The mechanism of bending in co-crystals of caffeine and 4-chloro-3-nitrobenzoic acid.
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ABSTRACT:
SUBMITTER: Thompson AJ
PROVIDER: S-EPMC8528856 | biostudies-literature | 2021 Oct
REPOSITORIES: biostudies-literature
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The mechanism of bending in co-crystals of caffeine and 4-chloro-3-nitrobenzoic acid.
Thompson Amy J AJ Price Jason R JR McMurtrie John C JC Clegg Jack K JK
Nature communications 20211020 1
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Project description:The structures of the four isomeric compounds of 6-methyl-quinoline with chloro- and nitro-substituted benzoic acids, C7H4ClNO4·C10H9N, namely, 2-chloro-4-nitro-benzoic acid-6-methyl-quinoline (1/1), (I), 2-chloro-5-nitro-benzoic acid-6-methyl-quinoline (1/1), (II), 3-chloro-2-nitro-benzoic acid-6-methyl-quinoline (1/1), (III), and 4-chloro-2-nitro-benzoic acid-6-methyl-quinoline (1/1), (IV), have been determined at 185-190 K. In each compound, the acid and base mol-ecules are linked by a short hydrogen bond between a carboxyl O atom and an N atom of the base. The O⋯N distances are 2.5452 (12), 2.6569 (13), 2.5640 (17) and 2.514 (2) Å, respectively, for compounds (I)-(IV). In the hydrogen-bonded acid-base units of (I), (III) and (IV), the H atoms are each disordered over two positions with O site:N site occupancies of 0.65 (3):0.35 (3), 0.59 (4):0.41 (4) and 0.48 (5):0.52 (5), respectively, for (I), (III) and (IV). The H atom in the hydrogen-bonded unit of (II) is located at the O-atom site. In all of the crystals of (I)-(IV), π-π inter-actions between the quinoline ring system and the benzene ring of the acid mol-ecule are observed. In addition, a π-π inter-action between the benzene rings of adjacent acid mol-ecules and a C-H⋯O hydrogen bond are observed in the crystal of (I), and C-H⋯O hydrogen bonds and O⋯Cl contacts occur in the crystals of (III) and (IV). These inter-molecular inter-actions connect the acid and base mol-ecules, forming a layer structure parallel to the bc plane in (I), a column along the a-axis direction in (II), a layer parallel to the ab plane in (III) and a three-dimensional network in (IV). Hirshfeld surfaces for the title compounds mapped over d norm and shape index were generated to visualize the weak inter-molecular inter-actions.
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