Yamamoto Coupling Research Articles

Synthesis, characterization, morphological behaviour, and photo- and electroluminescence of highly blue-emitting fluorene-carbazole copolymers with alkyl side-chains of different lengths

Four novel phenyl-end-capped π-conjugated polymers comprising alkyl chains of different lengths were synthesized: the poly(9,9-dihexyl-2,7-fluorene-alt-9,9-dioctylfluorene) (P0), the alternating fluorene-carbazole copolymers P1 and P2 comprising 20% and 50% of carbazole, respectively, and the homopolymer poly(9-hexyl-9H-carbazole) (P3). The non-end-capped alternating fluorene-carbazole copolymer P4 comprising 20% of carbazole was also synthesized for the sake of comparison with P1. P0-P2 and P4 were synthesized by a Pd-catalyzed Suzuki-Miyaura coupling in good yields (80-89%), while P3 was obtained by a Ni-catalyzed Yamamoto coupling reaction from the 3,6-dibromocarbazole monomer in a moderate yield (52%). P0-P4 polymers were characterized by NMR, elemental analysis, and GPC. The molecular weights are 40.30, 23.42, 14.33, 3.92, and 37.49 kDa, with polydispersity indices of 2.5, 1.7, 1.8, 1.3, and 2.6, for P0, P1, P2, P3, and P4, respectively. These polymers were found to show a high thermal stability, with decomposition temperatures in the range of 395-420 °C, and the glass transition temperature was found to regularly increase with the amount of carbazole inserted in the conjugated backbone. AFM images obtained on thin films (thickness of about 90 nm) of P0-P2 revealed films with surfaces of good quality, being homogeneous with low roughness (0.2 nm for the smaller ones). These polymers were found to be blue-emitting both in diluted dichloromethane and chlorobenzene solutions as well as in thin films and exhibit relatively high values of the absolute quantum yields in the range of 100-5.5% in dichloromethane and 51.4-7.7% in thin films. Blue-emitting electroluminescent devices were obtained with P0 and P1 as emitting layers, respectively. The device built with P1 showed improved performances (EQE of 1.32%) with respect to the one built with the parent polyfluorene material (EQE of 0.75%).

A novel nitrogen rich porous aromatic framework for hydrogen and carbon dioxide storage

A nitrogen rich, p-phenylenediamine based, porous aromatic framework (NPAF) with 1790 m2 g−1 BET surface area has been synthesized by using a Yamamoto coupling technique. The NPAF has shown a hydrogen uptake of 1.87 and 0.33 wt% at 77 K per 1 atm and 298 K per 80 bar, respectively. The CO2 uptake and selectivity of the NPAF at 273 K per 1 atm is 3.64 mmol g−1 and 48, respectively.

Chiral oxazoline substituted optically active poly(m‐phenylene)s: Synthesis and coupling polymerizations of (S)‐4‐benzyl‐2‐(3,5‐dihalidephenyl) oxazoline using transition metal catalysts

AbstractOptically active poly(m‐phenylene)s substituted with chiral oxazoline derivatives have been synthesized by the nickel‐catalyzed Yamamoto coupling reaction of optically active (S)‐4‐benzyl‐2‐(3,5‐dihalidephenyl)oxazoline derivatives (X = Br or I). The structures and chiroptical properties of the polymers were characterized by spectroscopic methods and thermal gravimetric analyses. The polymers showed higher absolute optical specific rotation values than their corresponding monomer, and showed a Cotton effect at transition region of conjugated main chain. The optical activities of the polymers should be attributed to the higher order structure such as helical conformations. Moreover, the helical conformation could be induced by addition of metal salts into polymer solutions. The polymers showed good thermal stabilities, which was attributable to the oxazoline side chains. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

All-Polymer Solar Cells Based on Fully Conjugated Block Copolymers Composed of Poly(3-hexylthiophene) and Poly(naphthalene bisimide) Segments

Fully conjugated donor–acceptor block copolymers composed of poly(3-hexylthiophene) and poly(naphthalene bisimide) segments, P3HT-PNBI-P3HTs, were synthesized using quasi-living Grignard metathesis polymerization and the Yamamoto coupling reaction. Broad absorption in a range of 350–850 nm, which corresponded to the optical band gap of 1.46 eV, was observed for the P3HT-PNBI-P3HT thin films. In addition, the optical band gap decreased to 1.38 eV (the light absorption band extended to 893 nm) by thermal annealing, which was much smaller than those of previously reported donor–acceptor block copolymers (1.6–1.8 eV). The annealed P3HT:P3HT-PNBI-P3HT blend film (1:1 by weight) also exhibited broad absorption in the range of 350–950 nm. Cyclic voltammetry demonstrated that the P3HT-PNBI-P3HT thin films exhibited the oxidation and reduction properties derived from the P3HT and PNBI segments. The HOMO and LUMO levels were in the range of 5.57–5.60 and 4.22–4.27 eV, respectively. All-polymer solar cells using the...

Synthesis and photovoltaic properties of polymeric metal complexes containing 8-hydroxyquinoline as dye sensitizers for dye-sensitized solar cells

Four new donor–acceptor type polymeric metal complexes (P1, P2, P3, and P4) with the same Cd(II) complex in side chain and different conjugated backbone structures were synthesized by Yamamoto coupling and applied in dye-sensitized solar cells (DSSCs) as photosensitizers. The photophysical, electrochemical, and thermal properties were investigated in detail, showing that conjugated backbone containing fluorene improved intramolecular charge transfer and increased generation of photocurrent. The highest power conversion efficiency of 0.56% (J sc = 1.63 mA cm−2, V oc = 0.69 V, FF = 0.50) was obtained with a DSSC based on P3 under simulated air mass 1.5 G solar irradiation, which shows a new strategy to design photosensitizers for DSSCs.

Effects of Molecular Structure on Intramolecular Charge Carrier Transport in Dithieno [3,2-b: -d] Pyrrole-Based Conjugated Copolymers

Intramolecular mobility of positive charge carriers in conjugated polymer films based on dithieno [2,3-b: -d] pyrrole (DTP) is studied by time-resolved microwave conductivity (TRMC). A series of DTP homopolymer and copolymers combined with phenyl, 2,-biphenyl, thiophene, 2,-bithiophene, and 9,-dioctylfluorene were synthesized by Suzuki-Miyaura and Yamamoto coupling reactions. Polymers containing DTP unit are reported to show high value of hole mobility measured by FET method, and this type of polymers is expected to have stable HOMO orbitals which are important for hole transportation. Among these copolymers, DTP coupled with 9,-dioctylfluorene copolymer showed the highest charge carrier mobility as high as 1.7 cm2/Vs, demonstrating an excellent electrical property on rigid copolymer backbones.

Exploration of structure and mechanism of insoluble gels formed in microwave-assisted Suzuki coupling for poly(9,9-dihexylfluorene)s

A series of poly(9,9-dihexylfluorene)s (PDHFs) have been synthesized via microwave-assisted Suzuki and Yamamoto coupling reactions. Compared with the conventional oil-bath heating (48 h, Mw 20100 g/mol by Suzuki reaction and Mw 24000 g/mol by Yamamoto reaction), microwave-assisted polymerization can yield PDHFs with higher molecular weights (Mw 37200 g/mol by Suzuki reaction and Mw 43400 g/mol by Yamamoto reaction) in shorter time (14 and 60 min). However, sometimes formation of insoluble gels was observed together with PDHF in Suzuki coupling reaction. PDHF and insoluble gels were analyzed by XPS, elemental analysis, FTIR, TGA and DSC. Experimental results demonstrated that H2O might take part in the Suzuki coupling reaction under microwave condition, which could make the cross-linking reaction occur and form gels.

Synthesis of novel blue-light-emitting polypyridine

A new regioregular head-to-tail (HT)-type polypyridine with methoxyethoxyethoxy (MEEO) side chains, HT-PMEEOPy, was synthesized by means of Kumada-Tamao coupling polymerization of a Grignard monomer with a Ni catalyst. Although the polymer was precipitated in THF during polymerization, multiangle laser light scattering (MALLS) analysis indicated that the weight-average molecular weight (Mw) was about 25,000. The HT content in the polymer was 95%. A solution of HT-PMEEOPy in CHCl3 was found to emit a strong blue light when the solution was irradiated with UV light; the UV-vis absorption maximum (λmax) and photoluminescence maximum (λmax em) were at 392 and 460 nm, respectively. To clarify the effect of regioregularity of PMEEOPy on the photoluminescence, head-to-head (HH) PMEEOPy was synthesized by means of Yamamoto coupling polymerization. The photoluminescence of HH-PMEEOPy (λmax = 330 nm, λmax em = 414 nm) was weaker than that of HT-PMEEOPy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Synthesis and characterization of blue light emitting polymers based on arylene vinylene

New blue polymers having poly(arylenevinylene) derivatives composed of biphenylene-vinylene-m-(t-butylated) phenylene-vinylene and terphenylene-vinylene-m-(t-butylated)phenylene-vinylene in the main chain were synthesized by nickel catalyzed Yamamoto coupling and palladium-catalyzed Suzuki coupling reactions. The polymers showed good solubility in a common organic solvent and weight average molecular weights of 11,100 to 9,800 with a polydispersity index of 1.46-1.2. The polymers with a highly twisted structure exhibited deep blue emission with (λ max =465 for the homopolymer and λ max =457 nm for copolymer) as well as good thermal stability. Double layer light emitting diode devices fabricated using the obtained polymers as emitters showed blue emission with a maximum brightness of 18–225 cd/m2.

Thieno[3,4-c]pyrrole-4,6-dione-Based Polymer Semiconductors: Toward High-Performance, Air-Stable Organic Thin-Film Transistors

We report a new p-type semiconducting polymer family based on the thieno[3,4-c]pyrrole-4,6-dione (TPD) building block, which exhibits good processability as well as good mobility and lifetime stability in thin-film transistors (TFTs). TPD homopolymer P1 was synthesized via Yamamoto coupling, whereas copolymers P2-P8 were synthesized via Stille coupling. All of these polymers were characterized by chemical analysis as well as thermal analysis, optical spectroscopy, and cyclic voltammetry. P2-P7 have lower-lying HOMOs than does P3HT by 0.24-0.57 eV, depending on the donor counits, and exhibit large oscillator strengths in the visible region with similar optical band gaps throughout the series (∼1.80 eV). The electron-rich character of the dialkoxybithiophene counits in P8 greatly compresses the band gap, resulting in the lowest E(g)(opt) in the series (1.66 eV), but also raising the HOMO energy to -5.11 eV. Organic thin-film transistor (OTFT) electrical characterization indicates that device performance is very sensitive to the oligothiophene conjugation length, but also to the solubilizing side chain substituents (length, positional pattern). The corresponding thin-film microstructures and morphologies were investigated by XRD and AFM to correlate with the OTFT performance. By strategically varying the oligothiophene donor conjugation length and optimizing the solubilizing side chains, a maximum OTFT hole mobility of ∼0.6 cm(2) V(-1) s(-1) is achieved for P4-based devices. OTFT environmental (storage) and operational (bias) stability in ambient was investigated, and enhanced performance is observed due to the low-lying HOMOs. These results indicate that the TPD is an excellent building block for constructing high-performance polymers for p-type transistor applications due to the excellent processability, substantial hole mobility, and good device stability.

Synthesis and device performance of new efficient blue copolymers containing biphenylenevinylene and triphenyldiamine

A series of light-emitting copolymers, poly(N 4,N 4-bis-(4-phenyl)-N 4,N 4′-bis-[4-(2-ethylhexyloxy)phenyl]-biphenyl-4,4′-diamine-co-1,2-bis(4′-phenyl)-1-(9″,9″-dihexyl-3-fluorenyl)ethane), P(BPBEPA-co-BPHFE) with different ratios (5%, 12.5%, 30%) of BPBEPA was synthesized using a Yamamoto coupling reaction. The structures of the copolymers were examined using various spectroscopic methods. The obtained copolymers showed blue fluorescence in 487–496 nm. The introduction of arylamine gave the copolymers good hole injection ability as well as good solubility and thermal stability with high T g . The EL performance of these copolymers were investigated from the devices structure of indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene) (PEDOT), doped with poly(styrenesulfonic acid) (PEDOT:PSS) (40 nm)/polymer (60 nm)/Ca (50 nm)/Li (100 nm). The copolymers exhibited maximum EL peaks in a range from 484 to 489 nm. The maximum current efficiency of 2.17 cd/A, maximum power efficiency of 1.24 lm/W and lower turn-on voltage of 3.5 V for P(BPBEPA12.5-co-BPHFE87.5) were observed. The enhanced EL performance of P(BPBEPA12.5-co-BPHFE87.5) can be explained by charge balance due to the introduced hole transporting BPBEPA.

Nickel-catalyzed synthesis of nanoporous organic frameworks and their potential use in gas storage applications

The synthesis of highly nanoporous organic frameworks (NPOFs) has been established using nickel(0)-catalyzed Yamamoto coupling reactions, which has afforded highly porous polymers featuring remarkable chemical and thermal stability. Treatment of 1,3,5-tris(4-bromophenyl)benzene, 1,2,4,5-tetrakis(4-bromophenyl)benzene, or 1,3,5,7-tetrakis(4-iodophenyl)adamantane with Ni(cod)2 in DMF at 80°C for 48 h afforded the nanoporous organic frameworks, NPOF-1, NPOF-2, and NPOF-3, respectively, as white powders in quantitative yields. All NPOFs are insoluble in common organic solvents such as dimethylformamide, tetrahydrofuran, toluene, dichloromethane, and methanol. The chemical composition and structural aspects of NPOFs were investigated by spectral and analytical methods while porosity was examined by nitrogen porosity measurements. In spite of their amorphous nature, NPOFs exhibit permanent porosity and high Langmuir surface areas (NPOF-1: 2,635 m2 g−1; NPOF-2: 4,227 m2 g−1; NPOF-3: 2,423 m2 g−1), which make them attractive for subsequent use in gas storage and separation applications, among others. The performance of NPOFs in hydrogen storage was evaluated at 1 bar and 77 K and revealed that these highly porous architectures can store up to 1.45 wt% of hydrogen.

A new N-fluorenyl carbazole host material: Synthesis, physical properties and applications for highly efficient phosphorescent organic light emitting diodes

A new N-fluorenyl carbazole material, 9,9′-bis-(9,9-dimethyl-9H-fluoren-2-yl)-9H,9′H-[3,3′]bicarbazolyl (BDFC), was synthesized by bromination, Ullmann and Yamamoto coupling reactions and confirmed using various spectroscopic studies. Thermogravimetric analysis and differential scanning calorimetry studies show the thermal stability (Δ T 5%) of 494.7 °C with high glass transition temperature ( T g) of 177.8 °C. The photophysical and electrochemical studies of BDFC show the photoluminescence at 408 nm and a band gap of 3.01 eV with higher triplet energy of 2.72 eV. The phosphorescent organic light emitting diode using BDFC as host, ITO/di-[4-( N, N-ditolyl-amino)-phenyl]cyclohexane (TAPC)/host: fac-tris(2-phenylpyridine)-iridium [Ir(ppy) 3] (5%)/1,3,5-tris(m-pyrid-3-yl-phenyl)benzene (TmPyPB)/LiF/Al, shows the effective confinement of triplet excitons and efficient energy transfer to the guest emitter in the emissive layer, resulted in the higher device efficiencies of 56.3 cd/A, 18.1% and 21.3 lm/W compared with that (48.1 cd/A, 15.3% and 16.3 lm/W) of device based on (4,4′- N, N′-dicarbazole)biphenyl (CBP) as host. The results show that the new host material BDFC could be useful for the efficient organic light emitting diodes.

Synthesis and Characterization of Quinoxaline-Based Thiophene Copolymers as Photoactive Layers in Organic Photovoltaic Cells

A series of new quinoxaline-based thiophene copolymers (PQx2T, PQx4T, and PQx6T) was synthesized via Yamamoto and Stille coupling reactions. The Mws of PQx2T, PQx4T, and PQx6T were found to be 20,000, 12,000, and 29,000, with polydispersity indices of 2.0, 1.2, and 1.1, respectively. The UV-visible absorption spectra of the polymers showed two distinct absorption peaks in the ranges 350 - 460 nm and 560 - 600 nm, which arose from the π-π* transition of oligothiophene units and intramolecular charge transfer (ICT) between a quinoxaline acceptor and thiophene donor. The HOMO levels of the polymer ranged from ‒5.37 to ‒5.17 eV and the LUMO levels ranged from ‒3.67 to ‒3.45 eV. The electrochemical bandgaps of PQx2T, PQx4T, and PQx6T were 1.70, 1.71, and 1.72 eV, respectively, thus yielding low bandgap behavior. PQx2T, PQx4T, and PQx6T had open circuit voltages of 0.58, 0.42, and 0.47 V, and short circuit current densities of 2.9, 5.29 and 9.05 mA/cm 2 , respectively, when PC71BM was used as an acceptor. For the solar cells with PQx2T-PQx6T:PC71BM (1:3) blends, an increase in performance was observed in going from PQx2T to PQx6T. The power conversion efficiencies of PQx2T, PQx4T, and PQx6T devices were found to be 0.69%, 0.73%, and 1.80% under AM 1.5 G (100 mW/cm 2 ) illumination.

Rational Concept To Recognize/Extract Single-Walled Carbon Nanotubes with a Specific Chirality

Single-walled carbon nanotubes (SWNTs) have remarkable and unique electronic, mechanical, and thermal properties, which are closely related to their chiralities; thus, the chirality-selective recognition/extraction of the SWNTs is one of the central issues in nanotube science. However, any rational materials design enabling one to efficiently extract/solubilize pure SWNT with a desired chirality has yet not been demonstrated. Herein we report that certain chiral polyfluorene copolymers can well-recognize SWNTs with a certain chirality preferentially, leading to solubilization of specific chiral SWNTs. The chiral copolymers were prepared by the Ni(0)-catalyzed Yamamoto coupling reaction of 2,7-dibromo-9,9-di-n-decylfluorene and 2,7-dibromo-9,9-bis[(S)-(+)-2-methylbutyl]fluorene comonomers. The selectivity of the SWNT chirality was mainly determined by the relative fraction of the achiral and chiral side groups. By a molecular mechanics simulation, the cooperative interaction between the fluorene moiety, alkyl side chain, and graphene wall were responsible for the recognition/dissolution ability of SWNT chirality. This is a first example describing the rational design and synthesis of novel fluorene-based copolymers toward the recognition/extraction of targeted (n, m) chirality of the SWNTs.

Synthesis and characterization of low-band-gap poly(thienylenevinylene) derivatives for polymer solar cells

A series of conjugated polymers containing thienylenevinylene moieties as the electron donor for polymer solar cells were synthesized through Yamamoto and Stille coupling. The structure and device properties of the homopolymer (E)-poly[2,2′-(1,2-ethenediyl)bisthiophene] (PEBT), and two donor–acceptor-type copolymers (E)-poly[2,2′-(1,2-ethenediyl)bisthiophene-alt-4,7-(2,1,3-benzothiadiazole)] (PEBTBT) and (E)-poly[2,2′-(1,2-ethenediyl)bisthiophene-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PEBTTBT) were investigated. The vinylene group inserted between two thiophene rings has an important role in lowering the band gap of thienylenevinylene derivatives. In addition, the donor–acceptor-type copolymers including a benzothiadiazole unit showed even lower band gap than their own homopolymer due to intramolecular charge transfer (ICT) through their conjugated backbones. As a result, PEBT, PEBTBT and PEBTTBT showed band gaps of 1.77, 1.37 and 1.57 eV, respectively. Bulk heterojunction photovoltaic devices were fabricated using blends of the polymers with [6,6]-phenyl C71-butyric acid methyl ester (PC70BM) and PEBTBT gave the best power conversion efficiency among them, at 1.07% under AM 1.5, 100 mW cm−2.

Synthesis and properties of phenothiazylene vinylene and bithiophene-based copolymers for organic thin film transistors

A series of new phenothiazylene vinylene and thiophene copolymers (P1, P2, and P3) have been synthesized via Yamamoto and Stille coupling reactions. The number-averaged molecular weights (Mn) of P1, P2, and P3 were found to be 12,000, 10,000, and 8200, with polydispersity indices of 3.5, 1.4, and 1.6, respectively. The UV–visible absorption spectra of the polymers contain two strong absorption bands in the ranges 306–325nm and 430–480nm, which arise from the absorptions of the phenothiazine segments and the conjugated main chains respectively. Solution-processed field-effect transistors (FETs) fabricated with these polymers exhibit p-type organic thin film transistor characteristics. The field-effect mobilities for P1, P2, and P3 were measured to be 1.8×10−4, 5.7×10−4, and 2.5×10−7cm2V−1s−1, respectively, with the corresponding on/off ratios of 5×102, 1×104, and 5×102.

Pyridine−EDOT Heteroarylene−Vinylene Donor−Acceptor Polymers

Two heteroarylene-vinylene donor−acceptor polymers, P(2,6-Py-V-EDOT) and P(2,5-Py-V-EDOT), containing vinylene-spaced simple donor (EDOT) and acceptor (pyridine) moieties, are presented. The central pyridine ring of the repeating unit is either 2,6- or 2,5-substituted, leading to different structural and electronic properties of the monomers. Polymers were obtained by either oxidative electropolymerization or Yamamoto coupling and fully characterized by NMR, UV−vis absorption, GPC, TGA, DSC, electrochemistry, and spectroelectrochemistry. Detailed ab initio computations have been performed for the monomers and model oligomers for analyzing their optical and electronic properties. GPC showed that isolated polymers obtained via Yamamoto poly coupling have low molecular weights, likely due to solubility issues. The electrochemical polymerizations led to p- and n-dopable polymers, with 2,5-Py-V-EDOT yielding more reversible n-doped process. The energetic positions revealed HOMO (−5.1 and −5.0 eV), LUMO (−3.4 e...

High Surface Area Networks from Tetrahedral Monomers: Metal-Catalyzed Coupling, Thermal Polymerization, and “Click” Chemistry

A series of tetrahedrally linked conjugated microporous polymer networks were prepared using a variety of bond-forming chemistries including Sonogashira−Hagihara coupling, Yamamoto coupling, thermal alkyne condensation, and “click” chemistry. These thermally stable polymers exhibit high surface areas (up to 3200 m2/g) and adsorb up to 2.34 wt % hydrogen by mass at 1.13 bar/77 K and 7.59 wt % carbon dioxide by mass at 1.13 bar/298 K.

Polymeric Squaraine Dyes as Electron Donors in Bulk Heterojunction Solar Cells

AbstractA polysquaraine low‐band‐gap polymer was synthesized by Yamamoto coupling of a monomeric dibromoindolenine squaraine dye. The resulting polymer has $\overline M _{\rm w} $ ≈ 34 000 and PDI ≈ 1.7. The electronic properties of monomer and polymer were investigated by CV, absorption, and emission spectroscopy. Bulk heterojunction solar cells were prepared from blends of the polysquaraine with the fullerene derivative PCBM in different weight ratios (1:3 to 1:1). The power conversion efficiencies under simulated AM1.5 conditions yielded 0.45% for these non‐optimized systems. The EQE shows that the photoresponse spans the range from 300 to 850 nm, which illustrates the promising properties of this novel organic semiconductor as a low band gap donor material in organic photovoltaics.magnified image