As a new type of π-conjugated oligomers, we synthesized two types of macrocyclic compounds with three 1,8-anthrylene units and acetylene or diacetylene linkers to construct strained frameworks. One is compound 1 with three diacetylene linkers, and the other is compound 2 with one diacetylene and two acetylene linkers, the latter having two isopropyl groups to increase the solubility.
The linear precursors were prepared by the Sonogashira and Eglington coupling reactions, which were then cyclized by the Eglinton coupling to give the desired macrocyclic compounds in 22-34% yield as yellow crystals. X-ray analysis revealed that compound 1 took a nearly C₂ symmetric structure with distorted alkynic carbons (bond angles 166-174°). On the contrary, the ¹H NMR signal pattern was symmetric even at -60 °C in CDCl₃ because of the facile dynamic processes. The structure of 2 was optimized by the DFT calculation to give a saddle-like structure of C_s symmetry. All bond angles at the sp carbons in 2 are smaller than 170°, and there are significant out-of-plane deformations in the anthracene rings. The ¹³C NMR signals due to alkynic carbons in these compounds are shifted by 3-8 ppm to the lower field relative to the strain-free cyclic tetramers because of the bending deformations. The UV and fluorescence spectra of these compounds are compared with those of the related oligomers.

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/8217 must be provided.

1. Photoreactions of 1,8-Anthrylene-ethynylene Acyclic Oligomers