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.