Conformational Isomers from Rotation of Diacetylenic Bond in an Ethynylpyrene-Substituted Molecular Hinge

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.