A concise synthesis and electrochemical behavior of functionalized poly(thieno[3,4-b]thiophenes): New conjugated polymers with low bandgap

New thieno[3,4-b]thiophene derivatives were prepared via a short and versatile synthetic route. Electrochemical studies of 2-heptenylthieno[3,4-b]thiophene, 2-styrylthieno[3,4-b]thiophene, and 2-phenyl-3-(thieno[3,4-b]thiophene-2-yl)acrylonitrile and the corresponding polymers revealed that raising the HOMO and lowering the LUMO can be attained by functionalizing thieno[3,4-b]thiophene with aromatic resonance-enhancing and electron-withdrawing groups. The bandgap of resulting polymers varied from 0.78 to 1.0 eV, indicating that poly(2-phenyl-3-(thieno[3,4-b]thiophene-2-yl)acrylonitrile) is one of the lowest bandgap polymers ever reported.     

Small bandgap non-fullerene acceptor enables efficient PTB7-Th solar cell with near 0 eV HOMO offset

Three small bandgap non-fullerene(SBG NFAs) acceptors,BDTI,BDTI-2 F and BDTI-4 F,based on a carbon-oxygen bridged central core and thieno[3,4-b]thiophene linker,end-capped with varied electronwithdrawing terminal groups,were designed and synthesized.The acceptors exhibit strong absorption from 600 nm to 1000 nm.The optimal device incorporating designed NFA and PTB7-Th polymer donor achieves a power conversion efficiency of 9.11% with near 0 eV HOMO offset.The work presents a case study of efficient non-fullerene solar cells with small HOMO offsets,which is achieved by blending PTB7-Th with fine-tuned SBG acceptor.     

含五氟苯的噻吩并吡咯二酮苯并二噻吩共轭聚合物的合成及其性能

以3,4-噻吩二甲酸和五氟苯胺为起始原料,经酰化、缩合和NBS溴代反应制得2,5-二溴-5-五氟苯基噻吩［3,4-c］吡咯-4,6-二酮(2); 2经两步反应制得2-溴-2,5-二噻吩-5-五氟苯基噻吩［3,4-c］吡咯-4,6-二酮(4);以苯并二噻吩衍生物（BDT-1和BDT-2）为给体单元,2或4为受体单元,分别经Stille偶联缩聚反应合成了3个含五氟苯的噻吩并吡咯二酮-苯并二噻吩共轭共聚物(5a~5c),其结构和性能经¹H NMR, ¹³C NMR, UV-Vis, TGA和循环伏安法表征。结果表明：5a, 5b和5c的最大吸收峰分别位于559 nm, 559 nm和547 nm,光学带隙分别为1.70 eV, 1.73 eV, 1.68 eV(薄膜)和1.84 eV, 1.83 eV, 1.81 eV(甲苯);失重5%的温度为307～325 ℃; 5a~5c的起始氧化电位和起始还原电位分别为1.14 V, 1.18 V, 1.03 V和-0.67 V, -0.67 V, -0.70 V; HOMO和LUMO能级分别为-5.54 eV, -5.58 eV, -5.43 eV和-3.73 eV, -3.73 eV, -3.70 eV。     

Preparation of new nitrogen-bridged heterocycles. 59. Syntheses and intramolecular interactions of 3-(acylmethylthio)- and 3-[(3-ethoxycarbonyl-2-propenyl)thio]thieno[3,4-b]indolizine derivatives

Various thieno[3,4-b]indolizine derivatives having an acylmethylthio or (3-ethoxycarbonyl-2-propenyl)thio group at the 3-position which could not be obtained by a conventional method were prepared by a new procedure using cyanoethyl group as a protecting group and their intramolecular arene-pi interactions were investigated. In the (1)H-NMR spectra of these thieno[3,4-b]indolizines, the low-field shifts (delta 0.10-0.33 ppm) for the 5-protons were observed in comparison with those of 3-(methylthio)thieno[3,4-b]indolizines as a standard. The UV spectra also exhibited a characteristic absorption band at 425-445 nm attributable to the arene-pi interaction but their intensities were generally lower than those of 3-(arylmethylthio)thieno[3,4-b]indolizines. In their X-ray analyses, the anti conformation for 3-(acylmethylthio)thieno[3,4-b]indolizines and the gauche one for the 3-(3-ethoxycarbonyl-2-propenyl)thio derivatives were exhibited.     

Preparation of new nitrogen-bridged heterocycles. 54.increased arene-arene interactions of 3-(bicyclic and tricyclic arylmethylthio)thieno[3,4-b]indolizine derivatives

Some thieno[3,4-b]indolizine derivatives having a 1-naphthylmethylthio, 2-methyl-1-naphthylmethylthio, 2-naphthylmethylthio, or 9-anthrylmethylthio group at the 3-position were prepared and their intramolecular arene-arene interactions were investigated. In comparison with 3-(methylthio)thieno[3,4-b]indolizines which have no such interactions, the (1)H-NMR spectra of title compounds showed large high-field shifts (delta 0.06-0.89 ppm) for the protons of the pyridine ring in the thieno[3,4-b]indolizine, and these values were considerably larger than those (delta <0.3 ppm) in 3-(benzylthio)thieno[3,4-b]indolizines. The UV spectra also exhibited a characteristic absorption band near 425 nm attributable to the arene-arene interaction. In the X-ray analyses of some compounds, however, the presence of both the gauche and the anti conformers at the sulfide spacer were confirmed.     

Crystalline conjugated polymer containing fused 2,5-di(thiophen-2-yl)thieno[2,3-b]thiophene and thieno[3,4-c]pyrrole-4,6-dione units for bulk heterojunction solar cells

A new conjugated polymer, PDTTTPD, comprising 2,5-di(thiophen-2-yl)thieno[3,2-b]thiophene and thieno[3,4-c]pyrrole-4,6-dione units, exhibits high crystallinity and excellent thermal stability. A device incorporating PDTTTPD and [6,6]-phenyl-C(71)-butyric acid methyl ester (1:1, w/w) exhibited a power conversion efficiency of 5.1%.     

Preparation of new nitrogen-bridged heterocycles. 53. Syntheses of 3-(benzylthio)thieno[3,4-b]indolizine derivatives and their intramolecular arene-arene interactions

Various ethyl 1-arylcarbonyl-3-[(un)substituted methylthio]thieno[3,4-b]indolizine-9-carboxylates were synthesized in good yields by a novel methodology in which the S-alkylation of 5-arylcarbonyl-4-ethoxycarbonylmethyl-3-(1-pyridinio)thiophene-2-thiolates with alkyl or benzyl halides, the 1,5-dipolar cyclization of the resulting pyridinium salts in the presence of a base, and the aromatization were performed. In the X-ray analyses of some 3-(benzylthio)thieno[3,4-b]indolizine-9-carboxylates, a gauche and two anti conformers in relation to the exocyclic sulfide linkage were found. Interestingly, all of the 3-(benzylthio)thieno[3,4-b]indolizine derivatives showed significant high-field shifts (delta up to 0.3 ppm) for the 5- and 6-proton signals compared with those of the 3-methylthio derivatives in the (1)H-NMR spectra and exhibited a definite absorption band near 425 nm in their UV spectra, indicating an intramolecular arene-arene interaction between the thieno[3,4-b]indolizine and the phenyl ring.     

Synthesis of calibrated poly(3,4-ethylenedioxythiophene) latexes in aqueous dispersant media

The synthesis of spherical poly(3,4-ethylenedioxythiophene) (PEDOT) nanoparticles with a narrow size distribution was achieved in a dispersant aqueous medium. Various oxidants such as ammonium persulfate, iron(III) p-toluenesulfonate, and iron(III) trichloride were tested. A series of end-functionalized poly(ethylene oxide) (PEO) such as alpha-(3,4-ethylenedioxythiophene) PEO, alpha-( N-methyl pyrrole) PEO, alpha-(fluorene) PEO, alpha,omega-( N-methyl pyrrole) PEO, alpha,omega-(thiophene) PEO, and alpha,omega-(fluorene) PEO were compared as reactive stabilizers. The molar mass and the functionality of these reactive PEOs were found to be important parameters with respect to the control of particle size and size distribution. PEDOT samples were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), size exclusion chromatography (SEC), and conductivity measurements.     

Poly(acenaphtho[1,2-b]thieno[3,4-e]pyrazine): a new low band gap conjugated polymer

The preparation of a new conjugated polymer with a low band gap of approximately 0.5 eV has been accomplished via the electropolymerization of acenaphto[1,2-b]thieno[3,4-e]pyrazine.     

Near infrared thieno[3,4-b]pyrazine sensitizers for efficient quasi-solid-state dye-sensitized solar cells

Three near infrared (NIR) metal-free organic sensitizers (FNE32, FNE34, FNE36) based on the thieno[3,4-b]pyrazine derivative have been designed and synthesized for application in quasi-solid-state dye-sensitized solar cells (DSSCs). These organic dyes demonstrate maximum absorption bands at 596-625 nm due to the presence of the thieno[3,4-b]pyrazine derivative, which facilitates the intramolecular electron transfer from the donor to the acceptor. Quasi-solid-state DSSCs based on FNE34 display efficient photoelectric conversion over the whole visible range extending into the NIR region up to 900 nm with maximum incident monochromatic photon-to-electron conversion efficiency (IPCE) of 77%, yielding a short-circuit photocurrent density of 16.24 mA cm(-2) and a power conversion efficiency of 5.30%. To the best of our knowledge, this is the highest efficiency for quasi-solid-state DSSCs based on an organic NIR dye. When exposed to one-sun illumination for 1000 h, the quasi-solid-state DSSC based on FNE34 exhibits good long-term stability with almost constant power conversion efficiency.     

1,3,4,6-Tetrakis(isopropylthio)thieno[3,4-c]thiophenium bis(tetrafluoroborate): X-ray crystal structure of a stable thieno[3,4-c]thiophene dication

The structure of the 1,3,4,6-tetrakis(isopropylthio)thieno[3,4-c]thiophene dication ( 2 ) prepared from 1,3,4,6-tetrakis(isopropylthio)thieno[3,4-c]thiophene ( 1 ) by two-electron oxidation was investigated by X-ray crystallographic analysis. The results revealed that the positive charges are largely delocalized on the two i-PrS-C-C-C-SPr-i moieties.     

Structural effects on the electronic properties of extended fused-ring thieno[3,4-b]pyrazine analogues

The synthesis and characterization of the extended thieno[3,4-b]pyrazine analogues acenaphtho[1,2-b]thieno[3,4-e]pyrazine (3a), 3,4-dibromoacenaphtho[1,2-b]thieno[3,4-e]pyrazine (3b), 3-octylacenaphtho[1,2-b]thieno[3,4-e]pyrazine (3c), dibenzo[f,h]thieno[3,4-b]quinoxaline (4), and thieno[3',4':5,6]pyrazino[2,3-f][1,10]phenanthroline (5) are reported. Comparison of structural, electrochemical, and photophysical properties to those of simple thieno[3,4-b]pyrazines are provided in order to provide structure-function relationships within this series of compounds.     

Tetra-EDOT substituted 3D electrochromic polymers with lower band gaps

A couple of novel electrochromic materials poly(2,3,4,5-tetrakis(2,3-hydrothieno[3,4-b]dixin-5-yl)-1-methyl-1H-pyrrole)(P(t-EDOT-mPy))and poly(5,5',5",5'"-(thiophene-2,3,4,5-tetrayl)tetrakis(2,3-dihydrothieno[3,4-b][1,4]dioxine))(P(t-EDOTTh))are electrodeposited via multi-position polymerization of their tetra-EDOT substituted monomers t-EDOT-mPy and t-EDOT-Th,respectively.Compared with the linear 2D structured poly(thiophene)(E_g=2.2 eV)and poly(2,5-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)thiophene)(E_g=1.7eV),P(t-EDOT-Th)(E_g=1.62eV)has the lowest band gap.Hence,we speculate that the band gaps of the two polymers,having 3D structures,are decreased in contrast to non-substituted polymers or bi-EDOT substituted polymers,thiophene and 1-methyl-1H-pyrrole.The results indicated that P(t-EDOT-Th)thin films are more stable and show higher transmittance amid two polymers,which may find their utilization in organic optoelectronics.     

Synthesis of a polythieno[3,4-b]thiophene derivative with a low-lying HOMO level and its application in polymer solar cells

A planar benzodithiophene with lower HOMO was copolymerized with the thieno[3,4-b]thiophene unit to obtain a new low band gap polymer of PBDPTT-C, which exhibited a higher open-circuit voltage (V(oc)) of 0.8 V and a promising efficiency of 5.2%.     

Planar beta-linked oligothiophenes based on thieno[3,2-b]thiophene and dithieno[3,2-b:2',3'-d]thiophene fused units

A series of planar beta-linked oligothiophenes based on thieno[3,2-b]thiophene and dithieno[3,2-b:2',3'-d]thiophene fused units were synthesized. The optical data indicate a blue shift of the absorption maximum in comparison to the alpha-linked analogues due to cross-conjugation between fused rings. The crystal structures of 3,3'-bi(thieno[3,2-b]thiophene) and 3,3';6',3"-ter(thieno-[3,2-b]thiophene) reveal edge-to-face pi-stacked dimer motifs, whereas the crystal structure of 3,3'-bis(dithieno[3,2-b:2',3'-d]thiophene) consists of face-to-face pi-stacked molecules. [structure: see text]     

Reactions of some new thienothiophene derivatives

Facile and convenient syntheses of bisdimethylthieno[2,3-b]thiophen-2,5-diyl bis(oxazole-2-amine), bis(1H-imidazol-2-amine), bis((3a)-H-indole),[1,2-a]pyrimidine), bis(1H-imidazo[1,2-b][1,2,4]triazole) and bis(9H-benzo[d]imidazo[1,2-a]imidazole) derivatives incorporating a thieno[2,3-b]thiophene moiety from the versatile and readily accessible 1,1'(3,4-dimethylthieno[2,3-b]thiophene-2,5-diyl)-bis(2-bromo-ethanone) (1) are described.     

Research on thiophenes

Thieno[2, 3-b]thiophene is prepared in a way similar to that previously described for the synthesis of thieno[3, 2-b]thiophene, the method being based on intramolecular condensation of methyl (3-formyl-2-thienylmercapto) acetate. The IR and PMR spectra of thieno[2, 3-b]-thiophene, 2-ethylthieno[2, 3-b] thiophene and 2-ethylthieno[3, 2-b]-thiophene are investigated.For Part IX see [13].     

A new route to annulated oligothiophenes

[reaction: see text] A new convenient method for the construction of thiophene-annulated thieno[2,3-b]thiophenes has been proposed. The key step of the method is ring closure of 10H-bisthienodithiocin-10-one by strong bases. The syntheses of two previously unknown annulated oligothiophenes, thieno[2,3-b]thieno[3',2':4,5]thieno[3,2-d]thiophene (1a) and thieno[3,2-b]thieno[2',3':4,5]thieno[3,2-d]thiophene (1b), have been described to illustrate the success of the method.     

Synthesis of Poly(3,4‐ethylenedioxythiophene) latexes using poly(N‐vinylpyrrolidone)‐based copolymers as reactive stabilizers

The synthesis by oxidative polymerization of well‐defined poly(3,4‐ethylenedioxythiophene) (PEDOT) nano‐objects in the presence of modified and unmodified poly(N‐vinylpyrrolidone)‐based copolymers used as stabilizers in aqueous media is reported. Ammonium persulfate or a mixture of ammonium persulfate with CuCl₂ or CuBr₂ was used as oxidants. The effects of several parameters such as the molar mass and the concentration of the stabilizer as well as the nature of the oxidants on the size, morphology, and the conductivity of the PEDOT particles have been investigated. The distribution of the reactive moieties along the copolymer stabilizer backbone was shown to be crucial to get well‐defined PEDOT nano‐objects. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3841–3855, 2010     

Fused pyrazolopyrimidines II. Thieno[3″,2″:5′,6′]pyrido[4′,3′:3,4]pyrazolo[1,5-a]pyrimidines

The reaction of 3-amino-1H-pyrazolo[3,4-d]thieno[2,3-b]pyridine with 1,3-dicarbonyl compounds and with ethoxy-methylene reagents gives the title ring system and its derivatives. The electrophilic substitutions occur in the thiophene ring of the system.