CIDEP Studies

Maeda K, Terazima M, Azumi T and Tanimoto Y 1991 CIDNP and CIDEP studies on intramolecular hydrogen abstraction reaction of polymethylene-linked xanthone and xanthene. Determination of the... 

Jeevarajan, A. S., M. Khaled et al. (1993a). CIDEP studies of carotenoid radical cations. Z. Phys. Chem. 182 51-61. 

It is not surprising to us that the current CIDEP study was not able to pinpoint the role of the excited singlet reaction. Nevertheless, the results of the solid state experiments at 77 K discussed earlier support the recent CIDNP product analysis of similar lignin model reactions which strongly indicate a primary direct 0-cleavage reaction from the excited singlet state (9,11-12). 

In a systematic ESR and CIDEP study of various alkoxy substituted phenols by photochemical reactions with ketones and with organic peroxides, we have shown (15) that molecular oxygen is not the active radical reactant in the oxidation. Rather, molecular oxygen is necessary to produce peroxy and alkoxy radicals, ROO and RO-which then add onto the phenyl ring to initiate the oxidation processes. The precursor radical R - can be derived from as many ways as one can imagine, both via photo and thermal reactions. 

CIDEP studies indicated that photo-ejection reactions probably occurred from triplet anions33. Oxidation potentials (—0.29 to —0.90 V, versus SCE)113 confirmed the electron-donor properties of the anions. 

T has to be obtained from independent experiments the obvious choice would be to take the value from the time-resolved CIDEP study. However, if T values are not available, we do not need to know the absolute value of V in those experiments where one is measuring relatives kq s of a particular triplet molecule reacting with a number of different substrates (49) as long as the same radical, derived from the same parent triplet state, is being monitored. 

Wong and Wan (136a) have suggested application of photo-CIDEP to the ISC study of triplet benzophenone. They pointed out that while PMDR methods normally study the dynamics of the ISC is zero field and in solid state, the photo-CIDEP study is potentially useful to estimate the intersystem crossing relative rates at a constant external magnetic field and in the liquid state. 

If the original semiquinone radical QH is polarized, the semi-quinone radical anion derived from eq. 52 can be expected to retain much of the initial polarization. Thus in the CIDEP studies of the photoreduct ion of quinones in triethylamine solution, the primary photochemical process was thought to involve the possible exciplexes (42) ... 

CIDEP and CIDNP in Metal and Metallorganic Systems. To date, very few CIDEP studies of metal systems have been reported (139). These included the earlier study of rubidium and cesium systems... 

A CIDEP study of the photooxidation of a range of phenols by benzophenone has concluded that the reaction proceeds by abstraction of a hydrogen atom to give the corresponding phenoxyi radicals . Others have reported that aromatic ketones such as 3-methoxyacetophenone and 2-acetonaphthone mediate efficiently the photooxidative degradation of phenols by a one-electron process producing the radical cations of the phenols in aerated aqueous solution. A possible reaction sequence is shown in equation 1. 

A time resolved CIDEP study of radical pair systems derived by electron-transfer photooxidation of carbazole derivatives using maleic anhydride has revealed that the singlet state of the radical ion-pair has an energy which is greater than that of the triplet state. From this evidence the conclusion is drawn that the sign of the apparent exchange interaction is positive. 

CIDNP and CIDEP Studies.—Two mechanisms have been proposed to account for the observation of electron spin polarization in radical reactions (CIDEP), the first being termed the radical pair mechanism, in which the polarization results from the mixing of the singlet and triplet states of the radical pair by the magnetic interactions within the radicals, and the second the triplet mechanism, in which the polarization originates in the triplet as a result of spin-selective intersystem crossing from the photoexcited singlet state, as is known to occur in several systems from ODMR measurements (see above). It has recently been pointed out 480 that, for the latter mechanism, unequal population of the triplet sub-levels will depend upon zero-field D and E terms and Zeeman terms, but also... 

INDO calculations of spin densities. ) CIDEP study. ... 

Flash photolysis EPR and CIDEP studies of corresp. radicals derived from methylpyrazines. ... 

MINDO/3 calculations. miYio calculations. ) CIDEP study. ) Temperature dependence studied out of plane vibration Frequency 380 cm". ) INDO calculations. ... 

Temperature dependence of proton hfs and protic solvents effect on H(jS, OH) studied. Ab initio calculation. CIDEP study. 

Time resolved CIDEP study. 38) CIDNP study. ... 

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