Halogen-regulated intramolecular through-space conjugated emission and room temperature phosphorescence of halogenated cyclooctatetrathiophene

Abstract

Developing non-planar molecules with intramolecular through-space conjugation (ITSC) and room temperature phosphorescence is of significant importance for understanding the properties and functions of new photochromic molecules. In this work, a series of novel saddle-shaped halogenated cyclooctatetrathiophenes (COTh-mXs, m = 1, 2, 3, 4; X = F, Cl, Br, I) were successfully synthesized. Crystal structure analysis confirms that halogen substitution can significantly alter the average distance between the double bonds of two para-thiophene (D_TSC) and the angle between the p-orbitals of two para-thiophene (θ_TSC) of COTh with multiple intermolecular interactions, which endow COTh-mXs with superior ITSC luminescence and significantly modulate the room temperature phosphorescence (RTP) behaviors based on the halogenation manners. This work provides a new perspective for designing molecular systems that possess both ITSC and RTP.