Supramolecular Engineering of Non-planar Bridged-Ethers: Blue to Red Emission Tuning and Solution-Processed OLED Fabrication

Abstract

There is an exigent demand of establishing a systematic strategy of supramolecular engineering to embrace an extraordinary tuning of desired emissions from the functional fluorescent organic materials. Simultaneous emission modulation in solids, aggregates, solvents, and viscous media is highly onerous with several photophysical pitfalls therewithal. 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 could be altered by reducing or expanding the heterocycle. Further, alterations to the present heteroatom result in various molecular packing patterns, including H, herringbone-H*, X, and charge-transfer (CT)-mediated J-type. Nevertheless, 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 the 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. However, a noncytotoxic orange-red emitting fluorophore was applied in a solution-processed yellow OLED (organic light emitting device) device fabrication to realize its further utility