title: Backbone-rigidified oligo(m-phenylene ethynylenes).
abstract: Oligo(m-phenylene ethynylenes) (oligo(m-PE)) with backbones rigidified by intramolecular hydrogen bonds were found to fold into well-defined conformations. The localized intramolecular hydrogen bond involves a donor and an acceptor from two adjacent benzene rings, respectively, which enforces globally folded conformations on these oligomers. Oligomers with two to seven residues have been synthesized and characterized. The persistence of the intramolecular hydrogen bonds and the corresponding curved conformations were established by ab initio and molecular mechanics calculations, 1D and 2D (1)H NMR spectroscopy, and UV spectroscopy. Pentamer 5, hexamer 6, and heptamer 7 adopt well-defined helical conformations. Such a backbone-based conformational programming should lead to molecules whose conformations are resilient toward structural variation of the side groups. These m-PE oligomers have provided a new approach for achieving folded unnatural oligomers under conditions that are otherwise unfavorable for previously described, solvent-driven folding of m-PE foldamers. Stably folded structures based on the design principle described here can be developed and may find important applications.
authors.affiliation: Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, New York 14260, USA.
authors.forename: Xiaowu
authors.initials: X
authors.lastname: Yang
authors.forename: Lihua
authors.initials: L
authors.lastname: Yuan
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Yamato
authors.forename: Amy L
authors.initials: AL
authors.lastname: Brown
authors.forename: Wen
authors.initials: W
authors.lastname: Feng
authors.forename: Mako
authors.initials: M
authors.lastname: Furukawa
authors.forename: Xiao Cheng
authors.initials: XC
authors.lastname: Zeng
authors.forename: Bing
authors.initials: B
authors.lastname: Gong
mesh_terms: D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
chemical_list: D011108:Polymers; C473966:poly(phenylene ethynylene)