Synthesis and supramolecular assembly of fluorinated biogenic amine recognition host polymers†
Copolymers containing hydroxyl (i.e. vinyl alcohol, VA) or fluorine functionalities are synthetic macromolecules having prominent biomedical applications. The concentration of hydroxyl groups along the polymer chain controls the polymer polarity. Moreover, the introduction of perfluorinated organic moieties via the OH functionalities may lead to macromolecules having potential magnetic resonance imaging (MRI) active properties. The ring-opening metathesis polymerization (ROMP) reaction using well-defined ruthenium-catalyzed systems is one of the most promising synthetic tools to fabricate such polymers. Co-polymerization of norbornene grafted pyridino-18-crown-6 ether (7) with fluorine-functionalized norbornenes (10 and 11) results in polymers bearing host molecular moieties. It has been demonstrated that the complexation of these host copolymers with biogenic amines including dopamine hydrochloride (12) and L-alanyl-L-lysine dipeptide hydrochloride (13) is straightforward. Based on the 1H NMR investigation of the 7 and 12 complexation, an equilibrium constant of log K = 4.3 ± 0.6 could be calculated. The in situ 1H NMR investigations have revealed that the complex formation of 13 with monomer 7 and perfluorinated copolymer cp-7-10 takes place via both the lysine –NH3+ and the alanine –NH3+ moieties. However, in the case of homopolymer poly-7, the lysine–NH3+ group coordination was observed exclusively. According to theoretical calculations, molecular switching of the crown ether structure of both the 7 monomer and its cp-7-10 copolymer were observed from 90 degrees bent to planar structure upon –NH3+ ion coordination.