The colourless crystals of (PPh ) [PW O ]⋅3 C H NO (1) are converted to the dark blue crystals of {(PPh ) [PW O ]⋅3C H NO} {(PPh ) (C H NO) [PW W O ] ⋅2C H NO)} (2) upon irradiation with visible light in an interesting single crystal to single crystal transformation. This photochromic conversion is accompanied by the reduction of concerned Keggin anion from {PW } to {PW W }. This redox conversion is characterized by various spectroscopic techniques including single crystal X-ray diffraction studies. The photochromic properties of compound 1 can be controlled reversibly through the dimethylformamide (DMF) molecule as a function of temperature and proton exposure in a gas-solid reaction. The present work can be described as a new concept of programmable photochromism with the formation of photochromic pockets in crystalline 1 host (solid state), wherein a solvent can be plugged at a time to show light induced coloration.
When the yellow rhombhohedral crystals of Keplerate [Mo72Fe30O252(CH3COO)12{Mo2O7(H2O)}2{H2Mo2O8(H2O)}(H2O)91]·150H2O (1), on wetting with N,N-dimethylformamide (DMF), are irradiated with sunlight, it show remarkable reversible solid state photochromic behaviour with the formation of...
The suspension of an yellow polycrystalline compound [PPh4]3[PMoVI12O40] in N-methylformanilide (NMF) (in which it is not soluble), on irradiation with sunlight, initiates its dissolution via its reduction followed by its...
Polyoxometalate (POM) clusters, mostly anionic, are constituted of early transition metal elements in their highest oxidation states. They have been developed into an important class of inorganic materials opening new frontiers of chemical research that can readily be explored. Their ability to accept one or more electrons to generate mixed valence colored species (heteropoly blues or heteropoly browns), with structural stability under redox conditions makes them suitable to be utilized as the photochromic, electrochromic or thermochromic materials. In the recent years, the photochromic polyoxometalates have received significant importance for their applications as optical storage devices, photoelectric display, sensors, high density memory devices among their many other technological applications. Keggin, [ZM12O40]n-contains twelve M(VI) atoms each of which can undergo reduction from M(VI) to M(V) reversibily. The reduction of the Keggin moiety can be initiated electrolytically or photochemically in presence of a solvent or with a suitable reducing agent. We have synthesized [P(R1)(R2)3][ZM12O40]-type (M = Mo, W; R1 = Me, Ph; R2 = Ph; Z = P, Si) materials which undergo photo induced charge transfer coupled with remarkable colour changes which proceed in a single crystal to single crystal (SCSC) manner. In this poster we wish to present the photoinduced crystallization of reduced Keggin Polyanions.
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