Chemistry of Anthracene-Acetylene Oligomers.II.Synthesis,Structure,and Properties of 1,8-Anthrylene-Ethynylene Cyclic Tetramers and Related Acyclic Oligomers

摘要

The title pi-conjugated oligomers consisting of anthracene and acetylene units were synthesized to construct a new type of three-dimensional organic architecture.An acyclic chain was extended by the sequence of the Sonogashira coupling and the desilylation from 1,8-diethynylanthracene derivatives and 1,8-diiodoanthracene to form a tetramer,which was then coupled intramolecularly to afford a cyclic tetramer as orange crystals.It is characteristic that a substituent free cyclic tetramer shows the hypochromic effect in the UV spectrum and the presence of an excimer-type emission in the fluorescence spectrum.X-ray analysis revealed that the cyclic tetramer took a diamond prism structure of nearly C_2 symmetry,and the skeletal swing between the two enantiomeric forms via a square prism form was observable by dynamic NMR spectroscopy(barrier:ca.38kJmol~(-1)).The structural and spectral properties as well as some reactivities of the cyclic tetramer and related acyclic oligomers up to heptamer are reported.