A soluble and multichromic conducting polythiophene derivative

A new soluble polythiophene derivative was synthesized by both chemical and electrochemical oxidative polymerization of 1-4-nitrophenyl-2,5-di(2-thienyl)-1H-pyrrole (SNSNO₂). Chemical method produces a polymer which is completely soluble in organic solvents. The structures of both the monomer and the soluble polymer were elucidated by ¹H and ¹³C-NMR and FTIR. The average molecular weight has been determined by GPC to be Mn = 6.3 × 10³ for the chemically synthesized polymer. P(SNSNO₂) was also synthesized via potentiostatic electrochemical polymerization. Characterizations of the resulting polymer were performed by cyclic voltammetry CV, FTIR and UV-Vis spectroscopy. Four-probe technique was used to measure the conductivities of the samples. Moreover, the spectroelectrochemical and electrochromic properties of the polymer film were investigated. In addition, dual type polymer electrochromic devices ECDs based on P(SNSNO₂) with poly3,4-ethylenedioxythiophene (PEDOT) were constructed. Spectroelectrochemistry, electrochromic switching and open circuit stability of the devices were studied. They were found to have good switching times, reasonable contrasts and optical memories.     

Highly diastereoselective chemoenzymatic synthesis of (2′R)- and (2′S)-2′-deoxy[2′-H]guanosines

In an effort to develop an efficient synthetic method of highly diastereoselective (2′R)- and (2′S)-2′-deoxy[2′-²H]guanosines, chemoenzymatic conversion was investigated. The synthesis of (2′R > 98% de)-2′-deoxy[2′-²H]guanosine was achieved by biological transdeoxyribosylation using (2′R > 98% de)-2′-deoxy[2′-²H]uridine, 2,6-diaminopurine, and Enterobacter aerogenes AJ-11125, followed by treatment with adenosine deaminase. (2′S > 98% de)-2′-Deoxy[2′-²H]guanosine was synthesized from (2′S > 98% de)-2′-deoxy[2′-²H]uridine and 2,6-diaminopurine using thymidine phosphorylase and purine nucleoside phosphorylase instead of E. aerogenes AJ-11125.     

Synthesis and characterization of novel fluorinated polyimides derived from 4-phenyl-2,6-bis[4-(4′-amino-2′-trifluoromethyl-phenoxy)phenyl]pyridine and dianhydrides

A series of organo-soluble polyimides were prepared from a novel fluorinated diamine monomer, 4-phenyl-2,6-bis[4-(4′-amino-2′-trifluoromethylphenoxy)phenyl]pyridine and various commercial aromatic dianhydrides. These polyimides had good solubility in common organic solvents. The obtained strong and flexible PI films exhibited excellent thermal stability with the decomposition temperature (at 5% weight loss) of above 561 °C and the glass transition temperature in the range of 258-312 °C. Moreover, the polymer films showed good electrical insulating property, low dielectric constant and low water uptake due to the introduction of fluorinated substitutes in the polymer backbone. The remarkable combined features ensure these polymers to be ideal candidate materials for advanced microelectronic industry and other related applications.     

Synthesis and characterization of soluble polyimides based on a new fluorinated diamine: 4-Phenyl-2,6-bis[3-(4′-amino-2′-trifluoromethyl-phenoxy) phenyl] pyridine

A new kind of pyridine-containing aromatic diamine monomer, 4-phenyl-2,6-bis[3-(4′-amino-2′-trifluoromethyl-phenoxy) phenyl] pyridine (m-PAFP), was successfully synthesized by a modified Chichibabin reaction of 3-(4′-nitro-2′-trifluoro-methyl-phenoxy)-acetophenone with benzaldehyde, followed by a catalytic reduction. A series of fluorinated pyridine-bridged aromatic poly(ether-imide)s were prepared from the resulting diamine monomer with various aromatic dianhydrides via a conventional two-step thermal or chemical imidization method. The inherent viscosities values of these polyimides were in the range of 0.56-1.02 dL/g, and they could be cast and thermally converted into transparent, flexible, and tough polyimide films. The polyimides displayed higher solubility in polar solvents such as NMP, DMSO and m-cresol. The polyimides had good thermal stability, with the glass transition temperatures (T_g) of 187-211 °C, the temperatures at 5% weight loss of 511-532 °C, and the residue at 800 °C in air was higher than 50%. These films also had dielectric constants of 2.64-2.74 at 10 MHz and low water uptake 0.53-0.66%. Wide-angle X-ray diffraction measurements revealed that these polyimides were predominantly amorphous. Moreover, the polymer films of these novel polyimides showed outstanding mechanical properties with the tensile strengths of 90.1-96.6 MPa, elongations at breakage of 8.9-10.7% and tensile modulus of 1.65-1.98 GPa.     

Synthesis and characterization of a bifunctional amido-thiophene monomer and its copolymer with thiophene and electrochemical properties

A bifunctional amido-thiophene namely hexamethylene (bis-3-thiophene acetamide) (HMTA) was synthesized by the reaction of 3-thiophene acetic acid with hexamethylene diamine. Copolymerization in the presence of thiophene was achieved electrochemically in tetrabutylammonium tetrafluoroborate/acetonitrile (TBAFB/AN). Spectroelectrochemical analysis of the resulting copolymer [P(HMTA-co-Th)] reflected electronic transitions at 505 nm, 740 nm and ∼1000 nm, revealing π to π* transition, polaron and bipolaron band formation respectively. Switching ability was evaluated by a kinetic study via measuring the transmittance (%T) at the maximum contrast. Dual type polymer electrochromic devices (ECDs) based on P(HMTA-co-Th) and poly(ethylene dioxythiophene) (PEDOT) have been constructed. Spectroelectrochemistry, switching ability and stability of the devices were investigated by UV-vis spectroscopy and cyclic voltammetry. These devices exhibit low switching voltages (between 0.0 V and +1.6 V), short switching times with reasonable switching stability under atmospheric conditions.     

Liquid crystalline and photoactive poly[4,4′-stilbeneoxy]alkylbiphenylphosphates

A series of liquid crystalline and photoactive polymers were synthesized from biphenylphosphorodichloridate with various 4,4′-bis(m-hydroxyalkyloxy)stilbenes (m = 2, 4, 6, 8, 10) in chloroform by solution polycondensation method using an acid scavenger. The resultant polymers were characterized by inherent viscosity, FT-IR, ¹H, ¹³C and ³¹P NMR spectroscopies. The liquid crystalline (LC) properties were studied using HOPM and DSC and it was inferred that out of the five polymers synthesized, higher methylene chain containing polymers (m = 6, 8, 10) exhibited LC properties. Thermogravimetric analysis revealed that all the polymers were stable in between 290 and 367 °C and underwent degradation thereafter. The thermal stability and char yield of the polymers decreased with increase in flexible methylene chain. The photochemical properties of these polymers were investigated by UV and fluorescence spectroscopy. Crosslinking proceeds via 2π-2π cycloaddition reaction of the -CHCH- of the stilbene moieties. The rate of crosslinking increases with increase in methylene chain length in the polymer backbone. The fluorescence spectra showed that the longer methylene spacer containing polymers exhibited larger red-shifts than the shorter spacer containing polymers.     

Synthesis, characterization and electrochromic properties of copolymer of 3-{[4-(thien-3-yl-methoxy)phenoxy]methyl}thiophene with thiophene

(3-{[4-(Thien-3-yl-methoxy)phenoxy]methyl}thiophene) (TMPMT) was synthesized via the reaction of 3-bromomethylthiophene with hydroquinone and characterized by nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). Electrochemical copolymerization of TMPMT with thiophene in acetonitrile/boron trifluoride diethyl etherate (AN/BFEE) solvent mixture was achieved using tetrabutylammonium tetrafluoroborate (TBAFB) as the supporting electrolyte. Resulting copolymer was characterized via cyclic voltammetry (CV), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), four probe technique conductivity measurement and UV-Vis spectroscopy. Spectroelectrochemical analysis of the copolymer [P(TTMT-co-Th)] revealed that π-π^∗ electronic transition occurs at 427 nm with a band gap value of 2.20 eV. Copolymer gives brown color at the fully reduced state whereas; at fully oxidized state the film has a gray-blue color. Kinetic studies were carried out at the maximum contrast wavelength upon measuring the percent transmittance, T% (7.6%) and switching time (2.0 s) to examine the switching ability of the copolymer. Dual type electrochromic device (ECD) of P(TMPMT-co-Th) and poly(3,4-ethylenedioxythiophene) (PEDOT) was constructed. Spectroelectrochemistry, switching ability, open circuit memory and stability of the device were examined by UV-Vis spectroscopy and cyclic voltammetry. The device switches between brown and blue at switching voltages of 0.0 V and 2.8 V with a short switching time of 1.4 s.     

Synthesis of a dipyrromethane functionalized monomer and optoelectrochromic properties of its polymer

A dipyrromethane functionalized monomer; 5-(4-tert-butylphenyl)dipyrromethane (BPDP) was synthesized. The structure of the monomer was characterized by nuclear magnetic resonance (¹H NMR and ¹³C NMR) and Fourier transform infrared (FTIR) spectroscopies. Electrochemical polymerization of BPDP was performed in acetonitrile (AN)/LiClO₄. The resulting conducting polymer was characterized by FTIR spectroscopy and electrical conductivity measurements. Spectroelectrochemical behavior and switching ability of P(BPDP) film were investigated by UV-Vis spectroscopy. P(BPDP) revealed color changes between yellow and blue in the reduced and oxidized states, respectively. In order to investigate electrochromic properties and stability of the P(BPDP) in electrochromic device (ECDs) application, dual type polymer ECD based on P(BPDP) and poly(ethylene dioxythiophene) (PEDOT) were constructed. Spectroelectrochemistry, switching ability and stability of the devices were investigated by UV-Vis spectroscopy and cyclic voltammetry.     

Two-photon absorption chromophores with a tunable [2,2′]bithiophene core

Sonogashira coupling between 3,5,3′,5′-tetrabromo-[2,2′]bithiophene and various terminal alkynes provides two-photon absorption (TPA) chromophores 1-6, which possess electron donor (D) and/or acceptor (A) alkynyl substituents at 3(3′) and 5(5′) sites of the bithiophene core. The up-converted fluorescence emission excited at 800 nm (Ti:sapphire femtosecond laser, ∼100 fs pulses) was used to determine the two-photon absorption cross-sections (σ) of these compounds. The corresponding TPA cross-section (σ) values ranging from 132 to 1120 GM (10⁻⁵⁰ cm⁴ s photon⁻¹) can be fine-tuned by the substitutents. The quadrupolar-type (A-π-D-π-A) chromophore 5 exhibits the largest σ value (1120 GM) in CH₂Cl₂ upon 800 nm excitation.     

Synthesis and characterization of rhenium(I) complexes with the polypyridinic quinone functionalized electron acceptor ligand [3,2-a:2′,3′-c]-benzo[3,4]-phenazine-11,16-quinone, Nqphen

In this work, the synthesis and characterization of fac-[Re(CO)₃(Nqphen)(L)]PF₆ complexes is reported. Nqphen is the quinone substituted acceptor ligand [3,2-a:2′,3′-c]-benzo[3,4]-phenazine-11,16-quinone, and L represents the donor monodentate pyridine substituted ligands 4-tert-butylpyridine (t-Bupy), 4-methoxypyridine (MeO-py) or 10-(4-picolyl)phenothiazine (py-PTZ). The complexes were synthesized by refluxing in methanol the metal precursor fac-Re(CO)₃(Nqphen)TfO (TfO = trifluoromethanesulphonate anion) with the corresponding L ligand. The UV-Vis spectra of the complexes are dominated by intense intraligand (IL) bands, and less intense metal ligand charge transfer (MLCT) bands with maxima in the 380-400 nm region. The IR shows the typical pattern for tricarbonyl Re complexes with facial (fac) geometry. An additional v(CO) stretching band, attributed to the quinone fragment of Nqphen, is observed.Electrochemical data indicate that the acceptor capacity of Nqphen is increased in the complexes with regard to the free ligand. This effect is sensitive to the nature of the L ligand, following the order: MeO-py < t-Bupy < py-PTZ, indicating therefore that the donor capacity of L affects the rest of the molecule. The results obtained for the fac-[Re (CO)₃(Nqphen)(pyPTZ)]PF₆ complex here reported were compared with those observed for the homologous complex fac-[Re(CO)₃(Aqphen)(L)]^0/+, with Aqphen = 12,17-dihydronaphtho[2,3-h]dipyrido[3,2-a:2′,3′-c]-phenazine-12,17-dione, and L = Cl⁻, TfO⁻, py-PTZ.     

Hole-transporting [3,3′]bicarbazolyl-based polymers and well-defined model compounds

Polymers containing bicarbazolyl moieties in the main chain have been synthesized by the modified Ullmann coupling reaction from 9H,9′H-[3,3′]bicarbazolyl and different dihalo derivatives. The number-average molecular weights of the polymers synthesized were in the range of 2500-6200 with a molecular weight distribution of 1.6-3.1. Well-defined model compounds for the polymers have been synthesized by stepwise reactions. All these compounds have been found to form glasses with glass transition temperatures in the range of 57-119 °C as characterised by differential scanning calorimetry. The electron photoemission spectra of the compounds have been recorded and the ionisation potentials of 5.35-5.4 eV have been established. Room temperature hole drift mobility of the synthesized compounds molecularly dispersed in a polymer host range from 10⁻⁶ to 3 × 10⁻⁵ cm²/V s at an electric field of 10⁶ V/cm at the room temperature.     

Synthesis of light-emmting materials bis-[2′-2″-(9H-fluoren-2-yl)-vinyl-8-hydroxyquinoline] zinc(II) and bis-[2′-4″-(4,5-diphenyl-1H-imidazol-2-yl)styryl-8-hydroxyquinoline] zinc(II)

Two novel light-emitting materials bis-[2′-2″-(9H-fluoren-2-yl)-vinyl-8-hydroxyquinoline] zinc(II) (3) and bis-[2′-4″-(4,5-diphenyl-1H-imidazol-2-yl)styryl-8-hydroxyquinoline] zinc(II) (4) containting 8-hydroxyquinoline and fluorene or imidazole moieties have been synthesized. The optical properties of these complexes were influenced by the styryl substituents, and exhibited orange-emission. They have higher fluorescence quantum yields than Alq₃, and good stabilities with thermal decomposition temperatures 395 °C and 435 °C. The single-layer OLED fabricated by 3 emitted lemon-yellow, and exhibited good device performance with a maximum luminance of 489 cd m⁻², and luminance efficiency of up to 0.41 cd A⁻¹. The single-layer OLED fabricated by 4 emitted yellow-green, and exhibited good device performance with a maximum luminance of 323 cd m⁻², and luminance efficiency of up to 0.54 cd A⁻¹.     

Electroactive aromatic polyamides and polyimides with adamantylphenoxy-substituted triphenylamine units

A new triphenylamine-containing aromatic diamine monomer, 4-[4-(1-adamantyl)phenoxy]-4′,4″-diaminotriphenylamine, was synthesized from cesium fluoride-mediated N,N-diarylation of 4-(1-adamantyl)-4′-aminodiphenyl ether with 4-fluoronitrobenzene and subsequent reduction of the resultant dinitro compound. Novel electroactive aromatic polyamides and polyimides with adamantylphenoxy-substituted triphenylamine moieties were prepared from the newly synthesized diamine monomer with aromatic dicarboxylic acids and tetracarboxylic dianhydrides, respectively. All the resulting polymers were amorphous and most of them were readily soluble in polar solvents such as N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc) and could be solution-cast into transparent and strong films with good mechanical properties. These polymers exhibited glass-transition temperatures between 254 and 310 °C, and they were fairly stable up to a temperature above 450 °C for the polyamides and above 500 °C for the polyimides. These polymers exhibited strong UV-vis absorption maxima at 293-346 nm in solution, and the photoluminescence spectra of polyamides showed maximum bands around 408-452 nm in the blue region. Cyclic voltammograms of the polyamide and polyimide films on an indium-tin oxide (ITO)-coated glass substrate exhibited one pair of reversible redox couples at half-wave oxidation potentials (E_1/2) around 0.83-0.86 V and 1.12-1.13 V, respectively, versus Ag/AgCl in an acetonitrile solution. All the polymer films revealed good electrochemical and electrochromic stability by repeatedly switching electrode voltages between 0.0 V and 1.1-1.4 V, with coloration change from the pale yellowish neutral state to the green or blue oxidized state.     

Electrosyntheses and characterization of poly(9-bromophenanthrene) in boron trifluoride diethyl etherate

A novel semi-conducting polymer poly(9-bromophenanthrene) (P9BP) was synthesized electrochemically by direct anodic oxidation of it is monomer 9-bromophenanthrene (9BP) in boron trifluoride diethyl etherate (BFEE). The oxidation onset potential of 9BP in this medium was measured to be only 1.33 V vs. saturated calomel electrode (SCE). P9BP films obtained from BFEE showed good electrochemical behavior and nice thermal stability with electrical conductivity of 0.03 S cm⁻¹. FTIR and ¹H NMR spectra together with theoretical quantum chemistry calculations indicated that the P9BP was mainly grown via the coupling of the monomer at C₃ and C₆ positions. Furthermore, P9BP exhibited strong electrochromic nature from opaque green to light yellow between the doped and dedoped states on ITO electrode in solid state. Fluorescence spectral studies indicated that P9BP was a blue light emitter.     

Synthesis of substituted dipyrido[3,2-a:2′,3′-c]phenazines and a new heterocyclic dipyrido[3,2-f:2′,3′-h]quinoxalino[2,3-b]quinoxaline

Three new α,α′-diimine ligands were synthesized based on condensation of 1,10-phenanthroline-5,6-dione with 1,2-phenylenediamine derivatives using different approaches. All compounds were fully characterized by IR, ¹H and ¹³C NMR, UV-visible, and MS spectroscopies. We report the first example of a dipyrido[3,2-f:2′,3′-h]quinoxalino[2,3-b]quinoxaline, which exhibits a strong absorption at 430 nm and an interesting electrochemical behavior. These new molecules may have biological potential and are of synthetic and technological importance.     

New active ruthenium(II) complexes based N3,N3′-bis(diphenylphosphino)-2,2′-bipyridine-3,3′-diamine and P,P′-diphenylphosphinous acid-P,P′-[2,2′-bipyridine]-3,3′-diyl ester ligands for transfer hydrogenation of aromatic ketones by propan-2-ol

The dimeric starting material [Ru(η⁶-p-cymene)(μ-Cl)Cl]₂ reacts with N3,N3′-bis(diphenylphosphino)-2,2′-bipyridine-3,3′-diamine, 1 and P,P′-diphenylphosphinous acid-P,P′-[2,2′-bipyridine]-3,3′-diyl ester, 2 ligands to afford bridged dinuclear complexes [C₁₀H₆N₂{NHPPh₂-Ru(η⁶-p-cymene)Cl₂}₂], 3 and [C₁₀H₆N₂{OPPh₂-Ru(η⁶-p-cymene)Cl₂}₂], 4 in quantitative yields. These bis(aminophosphine) and bis(phosphinite) based Ru(II) complexes serve as active catalyst precursors for the transfer hydrogenation of acetophenone derivatives in 2-propanol and especially 4 acts as a good catalyst, giving the corresponding alcohols in 99% yield in 20 min (TOF ? 280 h⁻¹).     

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.     

Design and synthesis of fluorescent 6-aryl[1,2-c]quinazolines serving as selective and sensitive ‘on-off’ chemosensor for Hg in aqueous media

Three fluorescent quinazolines thiophen-2-yl-5,6-dihydrobenzo-[4,5]imidazo[1,2-c]quinazoline (1), pyridin-3-yl-5,6-dihydrobenzo-[4,5]imidazo-[1,2-c]quinazoline (2) and phenyl-5,5′,6,6′-dihydrobenzo-[4,4′,5,5′]imidazo-[1.1′,2-c,2′-c]quinazoline (3) have been synthesized. Structures of 1 and 3 have been authenticated crystallographically. Quinazolines 1-3 exhibit highly selective ‘on-off’ switching for Hg²⁺ ions. The fluorescence intensity displayed a linear relationship with respect to Hg²⁺ concentration (0.1-1.0 μM; R² = 0.99) with detection limit of 2.0 × 10⁻⁷ M.     

Synthesis, crystal and molecular structure of gold(I) thiophenolate with 4′-ferrocenyl[1,1′]biphenylisocyanides

The syntheses of ferrocenylbiphenylisocyanide gold(I) thiophenolato complexes are described. The preparative route starts from ferrocenylphenylbromide and proceeds in six steps to yield the desired gold(I) complexes, (thiophenolato)gold{(4′-ferrocenyl[1,1′]biphenyl-4-yl)isocyanide} (11) and (thiophenolato)gold{(4′-ferrocenyl-3,5-dimethyl[1,1′]biphenyl-4-yl)isocyanide} (12) in good yields. The synthetic pathways were developed as a first step toward realizing the goal of preparing metallomesogens based on ferrocenyl-polyphenylenes coordinated to gold(I) thiophenolates, in which long chain alkoxy groups are substituted para to sulfur on the phenyl ring. The crystal structures of (chloro)gold{(4^′-ferrocenyl[1,1′]biphenyl-4-yl)isocyanide} (9) and 12 are reported. Complex 9 crystallizes in the space group P2₁/c and 12 crystallizes in P2₁/n. Complexes 9 and 12 show short intermolecular Au-Au contacts of 3.3765(7) Å and 3.3334(3) Å, respectively.     

Cucurbit[7]uril stabilization of a diarylmethane carbocation in aqueous solution

The stability of the 4,4′-bis(dimethylamino)diphenylmethane carbocation is significantly enhanced in aqueous solution by its inclusion in the cucurbit[7]uril host cavity. The formation of the host-guest complex (K_CB[7] = 2.0 × 10⁴ M⁻¹) shifts the carbinol-carbocation equilibrium, maximizing the formation of the intensely blue carbocation to 90% at pH 5.2.