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.