Synthesis and Stimuli-Responsive Properties of Metallo-Supramolecular Phosphazene Polymers Based on Terpyridine Metal Complexes

In this study, terpyridine functionalized phosphazene based metallo-supramolecular polymers were synthesized by three step reaction method. In the first step, 4′-(4-aminophenyl)-2,2′:6′,2′′-terpyridine was synthesized with p-nitro benzaldehyde and 2-acetylpyridine. Then, the monomer containing six terpyridine (TPY) units attached to the phosphazene was prepared from 4′-(4-aminophenyl)-2,2′:6′,2′′-terpyridine and hexachlorocyclotriphosphazene by a condensation reaction. Finally, metallo-supramolecular phosphazene polymers were synthesised with these TPY functional phosphazenes and different transition metal ions (Cu, Co, Ni, and Zn ions). Prepared metallo-supramolecular polymers containing phosphazene unit were investigated by elemental analysis, different spectroscopic methods, energy dispersive X-ray spectrometry (EDX) and thermal analysis techniques. The stimuli-responsive, optoelectronic and spectroscopic properties of the synthesised metallo-supramolecular phosphazene polymers were investigated for external effects with UV–Vis spectroscopy and electro-analytic techniques. In addition, competitive ligand effect on these metallo-supramolecular polymers was examined with ethylenediaminetetraacetic acid (EDTA). The resulting metallo-supramolecular polymers containing phosphazene unit show very fast stimuli-responsive properties, such as 3 s. they also showed a single reversible redox structure resulting from the bonding of homometallic segments to polymer chain. In addition, they showed d-π transition (in the range of λ = 330–550 nm) depending on the metal (Co, Ni and Zn) ion forming the supramolecular structure. The addition of competing EDTA ligands caused the degradation of metallo-supramolecular polymer structures. These metallo-supramolecular phosphazene polymers are a good alternative smart material for opto-electronic, electrochromic, photochromic and intelligent material applications.