Medicinal chemistry of indole analogs constitutes important therapeutic agents with antioxidant, anti-HIV and anti-cancer activities. Indole nucleus is frequently found in synthetic and natural products, pharmaceuticals, functional materials, agrochemicals, etc. The title compound, N-(2-(2-(4-chlorophenoxy)acetamido)phenyl)-1H-indole-2-carboxamide (5), has been synthesized in good yield by stirring the compound N-(2-aminophenyl)-2-(4chlorophenoxy)acetamide (3) with 1H-indole-2-carboxylic acid (4), in dry dichloromethane followed by the addition of 2,6-lutidine, and o-(benzotriazol-1-yl)-N,N,N',N'-tetramethyl uraniumtetrafluoroborate in cooled condition. Compound 5 was synthesized and characterized by the conventional spectroscopic techniques ( 1 H NMR, 13 C NMR and LC-MS) and the three-dimensional structure was elucidated by using single crystal X-ray diffraction methods. It crystallizes in the monoclinic crystal system with space group P21/c. The structure was solved by direct methods and refined by full matrix least square procedure to a final R value of 0.043 for 2490 observed reflections. Three intra-molecular interactions of the type N-H···N and C-H···N were observed. The packing of molecules in the unit cell is governed by N-H···O and C-H···O intermolecular H-boned interactions which leads to the formation of infinite staking chain along [001] direction. In addition, two weak C-H···π interactions also contribute to molecular packing.

A comparative crystallographic and detailed computational analysis of four known 6-chloropurine X-ray structures, accessed from the CSD repository, has been reported in this paper. The quantum chemical analysis of each structure, including the optimized geometry, lattice energy, Hirshfeld surface, HOMO-LUMO energies, has been made to account for the properties of this class of biologically important organic materials. The lattice energy contribution in terms of intermolecular interactions, responsible for the packing stability, has been estimated by PIXEL procedure. Three-dimensional Hirshfeld surfaces and the corresponding 2D-fingerprint plots include the analysis of short intermolecular contacts. The π…π interactions and stacking features of molecules in the packing, have been analyzed using shape index and curvedness plots.

The title hydrate, C13H10ClN3O·H2O, is the orthorhombic polymorph of the previously reported monoclinic compound [Fun et al. (2012). Acta Cryst. E68, o2303–o2304). In the title compound, the dihedral angle between the pyridine and benzene rings is 18.0 (2)°. In the crystal, the Schiff base molecules and water molecules are linked via O—H...O, N—H...O and O—H...N hydrogen bonds, forming a two-dimensional network parallel to (001). In addition, the Schiff base molecules are linked end-to-end by weak C—H...Cl hydrogen along the c-axis direction, forming an overall three-dimensional network. Weak C—H...π interactions are also observed.

Although the non-covalent interactions such as hydrogen bonds and Van der Waals bonds are considered as weak but have a significant impact on the characteristics of the molecule in solution and the crystalline phase. The nature and strength of such intermolecular interactions result in various physicochemical and biological properties in crystal structures. In the present study, a quantitative analysis of intermolecular interaction in the crystal packing of some bromine substituted coumarin derivatives has been undertaken for lattice energy and intermolecular interaction energies analyses using a computational approach. The analysis shows that the energy contribution of halogen bonds such as C-Br…O and C-Br…π is quite significant in the crystal structures of bromine substituted coumarins. Besides, the C-H…O, C-H…Br and π…π interactions are also found to have a profound effect on the molecular packing of these structures. Molecular interactions with reference to the packing mechanism in each molecule are studied in detail. It is expected that empirical analysis of molecular energy interactions will help in understanding the role of various structural motifs in crystal packing

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