Luminescent dyes, chemical structures

Table 13-2. Chemical structures of representative small molecule transport materials ami luminescent dyes.

We found that one of the crystal polymorphs of terpyridine (3) showed bright blue luminescence, while the other was non-luminescent. The results clearly indicate that the on- and off-states of the luminescence are controlled by the specific mode of molecular packing, and reproducible on-off switching of the luminescence is realised by heat-mode interconversion between two crystal polymorphs. Until recently, routine methods for tuning the luminescent properties of dye moleeules were mostly limited to modification or alteration of their chemical structures. 

The organic dyes used for lasers can be classified on the basis of molecular structure terphe-nyls (spectral range 312-400 nm) coumarines (420 - 580nm) rhodamines (570-720 nm), oxa-zines (680-860 nm). Each class consists of several dyes with slightly modified chemical structure and, hence, slightly shifted absorption and luminescence bands. There are special dyes for UV and near IR. 

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