The formation of supramolecular polymers is possible through directional and favorable intermolecular interactions that are much weaker that conventional covalent bonds. These interactions grant their respective systems reversibility in binding interactions, allowing molecular systems to achieve dynamic behavior. An important goal in supramolecular chemistry is the development of stimuli-responsive systems where the strengths of these binding interactions can be perturbed via external stimuli, such as light, temperature, and/or pH. Another possible stimulus is an applied voltage, but this has not been as thoroughly investigated as the other examples. In an attempt to exemplify this perturbation, a system known for self-complementary H-bonding – ureidopyrimidinones (UPy) – is being used. Several different UPy’s with electroactive substituents have been investigated in our group. One such UPy derivative is UPyFc, where a ferrocene is attached to the pyrimidone side of the UPy. Voltammetry methods reveal that dimerization of UPyFc can be electrochemically controlled. The data are consistent with a square scheme mechanism for the reversible UPyFc / UPyFc+ redox couple in dichloromethane, where dimerization is inhibited upon oxidation and resumed upon reduction. From these preliminary studies, electro-inactive UPy oligomers are being developed with the goal of altering the physical properties of bulk non-polar organic solutions containing a mixture of UPy oligomer units and electro-active UPy derivatives. It is expected that the formation of UPy hetero-dimers between UPyFc and electro-inactive UPy oligomer units will prevent polymerization resulting in a low viscosity solution. Oxidizing UPyFc to UPyFc+ will break these hetero-dimers apart, allowing UPy polymerization to occur. This will result in an increase in the viscosity of the solution. Based off of preliminary studies, this should be a reversible process in which the physical properties of bulk solutions can be altered by controlling H-bonding interactions via an electrochemical redox reaction.

Perturbation of ureidopyrimidinone polymerization via electrochemical oxidation of a ferrocene-substituted ureidopyrimidone

2019 Fall National Meeting

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