Molecular structure and ring distortions of p-diiso-cyanobenzene in the gaseous phase and in the crystal

Marcello Colapietro, Aldo Domenicano, Gustavo Portalone, Ines Torrini, István Hargittai, György Schultz

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The molecular structure of p-diisocyanobenzene has been accurately determined in the gaseous phase (by electron diffraction) and in the crystal (by X-ray crystallography). The X-ray diffraction results have been corrected for the effects of solid state thermal motions and asphericities in valence electrons, so as to allow a comparison with gas-phase results. In both phases the benzene ring is found to deviate appreciably from D6 h symmetry: the most pronounced distortion is an increase to ∼ 122° of the internal angle at the ipso carbon, α. The geometry of the substituent indicates that the dipolar form {A figure is presented} contributes to the electronic structure substantially more than does -N=C. The following structural changes occur on going from the free molecule to the crystal molecule: (i) an increase of α from 121.7 ± 0.2° to 122.2(3)°, (ii) an increase of {A figure is presented} from 1.388 ± 0.003 A to 1.396(3) A, and (iii) a decrease of {A figure is presented} from 1.176 ± 0.002 A to 1.166(4) A. The consistent pattern of these changes indicates that the contribution of the dipolar form of the substituent is larger in the crystalline than in the gaseous state. The crystals are composed of stacks of parallel molecules arranged in such a way that each benzene ring is sandwiched between two antiparallel isocyano groups, at a distance of 3.45 A. This arrangement appears to stabilize the dipolar form of the substituent, which has a π* orbital properly oriented to favour a charge-transfer interaction with a μ orbital of the neighbouring benzene ring.

Original languageEnglish
Pages (from-to)19-32
Number of pages14
JournalJournal of Molecular Structure
Issue number1-2
Publication statusPublished - Nov 1984


ASJC Scopus subject areas

  • Analytical Chemistry
  • Spectroscopy
  • Organic Chemistry
  • Inorganic Chemistry

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