Photochromic, organogelating and self-sorting behaviour of di-(dithienylethene) derivatives

Abstract

A series of di-(dithienylethene) (DTE) tetraamides 4 diDTE-X-NHR was synthesized and characterized. Their organogelation property could be rationally optimized by controlling the extent of intramolecular vs. intermolecular hydrogen bonding and also by tuning the extent of side chain interdigitation. Among these compounds, diDTE-Dec-NHDodec4e showed excellent gelation properties with minimum gelation concentration (MGC) values ≤10 mg mL⁻¹ in a wide variety of aromatic solvents. Upon UV (313 nm) irradiation, 32% of the DTE functionality in 4e underwent photocyclization accompanied with a photochromic change and a substantial weakening of the gel network structure. The pure doubly-cyclized isomer 4e-cc was separated and found to be a very weak organogelator (MGC ∼25 mg mL⁻¹) in a limited number of aromatic solvents. More interestingly, self-sorting of 4e and 4e-cc was observed in a 1 : 1 mixture of 4e and 4e-cc freeze-dried gel sample, indicating a high degree of non-self discrimination was present in the mixed gel of these two structurally similar isomers. The results demonstrated that such di-DTE derivatives are photochromic materials with interesting organogelating and self-sorting properties.