Charge‐Transfer Exciton Flows: Red Luminescent Zn ₈ D ₁₄ A ₄ Nanotubes

Abstract

ABSTRACT Precise arrangement of multi‐electron‐donor (D) and acceptor (A) molecules can drive directional flows of photo‐generated molecular excitons and charge‐transfer (CT) excitons along with the proper D–A sequence. Here, a highly D–A‐accumulated (14D + 4A) non‐statistical triple‐wall nanotube [(Zn 2+ ) 8 ( L D ) 14 ( L A ) 4 ] driven by linkages with eight zinc ions (Zn 2+ ) is fabricated ( L D and L A are anthracene‐ and anthraquinone‐based ditopic ligands, respectively). The absolute D and A positions are successfully determined by x‐ray diffraction analysis on a single crystal of (Zn 2+ ) 8 ( L D ) 14 ( L A ) 4 , realizing their nanotubular arrangements with a non‐statistical D–A sequence. The four L A ligands are located at the inner positions of the nanotube and undergo CT interactions with the outer four L D ligands, and the other 10 L D ligands form dimers [( L D ) 2 ] through π‐stacking or excitonic interactions between the anthracene rings. The intra‐tube L D / L A CT interactions produce a CT absorption band at long wavelength, enabling the (Zn 2+ ) 8 ( L D ) 14 ( L A ) 4 nanotube to absorb long‐wavelength green light through CT excitation ( L D / L A + h ν (CT) → L D •+ / L A •– ). Long‐wavelength light excitation provides a bright red excimer emission from the anthracene dimer units [( L D ) 2 * ]. This is most probably arising from flows of the low‐energy photon‐generated CT excitons.