Supramolecular engineering of non-planar bridged-ethers: blue to red emission tuning and solution-processed OLED fabrication

Abstract

There is an exigent demand for establishing a systematic supramolecular engineering strategy to support the extraordinary tuning of desired emission from functional fluorescent organic materials. Simultaneous emission modulation in solids, aggregates, solvents, and viscous media is highly onerous with several associated photophysical pitfalls. The present research has coined a design concept in which bridged oxo/thioethers are conjugated to a highly twisted molecular core, generating multisite nonplanarity within the molecular system. Moreover, the non-covalent interactions and slip-stack angles can be altered by reducing or expanding the heterocycle. Furthermore, alterations to the present heteroatoms result in various molecular packing patterns, including H, herringbone-H*, X, and charge-transfer (CT)-mediated J-type examples. In addition, the fluorophore's polarizability, electronic conjugation, and conformation can be systematically regulated to tune a wide range of emission, from blue to red. Indeed, we achieved a 118-nm emission tuning in solids, 150-nm emission modulation in aggregates, and 100-nm emission alteration in a viscous medium. Moreover, a 99-nm to 150-nm solvatochromic shift was attained for some fluorophores. Different emissions from aggregates and the viscous medium were also detected, and excimer formation was possible for some fluorophores, particularly in aggregates. Also, a noncytotoxic orange-red-emitting fluorophore was applied in solution-processed yellow OLED (organic light-emitting device) fabrication to realize its further utility.