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.