Photochemistry electronic spectra

Several reasons were proposed to explain the cleaner chemistry. First, the electrostatic fields (0.3 and 0.9 V for Na-Y and Ba-Y, respectively) in the zeolite stabilize the hydrocarbon-02 charge transfer, thereby shifting the transition to visible wavelengths. Second, the use of visible excitation suppresses the secondary photochemistry rampant with UV light. Third, the steric constraints imposed by the zeolite promote product selectivity. This chemistry can be demonstrated by the reaction of 2,3-dimethyl-2-butene (DMB). Figure 26a shows the electronic spectrum... 

The spectroscopy and photochemistry of the [Co(CN)6] ion have been studied extensively and have been reviewed. Bands at 312, 260 and 202 nm in the electronic spectrum of aqueous solutions are assigned to the Tig, Tig and CT transitions respectively, and similar spectro-... 

The majority of photochemistry of course deals with nondegenerate states, and here vibronic coupling effects aie also found. A classic example of non-Jahn-Teller vibronic coupling is found in the photoelection spectrum of butatiiene, formed by ejection of electrons from the electronic eigenfunctions [approximately the molecular orbitals). Bands due to the ground and first... 

The photochemistry of phthalimide systems was thoroughly investigated by many groups over the last two decades. This chromophore shows a broad spectrum of reactivity leading mainly to cycloaddition and photoreduction products by either intermolecular or intramolecular processes. In the presence of electron donors, the electronically excited phthalimide could also undergo electron transfer and act as an electron acceptor. 

The ferrocyanide ion, stable at neutral pH, shows well understood optical transitions in the visible and near u.v. It carries four negative charges, which should facilitate solvated electron formation. A survey of its known photochemistry indicated that at neutral pH we may hope that solvated electron formation will be the only photochemical primary process. Indeed, after we commenced the work, Matheson, Mulac, and Rabani (31) found on flash photolysis the absorption spectrum of e aq in aqueous solutions of ferrocyanide. 

Mesitylfhjorenyl anion (9MsF ) is unreactive towards Mel at temperatures below —78 °C.100 Above —60 °C the absorption spectrum of 9MsF in the presence of Mel is replaced by that of the corresponding 9-mesitylfluorenyl radical (9MsF), and 9-methyl-9-mesitylfluorene is formed in low yield, hi a study of the electron-transfer photochemistry of chrysanthemol, an intramolecular S 2 reaction of a vinylcycloprop-ane radical cation has been observed.101 hi a long series of studies of the reactivity of the acids of trivalent phosphorus and their derivatives, the behaviour of P—O nucleophiles towards arylmethyl bromide systems has been examined.102 Further evidence for an X-philic substitution/SET tandem mechanism has been obtained. 

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