Elastic Cycles as Flexible Hosts: How Tubes Built by Cyclic Chalcogenaalkynes Individually Host Their Guests

Tubular structures arise in the solid state through close chalcogen–chalcogen contacts. Several examples containing sulfur and selenium centers are presented. In the case of cyclic systems of ring size 22–33 the resulting tubes are capable of including π-systems as guest molecules. For hexaselenacyclotriacontahexayne 8(5) it is shown that the cycle is flexible and adopts a smaller space in the case of furan or n-hexane as compared with that of mesitylene. This behavior is attributed to the relatively low torsional barrier at the chalcogen-substituted butadiyne unit.