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Invariom-model refinement and Hirshfeld surface analysis of well-ordered solvent-free dibenzo-21-crown-7

Wiedemann, Dennis; Kohl, Julia

Crown ethers and their supra­molecular derivatives are well-known chelators and scavengers for a variety of cations, most notably heavier alkali and alkaline-earth ions. Although they are widely used in synthetic chemistry, available crystal structures of uncoordinated and solvent-free crown ethers regularly suffer from disorder. In this study, we present the X-ray crystal structure analysis of well-ordered solvent-free crystals of dibenzo-21-crown-7 (systematic name: dibenzo[b,k]-1,4,7,10,13,16,19-hepta­oxa­cyclo­heneicosa-2,11-diene, C22H28O7). Because of the quality of the crystal and diffraction data, we have chosen invarioms, in addition to standard independent spherical atoms, for modelling and briefly discuss the different refinement results. The electrostatic potential, which is directly deducible from the invariom model, and the Hirshfeld surface are analysed and complemented with inter­action-energy computations to characterize inter­molecular contacts. The boat-like mol­ecules stack along the a axis and are arranged as dimers of chains, which assemble as rows to form a three-dimensional structure. Dispersive C—H...H—C and C—H...π inter­actions dominate, but nonclassical hydrogen bonds are present and reflect the overall rather weak electrostatic influence. A fingerprint plot of the Hirshfeld surface summarizes and visualizes the inter­molecular inter­actions. The insight gained into the crystal structure of dibenzo-21-crown-7 not only demonstrates the power of invariom refinement, Hirshfeld surface analysis and inter­action-energy computation, but also hints at favourable conditions for crystallizing solvent-free crown ethers.
Published in: Acta crystallographica Section C : Structural Chemistry, 10.1107/S2053229617011160, International Union of Crystallography (IUCr) ; Wiley-Blackwell