Reversible single-crystal-to-single-crystal photochemical formation and thermal cleavage of a cyclobutane ring.
A [2+2] cycloaddition reaction has been observed in a number of solids. The cyclobutane ring in a photodimerized material can be cleaved into olefins by UV light and heat. The high thermal stability of the metal-organic salt K2SDC (H2SDC = 4,4'-stilbenedicarboxylic acid) has been successfully utilized to investigate the reversible cleavage of a cyclobutane ring. The two polymorphs of K2SDC undergo reversible cyclobutane formation by UV light and cleavage by heat in cycles. Of these, one polymorph retains its single-crystal nature during the reversible processes. Polymorphs are known to show different physical properties and chemical reactivities. This work reveals that the retention of single-crystal nature is strongly associated with the packing of molecules, which is controlled by kinetics and thermodynamics. The photoemissive nature of the products makes this as a promising material for photoswitches and optical data storage devices.
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543 (Singapore).
Goutam Kumar
GK
Kole
Tatsuhiro
T
Kojima
Masaki
M
Kawano
Jagadese J
JJ
Vittal
CC bond cleavage; coordination polymers; cycloaddition; polymorphism; solid-state reactions