Intermolecular charge transfer as evidence for unusual O–H⋯C(sp3) hydrogen bond

Isaev, A. N.

doi:10.1016/j.comptc.2016.06.014

Cited by 16 publications

(13 citation statements)

References 116 publications

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“…The red shift of the μ 3 -O–H stretch is consistent with other spectroscopic studies where OH−CH 3 hydrogen bonding has been observed . While traditional descriptions of hydrogen-bond formation require the hydrogen bond acceptor to have available electron lone pairs, evidence of hydrogen bonding that involves any molecule with electron rich regions including aromatic − and aliphatic ,− compounds has been observed and modeled. Computational studies have shown that hydrogen bonding between −OH groups and aliphatic and aromatic groups is accompanied by transfer of electron density from the hydrogen-bond acceptor to the σ*-antibonding orbital of the donor O–H bond.…”

Section: Discussionsupporting

confidence: 85%

“…Computational studies have shown that hydrogen bonding between −OH groups and aliphatic and aromatic groups is accompanied by transfer of electron density from the hydrogen-bond acceptor to the σ*-antibonding orbital of the donor O–H bond. Occupation of the O–H σ*-antibonding orbital weakens the bond, which results in an elongation and a red shift of the ν(O–H) vibration that correlates with the extent of charge transfer. − …”

Section: Discussionmentioning

confidence: 99%

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Benzene, Toluene, and Xylene Transport through UiO-66: Diffusion Rates, Energetics, and the Role of Hydrogen Bonding

et al. 2018

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The high-energy demand of benzene, toluene, and xylene (BTX) separation highlights the need for improved nonthermal separation techniques and materials. Because of their high surface areas, tunable structures, and chemical stabilities, metal–organic frameworks (MOFs) are a promising class of materials for use in more energy efficient, adsorption-based separations. In this work, BTX compounds in the pore environment of UiO-66 were systematically examined using in situ infrared (IR) spectroscopy to understand the fundamental interactions that influence molecular transport through the MOF. Isothermal diffusion experiments revealed BTX diffusivities between 10–8 and 10–12 cm2 s–1, where the rate follows the trend: o-xylene < m-xylene < p-xylene. Corresponding activation energies of diffusion (E diff) were determined to be 44 kJ mol–1 for the xylene isomers and 34 kJ mol–1 for both benzene and toluene, with the diffusion-limiting barrier identified to be molecular passage through the small triangular pore apertures of UiO-66. Furthermore, IR spectroscopy and computational methods showed the formation of two types of hydrogen bonds between BTX molecules and the μ3-OH groups located in the tetrahedral cavities of UiO-66, which indicates that BTX molecules are capable of fully accessing the inner pore environment of the MOF. The molecular-level insight into the diffusion mechanism and energetics of BTX transport through UiO-66 presented in this work provides rich insight for the design of next-generation MOFs for cost-effective separation processes.

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Section: Discussionsupporting

confidence: 85%

Section: Discussionmentioning

confidence: 99%

Benzene, Toluene, and Xylene Transport through UiO-66: Diffusion Rates, Energetics, and the Role of Hydrogen Bonding

et al. 2018

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“…Previous research has shown similar spectroscopic evidence for hydrogen bonding of saturated alkanes to the surface of zeolites . Within those systems, surface hydroxyl groups have been suggested to act as Brønsted acid hydrogen bond donors to slightly more electronegative alkanes. , Furthermore, theoretical studies of alkane hydrogen bond formation indicate that the σ-bonding orbital of the C–H bond can transfer electron density into the σ*-antibonding orbital of the O–H bond, which weakens the bond, thereby redshifting the O–H stretching frequency. , For n -butane hydrogen bonded to UiO-66, we observed an O–H redshift of 34 cm –1 . The complete disappearance of the free hydroxyl band at 3674 cm –1 suggests that butane can access every hydroxyl group within the MOF.…”

Section: Results and Discussionmentioning

confidence: 82%

Alkane–OH Hydrogen Bond Formation and Diffusion Energetics of n-Butane within UiO-66

et al. 2017

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Hydrocarbon diffusion and binding within porous molecular networks are critical to catalysis, separations, and purification technologies. Fundamental insight into n-butane uptake and mobility within a new class of materials for separations, metal−organic frameworks (MOFs), has been gained through in situ infrared spectroscopy. These ultrahigh vacuum (UHV) based measurements revealed that adsorption of n-butane within UiO-66 proceeds through the formation of hydrogen bonds between the alkane molecules and hydroxyl groups located at the inorganic node of UiO-66. Modeling the gas transport of n-butane with Fick's second law yielded diffusion coefficients at several temperatures. The Arrhenius parameter for the activation energy of diffusion was found to be 21.0 ± 1.2 kJ/mol. These studies have further shown that the rate-determining step for diffusion is likely the dissociation of n-butane from a binding site located within the tetrahedral pores of UiO-66.

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“…Furthermore, the methane–water system, which can display a configuration involving a short H 4 C···H-OH contact, has been extensively investigated by means of laser spectroscopy 25 , microwave spectrometry 26 , and also theoretically 27 – 30 . The CH 4 ···H 2 O adduct has been proposed 31 as a precursor of CH 5 + , with a calculated binding energy of 1 kcal mol −1 , increasing up to 10 kcal mol −1 in the case of CH 4 ···H 3 O + 32 . Similar interactions have been computationally predicted for the adsorption of water on CH 3 :Si(111) 33 .…”

Section: Introductionmentioning

confidence: 99%

Methyl groups as widespread Lewis bases in noncovalent interactions

Loveday

Echeverría

2021

Nat Commun

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It is well known that, under certain conditions, C(sp3) atoms behave, via their σ-hole, as Lewis acids in tetrel bonding. Here, we show that methyl groups, when bound to atoms less electronegative than carbon, can counterintuitively participate in noncovalent interactions as electron density donors. Thousands of experimental structures are found in which methyl groups behave as Lewis bases to establish alkaline, alkaline earth, triel, tetrel, pnictogen, chalcogen and halogen bonds. Theoretical calculations confirm the high directionality and significant strength of the interactions that arise from a common pattern based on the electron density holes model. Moreover, despite the absence of lone pairs, methyl groups are able to transfer charge from σ bonding orbitals into empty orbitals of the electrophile to reinforce the attractive interaction.

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Intermolecular charge transfer as evidence for unusual O–H⋯C(sp3) hydrogen bond

Cited by 16 publications

References 116 publications

Benzene, Toluene, and Xylene Transport through UiO-66: Diffusion Rates, Energetics, and the Role of Hydrogen Bonding

Benzene, Toluene, and Xylene Transport through UiO-66: Diffusion Rates, Energetics, and the Role of Hydrogen Bonding

Alkane–OH Hydrogen Bond Formation and Diffusion Energetics of n-Butane within UiO-66

Methyl groups as widespread Lewis bases in noncovalent interactions

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