Researchers from CEISAM (CNRS/Nantes Université) and the Interdisciplinary Center for Nanoscience of Marseille (CINaM, CNRS/Aix-Marseille Université) have developed a new family of cross-shaped organic dyes whose optical properties can be tuned by modifying their molecular architecture.
These original molecules consist of an aromatic core bearing electron-donating and electron-accepting groups along two perpendicular directions. This cross-shaped architecture promotes electronic communication between the different parts of the molecule, allowing its light absorption and emission properties to be controlled.
The researchers prepared a series of dyes displaying particularly interesting electrochemical and photophysical properties. In solution, some of the compounds show intense green or orange fluorescence, with emission lifetimes of up to 20 nanoseconds, which is relatively long for organic dyes.
One of the most remarkable results concerns emission in the near-infrared region, with some of the dyes emitting beyond 750 nm in solution. Even more surprisingly, in the solid state, one of the compounds displays emission extending from 800 to 1400 nm. This region of the electromagnetic spectrum is particularly interesting for many applications, yet organic materials capable of efficiently emitting in the near-infrared in the solid state remain relatively rare.
Beyond their fundamental interest, the properties of these new molecules open up prospects for a range of applications. Their long emission lifetimes could prove useful in photocatalysis, while their near-infrared emission could potentially find applications in fields such as biomedical imaging and optoelectronic devices.
This work, combining organic synthesis, electrochemistry, spectroscopy and theoretical modelling, is published open access in the European Journal of Organic Chemistry and also features on the cover of the issue:
https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/ejoc.70650