Acrylic Polymers Containing a Nickel Salphen Complex: An Approach to Supramolecular and Macromolecular Systems

The synthesis, characterization and crystallographic analysis is reported of a new Nickel Salphen complex and its radical copolymerization with n-butyl acrylate and methyl methacrylate to produce novel host macromolecules with tunable association against guest anions. Spectrophotometric titrations of the complex and of the polymers revealed that a supramolecular regulation of guest-binding accessibility was enabled by the number of Ni-Salphen units per chain. The latter content in turn, determined the chain size and molecular weight uniformity upon polymerization, and likely increased the strength in interchain/intrachain non-covalent interactions over the nickel center and the acrylic domains. The study also showed that incorporation of the monomer into the acrylic polymer backbone opened the possibility for the nickel binding site to gain access to host:guest stoichiometric discrimination, switching from 1 : 1 (major) and 1 : 2 (minor) both coexisting for the host when in the free form, to mostly 1 : 2 when in the polymerized version.