Multistate pi switches: synthesis and photochemistry of a molecule containing three switchable annelated dihydropyrene units.
[structure: see text] The synthesis of the multistate photochromic switch 3 is described. This switch contains three dihydropyrene (DHP) units in the most conjugated fully closed form 3-c,c,c. The thermally stable form has the central DHP unit open and is 3-c,o,c. NMR and laser flash photolysis experiments were used to characterize the multiple states in the photoswitching of 3 by visible and UV light. Three of the possible five isomeric states of 3-c,o,c were observed. Irradiation of 3-c,o,c by visible light led to the formation of 3-o,o,o via the isomer 3-c,o,o as an intermediate, which were observed by NMR. Irradiation by UV light led to the formation of 3-c,c,c, which decays with a lifetime of 7.5 ms.
Mitchell
Reginald H
RH
Department of Chemistry, University of Victoria, PO Box 3065, Victoria, BC, Canada, V8W 3V6. regmitch@uvic.ca
Bohne
Cornelia
C
Wang
Yunxia
Y
Bandyopadhyay
Subhajit
S
Wozniak
Chelsea B
CB