Cyclobenzoin Esters as Hosts for Thin Guests

Nitriles and terminal alkynes are important compounds in industrial and academic settings. Their supramolecular binding has been challenging without the intervention of metals, because of the small dimensions of their linear –C≡N and –C≡CH groups. Using a combination of crystallography and computation, we have shown that cyclotetrabenzoin esters can host terminal triple bonds of alkynes and nitriles in their electron-poor cavities. Within these cavities, π-clouds of triple bonds can establish favorable and virtually equidistant interactions with the four aromatic walls of the cyclotetrabenzoin skeleton. Binding is selective for aliphatic nitriles and terminal alkynes, with their aromatic counterparts residing outside of the cyclotetrabenzoin cavity. These findings are of relevance in the binding, separations, and activation of these and other linear molecular guests.