Polarized excited state

Let (Xgr and jXex be the dipole moments of the ground and excited states. Then if iXgr > the less polar excited state is surrounded by a solvation shell... 

Figure 8-7 illustrates schematically the electronic natures of the polar ground state (an ion pair) and the less polar excited state. This is, therefore, a case of p.g. 

Evaluation of the Work Term from Charge Transfer Spectral Data. The intermolecular interaction leading to the precursor complex in Scheme IV is reminiscent of the electron donor-acceptor or EDA complexes formed between electron donors and acceptors (21). The latter is characterized by the presence of a new absorption band in the electronic spectrum. According to the Mulliken charge transfer (CT) theory for weak EDA complexes, the absorption maximum hv rp corresponds to the vertical (Franck-Condon) transition from the neutral ground state to the polar excited state (22). 

Another interesting class of molecules are stilbene derivatives with charge donating groups. These compounds offer the opportunity to explore the role of polar solvation dynamics (dielectric friction) in cis/trans isomerization. Interesting papers on this subject have been published by Waldeck et al. [145] and Rulliere et al. [146]. Other well-studied polar excited state isomerization examples include pinacyanol, l,l -diethyl-4,4 -cyanine, and crystal violet, which have been studied by Sundstrom, Gilbro and their coworkers [148] and Ben-Amotz and Harris [148] and others who are referenced in these papers [148,149],... 

As early as 1964, Corey had suggested the intermediacy of an oriented pi complex in the cycloaddition of enones (43) and soon thereafter Hammond and coworkers, on the basis of arene fluorescence quenching by dienes, suggested the possible involvement of a polar excited state complex with substantial charge transfer character (44). Since then the possibility of cycloadditions occurring through the intervention of exciplex or excimer intermediates per se or as precursors for radical ions pairs, eq. 12,... 

CT complex formation from excited states is a widespread phenomenon and consequently has been very extensively studied. 0 A structure-energy correlation of intramolecular CT state formation in a series of (N,N-diethylanilino) amines indicates that high polar excited states are involved (pg values range between 13.4-... 

Fluorescence spectra of 10 aminoborane analogues of stilbenes and styrenes were interpreted in terms of tt tt emission from a polar excited state to a less polar, more rigidly planar ground state. 

The effect of solvent polarity on interpreted qualitatively Because the highly polar excited states enter into strong interaction with polar solvents, their tendency toward geometric isomerization (which requires complete reorganization of the solvate structure) is naturally very low. Data from Schulte-Frohlinde and co-workers [5] show substantial and different polar solvents, for example, /V./V -dimethylformamide (DMF) or ethanol, photostationary state is correspondingly shifted to the trans side [152], With... 

The specificity of the photohydrolysis allows to rule out a mecheuiism involving an homolytic scission of the C-Cl bond with formation of radicals. A direct photohydrolysis probcibly occurs from a polarized excited state. It is suggested this excited state would be the first triplet state to account for the sensitization and inhibition experiments (19). 

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