新型芳并吡喃类多环化合物的合成与光谱性质研究

本文设计并经由分子内碳-碳偶联反应合成了一系列基于芳并吡喃供电子功能片段的有机功能小分子,包括萘并[2,1-b：6,5-b’]二苯并吡喃4a,萘并[2,1-b：6,5-b’]二萘并吡喃4b,萘并[2,1-b：6,5-b’]二[2-（5-己基噻吩基）]苯并吡喃4c。通过紫外光谱和荧光光谱研究表明,这类化合物在370~400 nm波长范围内具有最大紫外吸收,在417~462 nm波长范围内具有最大荧光发射。说明随着共轭平面的增大或共轭链长度的增加,化合物的吸收和荧光光谱均发生显著的红移,是一类具有丰富光电活性的有机功能分子。     

Linear- and angular-shaped naphthodithiophenes: selective synthesis, properties, and application to organic field-effect transistors

A straightforward synthetic approach that exploits linear- and angular-shaped naphthodithiophenes (NDTs) being potential as new core structures for organic semiconductors is described. The newly established synthetic procedure involves two important steps; one is the chemoselective Sonogashira coupling reaction on the trifluoromethanesulfonyloxy site over the bromine site enabling selective formation of o-bromoethynylbenzene substructures on the naphthalene core, and the other is a facile ring closing reaction of fused-thiophene rings from the o-bromoethynylbenzene substructures. As a result, three isomeric NDTs, naphtho[2,3-b:6,7-b']dithiophene, naphtho[2,3-b:7,6-b']dithiophenes, and naphtho[2,1-b:6,5-b']dithiophene, are selectively synthesized. Electrochemical and optical measurements of the parent NDTs indicated that the shape of the molecules plays an important role in determining the electronic structure of the compounds; the linear-shaped NDTs formally isoelectronic with naphthacene have lower oxidation potentials and more red-shifted absorption bands than those of the angular-shaped NDTs isoelectronic with chrysene. On the contrary, the performance of the thin-film-based field-effect transistors (FETs) using the dioctyl or diphenyl derivatives were much influenced by the symmetry of the molecules; centrosymmetric derivatives tend to give higher mobility (up to 1.5 cm(2) V(-1) s(-1)) than axisymmetric ones (～0.06 cm(2) V(-1) s(-1)), implying that the intermolecular orbital overlap in the solid state is influenced by the symmetry of the molecules. These results indicate that the present NDT cores, in particular the linear-shaped, centrosymmetric naphtho[2,3-b:6,7-b']dithiophene, are promising building blocks for the development of organic semiconducting materials.     

Synthesis, structures, and properties of disubstituted heteroacenes on one side containing both pyrrole and thiophene rings

A new series of ladder-type heteroacenes containing both pyrrole and furan rings, 5,6-disubstituted diindolo[3,2-b:4,5-b']thiophenes (DITs), were effectively synthesized from N-functionalized 3,3'-dibromo-2,2'-biindoles undergoing intramolecular cyclization with bis(phenylsulfonyl) sulfide and organolithium. Single-crystal X-ray results demonstrate that 5,6-dipropyldiindolo[3,2-b:4,5-b']thiophene (4b) forms a herringbone-type of packing motif and 5,6-di(p-tolyl)diindolo[3,2-b:4,5-b']thiophene (4d) forms a parallel packing motif. Both of them have S-S contacts, enhancing the electronic transport between molecules. Their photophysical properties suggest that the skeleton of diindolo[3,2- b:4,5-b']thiophene is more favorable to aggregate in solid than that of indolo[3,2-b]carbazole. The large band gaps and low-lying HOMO energy levels could result in much better stability.     

Synthesis of ladder-type pi-conjugated heteroacenes via palladium-catalyzed double N-arylation and intramolecular O-arylation

Ladder-type heteroacenes containing pyrrole or furan rings, indolo[3,2-b]carbazoles and dibenzo[d,d']benzo[1,2-b:4,5-b']difurans, were effectively synthesized from the common intermediates, 2,5-bis(o-chloroaryl)hydroquinones. The key reactions are palladium-catalyzed double N-arylation of aniline and intramolecular O-arylation, which enable regioselective ring closure. In addition to the parent indolo[3,2-b]carbazole and dibenzo[d,d']benzo[1,2-b:4,5-b']difuran, their derivatives with an alkyl or cyano group were first synthesized. Photophysical and electrochemical studies showed that the obtained heteroacenes have lower HOMO energy levels and larger band gaps than the corresponding hydrocarbon acene, pentacene. An X-ray analysis of dibenzo[d,d']benzo[1,2-b:4,5-b']difuran revealed that it was packed in herringbone fashion.     

Synthesis of bridged oligothiophenes: toward a new class of thiophene-based electroactive surfactants

[structure: see text] A series of bridged oligothiophenes have been synthesized. Their novel molecular architecture, comprising two oligothiophenes linked together by a bridge at one alpha-extremity and one binding group at the other alpha-extremity, is expected to improve their utility as electroactive surfactants for semiconducting nanoparticles or organic electronics.     

A three-step synthetic approach to asymmetrically functionalized 4H-cyclopenta[2,1-b:3,4-b']dithiophenes

A convenient and efficient three-step route toward both symmetrically and asymmetrically functionalized 4H-cyclopenta[2,1-b:3,4-b']dithiophenes has been developed. Using this method a broad collection of functionalized bridged bithiophenes can smoothly be accessed. Starting from 3-bromo-2,2'-bithiophene, prepared by Kumada coupling of 2-thienylmagnesium bromide with 2,3-dibromothiophene under Pd(dppf)Cl(2) catalysis, lithiation and subsequent reaction with dialkyl ketones afforded (a)symmetrically dialkylated tertiary alcohol derivatives. By means of final Friedel-Crafts dehydration cyclization in sulfuric acid medium, these derivatives were converted to 4,4-dialkyl-4H-cyclopenta[2,1-b:3,4-b']dithiophenes. Upon replacement of the dialkyl ketone reagent by ethyl levulinate, an ester-functionalized 4H-cyclopenta[2,1-b:3,4-b']dithiophene was prepared, representing an attractive precursor for variously functionalized cyclopentadithiophene compounds.     

Synthesis and properties of novel thiophene-based conjugated homologues: 9,9-diphenylfluorene-capped oligothiophenes

[reaction: see text] A series of novel 9,9-diarylfluorene-capped oligothiophenes were synthesized by Suzuki coupling reactions in good yields. The color of the emissions can be controlled by varying the conjugation length of the oligothiophene core. The bulky and rigid terminal groups of the resulting oligomers are significantly beneficial for their high morphological and thermal stability. These new oligothiophenes exhibit intriguing reversible oxidation and reduction redox behavior.     

Synthetic applications of cyanoacetylated bisindoles: synthesis of novel cycloheptadiindoles, indolocarbazoles, and related aza analogues

Cyclization reactions involving cyanoacetylated bisindoles have been studied, providing access to various novel cyclohepta[2,1-b:3,4-b']diindole derivatives as well as some related fused pentacyclic systems. Treatment of 3-cyanoacetyl-2,3'-diindolylmethane with methanesulfonic acid gave 6-(cyanomethyl)indolo[3,2-b]carbazole in a good yield.     

Angular-shaped naphthodifurans, naphtho[1,2-b;5,6-b']- and naphtho[2,1-b;6,5-b']-difuran: are they isoelectronic with chrysene?

Although angular-shaped naphthodifurans, naphtho[1,2-b;5,6-b']- and naphtho[2,1-b;6,5-b']-difuran, are formally isoelectronic with chrysene as their thiophene counterparts, naphtho[1,2-b;5,6-b']- and naphtho[2,1-b;6,5-b']-dithiophene, the HOMO energy level of naphthodifurans is much higher than those of naphthodithiophenes and chrysene. The difference in electronic structure in the ground state can be explained by distinct electronic perturbation from the outermost aromatic rings.     

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 3,7-diiodo-2,6-di(thiophen-2-yl)benzo[1,2-b:4,5-b']difurans: functional building blocks for the design of new conjugated polymers

3,7-Diiodo-2,6-di(thiophen-2-yl)benzo[1,2-b:4,5-b']difurans are efficiently prepared by an iodine-promoted double cyclization. This new heterocyclic core is readily modified by the attachment of alkyl chains for improved solubility. The use of these compounds for the synthesis of new conjugated polymers is also reported.     

A Near-infrared Non-fullerene Acceptor with Thienopyrrole-expanded Benzo[1,2-b:4,5-b′]dithiophene Core for Polymer Solar Cells

A near-infrared non-fullerene acceptor(NFA) BDTIC, based on thienopyrrole-expanded benzo[1,2-b:4,5-b′]dithiophene unit(heptacyclic S,N-heteroacene) as core, is designed and synthesized. The aromatic pyrrole ring with strong electron-donating ability in the core enhances the intramolecular charge transfer effect, finely tunes the optical bandgap and absorption profile of BDTIC, and thus results in a narrowed optical bandgap(E_g~(opt)) of 1.38 eV and a near-infrared absorption to 900 nm. When BDTIC is paired with donor polymer PBDB-T to fabricate organic solar cells, the optimized device achieves a best power conversion efficiency of 12.1% with a short-circuit current density of 20.0 mA·cm~(-2) and an open-circuit voltage of 0.88 V. The photovoltaic performance benefits from the broad absorption, weak bimolecular recombination, efficient charge separation and collection, and favorable blend morphology. This work demonstrates that thienopyrroleexpanded benzo[1,2-b:4,5-b′]dithiophene unit(heptacyclic S,N-heteroacene) is a promising building unit to construct high-performance NFAs by enhancing the intramolecular charge transfer effect, broadening absorption as well as maintaining good intermolecular stacking property.     

A "zig-zag" naphthodithiophene core for increased efficiency in solution-processed small molecule solar cells

A solution-processed small molecule utilizing a novel 4,9-bis(2-ethylhexyloxy)naphtho[1,2-b:5,6-b']dithiophene "zig-zag" core (zNDT) exhibits high hole mobility, upshifted frontier MO energies, and enhanced photovoltaic cell short-circuit currents, fill-factors, and power conversion efficiencies (4.7%) versus the linear NDT isomer.     

Thin film organic transistors from air-stable heteroarenes: anthra[1,2-b:4,3-b':5,6-b':8,7-b']tetrathiophene derivatives

A facile synthesis of air-stable anthra[1,2-b:4,3-b':5,6-b':8,7-b']tetrathiophene derivatives 1a and 1b has been developed for applications in organic thin film transistors. Both molecules tend to self-associate through pi-pi stacking in solution and in different films. The hole mobility of 0.012 cm2 V(-1) s(-1) is obtained from 1a due to morphology changes in films from less ordered to highly ordered structures after thermal annealing. Good performance remained persistent over a period of 14 days, indicating the high stability of such transistors.     

Palladium-catalyzed double annulations to construct multisubstituted benzodifurans

Efficient synthetic routes to construct multisubstituted benzo[1,2-b:5,4-b']difurans and benzo[1,2-b:4,5-b']difurans from bis(allyloxy)bis(alkynyl)benzenes or bis(alkynyl)dihydroxybenzenes and allylic halides utilizing palladium-catalyzed double annulations is reported. By further applying a double ring-closing metathesis reaction, pentacyclic compounds were also prepared.     

π-Fused bis-BODIPY as a candidate for NIR dyes

Benzene-fused bis-(borondipyrromethene)s (bis-BODIPYs) were synthesized by retro-Diels-Alder reaction of the corresponding bicyclo[2.2.2]octadiene-fused (BCOD-fused) bis-BODIPYs, which were, in turn, prepared from 4,8-ethano-4,8-dihydropyrrolo[3,4-f]isoindole derivatives. The π-fused bis-BODIPY chromophores were designed to show intensive absorption and strong fluorescence in the near-infrared region and not to have any strong absorption in the visible region. A 6,10-dibora-5a,6a,9a,10a-tetraaza-s-indaceno[2,3-b:6,5-b']difluorene derivative (syn-bis-benzoBODIPY) obtained by a thermal retro-Diels-Alder reaction of the corresponding BCOD-fused BODIPY dimer has strong absorption and emission bands at 775 and 781 nm, respectively. The absolute quantum yield is 0.36. The absorption is more than 5.0 times stronger than other absorptions observed in the visible region. In the case of 6,15-dibora-5a,6a,14a,15a-tetraaza-s-indaceno[2,3-b:6,7-b']difluorene derivatives (anti-bis-benzoBODIPY), the absorption and emission maxima exceed 840 nm.     

Photoaddition reactions of acetylene and butadiyne derivatives to benzodithiophene

The photochemical [2pi +2pi] cycloaddition of dimethyl acetylenedicarboxylate to benzo[1,2-b:4,5-b']dithiophene has been used to synthesize substituted cyclobuta[b]thieno[2,3-f][1]benzothiophene. The first [2pi + 2pi] photocycloaddition reaction of a series of butadiynes to benzodithiophene is reported to yield regioselective and acetylene-substituted cyclobutene derivatives containing an aromatic thiophene moiety.     

Lewis acid adducts of narrow band gap conjugated polymers

We report on the interaction of Lewis acids with narrow band gap conjugated copolymers containing donor and acceptor units. Examination of the widely used poly[(4,4-bis(2-ethylhexyl)cyclopenta-[2,1-b:3,4-b']dithiophene)-2,6-(diyl-alt-benzo[2,1,3]thiadiazole)-4,7-diyl] (1) shows weaker binding with B(C(6)F(5))(3) when compared with a small molecule that contains a cyclopenta-[2,1-b:3,4-b']dithiophene (CDT) unit flanked by two benzo[2,1,3]thiadiazole (BT) fragments. Studies on model compounds representative of 1, together with a comparison between B(C(6)F(5))(3) and BBr(3), indicate that the propensity for Lewis acid coordination is decreased because of steric encumbrance surrounding the BT nitrogen sites. These observations led to the design of chromophores that incorporate an acceptor unit with a more basic nitrogen site, namely pyridal[2,1,3]thiadiazole (PT). That this strategy leads to a stronger B-N interaction was demonstrated through the examination of the reaction of B(C(6)F(5))(3) with two small molecules bis(4,4-bis(hexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-4,7-pyridal[2,1,3]thiadiazole (8) and bis{2-thienyl-(4,4-bis(hexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)}-4,7-pyridal[2,1,3]thiadiazole (9) and two polymer systems (poly[(4,4-bis(2-ethylhexyl)cyclopenta-[2,1-b:3,4-b']dithiophene)-2,6-diyl-alt-([1,2,5]thiadiazolo[3,4-c]pyridine)-4,7-diyl] (10) and poly[(4,4-bis(2-ethylhexyl)cyclopenta-[2,1-b:3,4-b']dithiophene)-2,6-diyl-alt-(4',7'-bis(2-thienyl)-[1,2,5]thiadiazolo[3,4-c]pyridine)-5,5-diyl] (11). From a materials perspective, it is worth pointing out that through the binding of B(C(6)F(5))(3), new NIR-absorbing polymers can be generated with band gaps from 1.31 to 0.89 eV. A combination of studies involving ultraviolet photoemission spectroscopy and density functional theory shows that the narrowing of the band gap upon borane coordination to the pyridal nitrogen on PT is a result of lowering the energies of both the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the optically relevant fragments; however, the LUMO is decreased to a greater extent, thereby giving rise to the narrowing of the gap.     

2,6-Diphenylbenzo[1,2-b:4,5-b']dichalcogenophenes: a new class of high-performance semiconductors for organic field-effect transistors

2,6-Diphenylbenzo[1,2-b:4,5-b']dichalcogenophenes including thiophene, selenophene, and tellurophene analogues as organic semiconductors for field-effect transistors were effectively synthesized in three steps from commercially available 1,4-dibromobenzene. All three benzodichalcogenophenes acted as good p-type semiconductors, and particularly the selenophene analogue, 2,6-diphenylbenzo[1,2-b:4,5-b']diselenophene, showed high FET mobility of 0.17 cm2 V-1 s-1.     

A-D-A-D-A-type oligothiophenes for vacuum-deposited organic solar cells

Novel A-D-A-D-A-type oligothiophenes incorporating electron-withdrawing benzo[c][1,2,5]thiadiazole (BTDA) as core and trifluoroacetyl (TFA) as terminal acceptor groups have been developed. Vacuum-processed planar heterojunction organic solar cells incorporating these new oligomers as donor and C(60) as acceptor showed very high open circuit voltages up to 1.17 V, resulting in power conversion efficiencies of 1.56% under AM1.5G conditions.