Charge-transfer complexes solvent photochemistry

Addition has also been shown to occur when the pyridinlum iodide (139) is irradiated. The product Is assigned the structure (140) and the relevance of this reaction to the photoreactivity of Kosower solvent polarity probes has been discussed. The use of osmium tetroxide to hydroxylate alkenes is a well known procedure which is often carried out in aromatic solvents. These arene solvents form charge transfer complexes with the osmium tetroxide and the photochemistry of these has now been examined. It is shown that with benzene and alkyl benzenes isolable adducts are formed that from benzene Is assigned structure (141). 

Mo(CN)8] solutions deal with the quantum yield of the primary photoaquation reaction.The photoaquation and photoredox processes in the photochemistry of [Mo(CN)8] have been succinctly contrasted in a paper whose main discussion is concerned with the solvated electrons formed during irradiation of aqueous solutions containing this complex ion at intemaJ-charge-transfer and charge-transfer-to-solvent frequencies. ... 

A number of studies have appeared dealing with the effect of solvent viscosity upon the charge-transfer-to-metal (CTTM) excitation of cobalt(m) complexes. " Irradiation of [Co(NH3)5X] + ions (X = Cl, Br, N3, or NCS) at 400 nm > A 214 nm indicates that the solvent plays a more active role in CTTM photochemistry of transition-metal complexes than previously suspected. Photolysis of [Co(NH3)6X] + ions (X = NOj or Ns) in polymer solutions indicates that the... 

Photochemistry of cis-[Co(en)2(N02)2] in neat acetonitrile differs from that in water. In aqueous solution excitation of the complex ion in the ligand-to-metal charge transfer band gives the cobalt(II) ion and the nitrito linkage isomer. In acetonitrile, an intermediate cobalt(II) complex coordinated to NO2 is produced. As previous studies have shown, the solvent employed has a marked effect on the reactivity pattern of excited states. The viscosity dependence of the photoaquation of [Co(CN)j " and a variety of Cr(III) complexes has been studied using glycerol-water mixtures. " Cage effects are not important in the photosubstitution of CN in the systems studied. 

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