,4,6-tris(bromomethyl)benzene and 1,3,5-tris(bromomethyl)benzene with 3 equiv of indole. 相似文献
98.
In this study, inclusion of 10 guest molecules, adamantyl and naphthyl carboxylic acids with different structural and electronic properties, within a synthetic cavitand octa acid was probed by isothermal calorimetry, 1D and 2D 1H nuclear magnetic resonance spectroscopy, and molecular dynamic simulations. Under the condition of the experiments (pH ~ 8.7), the guests were included as carboxylate anions with the polar anionic head group facing water and hydrophobic carbon skeleton buried within the cavitand, forming 1:1 host to guest complexes. Importance of weak interactions between the guest and the cavitand interior is reflected in the measured negative ΔH values. Although ΔH was negative for all guests, ΔS was positive for adamantyl guests and negative for naphthyl guests. Quite likely the difference in hydrophobicity between the 2 sets of molecules and the strength of interaction between the guest and the host are responsible for the sign difference in ΔS between the 2 series. The importance of steric factor during inclusion of naphthyl carboxylic acids within octa acid cavity is brought out by the difference in thermodynamic parameters between the 1‐ and 2‐substituted naphthyl carboxylic acids; 2‐naphthyl carboxylic acids that can penetrate deeply have larger ?ΔH and 1‐naphthyl carboxylic acids that can only enter the cavity in an angle have smaller ?ΔH. As expected, based on the well‐known concept of “enthalpy‐entropy compensation,” the molecules that have large ?ΔH are accompanied by large ?ΔS. 相似文献
99.
Sofyan A. Taya Anas A. Alkanoo Nambi R. Ramanujam Perumal Mahalakshmi Dhasarathan Vigneswaran 《Optical and Quantum Electronics》2018,50(5):222
Two ternary photonic crystals are proposed for sensing applications. The first one is composed of an air layer as an analyte sandwiched between two double negative material (DNM) layers whereas the second one consists of an air layer sandwiched between two epsilon negative material (ENM) layers. The transmission spectrum is studied for two different values of the refractive index of the analyte layer with ?n = 0.01. A specific peak in the transmission spectrum is observed and the wavelength at which the peak occurs is determined. The wavelength shift due to any change in the index of the analyte layer is also determined. The effect of varying the parameters of the DNM and ENM on the sensitivity of the sensor is discussed. It is found that the sensitivity of the structure ENM/air/ENM is much greater than that of the structure DNM/air/DNM and it is estimated as 26 times of the sensitivity of the latter structure. 相似文献
100.
Pure and urea-doped gamma-glycine (γ-glycine) single crystals were grown by solution method with slow evaporation technique. When urea was added as dopant, morphological alterations were noticed in γ-glycine crystals. Structural characterization of the grown crystals was carried out by single and powder X-ray diffraction (XRD) methods and it is observed that the samples crystallize in non-centrosymmetric space groups. UV-visible transmittance studies were performed to analyse optical transparency of pure and urea-doped γ-glycine crystals and found that the crystals were transparent in the entire visible-NIR region. Density and melting point of the grown crystals were measured. Second harmonic generation (SHG) for the grown crystals of this work was confirmed using Nd:YAG laser. Thermogravimetric and differential thermal analyses (TG/DTA) thermograms reveal that the materials have good thermal stability. From Microhardness studies, it is observed that urea-doped γ-glycine crystal is harder than pure (undoped) sample. 相似文献