Low Bending Vibrations of Crystalline Water Molecules: An Ongoing Quest or a Final Word – Topical Review – A Tribute to Academician Bojan Šoptrajanov

Pejov, Ljupčo; Jovanovski, Gligor

doi:10.20903/csnmbs.masa.2017.38.1.102

Cited by 3 publications

(6 citation statements)

References 38 publications

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“…Another contribution is also observed around 1550–1560 cm –1 . Such band can also be attributed to a water bending mode . This band could be due to crystalline water in strong interaction with the anion .…”

Section: Resultssupporting

confidence: 63%

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Tuning the Nature of the Anion in Hydrated Layered Double Hydroxides for H₂ Production under Ionizing Radiation

Lainé

Liao

Varenne

et al. 2018

ACS Appl. Nano Mater.

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Layered double hydroxides (LDHs) are adsorbent materials able to store significant amounts of anionic radionuclides under various levels of hydrations. In view of this storage application, it is crucial to understand their evolution under ionizing radiation, particularly as a function of their hydration state. We thus synthesized four LDHs, with Mg/Al molar ratio ∼3.5 and four different anions: NO3 –, CO3 2–, ClO4 –, and Cl– chosen for their contrasted behavior toward ionizing radiation. For all these materials, the initial interlamellar distance increases slightly within the first step of relative humidity (RH), 0–3%, and remains constant in the 3–74% RH range. Infrared spectroscopy reveals a lowering of the anion symmetry when it is confined in LDHs, caused by the interaction with surface OH groups and water molecules together with a decrease of degrees of freedom upon confinement. When RH increases, the environment of the anions becomes more and more symmetric. Under ionizing radiation, the nature of the anion in the interlamellar space and the hydration state control the H2 production. The LDH containing nitrate anions leads to low H2 yields, as nitrate anions scavenge precursors of dihydrogen. Materials containing perchlorate (inert toward ionizing radiation) and carbonate (hydroxyl scavenger) anions lead to very similar H2 yields, which increase in the 0–3% RH range and then remain stable in the 3–74% range, with a maximum value approximately half of that obtained for bulk water. This shows that the material itself contains hydroxyl scavengers. The sample containing chloride anions produces the highest H2 amounts, with H2 yields twice higher than the yield measured in bulk water. This peculiar behavior can be linked to specific reactions involving confined chloride anions. This work shows that the anion of the LDH sample can be selected depending on the applications.

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Section: Resultssupporting

confidence: 63%

“…Such band can also be attributed to a water bending mode. 48 This band could be due to crystalline water in strong interaction with the anion. 48 Note that the same type of contribution was observed for all samples (Figures S5−S8).…”

mentioning

confidence: 99%

Tuning the Nature of the Anion in Hydrated Layered Double Hydroxides for H₂ Production under Ionizing Radiation

Lainé

Liao

Varenne

et al. 2018

ACS Appl. Nano Mater.

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“…The lowering of the bending mode wavenumber can be due to the flattening of the corresponding potential energy surface which brings the energy levels closer . In some specific cases (solid-state hydrates with water molecules in strong interaction with ions), very low-lying bending vibrations are detected, with typical wavenumbers ranging from 1590 to 1430 cm –1 . In contrast, a previous study indicates that anions (such as ClO 4 – ) blue-shift the bending mode .…”

Section: Resultsmentioning

confidence: 88%

“…49 In some specific cases (solid-state hydrates with water molecules in strong interaction with ions), very low-lying bending vibrations are detected, with typical wavenumbers ranging from 1590 to 1430 cm −1 . 50 In contrast, a previous study indicates that anions (such as ClO 4 − ) blue-shift the bending mode. 51 In the present case, the softening of the bending suggests that, upon high confinement between the two walls, the dominating effect is a HOH angle change which becomes larger or that the mean water−water H bond angle increases.…”

Section: Analysis Of the O−h Stretching Bandmentioning

confidence: 81%

Water Adsorption in Single- and Double-Walled Inorganic Nanotubes

et al. 2019

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Imogolite forms a class of inorganic nanotubes whose inner and outer surfaces can be tuned on a molecular level. The combination of this property with their monodisperse diameters makes imogolites ideal to study water confinement in a one-dimensional environment. Here, we have investigated, by means of infrared (IR) spectroscopy, water confined in two types of germanium-based imogolites: (i) the hydroxylated imogolite (Ge-IMO-OH), a doublewalled structure with an interstitial space of about 2 Å and the interior of the tube covered by Ge−OH groups; and (ii) the hybrid, methylated, imogolite (Ge-IMO-CH 3 ), a single-walled structure with Ge−CH 3 groups covering the interior of the tube. In both cases, the external surface is covered by Al 2 -(μOH) groups. Small-angle Xray scattering has also been exploited to determine the nanotube geometry of the two confining systems. Using thermogravimetric analysis, we show here that the interstitial space of Ge-IMO-OH fills with water in a significant proportion. Indeed, at 81% relative humidity (RH), 5% of the weight loss is due to water molecules in this interstitial space, whereas 13% of the weight loss is attributed to water molecules filling the other porosities. The IR study, in turn, reveals that water molecules start filling the interstitial space at very low RH values and are weakly H-bonded while exhibiting a low-frequency bending mode. This low bending value at around 1550 cm −1 is indicative of a large H−O−H angle (as compared to the liquid water H bond angle). Such a large angle and weak hydrogen bonding are probably related to the strong confinement of water molecules between the two inner walls. Water also fills up the interior of the tube of Ge-IMO-OH from low RH values all the way to maximum RH. In this case, however, water molecules aggregate to form liquid water. In Ge-IMO-CH 3 , the filling of the porosities outside the tubes increases continuously with hydration. Moreover, a small proportion of weakly H-bonded water molecules enter in the hydrophobic cavity. The number of these internal water molecules is larger than what was observed in the silicon imogolite counterpart Si-IMO-CH 3 because of the larger diameter of Ge-IMO-CH 3 internal cavity.

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“…[50] However, in indole, this bond distance is shorter, 1.37 Å, indicating that substituent has an impact on the geometry of the indole moiety. [51] On the other hand, the bond distance is slightly longer for entry 10. Interestingly, the C¼O bond distance is 1.222 Å, which is similar for all compounds.…”

Section: Palladium-catalyzed Cyclizationmentioning

confidence: 98%

Palladium‐catalyzed cyclization of 2‐alkynyl‐N‐ethanoyl anilines to indoles: synthesis, structural, spectroscopic, and mechanistic study

Hoque

Halim²,

Sarwar

et al. 2015

J of Physical Organic Chem

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This study reports a facial regio‐selective synthesis of 2‐alkyl‐N‐ethanoyl indoles from substituted‐N‐ethanoyl anilines employing palladium (II) chloride, which acts as a cyclization catalyst. The mechanistic trait of palladium‐based cyclization is also explored by employing density functional theory. In a two‐step mechanism, the palladium, which attaches to the ethylene carbons, promotes the proton transfer and cyclization. The gas‐phase barrier height of the first transition state is 37 kcal/mol, indicating the rate‐determining step of this reaction. Incorporating acetonitrile through the solvation model on density solvation model reduces the barrier height to 31 kcal/mol. In the presence of solvent, the electron‐releasing (–CH3) group has a greater influence on the reduction of the barrier height compared with the electron‐withdrawing group (–Cl). These results further confirm that solvent plays an important role on palladium‐catalyzed proton transfer and cyclization. For unveiling structural, spectroscopic, and photophysical properties, experimental and computational studies are also performed. Thermodynamic analysis discloses that these reactions are exothermic. The highest occupied molecular orbitallowest unoccupied molecular orbital gap (4.9–5.0 eV) confirms that these compounds are more chemically reactive than indole. The calculated UV–Vis spectra by time‐dependent density functional theory exhibit strong peaks at 290, 246, and 232 nm, in good agreement with the experimental results. Moreover, experimental and computed 1H and 13C NMR chemical shifts of the indole derivatives are well correlated. Copyright © 2015 John Wiley & Sons, Ltd.

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Low Bending Vibrations of Crystalline Water Molecules: An Ongoing Quest or a Final Word – Topical Review – A Tribute to Academician Bojan Šoptrajanov

Cited by 3 publications

References 38 publications

Tuning the Nature of the Anion in Hydrated Layered Double Hydroxides for H₂ Production under Ionizing Radiation

Tuning the Nature of the Anion in Hydrated Layered Double Hydroxides for H₂ Production under Ionizing Radiation

Water Adsorption in Single- and Double-Walled Inorganic Nanotubes

Palladium‐catalyzed cyclization of 2‐alkynyl‐N‐ethanoyl anilines to indoles: synthesis, structural, spectroscopic, and mechanistic study

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Low Bending Vibrations of Crystalline Water Molecules: An Ongoing Quest or a Final Word – Topical Review – A Tribute to Academician Bojan Šoptrajanov

Cited by 3 publications

References 38 publications

Tuning the Nature of the Anion in Hydrated Layered Double Hydroxides for H2 Production under Ionizing Radiation

Tuning the Nature of the Anion in Hydrated Layered Double Hydroxides for H2 Production under Ionizing Radiation

Water Adsorption in Single- and Double-Walled Inorganic Nanotubes

Palladium‐catalyzed cyclization of 2‐alkynyl‐N‐ethanoyl anilines to indoles: synthesis, structural, spectroscopic, and mechanistic study

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Tuning the Nature of the Anion in Hydrated Layered Double Hydroxides for H₂ Production under Ionizing Radiation

Tuning the Nature of the Anion in Hydrated Layered Double Hydroxides for H₂ Production under Ionizing Radiation