Coordination polymer gel derived from a tetrazole ligand and Zn2+: spectroscopic and mechanical properties of an amorphous coordination polymer gel

A tetrazole-based ligand forms a supramolecular gel in the presence of transition metal ions, particularly Zn2+, Cu2+ and Co2+. The gels have been characterized by SEM, TEM, fluorescence spectroscopy, rheometry and fluorescence microscopy. The polymer exhibits a strong fluorescence enhancement upon gel formation. According to DFT calculations, one of Zn2+ is bound to 4 tetrazole moieties and 2 solvent molecules by octahedral structure. The Zn2+-induced gelation does not strongly depend on anions. The Zn2+-tetrazole ligand gel shows a spherical structure with 20-50 nm diameter. The rheological properties of the Zn2+-tetrazole ligand gel were strongly dependent on the concentration of Zn2+.