Different substituent effects on the supramolecular arrays in some (E)-halo- and nitro-benzaldehyde oximes: confirmation of attractive π(C=N)···π(phenyl) interactions

Ligia R. Gomes, John N. Low, Tanja van Mourik, Herbert Früchtl, Marcus V.n. De Souza, Cristiane F. Da Costa, James L. Wardell

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Abstract

The crystal structures and Hirshfeld surface analyses are reported for four aldoximes, (E)-X–C6H4CH=N–OH [X = 3-Cl (1), 4-F (2), 2-O2N (3) and 4-O2N (4)]. The strong classical O–H · · · N hydrogen bonds involving the oxime group generate C(3) chains in compound 1, in contrast to the R22(6) dimers formed in compounds 2–4; such arrangements have been shown to be the most frequently found for oximes other than salicylaldoximes (2-hydroxybenzaldehyde oximes). In general, weaker intermolecular interactions involving the X substituents, as well as C–H · · · O and π · · · π interactions have significant effects on the supramolecular arrays generated in the aggegation. A further important interaction in compound 1, and to a lesser extent in compound 4, is a π(C=N) · · · π(phenyl) molecular stacking. A data base search has indicated that short Cg(C=N) · · · Cg(phenyl) distances, <3.3 Å (Cg = centre of gravity), have been found in various compounds, including other oximes. A theoretical study was carried out starting from the crystal structure data of compound 1, with optimisation at the BLYP-D3/def2-DZVP level, as well as at the higher PBE0/ma-def2-TZVP level. Breakdown of the interaction energy into separate contributions was achieved using SAPT (using the jun-cc-pvdz basis set). Overall, the calculations indicate that the π(C=N) ·· · π(phenyl) interaction is attractive, with a magnitude of 14–18 kJ mol−1.
Original languageEnglish
Pages (from-to)319-334
JournalZeitschrift für Naturforschung B - A Journal of Chemical Sciences
Volume74
Issue number4
Early online date2 Apr 2019
DOIs
Publication statusPublished - 24 Apr 2019

Keywords

  • π(C=N)···π(phenyl) interactions
  • Aldoximes
  • Crystal structures
  • Quantum chemical calculations

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