Salts of 3,5-dinitrobenzoic acid with organic diamines: hydrogen-bonded supramolecular structures in one, two and three dimensions

Abstract

The trigonally trisubstituted carboxylic acid 3,5-dinitrobenzoic acid, (O2N)2C6H3COOH, forms 2:1 salts with a range of organic diamines L, with the general composition [LH2]2+·[{(O2N)2C6H3COO}−]2. When L is a bis-tertiary amine the hard N—H...O hydrogen bonds generate finite three-component aggregates, anion...cation...anion, and these aggregates are further linked by soft C—H...O hydrogen bonds to form one-dimensional molecular ladders when L is N,N,N′,N′′-tetramethyl-1,2-diaminoethane and chains of rings when L is 4,4′-dipyridylethane or 4,4′-dipyridylethene; two-dimensional sheets are formed when L is 1,4-diazabicyclo[2.2.2]octane and a three-dimensional framework is formed when L is N,N′-dimethylpiperazine. When L is the bis-secondary amine piperazine, the hard N—H...O and soft C—H...O hydrogen bonds each generate continuous motifs in the form of distinct chains of rings, the combination of which generates sheets, while when L is the bis-primary amine 1,2-diaminoethane the hard N—H...O hydrogen bonds alone generate a three-dimensional framework.