Synthesis and Photophysical Properties of Chalcophenes-Embedded Cycloparaphenylenes

[n]­Cyclo-4,4′-biphenylene-2″,5″-thienylenes ([n]­CP2T, n = 3, 4), [n]­cyclo-4,4′-biphenyl-ene-2″,5″-selenylenes ([n]­CP2S, n = 3, 4), and [n]­cyclo-4,4′-biphenylene-2″,5″-ethylenedioxythienylenes ([n]­CP2E, n = 3) were synthesized in few steps with high overall yields. These nanorings were prepared through platinum-mediated cyclooligomerization of 2,5-bis­(4-pinacolboryl-phenyl)­chalcophenes. The X-ray crystallographic analysis of [4]­CP2S showed that it employed a cone-shaped conformation in the solid state. Furthermore, their photophysical properties were investigated by using the UV–vis absorption spectra and fluorescence spectra. In particular, selenophene and 3,4-ethylenedioxythiophene-embedded cycloparaphenylenes, which showed significant red shifts in the UV–vis absorption and fluorescence spectra compared with thiophene analogues, are reported here for the first time.