Novel optically active poly(amide-imide)s from N,N-(4,4-carbonyldiphthaloyl)-bis-l-phenylalanine diacid chloride and aromatic diamines by microwave irradiation

3,3^′,4,4^′-benzophenonetetracarboxylic dianhydride (4,4^′-carbonyldiphthalic anhydride) (1) was reacted with l-phenylalanine (2) in a mixture of acetic acid and pyridine (3:2) and the resulting imide-acid [N,N^′-(4,4^′-carbonyldiphthaloyl)-bis-l-phenylalanine diacid] (4) was obtained in high yield. The compound (4) was converted to the N,N^′-(4,4^′-carbonyldiphthaloyl)-bis-l-phenylalanine diacid chloride (5) by reaction with thionyl chloride. A new facile and rapid polycondensation reaction of this diacid chloride (5) with several aromatic diamines such as 4,4^′-diaminodiphenyl methane (6a), 2,4-diaminotoluene (6b), 4,4^′-sulfonyldianiline (6c), p-phenylenediamine (6d), 4,4^′-diaminodiphenylether (6e), m-phenylenediamine (6f), benzidine (6g) and 2,6-diaminopyridine (6h) was developed by using a domestic microwave oven in the presence of a small amount of a polar organic medium such as o-cresol. The polymerization reactions proceeded rapidly, compared with the conventional solution polycondensation, and was completed within 7 min, producing a series of optically active poly(amide-imide)s with high yield and inherent viscosity of 0.22-0.52 dl/g. All of the above polymers were fully characterized by IR, elemental analyses and specific rotation. Some structural characterization and physical properties of this optically active poly(amide-imide)s are reported.     

Synthesis and characterization of polybinaphthalene incorporating chiral (R) or (S)-1,1′-binaphthalene and oxadiazole units by Heck reaction

Chiral conjugated polymers P-1 and P-2 were synthesized by the polymerization of (R)-3,3′-diiodo-2,2′-bisbutoxy-1,1′-binaphthalene ((R)-M-1) and (S)-3,3′-diiodo-2,2′-bisbutoxy-1,1′-binaphthalene ((S)-M-1) with 2,5-bis(4-vinylphenyl)-1,3,4-oxadiazole (M-2) under Pd-catalyzed Heck coupling reaction, respectively. Both monomers and polymers were analysed by NMR, MS, FT-IR, UV, DSC-TG, fluorescent spectroscopy, GPC and CD spectra. The chiral conjugated polymers exhibit strong Cotton effect in their circular dichroism (CD) spectra indicating a high rigidity of polymer backbone. CD spectra of polymers P-1 and P-2 are almost identical and have opposite signs for their position. These polymers have strong blue fluorescence.     

Cyclopalladation of enantiopure oxazolines having the prochiral CMe2 moiety at position 2 of the heterocycle

(R)-4-Ethyl-2-(1,1-dimethylpropyl)-2-oxazoline (1) and (S)-4-tert-butyl-2-(1,1-dimethylbutyl)-2-oxazoline (2) were synthesized in two steps from the corresponding enantiopure amino alcohols and acid chlorides in a total yield of 95% and 72%, respectively. (S)-2-(1-Adamantyl-1-methylethyl)-4-isobutyl-2-oxazoline (3) was obtained from adamantyl bromide and l-leucinol in five steps in a total yield of 82%. Reactions of oxazolines 1–3 with Pd(OAc)₂ in AcOH or CH₂Cl₂ followed by treatment with LiCl afforded the corresponding μ-Cl dimeric cyclopalladated complexes 15, 17, and 20 in good yield. Compounds 15, 17, and 20 reacted with PPh₃ to furnish the corresponding mononuclear complexes 16, 19, and 21. The ³¹P NMR spectra of trans(N,P) adducts 16, 19, and 21 contained signals of two diastereomers in a ratio of ca. 1.3:1.     

Microwave-promoted synthesis of new optically active poly(ester-imide)s derived from N,N-(pyromellitoyl)-bis-l-leucine diacid chloride and aromatic diols

Pyromellitic dianhydride (benzene-1,2,4,5-tetracarboxylic dianhydride) (1) was reacted with l-leucine (2) in a mixture of acetic acid and pyridine (3:2) and the resulting imide-acid [N,N^′-(pyromellitoyl)-bis-l-leucine diacid] (4) was obtained in quantitative yield. The compound (4) was converted to the N,N^′-(pyromellitoyl)-bis-l-leucine diacid chloride (5) by reaction with thionyl chloride. A new facile and rapid polycondensation reaction of this diacid chloride (5) with several aromatic diols such as phenol phthalein (6a), bisphenol-A (6b), 4,4^′-hydroquinone (6c), 1,8-dihydroxyanthraquinone (6d), 1,5-dihydroxy naphthalene (6e), 4,4-dihydroxy biphenyl (6f), and 2,4-dihydroxyacetophenone (6g) was developed by using a domestic microwave oven in the presence of a small amount of a polar organic medium such as o-cresol. The polymerization reactions proceeded rapidly and are completed within 10 min, producing a series of optically active poly(ester-imide)s (PEIs) with good yield and moderate inherent viscosity of 0.10-0.27 dl/g. All of the above polymers were fully characterized by IR, elemental analyses and specific rotation. Some structural characterization and physical properties of these optically active PEIs are reported.     

Generation of Ir-Sn and Rh-Sn bonds from the oxidative addition of tin(IV) halides to [Ir(μ-Cl)(1,5-COD)]2 and [Rh(μ-Cl)(1,5-COD)]2

Facile oxidative addition of SnCl₄, MeSnCl₃, and SnBr₄ across Ir(I) and Rh(I) cyclooctadiene complexes resulted in the formation of the corresponding Ir-Sn and Rh-Sn heterobimetallic complexes. Treatment of SnCl₄ with [Ir(COD)(μ-Cl)]₂ and [Rh(COD)(μ-Cl)]₂ afforded [Ir(COD)(μ-Cl)Cl(SnCl₃)]₂ (1) and [Rh(COD)(μ-Cl)Cl(SnCl₃)]₂ (2), respectively. Reaction of the organotin halide MeSnCl₃ with [Ir(COD)(μ-Cl)]₂ led to the formation of [Ir(COD)(μ-Cl)Cl(MeSnCl₂)]₂ (3). The reaction of SnBr₄ to Ir^I and Rh^I precursors gave [Ir(COD)(μ-Br)Br(SnBr₃)]₂ (4) and [Rh(COD)(μ-Br)Br(SnBr₃)]₂ (5) respectively, which indicates halide exchange at post-oxidative addition stage. The structures of complexes 1-5 were confirmed by X-ray crystallography. A cis-addition of Sn-X bond across Ir^I/Rh^I is proposed from the analysis of the geometrical features of “X-M-Sn” triangular units in 1-5.     

Chiroptical switching system based on the host-guest interaction between metal cations and poly(phenylacetylene)s bearing polycarbohydrate ionophore

Polycarbohydrate macromonomers with different degrees of polymerization (DP), that is, end-functionalized (1 → 6)-2,5-anhydro-3,4-di-O-ethyl-d-glucitols with 4-ethynylbenzoyl groups (macromonomer 2: DP = 6.6, and macromonomer 3: DP = 9.5) were synthesized. The copolymerizations of these macromonomers and phenylactylene (PA) were carried out in various molar ratios to give poly(phenylacetylene)s bearing a polycarbohydrate ionophore as the graft chain with various grafting rates, poly-(2_x-co-PA_y) and poly-(3_x-co-PA_y). These polymers showed split-type circular dichroism (CD) spectra in the long absorption region of the conjugated polymer backbones (280-500 nm). This indicated that poly-(2_x-co-PA_y) and poly-(3_x-co-PA_y) had predominantly one-handed helical conformations in the backbones. The CD spectral patterns of these polymers were inverted in the presence of metal cationic guest molecules. On the other hand, control experiments using poly(phenylacetylene)s bearing a monocarbohydrate (poly-(4_x-co-PA_y)) and metal cations did not show such a CD spectral inversion. These results clearly indicated that the chiroptical switching of the poly(phenylacetylene)s bearing polycarbohydrate ionophore was attributable to the host-guest complexation of the polycarbohydrate ionophore with metal cations.     

Quinoline-functionalized N-heterocyclic carbene complexes of iridium: Synthesis, structures and catalytic activities in transfer hydrogenation

Iridium complexes containing quinoline-functionalized N-heterocyclic carbene (NHC) ligands have been synthesized by the transmetalation route from silver carbene precursors. The silver complexes undergo a facile reaction with [Ir(COD)Cl]₂ (COD = 1,5-cyclooctadiene) to yield a series of carbene complexes [(NHC)Ir(COD)Cl] (NHC = 3-methyl-1-(8-quinolylmethyl)imidazole-2-ylidene (2a); 3-n-butyl-1-(8-quinolylmethyl)imidazole-2-ylidene (2b); 3-benzyl-1-(8-quinolylmethyl)imidazole-2-ylidene (2c); 1,3-di(8-quinolylmethyl)imidazole-2-ylidene (2d). The coordinated COD was replaced by carbon monoxide to yield the corresponding carbonyl species [(NHC)Ir(CO)₂Cl] (3). Complexes 2 and 3 have been characterized by IR, ESI-MS, ¹H and ¹³C NMR and elemental analyses. The molecular structures of complexes 2b and 2c have been confirmed by single-crystal X-ray diffraction. Two analogous Ir(I) complexes 5 and 6 with naphthalene-containing NHC have also been synthesized and characterized. These Ir(I) complexes in the current work have been proved to be active catalysts in the transfer hydrogenation of ketones to alcohols using 2-propanol as the hydrogen source.     

Synthesis and characterization of dithienobenzothiadiazole-based donor–acceptor conjugated polymers for organic solar cell applications

New donor–acceptor conjugated polymers (P1 and P2) containing a fused-ring dithienobenzothiadiazole (DT-BTD building block) were synthesized by using the Stille copolymerization method. The synthesized polymers were characterized by ¹H NMR, GPC, and elemental analysis. The optical band gaps of the polymers were found to be 1.86 and 1.9 eV, respectively, as calculated from their film onset absorption edge. Upon annealing both produced a distinct shoulder peak in their film absorption spectra. The electrochemical studies of P1 and P2 revealed that the HOMO and LUMO energy levels of the polymer were −5.3, −5.1 eV, and −3.4, −3.2 eV, respectively. The polymers are thermally stable up to 250–350 °C.     

Rapid synthesis of optically active poly(amide-imide)s by direct polycondensation of aromatic dicarboxylic acid with aromatic diamines

4,4^′-(Hexafluoroisopropylidene)-N,N^′-bis(phthaloyl-l-leucine-p-amidobenzoic acid) (2) was prepared from the reaction of 4,4^′-(hexafluoroisopropylidene)-N,N^′-bis(phthaloyl-l-leucine) diacid chloride with p-aminobenzoic acid. The direct polycondensation reaction of monomer (2) with p-phenylenediamine (2a), 4,4^′-diaminodiphenylsulfone (2b), 2,4-diaminotoluene (2c), 2,6-diaminopyridine (2d), m-phenylene diamine (2e), benzidine (2f), 4,4^′-diaminodiphenylether (2g) and 4,4^′-diaminodiphenyl methane (2h) was carried out in a medium consisting of triphenyl phosphite, N-methyl-2-pyrolidone, pyridine, and calcium chloride. The homogeneous mixture was heated at 220 °C for 1 min under nitrogen. The resulting poly(amide-imide)s (PAIs) having inherent viscosities 0.27-0.78 dl/g were obtained in high yield and are optically active and thermally stable. All of the above polymers were fully characterized by IR spectroscopy, elemental analyses and specific rotation. Some structural characterization and physical properties of this new optically active PAIs are reported.     

Synthesis, characterization and photovoltaic properties of thiophene copolymers containing conjugated side-chain

Five side-chain conjugated polythiophene derivatives, P1-P5, were synthesized by Stille coupling reaction. The effects of side-chain structures, bearing CC double bond, CC triple bond as well as different number of methoxy substituents on the benzene ring of the side-chains, on the optical, electrochemical, and photovoltaic properties of the polymers were investigated. From P1 to P3, the effect of CC triple bond and CC double bond was compared. The results indicate that the content of the thiophene units with the CC triple bond in their conjugated side-chains not only influences the absorption shape and intensity, but also influences the energy bandgap and the photovoltaic properties of the polymers. From P3 to P5, the effect of methoxy substituents on the benzene ring of the conjugated side-chains was compared. On increasing the number of the methoxy groups on the benzene ring of the conjugated side chains, the visible π-π^∗ absorption of the conjugated polymer backbone become stronger both in solution and in film. Electron-donating ability of the methoxy groups decreased the bandgap of the polymers. The best polymer solar cell based on P5 with a structure of ITO/PEDOT:PSS/Polymer:PCBM (1:1 wt/wt)/Mg/Al showed a power conversion efficiency of 1.45% under the illumination of AM1.5, 80 mW/cm².     

Synthesis and thermal reaction of hydrido(selenolato) platinum(II) complex having a 9,10,11,12,14,15-hexahydro-9,10[3′,4′]-furanoanthracenyl group

The oxidative addition of selenol, HhfSeH (2, Hhf = 9,10,11,12,14,15-hexahydro-9,10[3′,4′]-furanoanthracenyl) with [Pt(η²-nb)(Ph₃P)₂] (nb = norbornene) in toluene afforded the corresponding hydrido(selenolato) Pt(II) complex [cis-PtH(SeHhf)(Ph₃P)₂] (3) as a stable compound. Refluxing a xylene solution of 3 produced two isomers of five-membered selenaplatinacycles 4 in moderate yield as an inseparable mixture. In addition, the molecular structures of HhfSeH 2 and the minor selenaplatinacycle 4a were determined by X-ray crystallography.     

Influence of sterically non-hindering methyl groups on adsorption properties of two classical zinc and copper MOF types

The metal-organic frameworks (three-dimensional porous coordination polymers) [Zn₄O(Me₄BPDC)₃] × 9 DMF, 2 · 9 DMF and [Cu₂(Me₄BPDC)₂] × 9 DMF, 3 · 9 DMF are representatives of the classical Zn-IRMOF series and Cu paddle-wheel complexes with H₂Me₄BPDC = 2,2′,6,6′-tetramethyl-4,4′-biphenyldicarboxylic acid, 1. The dicarboxylate linker of 1 is a representative of the non-planar biphenyl ligand family, known as an efficient scaffold for chiral molecules. There is a 90° twist angle between the phenyl rings in 1, dictated by the methyl groups, which leads to assembly of doubly interpenetrated pcu-a (in 2) and nbo-a (in 3) nets under low temperature solvothermal conditions in dimethylformamide (DMF). Activation by degassing (to yield 2), exchange with methanol or tetrahydrofuran and subsequent evacuation at elevated temperatures (to yield 3^I) gave materials with BET surface areas of 1735 m²/g (2) and 1041 m²/g (3^I). Adsorbed quantities of H₂ were 1.26 wt% (2) and 1.02 wt% (3^I) (77 K, 1 bar), CO₂ 30.8 cm³/g (2) and 50 cm³/g (3^I) (273 K, 1 bar) and CH₄ 12.9 cm³/g (2) and 11.4 cm³/g (3^I) (273 K, 1 bar). The H₂ and CO₂ sorption values for 2 are similar to those of MOF-5 (IRMOF-1) with its almost doubled BET surface area. An increase is found concerning the adsorbed amounts of N₂, H₂, and CO₂ for 3^I compared to related doubly interpenetrated nbo-a-type MOF-601, MOF-602, MOF-603 ([Cu₂L₂] with L = 2,2′-R₂-4,4′-biphenyldicarboxylate, R = CN, Me, I, respectively).     

Cyclopolymerization XXXIII. Radical polymerizations and copolymerizations of 1,6-dienes with 2-phenylallyl group and thermal properties of polymers derived therefrom

Radical polymerizations of α-allyloxymethylstyrene (1) and copolymerizations of α-(2-phenylallyloxy)methylstyrene (2) were undertaken to acquire comprehensive understanding on polymerization behavior of these dienes and to get polymers with high thermal stability and high glass transition temperature (T_g). One of the monofunctional counterparts of 1 is a derivative of α-methylstyrene, the ceiling temperature of which is low, and the other is an allyl compound that is well-known for the low homopolymerization tendency. This means that the intermolecular propagation reactions leading to pendant uncyclized units are suppressed during the polymerization of 1 to yield highly cyclized polymers. In fact, the degree of cyclization of poly(1) obtained at 140 °C attained the value 92%. Structural studies revealed that repeat cyclic units of poly(1) consist exclusively of five-membered rings. Poly(1) was found to be stable up to 300 °C, but its T_g values were detected at around 100 °C. They are considerably lower than the targeted values which should lie between 180 and 220 °C. An additional drawback of poly(1) is its low molecular weight probably due to a degradative chain transfer. For this reason, copolymerizations of 2 with 1 and with styrene were also carried out to seek for the possibility to control the thermal properties precisely. Monomer 2 was chosen, since it has been reported in our previous work that it yields polymers with thermal stability up to 300 °C and T_g higher than 250 °C. Copolymerization of 2 with styrene afforded polymers with desired thermal properties and high molecular weight.     

Insertion of nitrene and chalcogenolate groups into the Ir-C σ bond in a cyclometalated iridium(III) complex

Treatment of [Cp∗Ir(ppy)Cl] (Cp∗ = η⁵-C₅Me₅, ppyH = 2-(2-pyridyl)phenyl) with Ag(OTf) (OTf⁻ = triflate) in MeOH and MeCN gave the solvento complexes [Cp∗Ir(ppy)(solv)][OTf] (solv = MeOH (1) and MeCN (2)). Complex 1 is capable of catalyzing oxidation and azirdination of styrene with PhIO and PhINTs (Ts = tosyl), respectively. Treatment of 2 with a stoichiometric amount of PhINTs resulted in the insertion of the NTs group into the Ir-C(ppy) bond and formation of [Cp∗Ir(η²-ppy-NTs)(MeCN)][OTf] (3). Treatment of 1 with R₂E₂ afforded [Cp∗Ir(ppy)(η¹-R₂E₂)][OTf] (E = S (4), Se (5), Te (6)). Reactions of 4 and 5 with Ag(OTf) resulted in cleavage of the E-E bond and insertion of an ER group into the Ir-C(ppy) bond. The crystal structures of complexes 2-6 and [Cp∗Ir(η²-ppy-S-p-tol)(H₂O)][OTf]₂ have been determined.     

Synthesis, structural characterization, and initial electroluminescent properties of bis-cycloiridiated complexes of 2-(3,5-bis(trifluoromethyl)phenyl)-4-methylpyridine

A series of bis-cyclometalated Ir(III) complexes (8-10, 12, 15, 17, 19, 21, 23, 25, 28, 29 and 33) bearing two chromophoric N^∧C cyclometalated ligands derived from 2-(3,5-bis(trifluoromethyl)phenyl)-4-methylpyridine (1) and a third nonchromophoric ligand has been synthesized. A palladium-catalyzed cross-coupling reaction between 2-chloro-4-methylpyridine (2) and 3,5-bis(trifluoromethyl)phenylboronic acid (3) was used to prepare 2-(3,5-bis(trifluoromethyl)phenyl)-4-methylpyridine (1). Cyclometalation of (1) by IrCl₃ was carried out in (MeO)₃PO, with the formation of chloro-bridged dimer [N^∧C]₂Ir(μ-Cl)₂Ir[C^∧N]₂ (8). Reaction of (8) with lithium 2,4-pentanedionate, lithium 2,2,6,6-tetramethyl-heptane-3,5-dionate (13), dipivaloyltrimethylsilylphosphine (14), 2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octadione (16), 1,1,1,3,3,3-hexafluoro-2-pyridin-2-yl-propan-2-ol (18), 1,1,1,3,3,3-hexafluoro-2-pyrazol-1-ylmethyl-propan-2-ol (20), 2-diphenylphosphanylethanol (22), and 1-diphenylphosphanylpropan-2-ol (24), afforded octahedral iridium complexes 9, 12, 15, 17, 19, 21, 23 and 25, respectively. Complex 10, which contains three different ligands (L₁ = N^∧C of 1; L₂ = N^∧C of 4,4′-dimethyl-[2,2′]bipyridinyl 4; L₃ = O^∧O of 2,4-pentanedione), and complex 11, which contains no cyclometalated ligands (L₁ = 4; L₂ = L₃ = Cl; L₄ = O^∧O of 2,4-pentanedione) were also isolated as minor products in a one-pot reaction between a 94:5 mixture of 1 and 4, IrCl₃ and lithium 2,4-pentanedionate. Reaction of 8 with diphenylphosphanylmethanol (27) in 1,2-dichloroethane unexpectedly led to complexes 28 and 29. The reactions of 8 with benzoylformic acid resulted in the formation of hydroxyl-bridged dimer [N^∧C]₂Ir(μ-OH)₂Ir[C^∧N]₂ (33). According to X-ray analyses, Ir-to-Ir distances in the crystal cell increase from 6.86 Å for 10 to 13.31 Å for 33. The angle theta, which represents the twisting of two cyclometalated C-Ir-N planes relative to each other, varies from 97.5° for 21 to 90.76 for complex 28. OLED devices were fabricated from several Ir complexes and preliminary results are discussed.     

Transition metal cyclopentadienyl complexes bearing perfluoro-4-tolyl substituents

Depending on the ratio of starting materials and the reaction conditions, perfluorotoluene (C₆F₅CF₃) reacts with sodium cyclopentadienide (NaCp; Cp = C₅H₅) and excess sodium hydride to afford, after acidic aqueous workup, moderate to high yields of mono-, bis-, tris-, and tetrakis(perfluoro-4-tolyl)cyclopentadiene (1, 2, 3, and 4, respectively). Treatment of 1 with excess NaH in THF afforded sodium (perfluoro-4-tolyl)cyclopentadienide (5) in 90% yield. Reaction of FeBr₂ with 2 equiv. of 5 afforded a 68% yield of (η⁵-C₅H₄C₇F₇)₂Fe (6). Reaction of ZrCl₄(THF)₂ with 2 equiv. of 5 afforded a 58% yield of (η⁵-C₇F₇C₅H₄)₂ZrCl₂ (7). Reaction of Mn(CO)₅Br with 5 afforded a 74% yield of (η⁵-C₇F₇C₅H₄)Mn(CO)₃ (8). Treatment of 3b with NaH and then with Mn(CO)₅Br in DME afforded a 26% yield of [η⁵-1,2,4-(C₇F₇)₃C₅H₂]Mn(CO)₃ (9). Treatment of 3b with NaH and then with FeBr₂ in DME afforded a trace yield of [η⁵-1,2,4-(C₇F₇)₃C₅H₂]₂Fe (10), which was not fully characterized. Dienes 2a, 3a, and 3b and metal complexes 7, 8, and 9 were structurally characterized by single-crystal X-ray diffraction. Infrared spectroscopic analysis of the substituted CpMn(CO)₃ complexes showed a linear increase of 5 cm⁻¹ in the A-symmteric stretching frequency for each C₇F₇ substituent, compared to the analogous value of 4 cm⁻¹ reported earlier for each pentafluorophenyl (C₆F₅) substituent. Solution voltammetric analysis of the substituted ferrocene 6 revealed a shift in the E_1/2 of 465 mV relative to ferrocene, compared to the analogous value of about 340 mV for 1,1′-bis(pentafluorophenyl)ferrocene.     

Interaction of 2-(2′,6′-dialkylphenylazo)-4-methylphenols with iridium. C-H activation and migration of alkyl group

Reaction of 2-(2′,6′-diethylphenylazo)-4-methylphenol (L²) with [Ir(PPh₃)₃Cl] afforded two organoiridium complexes 3 and 4 via C-H bond activation of an ethyl group in the arylazo fragment of the L² ligand. In both the complexes the azo ligand binds to iridium as a dianionic tridentate C,N,O-donor. Two triphenylphosphines and a hydride (in the case of complex 3) or chloride (in the case of complex 4) are also coordinated to the metal center. A similar reaction of [Ir(PPh₃)₃Cl] with 2-(2′,6′-diisopropylphenylazo)-4-methylphenol (L³) yielded another organoiridium complex 5, where migration of one iso-propyl group from its original location (say, the 2′ position) to the corresponding third position (say, the 4′ position) took place through C-C bond activation. In this complex the modified azo ligand binds to iridium as a dianionic tridentate C,N,O-donor. Two triphenylphosphines and a hydride are also coordinated to the metal center. The structures of complexes 3 and 4 have been optimized through DFT calculations. The structure of complex 5 has been determined by X-ray crystallography. All the complexes show characteristic ¹H NMR signals and intense transitions in the visible region. Cyclic voltammetry on all the complexes shows an oxidation within 0.66-1.10 V vs SCE, followed by a second oxidation within 1.15-1.33 V vs SCE and a reduction within −0.96 to −1.07 V vs SCE.     

Synthesis, characterization and fluorimetric studies of novel photoactive poly(amide-imide) from anthracene 9-carboxaldehyde and 4,4′-diaminodiphenyl ether by microwave irradiation

Trimellitic anhydride acid chloride (2) was obtained by the reaction of trimellitic anhydride (1) and excess amount of thionyl chloride. The acid chloride was reacted with 4,4′-diaminodiphenyl ether (3), and produced the monomer 4. Anthracene-9-carboxaldehyde (5) was reacted with sulfuryl chloride to produce anthracene-9-carboxylic acid chloride (6) in a quantitative yield. Through the reaction of 6 and 2,4,6-triamino-1,3,5-triazine (7), the monomer 8 was produced in high yield. Two monomers were characterized by ¹H NMR and FT-IR spectroscopy, and then were used in the polymerization reaction. A new facile and rapid polycondensation reaction of the two monomers was performed by using a domestic microwave oven. The polymerization reaction proceeded rapidly, compared with the conventional solution polycondensation and was completed within 10 min, producing a photoactive poly(amide-imide) in a quantitative yield. The resulting polymer was characterized by IR, ¹H NMR and TGA techniques. Thermogravimetric analysis indicated that polymer 9 was thermally stable in nitrogen atmosphere. In addition the initial decomposition temperature, 5% and 10% weight loss (T5, T10) were 284, 356 and 408 °C. The residual weight percent at 700 °C was 51.5%, which shows it is moderately thermally stable. Fluorescence properties of polymer 9 were investigated in several solvents. The ideal concentration of each case was determined by fluorescence self quenching phenomena. Also the self quenching mechanism was studied according to the specific behavior of the polymer in different solvents.     

Hyperbranched conjugated polymers with donor-π-acceptor architecture as organic sensitizers for dye-sensitized solar cells

Three novel hyperbranched conjugated polymers (H-tpa, H-cya, and H-pca) with the same conjugated core structure and different functional terminal units were synthesized and applied in dye-sensitized solar cells (DSSCs) as photosensitizers. The photophysical, electrochemical and photovoltaic properties of the three hyperbranched conjugated polymers (HBPs) were investigated in detail. The results showed that donor-π-acceptor architecture in hyperbranched molecule benefited intramolecular charge transfer and consequently increased the generation of photocurrent. The three-dimensional (3D) steric configuration of HBPs could effectively suppress the aggregation of dyes on TiO₂ film, which is beneficial for achieving good photovoltaic performances. Among the three hyperbranched dyes, the highest power conversion efficiency (η) of 3.93% (J_sc = 8.78 mA/cm², V_oc = 0.65 V, FF = 0.688) was obtained with a DSSC based on H-pca dye upon the addition of the same mass ratio chenodeoxycholic acid (CDCA) as coadsorbent under AM 1.5 irradiation with 100 mW/cm² simulated sunlight.     

Microwave-assisted rapid synthesis of novel optically active poly(amide-imide)s containing hydantoins and thiohydantoins in main chain

Rapid and highly efficient synthesis of novel optically active poly(amide-imide)s (PAIs) 6(a-f) was achieved using microwave irradiation. These were made from the polycondensation reactions of 4,4^′-carbonyl-bis(phthaloyl-l-alanine) diacid chloride [N,N^′-(4,4^′-carbonyldiphthaloyl)] bisalanine diacid chloride 5 with six different derivatives of hydantoin and thiohydantoin compounds 4(a-f) in the presence of a small amount of a nonpolar organic medium that acts as a primary microwave absorber. Hydantoin and thiohydantoin derivatives 4(a-e) were synthesis from the reactions between benzil or benzil derivatives 3(a-e) with urea and thiourea. 5,5-Dimethylhydantoin 4f was synthesis from the reactions between acetone cyanohydrin 3f and ammonium carbonate. The polycondensation proceeded rapidly, and was completed within 10 min giving a series of PAIs with an inherent viscosity about 0.25-0.45 dL/g. The resulting PAIs 6(a-f) were obtained in a high yield and were optically active and thermally stable. All of the above compounds were fully characterized by means of Fourier transform infrared spectroscopy, elemental analyses, inherent viscosity (η_inh), solubility tests and specific rotation. Thermal properties of the PAIs 6(a-f) were investigated using thermal gravimetric analysis.