Photochromic properties of polycrystals: 2,3-diarylcyclopentenone and its adduct with a metal-organic coordination polymer

Abstract

In order to obtain crystalline photochromic materials combining the advantages of photochroms in liquid and polymeric solutions (high quantum yields) and in the solid state (enhanced resistance to photodegradation) a photochromic adduct consisting of a metal-organic framework [Zn₄(dmf)(ur)₂(ndc)₄] (ndc^2– is 2,6-naphthalenedicarboxylate, ur is urotropine, dmf is N,N-dimethylformamide) and 2,3-bis-(2,5- dimethylthiophen-3-yl-cyclopent-2-en-1-one) is synthesized (compound 1). The photochemistry of the adduct is studied. Solid 2,3-diarylcyclopentenone exhibits photochromism typical of diarylethenes. Quantum yields of the adduct photocoloration and photobleaching turn out to be 1.5 and 3 times higher respectively than those for solid compound 1 and lower than those of solution 1 in acetonitrile by an order of magnitude. The number of photochemical cycles for compound 1 in the solution, the solid state, and the adduct composition is limited by the monomolecular side reaction.