The novel hydrogen bonding motifs and supramolecular patterns in 2,4-diaminopyrimidine–nitrobenzoate complexes

Abstract

The crystal structures of the hydrogen-bonded, 1:1 molecular complexes of nitro ( ortho, meta and para) benzoic acids with two 2,4-diaminopyrimidine derivatives (trimethoprim and pyrimethamine) have been investigated in detail ( 1– 5 ). In all the crystal structures except pyrimethamine o-nitrobenzoate ( 3 ), the carboxylate group of the respective anions interacts with the protonated trimethoprim or pyrimethamine moiety in a linear fashion through a pair of N–H⋯O hydrogen bonds to form a cyclic hydrogen-bonded motif. This cyclic hydrogen-bonded motif is self-organized in different ways to get the novel types of hydrogen bonding motifs and supramolecular patterns. In the crystal structure of pyrimethamine o-nitrobenzoate ( 3 ), the chelating type of hydrogen bonding motif is self-organized to get a helical supramolecular pattern. In the crystal structures of both pyrimethamine m-nitrobezoate ( 4 ) and pyrimethamine p-nitrobenzoate ( 5 ), a novel type of an alternate arrangement of DADA (D represents donor and A represents acceptor) and DDAA arrays is present, resulting in the formation of hydrogen-bonded ladders.