Molecular to supramolecular structure: Influence of coordination environment in azo-dye complexes

The mixed donor ligand 2-(phenylazo)imidazole (L-1) forms a family of seven different metal complexes of varying coordination environments at the molecular level. The presence of hydrogen bonding sites along with metal coordination sites results in the formation of three-dimensional (3D) self-assembled supramolecular architectures. Variation of the 3D architecture is a consequence of fine-tuning of the coordination behavior of the mixed donor ligand. Compatibility of the hard-soft nature of the metal ion and the mixed donor L-1 controls the long-range 3D order in the solid-state. The solid-state structures of L, and their complexes were identified by single crystal X-ray structure analysis. The optical, electrochemical, and thermal properties of azo-dyes and their metal complexes were studied in detail and compared with their molecular structures.