Uranyl complexes photochemistry

Exclted states, primary processes Lanthanides, electronic structure Lanthanides, excited states Lanthanides, photochemistry Actinides, electronic structure ActlnldCs, excited states Uranyl ion, photochemistry Uranyl complexes, photochemistry Uranyl Ion, luminescence quenching Photochemistry, actinide alkyls... 

ESR spectra, 511 Uranium(VI) complexes dioxoneocupferron, 512 Uranium hexaalkoxides physical properties, 347 Uranyl complexes cupferron, 512 formamide, 491 glycolic acid, 472 hexafluoroacetylacetone, 373, 377 photochemistry, 385 rearrangement, 384 maleic acid conformation, 467 neutral 1,3-diketones, 402 poly ketones, 399 Urea... 

A large number of other metal complexes have received long and detailed attention, but activity in recent years has revealed few new principles appropriate for discussion here and some systems have been treated in detail elsewhere.2 Included among these are oxalato complex photochemistry where oxidation of the oxalato ligands is coupled to the central metal reduction Ag(I) photochemistry related to imaging systems uranyl ion photochemical reactions coupled to organic oxidations and aquo ion photoredox reactions. Two specific topics have recently emerged as... 

The most intensive studies of the photolysis of uranyl complexes of carboxylic acids have been conducted on the uranyl-oxalic acid system, particularly because of its use as a chemical actinometer. The overall photochemistry occuring in the uranyl oxalate actinometer solution is summarized by the following equations ... 

During the last ten years, studies of luminescence and photochemistry of polypyridyl Ru(II), Rh(III) and Co(III) complexes, porphyrins and uranyl salts, in the presence of biological macromolecules such as DNA, have been the focus of increasing research work. The interest in such coordination compounds stems from their easily tunable properties. Not only their size and shape but also their... 

The characterization and utilization of photochemical processes are rapidly developing into one of the major areas of activity in modern inorganic and physical chemistry. In the past, the photochemistry of classical metal coordination complexes has received the greatest amount of attention, but recently the photochemistry of organometallic compounds has attracted notice In particular, the photochemistry and photophysics of uranyl compounds have been investigated for more than four decades and a great deal has been learned about the primary photoprocesses and the photo-induced reaction mechanisms displayed by these complexes (.3,4). The popularity of uranyl compounds in photochemical studies is derived from their ready availability and stability, their facile redox chemistry and photosensitivity and their rich excited state chemistry. Since current reviews of uranyl photochemistry are expected to appear in the near future, vide infra, further discussion of this topic here will be limited. 

Knowledge of actinide photochemistry is limited mainly to the complexes of uranium, especially those containing the uranyl ion, The lowest excited state of this ion is... 

These reaction products can be explained on the basis of the pathway shown in Scheme 8.4. This pathway involves an initial photoinduced one-electron transfer in a uranyl formate complex to give UO2 and a formate radical, followed by disproportionation to give and carbon dioxide. The photochemistry of the uranyl ion with either acetic acid or its higher homologues follows a similar type redox pathway. Such a pathway with acetic acid leads to the formation of carbon dioxide, ethane, and carbon dioxide ... 

In all of the photochemistry of UO2 , the nature of the bimolecular product formed by association of the reactant with the excited state U02 is an important facet of the chemistry. In aqueous solution the uranyl ion exists as the hydrate, U02(H20)5, where the five water molecules are complexed in the equatorial plane. Replacement of one or more of these complexed water molecules by an incoming substrate allows for bimolecular photoreaction to occur in the vicinity of the metal center. The reaction types can be summarized by the series of reactions shown in Scheme 8.5, where the radical pair can undergo dissociation, or either forward or back electron transfer reactions. Since the potentials for the (U02 /U02) and the (UOj/U ) couples are 0.06 V and 0.55 V, respectively, the UO2 ion can either be readily oxidized back to UOi, or it can act as a one-electron oxidant to a substrate that reacts as a reducing agent. By observing the reactions... 

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