Insight into the shear stability of the polymer-metal complexes: Experiment and density functional theory studies

We present a detailed investigation on the shear stability of the PAA-M (M = Co(II), Ni(II) and Cu(II)) complexes using sodium polyacrylate (PAAS) as complexant by shear induced dissociation coupling with ultrafiltration (SID-UF) experiment and density functional theory studies. The theoretical calculations were performed at the PBE0/def2-TZVP level of theory for the complexation geometries which used two monomers of PAAS ligands bind with M cations. Two different coordination modes with or without the hydration of metal cations have been considered in the calculations. Different analyses were carried out: optimized configuration, interaction energy, Gibbs free energy change, frontier molecular orbital and electron transfer. The results of theoretical calculations were in good agreement with experimental work although with quite small stability difference. The presence of water molecules as explicit solvent clearly affected the most favorable binding configurations and presented a more credible prediction on the stability difference of PAA-M complexes. The findings of charge decomposition analysis showed that the origin of the difference in the stability of PAA-M complexes related to the number of electrons transferred from the ligands to the central metal cations.