title: Quantifying intrinsic ion-driven conformational changes in diphenylacetylene supramolecular switches with cryogenic ion vibrational spectroscopy.
abstract: We report how two flexible diphenylacetylene (DPA) derivatives distort to accommodate both cationic and anionic partners in the binary X(±)·DPA series with X = TMA(+) (tetramethylammonium), Na(+), Cl(-), Br(-), and I(-). This is accomplished through theoretical analysis of X(±)·DPA·2D2 vibrational spectra, acquired by predissociation of the weakly bound D2 adducts formed in a 10 K ion trap. DPA binds the weakly coordinating TMA(+) ion with an arrangement similar to that of the neutral compound, whereas the smaller Na(+) ion breaks all intramolecular H-bonds yielding a structure akin to the transition state for interconversion of the two conformations in neutral DPA. Halides coordinate to the urea NH donors in a bidentate H-bonded configuration analogous to the single intramolecular H-bonded motif identified at high chloride concentrations in solution. Three positions of the "switch" are thus identified in the intrinsic ion accommodation profile that differ by the number of intramolecular H-bonds (0, 1, or 2) at play.
authors.affiliation: Sterling Chemistry Laboratory, Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520, USA.
authors.forename: Arron B
authors.initials: AB
authors.lastname: Wolk
authors.forename: Etienne
authors.initials: E
authors.lastname: Garand
authors.forename: Ian M
authors.initials: IM
authors.lastname: Jones
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Hamilton
authors.forename: Mark A
authors.initials: MA
authors.lastname: Johnson