Thienyl-phenyl Ethylenes with Crown Ether Fragments and Their Photocyclization Products: UV-Vis, NMR, Redox Response for Complexation. A 18-Crown-6 Ether Restricted with a Tricyclic Aromatic Moiety

The synthesis o f new compounds possessing 18-crown-6 fragment is reported: 1-(2-thienyl)-2-(meta-benzo-18-crown-6)stilbene and 1-(3-thienyl)-2-(meta-benzo-18-crown-6)stilbene, as well as two isomeric products of Mallory cyclization of 2-thienylstilbene, containing a tricyclic fragment annulated to the crown ether moiety. Binding constants of these compounds with Ca2+ and Ba2+ have been measured. Besides, dependence of the H-1 NMR chemical shifts o f both stilbenes and cyclization products on their binding to Ba2+ has been studied. Redox response on the complexation is also elucidated. Among the studied compounds, a sterically congested photocyclization product exhibits an unusual dependence of chemical shifts upon complexation, as well as redox behaviour.