Polyhalogenated 2,1,3‐Benzochalcogenadiazoles: A Small‐Molecule Platform for Multicentered Spin–Orbit Coupling Affecting Optical Properties (Chalcogens = S, Se, Te; Halogens = F, Cl, Br, I)

2,1,3‐Benzochalcogenadiazoles and their halogen derivatives (chalcogen = S, Se, Te; halogen = F, Cl, Br, I) are widely employed in organic optoelectronics as chromophoric/fluorophoric electron‐acceptor building blocks. In this work they are specified as an advantageous small‐molecule platform for multicentered (Se, Te; Cl, Br, I) spin–orbit coupling (SOC) affecting optical properties of π‐organics. Electronic absorption and emission/photoluminescence spectra of 4,7‐di‐ and 4,5,6,7‐tetrahalogenated 2,1,3‐benzochalcogenadiazoles E / X’ and E / X , respectively ( E = chalcogen, X = halogen), have been studied in solid‐state and THF solutions experimentally and theoretically. It has been found that the nature of E is the key factor controlling the photophysical properties of E / X’ and E / X , such as energy levels, Stokes shifts, and the photoluminescence quantum yields, while X serves for further fine tuning of the properties. Combined E and X variation allows target‐oriented design of absorptive and emissive materials for metal‐free SOC‐controlled optoelectronics and emerging spin–orbitronics.