Dopants, intramolecular charge transfer

Four compounds (1 to 4) were utilized for the intramolecular charge transfer dopants (see Scheme 2). Their synthesis is described elsewhere [59], They were chosen for the following reasons ... 

Figure 9 Diffraction efficiency of photorefractive grating in the composite systems. Note that high diffraction efficiency for the composites containing the intramolecular charge transfer dopants 3 and 4 occurs at lower applied voltages than those for the intermolecular charge transfer dopants.

Photoinduced electron transfer occurs through excitation of the 400-nm absorption bands of the donor chromophores based on the aminonapthalene-dicarboximide derivatives. The tails of the dopants absorption bands extend to at least 500 nm, which allows for the use of an Ar+ laser. Figure 8 illustrates the ground-state absorption spectra of the donor and acceptor for both the intramolecular and intermolecular charge transfer dopants in toluene. The spectra are similar for all of the dopants, with the exception of 2, which has a 50-nm red-shifted absorption band. The inset illustrates the broadened spectra in the liquid crystalline environment. The extinction coefficient at 457 nm varies from approximately 1000 M-1 cm-1 for 4, 2000 M-1 cm-1 for 1, 5000 M-1 cm-1 for 3, and 10,000 M-1 cm-1 for 2. 

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