Molecules that exhibit efficient phosphorescence at room temperature are valued as the emissive components of a variety of optical technologies, notably organic light emitting diodes (OLEDs). Phosphorescent materials suitable for these applications often contain rare heavy metals such as platinum and iridium that enable efficient intersystem crossing via heavy atom-induced spin orbit coupling. Efforts directed toward metal-free, cost-effective phosphorescent organic molecules is a relatively new area of research. Nonetheless, a common feature of several of the examples reported thus far is the presence of aryl halides (i.e. bromide and iodide) capable of inducing spin orbit coupling to access a molecule’s triplet manifold. This presentation describes a class of metal-free, halogenated benzo[2,1,3]thiadiazoles that exhibit phosphorescence at room temperature in a variety of media, including solution. Unusual and noteworthy features of these materials are their red emission and Stokes shifts well above 200 nm. The preparation of these molecules and their photophysical properties in solution, 77 K glass, and thin films are presented. Studies on the mechanism of phosphorescence by these materials, including structure-property relationships through halide substitution and TD-DFT calculations, are discussed. Lastly, strongly emissive excimers of these species with electron-rich aromatics in amorphous thin films and their electroluminescence in an OLED are presented.

Room-temperature red phosphorescence of structurally simple benzo[2,1,3]thiadiazoles

250th National Meeting (2015)

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