π-Hole bonding in a new co-crystal hydrate of gallic acid and pyrazine: static and dynamic charge density analysis - CNRS - Centre national de la recherche scientifique Accéder directement au contenu
Article Dans Une Revue Acta Crystallographica Section B : Structural Science, Crystal Engineering and Materials [2014-...] Année : 2022

π-Hole bonding in a new co-crystal hydrate of gallic acid and pyrazine: static and dynamic charge density analysis

Résumé

A new cocrystal hydrate of gallic acid with pyrazine (4GA, Py, 4H 2 O; GA 4 PyW 4 ) was obtained and characterized by single crystal X-ray diffraction. In addition to structure determination, experimental charge density analysis was carried out in terms of Multipole Modelling (MP), X-ray wavefunction refinement (XWR) and maximum entropy method (MEM). As a part of XWR, the structural refinement via Hirshfeld atom refinement was carried out and resulted in O—H bond lengths close to values from neutron diffraction. A systematic comparison of molecular conformations and aromatic interactions in this new cocrystal hydrate was performed with other existing polymorphs of gallic acid. In GA 4 PyW 4 , the two symmetry-independent gallic acid molecules have a syn COOH orientation and form the common (COOH) 2 dimeric synthon. The carboxyl C atom displays the characteristics of π-holes with electropositive regions above and below the molecular plane and engages in acceptor–donor interactions with oxygen atoms of acidic O—H groups and phenol groups of neighbouring gallic acid molecules. The signature of the π-hole was identified from experimental charge density analysis, both in static density maps in MP and XWR as well as dynamic density in MEM, but it cannot be pinned down to a specific atom–atom interaction. This study presents the first comparison between an XWR and a MEM experimental electron-density determination.
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Dates et versions

hal-03633243 , version 1 (06-04-2022)

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Rumpa Pal, Christian Jelsch, Koichi Momma, Simon Grabowsky. π-Hole bonding in a new co-crystal hydrate of gallic acid and pyrazine: static and dynamic charge density analysis. Acta Crystallographica Section B : Structural Science, Crystal Engineering and Materials [2014-..], 2022, 78 (2), pp.231-246. ⟨10.1107/S2052520622001457⟩. ⟨hal-03633243⟩
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