H-Bonded Duplexes based on a Phenylacetylene Backbone.

Complementary phenylacetylene oligomers equipped with phenol and phosphine oxide recognition sites form stable multiply H-bonded duplexes in toluene solution. Oligomers were prepared by Sonogashira coupling of diiodobenzene and bis-acetylene building blocks in the presence of monoacetylene chain terminators. The product mixtures were separated by reverse phase preparative high-pressure liquid chromatography to give a series of pure oligomers up to seven recognition units in length. Duplex formation between length complementary homo-oligomers was demonstrated by 31P NMR denaturation experiments using dimethyl sulfoxide as a competing H-bond acceptor. The denaturation experiments were used to determine the association constants for duplex formation, which increase by nearly 2 orders of magnitude for every phenol-phosphine oxide base-pair added. These experiments show that the phenylacetylene backbone supports formation of extended duplexes with multiple cooperative intermolecular H-bonding interactions, and together with previous studies on the mixed sequence phenylacetylene 2-mer, suggest that this supramolecular architecture is a promising candidate for the development of synthetic information molecules that parallel the properties of nucleic acids.