ChemInform Abstract: Cyclophanes. Part 30. The Crystal Structure of (2.4)Paracyclophane at ‐95 °C

Jones, Peter G.; Pechlivanidis, Z.; Hopf, Henning

doi:10.1002/chin.198942048

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“…This separation increases for longer bridging groups, such as in [3,3]PCP. 40−44 Analysis of the single-crystal diffraction structures of [2,2]PCP, 40,45 [3,3]PCP, 42 and 4,4[PCP] 46 shows that the phenyl rings in dif ferent PCP molecules are not facially aligned with each other. The only facial π−π interactions between phenyl rings are therefore within the PCP molecules.…”

Section: Introductionmentioning

confidence: 99%

Systematic Investigation of π–π Interactions in Near-Edge X-ray Fine Structure (NEXAFS) Spectroscopy of Paracyclophanes

Perera

Urquhart

2017

J. Phys. Chem. A

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NEXAFS spectroscopy has potential for study of packing and order in organic materials but only if intermolecular effects are understood. This work studies how π-π interactions between adjacent unsaturated groups affect their NEXAFS spectra, with a broader goal of building a general understanding of the role of intermolecular effects in NEXAFS spectroscopy. These effects are examined using paracyclophane (PCP) molecules, in which the benzene-benzene separation distance is controlled by varying the length of the alkyl groups separating the benzene rings. NEXAFS spectroscopy and density functional theory (DFT) simulations are used to examine spectroscopic changes related to the strength of these π-π interactions. A characteristic red shift is observed as adjacent benzene rings get closer together. This shift is attributed to Coulombic and orbital interactions between the adjacent benzene rings, mediated through overlapping π/π* orbitals.

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