Efficient organic emitters enabled by ultrastrong through-space conjugation

Manipulating the electronic structure of organic functional materials by through-space conjugation (TSC) to achieve desirable photophysical properties has been a long-standing research focus. Although the working mechanisms of TSC have been demonstrated, the roles that the intrinsic molecular skeleton and extrinsic aggregates play remain unclear. Here four trinaphthylmethanol isomers and four trinaphthylmethane (TNM) isomers with varying connecting sites of naphthalene were synthesized, and their photophysical properties were systematically investigated. The strength of TSC was found to rise from 222-TNM to 111-TNM with the increased number of 1-naphthalene units. In particular, 111-TNM was found to support efficient long-wavelength clusteroluminescence with an absolute quantum yield of 55%. Experimental and theoretical results revealed that the inherent attribute of robust intramolecular interactions within individual molecules is fundamental for ultrastrong TSC, and intermolecular interactions play an auxiliary role in fortifying and stabilizing intramolecular interactions. This work reveals the intrinsic and extrinsic factors for manipulating TSC and provides a reliable strategy for constructing non-conjugated luminogens with efficient clusteroluminescence.