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

Abstract

Abstract The title π-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 C2 symmetry, and the skeletal swing between the two enantiomeric forms via a square prism form was observable by dynamic NMR spectroscopy (barrier: ca. 38 kJ mol−1). The structural and spectral properties as well as some reactivities of the cyclic tetramer and related acyclic oligomers up to heptamer are reported.