Noncovalently Netted, Photoconductive Sheets with Extremely High Carrier Mobility and Conduction Anisotropy from Triphenylene-Fused Metal Trigon Conjugates

Abstract

Supramolecular assembly of small molecules via noncovalent interaction is useful for bottom-up construction of well-defined macroscopic structures. This approach is attracting increasing interest due to its high potential in manufacturing novel molecular electronic and optoelectronic devices. This Article describes the synthesis and functions of a sheet-shaped assembly from novel triphenylene-fused metal trigon conjugates. These conjugates were recently designed and synthesized by a divergent method and used for the supramolecular self-assembly of sheet-like objects. In contrast to triphenylene, which absorbs photons in ultraviolet region, the triphenylene-fused metal trigon conjugate shows a strong absorption band in the visible region. The metal trigon conjugate emits green photoluminescence with significantly enhanced quantum yield and allows intramolecular energy migration, as a result of extended π-conjugation over metal sites. It assembles via physical gelation to form noncovalent sheets that collect a wide wavelength range of photons from ultraviolet to visible regions. The noncovalent sheets allow exciton migration and are semiconducting with an extremely large intrinsic carrier mobility of 3.3 cm² V⁻¹ s⁻¹. They are highly photoconductive, produce photocurrent with a quick response to light irradiation, and are capable of repetitive on−off switching. Moreover, these sheets facilitate a conduction path perpendicular to the sheet plane, thus exhibiting a spatially distinctive anisotropy in conduction. The noncovalent sheet assemblies with these unique characteristics are important for molecular optoelectronic devices based on solution-processed soft materials.