Extending helicity—capturing the helical character of longer ortho-phenylene ethynylene oligomers

Folding and Aggregation of Cationic Oligo(aryl‐triazole)s in Aqueous Solution

“…An attempt to confirm this flipping by NMR spectral analysis was unsuccessful due to drastic aggregation of oligomers at the millimolar range (vide infra). In fact, “horizontal flipping” of the terminals is a dynamic nature of helices, as observed in ortho ‐phenylene–ethynylene foldamer by Tew et al,28a and in abiotic metallofoldamers by Fox and co‐workers 28b. Surprisingly, no clear isodichroic point was observed when the solvent was changed from methanol to water.…”

Recent advances in arylene ethynylene folding systems: Toward functioning

“…When the length of oPE foldamer increases, such as for oligomers 76 and 77, the possible conformations of the folded state become more complex. By making assignment of the spin system for the homo-oPE foldamers [127], Tew et al clarified the folded conformation of hexamer 77 [128]. Chemical shifts of protons on the central ring of pentamer 76 remained constant; other protons on rings 1, 2, 4, and 5 shifted upfield with increased solvent polarity; whereas protons of all 6 phenyl rings in the hexamer shifted upfield when solvent polarity increased.…”

Regioselective Carbyne Transfer to Ring-Opening Alkyne Metathesis Initiators Gives Access to Telechelic Polymers

“…The performance of these polymers relies to a significant extent on the intra- and intermolecular interactions that span the gap between the nano- and the microscopic scale. − While the primary sequence of monomers largely determines the band gap and optical absorption, the preferred secondary structure adopted by polymer chains controls critical performance parameters like the mean free path of charge carriers and excitons. − Lastly, the challenge to direct the self-assembly of polymers into ordered microscopic domains, a tertiary structure, is a key technology in the fabrication of bulk heterojunctions for OPVs. − Herein, we focus on conjugated polymers derived from poly -(phenylene ethynylene) (PPE) featuring a pattern of alternating aromatic rings and CC triple bonds. By varying the substitution pattern ( ortho -, meta -, para -) along the aromatic rings lining the backbone of the polymer the secondary structure of PPEs can be adjusted from a linear zigzag to a helically coiled conformation. − Classical syntheses of PPEs have relied on transition-metal-catalyzed cross-coupling or alkyne cross-metathesis (ACM) step-growth polymerizations that suffer from unselective chain termination and uncontrolled chain transfer and result in polymers with disproportionately broad molecular weight distributions. − We recently demonstrated the use of living ring-opening alkyne metathesis polymerization (ROAMP) of ring-strained cyclic alkynes with initiators derived from [RCMo­(OC­(CH 3 )­(CF 3 ) 2 ) 3 ] for the controlled synthesis PPEs featuring either a linear or cyclic topology …”