Nanjing University of Posts and Telecommunications, China
Wen Yong Lai is a Full Professor at the Nanjing University of Posts and Telecommunications. He received his PhD from Fudan University in 2007. He then joined the Key Laboratory for Organic Electronics & Information Displays and Institute of Advanced Materials, Nanjing University of Posts & Telecommunications. His research mainly focuses on the design, synthesis and application of organic and polymer optoelectronic materials for organic/plastic electronics. He is also interested in the exploration of novel materials and processes for printed electronics.
A novel set of star-shaped polycyclic aromatic hydrocarbons (PAHs) based on naphthalene-fused truxenes, named as TrNaCn (n=1-4), were synthesized and characterized. Oxidative cyclodehydrogenation was carried out following the microwave-assisted six-fold Suzuki coupling reaction. It is worthwhile to mention that multiple dehydrocyclization samples can be isolated effectively in one reaction, suggesting that the oxidative cyclodehydrogenation was a stepwise ring-closed process. Thermal, optical, and electrochemical properties, and self-assembly behaviors of the resulting oxidized samples were investigated to understand the impact of the ring-fused process on the properties of star-shaped PAHs. Distinct bathochromic shift of the absorption maxima λmax reveals that the molecular conjugation extends with the stepwise ring closed reaction. The optical band gap energy of these PAHs varied significantly with increasing the fused rings, resulting in facile-tunable emissive properties for the resultant star-shaped PAHs. Interestingly, with the generation of perylene analogue rigid arms, TrNaC2 and TrNaC3 showed significant enhancement of photoluminescence quantum yields (PLQYs) in solution (η=0.65 and 0.66, respectively) in comparison with those of TrNa and TrNaC1 (η=0.08 and 0.16, respectively). With strong intermolecular interactions, the precursor TrNa is found to be able to self-assemble into rod-like microcrystals which can be facilely identified by naked eyes, while TrNaC1 self-assembles into nanosheets once the naphthalene rings are fused. This study offers a unique platform to gain further insights and better understanding into the photophysical and self-assembly properties of π-extended star-shaped PAHs.