Although formally conjugated, steric interactions force the ortho-phenylenes into highly twisted conformations exhibiting limited delocalization. Recently, however, it has been shown that this twisting results in well-defined helices both in solution and in the solid state; o-phenylenes have therefore been proposed as a new class of chiroptical materials. The actual reasons for this folding behavior are not clear, however: the role of specific arene�arene interactions is not obvious, and common methods of computational chemistry fail to predict the relative stabilities of the various conformers. We have prepared a series of oligomers with varying substitution. The substituent effect on conformer distributions was used, in combination with dispersion-corrected DFT calculations, to evaluate the role of aromatic stacking in determining their folding. From these results, a simple model has been developed which explains several aspects of their behavior, including the sensitivity of their conformational preferences to small changes in the strengths of aromatic interactions. Efforts to use this model to design o-phenylenes with increased folding propensities will also be discussed.

Folding of <i>ortho</i>-phenylenes

246th National Meeting (2013)

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Folding of ortho-phenylenes