Photochromism Materials Of POMS Tethered With Coumarin Molecule

Natural product coumarin and these derivatives have two kinds of fluorescent potential groups, which are the six-member heterocyclic and the carbonyl group. The derivatives that show a different color and strong fluorescence with a different range of absorption and fluorescence emission wavelength can be obtained, through the substituents in the loops of coumarin in different position. Coumarin compounds have a highlight property, which leads to the photo-dimerization upon irradiation at UV lights. Coumarin group can be introduced to different polymers to form a variety of "light responsive" functional materials with different physic-chemical properties, which can be controlled through adjusting quantity and irradiation times.Polyoxometalates (POMs) are a class of anionic metal oxides of V, Mo, W, and Nb species, with unique physical and chemical properties, especially with the charge transfer property, which is widely used to develop new materials such as non-linear optical materials, luminescent materials of excellent properties conjugated with organic compound as ligands to construct, conductive and magnetic materials. The design of POM-containing organic-inorganic hybrids, based on covalently grafting various organic functionalities onto POMs, has been an important synthetic strategy towards the development of POM-containing advanced functional materials.In this paper, two new photosensitive polyoxometalate (POM) organic-inorganic hybrid compounds have been prepared by covalently tethering coumarin moieties onto the different POMs. These compounds have been fully characterized by UV-Vis, FT-IR, NMR, ESI-MS and Elementary Analysis. The two organic-inorganic hybrid compounds can undergo reversible light-driven polymerization and this process has been characterized in details. The photo-irradiation process has been characterized in solution by UV-Vis,1H NMR,2D COSY NMR spectroscopy, DLS, GPC and XPS measurements.On the basis of the above-mentioned research, the changes in color of the solution and film samples of the two compounds provide further evidences for a reversible light-modulated process resulting from dimer-and polymerization.