Internal energy, charge transfer process

Z polarity scale. A solvent polarity scale proposed by Koso ver [Kosower 1958a, 1958b] based on the energy of the electronic transition of the 1 -ethyl-4-carbomethoxypyridinium iodide that is strongly solvent-dependent. This is a measure of an internal charge transfer process. The original set of Z values being quite small, it was successively extended by means of other indicators (Table L2). 

A special discussion is needed of the influence of internal energy on the charge-transfer process... 

Stoicescu and Dimonie103 studied the polymerization of 2-vinylfuran with iodine in methylene chloride between 20 and 50 °C. The time-conversion curves were not analysed for internal orders but external orders with respect to catalyst and monomer were both unity. Together with an overall activation energy of 2.5 kcal/mole for the polymerization process, these were the only data obtained. Observations about the low DP s of the products, their dark colour, their lack of bound iodine and the presence of furan rings in the oligomers, inferred by infrared spectra (not reported), completed the experimental evidence. The authors proposed a linear, vinylic structure for the polymer, and a true cationic mechanism for its formation and discussed the occurrence of an initial charge-transfer complex on the... 

In addition to the processes just discussed that yield vibrationally and rotationally excited diatomic ions in the ground electronic state, vibrational and rotational excitations also accompany direct electronic excitation (see Section II.B.2.a) of diatomic ions as well as charge-transfer excitation of these species (see Section IV.A.l). Furthermore, direct vibrational excitation of ions and molecules can take place via charge transfer in symmetric ion molecule collisions, as the translational-to-internal-energy conversion is a sensitive function of energy defects and vibrational overlaps of the individual reactant systems.312-314... 

Figure 1. JabJonski-type diagram of the lowest energy levels of electron donor-acceptor molecules formally linked by a single bond which show dual fluorescence phenomenon. D-A, (D A), (D+-A ), (D -A ) and (D-A) denote the ground state, the primary excited and charge-transfer (CT) singlet states, and CT and locally excited triplet states, respectively. The arrows correspond to the radiative (absorption, A, fluorescence, F, and phosphorescence, Ph) and the radiationless (internal conversion, IC, and intersystem crossing, ISC) processes.

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