ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Synthesis and characterization of novel phosphorescent host materials based on triphenylpyridine derivatives

Xu Zhang, Qingqing Ye, Yingtao Fan, Xiaoyu Hu, and Yingzhong Shen

Applied Chemistry Department, School of Material Science and Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, People’s Republic of China

E-mail: yz_shen@nuaa.edu.cn

Received: 19 November 2019  Accepted: 10 January 2020

Abstract:

Three novel phosphorescent host materials, 4′,4‴-(4-phenylpyridine-2,6-diyl)bis(N,N-diphenyl-[1,1′-biphenyl]-4-amine) (P1), 2,6-bis(4′-(naphthalen-1-yl)-[1,1′-biphenyl]-4-yl)-4-phenylpyridine (P2), and 2,6-bis(3′,5′-dimethyl-[1,1′-biphenyl]-4-yl)-4-phenylpyridine (P3), based on triphenylpyridine with a symmetrical molecular conformation were designed and synthesized from 2,6-bis(4-bromophenyl)-4-phenylpyridine (3) reacting with [4-(diphenylamino)phenyl]boronic acid (A1), [4-(naphthalen-1-yl)phenyl]boronic acid (A2), and (3,5-dimethylphenyl)boronic acid (A3) through Suzuki coupling reaction, respectively. The compounds obtained were characterized by elemental analysis, ¹H NMR, and ¹³C NMR spectroscopy. The thermal properties of these materials were studied by thermogravimetric analysis and differential scanning calorimetry measurements, which showed that they exhibited excellent thermal stability with glass transition temperatures over 94 °C. Their photophysical properties were also investigated, and the results indicated that all compounds possessed considerably high triplet energy level greater than 2.6 eV; they also emitted blue fluorescence in different solvents. Finally, the results of the density function theory calculations revealed that the compound P1 showed the well-separated frontier molecular orbital, which indicated that it possessed bipolar carrier transport ability for holes and electrons, whereas the compound P2 and P3 exhibited greater overlap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital.

Keywords: Phosphorescent material; Triphenylpyridine; Glass transition temperatures; Triplet energy level

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-020-01063-y

Chemical Papers 74 (7) 2145–2152 (2020)