Star‐Shaped Macromolecules with the Core of Hexakis‐(fluoren‐2‐yl)benzene and the Periphery of Pyridine: Synthesis and Application as Solution‐Processable Electron‐Transport Materials

Abstract

Three new star-shaped macromolecules with hexakis(fluoren-2-yl)benzene as the core and pyridine as the periphery (2Py-HFB, 3Py-HFB, and 4Py-HFB) are synthesized and characterized. The synthetic conditions of octacarbonyldicobat-catalyzed cycloaddition reaction for different alkyne precursors are investigated. The coordination interaction between the pyridine ring of alkyne precursor and the cobalt catalyst may result in very low yield of the cyclotrimerization product. However, with the increase of the catalyst loading, the yields of the intermediates of cyclopentadienone are enhanced. Then, the desired cyclotrimerization products can be obtained by the Diels-Alder reactions of cyclopentadienone with acetylene in good yield. These new compounds exhibit good thermal stability and favorable electron affinity. By using the new compounds as electron-transporting materials, all-solution-processed phosphorescent organic light-emitting devices (OLEDs) show good performance with a maximum current efficiency of 5.6 cd A(-1) and maximum external quantum efficiency of 4.68%.

Hexaarylbenzene: Evolution of Properties and Applications of Multitalented Scaffold

“…In a continuation of this work, recently Yang and co-workers reported three fluorene-based, star-shaped HAB derivatives 32 a–c (Figure ) bearing very good electron-transporting pyridyl groups at the periphery. All three derivatives showed good thermal stability and high electron affinity.…”

An overview on synthetic strategies for the construction of star-shaped molecules

“…Abdelhamid et al 94 reported the synthesis of poly(2,6dimethyl-4-phenyl-1,4-dihydropyridinyl)arenes 159a, 159b, 161a, 161b, 163a and 163b in good yields through reaction of tris-, tetrakis-, and hexakis(formylphenoxy methyl)benzenes 157a, 157b, 160a, 160b, 162a and 162b, respectively, with 3aminobut-2-enenitrile 158 in acetic acid at reux (Schemes 39-41). 97 Yin et al 98 reported the synthesis of star-shaped macromolecules 186a-c with hexakis(uoren-2-yl)benzene as the core and pyridine as the periphery. The synthetic strategy includes octacarbonyldicobalt-catalyzed cycloaddition reaction for different alkyne precursors 184a-c.…”

Recent development of pyridine based charge transporting materials for organic light-emitting diodes and perovskite solar cells

“…Three pyridine substituted star shaped ETMs 55–57 were reported by Yang et al for application in OLEDs as a solution processed electron transporter. 85 The ETMs 55–57 were synthesized via Diels–Alder reactions of cyclopentadienone with the acetylene unit to get the final compounds through cyclotrimerization. The UV-Visible absorption spectra for compounds 55–57 shows a strong absorption band at 330 nm, which could be instigated from the collective π–π* transition of the fluorene units.…”