Research

This study reveals the unique coordination behavior of Ni(II) with flexible tripeptides (L). Replacing the metal(II) center reveals that no other metal ions exhibit a similar distribution of formation propensities to Ni(II), indicating their different abilities to form monodentate, bidentate, and tridentate coordination with the flexible tripeptide. Given that the octahedral coordination formed by Ni(II) ions and tripeptides in crystal structures is unique, substituting Ni(II) with other metal ions may not yield the same cyclic supramolecules such as Ni₁₄L₁₄, Ni₁₂L₁₂, and the catenane Ni₂₈L₂₈.

This study investigates the self-assembly mechanism of Ni(II)-tripeptide supramolecules through comprehensive conformational exploration. The most stable conformers are different from those observed in crystal structures, suggesting that the crystal conformation must arise from specific stabilizing factors. Incorporating solvent effects and counter anions, the coordination behavior of Ni(II) with the monodentate, bidentate, and tridentate sites of the stable tripeptide conformers was investigated. The potential formation routes to octahedral coordination were revealed using the AFIR method.