Vibrational study of isolated 18-crown-6 ether complexes with alkaline-earth metal cations

Gámez, Francisco; Hurtado, Paola; Martínez–Haya, Bruno; Berden, Giel; Oomens, Jos

doi:10.1016/j.ijms.2011.06.015

Cited by 44 publications

(44 citation statements)

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“…Their stronger binding was demonstrated both in absorption and fluorescence experiments, in which fluorescence increased by up to 100 Â and F F reached values of approximately 0.20. The stronger binding of alkaline earth metal cations is in accordance with published data in which different methods (i.e., absorption spectroscopy of chromoionophores [27], polarography [28], or laser infrared multiple photon dissociation spectroscopy [23]) were applied.…”

Section: Discussionsupporting

confidence: 87%

“…The K D values for alkali metal cations binding were found to range from hundreds of micromoles to tens of millimoles (see Table 1), which is in agreement with our previous data for the complexation of the 1-aza-15-crown-5 moiety to Na þ in THF [14], as well as the data published by other authors for the aza-crowns and cations involved in this study [1,23,26]. K D values of alkaline earth metal cations reached usually lower values in micromolar range.…”

Section: Titration With Metal Cationssupporting

confidence: 92%

“…Such behavior can be attributed to the interaction of the cation and the peripheral donor nitrogen, whose lone electron pair cannot contribute to the p-electron system of the macrocycle any more, leading to the blue shift of the Q band maximum. Binding of alkaline earth metal cations into the studied aza-crowns was shown to be stronger in comparison with alkali metal cations due to the increased cation charge from 1 þ to 2þ, while keeping the cation size constant [23]. Tighter binding of divalent ions was also in accordance with the fluorescence data described below.…”

Section: Titration With Metal Cationssupporting

confidence: 81%

“…The diameters of alkaline earth metal cations Mg 2þ , Ca 2þ , and Ba 2þ are 0.72, 1.00, and 1.35 Å, respectively. Those of the alkali metal cations Li þ , Na þ , and K þ are 0.76, 1.02, and 1.38 Å, respectively [23]. Hence, alkaline earth metal cations are roughly similar in size in this series, but being divalent cations, they possess higher electron density in comparison with alkali metal cations.…”

Section: Titration With Metal Cationsmentioning

confidence: 81%

See 3 more Smart Citations

The role of the size of aza-crown recognition moiety in azaphthalocyanine fluorescence sensors for alkali and alkaline earth metal cations

et al. 2015

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Section: Discussionsupporting

confidence: 87%

Section: Titration With Metal Cationssupporting

confidence: 92%

Section: Titration With Metal Cationssupporting

confidence: 81%

Section: Titration With Metal Cationsmentioning

confidence: 81%

See 2 more Smart Citations

The role of the size of aza-crown recognition moiety in azaphthalocyanine fluorescence sensors for alkali and alkaline earth metal cations

et al. 2015

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“…In the case of hydronium trapped in 18C6, this approach yields a simple qualitative picture for the origin of the extreme spectral broadening as a consequence of photoinduced structural deformations toward the intermolecular proton transfer asymptote. (14,19). This is consistent with the calculated bond lengths highlighted in Fig.…”

Section: Significancesupporting

confidence: 91%

Hidden role of intermolecular proton transfer in the anomalously diffuse vibrational spectrum of a trapped hydronium ion

Craig

Menges

Duong

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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We report the vibrational spectra of the hydronium and methylammonium ions captured in the C 3v binding pocket of the 18-crown-6 ether ionophore. Although the NH stretching bands of the CH 3 NH 3 + ion are consistent with harmonic expectations, the OH stretching bands of H 3 O + are surprisingly broad, appearing as a diffuse background absorption with little intensity modulation over 800 cm −1 with an onset ∼400 cm −1 below the harmonic prediction. This structure persists even when only a single OH group is present in the HD 2 O + isotopologue, while the OD stretching region displays a regular progression involving a soft mode at about 85 cm −1. These results are rationalized in a vibrationally adiabatic (VA) model in which the motion of the H 3 O + ion in the crown pocket is strongly coupled with its OH stretches. In this picture, H 3 O + resides in the center of the crown in the vibrational zeropoint level, while the minima in the VA potentials associated with the excited OH vibrational states are shifted away from the symmetrical configuration displayed by the ground state. Infrared excitation between these strongly H/D isotope-dependent VA potentials then accounts for most of the broadening in the OH stretching manifold. Specifically, low-frequency motions involving concerted motions of the crown scaffold and the H 3 O + ion are driven by a Franck-Condon-like mechanism. In essence, vibrational spectroscopy of these systems can be viewed from the perspective of photochemical interconversion between transient, isomeric forms of the complexes corresponding to the initial stage of intermolecular proton transfer.vibrational spectroscopy | hydrogen bonding | vibrationally adiabatic | proton transfer

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Mechanistic Aspects and Side Reactions during Reversible Mg Deposition and Oxygen Reduction on a Pt Film Electrode in BMP‐TFSI‐Based Electrolytes: A DEMS Study

Jusys

Behm

2023

ChemElectroChem

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Reversible Mg deposition/stripping and O 2 reduction/evolution on a Pt film electrode in neat and O 2 -saturated 1-butyl-1methylpyrrolidinium bis(trifluoromethylsulfonyl) imide (BMP-TFSI) electrolytes, containing Mg(TFSI) 2 and/or Mg(BH 4 ) 2 as Mg source as well as Mg(BH 4 ) 2 and/or the crown ether 18-c-6 as additive, were investigated by online differential electrochemical mass spectrometry (DEMS) and by scanning electron microscopy/energy dispersed X-ray spectroscopy. Combined cyclic voltammetry and DEMS measurements reveal a complex network of partial reactions, including borohydride electrooxidation by reaction with water or O 2 , chemical bulk reaction of these components, as well as electro-oxidation of H 2 , and electrolyte decomposition, in addition to the primary reactions Mg deposition/stripping and ORR/OER. They provide detailed insights into the potential dependent reactions occurring under these conditions, demonstrating that also the additive 18-c-6 undergoes decomposition upon reduction of Mg 2 + . Contributions from chemical bulk reactions are resolved by DEMS measurements in borohydride containing solution without a Pt electrode. Electrocatalytic borohydride oxidation, explored by similar measurements with a Pt electrode, can lead to H 2 or H + formation. Under open circuit potential conditions, charge compensation by the ORR results in the formation of a mixed potential. Consequences of these findings for applications in Mg-air batteries are discussed.

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Vibrational study of isolated 18-crown-6 ether complexes with alkaline-earth metal cations

Cited by 44 publications

References 50 publications

The role of the size of aza-crown recognition moiety in azaphthalocyanine fluorescence sensors for alkali and alkaline earth metal cations

The role of the size of aza-crown recognition moiety in azaphthalocyanine fluorescence sensors for alkali and alkaline earth metal cations

Hidden role of intermolecular proton transfer in the anomalously diffuse vibrational spectrum of a trapped hydronium ion

Mechanistic Aspects and Side Reactions during Reversible Mg Deposition and Oxygen Reduction on a Pt Film Electrode in BMP‐TFSI‐Based Electrolytes: A DEMS Study

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