Synthesis and electroluminescence properties of carbazole-containing 2,6-naphthalene-based conjugated polymers

Abstract

Three types of carbazole containing 1,5-disubstituted poly(2,6-naphthalene) derivatives, i. e., 2,6-naphthalene homopolymer that has a carbazolyl side chain at 1,5-positions, random copolymers and alternating copolymers consisting of 1,5-dialkoxynaphthalene-2,6-diyl and N-phenylcarbazole-2,7diyl were newly synthesized by Ni-mediated Yamamoto polycondensation and Pd-catalyzed Suzuki coupling reaction. The number-average molecular weights (M n ) of the polymers and their polydispersity indices (M w /M n ) were 5.4-8.2×10 3 and 1.4-1.7, respectively. These polymers exhibited blue photoluminescence in the film states and high fluorescence quantum efficiencies in CHCl 3 (φ fl = 0.70-1.00). The electroluminescence properties of these polymers were investigated by fabricating a PLED device that has a configuration of ITO/PEDOT(PSS)/polymer/CsF/Al. The device fabricated with the random copolymer exhibited highest performances showing a maximum brightness of 8370 cd/m 2 at 13 V and a maximum efficiency of 2.16 cd/A at 7 V. Kanto Chemical, Tokyo Chemical Industry, Aldrich and Nacalai Tesque Inc. N,N-Dimethylformamide (DMF), acetonitrile and tetrahydrofuran (THF) were used after purification by distillation using an appropriate drying reagent such as molecular sieves and Na, respectively, under argon. Other chemicals were used as received without further purification. 5-Bis[6-(carbazol-9-yl)hexyloxy]-2,6-dibromonaphthalene (3) 1,5-Bis[6-(carbazol-9-yl)hexyloxy]-2,6-dibromonaphthalene (3) was synthesized by the modified procedure reported in our previous work. [23] Under an argon atmosphere, a solution of 2,6-dibromo-1,5-dihydroxynaphthalene 1 (0.76 0g, 2.39 mmol), KOH (0.530 g, 9.45 mmol) in EtOH (25 ml) was refluxed for 30 minuets. Afterwards, N-(6-bromohexyl)carbazole 2 (3.20 g, 9.69 mmol) was added to the solution, which was successively refluxed for 24 hours, cooled to room temperature, and dissolved in CH 2 Cl 2 . The organic layer was washed with NaOH aq, water and brine, and was dried over anhyd. 1,Na 2 SO 4 . After removing the solvent, the resultant black residue was chromatographed on silica gel (CH 2 Cl 2 /hexane= 1:1) to afford a yellow solid, which was recrystallized from hexane/CH 2 Cl 2 to obtain pure 3 (0.80 g, yield: 41 %). 1 H NMR (270 MHz, CDCl 3 ) δ = 1.55, 1.65 (m, 8H), 1.91 (m, 8H), 4.01 (t, J = 6.43, 4H), 4.35 (t, J = 7.25, 4H), 7.23 (m, 4H), 7.48 (m, 8H), 7.57 (d, J = 9.06, 2H), 7.65 (d, J = 9.06, N-phenyl-2,7-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolate) carbazole (6a)Under an argon atmosphere, to a solution of N-phenyl-2,7-dibromocarbazole (5a) (0.150 g, 0.399 mmol), PdCl 2 [1,1′-Bis(diphenylphosphino)ferrocene](II) (0.0195 g, 0.0239 mmol), KOAc (0.234 g, 2.39 mmol) in DMF (5 ml) was added bis(pinacolato)diborane (0.223 g, 0.878 mmol), which was refluxed for 24 hours. After cooling to room temperature, CH 2 Cl 2 was added to the solution. The organic layer was washed with water and brine, and was dried over anhyd. Na 2 SO 4 . After evaporation, a black residue was obtained, which was purified by a s...

Characteristics of thermal behavior of photoluminescent copolymers studied by the TG/DTG/FTIR coupled method

“…Naphthalene derivatives are commonly used as a luminescent material due to their intense fluorescence, strong pstacking and good chemical and thermal stabilities [7]. These properties make the naphthalene derivatives very useful precursors for preparation of: fluorophores of luminescent materials [8,9], polymer light-emitting diodes [10,11] and organic semiconductors [12][13][14].…”

Synthesis, characterization and luminescent properties of new copolymers of dimethacrylate derivatives of naphthalene‐2,7‐diol

“…Naphthalene derivatives, due to their unique luminescent properties, have been investigated and used as fluorophores of luminescent materials, [1][2][3] polymer light-emitting diodes, [4,5] photo-voltaic and optical devices, [6][7][8] etc. Polynaphthalenes with different linkages in 1,4-, 1,5-, 2,6-and 2,7-positions have been used as conducting polymers.…”

Synthesis, Characterization, Absorbance, Fluorescence and Non Linear Optical Properties of Some Donor Acceptor Chromophores

“…Because of their high photostability and the elongated molecular shape, carbazole derivatives can be applied as probes in the experimental studies of molecular orientational order in thermotropic and lyotropic liquid crystals, in liquid-crystalline polymers, and in lipid membranes. 3,4 Most of the carbazole derivatives have been considered for applications in organic electronic devices and in optical disks. [5][6][7] They can be also applied as a fluorescent component in liquid crystal displays working in passive or active modes.…”