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

The 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.