Aromatic oligourea foldamers represent an interesting class of biomimetic foldamers known by its planarity, hydrogen bonding capability, and pi-stacking ability. Similar to other biomimetic foldamers, oligoureas are stabilized by non-covalent interactions. Several oligoureas are reported to fold into a variety of conformations such as helical, switchable conformations, �-turn motifs, sheet-like structures and macrocycles. In addition to stable structures with rigid backbones that mimic biological structures, helical oligourea structures that exhibit dynamic behavior have garnered attention due to the possibility of controlling helical handedness. Controlling helicity in synthetic compounds has possible applications in a number of areas including chemical sensing, catalysis and biology. It has been previously shown that adding N,N'-substituents to N,N'-diphenylurea units induce a folded conformation. In this work, we investigate the molecular basis for the conformational propensity of N,N'-substituted-N,N'-diphenylurea oligomers. We will present detailed analyses of the torsional motions around the urea bonds (Figure 1) for a series of compounds with varying substituents. We will also show conformational distributions of the above compounds and a series of oligomers derived from molecular dynamics simulations. Further, we demonstrate how chain length, chiral substituents, and nature of solvent affect the conformational preference and dynamics of aromatic oligoureas. IR and NMR spectroscopy experiments have been carried out to validate our computational results.Figure 1. N,N'-substituted-N,N'-diphenylurea monomer unit

Conformational propensities and dynamic behavior of aromatic oligourea foldamers

248th National Meeting (2014)

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