X-ray diffraction and theoretical study of molecular and crystal structure of new crystalline aryl- and alkyl-substituted N-(adamantan-1-yl)amides: Similarities and differences

Abstract

The molecular structure and crystal packing of new aryl and alkyl N-(adamantan-1-yl)amides derivatives А1–А7 were analyzed, and their intermolecular interaction parameters were found using X-ray diffraction, topological analysis within Bader's theory of “Atoms in molecules”, PIXEL method, and Hirshfeld surface analysis. N–H…O and С–Н…О hydrogen bonds and numerous Н…Н contacts are formed in the crystals of adamantylamides А1–А7. The adamantylamide molecules A1–A7 form a С(4) supramolecular chain synthon via N–H…O hydrogen bonds. An acetamide oxygen atom in the crystals of A1, A3–A5, and A7 is involved into unsymmetrical bifurcated bonds, in which one component is N–H…O and the other one is С–Н…О. The contribution of the O…Н contacts to the Hirshfeld surface is higher for alkyl adamantylamides than that for the aryl derivatives, whereas the packing index is lower for the alkyl derivatives than that for aryl one. The position of an acetamide group relative to adamantane framework in all structures is fixed by C–H…O intramolecular hydrogen bonds. The stabilization energy of the molecular pairs apparently depends on orientation of substituents and the mutual orientation of molecules in the pair that create favorable conditions for numerous intermolecular interactions.