Carborane-Induced Excimer Emission of Severely Twisted Bis-o-Carboranyl Chrysene.

Adam V Marsh,Nathan J Cheetham,Matthew Dyson,Martin Heeney,Paul N Stavrinou,Colin N Warriner,Anthony C Swain,Andrew J P White,Mark Little,Peter Beavis

doi:10.1002/anie.201805967

Abstract

The synthesis of a highly twisted chrysene derivative incorporating two electron deficient o‐carboranyl groups is reported. The molecule exhibits a complex, excitation‐dependent photoluminescence, including aggregation‐induced emission (AIE) with good quantum efficiency and an exceptionally long singlet excited state lifetime. Through a combination of detailed optical studies and theoretical calculations, the excited state species are identified, including an unusual excimer induced by the presence of o‐carborane. This is the first time that o‐carborane has been shown to induce excimer formation ab initio, as well as the first observation of excimer emission by a chrysene‐based small molecule in solution. Bis‐o‐carboranyl chrysene is thus an initial member of a new family of o‐carboranyl phenacenes exhibiting a novel architecture for highly‐efficient multi‐luminescent fluorophores.

Highlights

At first glance, bulky boron-rich spheroids appear to be an anathema to the two-dimensional, p-conjugated world of organic electronics
To explore whether o-carborane could induce excimer emission ab initio, we focused our attention on chrysene, a non-linear phenacene fluorophore
We proposed that the p–p interactions between the phenyl group of the carborane and chrysene would help to lock the carboranyl CÀC bond perpendicular to the aromatic plane in a geometry favorable for intramolecular charge transfer (ICT), and in doing so create a new class of severely twisted, multi-emissive luminescent materials.[36]

Summary

Introduction

Bulky boron-rich spheroids appear to be an anathema to the two-dimensional, p-conjugated world of organic electronics. This is the first time that o-carborane has been shown to induce excimer formation ab initio, as well as the first observation of excimer emission by a chrysene-based small molecule in solution.

Results

Conclusion