Through-Space Control of the Persistence of Photogenerated <i>o</i>-Quinonoid Intermediates in Naphthalenes Containing Cofacially Oriented Chromenes and Arenes

Remarkable modulation of the persistence of the photogenerated colored o-quinonoid intermediates via a through-space interaction has been demonstrated in chromenes 1–4 based on 1,8-diarylnaphthalenes. Polar/π interaction is shown to stabilize the closed form of 4 to such an extent that photoinduced coloration is virtually invisible, while the same stabilization in the opened form of 2 permits ready coloration with a long-lived o-quinonoid intermediate.