The molecular structure of p-diethynylbenzene has been determined by gas-phase electron diffraction and ab initio MO calculations at the HF/6-31G* and MP2/6-31G*(fc) levels. The two ethynyl groups undergo large-amplitude bending motions, making the equilibrium D2h model inadequate to describe the average structure from electron diffraction. Based on spectroscopic information on low-frequency modes, the electron diffraction data were approximated by a model consisting of a mixture of rigid conformers, differing only in the extent of the symmetric out-of-plane bending of the substituents. This gave the following geometrical parameters: <Cortho−Cipso−Cortho = 119.2 ± 0.2°, <rg(C-C)> = 1.402 ± 0.003 Å, rg(Cring−Csp) = 1.431 ± 0.003 Å, and rg(C≡C) = 1.211 ± 0.003 Å. The computed re values (MP2) are 119.2°, 1.401 Å, 1.430 Å , and 1.223 Å, respectively, with the Cipso−Cortho bond 0.016 Å longer than the central C−C bond. The HF/6-31G* geometries of ethynylbenzene and p-diethynylbenzene indicate that the interaction of the ethynyl group with the ring is not affected by the presence of another ethynyl group in the para position. Comparison with solid-state results shows no appreciable effect of crystal environment on the ring deformation in these molecules.

Molecular structure and large-amplitude motion of p-diethynylbenzene from gas-phase electron diffraction and theoretical calculations / Domenicano, A.; Arcadi, A.; Ramondo, F.; Campanelli, Anna Rita; Portalone, Gustavo; Schultz, G.; Hargittai, I.. - In: THE JOURNAL OF PHYSICAL CHEMISTRY. - ISSN 0022-3654. - STAMPA. - 100:(1996), pp. 14625-14629. [10.1021/jp952328y]

Molecular structure and large-amplitude motion of p-diethynylbenzene from gas-phase electron diffraction and theoretical calculations

F. Ramondo;CAMPANELLI, Anna Rita;PORTALONE, Gustavo;
1996

Abstract

The molecular structure of p-diethynylbenzene has been determined by gas-phase electron diffraction and ab initio MO calculations at the HF/6-31G* and MP2/6-31G*(fc) levels. The two ethynyl groups undergo large-amplitude bending motions, making the equilibrium D2h model inadequate to describe the average structure from electron diffraction. Based on spectroscopic information on low-frequency modes, the electron diffraction data were approximated by a model consisting of a mixture of rigid conformers, differing only in the extent of the symmetric out-of-plane bending of the substituents. This gave the following geometrical parameters: = 1.402 ± 0.003 Å, rg(Cring−Csp) = 1.431 ± 0.003 Å, and rg(C≡C) = 1.211 ± 0.003 Å. The computed re values (MP2) are 119.2°, 1.401 Å, 1.430 Å , and 1.223 Å, respectively, with the Cipso−Cortho bond 0.016 Å longer than the central C−C bond. The HF/6-31G* geometries of ethynylbenzene and p-diethynylbenzene indicate that the interaction of the ethynyl group with the ring is not affected by the presence of another ethynyl group in the para position. Comparison with solid-state results shows no appreciable effect of crystal environment on the ring deformation in these molecules.
1996
Gas-phase electron diffraction; Large-amplitude motion; p-diethynylbenzene; MO calculations
01 Pubblicazione su rivista::01a Articolo in rivista
Molecular structure and large-amplitude motion of p-diethynylbenzene from gas-phase electron diffraction and theoretical calculations / Domenicano, A.; Arcadi, A.; Ramondo, F.; Campanelli, Anna Rita; Portalone, Gustavo; Schultz, G.; Hargittai, I.. - In: THE JOURNAL OF PHYSICAL CHEMISTRY. - ISSN 0022-3654. - STAMPA. - 100:(1996), pp. 14625-14629. [10.1021/jp952328y]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/466818
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