A versatile synthetic approach to design tailor-made push-pull chromophores with intriguing and tunable photophysical signatures

Abstract

Novel modified Biellmann BODIPYs were prepared using a C-H arylation reaction with in-situ formed aryldiazonium salts. The post-functionalization of the methylthio group of these derivatives was demonstrated in SNAr and the Liebeskind-Srogl cross-coupling reactions. The series of compounds herein designed with specific and selective functionalization featuring electron donor and acceptor groups provides valuable information about the impact of the molecular structure and stereoelectronic properties of the substituent on the photophysical signatures of BODIYs. In fact, push-pull dyes showing unexpected high fluorescence response towards the red edge of the visible spectrum can be designed, or, alternatively, chromophores ongoing the expected intramolecular charge transfer states (dark or fluorescent depending on the substituent, the attachment position and the surrounding media) can be also attained owing to the characteristic high charge separation of this king of dyes. We envisage that the reactivity of the selected scaffold as well as the guidelines derived from the computationally-aided spectroscopy study of these luminophores pave the way to the development of tailor made BODIPYs with specific and finely modulable spectroscopic and optical properties.