Abstract
Hydrogen bonding arrays are useful building blocks for supramolecular chemistry due to their strong hydrogen bond interactions that can form dimers. The strength of the H-bond interactions can be perturbed by applying an external stimuli, in this case electron transfer. Recently, our group has modified Meijer’s four H-bond ureidopyrimidinone (UPy) array1 to make it electroactive by adding a dimethylaminophenyl group. The modified structure forms strong H-bond interactions in CH2Cl2, creating a dimer that can undergo a reversible 2e-oxidation, followed by an irreversible oxidation at more positive potentials. The latter results in the break-up of the dimer due to electrostatic repulsion. For this study, we aim to modify another four H-bond Upy array by introducing a methyl pyridinium redox center as shown below. We hypothesize that this array will prefer the tautomer that presents an ADAD H-bond motif in the starting oxidation state. This motif will form a dimer with relatively weak H-bond interactions due to electrostatic repulsions and also unfavorable secondary H-bond interactions. Upon 2e- reduction, where 1e- is gained for each methyl pyridinium redox center, the H-bond strength should increase due to the loss of repulsive charges and also allows the nitrogen to become a stronger hydrogen acceptor. Since the resulting nitrogen is now a better H-acceptor, there is a possibility of intermolecular proton transfer which will induce the tautomer to have an AADD motif that will further strengthen the H-bonds by favorable secondary H-bond interactions. 1. Beijer, F.H.; Sijbesma, R.P.; Kooijman, H.; Spek, A.L.; Meijer, E.W. J. Am. Chem. Soc., 1998, 120 (27), pp 6761–6769. Figure 1
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