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. 2017 Mar 27;4(Pt 3):243-250.
doi: 10.1107/S2052252517004043. eCollection 2017 May 1.

Mechanochemical synthesis of N-salicylidene-aniline: thermosalient effect of polymorphic crystals

Sudhir Mittapalli  1 , D Sravanakumar Perumalla  2 , Ashwini Nangia  1   3
Affiliations

Mechanochemical synthesis of N-salicylidene-aniline: thermosalient effect of polymorphic crystals

Sudhir Mittapalli et al. IUCrJ. .

Abstract

Polymorphs of the dichloro derivative of N-salicylideneaniline exhibit mechanical responses such as jumping (Forms I and III) and exploding (Form II) in its three polymorphs. The molecules are connected via the amide N-H⋯O dimer synthon and C-Cl⋯O halogen bond in the three crystal structures. A fourth high-temperature Form IV was confirmed by variable-temperature single-crystal X-ray diffraction at 180°C. The behaviour of jumping exhibited by the polymorphic crystals of Forms I and III is due to the layered sheet morphology and the transmission of thermal stress in a single direction, compared with the corrugated sheet structure of Form II such that heat dissipation is more isotropic causing blasting. The role of weak C-Cl⋯O interactions in the thermal response of molecular crystals is discussed.

Keywords: crystal design; crystal engineering; halogen bonding; hydrogen bonding; intermolecular interactions; materials science; mechanochemistry; polymorphism.

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Figures

Figure 1
Figure 1
Schematic representation of the preparation conditions and transformations for polymorphs of compound A.
Figure 2
Figure 2
(a) Heating of Form I crystal of compound A, and the sudden disappearance of crystal from the hot stage. (b) Blasting of Form II crystals on heating.
Figure 3
Figure 3
(a) Crystal morphology of Compound A Form I and arrangement of molecules in different planes. (b) Amide dimers extend through C—Cl⋯O and N—H⋯O interactions (Form I). (c) Figure showing the layered arrangement of molecules in Form I crystal structure.
Figure 4
Figure 4
(a) Figure showing amide–amide dimers extended by C—Cl⋯O and N—H⋯O interactions in Form II structure. (b) Symmetry-independent molecules (indicated in blue and green colors) were arranged in a corrugated wave-like manner in Form II.
Figure 5
Figure 5
(a) Amide dimers extended by C—Cl⋯O and N—H⋯O interactions in Form III. (b) Morphology of Form III crystal and packing of molecules in different planes. (c) Layered arrangement of symmetry independent molecules (blue and green color).
Figure 6
Figure 6
(a) Amide dimers extended by C—Cl⋯O and N—H⋯O interactions. (b) Layered arrangement of molecules (Form IV).
Figure 7
Figure 7
Percentage contribution of hydrogen-/halogen-bonding interactions in Compound A polymorphs (I–IV).
See this image and copyright information in PMC

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