Supramolecular assemblies of 4,7-phenanthroline with various aromatic polycarboxylic acids

• Synthesis of five molecular complexes of novel ligand 4,7-phenanthroline.
• Structures of the complexes analyzed by single crystal X-ray diffraction.
• Strong O-H⋯O/O-H⋯N/N+-H⋯O− and weak C-H⋯O hydrogen bonds dictate the packing.
• Significant role of water in production of supramolecular assemblies.

Five molecular complexes 1a–1e, of 4,7-phenanthroline (1) with various aromatic polycarboxylic acids such as benzene-1,3-dicarboxylic acid (a), pyridine-2,6-dicarboxylic acid (b), pyridine-2,5-dicarboxylic acid (c), benzene-1,2,3,4,5-pentacarboxylic acid (d) and 1,2,3,4,5,6-benzenehexacarboxylic acid (e) have been prepared and characterized by single crystal X-ray diffraction and thermogravimetric analyses. The analysis shows that all the assemblies crystallized as hydrates, except complex, 1c, formed between 1 and pyridine-2,5-dicarboxylic acid. Single crystal X-ray data reveals that the packing patterns of all the molecular complexes have been directed by strong hydrogen bonding O-H⋯O/O-H⋯N/N+-H⋯O− and weak hydrogen bonding C-H⋯O interactions. All the hydrated assemblies aggregate through the formation of cyclic networks as basic recognition pattern. Further, we observed that water molecules play significant role for production of supramolecular assemblies.

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