Weak hydrogen bonding in the structures of three double-acylated aminoantipyrines

The structures of three doubly-acylated 4-aminoantipyrine (AP) compounds where the aryl substituent is varied are reported and analysed in terms of their relative conformation, intermolecular interactions and overall packing; these are N -(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1 H -pyrazol-4-yl)-4-methyl- N -[(4-methylphenyl)carbonyl]benzamide, C 27 H 25 N 3 O 3 , N -(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1 H -pyrazol-4-yl)- N -[(furan-2-yl)carbonyl]furan-2-carboxamide, C 21 H 17 N 3 O 5 , and N -(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1 H -pyrazol-4-yl)- N -[(thiophen-2-yl)carbonyl]thiophene-2-carboxamide, C 21 H 17 N 3 O 3 S 2 . The compounds were crystallized using the encapsulated nanodroplet crystallization (ENaCt) protocol. Where previous singly-acylated AP compounds produced structures with obvious classical hydrogen-bonding motifs, the doubly-acylated derivatives lack classical donors and therefore exhibit weak C—H hydrogen bonds and interactions involving the π-system. All three AP compounds form bifurcated C—H...O interactions having either dimer or chain motifs, with the other structure-directing interactions being dependant on the nature of the aryl substituent.