Interesting organic supramolecular structures constructed by piperazine/N,N′-dimethylpiperazine with aromatic multicomponent acids: Synthon cooperation and structural diversity

Article abstract of DOI:10.1039/c2ce25627d

Crystallographic studies reveal that organic supramolecular structures 1-7 constructed by piperazine/N,N′-dimethylpiperazine with aromatic multicomponent acids are organic salts formed due to the proton transfer from the carboxylic group of the aromatic multicomponent acids to the nitrogen atom of the piperazine/N,N′-dimethylpiperazine. In all salts, the cations and anions are associated via N-H...O(-COO^-) charge-assisted hydrogen bonds, leading to ionic synthons. Competition and cooperation among -COOH, -COO^-, -OH, -NO₂, -NH⁺- and -NH ²⁺- functional groups for the observed hydrogen bond synthons are examined in the seven structures. It is noted that C-H...O hydrogen bonds increase the dimensionality of the supramolecular architectures of the seven salts. The number of acids involved in the complex equals to the number of N-protonated binding sites in the piperazine/N,N′-dimethylpiperazine. Water molecules play a significant role in the formation of the supramolecular architectures. The supramolecular structures of the seven piperazine/N,N′- dimethylpiperazine salts were determined by single-crystal X-ray diffraction, respectively, to understand how variations in their molecular structures and intermolecular interactions influence their supramolecular assemblies. After the formation of salts of 1-7, the melting points are dramatically different, and thermal stability of these compounds were investigated by thermogravimetric analysis (TGA). This journal is