Molecular Interactions within the Crystal Packing of Busulfan (DNA Cross-Linking Agent) by Hirshfeld Surface Analysis

Background: Non-Covalent Interactions (NCIs) play a vital role in the chemical process. Certain Experimental and theoretical approaches provide information about the stronger and weaker interactions. In the present work, we have implemented Hirshfeld charges based surface mapping to find the weaker interactions between the molecules of busulfan. Objective: The main objective of this work is to recognize the non-covalent interactions which are not simply drawn from the experimental and conventional theoretical approach. It aims to provide more insightful information into the crystallographic structure. Methods: In the present work, we have implemented a Hirshfeld surface mapping which incorporates periodic boundary conditions of the crystalline geometry. Each point of the isosurface is defined by two distances i.e. de, the distance from the point to the nearest atom outside to the surface and di, the distance to the nearest atom inside the surface. Also, for precise identification of intermolecular interactions, mapping by normalized contact distance dnorm is also considered. Fingerprint plot di vs de for various types of interactions were also provided. Results: The Hirshfeld surface and fingerprint plot show the very weak H···H interactions in addition to the O···H interactions. This enables the visualization of very weak interactions. Conclusion: This proposed work on Hirschfeld surface analysis accounts for the solidstate environment of the busulfan, crystallographic parameters and packing information. Hence, the interactions obtained for monomer and extended molecular framework in this work are more reliable to study the intermolecular interactions. The 2D finger print plots revealed the predominant O⋅⋅⋅H interactions within the crystal packing. In addition to O⋅⋅⋅H interactions, H⋅⋅⋅H interaction were also identified.

Hydrogen bonding in two benzene-1,2-diaminium pyridine-2-carboxylate salts and a cocrystal of benzene-1,2-diamine and benzoic acid

The isostructural salts benzene-1,2-diaminium bis(pyridine-2-carboxylate), 0.5C6H10N2 2+·C6H4NO2 −, (1), and 4,5-dimethylbenzene-1,2-diaminium bis(pyridine-2-carboxylate), 0.5C8H14N2 2+·C6H4NO2 −, (2), and the 1:2 benzene-1,2-diamine–benzoic acid cocrystal, 0.5C6H8N2·C7H6O2, (3), are reported. All of the compounds exhibit extensive N—H...O hydrogen bonding that results in interconnected rings. O—H...N hydrogen bonding is observed in (3). Additional π–π and C—H...π interactions are found in each compound. Hirshfeld and fingerprint plot analyses reveal the primary intermolecular interactions and density functional theory was used to calculate their strengths. Salt formation by (1) and (2), and cocrystallization by (3) are rationalized by examining pK a differences. The R 2 2(9) hydrogen-bonding motif is common to each of these structures.

Crystal structure and Hirshfeld surface analysis of 2-amino-4-methoxy-6-methylpyrimidinium 2-hydroxybenzoate

In the title molecular salt, C6H10N3O+·C7H5O3−, the cation is protonated at the N atom lying between the amine and methyl substituents and the dihedral angle between the carboxyl group and its attached ring in the anion is 4.0 (2)°. The anion features an intramolecular O—H...O hydrogen bond, which closes anS(6) ring. The cation and anion are linked by two N—H...O hydrogen bonds [R22(8) motif] to generate an ion pair in which the dihedral angle between the aromatic rings is 8.34 (9)°. Crystal symmetry relates two ion pairs bridged by further N—H...O hydrogen bonds into a tetramericDDAAarray. The tetramers are linked by pairs of C—H...O hydrogen bonds to generate [100] chains. Hirshfeld surface and fingerprint plot analyses are presented.