Cooperative Effect of CH···O Bonds in Models for Biological Systems

Giambiagi, Mario; Neto, Marçal Oliveira de; Neder, Amarílis V. F.

doi:10.1007/s10910-005-6905-3

Cited by 4 publications

(4 citation statements)

References 41 publications

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“…While XH bonds exhibit the usual trend, elongating when entering a hydrogen bond, the MH bonds behave in the opposite sense, becoming shorter; this feature has been found by other authors, although not so generally, 28,32 and hinted at in the present framework. 49 The trend of the blue-shift points at the same direction, but there is not a clear correlation as that between the indices and the energies. Figure 1 represents, on one hand I XHM + I XHH and on the other hand I HH M + I XH M , as well as I XHH M , all of them as functions of the bond energy.…”

Section: Resultsmentioning

confidence: 92%

Bond indices in dihydrogen bonds

Giambiagi¹,

Bultinck²

2008

J. Braz. Chem. Soc.

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Os índices de ligação de três centros levam a uma descrição nova da ligação di-hidrogênio XH...H M como sendo uma superposição de uma ponte de hidrogênio usual XHH , mais uma ponte de hidrogênio forte HH M. O índice de ligação de quatro centros é negativo e o seu valor é intermediário entre os anteriores. Three-center bond indices lead to a new description for dihydrogen bonds XH…H M: it may be mainly described as a superposition of a usual hydrogen bond XHH and a strong hydrogen bond HH M. The four-center bond index is negative and its value is intermediate between the preceding ones.

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Section: Resultsmentioning

confidence: 92%

Bond indices in dihydrogen bonds

Giambiagi¹,

Bultinck²

2008

J. Braz. Chem. Soc.

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“…10 The cooperative effects of the CsH • • • O interaction on adjacent OsH • • • O HBs were investigated theoretically for the homodimers of acetic acid and acrylic acid and the mixed dimer between acetic acid and acetamide. 15 However, to our knowledge, direct spectroscopic evidence of cooperative stabilization in such systems has not been reported to date.…”

Section: Introductionmentioning

confidence: 87%

“…The effect was also investigated by quantum chemistry methods for complexes of CO 2 with formaldehyde, methyl acetate, acetic acid, and so on . The cooperative effects of the CH···O interaction on adjacent OH···O HBs were investigated theoretically for the homodimers of acetic acid and acrylic acid and the mixed dimer between acetic acid and acetamide . However, to our knowledge, direct spectroscopic evidence of cooperative stabilization in such systems has not been reported to date.…”

Section: Introductionmentioning

confidence: 99%

Cooperative Strengthening of an Intramolecular O—H···O Hydrogen Bond by a Weak C—H···O Counterpart: Matrix-Isolation Infrared Spectroscopy and Quantum Chemical Studies on 3-Methyl-1,2-cyclohexanedione

et al. 2009

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Matrix-isolation infrared spectra of 1,2-cyclohexanedione (CD) and 3-methyl-1,2-cyclohexanedione (3-MeCD) were measured in a nitrogen matrix at 8 K. The spectral features reveal that, in the matrix environment, both molecules exist exclusively in the monohydroxy tautomeric form, which is stabilized by an intramolecular O-H...O=C hydrogen bond (HB). The nu(O-H) band of the enol tautomer of 3-MeCD appears at a relatively lower frequency and displays a somewhat broader bandwidth compared to that of CD, and these spectral differences between the two molecules are interpreted as being due to the formation of an interconnected C-H...O HB, where the enolic oxygen is the HB acceptor and one of the C-H covalent bonds of the methyl group is the HB donor. Electronic structure calculations at the B3LYP/6-311++G**, MP2/6-311++G**, and MP2/cc-pVTZ levels predict that this tautomer (enol-2) is approximately 3.5 kcal/mol more stable than a second enolic form (enol-1) where such interconnected H-bonding is absent. Theoretical analysis with a series of molecules having similar functional groups reveals that part of the excess stability (approximately 1 kcal/mol) of enol-2 originates from a cooperative interaction between the interconnected C-H...O and O-H...O HBs. In the IR spectrum, a weak band at 3007 cm(-1) is assigned to nu(C-H) of the methyl C-H bond involved in the H-bonded network. The spectra predicted by both harmonic and anharmonic calculations reveal that this transition is largely blue-shifted compared to the fundamentals of the other two methyl C-H stretching frequencies that are not involved in H-bonding. The conclusions are corroborated further by natural bond orbital (NBO) analysis.

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“…For several decades, the formation of hydrogen halide aggregates has been explored, driven by the interest in the varied architectures and the nature of the interactions in these aggregates, as well as the resulting properties manifested by molecular cooperativity [1][2][3][4][5][6]. Among the interactions established between clusters, multicentric interactions (for example, the tricentric bond with three nuclear attractors and two electrons) [7] are usually responsible for the stabilization of a set of atoms in a molecule, and this can be extended to clusters of molecules, and hydrogen bonds, which are special dipole-dipole type interactions involving charge transfer. Systems comprising three nuclear attractors and four electrons may also be formed.…”

Section: Introductionmentioning

confidence: 99%

Non-conservation of activation energy barriers in the same chemical process: a cooperative (effect) proton transfer on (HF)n molecular aggregates

2020

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The formation of (HF) n aggregates with n = 2, 3, 4, 5 and 6 and concerted proton transfer processes in these aggregates were systematically analyzed. It was verified that, by a cooperative effect, the barrier associated with the proton transfer process decreases for aggregates with a larger number of molecules, indicating that the activation energy for proton transfer depends on the molecularity of the process. Natural bond orbital and quantum theory of atoms in molecules were used to characterize the strength of the hydrogen bonds established in the aggregates, which verified a general increase in the delocalization energy as a function of increasing aggregate size. A deformed Eyring (d-Eyring) equation was used to calculate the proton transfer rate constants, where the d-Eyring equation adequately described the proton transfer kinetics. Analysis of the rate constants showed that proton transfer became faster as the cluster size increased. Arrhenius and d-Arrhenius plots showed a decrease in the dependence of the rate constants on temperature, particularly for the tetramer, pentamer, and hexamer. The d-Arrhenius plots, for which the d parameter was included in the Eyring equation, suggest non-Arrhenius behavior for proton transfer in the HF aggregates at low temperatures.

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Cooperative Effect of CH···O Bonds in Models for Biological Systems

Cited by 4 publications

References 41 publications

Bond indices in dihydrogen bonds

Bond indices in dihydrogen bonds

Cooperative Strengthening of an Intramolecular O—H···O Hydrogen Bond by a Weak C—H···O Counterpart: Matrix-Isolation Infrared Spectroscopy and Quantum Chemical Studies on 3-Methyl-1,2-cyclohexanedione

Non-conservation of activation energy barriers in the same chemical process: a cooperative (effect) proton transfer on (HF)n molecular aggregates

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