We’ve seen a whole range of molecular shapes over the years, from spheres to squares and from spirals and grids. Well, now we’ve also got triangles and they’re not just a gimmick – they are able to harvest light and undergo ultrafast charge separation, thanks to the close proximity of the chromophores within them.
In an article published in the Journal of the American Chemical Society last month, a team of researchers from the University of Würzburg, Germany, describe their synthesis of triangular molecules assembled from perylene diimide units, or PDIs. These highly aromatic systems are well known for their photochemical properties, but it would appear that is not only the electronic structure of these molecules which enhances their photophysical performance, but their spacial arrangements with each other as well.
The stacking of the PDIs in a triangular arrangement actually limits their pi-pi interactions with each other, allowing them to compete as separate chromophores, allowing up to six charge-separated states to exist within the molecule. Furthermore, EPR spectroscopy shows that electronic communication does exist between the three PDI units, as a single unpaired electron is able to be shared by all three.
The research is still in its infancy in regards to how it may be applied in the future, but this presents a new and interesting form of light-harvesting molecule which may find use in solar cell technology or organic electronics, due to its remarkable number of charge separated states. It’s early days, but watch this space!