Synthesis, Structure, and Chiroptical Properties of a Double [7]Heterohelicene

The synthesis of 11a,25a-dibora-11,­12,­25,­26-tetraoxatetranaphtho­[1,2-<i>a</i>:2′,1′-<i>f</i>:1″,2″-<i>j</i>:2‴,1‴-<i>o</i>]­perylene, a double [7]­heterohelicene containing OBO units, has been achieved via tandem demethylation-borylation, representing the highest double helicene reported thus far with all six-membered rings. Single-crystal X-ray analysis clearly demonstrated a significantly twisted structure with the terminal aromatic rings overlapping at both ends, giving the first example of a double helicene with intramolecular π-layers. Such structural features resulted in a high theoretical isomerization barrier of 45.1 kcal/mol, which is the highest value for all the double helicenes ever reported, rendering the achieved molecule with high chiral stability. The (<i>P</i>,<i>P</i>)- and (<i>M</i>,<i>M</i>)-isomers were separated by chiral HPLC and the chiroptical properties were investigated, revealing opposite circular dichroism responses

A Straightforward Strategy toward Large BN-Embedded π‑Systems: Synthesis, Structure, and Optoelectronic Properties of Extended BN Heterosuperbenzenes

A straightforward strategy has been used to construct large BN-embedded π-systems simply from azaacenes. BN heterosuperbenzene derivatives, the largest BN heteroaromatics to date, have been synthesized in three steps. The molecules exhibit curved π-surfaces, showing two different conformations which are self-organized into a sandwich structure and further packed into a π-stacking column. The assembled microribbons exhibit good charge transport properties and photoconductivity, representing an important step toward the optoelectronic applications of BN-embedded aromatics