Molecular structure of p-diisocyanobenzene from gas-phase electron diffraction and theoretical calculations and effects of intermolecular interactions in the crystal on the benzene ring geometry

Anna Rita Campanelli, Aldo Domenicano, Fabio Ramondo, I. Hargittai

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3 Citations (Scopus)

Abstract

In this study, the molecular structure of p-diisocyanobenzene has been determined by gas-phase electron diffraction and quantum chemical calculations. The electron diffraction intensities from a previous study by Colapietro et al. (J Mol Struct 125:19-32, 1984) have been reanalyzed using geometrical constraints and initial values of vibrational amplitudes from computations. The equilibrium structure of the molecule has D 2h symmetry, whereas the average geometry in the gaseous phase is best described by a non-planar model of C 2v symmetry. The lowering of symmetry is due to large-amplitude motion of the substituents out of the plane of the benzene ring. The non-planar model has an internal ring angle at the ipso position, aC2-C1-C6 = 120.6 ± 0.2°, about 1° smaller than that from the previous study, but consistent with the quantum chemical calculations. The mean length of the ring C-C bonds and the length of the triple bond are accurately determined as (r g(C-C)i = 1.398 ± 0.003 Å and r g(N:C) = 1.177 ± 0.002 Å , respectively. Comparison with the gaseous isoelectronic molecules p-diethynylbenzene and p-dicyanobenzene shows that the differences in the mean lengths of the ring C-C bonds and in the lengths of the triple bonds determined by electron diffraction are equal or closely similar to the corresponding differences from quantum chemical calculations. The present experimental value of the ipso angle in free p-diisocyanobenzene is slightly, but significantly smaller than that obtained by X-ray crystallography. The difference is confirmed by computational modeling of the crystal structure and appears to be due to -N:C⋯H-C intermolecular interactions in the crystal.

Original languageEnglish
Pages (from-to)287-295
Number of pages9
JournalStructural Chemistry
Volume23
Issue number1
DOIs
Publication statusPublished - Feb 2012

Fingerprint

Benzene
Electron diffraction
Molecular structure
molecular structure
electron diffraction
Gases
benzene
vapor phases
Crystals
Geometry
rings
geometry
crystals
symmetry
interactions
Molecules
X ray crystallography
crystallography
molecules
Crystal structure

Keywords

  • Equilibrium C-C bond distances
  • Gas-phase electron diffraction
  • Gas-solid structural differences
  • MO calculations
  • P-Dicyanobenzene
  • P-Diethynylbenzene
  • P-Diisocyanobenzene
  • P-Diisocyanobenzene pentamer

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry

Cite this

@article{583fc6e9afa349cdbe6b1646936e3663,
title = "Molecular structure of p-diisocyanobenzene from gas-phase electron diffraction and theoretical calculations and effects of intermolecular interactions in the crystal on the benzene ring geometry",
abstract = "In this study, the molecular structure of p-diisocyanobenzene has been determined by gas-phase electron diffraction and quantum chemical calculations. The electron diffraction intensities from a previous study by Colapietro et al. (J Mol Struct 125:19-32, 1984) have been reanalyzed using geometrical constraints and initial values of vibrational amplitudes from computations. The equilibrium structure of the molecule has D 2h symmetry, whereas the average geometry in the gaseous phase is best described by a non-planar model of C 2v symmetry. The lowering of symmetry is due to large-amplitude motion of the substituents out of the plane of the benzene ring. The non-planar model has an internal ring angle at the ipso position, aC2-C1-C6 = 120.6 ± 0.2°, about 1° smaller than that from the previous study, but consistent with the quantum chemical calculations. The mean length of the ring C-C bonds and the length of the triple bond are accurately determined as (r g(C-C)i = 1.398 ± 0.003 {\AA} and r g(N:C) = 1.177 ± 0.002 {\AA} , respectively. Comparison with the gaseous isoelectronic molecules p-diethynylbenzene and p-dicyanobenzene shows that the differences in the mean lengths of the ring C-C bonds and in the lengths of the triple bonds determined by electron diffraction are equal or closely similar to the corresponding differences from quantum chemical calculations. The present experimental value of the ipso angle in free p-diisocyanobenzene is slightly, but significantly smaller than that obtained by X-ray crystallography. The difference is confirmed by computational modeling of the crystal structure and appears to be due to -N:C⋯H-C intermolecular interactions in the crystal.",
keywords = "Equilibrium C-C bond distances, Gas-phase electron diffraction, Gas-solid structural differences, MO calculations, P-Dicyanobenzene, P-Diethynylbenzene, P-Diisocyanobenzene, P-Diisocyanobenzene pentamer",
author = "Campanelli, {Anna Rita} and Aldo Domenicano and Fabio Ramondo and I. Hargittai",
year = "2012",
month = "2",
doi = "10.1007/s11224-011-9889-6",
language = "English",
volume = "23",
pages = "287--295",
journal = "Structural Chemistry",
issn = "1040-0400",
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T1 - Molecular structure of p-diisocyanobenzene from gas-phase electron diffraction and theoretical calculations and effects of intermolecular interactions in the crystal on the benzene ring geometry

AU - Campanelli, Anna Rita

AU - Domenicano, Aldo

AU - Ramondo, Fabio

AU - Hargittai, I.

PY - 2012/2

Y1 - 2012/2

N2 - In this study, the molecular structure of p-diisocyanobenzene has been determined by gas-phase electron diffraction and quantum chemical calculations. The electron diffraction intensities from a previous study by Colapietro et al. (J Mol Struct 125:19-32, 1984) have been reanalyzed using geometrical constraints and initial values of vibrational amplitudes from computations. The equilibrium structure of the molecule has D 2h symmetry, whereas the average geometry in the gaseous phase is best described by a non-planar model of C 2v symmetry. The lowering of symmetry is due to large-amplitude motion of the substituents out of the plane of the benzene ring. The non-planar model has an internal ring angle at the ipso position, aC2-C1-C6 = 120.6 ± 0.2°, about 1° smaller than that from the previous study, but consistent with the quantum chemical calculations. The mean length of the ring C-C bonds and the length of the triple bond are accurately determined as (r g(C-C)i = 1.398 ± 0.003 Å and r g(N:C) = 1.177 ± 0.002 Å , respectively. Comparison with the gaseous isoelectronic molecules p-diethynylbenzene and p-dicyanobenzene shows that the differences in the mean lengths of the ring C-C bonds and in the lengths of the triple bonds determined by electron diffraction are equal or closely similar to the corresponding differences from quantum chemical calculations. The present experimental value of the ipso angle in free p-diisocyanobenzene is slightly, but significantly smaller than that obtained by X-ray crystallography. The difference is confirmed by computational modeling of the crystal structure and appears to be due to -N:C⋯H-C intermolecular interactions in the crystal.

AB - In this study, the molecular structure of p-diisocyanobenzene has been determined by gas-phase electron diffraction and quantum chemical calculations. The electron diffraction intensities from a previous study by Colapietro et al. (J Mol Struct 125:19-32, 1984) have been reanalyzed using geometrical constraints and initial values of vibrational amplitudes from computations. The equilibrium structure of the molecule has D 2h symmetry, whereas the average geometry in the gaseous phase is best described by a non-planar model of C 2v symmetry. The lowering of symmetry is due to large-amplitude motion of the substituents out of the plane of the benzene ring. The non-planar model has an internal ring angle at the ipso position, aC2-C1-C6 = 120.6 ± 0.2°, about 1° smaller than that from the previous study, but consistent with the quantum chemical calculations. The mean length of the ring C-C bonds and the length of the triple bond are accurately determined as (r g(C-C)i = 1.398 ± 0.003 Å and r g(N:C) = 1.177 ± 0.002 Å , respectively. Comparison with the gaseous isoelectronic molecules p-diethynylbenzene and p-dicyanobenzene shows that the differences in the mean lengths of the ring C-C bonds and in the lengths of the triple bonds determined by electron diffraction are equal or closely similar to the corresponding differences from quantum chemical calculations. The present experimental value of the ipso angle in free p-diisocyanobenzene is slightly, but significantly smaller than that obtained by X-ray crystallography. The difference is confirmed by computational modeling of the crystal structure and appears to be due to -N:C⋯H-C intermolecular interactions in the crystal.

KW - Equilibrium C-C bond distances

KW - Gas-phase electron diffraction

KW - Gas-solid structural differences

KW - MO calculations

KW - P-Dicyanobenzene

KW - P-Diethynylbenzene

KW - P-Diisocyanobenzene

KW - P-Diisocyanobenzene pentamer

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U2 - 10.1007/s11224-011-9889-6

DO - 10.1007/s11224-011-9889-6

M3 - Article

VL - 23

SP - 287

EP - 295

JO - Structural Chemistry

JF - Structural Chemistry

SN - 1040-0400

IS - 1

ER -