Conformational isomers from rotation of diacetylenic bond in an ethynylpyrene-substituted molecular hinge

(Chemical Equation Presented) The first example of isolation and X-ray crystallographic structural characterization of two conformers arising from rotation along a diacetylenic bond is reported. In both the conformers extensive π-π interactions are observed in the solid state. VT-NMR and fluorescence spectroscopic studies in solution suggest that the closed and open conformers are in equilibrium and that the closed conformer is the predominant species at room temperature. © 2008 American Chemical Society.