Developing an understanding of the binding hierarchy of imidazole with M 2+ ions must begin with an assessment of the kinetics of the imidazole-M 2+ interaction in an ideal environment in which the coordination interactions are not affected by other features of the system. An example of a nonideal environment might be the conformational restrictions on the imidazole-M 2+ interactions in biological systems due to the structural self-assembly of the protein strands. Thus, here we aim to study the binding hierarchy of histidine and imidazole with M 2+ ions by utilizing a flexible telechelic polymer hydrogel as the model system. In this configuration, the telechelic end-groups of the polymers can be functionalized with either histamine or imidazole to induce transient crosslinking with Ni 2+ , Zn 2+ , and Cu 2+ ions. The binding affinity between the ligands and the M 2+ can thus be studied by monitoring the viscoelasticity of the hydrogel network, as the dissociation kinetics of such structures govern the relaxation of the hydrogel network. Furthermore, this configuration allows control of the stoichiometric ratio of histidine and M 2+ , which provides an easy handle for controlling the metal-ligand coordination number (ML1, ML2, ML3, ML4). Thus, here we characterize the viscoelasticity of transient networks formed with histamine or imidazole and Ni 2+ , Zn 2+ , and Cu 2+ ions under different stoichiometric conditions and complement this effort with a density functional theory (DFT) investigation of the overall affinity of complexes at different coordination numbers. We thus show that the hierarchy of Ni 2+ , Zn 2+ , and Cu 2+ binding stability is dramatically affected by the coordination number of the metal-ligand interaction (Fig. ), and provide a structural explanation of this hierarchy.