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C19H14FN5O, monoclinic, P21/c (no. 14), a = 7.2944(3) Å, b = 12.2032(5) Å, c = 18.1070(7) Å, β = 95.807(4)°, V = 1603.52(11) Å3, Z = 4, Rgt(F) = 0.0451, wRref = 0.1217, T = 100(2) K. [ABSTRACT FROM AUTHOR]

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, Rgt(F) = 0.0463, wRref = 0.1201, T = 293(2) K. [ABSTRACT FROM AUTHOR]

The crystal structures of the carboxamide and thiocarboxamide derivatives of coumarin and 2-iminocoumarin have been studied thoroughly by comparing their pairwise interaction energies calculated by quantum chemistry methods. The crystals of coumarin-3-carboxamide and 2-iminocoumarin-3-carboxamide proved to be isostructural despite the predictable different properties of the carbonyl and imino groups in the formation of intermolecular interactions. The strongest interaction in these crystals is the N–H⋯O hydrogen bonds which form centrosymmetric dimers. Stacked columns of such dimers have been recognized as the main structural motif of columnar crystals of carboxamide derivatives. The weakening of the thiocarboxamide group acceptor properties as compared to those of the carboxamide group results in the close interaction energies of the hydrogen bonded and stacked dimers in the coumarin-3-thiocarboxamide crystal. Both these interactions form corrugated chains as the primary structural motif. The stacking interactions proved to be the strongest in the 2-iminocoumarin-3-thiocarboxamide crystal where they form stacked columns as the primary basic structural motif. The neighbouring chains interact stronger in two opposite directions forming layers as the secondary structural motif in both crystals of thiocarboxamide derivatives. These crystals have a columnar-layered structure. [ABSTRACT FROM AUTHOR]

This study of 3‐(5‐phenyl‐1,3,4‐oxadiazol‐2‐yl)‐2H‐chromen‐2‐one, C17H10N2O3, 1, and 3‐[5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazol‐2‐yl]‐2H‐chromen‐2‐one, C16H9N3O3, 2, was performed on the assumption of the potential anticancer activity of the compounds. Three polymorphic structures for 1 and two polymorphic structures for 2 have been studied thoroughly. The strongest intermolecular interaction is stacking of the 'head‐to‐head' type in all the studied crystals. The polymorphic structures of 1 differ with respect to the intermolecular interactions between stacked columns. Two of the polymorphs have a columnar or double columnar type of crystal organization, while the third polymorphic structure can be classified as columnar‐layered. The difference between the two structures of 2 is less pronounced. Both crystals can be considered as having very similar arrangements of neighbouring columns. The formation of polymorphic modifications is caused by a subtle balance of very weak intermolecular interactions and packing differences can be identified only using an analysis based on a study of the pairwise interaction energies. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]