Hydrogen bonded and stacked dimers have very close interaction energies in the crystals of the simplest coumarin derivatives according to the data of the crystal structure analysis based on the comparison of pairwise interaction energies.
The polymorphic study of 3‐(3‐phenyl‐1H‐1,2,4‐triazol‐5‐yl)‐2H‐1‐benzopyran‐2‐one, C17H11N3O2, was performed due to its potential biological activity and revealed three polymorphic modifications in the triclinic space group P, the monoclinic space group P21 and the orthorhombic space group Pbca. These polymorphs have a one‐column layered type of crystal organization. The strongest interactions between the molecules of the studied structures is stacking between π‐systems, while N—H…N and C—H…O hydrogen bonds link stacked columns forming layers as a secondary basic structural motif. C—H…π hydrogen bonds were observed between neighbouring layers and their role is the least significant in the formation of the crystal structure. Packing differences between the polymorphic modifications are minor and can be identified only using an analysis based on a comparison of the pairwise interaction energies.
During a comprehensive study of a series of 2‐(N‐arylimino)coumarin‐3‐carboxamides with the aryl group substituted in the ortho‐position by either a halogen atom, a methyl group or a methoxy group, the existence of three groups of isotypic crystal structures has been revealed. The similarity of crystal structures belonging to the same groups was confirmed by the analysis based on the comparison of pairwise interactions energies obtained from quantum chemical calculations. Group I includes unsubstituted, methyl‐substituted and polymorphic modification 1 of fluoro‐substituted 2‐(N‐arylimino)coumarin‐3‐carboxamide. Structures of polymorphic modification 2 of fluoro‐substituted derivative, chloro‐substituted and polymorphic modification 1 of bromo‐substituted 2‐(N‐arylimino)coumarin‐3‐carboxamide may represent group II. Group III contains structures of polymorphic modification 2 of bromo‐substituted derivative, iodine‐ and methoxy‐substituted 2‐(N‐arylimino)coumarin‐3‐carboxamides. Structures of the same type group have extremely close parameters of the unit cell as well as those of molecular and crystal structures. But they are not identical. Polymorphic modifications of fluoro‐ and bromo‐substituted 2‐(N‐arylimino)coumarin‐3‐carboxamides belong to different crystal types mainly due to different arrangement of basic structural motifs separated out using quantum chemical calculations.
C21H23N5O6, monoclinic, P21/c (no. 14), a = 8.4861(4) Å, b = 16.3198(8) Å, c = 15.8521(8) Å, β = 97.605(5)°, V = 2176.1(2) Å3, Z = 4, R
gt(F) = 0.0463, wR
ref = 0.1201, T = 293(2) K.
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