New alkoxy-functionalized naphthodithiophene-based semiconducting oligomers and polymers

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DOI: 10.1002/ijch.201400046

New Alkoxy-Functionalized Naphthodithiophene-Based

Semiconducting Oligomers and Polymers

Chun Huang,* Yan Hu, Yan Zheng, Martin Drees, Hualong Pan, and Antonio Facchetti*^[a]

In memory of Michael Bendikov, a good friend and excellent chemist

Abstract: We report the syntheses and characterization of

two bent dialkoxy-substituted naphthodithiophene (bNDT)

isomers as well as of the corresponding bNDT-based small

molecule and polymer semiconductors for organic field-

effect transistors and organic photovoltaics. The bNDT-

based building blocks exhibit improved oxidation potential

and photo- and air stability versus the benzodithiophene

and linear naphthodithiophene counterparts. Incorporation

of the dialkoxy substituents enables film fabrication from so-

lution and control of the molecular solid-state packing.

Among these semiconductors, the polymer P1 exhibits good

hole field-effect mobility of about 0.4 cm²Vs^ꢀ1with I_on/I_off>

10⁴for low-temperature annealing. These results indicate

that bNDT is a promising building block for optoelectronic

semiconducting materials.

Keywords: donorꢀacceptor systems · oligomers · photochemistry · polymers · semiconductors

1 Introduction

Organic semiconductors have been attracting great re-

search attention for the realization of large-area, flexible

optoelectronic devices using solution-based processing

methodologies, such as spin-coating, blade coating, slot-

die coating, and printing.^[1]Since their introduction into

electronic devices in the late 20th century, remarkable

progress has been made in understanding organic semi-

conductor-based device operation mechanisms, engineer-

ing of the device architecture, and developing new organ-

ic semiconductor chemistries for improving device per-

formances. Among the optoelectronic devices pursued for

flexible electronics, organic field-effect transistors

(OFETs) and organic photovoltaics (OPVs) have been by

far the most popular.^[2]As far as the development of new

organic semiconducting cores is concerned, building

blocks such as acenes,^[3]oligo/fused chalogenophenes,^[4]

and rylenes^[3a,5]have received paramount attention for or-

ganic thin-film transistors (OTFTs) and OPVs, as illus-

trated in Figure 1. Particularly, sulfur-based p-conjugated

moieties have been implemented as major components of

the p core or as a co-unit for the realization of several

semiconductor classes. Indeed the best hole-transporter/

donors^[2d,f,6]and electron-transporter/acceptors^[5d,7]for

OTFT and OPV organic semiconductors do contain

a sulfur atom. On the other hand, the use of oxygen-

based semiconductors has been far more limited. Bendi-

kov et al. pioneered the use of furan-based semiconduc-

tors for OFETs, whereas oxygenated substituents have

been mainly employed in functionalizing phenylenes and

oligothiophenes to improve solution processability.^[8]Re-

cently, research on using oxygen-substituted side chains

on the semiconductor backbones also achieved great

progress in offering high-performance materials for opto-

electronic devices by controlling the molecular co-planari-

ty and solid-state packing.^[9]

Currently, one of the most promising strategies to pro-

mote strong intermolecular interactions in organic semi-

conductors employs the main-chain donorꢀacceptor

design, in which the conjugated semiconducting polymer

or small molecule comprise an electron-rich donor unit

(D) and an electron-deficient acceptor unit (A) linked

through a chemical bond or by a spacer group.^[4b,10]Fur-

thermore, this approach enables fine-tuning of the fron-

tier molecular orbitals (FMOs) as well as thin-film micro-

structures; both are critical parameters for optimal charge

carrier transport. Among several donor building blocks

currently under investigation, benzo[1,2-b:4,5-b’]dithio-

phene (BDT) and its derivatives are promising candi-

dates, since core fusion and the symmetric structure of

such units enables a high degree of backbone planarity,

good solid-state intermolecular registry, and tight inter-

molecular packing, which would benefit charge carrier

transport in the solid state and charge carrier collection

[a] C. Huang, Y. Hu, Y. Zheng, M. Drees, H. Pan, A. Facchetti

Polyera Corporation, Suite 140

8045 Lamon Ave, Skokie, IL, 60077 (USA)

e-mail: chuang@polyera.com

afacchetti@polyera.com

a-facchetti@northwestern.edu

Supporting information for this article is available on the WWW

under http://dx.doi.org/10.1002/ijch.201400046.

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Figure 1. Some promising organic semiconductors for OFET and OPV research.

in the metal/organic interface.^[6c,11]For example, organic

solar cells with power conversion efficiencies (PCEs) ap-

proaching 10% have been demonstrated using materials

of this type, both polymeric and small molecular materi-

als, recently.^[12]Furthermore, p-channel OFETs using

BDT-based semiconductors with high-charge carrier mo-

tilities have been achieved by several research group-

s.^[11a,13]

(NDT) and anthodithiophene (ADT)-type conjugated

materials and excellent performances have been achieved

in both OTFTs and OPVs.^[16]However, it is likely that

such organic semiconductors might suffer from similar

stability issues to those of BDT-based materials, as illus-

trated in Figure 2, regarding to their chemical structur-

es.^[16f,g]

Aiming to provide p-conjugated units with better

photo-stability than those of BDTs and their p-extended

linear derivatives, we proposed a bent molecular architec-

Another key requirement for commercially relevant

applications, particularly for the OPV semiconductors, is

chemical stability during operation, considering that the

active materials are exposed to air and solar light simulta-

neously during device fabrication and/or operation. As il-

lustrated in Figure 2, typical benzo-/thieno-fused donor

units, such as BDT, anthracene, and other n-acene deriva-

tives, are known to react with photo-generated singlet

oxygen in ambient conditions to give cycloadducts that

create p-insulating linkage points in the conjugated

unit,^[14]which will result in significant device performance

degradation. This process has been investigated by Tao

and co-workers recently for BDT-based low band gap Dꢀ

A alternating copolymers.^[15]They reported that the BDT

unit underwent dramatic structural change under illumi-

nation in air, leading to the disruption of the polymer

main-chain conjugation and degradation of the electro-

optical properties. Thus, it was concluded that this photo-

sensitivity was one of the key factors that limited the use

of BDT-based materials. Recently, great progress has

been made in developing linear naphthodithiophene

Figure 2. Possible mechanism of BDTs, acenes, and their deriva-

tives that undergo cycloaddition with singlet oxygen.

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Figure 3. Possible mechanism of the reaction of BDTs, linear NDTs, and bent NDT cycloaddition with singlet oxygen and the respective aro-

maticity loss.

ture comprising naphthalene fused with two thiophene

rings.^[17]This donor unit may be less sensitive to cycload-

dition of dioxygen because of the different molecular ring

arrangement. In fact, unlike functionalized BDT and

linear NDT and ADT units, for which upon cycloaddition

of O₂only the aromaticity of one ring is lost (Figure 3),

two aromatic rings in bent NDTs will simultaneously lose

aromaticity upon reacting with O₂; this makes this pro-

cess far more endoergonic. The expected large activation

energy (breaking two aromatic rings during the photo-

triggered cycloaddition) may prevent/limit the cycloaddi-

tion of singlet oxygen from occurring and make the corre-

sponding bNDI-based organic semiconductors more

stable. Also, the bent structures of the NDT could effec-

tively increase the respective ionization potential and oxi-

dation potential compared with linear NDT because of

the cross-conjugation in such building blocks,^[16d]which

was expected to benefit the material stability.

Recently, a few contributions have highlighted the po-

tential of bent NDT-based semiconductors^[18]and the dif-

ferent isomers that could be derived.^[19]Herein, we report

the synthesis, characterization, and stability of two new

alkoxy-substituted bent NDT building blocks as well as

their implementation into new molecular and polymeric

semiconductors, as illustrated in Figure 4. From the syn-

thetic front, a new approach to developing efficient

routes to alkoxy-substituted bNDTs is discussed, which

could benefit the screening of bNDT-based semiconduc-

tors with various alkoxy side chains. Finally, we report ini-

tial results for their charge-transport characteristics in

Figure 4. Conjugated materials based on bNDTs studied in this work and a related BDT polymer from the literature.

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OFETs and the performance of a polymer as a donor ma-

terial in OPV cells as a blend with a soluble fullerene.

for the first time, to enable the synthesis of bNDT build-

ing blocks with the desired long or branched alkoxy side

chains. The incorporation of such alkoxy side chains is ex-

pected to enhance bNDT-based semiconductor solubility

and solution processability for electronic devices. An im-

portant advantage of this synthetic strategy is to avoid

the tedious and low yield (typically <20%) cyclo-con-

densation reaction for forming linear and bent NDTs car-

rying long/branched alkoxy side chains.^[16a,18b]Table 1 sum-

marizes the reaction conditions for the trans-alkoxylation

reactions from bBNDT1OMe or bNDT2OMe to the cor-

responding bNDT1OR or bNDT2OR, respectively. Here,

by utilizing typical trans-alkoxylation conditions em-

ployed for 3-methoxythiophene, which uses p-toluenesul-

fonic acid (TsOH; 10 mol% to the substrate) as the cata-

lyst, affords products in very poor yields (<5%) for both

bNDT isomers.^[9a]It was also found that using stronger

acids as the catalyst (e.g., chlorosulfonic acid) did not im-

prove the bNDT trans-alkoxylation reaction yields, but

caused decomposition of the bNDT substrates. However,

by raising the reaction temperature, carrying out the reac-

tion without solvent, and increasing the acid to bNDT

substrate molar ratio the reaction yields can be signifi-

cantly improved and the optimized conditions afford the

products in >65% yield for several high-molecular-

weight alcohols (such as C₁₀H₂₅OH and C₁₂H₂₅OH). Thus,

the optimized reactions were carried out in neat alcohol

at about 2008C with about 50 mol% of TsOH. Further in-

creasing the amount of acid did not improve the yields of

the respective trans-alkoxylation. The corresponding dis-

tannyl-bNDT monomers (bNDT1OR-Sn2 or bNDT2OR-

2 Result and Discussion

2.1 Monomer, Oligomer, and Polymer Syntheses

The two isomeric bNDT building blocks with various

alkoxy substituents (bNDT1OR and bNDT2OR) were

designed and synthesized in reasonable yields according

to Scheme 1. The precursors to the longer alkoxy-func-

tionalized systems, bBNDT1OMe and bNDT2OMe, were

synthesized by following the cyclo-condensation reaction

reported in our previous work.^[16a,18b]The synthesis of

bNDT1OMe initiated by lithiation of 1,5-dibromo-4,8-di-

methoxynaphthalene using n-butyllithium and trapping

with 1,2-bis(2,2-diethoxyethyl) disulfide to provide Precu-

sor1 in good yields (62%). An acid catalytic (PPA) con-

densation was then applied on Precusor1 to perform the

cyclo-condensation to offer bNDT1OMe in high yields

(86%). For the synthesis of bNDT2OMe, the lithiation

reaction was carried out on 2,6-dimethoxynaphthalene

with n-butyllithium, instead of the respective dibromo de-

rivatives, following the addition of an excess 1,2-bis(2,2-

diethoxyethyl) disulfide to afford Precusor2 in 52% yield.

Then bNDT2OMe was synthesized in a yield of about

66% following acid catalytic condensation from Precu-

sor2.

As illustrated in Scheme 2, an acid-catalyzed trans-al-

koxylation reaction^[9a]on the methoxy-functionalized

bNDTs (bNDT1OMe and bNDT2OMe) was carried out,

Scheme 1. Synthesis of bBNDT1OMe and bNDT2OMe. NBS=N-bromosuccinimide, PPA=polyphosphoric acid.

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Scheme 2. Synthesis of the distannyl bNDT monomers and mono-functionalized bNDTs.

Table 1. Summary of the conditions for the trans-alkoxylation reactions of bNDT1OMe and bNDT2OMe.

NDTs

Acid ([mol%])

Solvent

Alcohol ([equiv])

T [8C]

Yield [%]

Product

bNDT1OMe

bNDT2OMe

bNDT1OMe

bNDT2OMe

TsOH (10)

ClSO₃H (10)

TsOH (10)

TsOH (20)

TsOH (50)

TsOH (100)

TsOH (50)

toluene

o-xylene

none

1-dodecanol (5)

1-dodecanol (>20)

1-decanol (>20)

1-dodecanol (>20)

2-butyl-1-octanol (>20)

1-dodecanol (>20)

2-butyl-1-octanol (>20)

110

140

200

<5

bNDT1ODD

bNDT2ODD

bNDT1ODD

bNDT1ODC

bNDT1ODD

bNDT1OBO

bNDT2ODD

bNDT2OBO

decomposed

20–30

ꢁ40

60–70

60–80

ꢁ90

none

ꢁ70

Sn2) were synthesized in high yields (80–90%) using the

conventional lithiation/stannylation of bNDT1ODD,

bNDT1OBO, bNDT2ODD, and bNDT2OBO. The suc-

cessful development of such distannyl compounds enables

the synthesis of high-molecular-weight bNDT-based con-

jugated polymers by Stille coupling polycondensation.^[20]

Furthermore, the mono-substituted bNDT1ODD-X

building blocks (X=BPin, Br) were also synthesized in

satisfactory yields (32 and 58%, respectively).

bNDT1ODD-BOR was made via mono-lithiation of

bNDT1ODD with n-butyllithium and quenching with 2-

isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, while

bNDT1ODD-Br was synthesized via the bromination of

bNDT1ODD with N-bromosuccinimide (NBS). The suc-

cessful synthesis of the mono-functional BNDTs will

enable the development of bNDT-based oligomers for

electronic applications (see below).

The synthesis of bNDT1ODD-based DꢀAꢀD-triads

(Ter1 and Ter3) and D₂ꢀD₁ꢀD₂-type triad (Ter2) and

the longer DꢀAꢀDꢀAꢀD-type oligomer (Penta1) were

achieved via Suzuki coupling condensation,^[21]as illustrated

in Scheme 3. The syntheses for these triads were straight-

forward and afforded Ter1, Ter2, and Ter3 in 43, 64, and

51% yield, respectively, after column chromatography

purification. The synthesis of Penta1 was carried out in

two steps, first by reacting bNDT1ODD-Sn2 with an

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Scheme 3. Synthesis of bNDT1ODD-based oligomers Ter1, Ter2, Ter3, and Penta1.

excess of 4,7-dibromooctylisoindoline-1,3-dione to afford

the intermediate, Br-PI-NDT1-PI-Br, in good yield

(ꢁ50%); this was further converted into Penta1 by Suzuki

coupling condensation with satisfactory yield (45%) after

column chromatography purification. Among these oligo-

mers, Ter1 exhibits superior solubility in common organic

solvents, such as CH₂Cl₂, CHCl₃, THF, and toluene.

Moreover, the solubility of Ter2 and Ter3 is at least 10

times lower than that of Ter1, possibly due to better pla-

narity along the molecular backbones for Ter2 and Ter3

than that of Ter1 (see Table S1 in the Supporting Informa-

tion,).^[9c,22]Ter2 is slightly less soluble than Ter3, possibly

owing to greater conjugation and the lack of a solubilizing

alkane group on the bithiophene unit, compared with

Ter3. The longer oligomer, Penta1, also shows good solu-

bility in common organic solvents, which is similar to Ter1.

Scheme 4 outlines the synthesis of the new conjugated

copolymers based on the two bNDTs. Here, the phthali-

mide-,^[9a]dithiophene-, thienoimide-,^[22,23]and benzothia-

diazole-based^[24]dibromo monomers were prepared as de-

scribed in the literature or obtained through commercial

sources. The copolymers were then achieved through

a palladium-catalyzed Stille coupling between the dibro-

mo monomers and bNDT1DD-Sn2, bNDT1BO-Sn2, and

out at 1308C, proceeded well, except for the synthesis of

P3 and P5, for which precipitates formed during polymer-

ization and no further purification and characterizations

were carried on these two polymers. Both copolymers P1

and P2 show relatively good solubility in common organic

solvents, such as toluene, xylene, chlorobenzene, and

CHCl₃. P1 and P2 show a high weight-average molecular

weight of (37.0 and 102.9 kD, respectively) and small

polydispersity (1.5 and 2.6, respectively) using THF-based

gel permeation chromatography (GPC) at room tempera-

ture. The polymers P3–P6 are typically less soluble than

P1 and P2, which could be attributed to the improved co-

planarity between the alternative building blocks in the

polymer main chain. This result is consistent with the red-

shifted absorption spectra and lower solubility of oligo-

mers Ter2 and Ter3 relative to Ter1 and Penta1. Polymers

P2, P4, and P6, containing branched alkoxy side chains,

are somehow more soluble than their respective counter-

parts with linear alkoxy side chains (P1, P3, and P5).

Both P6, containing bNDT1OBO as the donor unit and

thieno[3,4-c]pyrrole-4,6-dione (TPD) as the acceptor unit,

and P7, containing bNDT2OBO as the donor unit and

4,7-dithiophen-2,1,3-benzothiadiazole (DBT) as the ac-

ceptor unit, illustrated a high weight-average molecular

weight (76.9 and 117.7 kD, respectively) and small poly-

dispersity (1.8 and 1.5, respectively) using THF-based

GPC at room temperature.

bNDT2BO-Sn2, using

a

Pd₂dba₃/tri-o-tolylphosphine

system (3 mol% Pd catalyst with respect to bNDT mono-

mers) as the metal source. The polymerizations, carried

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Scheme 4. Synthesis of bNDT1- and bNDT2-based copolymers. dba=dibenzylideneacetone.

2.2 Molecular and Solid-State Properties

ence (3.3 eV) and then bNDT2OMe (3.4 eV). Interesting-

To compare the properties of bNDT versus BDT building

blocks, the optical and electrochemical behavior and the

stability of these systems were investigated. First, the H

ly, bNDT2OMe has the widest optical band gap in solu-

tion, despite the larger p conjugation than that of

BTDOMe, while bNDT1OMe shows a similar band gap

to that of BTDOMe, which indicates that using an iso-

meric structure of alkoxy-substituted bNDT could signifi-

cantly alter the electronic structure and opticalꢀelectrical

1

NMR spectra (in CDCl₃) were used to monitor the com-

parative storage and photo-stability of bNDT1OMe,

bNDT2OMe, and 4,8-bis(methoxy)benzo[1,2-b:4,5-b’]di-

thiophene (BTDOMe). As shown in Figure S1 in the Sup-

porting Information, there was no significant change for

1

the H NMR spectra of bNDT1OMe and bNDT2OMe

after the respective solutions in CDCl₃were stored for 6

days avoiding light or under simulated solar light (AM

1.5) for 18 h. On the other hand, there are additional sig-

1

nals growing at dꢁ7.8 ppm in the H NMR spectrum of

BTDOMe when the samples were stored under similar

conditions. The UV/Vis absorption spectra of these com-

pounds in dichloromethane are shown in Figure 5A.

There is about a 19 nm blueshift for the longest wave-

length transition (l_max) upon going from bNDT1OMe

(365 nm) to bNDT2OMe (356 nm), whereas that of

BDTOMe is located at 348 nm. From the onset of the ab-

sorption, bNDT1OMe shows the smallest optical band

gap (3.3 eV), followed by BTDOMe with a small differ-

Figure 5. A) Normalized UV/Vis absorption spectra of bNDT1OMe,

bNDT2OMe, and BTDOMe in CH₂Cl₂at a concentration of about

1ꢀ10^ꢀ5M. B) Cyclic voltammograms of bNDT1OMe, bNDT2OMe,

and BTDOMe in CH₂Cl₂with a scan rate of 50 mVs^ꢀ1using ferro-

cene as an internal reference.

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properties of the respective conjugated polymers. This

result is in agreement with the finding by Takimiya et al.

on non-substituted NDT, linear and/or bent conjugated

polymers.^[16c,18d]It was found that bNDT-based polymers

exhibited better mobilities in OFETs than those of the

linear NDT derivatives; this is contradictory to small-

molecule systems. Meanwhile, the isomeric bent NDT-

based polymers also offer different types of microstruc-

tures in the thin film due to the molecular shapes and the

FMO geometry, which also results in quite different

charge-transport properties of such polymers. Moreover,

the two alkoxy-substituted bNDT compounds might also

possess more rigid structures when compared with

BTDOMe, since their absorption spectra in solution show

much clearer vibronic fine-structure features.

Figure 6. A) Normalized UV/Vis absorption spectra of bNDT1-

based oligomers in CHCl₃at a concentration of about 1ꢀ10^ꢀ5M. B)

Cyclic voltammograms of bNDT1-based oligomers in CH₂Cl₂with

a scan rate of 50 mVs^ꢀ1using ferrocene as an internal reference.

The comparative redox properties of the bNDTs and

BDT were investigated using cyclic voltammetry (CV) in

anhydrous dichloromethane, with tetra-n-butylammonium

hexafluorophosphate as the supporting electrolyte and

ferrocene (FeCp₂) as the internal reference. The cyclovol-

tammograms shown in Figure 5B indicate that all units

exhibit reversible oxidation features. The half-wave po-

tentials corresponding to molecular oxidation (E_1/2^0/+) of

bNDT1OMe to bNDT2OMe and BTDOMe, are similar

and located at 0.63, 0.58, and 0.43 V. BTDOMe is slightly

more readily oxidizable than bNDT1OMe and

bNDT2OMe (by ca. 0.2 eV), which suggests that the

newly developed bNDTs could be more photo-stable.

Indeed, Anthony and co-workers found that using elec-

tron-withdrawing substituents (e.g., F atoms and cyano

groups) to increase the oxidation potential of ADT semi-

conductors enhanced their photo-stability.^[16f,g]This result,

in combination with the greater aromaticity loss upon re-

action with dioxygen, is in agreement with less sensitivity

to ambient atmosphere and photo-oxidization of

bNDT1OMe to bNDT2OMe than that of BTDOMe.

From the electrochemistry data and optical band gap, the

respective highest occupied molecular orbitals (HOMOs)

and lowest unoccupied molecular orbitals (LUMOs) of

the two bNDT isomers and the BDT were estimated and

the data are collected in Table 2.^[25]

Table 3. The estimated optical band gaps and energy levels of re-

spective FMOs of the bNDTs oligomers and polymers.

+/0[a]

Material

E_1/2

[V]

HOMO

[eV]

LUMO^[c]

[eV]

l_max

[nm]

E_gap

(optical) [eV]

Ter1

Ter2

Ter3

Penta1

P1

P2

P4

P6

P7

+0.56^[b]

+0.20^[b]

+0.42^[b]

+0.50^[b]

+0.33^[b]

+0.34^[b]

N.A.

ꢀ5.4

ꢀ5.0

ꢀ5.2

ꢀ5.3

ꢀ5.1

N.A.

ꢀ5.3

ꢀ5.2

ꢀ3.0

ꢀ2.7

ꢀ3.0

ꢀ2.9

N.A.

ꢀ3.3

ꢀ3.4

419

444

488

451

466

472

508

576

590

2.4

2.3

2.2

2.3

2.2

2.1

2.0

1.8

+0.53^[b]

+0.42^[b]

[a] Redox potential versus FeCp₂^+/0. [b] Partially reversible oxidation.

[c] LUMO=ꢀ(ꢀHOMOꢀE_gapoptical).

mum at 419 nm, which is blueshifted by about 25 nm

when compared with the same transition for Ter2

(444 nm). This result can be attributed to the reduced

core planarity as a result of the larger torsional angle be-

tween the bNDT and phthalimide units. Going from Ter1

to the longer oligomer, Penta1, a redshift of about 32 nm

was observed for the pꢀp* transition (451 nm), which was

due to the extended conjugation. Ter3 shows the lowest

pꢀp* transition maximum at 488 nm (ꢁ70 nm redshifted

from Ter1), which could be explained by the excellent

core planarity and significant charge-transfer characteris-

tic between the bNDT and TPD units. Notably, with the

exception of Ter2, all of these oligomers exhibit some

degree of DꢀA charge-transfer-type absorption, with two

electronic transitions in the respective absorption spectra.

From the onset of the absorption, the optical gap of these

oligomers are estimated at 2.3 eV for Penta1, 2.4 eV for

Ter1, 2.3 eV for Ter2, and 2.2 eV for Ter3, respectively.

The smallest optical band gap for Ter3 could be attribut-

ed to the combination effect from good main-chain pla-

narity and significant charge-transfer characteristics be-

tween the bNDT (donor) and TPD (acceptor) units.

The UV/Vis absorption spectra of dilute solutions of

the four small-molecule semiconductors in CHCl₃(ca. 1ꢀ

10^ꢀ5M) are shown in Figure 6A and the data are collect-

ed in Table 3. Here, Ter1 shows the pꢀp* transition maxi-

Table 2. The estimated optical band gaps and energy levels of re-

spective FMOs of the bNDTs and BDT.

+/0[a]

Material

E_1/2

HOMO^[b]LUMO^[c]l_maxE_gap

[V]

[eV]

[nm] (optical) [eV]

bNDT1OMe 0.63

bNDT2OMe 0.58

ꢀ5.4

ꢀ5.2

ꢀ2.1

ꢀ2.0

ꢀ1.9

365

354

348

3.3

3.4

3.3

BDTOMe

0.43

[a] Redox potential versus FeCp₂^+/0. [b] HOMO=ꢀe(E_1/2^0/++4.8).

[c] LUMO=ꢀ(ꢀHOMOꢀE_gap).

The redox properties of Ter1, Ter2, Ter3, and Penta1

were investigated using CV in anhydrous dichlorome-

Isr. J. Chem. 2014, 54, 796 – 816

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thane, with tetra-n-butylammonium hexafluorophosphate

as the supporting electrolyte and ferrocene (FeCp₂) as the

internal reference. The cyclovoltammograms shown in

Figure 6B indicate that all units exhibit reversible/partial-

ly reversible oxidation features and no reduction features

were observed. The half-wave potentials corresponding to

molecular oxidation (E_1/2^0/+) of Ter1, Ter2, Ter3, and

Penta1 are located at +0.56, +0.20, +0.42, and +0.50 V,

respectively. Ter2 is slightly more readily oxidizable than

Ter1 and Ter3 (by ca. 0.2–0.3 eV), possibly due to the in-

corporated electron-rich bisthiophene unit, which lowers

the respective oxidation potential. As the main-chain

length increases from Ter1 to Penta1, the oligomers

become slightly easier to oxidize, possibly because of the

extension of the p conjugation. The HOMOs of these

oligomers were estimated to be ꢀ5.3, ꢀ5.4, ꢀ5.0, and

ꢀ5.2 eV for Penta1, Ter1, Ter2, and Ter3, respectively, as-

suming HOMO=ꢀe(E_1/2^0/++4.8) (eV).^[25]The LUMOs

were estimated to be ꢀ3.0, ꢀ3.0, ꢀ2.7, and ꢀ3.0 eV for

Penta1, Ter1, Ter2, and Ter3, respectively, assuming

LUMO=ꢀ(ꢀHOMOꢀE_gap) because no clear reduction

features were observed in the analysis windows.

The UV/Vis absorption spectra of dilute solutions of

P1, P2, P6, and P7 in chloroform (ca. 1ꢀ10^ꢀ5M) and on

glass (eagle 2000) are shown in Figure 7A. Notably, the

poor solubility of the other polymers prevents further

studies. With the exception of P6, all the remaining poly-

mers show a redshifted absorption in thin films versus

those recorded in dilute solution. In chloroform, the pꢀ

p* transition of the bNDT1-phthalimide polymer P1 has

a maximum at 467 nm, which is comparable to the same

transition of P2 (472 nm), and is reasonable considering

the similar chemical structure of these two polymers.

Such an electronic transition for P1 is redshifted by about

15 and 47 nm compared with the corresponding transition

for structurally similar oligomers Penta1 and triad Ter1,

respectively. The redshift of the absorption going from

Ter 1 to Penta1, to P1 in this homologous series is attrib-

uted to the further extended p conjugation of the back-

bone and possibly from the cooperative contribution of

the DꢀA electronic coupling. The thin-film absorption

spectra of both P1 and P2 are significantly redshifted rel-

ative to the solution ones, which could be attributed to

polymer backbone planarization and molecular pꢀp

stacking in the solid state. The absorption shoulder of the

branched-substituted P1 thin film located at 528 nm indi-

cates improved stacking than that for P2, probably as

a result of the reduced steric demand of the linear side

chain. The optical band gaps for P1 and P2 are about

2.2 eV, as estimated from the solution absorption edge.

This optical behavior of P1 and P2 is in line with those of

other alkoxyBDT-/phthalimide-based alternating copoly-

mers reported in the literature,^[26]which illustrated a solu-

tion absorption maximum at about 470 nm and optical

band gaps of about 2.1–2.2 eV. Because of the very poor

solubility, the optical absorption of P4, the copolymer of

bNDT1OBO and T2, was recorded in o-dichlorobenzene

(DCB) at elevated temperature (>508C, see Figure S3 in

the Supporting Information). This polymer absorption

has a maximum at 508 nm with a band gap of about

2.1 eV.

Interestingly, the bNDT1-thienoimide polymer P6 ex-

hibits a very similar optical absorption in solution and as

a thin film, with l_maxꢁ574 nm and a vibronic shoulder at

about 530 nm. Note that the maximum absorption of P6

in solution is redshifted by about 100 nm compared with

the corresponding phthalimide-based polymers P1 and

P2; this clearly indicates that the P6 backbone is already

substantially planar in solution. Thus, the minimal batho-

chromic shift of P6 versus P1/P2 combined with the negli-

gible variation of the absorption on going from solution

to the solid state indicate that this polymer is already sub-

stantially aggregated in CHCl₃at room temperature.

Thus, morphological rearrangement of the polymer

chains after film deposition from solution may be very

difficult for low-temperature annealing, which might limit

its charge-transport capability. The optical band gap for

P6 is about 2.0 eV, as estimated from the absorption

edge. The optical properties of P6 are in agreement with

work by Li et al. on a similar polymer with different side

chains, which has a maximum absorption at 578 nm, a vi-

bronic shoulder absorption at 535 nm, and a band gap of

Figure 7. A) Normalized UV/Vis absorption spectra of selected bNDT-based polymers in CHCl₃(at the concentration of ꢁ1ꢀ10^ꢀ5M) and

on glass films (prepared by spin-coating). B) Cyclic voltammograms of bNDT-based polymer films on an electrode in acetonitrile with

a scan rate of 50 mVs^ꢀ1using ferrocene as an external reference.

Isr. J. Chem. 2014, 54, 796 – 816

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about 2.0 eV.^[18f]Finally, the polymer P7, based on the

bNDT2 building block as a donor unit and dialkylthio-

phene-benzothiadiazole as an acceptor unit, exhibits

a broader visible absorption and narrower optical band

gap in the polymer series. Thus, the absorption has a maxi-

mum at 590 nm in solution with an optical band gap of

about 1.8 eV. The broader absorption bands and lower

optical band gap of P7 are favorable for its application in

polymer solar cells.

2.3 Charge-Transport Measurements

The charge-transport properties of the new semiconduc-

tors were evaluated in a bottom-contact top-gate transis-

tor architecture (Figure 8A). The thin-film transistors

(TFTs) were fabricated on glass substrates coated with

a 200 nm thick planarizing layer of a cross-linkable poly-

mer (B2000, Polyera Corp.).^[27]Gold source/drain electro-

des were deposited by thermal evaporation to define de-

vices with a channel length of 50 mm and a channel width

of 500 mm followed by a thiol treatment using pentafluor-

obenzothiol for better contact and charge injection. Next,

the semiconductors were spin-coated in ambient condi-

tions from the appropriate solution (see the Experimental

Section) and annealed at 110–1508C for 5 min to 10 h

before depositing the gate insulator (Cytop or PMMA)

by spin-coating. The thickness of the organic semiconduc-

tor layer was about 50 nm and that of the gate dielectric

was between 500 and 800 nm. The device was completed

by vapor deposition of the gold gate contact. All meas-

urements were performed in ambient conditions and the

field-effect transistor (FET) data are collected in Table 4.

To allow comparison with other OFETs, mobilities (m)

were calculated by standard FET equations. In traditional

metalꢀinsulatorꢀsemiconductor FETs (MISFETs), there

is typically a linear and saturated regime in the I_DSversus

V_DScurves at different V_G(in which I_DSis the sourceꢀ

drain saturation current, V_DSis the potential between the

source and drain, and V_Gis the gate voltage). At large

V_DS, the current saturates and is given by Equation (1):

The redox properties of P1, P2, P6, and P7 films were

investigated using CV in anhydrous acetonitrile, with

tetra-n-butylammonium hexafluorophosphate as the sup-

porting electrolyte and ferrocene (FeCp₂) as the external

reference. The cyclovoltammograms shown in Figure 7B

and the onset potentials corresponding to polymer oxida-

tion (E^0/+) for P1, P2, P6, and P7 are located at +0.33,

+0.34, +0.53, and +0.42 V, respectively. The HOMOs of

these polymers were estimated to be ꢀ5.1, ꢀ5.1, ꢀ5.3,

and ꢀ5.2 eV for P1, P2, P6, and P7, respectively, assum-

ing HOMO=ꢀe(E^0/++4.8) (eV). The LUMOs were esti-

mated to be ꢀ2.9, ꢀ2.9, ꢀ3.3, and ꢀ3.4 eV for P1, P2,

P6, and P7, respectively, assuming LUMO=ꢀ(ꢀHO-

MOꢀE_gap). Here, P1 and P2 show higher HOMOs and

LUMOs than the reported FMO energies of alkoxy-

BDT/phthalimide (poly(BDT-PI))-based alternating co-

polymers (ꢀ5.51 and ꢀ3.36 eV, respectively, for HOMO

and LUMO).^[26]Unsurprisingly, P6 exhibits similar redox

characteristics and FMO energies (ꢀ5.38 and ꢀ3.43 eV

for HOMO and LUMO, respectively) to those of struc-

turally similar bNDT polymers reported by Takimiya

et al., but with different side chains.^[18f]The HOMO and

LUMO for P7 are ꢀ5.2 and ꢀ3.4 eV, which are in agree-

ment with the BDT-based analogue polymer (poly(BDT-

DBT) illustrated in Figure 4; ꢀ5.2 and ꢀ3.5 eV respec-

tively), although the band gap is slightly larger (ca.

0.1 eV).^[24]

2

ð1Þ

ðI_DSÞ_sat¼ ðWC_i=2LÞm_satðV_GꢀV_tÞ

in which L (50 mm) and W (500 mm) are the device

channel length and width, respectively; C_iis the capaci-

tance of the insulator; and V_this the threshold voltage.

Figure 8. A) The top-gate OFET device geometry used in this study. B) Representative transfer plots for the indicated bNDT oligomers. C)

Representative transfer plots for the indicated bNDT polymers. Here, devices using Ter2 and Penta1 with Cytop as a dielectric, while devi-

ces using P1, P2, P6, and P7 with poly(methyl methacrylate) (PMMA) as a dielectric. OGI=organic insulator, OSC=organic semiconductor.

Isr. J. Chem. 2014, 54, 796 – 816

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Table 4. Summary of the OTFT performance of the indicated semi-

3ꢀ10⁴for PMMA-based devices in which the semicon-

ductor is annealed at about 1508C. Such mobilities for P1

are comparable to those of OFETs based on the best

phthalimide-based polymers reported to date, such as pol-

conductors.

Dielectric T_ann

[8C]

m_h^[a][cm²Vs^ꢀ1) V_on

SS^[b]

I_on/I_off

[V]

[Vdec^ꢀ1

]

y(dialkoxybithiophene-co-phthalimide)

(m_max=

Ter1

Ter2

Cytop

110

not active

0.0022

–

0

–

4.7

–

0.28 cm²Vs^ꢀ1) and poly(dialkoxybithiazole-co-phthali-

mide) (m_max=0.25 cm²Vs^ꢀ1);^[9a,c]non-substituted bNDT-

based polymers, such as poly(bNDT-co-naphthobisthia-

diazole) (m_max=0.5 cm²Vs^ꢀ1) and poly(bNDT-co-diketo-

pyrrolopyrrole (DPP)) (m_max=1.3 cm²Vs^ꢀ1);^[18c,g]and the

best BTD-based polymers, such as poly[4,8-dialkyl-2,6-

bis(3-alkylthiophen-2-yl)benzo[1,2-b:4,5-b’]dithiophene]

(m_max=0.25 cm²Vs^ꢀ1).^[11a,13e,f]These OFET device charac-

teristics for P1 indicate that such alkoxy-substituted

bNDTs are promising building blocks for hole-transport-

ing materials. Devices using P2, which contains branched

side chains on the bNDT1 unit, exhibit the best hole mo-

bility of about 0.13 cm²Vs^ꢀ1with I_on/I_off>10⁴. The higher

mobility of devices based on P1 as a semiconductor can

be attributed to better packing of the polymer in the solid

state due to the linear side-chain substituents on the

bNDT unit. This result is in agreement with their thin-

film absorption spectra, in which P1 exhibits a clear

shoulder absorption peak and morphological analysis (see

below). Interestingly, it was also found that the per-

formance of P1-based FETs dropped significantly if

Cytop was used as a gate dielectric (m_av=0.043 cm²Vs^ꢀ1),

which could be attributed to the poor wetting of Cytop

on several semiconducting surfaces. Furthermore, P1-

based OFETs (using PMMA as a dielectric) with the

semiconductor layer annealed at lower temperatures (T_ann

ꢁ1208C) also exhibited lower average mobilities (m_av=

0.068 cm²Vs^ꢀ1; see the Supporting Information for re-

spective I_DSꢀV_Gcurves). This result is typical for several

semicrystalline polymeric semiconductors, since higher

film annealing temperatures and longer times promote

film structural reorganization favoring charge trans-

port.^[32,33]OFET devices based on polymer P6, although

processed following similar protocols to those of the

other two polymers, shows lower hole mobilities of

0.033 cm²Vs^ꢀ1, but larger I_on/I_off=3ꢀ10⁵. The significantly

lower hole mobility of P6 than those of P1 and P2 could

be attributed to the combined poorer packing of P6 in

the thin film (see below) and the poor tendency of this

polymer to reorganize, as suggested by the optical data.

Finally, the bNDT2-BTZ building block based polymer,

P7, also showed lower hole mobilities in OFET devices

than those of P1, P2, and P6, with m_av=0.011 cm²Vs^ꢀ1

and I_on/I_off=7ꢀ10⁵. The lower hole mobility of P7 com-

pared with the other three polymers could be attributed

to the electronic structure of this polymer. The deep

HOMO may prevent efficient hole injection when using

bare Au electrodes. It is known that functionalizing the

Au contact surface with proper arene thiols can substan-

tially improve the injection and transport characteristics

for low-HOMO systems.

3ꢁ10⁴

(0.0020)

not active

0.0070

(0.0068)

0.0092

(0.0081)

0.081 (0.068) ꢀ5 1.0

0.40 (0.25)

ꢀ15 1.1

0.057 (0.043) ꢀ17 0.8

0.13 (0.12)

Ter3

Penta1 Cytop

Cytop

110

–

ꢀ6 0.4

3ꢁ10⁵

Penta1 Cytop

150

ꢀ3 0.8

5ꢁ10⁵

P1

P2

P6

P7

PMMA

Cytop

PMMA

120

150

8ꢁ10⁴

3ꢁ10⁴

4ꢁ10³

4ꢁ10⁴

3ꢁ10⁵

7ꢁ10⁵

ꢀ13 1.0

0.033 (0.026) ꢀ8 0.8

0.013 (0.011) ꢀ6 0.8

[a] The average mobility for a statistically significant number of devi-

ces is reported in parentheses. [b] SS=sub-threshold swing.

Mobilities (m_sat) were calculated in the saturation regime

by rearranging Equation (1) to obtain Equation (2):

2

ð2Þ

m_sat¼ ð2I_DSLÞ=½WC_iðV_GꢀV_thÞ ꢂ

The threshold voltage (V_th) can be estimated as the x-

axis intercept of the linear section of the plot of V_G

1/2

versus (I_DS

)

(at V_DS=ꢀ100 V).

For the triad semiconductors, Ter1ꢀTer3, only devices

based on Ter2 were active and exhibited p-channel trans-

port with an average hole mobility of 2.0ꢀ10^ꢀ3cm²Vs^ꢀ1,

an I_on/I_offratio of about 10⁴, a turn-on voltage (V_on) of

about 0 V, and a sub-threshold swing (SS) of ꢁ4 Vdec^ꢀ1

(Figure 8B and Table 4). Unlike Ter1, for which the devi-

ces are inactive, Penta1 TFTs exhibit an average hole mo-

bility of 7.0ꢀ10^ꢀ3cm²Vs^ꢀ1and I_on/I_offratios of about 10⁵.

The superior performance of Penta1 compared with the

triad oligomers could be attributed to the extended conju-

gation, which favored molecular stacking for side/b-sub-

stituted cores; thus promoting charge transport.^[28]This

observation is in agreement with the improved OFET

performance of the devices using the respective polymers

(e.g., P1). The OFET performance of Ter2 and Penta1

are comparable to those of several other benzothiadia-

zole-bithiophene-,^[29]benzothiadiazole-dithienopyrrole-,^[30]

and arylacetylene-based^[31]oligomers in p-channel OFET

devices. It was also found that film thermal annealing at

higher temperatures (1508C) for Penta1-based FET devi-

ces could result in slightly increased hole mobility ap-

proaching 0.01 cm²Vs^ꢀ1, which is common for several or-

ganic semiconductors, since it could promote film struc-

tural reorganization.^[32]

On the other hand, OFET devices based on P1, P2, P6,

and P7 exhibit respectable p-channel characteristics. As

illustrated in Figure 8C and Table 4, P1 exhibits maxi-

mum hole mobilities of 0.40 cm²Vs^ꢀ1and I_on/I_offratios=

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Figure 9. XRD scattering patterns (left) and AFM topography images (right) for films of P1, P2 P6, and P7 fabricated on Polyera B2000/Si

substrates.

To rationalize the performance difference for the best

performing devices, atomic force microscopy (AFM) and

wide-angle X-ray diffraction (XRD) experiments were

carried out on the corresponding semiconductor films.

AFM images of P1 and P2 films indicate that the former

polymer surface is far rougher than that of the latter,

with average root-mean-square (rms) roughnesses of

about 5 and 1 nm, respectively (Figure 9). This result sug-

gests that polymer P1 tends to aggregate far more than

P2 either during film deposition or after thermal anneal-

ing; data are in agreement with the polymer structure

(linear versus branched, respectively), as well as optical

and microstructural (see below) characteristics. The V-2V

XRD scans for films of P1, P2, P6, and P7 with similar

film thickness indicate a single family of Bragg reflections

for polymers P1, P2, and P7 and no Bragg reflections for

P6. This result indicates that the P6 film is amorphous,

which is in agreement with its featureless AFM images

(average rms roughnessꢁ0.5 nm) and limited changes in

the absorption spectra upon going from solution to a thin

film due to the rigid-rod conformation in both states,^[18f]

and much lower hole mobility in OFETs compared with

P1 and P2. The XRD scans corroborate that P1 films are

more textured than those of P2, as demonstrated by the

larger intensity and sharper feature of the P1 scan as well

as the presence of a second reflection that is undetectable

for the other polymer film. For the first reflection, the la-

mellar d spacings are estimated to be 27.60, 20.06, and

24.06 ꢁ for the P1, P2, and P7 films, respectively. This

result demonstrates an edge-on arrangement of the poly-

mer chains for the three systems on the substrate. The

larger d-spacing value for P1 versus P2 could be due to

a greater upright arrangement and/or negligible side-

chain interdigitation. Since branched chains typically pre-

vent efficient interdigitation, the first mechanism is likely

to operate. Furthermore, these results suggest that the

use of linear side chains in the bNDT polymers increases

film crystallinity. The morphological and microstructural

pictures are in agreement with the greater charge-trans-

port capabilities (ꢁ2ꢀ larger FET mobilities) of P1

versus P2. The AFM images from polymer P7 show a tex-

tured morphology (average rms roughnessꢁ1 nm), and

the respective thin-film XRD scans indicate similar crys-

tallinity to that of the film from P2 with slightly lower in-

tensity.

2.4 Photovoltaic Measurements

As discussed above, the relatively deep HOMO

(ꢀ5.2 eV) and small band gap (1.8 eV) of P7 suggest that

this polymer may be a suitable candidate for use as the

donor components in solar cells in combination with ac-

ceptors such as phenyl-C₆₁-butyric acid methyl ester

(PC₆₀BM).^[34]Accordingly, bulk heterojunction (BHJ)

OPV devices were fabricated using the polymer:PC₆₀BM

blend (1:2 w/w) as the active layer in a device with a ge-

ometry of indium tin oxide (ITO)/poly(3,4-ethylenedioxy-

thiophene) (PEDOT)/P7:PC₆₀BM/LiF/Al. The solution of

P7:PC₆₀BM (purchased from Nano-C) was prepared in

1,2-dichlorobenzene at

a

concentration of 12 :24

(mgmL^ꢀ1) and coated onto preheated PEDOT-covered

ITO substrates a with solution temperature of about

1308C. Various spin-coating rates were used to achieve

active-layer thicknesses between 100 and 200 nm with an

active area of the device of about 0.1 cm². The solar cell

performances of these devices are summarized in Table 5

and representative IꢀV and incident photon-to-current ef-

ficiency (IPCE) curves are illustrated in Figure 10. These

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Figure 10. A) JꢀV curves for OPV cells with P7:PC60BM as the active layer. B) IPCE curve for OPV cells with P7:PC60BM as the active layer.

mobilities between 0.01 and 0.1 cm²Vs^ꢀ1. These metrics

Table 5. Summary of the OPV performance of P7.

are respectable for devices fabricated and annealed in

ambient conditions and at moderate temperatures. More-

over, preliminary results on the photovoltaic response of

polymer P7 were presented, which exhibited PCEs of

about 2.2% when blended with PC₆₀BM. These results in-

dicated that alkoxy substitution of the bNDT may have

enabled semiconducting polymers with promising optical

and charge-transport characteristics. Further optimiza-

tions, such as improving the molecular weight, using vari-

ous acceptor units, formulation optimizations, dielectric

optimization, as well as using a greater variety of alkoxy

chains are under investigation.

Materials

Spin rate [rpm]

(Thickness [nm])

V_ocJ_sc

FF PCE

[V] [mAcm^ꢀ2] [%] [%]

P7/PC₆₀BM

Poly(BDT-DBT)/

PC₆₀BM^[a]

600 (ꢁ200)

800 (ꢁ170)

1000 (ꢁ150)

–

0.70 5.78

0.74 6.05

0.70 5.56

0.63 6.18

48.5 1.96

50.4 2.25

54.2 2.11

48.0 1.86

[a] Literature data.^[24]

cells exhibit relative low PCEs when compared with

state-of-the-art polymer OPVs; however, the maximum

PCE value of about 2.2% is comparable to those of the

BDT-DBT linear analogue (ꢁ1.9%). Compared with the

reported poly(BDT-DBT) (Figure 4)^[24]OPV devices in

the literature, slightly higher open-circuit voltages (V_oc),

better fill factors (FFs), and lower short-circuit currents

(J_sc) were achieved for devices based on P7. We are cur-

rently optimizing these devices and testing several copoly-

mers based on bNDT1 and bNDT2 monomers.

4 Experimental Section

All reagents were purchased from commercial sources

and used without further purification unless otherwise

noted. Anhydrous THF was distilled from Na/benzophe-

none. Conventional Schlenk techniques were used on re-

actions that were carried out under N₂unless otherwise

noted. UV/Vis spectra were recorded on a Cary 50 UV/

Vis spectrophotometer. The concentration of the solution

sample was about 1ꢀ10^ꢀ5M and the thin-film samples

that were prepared by spin-coating of the respective poly-

mer solution onto glass followed by a thermal baking.

NMR spectra were recorded on a Varian Unity Plus 500

spectrometer (¹H, 500 MHz). Elemental analysis was per-

formed at Midwest Microlab, LLC. The molecular weight

of the polymers was determined by a Waters GPC system

(Waters Pump 510) in THF at room temperature. The

GPC system used polystyrenes (PSS) as standards. CV

measurements were carried out under nitrogen using

a BAS-CV-50W voltammetric analyzer. For redox meas-

urements of polymer samples, the polymer films were

prepared by drop-casting a 2 mg/mL solution of polymer

in chloroform onto a platinum disk working electrode fol-

lowed by slow drying. A platinum wire served as the aux-

iliary electrode and an Ag wire anodized with AgCl

served as a pseudo-reference electrode. The experiments

were performed on deoxygenated 0.1 M solutions of

3 Conclusions

Two new bNDT-type building blocks were developed and

their stability under photo-illumination was investigated

with respect to BTD analogues. Furthermore, the synthe-

sis of the bNDT building block was also optimized; this

will simplify routes to new NDTs with various alkoxy side

chains. Next, a series of bNDT oligomer and copolymers

were successfully synthesized use Suzuki and or Stille

coupling condensation reactions. Various electron-accept-

ing units were employed, including phthalimide and ben-

zothiadiazole, as well as the electron-neutral dithiophene.

OFET devices based on the bNDT oligomers exhibited

negligible or poor field-effect mobilities, which was maxi-

mum for pentamer Penta1 at about 0.01 cm²Vs^ꢀ1. The

bNDT-phthalimide polymer P1 exhibited hole mobilities

up to 0.40 cm²Vs^ꢀ1, whereas those based on the other so-

lution-processable polymers (P2, P6, and P7) exhibited

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tetra-n-butylammonium hexafluorophosphate in anhy-

The photovoltaic characteristics of the devices were

tested in air. The currentꢀvoltage (IꢀV) curves were ob-

tained by means of a Keithley 2400 source-measure unit.

The photocurrent was measured under simulated AM

1.5G irradiation (100 mWcm^ꢀ2) using a xenon-lamp-

based solar simulator (Newport 91160A 300W Class-A

Solar Simulator, 2 inch by 2 inch uniform beam). The

light intensity was set using a National Renewable

Energy Laboratory (NREL)-calibrated silicon photodiode

with a color filter. External quantum efficiency was mea-

sured using Newportꢂs QE setup. Incident light from

a xenon lamp (300 W) passing through a monochromator

(Newport, Cornerstone 260) was focused on the active

area of the cell. The output current was measured using

a current pre-amplifier (Newport, 70710QE) and a lock-

in amplifier (Newport, 70105 Dual channel Merlin). A

calibrated silicon diode (Newport 70356) was used as

a reference.

drous acetonitrile at a scan rate of 50 mVs^ꢀ1. Potentials

were referenced to the ferrocenium/ferrocene (FeCp2^+/0

)

couple by using ferrocene as an external standard. For

redox property measurements of small-molecule samples,

the experiments were performed on deoxygenated 0.1 M

solutions of tetra-n-butylammonium hexafluorophosphate

in anhydrous dichloromethane with a certain concentra-

tion of the respective materials at a scan rate of

50 mVs^ꢀ1. Potentials were referenced to the FeCp2^+/0

couple by using ferrocene as an internal standard. AFM

was carried out using a Nano Surf SPM S100 instrument.

The surface topography and phase images were obtained

by a generic tapping mode scan in the first pass. Thin-film

XRD patterns were analyzed using wide-angle X-ray dif-

fractometry (WAXRD) on a Rigaku ATX-G using stan-

dard V/2V techniques, with monochromated Cu_Karadia-

tion (l=1.5406 ꢁ) in a continuous scan mode.

Top-gate bottom-contact TFTs were prepared as fol-

lows: Step 1: Glass substrates (eagle 2000) were optional-

ly covered with a thin film of Polyera ActivInk^TMB2000,

which was spin-coated from a solution of propylene

glycol monomethyl ether acetate (PGMEA) at 1200 rpm,

followed by UV irradiation for 10 min. Step 2: Gold (30–

50 nm) was thermally evaporated as sourceꢀdrain (S/D)

electrodes. Step 3: S/D electrodes were treated with pen-

tafluorothiophenol/anisole (5/95 v/v) by spin-drying the

respective solution. Step 4: The semiconductor was dis-

solved in respective solutions, at a concentration of about

6 mg/mL, and spin-coated at 1000–2000 rpm then dried at

120–1508C to give a film of about 50 nm. Step 5: The die-

lectric was deposited by spin-coating. Examples of dielec-

tric include PMMA or Cytop. Gold (30 nm) was thermal-

ly evaporated as a gate electrode. All electrical measure-

ments were performed in ambient conditions.

5 Synthesis Section

Synthesis of 1,5-Dimethoxynaphthalene:^[35]Naphthalene-

1,5-diol (16.0 g, 100 mmol) and potassium carbonate (

27.6 g, 200 mmol) were stirred in acetone (300 mL) under

nitrogen. Dimethyl sulfate (32 mL) was added by using

a syringe. The mixture was then heated to reflux under

nitrogen overnight. Water (300 mL) was added after the

mixture was cooled to room temperature. The precipitate

was collected by filtration and washed with water (4ꢀ

50 mL) then methanol (3ꢀ50 mL). After drying under

vacuum, the solid was heated at reflux in ethanol

(300 mL) for 2 h. After cooling to room temperature, the

desired product was then collected by filtration to give

1

a pale-brown solid (17.9 g, 95.2%). H NMR (500 MHz,

Before OPV device fabrication, the patterned ITO-

coated glass substrates were cleaned by sequential ultra-

sonic treatment in detergent, deionized water, acetone,

and isopropanol, and UV/ozone treatment for 15 min. A

PEDOT:PSS layer of about 40 nm thick was spin-coated

from an aqueous solution (HC Stark, Baytron AI 4083)

onto ITO-coated glass substrates, followed by baking at

1408 for 30 min in air. The solution of polymer:C₆₀-

PCBM (purchased from Nano-C) was prepared in 1,2-di-

chlorobenzene at a concentration of 12 :24 mg/mL. The

solution was kept on a hot plate at 1308; the hot solution

was transferred onto preheated PEDOT-covered sub-

strates using a preheated glass pipette and the spin-coat-

ing process was started immediately. Various layer thick-

nesses were tested. To complete the fabrication of the

device, 0.6 nm thick lithium fluoride (LiF) and 100 nm

thick aluminum were successively deposited thermally

under a vacuum of about 10^ꢀ6torr. The active area of the

device was about 0.1 cm². The devices were then encapsu-

lated with a cover glass using EPO-TEK OG112-6 UV

curable epoxy (Epoxy Technology) in the glove box.

CDCl₃): d=7.45 (d, J=8.5 Hz, 2H), 7.33 (t, J=8.5 Hz,

2H), 6.83 (d, J=8.5 Hz, 2H), 4.00 ppm (s, 6H).

Synthesis of 1,5-Dibromo-4,8-dimethoxynaphthalene:^[36]

1,5-Dimethoxynaphthalene (2.31 g, 12.3 mmol) was

stirred in acetonitrile (30 mL) and cooled to 08C under

nitrogen. A slurry of NBS (4.81 g, 27.0 mmol) in acetoni-

trile (40 mL) was added dropwise. Upon addition, the

mixture was warmed to room temperature slowly and

stirred for another 3 h. The formed precipitate was col-

lected by filtration and 1,5-dibromo-4,8-dimethoxynaph-

thalene was obtained as a grey solid (1.70 g, 40%) after

washing with acetonitrile (2ꢀ5 mL) and methanol (4ꢀ

5 mL). ¹H NMR (500 MHz, CDCl₃): d=7.69 (d, J=

8.5 Hz, 2H), 6.73 (d, J=8.5 Hz, 2H), 3.90 ppm (s, 6H).

Synthesis

of

(4,8-Dimethoxynaphthalene-1,5-diyl)-

bis[(2,2-diethoxyethyl)sulfane)]: 1,5-Dibromo-4,8-dime-

thoxynaphthalene (0.346 g, 1.00 mmol) was dissolved in

anhydrous THF (10 mL) and cooled at ꢀ788 under nitro-

gen. n-Butyllithium (1.0 mL, 2.5 M in hexane, 2.5 mmol)

was then added and stirring was continued for 30 min at

ꢀ788. The reaction mixture was then warmed to room

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temperature slowly and cooled to ꢀ788 immediately.

After another hour, the mixture was treated with bis(2,2-

diethoxyethyl) disulfide (0.746 g, 2.50 mmol) and the mix-

ture was kept at ꢀ788C for 30 min before being warmed

to room temperature slowly and stirred overnight. The

solvent was then removed and the residue was dissolved

in dichloromethane (20 mL) and passed through a short

silica plug eluting with dichloromethane/ethyl acetate

(20 :1). After the solvent was removed under vacuum, the

residue was recrystallized from isopropanol (10 mL) to

give 4,8-dimethoxynaphthalene-1,5-diyl)bis[(2,2-diethox-

CHCl₃/hexane (1:4 and then 2 :3) to give compound

bNTD1ODD as a white solid (4.8 g, 78%). ¹H NMR

(500 MHz, CDCl₃): d=7.56 (d, J=5.0 Hz, 2H), 7.42 (d,

J=5.0 Hz, 2H), 7.41 (s, 2H), 4.32 (t, J=6.5 Hz, 4H), 2.13

(quintet, J=7.5 Hz, 4H), 1.68 (quintet, J=7.5 Hz, 4H),

1.39 (m, 32H), 0.86 ppm (t, J=6.0 Hz, 6H).

Synthesis of [4,9-Bis(dodecyloxy)naphtho[1,2-b:5,6-

b’]dithiophene-2,7-diyl]bis(trimethylstannane)

(bNDT1ODD-Sn2): Compound bNDT1ODD (608 mg,

1.00 mmol) was dissolved in anhydrous THF (30 mL) and

cooled at ꢀ788 under nitrogen. n-Butyllithium (1.0 mL,

2.5 M, 2.5 mmol) was then added and stirred for 30 min.

The mixture was then warmed to room temperature and

stirred at this temperature for another 30 min. The mix-

ture was cooled to ꢀ788 and stirring was continued for

another hour. Trimethyltin chloride (0.50 g, 2.5 mmol) in

anhydrous THF (5.0 mL) was added in one portion and

the mixture was warmed to room temperature slowly and

stirred overnight. The solvent was removed under

vacuum and the residual was dissolved in dichlorome-

thane (100 mL) and washed with water (100 mL) and

brine (100 mL). The solution was dried over Na₂SO₄and

concentrated under vacuum. The residue was recrystal-

lized from isopropanol (30 mL) to give compound

1

yethyl)sulfane] as a pale-yellow solid (0.30 g, 62%). H

NMR (500 MHz, CD₂Cl₂): d=7.28 (d, J=8.5 Hz, 2H),

6.86 (d, J=8.5 Hz, 2H), 4.73 (t, J=5.0 Hz, 2H), 3.94 (s,

6H), 3.71 (m, 4H), 3.60 (m, 4H), 3.11 (d, J=5.5 Hz, 4H),

1.22 ppm (t, J=7.0 Hz, 12H).

Synthesis of (4,9-Dimethoxynaphtho[1,2-b:5,6-b’]di-

thiophene) (bNDT1OMe): PPA (0.29 g) was dissolved in

chlorobenzene (10.0 mL) and heated at reflux for 3 h

under nitrogen. A solution of (4,8-dimethoxynaphtha-

lene-1,5-diyl)bis[(2,2-diethoxyethyl)sulfane]

(0.225 g,

0.464 mmol) in chlorobenzene (3.0 mL) was added drop-

wise to the reaction mixture. The mixture was stirred at

reflux overnight. After the mixture was cooled to room

temperature, dichloromethane (100 mL) was added, and

the mixture was washed with NaHCO₃(saturated, 2ꢀ

50 mL) and brine (50 mL). The solution was dried over

Na₂SO₄and concentrated under reduced pressure. The

residue was heated at reflux in isopropanol (30 mL) for

2 h. After cooling to room temperature, bNDT1OMe was

obtained by filtration as a pale-yellow solid (120 mg,

86%). ¹H NMR (500 MHz, CDCl₃): d=7.59 (d, J=

5.5 Hz, 2H), 7.45 (d, J=5.5 Hz, 2H), 7.44 (s, 2H),

4.19 ppm (s, 6H).

Synthesis of 4,9-Bis(dodecyloxy)naphtho[1,2-b:5,6-

b’]dithiophene (bNTD1ODD): NTD1Me (150 mg,

0.50 mmol) and p-toluenesulfonic acid monohydrate

(15.2 mg, 0.080 mmol; 16 mol% to NTD1Me) were

heated in dodecan-1-ol (3.7 g, 20 mmol) at 2008C under

nitrogen overnight. Upon cooling to room temperature,

the solvent was removed under reduced pressure and the

residue was purified by column chromatography on silica

gel eluted with CHCl₃/hexane (1:4 and then 2 :3) to give

compound bNTD1ODD as a white solid (110 mg, 36%).

¹H NMR (500 MHz, CDCl₃): d=7.56 (d, J=5.0 Hz, 2H),

7.42 (d, J=5.0 Hz, 2H), 7.41 (s, 2H), 4.32 (t, J=6.5 Hz,

4H), 2.13 (quintet, J=7.5 Hz, 4H), 1.68 (quintet, J=

7.5 Hz, 4H), 1.39 (m, 32H), 0.86 ppm (t, J=6.0 Hz, 6H).

Synthesis of 4,9-Bis(dodecyloxy)naphtho[1,2-b:5,6-

b’]dithiophene (bNTD1ODD): bNTD1OMe (3.0 g,

10 mmol) and p-toluenesulfonic acid monohydrate (1.9 g,

10 mmol; 100 mol% to bNTD1OMe) were heated in do-

decan-1-ol (70 mL) at 2008C under nitrogen overnight.

Upon cooling to room temperature, the solvent was re-

moved under reduced pressured and the residue was puri-

fied by column chromatography on silica gel eluted with

1

bNDT1ODD-Sn2 as a pale-yellow solid (0.80 g, 85%). H

NMR (500 MHz, CDCl₃): d=7.49 (s, 2H), 7.40 (s, 2H),

4.32 (t, J=6.5 Hz, 4H), 2.12 (m, 4H), 1.72 (m, 4H), 1.39

(m, 32H), 0.86 (t, J=7.0 Hz, 6H), 0.43 ppm (t, J=30 Hz,

18H).

Synthesis of 4,9-Bis(2-butyl-1-octyl)naphtho[1,2-b:5,6-

b’]dithiophene (bNTD1OBO): bNTD1OMe (1.0 g,

3.3 mmol) and p-toluenesulfonic acid monohydrate

(0.63 g, 3.3 mmol) were heated in 2-butyl-1-octonol

(25.0 mL) at 2008C under nitrogen overnight. The solvent

was removed under vacuum, and the residue was purified

by column chromatography on silica gel eluted with

hexane then CHCl₃/hexane (1:9) to give compound

1

bNTD1OBO as a pale-yellow oil (1.80 g, 90%). H NMR

(500 MHz, CD₂Cl₂): d=7.65 (d, J=5.0 Hz, 2H), 7.52 (s,

2H), 7.49 (d, J=5.5 Hz, 2H), 4.27 (d, J=5.5 Hz, 4H), 2.20

(m, 2H), 1.82 (m, 4H), 1.64 (m, 4H), 1.39 (m, 24H),

0.91 ppm (m, 12H).

Synthesis of [4,9-Bis(2-butyl-1-octyl)naphtho[1,2-b:5,6-

b’]dithiophene-2,7-diyl]bis(trimethylstannane) (bNTD1O-

BO-Sn2): Compound bNTD1OBO (608 mg, 1.00 mmol)

was dissolved in anhydrous THF (30 mL) and cooled at

ꢀ788 under nitrogen. n-Butyllithium (1.0 mL, 2.5 M,

2.5 mmol) was then added and stirring was continued for

30 min. The mixture was then warmed to room tempera-

ture and stirred for another 30 min. The mixture was

cooled to ꢀ788 and stirred for another hour. Trimethyltin

chloride (0.50 g, 2.5 mmol) in anhydrous THF (5.0 mL)

was added in one portion and the mixture was warmed to

room temperature slowly and stirred overnight. The sol-

vent was removed under vacuum and the residue was dis-

solved in dichloromethane (100 mL) and washed with

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water (100 mL) and brine (100 mL). The solution was

dried over Na₂SO₄and concentrated in vacuo. The resi-

due was recrystallized from isopropanol to give

NaHCO₃before the solvent was removed under vacuum.

Methanol (100 mL) was added before the product

bNDT2OMe (2.0 g, 66.0%) was collected by filtration as

a white solid, washed with methanol, and dried in vacuo.

¹H NMR (500 MHz, CDCl₃): d=7.97 (d, J=5.5 Hz, 2H),

7.62 (d, J=5.5 Hz, 2H), 7.51 (s, 2H), 4.18 ppm (s, 6H) .

Synthesis of 5,10-Bis-dodecyloxy-1,6-dithiadicyclo-

1

bNTD1OBO-Sn2 as a pale-yellow solid (0.75 g, 80%). H

NMR (500 MHz, CDCl₃): d=7.50 (s, 2H), 7.42 (s, 2H),

4.18 (t, J=5.5 Hz, 4H), 2.18 (m, 2H), 1.80 (m, 4H), 1.39

(m, 28H), 0.8–0.9 (m, 12H), 0.43 ppm (t, J=30 Hz, 18H).

Synthesis of 2,6-Dimethoxynaphthalene: Naphthalene-

2,6-diol (16.0 g, 0.1 mol) and NaH (6.0 g, 0.25 mol) was

combined in a 500 mL flask under argon. The mixture

was cooled to ꢀ788C before anhydrous DMF (200 mL)

was injected. Lots of gas was observed. Stirring was con-

tinued at room temperature for 2 h. Dimethyl sulfate

(31.5 g, 0.25 mol) was added dropwise after the mixture

was cooled to ꢀ788C again. The reaction was continued

overnight at room temperature before water (200 mL)

was added. 2,6-Dimethoxynaphthalene (16.0 g, 85.1%)

was collected as a white powder by filtration, washed

penta[a,f]naphthalene

(bNDT2ODD):

bNDT2OMe

(230 mg, 0.77 mmol), p-toluenesulfonic acid monohydrate

(145 mg, 0.77 mmol), and 1-dodecanol (7 mL) were added

to a 50 mL three-necked flask equipped with a condenser.

The system was heated at 2008C overnight under argon

before being cooled to room temperature. Hexane

(50 mL) was added and the organic layer was washed

with saturated NaHCO₃before the solvent was removed

under vacuum. Excess 1-dodecanol was distilled out

under vacuum. Column chromatography (silica gel) with

hexane/dichloromethane (v/v, 4/1) as the eluent yielded

1

with water and methanol, and dried under vacuum. H

bNDT2ODD as a white solid (320 mg, 68.2%). H NMR

NMR (500 MHz, CDCl₃): d=7.67 (d, J=8.5 Hz, 2H),

7.17 (dd, J=8.5, 2.5 Hz, 2H), 7.13 (d, J=2.5 Hz, 2H), 7.13

(d, J=2.5 Hz, 2H), 3.9 ppm (s, 6H).

(500 MHz, CDCl₃): d=7.95 (d, J=5.5 Hz, 2H), 7.61 (d,

J=5.5 Hz, 2H), 7.50 (s, 2H), 4.35 (t, J=6.0 Hz, 4H), 1.99

(m, 4H), 1.61 (m, 4H), 1.29 (m, 32H), 0.90 ppm (t, J=

6.5 Hz, 6H).

Synthesis of 2,6-Bis(2,2-diethoxyethylsulfanyl)-3,7-di-

methoxynaphthalene: 2,6-Dimethoxynaphthalene (3.76 g,

20.0 mmol) was added to a 200 mL Schlenk flask. The

system was placed under vacuum and backfilled with

argon three times before anhydrous THF (100 mL) was

added. After the mixture was cooled to 08C for 30 min,

n-butyllithium (34 mL, 2.5 M, 85.0 mmol) was added

dropwise. The resulting mixture was stirred at room tem-

perature for 4 h before being cooled to ꢀ788C. 1,2-

bis(2,2-Diethoxyethyl) disulfide (26.6 g, 103 mmol) was

injected in one portion. The dry-ice bath was removed

5 min later and the mixture was stirred overnight. Water

(100 mL) was added to quench the reaction and the mix-

ture was stirred at room temperature for 10 min. Hexane

(3ꢀ150 mL) was used to extract the product and the com-

bined organic layers were dried with anhydrous Na₂SO₄.

Methanol (150 mL) was added and the product 2,6-bis-

(2,2-diethoxyethylsulfanyl)-3,7-dimethoxynaphthale-

ne,(5.0 g, 52.0%) was collected by filtration as yellow

solid and washed with methanol and dried under vacuum.

¹H NMR (500 MHz, CDCl₃): d=7.62 (s, 2H), 7.00 (s,

2H), (t, J=2.5 Hz, 2H), 3.99 (s, 6H), 3.73 (m, 4H), 3.60

(m, 4H), 3.23 (d, J=2.5 Hz, 4H), 1.23 ppm (t, J=9.0 Hz,

12H),

Synthesis of 5,10-Bis-dodecyloxy-2,7-bis-trimethylstan-

nanyl-1,6-dithiadicyclopenta[a,f]naphthalene

(bNDT2ODD-Sn2): Compound bNDT2ODD (0.366 g,

0.6 mmol) was added to a 50 mL flask. The system was

placed under vacuum and backfilled with argon three

times before anhydrous THF (17 mL) was injected. n-Bu-

tyllithium (2.5 M in hexane; 0.6 mL, 1.5 mmol) was added

after the mixture was cooled to ꢀ788C. White precipitate

was observed after the mixture was stirred at ꢀ788C for

30 min. Stirring was continued at room temperature for

one more hour before being cooled to ꢀ788C again. Tri-

methyltin chloride (0.5 g, 2.5 mmol) was added in por-

tions and stirring was continued overnight at room tem-

perature. Hexane (100 mL) was added and the organic

layer was washed with water (150 mL). The aqueous

layer was extracted with hexane (2ꢀ50 mL). The com-

bined organic layer was dried over anhydrous Na₂SO₄.

Removal of solvent under vacuum yielded a white solid.

The colorless crystalline product bNDT2ODD-Sn2

(0.48 g, 85.7%) was obtained after recrystallization from

1

hexane/isopropanol. H NMR (CDCl₃, 500 MHz): d=7.80

(s, 2H), 7.51 (s, 2H), 4.37 (t, J=6.5 Hz, 4H), 2.00 (m, 4H),

1.63 (m, 4H), 1.46 (m, 4H), 1.30 (m, 28H), 0.90 (t, J=

7.0 Hz, 6H), 0.51 ppm (m, 18H).

Synthesis of 5,10-Dimethoxy-1,6-dithiadicyclopenta-

[a,f]naphthalene (bNDT2OMe): 2,6-Bis-(2,2-diethoxye-

Synthesis of 5,10-Bis-(2-butyloctyloxy)-1,6-dithiadi-

cyclopenta[a,f]naphthalene (bNDT2OBO): bNDT2OMe

(1.80 g, 6.0 mmol), p-toluenesulfonic acid monohydrate

(1.14g, 6.0 mmol), and 2-butyloctanol (35 mL) were

added to a 250 mL three-necked flask equipped with

a condenser. The system was heated at 2008C overnight

under argon before being cooled to room temperature.

Hexane (200 mL) was added and the organic layer was

washed with saturated NaHCO₃before the solvent was

thylsulfanyl)-3,7-dimethoxynaphthalene

(5.0 g,

10.3 mmol) and PPA (6.8 g) were added to a 250 mL

three-necked flask equipped with a condenser. The

system was flushed with argon for 15 min before anhy-

drous chlorobenzene (50 mL) was added. The mixture

was heated at 1408C for 40 h before being cooled to

room temperature. Dichloromethane (100 mL) was added

and the organic mixture was washed with saturated

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removed under vacuum. Excess 2-butyloctanol was dis-

tilled out under vacuum. Column chromatography (silica

gel) with hexane/dichloromethane (v/v, 100/4) as the

eluent yielded product bNDT2OBO as a colorless liquid

Synthesis of 2-Bromo-4,9-bis(dodecyloxy)naphtho[1,2-

b:5,6-b’]dithiophene (bNDT1ODD-Br): bNDT1ODD

(0.15 g, 0.025 mmol) was dissolved in anhydrous THF

(30 mL) and cooled to 08C under nitrogen. NBS (0.045 g,

0.025 mmol) was then added and stirring was continued

for 10 h at this temperature. The mixture was then

warmed to room temperature and stirring was continued

for another 18 h. The solvent was removed under vacuum

and the residue was purified by column chromatography

on silica gel with dichloromethane/hexane (1/6) as the

eluent to give compound bNDT1ODD-Br as a pale-

1

(2.5 g, 68.5%). H NMR (500 MHz, CDCl₃): d=7.96 (d,

J=5.5 Hz, 2H), 7.60 (d, J=5.5 Hz, 2H), 7.50 (s, 2H), 4.23

(d, J=5.5 Hz, 4H), 1.99 (m, 2H), 1.33 (m, 32H), 0.96 (t,

J=7.0 Hz, 6H), 0.90 ppm (t, J=7.0 Hz, 6H).

Synthesis of 5,10-Bis-(2-butyloctyloxy)-2,7-bis-trime-

thylstannanyl-1,6-dithiadicyclopenta[a,f]naphthalene

(bNDT2OBO-Sn2): bNDT2OBO (1.41 g, 2.3 mmol) was

added to a 200 mL flask. The system was placed under

vacuum and backfilled with argon three times before an-

hydrous THF (60 mL) was injected. n-Butyllithium

(2.5 M in hexane; 2.2 mL, 5.09 mmol) was added after the

mixture was cooled to ꢀ788C. White precipitate was ob-

served after the mixture was stirred at ꢀ788C for 30 min.

Stirring was continued at room temperature for one more

hour before being cooled to ꢀ788C again. Trimethyltin

chloride (1.20 g, 5.75 mmol) was added in portions and

stirring was continued overnight at room temperature.

Hexane (100 mL) was added and the organic layer was

washed with water (150 mL). The aqueous layer was ex-

tracted with hexane (2ꢀ100 mL). The combined organic

layers were dried over anhydrous Na₂SO₄. Removal of

solvent under vacuum yielded a white solid. The colorless

crystalline product bNDT2OBO-Sn2 (1.70 g, 79.0 %) was

obtained after recrystallization from hexane/isopropanol.

¹H NMR (500 MHz, CDCl₃): d=7.80 (s, 2H), 7.69 (s,

2H), 4.25 (d, J=5.5 Hz, 4H), 1.99 (m, 2H), 1.33 (m, 32H),

0.96 (t, J=7.0 Hz, 6H), 0.90 (t, J=7.0 Hz, 6H), 0.51 ppm

(m, 18H).

Synthesis of 2-[4,9-Bis(dodecyloxy)naphtho[1,2-b:5,6-

b’]dithiophen-2-yl]-4,4,5,5-tetramethyl-1,3,2-dioxaboro-

lane (bNDT1ODD-BOR): Compound bNDT1ODD

(0.50 g, 0.82 mmol) and was dissolved in anhydrous THF

(30 mL) and cooled to ꢀ788C under nitrogen. n-Butyl-

lithium (0.32 mL, 2.5 M, 0.82 mmol) was then added and

stirring was continued for 30 min. The mixture was then

warmed to room temperature and stirred for another

30 min. The mixture was cooled to ꢀ788C and stirring

was continued for another hour. 2-Isopropoxy-4,4,5,5-tet-

ramethyl-1,3,2-dioxaborolane (0.50 g, 2.7 mmol) in anhy-

drous THF (5.0 mL) was added in one portion and the

mixture was warmed to room temperature slowly and stir-

ring was continued overnight. The solvent was removed

under vacuum and the residue was dissolved in a mixture

of dichloromethane/hexane (1/1, 10 mL) and passed

through a short silica plug eluted with dichloromethane/

hexane (1/1) to give compound bNDT1ODD-BOR as

a pale-yellow solid (0.19 g, 32%). ¹H NMR (500 MHz,

CDCl₃): d=7.84 (s, 1H), 7.58 (d, J=5.0 Hz, 1H), 7.40 (m,

2H), 7.37 (s, H), 4.34 (t, J=6.5 Hz, 2H), 4.31 (t, J=

6.5 Hz, 2H), 2.13 (m, 4H), 1.72 (m, 4H), 1.39 (m, 44H),

0.86 ppm (m, 6H).

1

yellow solid (0.10 g, 58%). H NMR (500 MHz, CDCl₃):

d=7.66 (br d, 1H), 7.46 (m, 3H), 7.37 (s, H), 4.34 (t, J=

6.5 Hz, 2H), 4.36 (m, J=6.5 Hz, 4H), 2.22 (m, 4H), 1.72

(m, 4H), 1.39 (m, 32H), 0.86 ppm (m, 6H).

Synthesis of 5,5’-Bis[4,9-bis(dodecyloxy)naphtho[1,2-

b:5,6-b’]dithiophen-2-yl]-2,2’-bithiophene (Ter2): A de-

oxygenated mixture of bNDT1ODD-BOR (0.18 g,

0.25 mmol),

5,5’-dibromo-2,2’-bithiophene

(0.032 g,

0.10 mmol), and Pd(PPh₃)₄(0.002 g, 0.02 mmol) in tolu-

ene (5 mL) and a 2 M aqueous solution of K₂CO₃(3 mL)

was heated to 908C for 2 h under nitrogen in a two-

necked round-bottomed flask with a reflux condenser at-

tached. Methanol (30 mL) was added to the mixture and

the resulting solid was filtered and washed with water

(3ꢀ5 mL) and methanol (3ꢀ5 mL). The solid was then

recrystallized from isopropanol/toluene (3/1) to give Ter2

1

as an orange solid (0.089 g, 64%). H NMR (500 MHz,

CD₂Cl₂): d=7.65 (d, J=5.5 Hz, 2H), 7.59 (s, 2H), 7.50 (m,

4H), 7.41 (s, 2H), 7.35 (d, J=4.0 Hz, 2H), 7.26 (d, J=

4.0 Hz, 2H), 4.41(m, 8H), 2.25 (m, 8H), 1.82 (m, 4H), 1.80

(m, 4H), 1.52–1.20 (m, 64H), 0.84 ppm (m, 12H); elemen-

tal analysis calcd (%) for C₈₄H₁₁₄O₄S₆: C 73.10, H 8.33, N

0.00; found: C 72.98, H 8.24, N 0.00.

Synthesis of 4,7-Bis[4,9-bis(dodecyloxy)naphtho[1,2-

b:5,6-b’]dithiophen-2-yl]-2-dodecylisoindoline-1,3-dione

(Ter1): A deoxygenated mixture of bNDT1ODD-BOR

(0.18 g, 0.25 mmol), 4,7-dibromo-2-dodecylisoindoline-1,3-

dione (0.047 g, 0.10 mmol), and Pd(PPh₃)₄(0.002 g,

0.02 mmol) in toluene (8 mL) and a 2 M aqueous solution

of K₂CO₃(5 mL) was heated to 908C for 16 h under ni-

trogen in

a two-necked round-bottomed flask with

a reflux condenser attached. Toluene (50 mL) was added

to the mixture and the resulting mixture was washed with

water (2ꢀ50 mL). The organic phase was dried with an-

hydrous Na₂SO₄. After the solid was removed by filtra-

tion and the solvent was removed by rotary evaporation,

the residue was purified by column chromatography on

silica gel eluted with chloroform/hexane (1/2) to give

Ter1 as a dark-yellow solid (0.064 g, 43%). ¹H NMR

(500 MHz, CD₂Cl₂): d=8.28 (s, 2H), 8.07 (s, 2H), 7.68 (d,

J=5.0 Hz, 2H), 7.55 (s, 2H), 7.53 (m, 4H), 4.43 (m, 8H),

3.75 (t, J=8.5 Hz, 2H), 2.25 (m, 8H), 1.80 (m, 10H), 1.52–

1.20 (m, 82H), 0.90–0.80 ppm (m, 15H); elemental analy-

sis calcd (%) for C₉₆H₁₃₇NO₆S₄: C 75.39, H 9.03, N 0.92;

found: C 75.37, H 8.97, N 1.07.

Isr. J. Chem. 2014, 54, 796 – 816

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Synthesis of 1,3-Bis[4,9-bis(dodecyloxy)naphtho[1,2-

b:5,6-b’]dithiophen-2-yl]-5-dodecyl-4H-thieno[3,4-c]pyr-

role-4,6(5H)-dione (Ter3): A deoxygenated mixture of

bNDT1ODD-BOR (0.18 g, 0.25 mmol), 1,3-dibromo-5-

dodecyl-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione (0.048 g,

0.10 mmol), and Pd(PPh₃)₄(0.002 g, 0.02 mmol) in tolu-

ene (8 mL) and a 2 M aqueous solution of Na₂CO₃

(5 mL) was heated to 908C for 16 h under nitrogen in

a two-necked round-bottomed flask with a reflux con-

denser attached. Toluene (50 mL) was added to the mix-

ture and the resulting mixture was washed with water (2ꢀ

50 mL). The organic phase was dried with anhydrous

Na₂SO₄. After the solid was removed by filtration and the

solvent was removed by rotary evaporation, the residue

was purified by column chromatography on silica gel

eluted with chloroform/hexane (1/2) to give Ter3 as a red

Synthesis of P1: Compound bNDT1ODD-Sn2

(0.1402 g, 0.1500 mmol), 4,7-dibromo-2-tetradecylisoindo-

line-1,3-dione (0.0752 g, 0.1500 mmol), tri-o-tolylphos-

phine (9.1 mg, 0.030 mmol), and Pd₂dba₃(3.7 mg,

0.0038 mmol) were charged in a Schlenk tube and the

system was then evacuated and refilled with N₂four

times. Chlorobenzene (20.0 mL) was added before the

mixture was heated to 1308C and stirred at this tempera-

ture for 3 days under nitrogen. After the mixture was

cooled to room temperature, methanol (20 mL) was

added. The formed solid was filtered and washed with

methanol. The solid was washed sequentially with hot

methanol (6 h) and hot ethyl acetate (12 h) using a Soxh-

let apparatus under nitrogen. The residue was then ex-

tracted with dichloromethane in a Soxhlet apparatus. The

solvent was then removed and the residue was dissolved

in chloroform (3.0 mL) before it was precipitated into

methanol (50 mL). The resulting solid was filtered and

washed with methanol and dried under vacuum to give

P1 as a red solid (130 mg, 91%). GPC (THF, RT): M_n=

1

solid (0.077 g, 51%). H NMR (500 MHz, CD₂Cl₂): d=

8.43 (s, 2H), 7.63 (d, J=5.0 Hz, 2H), 7.43 (d, J=5.0 Hz,

2H), 7.41(s, 2H), 7.34 (s, 2H), 4.38 (t, J=6.5 Hz, 4H), 4.26

(t, J=6.5 Hz, 4H), 3.73 (t, J=4.5 Hz, 2H), 2.27 (m, 4H),

2.10 (m, 4H), 1.85–1.20 (m, 92H), 0.90–0.80 ppm (m,

15H); elemental analysis calcd (%) for C₉₄H₁₃₅NO₆S₅: C

73.53, H 8.86, N 0.91; found: C 73.29, H 8.86, N 1.02.

Synthesis of Br-PI-NDT1-PI-Br: A deoxygenated mix-

ture of bNDT1ODD-Sn2 (0.25 g, 0.26 mmol), 4,7-dibro-

mooctylisoindoline-1,3-dione (0.47 g, 1.1mmol), and

Pd(PPh₃)₄(0.017 g, 0.015 mmol) in DMF (10 mL) was

heated to 1408C for 16 h under nitrogen in a sealed tube.

MeOH (15 mL) was added to the mixture and the result-

ing precipitate was filtered and purified by column chro-

matography on silica gel eluted with chloroform/hexane

(1/4) to give Br-PI-NDT1-PI-Br as a dark-yellow solid

1

37.0 kD, M_w=55.6 kD, M_w/M_n=1.5; H NMR (400 MHz,

CDCl₃): d=6.5–8.4 (m, 6H), 3.2–4.4 (m, 6H), 2.1–0.8 ppm

(m, 73H); elemental analysis calcd (%) for P1

(C₆₀H₈₅NO₄S₂)_n: C 75.98, H 9.03, N 1.48; found: C 75.92,

H 9.12, N 1.38.

Synthesis of P2: Compound bNDT1OBO-Sn2

(0.1402 g, 0.1500 mmol), 4,7-dibromo-2-dodecylisoindo-

line-1,3-dione (0.0710 g, 0.1500 mmol), tri-o-tolylphos-

phine (11.0 mg 0.036 mmol), and Pd₂dba₃(4.1 mg,

0.0045 mmol) were charged in a 50 mL Schlenk tube and

the system was then evacuated and refilled with N₂four

times. THF (10.0 mL) was added before the mixture was

heated to 808C and kept at this temperature for 18 h

under nitrogen in a sealed tube. After the mixture was

cooled to room temperature, methanol (20 mL) was

added. The formed solid was filtered and washed with

methanol. The solid was washed sequentially with hot

methanol (6 h) and hot ethyl acetate (12 h). The residue

was then extracted with chloroform in a Soxhlet appara-

tus. The solvent was then removed and the residue was

dissolved in chloroform (5.0 mL) before being precipitat-

ed in methanol (50 mL). The resulting solid was filtered,

washed with MeOH, and dried under vacuum to give P2

as a red solid (120 mg, 87%). GPC (THF, RT): M_n=

1

(0.164 g, 49%). H NMR (500 MHz, CDCl₃): d=8.21 (s,

2H), 7.74 (m, 4H), 7.39 (s, 2H), 7.55, 4.30 (t, J=6.5 Hz,

4H), 3.65 (t, J=7.5 Hz, 4H), 2.11 (m, 4H), 1.68 (m, 10H),

1.52–1.10 (m, 50H), 0.90–0.80 ppm (m, 12H).

Synthesis of Penta1:

A deoxygenated mixture of

bNDT1ODD-BOR (0.17 g, 0.23 mmol), Br-PI-NDT1-PI-

Br (0.080 g, 0.063 mmol), and Pd(PPh₃)₄(0.0012 g,

0.01 mmol) in toluene (8 mL) and a 2 M aqueous solution

of Na₂CO₃(5 mL) was heated to 908C for 16 h under ni-

trogen in

a two-necked round-bottomed flask with

a reflux condenser attached. Toluene (50 mL) was added

to the mixture and the resulting mixture was washed with

water (2ꢀ50 mL). The organic phase was dried with an-

hydrous Na₂SO₄. After the solid was removed by filtra-

tion and the solvent was removed by rotary evaporation,

the residue was purified by column chromatography on

silica gel eluted with chloroform/hexane (1/2 and then 1/

1

39.6 kD, M_w=102.9 kD, M_w/M_n=2.6; H NMR (400 MHz,

CDCl₃): d=6.4–8.5 (m, 6H), 3.2–4.4 (m, 6H), 2.1–0.8 ppm

(m, 69H); elemental analysis calcd (%) for P2

(C₅₈H₈₁NO₄S₂)_n: C 75.69, H 8.87, N 1.52; found: C 76.17,

H 8.52, N 1.55.

Synthesis of P3: Compound bNDT1ODD-Sn2

(0.1402 g, 0.1500 mmol), 5,5’-dibromo-2,2’-bithiophene

(0.0456 g, 0.1500 mmol), tri-o-tolylphosphine (11.0 mg

0.036 mmol), and Pd₂dba₃(4.1 mg, 0.0045 mmol) were

charged in a 50 mL Schlenk tube and the system was then

evacuated and refilled with N₂four times. Chlorobenzene

(20.0 mL) was added before the mixture was heated to

1

1) to give Penta1 as a red solid (0.066 g, 45%). H NMR

(500 MHz, CD₂Cl₂): d=8.19 (s, 2H), 8.12 (s, 2H), 7.93 (m,

4H), 7.62 (m, 4H), 7.44–7.40 (m, 4H), 7.32 (s, 2H) 4.4–4.0

(m, 12H), 3.67 (br s, 4H), 2.2–1.2 (m, 144H), 0.90–

0.80 ppm (m, 24H); elemental analysis calcd (%) for

C

₁₄₆H₂₀₂N₂O₁₀S₆: C 75.02, H 8.71, N 1.20; found: C 75.00,

H 8.63, N 1.21.

Isr. J. Chem. 2014, 54, 796 – 816

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www.ijc.wiley-vch.de

813

Full Paper

1308C and kept at this temperature under nitrogen. An

orange precipitate forming during polymerization and no

further attempt to purify P3 was carried out.

Synthesis of P7: Compound bNDT2OBO-Sn2

(0.0934 g, 0.1000 mmol), 4,7-bis(5-bromo-4-dodecylthio-

phen-2-yl)benzo[c][1,2,5]thiadiazole (0.0794 g, 0.1000

mmol), tri-o-tolylphosphine (11.0 mg 0.036 mmol), and

Pd₂dba₃(2.7 mg, 0.003 mmol) were charged in a 50 mL

Schlenk tube and the system was then evacuated and re-

filled with N₂four times. Chlorobenzene (10.0 mL) was

added before the mixture was heated to 1308C and kept

at this temperature for 18 h under nitrogen in a sealed

tube. After the mixture was cooled to room temperature,

methanol (20 mL) was added. The formed solid was fil-

tered and washed with methanol. The solid was washed

sequentially with hot methanol (6 h) and hot ethyl acetate

(12 h). The residue was then extracted with chloroform in

a Soxhlet apparatus. The solvent was then removed and

the residue was dissolved in chloroform (10.0 mL) before

precipitating in methanol (50 mL). The resulting solid

was filtered and washed with MeOH and dried under

vacuum to give P7 as a red solid (82 mg, 81%). GPC

(THF, RT): M_n=81.2 kD, M_w=117.7, M_w/M_n=1.5; ele-

mental analysis calcd (%) for P7 (C₇₆H₁₀₈N₂O₂S₅)_n: C

73.49, H 8.76, N 2.26; found: C 72.99, H 8.28, N 2.23.

Synthesis of P4: Compound bNDT1OBO-Sn2

(0.1402 g, 0.1500 mmol), 5,5’-dibromo-2,2’-bithiophene

(0.0456 g, 0.1500 mmol), tri-o-tolylphosphine (11.0 mg

0.036 mmol), and Pd₂dba₃(4.1 mg, 0.0045 mmol) were

charged in a 50 mL Schlenk tube and the system was then

evacuated and refilled with N₂four times. Chlorobenzene

(20.0 mL) was added before the mixture was heated to

1308C and kept at this temperature for 24 h under nitro-

gen. After the mixture was cooled to room temperature,

methanol (20 mL) was added. The formed solid was fil-

tered and washed with methanol. The solid was further

washed with hot methanol (6 h), hot ethyl acetate (12 h),

and chloroform (6 h) using a Soxhlet apparatus under ni-

trogen. The residue was then collected and dried to give

P4 as a red solid (96 mg, 83%). This material is insoluble

in common organic solvent and no further purification

was performed. Elemental analysis calcd (%) for Poly-

NDT1BO-TT (C₄₆H₅₈O₂S₄)_n: C 71.64, H 7.58, N 0.00;

found: C 71.56, H 7.63, N 0.00.

Synthesis of P5: Compound NDT1DD-Sn2 (0.0934 g,

0.1000 mmol),

1,3-dibromo-5-dodecyl-4H-thieno[3,4-

Acknowledgements

c]pyrrole-4,6(5H)-dione (0.0479 g, 0.1000 mmol), tri-o-tol-

ylphosphine (11.0 mg 0.036 mmol), and Pd₂dba₃(2.7 mg,

0.003 mmol) were charged in a 50 mL Schlenk tube and

the system was then evacuated and refilled with N₂four

times. Chlorobenzene (10.0 mL) was added before the

mixture was heated to 1308C and kept at this tempera-

ture under nitrogen. A red precipitate formed during

polymerization and no further attempt to purify P5 was

carried out.

We would like to thank Dr. Henry He Yan, Dr. Yu Xia,

and Dr. Damien Boudinet from Polyera Corporation and

Dr. Yanrong Shi and Dr. Xugang Guo from Northwestern

University for helpful discussions.

References

Synthesis of P6: Compound bNDT1OBO-Sn2

[1] a) T. A. Skotheim, J. R. Reynolds, Handbook of Conducting

Polymers, 3rd Ed., CRC Press, Boca Raton, 2007; b) M. Le-

clerc, J. F. Morin, Design and Synthesis of Conjugated Poly-

mers, Wiley-VCH, Weinheim, 2010; c) Z. N. Bao, J. Locklin,

Organic Field-Effect Transistors, CRC Press, New York,

2007.

[2] a) Y. Y. Liang, L. P. Yu, Acc. Chem. Res. 2010, 43, 1227;

b) B. Kippelen, J.-L. Bredas, Energy Environ. Sci. 2009, 2,

251; c) C. L. Wang, H. L. Dong, W. P. Hu, Y. Q. Liu, D. B.

Zhu, Chem. Rev. 2012, 112, 2208; d) H. Minemawari, T.

Yamada, H. Matsui, J. Y. Tsutsumi, S. Haas, R. Chiba, R.

Kumai, T. Hasegawa, Nature 2011, 475, 364; e) H. Sirring-

haus, Adv. Mater. 2014, 26, 1319; f) X. Guo, N. Zhou, S. J.

Lou, J. Smith, D. B. Tice, J. W. Hennek, R. P. Ortiz, J. T. L.

Navarrete, S. Li, J. Strzalka, L. X. Chen, R. P. H. Chang, A.

Facchetti, T. J. Marks, Nat. Photonics 2013, 7, 825; g) A. Fac-

chetti, Mater. Today 2013, 16, 123; h) Y. Yuan, G. G. A.

Ayzner, A. P. Zoombelt, S. C. B. Mannsfeld, J. Chen, J.

Huang, Z. Bao, Nat. Commun. 2014, 5, 3005.

(0.0934 g,

0.1000 mmol),

1,3-dibromo-5-dodecyl-4H-

thieno[3,4-c]pyrrole-4,6(5H)-dione

(0.0479 g, 0.1000

mmol), tri-o-tolylphosphine (11.0 mg 0.036 mmol), and

Pd₂dba₃(2.7 mg, 0.003 mmol) were charged in a 50 mL

Schlenk tube and the system was then evacuated and re-

filled with N₂four times. Chlorobenzene (10.0 mL) was

added before the mixture was heated to 1308C and kept

at this temperature for 18 h under nitrogen in a sealed

tube. After the mixture was cooled to room temperature,

methanol (20 mL) was added. The formed solid was fil-

tered and washed with methanol. The solid was washed

sequentially with hot methanol (6 h) and hot ethyl acetate

(12 h). The residue was then extracted with chloroform in

a Soxhlet apparatus. The solvent was then removed and

the residue was dissolved in chloroform (10.0 mL) before

precipitating in methanol (50 mL). The resulting solid

was filtered and washed with MeOH and dried under

vacuum to give P6 as a red solid (40 mg, 43%). GPC

(THF, RT): M_n=41.9 kD, M_w=76.9 kD, M_w/M_n=1.8; ele-

mental analysis calcd (%) for P6 (C₅₆H₇₉NO₄S₃)_n: C

72.60, H 8.60, N 1.51; found: C 72.78, H 8.78, N 1.49.

[3] a) J. E. Anthony, A. Facchetti, M. Heeney, S. R. Marder,

X. W. Zhan, Adv. Mater. 2012, 22, 3876; b) J. E. Anthony,

Chem. Rev. 2006, 106, 5028; c) M. Bendikov, F. Wudl, D. F.

Perepichka, Chem. Rev. 2004, 104, 4891.

[4] a) K. Takimiya, S. Shinamura, I. Osaka, E. Miyyazaki, Adv.

Mater. 2011, 23, 4347; b) J. G. Mei, Y. Diao, A. L. Appleton,

L. Fang, Z. N. Bao, J. Am. Chem. Soc. 2013, 135, 6724; c) L.

Isr. J. Chem. 2014, 54, 796 – 816

ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.ijc.wiley-vch.de

814

Full Paper

Cardenas, R. Gutzler, J. Lipton-Duffin, C. Fu, J. L. Brusso,

L. E. Dinca, M. Vondracek, Y. Fagot-Revurat, D. Malterre,

F. Rosei, D. F. Perepichka, Chem. Sci. 2013, 4, 3263.

K. C. Lau, W. K. Li, J. Phys. Chem. A 2005, 109, 7509; d) C.

Schmitz, J. M. Aubry, J. Rigaudy, Tetrahedron 1982, 38,

1425.

[5] a) X. W. Zhan, A. Facchetti, S. Barlow, T. J. Marks, M. A.

Ratner, M. R. Wasielewski, S. R. Mader, Adv. Mater. 2011,

23, 268; b) C. Huang, S. Barlow, S. R. Marder, J. Org. Chem.

2011, 76, 2386; c) A. R. Mohebbi, C. Munoz, F. Wudl, Org.

Lett. 2011, 13, 2560; d) H. Yan, Z. Chen, Y. Zheng, C.

Newman, J. R. Quinn, F. Dçtz, M. Kastler, A. Facchetti,

Nature 2009, 457, 679.

[6] a) J. Li, Y. Zhao, H. S. Tan, Y. Guo, C.-A. Di, G. Yu, Y. Liu,

M. Li, S. H. Lim, Y. Zhou, H. Su, B. S. Ong, Sci. Rep. 2012,

2, 754; b) C. E. Small, S. Chen, J. Subbiah, C. M. Amb, S. W.

Tsang, T. H. Lai, J. R. Reynolds, F. So, Nat. Photonics 2011,

6, 1749; c) Y. Y. Liang, Y. Wu, D. Q. Feng, S.-T. Tsai, H.-T.

Son, G. Li, L. P. Yu, J. Am. Chem. Soc. 2009, 131, 56.

[7] a) X. W. Zhan, Z. A. Tan, B. Domercq, Z. S. An, X. Zhang,

S. Barlow, Y. F. Li, D. B. Zhu, B. Kippelen, S. R. Marder, J.

Am. Chem. Soc. 2007, 129, 7246; b) L. E. Polander, S. P.

Tiwari, L. Pandy, B. M. Selfried, Q. Zhang, S. Barlow, C.

Risko, J. L. Bredas, B. Kippelen, S. R. Marder, Chem. Mater.

2011, 23, 3408.

[8] a) O. Gidron, Y. Diskin-Posner, M. Bendikov, J. Am. Chem.

Soc. 2010, 132, 2148; b) O. Gidron, A. Dadvand, Y. Sheynin,

M. Bendikov, D. F. Perepichka, Chem. Commun. 2011, 47,

1796; c) X.-H. Jin, D. Sheberla, L. J. W. Shimon, M. Bendi-

kov, J. Am. Chem. Soc. 2014, 135, 2592.

[9] a) X. G. Guo, F. S. Kim, S. A. Jenekhe, M. D. Watson, J.

Am. Chem. Soc. 2009, 131, 7206; b) T. Lei, J.-H. Dou, X.-Y.

Cao, J.-Y. Wang, J. Pei, J. Am. Chem. Soc. 2013, 135, 12168;

c) X. G. Guo, J. R. Quinn, Z. Chen, H. Usta, Y. Zheng, Y.

Xia, J. W. Hennek, R. P. Ortiz, T. J. Marks, A. Facchetti, J.

Am. Chem. Soc. 2013, 135, 1986; d) C. Kanimozhi, N. Yaa-

cobi-Gross, K. W. Chou, A. Amassian, T. D. Anthopoulos, S.

Patil, J. Am. Chem. Soc. 2012, 134, 16532; e) M. Seri, A.

Marrocchi, D. Bagnis, R. Ponce, A. Taticchi, T. J. Marks, A.

Facchetti, Adv. Mater. 2011, 33, 3827–3831.

[10] a) B. Walker, C. Kim, T. Q. Nguyen, Chem. Mater. 2010, 23,

470; b) P.-L. T. Boudreault, A. Najari, M. Leclerc, Chem.

Mater. 2010, 23, 456.

[11] a) H. L. Pan, Y. N. Li, Y. L. Wu, P. Liu, B. S. Ong, S. P. Zhu,

G. Xu, J. Am. Chem. Soc. 2007, 129, 4112; b) L. J. Huo, J. H.

Hou, S. Q. Zhang, H. Y. Chen, Y. Yang, Angew. Chem. Int.

Ed. 2010, 49, 1500.

[12] a) Z. C. He, C. M. Zhong, S. J. Su, H. B. Wu, Y. Cao, Nat.

Photonics 2012, 6, 591; b) J. Y. Zhou, Y. Zuo, X. J. Wan,

G. K. Long, Q. Zhang, W. Ni, Y. S. Liu, Z. Li, G. R. He,

C. X. Li, B. Kan, M. M. Li, Y. S. Chen, J. Am. Chem. Soc.

2013, 135, 8484.

[13] a) J. A. Hong, R. Kim, H. J. Yun, J. M. Park, S. C. Shin,

Y. H. Kim, Bull. Korean Chem. Soc. 2013, 34, 1170; b) B. S.

Ong, Y. L. Wu, Y. N. Li, P. Liu, H. L. Pan, Chem. Eur. J.

2008, 14, 4766; c) T. T. M. Dang, S.-J. Park, J.-W. Park, D.-S.

Chung, C. E. Park, Y.-H. Kim, S.-K. Kwon, J. Polym. Sci.

Part A Polym. Chem. 2007, 45, 5277; d) M. A. M. Leenen, F.

Cucinotta, W. Pisula, J. Steiger, R. Anselmanm, H. Thiem,

L. De Cola, Polymer 2010, 51, 3099; e) H. L. Pan, Y. N. Li,

Y. L. Wu, P. Liu, B. S. Ong, S. P. Zhu, G. Xu, Chem. Mater.

2006, 18, 3237; f) H. L. Pan, Y. L. Wu, Y. N. Li, P. Liu, B. S.

Ong, S. P. Zhu, G. Xu, Adv. Funct. Mater. 2007, 17, 3574.

[14] a) H. Yamada, Y. Yamashita, M. Kikuchi, H. Watanabe, T.

Okujima, H. Uno, T. Ogawa, K. Ohara, N. Ono, Chem. Eur.

J. 2005, 11, 6212; b) E. A. Venedictov, E. J. Tulikova, Tetra-

hedron Lett. 2003, 44, 3215; c) S. H. Chien, M. F. Cheng,

[15] S. Alem, S. Wakim, J. Lu, G. Robertson, J. Ding, Y. Tao,

ACS Appl. Mater. Interfaces 2012, 4, 2993.

[16] a) S. Loser, C. J. Bruns, H. Miyauchi, R. Ponce Ortiz, A.

Facchetti, S. J. Stupp, T. J. Marks, J. Am. Chem. Soc. 2011,

133, 8142; b) Q. Peng, Q. Huang, X. Hou, P. Chang, J. Xu,

S. Deng, Chem. Commun. 2012, 48, 11452; c) K. Takimiya,

S. Shinamura, I. Osaka, H. Miyazaki, Adv. Mater. 2011, 23,

4347; d) S. Shinamura, I. Osaka, E. Miyazaki, A. Nakao, B.

Yamagishi, J. Takeya, K. Takimiya, J. Am. Chem. Soc. 2011,

133, 5024; e) H. Kong, S. H. Park, N. S. Cho, S. Cho, H. K.

Shim, J. Polym. Sci. Part A Polym. Chem. 2012, 50, 4119;

f) S. Subramanian, S. K. Park, S. R. Parkin, V. Podzorov,

T. N. Jackson, J. E. Anthony, J. Am. Chem. Soc. 2008, 130,

2706; g) S. Subramanian, Dissertation Thesis, University of

Kentucky (USA), 2008.

[17] A. Facchetti, C. Huang, H. L. Pan, US patent

US2013035464-A1, USA, 2013.

[18] a) I. Osaka, T. Kakara, N. Takemura, T. Koganezawa, K. Ta-

kimiya, J. Am. Chem. Soc. 2013, 135, 8834; b) S. Loser, H.

Miyauchi, J. W. Hennek, J. Smith, C. Huang, A. Facchetti,

T. J. Marks, Chem. Commun. 2012, 48, 8511; c) I. Osaka, T.

Abe, M. Shimawaki, T. Koganezawa, K. Takimiya, ACS

Macro Lett. 2012, 1, 437; d) I. Osaka, T. Abe, S. Shinamura,

K. Takimiya, J. Am. Chem. Soc. 2011, 133, 6852; e) A.

Nakano, S. Shinamura, R. Sugimoto, I. Osaka, E. Miyazaki,

K. Takimiya, Org. Lett. 2012, 14, 5448; f) S. W. Shi, P. Jiang,

S. Q. Yu, L. W. Wang, X. C. Wang, M. Wang, H. Q. Wang,

Y. F. Li, X. Y. Li, J. Mater. Chem. A 2013, 1, 1540; g) W. T.

Lee, D. H. Lee, J. C. Shin, M. J. Cho, D. H. Choi, J. Polym.

Sci. Part A Polym. Chem. 2013, 51, 5280.

[19] S. Shinamura, R. Sugimoto, N. Yanai, N. Takemura, T. Ka-

shiki, I. Osaka, E. Miyazaki, K. Takimiya, Org. Lett. 2012,

14, 4718.

[20] B. Carsten, F. He, H. J. Son, T. Xu, L. P. Yu, Chem. Rev.

2011, 11, 1493.

[21] N. Miyaura, A. Sizuki, Chem. Rev. 1995, 95, 2457.

[22] X. G. Guo, R. Ponce Ortiz, Y. Zheng, M.-G. Kim, S. M.

Zhang, Y. Hu, G. Lu, A. Facchetti, T. J. Marks, J. Am.

Chem. Soc. 2011, 133, 13685.

[23] Q. Zhang, J. M. Tour, J. Am. Chem. Soc. 1997, 119, 5065.

[24] B. Qu, H. Yang, D. Tian, H. Liu, Z. Cong, C. Gao, Z. Chen,

L. Xiao, Z. Gao, W. Wei, Q. Gong, Synth. Met. 2012, 162,

2020.

[25] J. Pommerehne, H. Vestweber, W. Guss, R. F. Mahrt, H.

Bassler, M. Porsch, J. Daub, Adv. Mater. 1995, 7, 551.

[26] J. Chen, M. M. Shi, X. L. Hu, M. Wang, H. Z. Chen, Poly-

mer 2010, 51, 2897.

[27] W. Hong, C. Guo, B. Sun, Z. Q. Yan, C. Huang, Y. Hu, Y.

Zheng, A. Facchetti, Y. N. Li, J. Mater. Chem. C 2013, 1,

5624.

[28] M. Halik, H. Klauk, U. Zschieschang, G. Schmid, S. Pono-

marenko, S. Kirchmeyer, W. Weber, Adv. Mater. 2004, 15,

917.

[29] P. Sonar, S. Singh, P. Leclꢃre, R. Lazzaroni, T. T. Lin, A.

Dodabalapur, A. Sellinger, J. Mater. Chem. 2009, 19, 3228.

[30] L. E. Polander, L. Pandey, S. Barlow, P. Tiwari, C. Risko, B.

Kippelen, J. L. Bredas, S. R. Marder, J. Phys. Chem. C.

2011, 114, 23149.

[31] a) F. Silvestri, A. Marrocchi, M. Seri, C. G. Kim, T. J. Marks,

A. Facchetti, A. Taticchi, J. Am. Chem. Soc. 2010, 132,

Isr. J. Chem. 2014, 54, 796 – 816

ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.ijc.wiley-vch.de

815

Full Paper

6108; b) A. Marrocchi, M. Seri, C. G. Kim, A. Facchetti, A.

Taticchi, T. J. Marks, Chem. Mater. 2009, 21, 2592.

[34] B. C. Thompson, J. M. J. Frꢄchet, Angew. Chem. Int. Ed.

2007, 47, 58.

[35] D. S. Tyson, E. F. Fabrizio, M. J. Panzner, J. D. Kinder, J.-P.

Buisson, J. B. Christensen, M. A. Meadoe, J. Photochem.

Photobiol. A: Chem. 2005, 172, 97.

[32] a) K. Kanai, T. Miyazaki, H. Suzuki, M. Inaba, Y. Ouchi, K.

Seki, Phys. Chem. Chem. Phys. 2010, 12, 273; b) M. Surin, P.

Leclere, R. Lazzaroni, J. D. Yuen, G. Wang, D. Moses, A. J.

Heeger, S. Cho, K. Lee, J. Appl. Phys. 2006, 100, 033712.

[33] J. D. Y. A. R. Mohebbi, J. Fan, C. Munoz, M. F. Wang, R. S.

Shirazi, J. Seifer, F. Wudl, Adv. Mater. 2011, 23, 4644.

[36] Z. H. Peng, Y. C. Pan, Tetrahedron Lett. 2000, 41, 4537.

Received: February 16, 2014

Accepted: March 24, 2014

Isr. J. Chem. 2014, 54, 796 – 816

ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.ijc.wiley-vch.de

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New alkoxy-functionalized naphthodithiophene-based semiconducting oligomers and polymers

DOI: 10.1002/ijch.201400046

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