Facile synthesis and photochromic properties of diarylethene‐containing terpyridine and its transition metal (Zn2+/Co2+/Ru2+) complexes

Several transition metal complexes based on 2,3‐bis(2,4,5‐trimethyl‐3‐thienyl)maleic anhydride (DTE) bearing terpyridine (TPY) have been designed and synthesized. Furthermore, the photochromism of the free ligand and the influence of transition metal moieties on the photochemical properties have been thoroughly characterized by monitoring the changes in their UVvis spectra. Compounds 3–6 all display excellent response to UV irradiation, especially Co complex 5 with optimum sensitivity that took only 5 s to reach photostationary state. The photochromic properties of DTE unit have been found to be strongly influenced by the bridging transition metals, as complexes 4 (L–Zn–L) and 6 (L–Ru–L) exhibit much better photochromic properties in tetrahydrofuran solution than complex 5 (L–Co–L) and the free ligand 3 (L). It is worth noting that the optical/chemical thermal stabilities of photochromic compounds 3–6 are all greatly improved after the precursor functionalized with TPY and further coordinated with metal ions. Copyright © 2012 John Wiley & Sons, Ltd.