Photoresponsive lower-rim azobenzene substituted and bridged calix[4]arenes

Abstract The doubly azobenzene-chain lower-rim substituted calix[4]arenes 6 – 9 were prepared, followed by the doubly bridged biscalix[4]arenes 10 and 11 . All are photoresponsive and detailed studies of the E⇌Z photoisomerization and the Z → E thermal isomerization in 6 and 10 were carried out using UV and 1 H NMR spectroscopic techniques. The three ( EE , EZ and ZZ ) isomers of 6 and 10 were isolated or enriched and fully characterized by 1 H NMR. Kinetic analyses of these transformations of 6 were carried out and revealed a concentration dependent behavior and an interesting sequential course of its photoisomerization.