An experimental value for the B1u C–H stretch mode in benzene

Erlekam, Undine; Frankowski, Marcin; Meijer, Gerard; Helden, Gert von

doi:10.1063/1.2198828

Cited by 69 publications

(97 citation statements)

References 25 publications

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“…30,[32][33][34][35]38,41,42 When it was discovered 38,42,49 that the T-shape structure is further stabilized by a slight tilt of the monomers, it became clear that the (tilted) T-shaped structure is lower in energy than the parallel-displaced structure. The experimental evidence 17,[19][20][21][22][23] confirms this conclusion. Although the energy difference between the two structures is small, the parallel-displaced structure is not observed in experiments due to collisions with the carrier gases used.…”

Section: Introductionmentioning

confidence: 54%

Vibration–rotation-tunneling states of the benzene dimer: an ab initio study

Avoird

Podeszwa

Szalewicz

et al. 2010

Phys. Chem. Chem. Phys.

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152

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An improved intermolecular potential surface for the benzene dimer is constructed from interaction energies computed by symmetry-adapted perturbation theory, SAPT(DFT), with the inclusion of third-order contributions. Twelve characteristic points on the surface have been investigated also using the coupled-cluster method with single, double, and perturbative triple excitations, CCSD(T), and triple-zeta quality basis sets with midbond functions. The SAPT and CCSD(T) results are in close agreement and provide the best representation of these points to date. The potential was used in calculations of vibration-rotation-tunneling (VRT) levels of the dimer by a method appropriate for large amplitude intermolecular motions and tunneling between multiple equivalent minima in the potential. The resulting VRT levels were analyzed with the use of the permutation-inversion full cluster tunneling (FCT) group G 576 and a chain of subgroups that starts from the molecular symmetry group C s (M) of the rigid dimer at its equilibrium C s geometry and leads to G 576 if all possible intermolecular tunneling mechanisms are feasible. Further information was extracted from the calculated wave functions. It was found, in agreement with the experimental data, that for all of the 54 G 576 symmetry species (with different nuclear spin statistical weights) the lower VRT states have a tilted T-shape (TT) structure; states with the parallel-displaced structure are higher in energy than the ground state of A + 1 symmetry by at least 30 cm À1 . The dissociation energy D 0 equals 870 cm À1 , while the depth D e of the TT minimum in the potential is 975 cm À1 . Hindered rotation of the cap in the TT structure and tilt tunneling lead to level splittings on the order of 1 cm À1 . Also intermolecular vibrations with excitation energies starting at a few cm À1 were identified. A further small, but probably significant, level splitting was assigned to cap turnover, although in scans of the potential surface we could not find a plausible 'reaction path' for this process. Rotational constants were extracted from energy levels calculated for total angular momentum J = 0 and 1, and from expectation values of the inertia tensor. Although the end-over-end rotational constant B + C agrees well with the measured microwave spectra, there is disagreement with the measurements concerning the (a)symmetric rotor character of the benzene dimer. It is concluded from calculations for the 54 nuclear spin species that the microwave spectrum should show overlapping contributions from many different species. Another interesting conclusion regards the role of the quantum number K, for a prolate near-symmetric rotor the projection of the total angular momentum on the prolate axis. For the benzene dimer, K has a substantial effect on the energy levels associated with the intermolecular motions of the complex.

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Section: Introductionmentioning

confidence: 54%

Vibration–rotation-tunneling states of the benzene dimer: an ab initio study

Avoird

Podeszwa

Szalewicz

et al. 2010

Phys. Chem. Chem. Phys.

Self Cite

152

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“…These results, too, are in agreement with the experimentally observed red-shift of 3 cm −1 for these modes and also theoretical calculations of the vibrational spectra for the T-shape structure. [36][37][38] FIG. 2.…”

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confidence: 99%

Communication: Benzene dimer—The free energy landscape

Tummanapelli

Vasudevan

2013

The Journal of Chemical Physics

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Establishing the relative orientation of the two benzene molecules in the dimer has remained an enigmatic challenge. Consensus has narrowed the choice of structures to either a T-shape, that may be tilted, or a parallel displaced arrangement, but the relatively small energy differences makes identifying the global minimum difficult. Here we report an ab initio Car-Parrinello Molecular Dynamics based metadynamics computation of the free-energy landscape of the benzene dimer. Our calculations show that although competing structures may be isoenergetic, free energy always favors a tilted T-shape geometry at all temperatures where the bound benzene dimer exist.

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“…26 In the last year, Ramón and Grańa 27 have reported "blue shifting"hydrogen bond for the classical T-shaped configurations of the benzene dimer and benzene-naphthalene complexes using MP2 / 6-31+ + G ‫ءء‬ level. In contrast, a recent experimental study by Erlekam et al 24 revealed that the IR active modes of the C-H stretching vibrations of the benzene dimer are shifted up to 3 cm −1 to the "red" compared to the monomer. This experimental result raises challenging questions to theoreticians: ͑a͒ Does MP2 method fail to predict the red shift of vibrational frequency?…”

Section: Department Of Chemistry Interdisciplinary Center Formentioning

confidence: 50%

“…Erlekam et al 24,25 assigned T-shaped configuration for the benzene dimer based on their IR spectra. Therefore, we have considered different T-shaped configurations of the benzene dimer in this work in order to probe the reliability of theoretical approaches ͑Fig.…”

Section: Department Of Chemistry Interdisciplinary Center Formentioning

confidence: 99%

“…[17][18][19] Although it is of great challenge for experimentalists to characterize the structure of the gas phase benzene dimer due to rather flat potential energy surface, some experimental studies were reported in the literature. [20][21][22][23][24][25] Raman and microwave experimental studies suggested T-shaped configuration. 22,23 Significant efforts have been carried out by theoreticians in understanding the strength and directionality of -interactions of the benzene dimer using rigorous quantum chemical calculations.…”

Section: Department Of Chemistry Interdisciplinary Center Formentioning

confidence: 99%

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In the pursuit of small “red shift” of C–H stretching vibrational frequency of C–H⋯π interactions for benzene dimer: How to amend MP2 calculations to reproduce the experimental results

Dinadayalane

Leszczyński

2009

The Journal of Chemical Physics

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For the bent T-shaped benzene dimer, the vibrational frequencies at the MP2/aug-cc-pVDZ level with counterpoise correction reproduce experimental results of the small “red shifts” of C–H stretching, while those without counterpoise correction yield considerable “blue shift.” Counterpoise correction also affects the C–H bond distances of C–H⋯π interactions as well as intermoiety distances.

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An experimental value for the B1u C–H stretch mode in benzene

Cited by 69 publications

References 25 publications

Vibration–rotation-tunneling states of the benzene dimer: an ab initio study

Vibration–rotation-tunneling states of the benzene dimer: an ab initio study

Communication: Benzene dimer—The free energy landscape

In the pursuit of small “red shift” of C–H stretching vibrational frequency of C–H⋯π interactions for benzene dimer: How to amend MP2 calculations to reproduce the experimental results

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