Polar compounds, charge transfer systems

Indeed, the usual fluorescence of the isolated aromatic amines (e.g., N,N-dimethylaniline, DMA) is quenched by excimer formation in compounds I and II. In the process of prolonged irradiation of I and II solutions the emission intensity increases gradually because of the loss of the C = C double bonds in the system due to the polymerization reaction. A polar environment favors the charge transfer and, therefore, the fluorescence quenching of the monomer is drastically decreased, whereas the polymer formation increases. 

The z-polarized charge transfer band is not likely to be seen in high-spin systems, since it will now lie some 10 kK higher in energy and will probably be blotted out by the Soret band. However, some high-spin compounds do have a weak shoulder at about 22 kK (111, 112). 

The Twisted Intramolecular Charge Transfer (TICT) model was put forward by Grabowski and coworkers [2,3,15] to account for the observation that the dual fluorescence of DMABN with its normal band (B band) at around 350 nm and its anomalous one (A band, around 450 nm in medium polar solvents) depends on the conformational freedom of the dimethylamino (DMA) group For compounds like MIN, where the DMA group is more or less fixed to a coplanar conformation with the benzonitrile sceleton, and where the lone pair orbital on the amino nitrogen is nearly parallel to the carbon p-orbitals constituting the benzonitrile 7t-system, only the B band is observed. For the... 

Photosubstitution processes of polynuclear aromatic systems including naphtho- and anthraquinones continues to be explored for various compounds. The change in fluorescence characteristics of 8-anilino-1-naph-thalenesulphonates with substitution and solvent polarity is interpreted in terms of sequential formation of the naphthalene S, excited state and a charge-transfer S] excited state. Irradiation of the systems leads to an inefficient dissociation and the formation of 1-anilinonaphthalenes. Japanese... 

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