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Aggregation in isomeric imides: analysis of the weak interactions in six N-(benzoyl)-N-(2-pyridyl)benzamides


Crystal structures of 4-chloro-N-(4-chlorobenzoyl)-N-(2-pyridyl)benzamide (I) Clpod, 3-chloro-N-(3-chlorobenzoyl)-N-(2-pyridyl)benzamide (II) Clmod and 2-chloro-N-(2-chlorobenzoyl)-N-(2-pyridyl)benzamide (III) Clood together with three methylated analogues, Mpod, Mmod and Mood, are presented herein. The Clxod acyclic imides are produced from reacting the 4-/3-/2-chlorobenzoyl chlorides (Clx) with 2-aminopyridine (o), respectively, together with their benzamide analogues Clxo; the Mxod/Mxo triad are produced similarly and in good yield. The five Clxod, Mpod and Mmod structures adopt the open transoid conformations as expected, but Mood crystallises with cisoid oriented benzoyl groups, and this conformation was unexpected, though not unknown. Halogen bonding contacts and weak hydrogen bonding C-H···N/O/π contacts are noted in the structures lacking strong hydrogen bonding donor atoms/groups but possessing a variety of strong and weaker acceptor atoms/groups. For Clxod, contact studies show that both hydrogen and carbon account for a high percentage of elements (70–75%) on the molecular surface and being the most abundant have C···H forming 26–30% of the contacts. Contact enrichment ratios are an indicator of the likelihood of chemical species to form intermolecular interactions with themselves and other species. The C-H···N and C-H···O are the most enriched (with EHN > 2.15), indicating that these weak hydrogen bonds are the driving force in the Clxod crystal packing formation. For Mxod, the C···H contact type at 40–52% is the most abundant contact type and C-H···O and C-H···N weak hydrogen bonds dominate with enrichment values in the 1.48–1.78 range. In Mxod, N/O···N/O contacts are effectively absent, except for Mpod (0.2%, N···N contacts) and both H···H and C···C non-polar contacts are moderately impoverished while the C···H interactions are slightly enriched (E = 1.1–1.21).

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JFG and MF thank Dublin City University for grants in aid of undergraduate research. PM thanks the T3 (PRTLI-4) program for a postgraduate studentship. This research was part-funded by the Programme for Research in Third Level Institutions (PRTLI) Cycle 4 (Ireland) and co-funded through the European Regional Development Fund (ERDF), part of the European Union Structural Funds Programme (ESF) 2007−2013. JFG and CJ thank the Region Lorraine for a FEDER Chercheur d’Avenir grant (2015–2018).

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Correspondence to John F. Gallagher.

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Crystallographic data for the six Clxod and Mxod isomeric crystal structures have been deposited with the Cambridge Crystallographic Data Centre, CCDC no. 1564570 to 1564575. The CIF data may be downloaded from the CCDC website or obtained free of charge from The Director, CCDC, 12 Union road, Cambridge, CB2 1EZ, U.K. (fax: +44–1223-336,033; e-mail: The data are also available as CIF files from the corresponding author Dr. John F. Gallagher. (DOCX 1522 kb)


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Mocilac, P., Farrell, M., Lough, A.J. et al. Aggregation in isomeric imides: analysis of the weak interactions in six N-(benzoyl)-N-(2-pyridyl)benzamides. Struct Chem 29, 1153–1164 (2018).

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  • Chlorine
  • Contact enrichment ratio
  • Crystal structure
  • Imide
  • Methyl
  • Weak interactions