Proton-transfer supramolecular salts resulting from 3,5-dinitrobenzoic acid and aminomethyl pyridine

Three hydrogen-bonding three-dimensional (3D) networks of ammonium carboxylate salts formed between 3,5-dinitrobenzoic acid and aminomethyl pyridine (2-, 3-, 4-) are described here. During solution crystallization, the hydrogen atom transfers from the carboxylic acid to the amine to yield ammonium carboxylate salts, which feature three charge-separated N⁺- H⋯O^- hydrogen bonds to afford two types of one-dimensional (1D) hydrogen-bonding columns. Of the three structures, ((2-pyridylmethyl) ammonium) (3,5-dinitrobenzoate) (1) shows a hydrogen-bonding column which consists of alternating R12(4) and R24(8) rings whereas ((3-pyridylmethyl) ammonium) (3,5-dinitrobenzoate) (2) results in a hydrogen-bonding column which comprises repeating R34(10) rings. ((4-pyridylmethyl)ammonium) (3,5-dinitrobenzoate) (3) bears a unique shape of Chinese knot among four cations instead of the column constructed by rings. From this we can gather information about the possible position effects of functional groups on the overall packing.