Acceptor or Donor (Diaryl B or N) Substituted Octupolar Truxene:  Synthesis, Structure, and Charge-Transfer-Enhanced Fluorescence

Two diaryl B- and N-substituted truxene charge-transfer compounds <b>B3 </b>and <b>N3</b> have been synthesized. The fluorescence intensities of several nonfunctionalized truxene compounds are 1 order of magnitude weaker than that of <b>B3</b> and <b>N3</b>. To reveal the structure−property correlations, the X-ray structures of <b>B3</b> and <b>N3</b> and their precursors <b>3</b> and <b>4</b> have been determined. The extended molecular dimension, the especially shortened B−C bond, and the improved planarity of <b>B3</b> can serve as direct structural evidence for the charge transfer.