Homogeneous and Heterogeneous Self‐Assembly of Luminescent Pyromellitic Dianhydride‐Based Charge‐Transfer Complexes

Using easily hydrolyzable brominated pyromellitic dianhydride (PMDA) as an electron acceptor, a wide variety of structurally stable binary organic charge‐transfer (CT) microcrystals that are stabilized by dominant intermolecular CT interactions is achieved. By varying the electron‐donating abilities of π‐electron compounds, the resulting single crystalline CT assemblies display tailorable fluorescence emissions spanning from green to near‐infrared. Upon implantation of a π‐electron donor anthracene (An) into fluoranthene‐PMDA (Fl‐PMDA), red and NIR emissions of ternary alloyed assemblies are substantially enhanced due to efficient energy transfer from Fl‐PMDA to An‐PMDA as well as structural complementarity between two CT complexes. Depending on the well‐matched epitaxial relationship, seeded growth of phenanthrene‐PMDA (Ph‐PMDA) onto the pre‐existing An‐PMDA microcrystals is also achieved, leading to core‐shell heterostructures with full and partial coverage. Such an epitaxial growth strategy is also applicable to the construction of microscale heterostructures of diverse CT complex combinations. The ternary Fl1−xAnx‐PMDA alloyed assemblies display composition‐dependent tailorable optical waveguiding behaviors. While An‐PMDA@Ph‐PMDA core‐shell microrods present wavelength‐dependent two‐photon excited fluorescence performances. The rational creation of these homogeneous and heterogeneous CT‐assembled architectures provides us a deep insight to investigate multicomponent functional organic cocrystals. By constructing a variety of luminescent charge‐transfer (CT) cocrystals applying brominated pyromellitic dianhydride (PMDA) as an π‐electron acceptor, homogeneous and heterogeneous assemblies based on these PMDA‐based CT complexes are both achieved, giving rise to alloyed and heterostructured microcrystals. Ternary alloyed CT microcrystals display composition‐dependent optical waveguiding abilities, while An‐PMDA@Ph‐PMDA core‐shell microrods present wavelength‐dependent two‐photon excited fluorescence performances.