Thiazolo[5,4-d]thiazoles – promising building blocks in the synthesis of semiconductors for plastic electronics

The thiazolo[5,4-d]thiazole fused (bi)heterocycle is an electron deficient system with high oxidative stability and a rigid planar structure, enabling efficient intermolecular π–π overlap. The parent thiazolo[5,4-d]thiazole moiety hence already possesses some appealing features towards applications in organic electronics. Moreover, aryl-functionalized thiazolo[5,4-d]thiazole derivatives – expanding the conjugated backbone of the semiconducting material – are easily prepared. Surprisingly, interest in thiazolo[5,4-d]thiazole-based materials has been rather low, until quite recently, when the high potential of these molecules was widely recognized, notably in the field of organic photovoltaics. Despite the almost exponential growth of activity, the synthetic chemistry behind these molecules has only been explored to a minor extent and there is plenty of room for improvement and broadening of the material scope. In this review, an overview of the currently available synthetic methods and the range of materials prepared to date, together with their basic material properties and main applications, is provided, with the aim to facilitate and stimulate further progress in thiazolo[5,4-d]thiazole-based materials science.