Synthesis And Photochromic Properties Of Diarylethene-containing Terpyridine Derivatives And Its Transition Metal Complexes

Photochromic molecules have been studied extensively because of their capability tomodulate physical and chemical properties for photoresponsive functional materials, such asrewritable data memories, molecular optical switches and chemical sensing. Among thesematerials, the diarylethene derivatives have received much attention for their excellentphotochromic properties with thermal irreversibility, good fatigue resistance and shortresponse time. In recent years, transition metal complexes with ligands containing differentphotochromic families have been developed. In view of the photoswitching capability of themetal complex, organometallic photochromic complex is an interesting alternative to pureorganic photochromes. They can provide new properties deriving from the combination ofredox, optical, and magnetic properties of the metal complexes.The metal terpyridine (TPY) complexes have excellent stability and remarkably highbinding affinity towards transition metal ions, showing photophysical/photochemicalproperties, which have led to the development of various luminescent metal compounds andsensitizers for photovoltaic devices. Therefore, we focus our attention on coupling differentmetal ions with the functionalized photochromic TPY-2,3-bis(2,4,5-trimethyl-3-thienyl)maleic anhydride (DTE). All the compounds1~6have been confirmed by EA, NMR and MSspectra. The influence of transition metal moieties on the photochemical properties andoptical/chemical thermal stabilities of these compounds have been thoroughly characterized.The results indicate that:3~6all display good fatigue resistance and excellent response toUV irradiation, especially Co complex5with optimum sensitivity that takes only5s to reachphotostationary state. The photochromic properties of DTE unit have been found to bestrongly influenced by the bridging transition metals, as4and6exhibit much betterphotochromic properties in tetrahydrofuran solution than5and the free ligand3. The optical/chemical thermal stabilities of photochromic compounds3~6are all greatly improved afterthe precursor functionalized with TPY and further coordinated with metal ions.In addition, two novel diarylethene-containing phenanthroline derivatives11and14withremarkably high linear binding affinity towards transition metal ions have been designed,hoping to form three-dimensional metal organic framework (MOF) with photochromicproperties. With the specific solid-phase crystalline, high stability of MOF, thePhotochromic-MOF can be modified to achieve the real practical application.