Synthesis And Properties Of Polyoxometalate-based Photochromic Materials

Due to the excellent photosensity and thermosensity, photochromicmaterials have been paid much attention by scientists over the years. Asthe most applicable functional materials, photochromic materials haveshown wide applications in optical data storge, display devices,anti-counterfeit materials, etc. Many organic photochromic compoundsexhibit excellent sensitivity and flexibility; However, they have manyshortages in sturdiness and stability. Polyoxometalates (POMs) are adiverse family of metal-oxygen clusters made up of early transitionalmetals (V, Mo, W, etc) with unique physical and chemical properties. Bythe introduction of photochromic organic moieties via covalent bonds, wecan get a series of organic-inorganic hybrids with an almost unmatchedrange of structural types and functions, which has great significance onthe research in novel photochromic materials.First of all, we successfully synthesized four salophen-basedazobenzene compounds, which was easily prepared and provided theoretical support for the synthesis of POMs-based photochromicmaterials via covalent interactions. These compounds were characterizedby FT-IR,1H-NMR, ESI-MS and elemental analysis. The photochromismand liquid crystal properties of these compounds were studied by UV-Vis,differential scanning calorimetry(DSC) and polarization microscope.On the basis of the above research, by the introduction ofazobenzene moieties, we successfully synthesized two POMs-basedphotochromic materials via covalent bonds, which were characterized byFT-IR,1H-NMR, ESI-MS, elemental analysis and single-crystal X-raydiffraction. Due to different linker between azobenzene moieties andPOMs, different photochromism of these compounds can be observed.Thus, UV-Vis and1H-NMR study indicated the rate and extent of thetrans-to-cis isomerization, respectively.