Blue-Shift in the Frequencies of the CH Stretches of Chloro- and Fluoroform Induced by C–H...π Hydrogen Bonding with Benzene Derivatives: the Influence of Electron Donating and Withdrawing Substituents

Reimann, Bernd; Buchhold, K.; Vaupel, Sascha; Brutschy, Bernhard

doi:10.1524/zpch.2001.215.6.777

Cited by 20 publications

(3 citation statements)

References 21 publications

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“…In 1999, an increase of C–H stretching frequency was reported in the complex between chloroform and fluorobenzene by using double-resonance IR ion-depletion spectroscopy . In addition, a surprising shortening of the C–H bond was found in C–H...O/N/halogen/π H-bonds. − The BSHB is often reported for H-bond complexes formed between various proton acceptors and the proton donor C sp3 –H (C sp3 refers to the tetrahedral hybridized carbon in the molecule). ,, For example, complexation between methane, fluoroform, chloroform, bromoform, and iodoform on the one hand and water, benzene, fluorobenzene, acetylene, and ethylene ,,, on the other hand leads to a C–H bond contraction.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Aspects of Nonconventional Hydrogen Bonds in the Complexes of Aldehydes and Hydrogen Chalcogenides

et al. 2021

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Hydrogen bonds (H-bonds) in the complexes between aldehydes and hydrogen chalcogenides, XCHO...nH 2 Z with X = H, F, Cl, Br, and CH 3 , Z = O, S, Se, and Te, and n = 1,2, were investigated using high-level ab initio calculations. The C sp2 − H...O H-bonds are found to be about twice as strong as the C sp2 − H...S/Se/Te counterparts. Remarkably, the S/Se/Te−H...S/Se/Te H-bonds are 4.5 times as weak as the O−H...O ones. The addition of the second H 2 Z molecule into binary systems induces stronger complexes and causes a positive cooperative effect in ternary complexes. The blue shift of C sp2 −H stretching frequency involving the C sp2 −H...Z H-bond sharply increases when replacing one H atom in HCHO by a CH 3 group. In contrast, when one H atom in HCHO is substituted with a halogen, the magnitude of blueshifting of the C sp2 −H...Z H-bond becomes smaller. The largest blue shift up to 92 cm −1 of C sp2 −H stretching frequency in C sp2 −H...O H-bond in CH 3 CHO...2H 2 O has rarely been observed and is much greater than that in the cases of the C sp2 −H...S/Se/Te ones. The C sp2 −H blue shift of C sp2 −H...Z bonds in the halogenated aldehydes is converted into a red shift when H 2 O is replaced by a heavier analogue, such as H 2 S, H 2 Se, or H 2 Te. The stability and classification of nonconventional H-bonds including C sp2 −H...Se/Te, Te−H...Te, and Se/Te−H...O have been established for the first time.

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Section: Introductionmentioning

confidence: 99%

Theoretical Aspects of Nonconventional Hydrogen Bonds in the Complexes of Aldehydes and Hydrogen Chalcogenides

et al. 2021

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“…In a few cases, however, experiments find that the X−H stretching vibration is shifted toward higher frequency (blue-shift) in an X−H···Y hydrogen-bonded system, − where X is CF 3 and CCl 3 , and Y is triformylmethane, benzene, ethylene oxide, and dimethyl ether. A number of theoretical studies have also demonstrated that blue-shifted hydrogen bonds can be obtained at various levels of calculation. − Clearly, this challenges the generally held explanations of hydrogen bonding and the standard experimental methods of detecting hydrogen bonds, because the qualitative theoretical models mentioned above only allow for red-shifts.…”

Section: Introductionmentioning

confidence: 99%

On the Physical Origin of Blue-Shifted Hydrogen Bonds

2002

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For blue-shifted hydrogen-bonded systems, the hydrogen stretching frequency increases rather than decreases on complexation. In computations at various levels of theory, the blue-shift in the archetypical system, F(3)C-H.FH, is reproduced at the Hartree-Fock level, indicating that electron correlation is not the primary cause. Calculations also demonstrate that a blue-shift does not require either a carbon center or the absence of a lone pair on the proton donor, because F(3)Si-H.OH(2), F(2)NH.FH, F(2)PH.NH(3), and F(2)PH.OH(2) have substantial blue-shifts. Orbital interactions are shown to lengthen the X-H bond and lower its vibrational frequency, and thus cannot be the source of the blue-shift. In the F(3)CH.FH system, the charge redistribution in F(3)CH can be reproduced very well by replacing the FH with a simple dipole, which suggests that the interactions are predominantly electrostatic. When modeled with a point charge for the proton acceptor, attractive electrostatic interactions elongate the F(3)C-H, while repulsive interactions shorten it. At the equilibrium geometry of a hydrogen-bonded complex, the electrostatic attraction between the dipole moments of the proton donor and proton acceptor must be balanced by the Pauli repulsion between the two fragments. In the absence of orbital interactions that cause bond elongation, this repulsive interaction leads to compression of the X-H bond and a blue-shift in its vibrational frequency.

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“…Because of the relatively higher acidity of acetylenic CH (p K a = 25) than those of alkane (p K a = 49 for methane) and alkene (p K a = 44 for ethylene), the interaction between acetylenic CH and π-electrons is considered to be relatively stronger , and both of them are often called activated CH/π interaction . Infrared (IR) spectroscopic studies of bulk solutions have demonstrated that low-frequency shifts of the CH stretching vibration of various substituted acetylenes occur upon association with aromatic molecules .…”

Section: Introductionmentioning

confidence: 99%

A Molecular Cluster Study on Activated CH/π Interactions: Infrared Spectroscopy of Aromatic Molecule−Acetylene Clusters

et al. 2004

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CH stretching vibrations of jet-cooled benzene−acetylene and several aromatics−acetylene clusters were observed in order to characterize the intermolecular interaction, so-called activated CH/π interaction between an acidic CH group and π-electrons. The infrared−ultraviolet double resonance spectroscopic techniques were used for measuring their vibrational spectra. The antisymmetric CH stretching vibration of the acetylene moiety exhibits a remarkable low-frequency shift upon the cluster formation with the aromatic molecules, indicating such a cluster structure that the acetylenic CH group is bound to π-electrons of the aromatic ring. The low-frequency shifts observed for the clusters show a positive correlation with the π-electron density of the ring, as expected for an ordinary π-hydrogen bond. On the other hand, the polarizability of the proton-accepting molecules showed a weakly negative correlation with the CH frequency shifts. These results show that the intermolecular interaction between the activated CH group and π-electrons is characterized as a π-hydrogen bond rather than as a van der Waals interaction.

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Blue-Shift in the Frequencies of the CH Stretches of Chloro- and Fluoroform Induced by C–H...π Hydrogen Bonding with Benzene Derivatives: the Influence of Electron Donating and Withdrawing Substituents

Cited by 20 publications

References 21 publications

Theoretical Aspects of Nonconventional Hydrogen Bonds in the Complexes of Aldehydes and Hydrogen Chalcogenides

Theoretical Aspects of Nonconventional Hydrogen Bonds in the Complexes of Aldehydes and Hydrogen Chalcogenides

On the Physical Origin of Blue-Shifted Hydrogen Bonds

A Molecular Cluster Study on Activated CH/π Interactions: Infrared Spectroscopy of Aromatic Molecule−Acetylene Clusters

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