Intermolecular Hydrogen-Bond-Assisted Solid-State Dual-Emission Molecules with Mechanical Force-Induced Enhanced Emission

Hydrogen bonds not only play a crucial role in the life sciences but also endow molecules with fantastic physical and chemical properties, which help in the realization of their high-tech applications. This work presents an efficient strategy for achieving highly efficient solid-state dual-emission blue emitters with mechanical force-induced enhanced emission properties via intermolecular hydrogen bonds via novel pyrene-based intermediates, namely, 1,3,6,8-tetrabromo-2,7-dihydroxypyrene (1) and 1,3,6,8-tetrabromo-2-hydroxypyrene (2), prepared via hydroxylation and bromination of pyrene in high yields. Moreover, further use of a classical Pd-catalyzed coupling reaction affords new pyrene-based luminescent materials 3-5, which display high thermal stability (in range of 336-447 °C), blue emission (<463 nm), and high quantum yields in solution. Interestingly, with the monosubstituted hydroxyl (OH) or methoxy (OMe) group located at position 2 of pyrene, compounds 4a and 5 display exciting dual emission with mechanical force-induced enhanced emission properties, due to the presence of several hydrogen-bond interactions. Moreover, this series of compounds exhibits numerous advantages, for example, deeper blue emission with a narrower full width at half-maximum, a stronger steric effect, and higher hydrophilicity. Thus, these novel bromopyrene intermediates and related pyrene-based luminescent materials will pave the way for further exploration of novel organic solid-state luminescent materials for potential application in organic electronics, bioimaging, chemosensors, etc.