Correlating the Structural and Photophysical Properties of Ortho, Meta, and Para‐Carboranyl–Anthracene Dyads

Adam V Marsh,Paul N Stavrinou,Matthew J Dyson,Nathan J Cheetham,Iain Mcculloch,Matthew Bidwell,Colin N Warriner,Martin Heeney,Mark Little,Stefan C J Meskers,Andrew J P White,Anthony C Swain

doi:10.1002/aelm.202000312

Abstract

AbstractThe role of the carborane isomer is investigated on the structural and photophysical properties of molecules comprising a carborane cluster and a conjugated organic moiety is investigated by synthesizing isomeric o‐, m‐, and p‐carboranyl‐anthracene donor–acceptor dyads. While appending a carborane leads to emission from a low energy intramolecular charge transfer state for the o‐isomer, as well as emission from an excited state localized on the anthracene, this is not the case for the m‐ and p‐carborane derivatives. This difference is attributed to a lower electron affinity for the latter two isomers. However, adding both m‐ and p‐ deforms the aromatic backbone and increases its structural rigidity, reducing non‐radiative decay pathways and hence enhancing photoluminescence quantum efficiency relative to anthracene.

Highlights

The acenes constitute a class of molecular semiconductors the anthracene donor onto the antibonding orbital of the carboranyl carbon-carbon (CC–CC) bond.[8,15,16,17,18,23,24,25] This orbital overlap depends on the molecular geometry and is expected to with remarkable optoelectronic properties such as, for example, be largest with a perpendicular arrangement of the CC–CC bond luminescence, high charge carrier mobilities, and relative to the plane of the donor π-system
Functionalization of the acene at the central coupled to rearrangement of the internal molecular geomcarbon atoms allows further optimization of the desired proper- etry allows for a twisted-intramolecular charge transfer (ICT) (TICT) state.[25,26,27,28,29,30,31,32,33,34,35,36,37,38]
Thermal stability increases on the order o < m < p, allowing for the synthesis of m- and p-carboranes from thermal isomerization of o-carborane[80].[81]

Summary

Introduction

The acenes constitute a class of molecular semiconductors the anthracene donor onto the antibonding orbital of the carboranyl carbon-carbon (CC–CC) bond.[8,15,16,17,18,23,24,25] This orbital overlap depends on the molecular geometry and is expected to with remarkable optoelectronic properties such as, for example, be largest with a perpendicular arrangement of the CC–CC bond (electro-) luminescence, high charge carrier mobilities, and relative to the plane of the donor π-system. We report the functionalization of anthracene with such a molecular geometry depends strongly on the environthree different carborane isomers

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Results

Conclusion