Structure-property relationship of acceptor-substituted oligothiophenes

Article abstract of DOI:10.1016/j.tet.2010.09.004

A series of oligothiophenes that are end-capped with dicyanovinyl (DCV) and 1,3,2-(2H)-dioxaborine (DOB) moieties has been prepared using standard procedures. Their optoelectronic properties have been investigated by cyclic voltammetry and optical absorption. The optical absorption has been measured both in solution and thin film state.

Full text of DOI:10.1016/j.tet.2010.09.004

Tetrahedron 66 (2010) 8729e8733
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Structureeproperty relationship of acceptor-substituted oligothiophenes
*
M.S. Wrackmeyer , M. Hummert, H. Hartmann, M.K. Riede, K. Leo
€
Institut für Angewandte Photophysik, TU Dresden, George-Bahr-Straße 1, 01069 Dresden, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 31 May 2010
Received in revised form 31 August 2010
Accepted 3 September 2010
Available online 15 September 2010
A series of oligothiophenes that are end-capped with dicyanovinyl (DCV) and 1,3,2-(2H)-dioxaborine
(DOB) moieties has been prepared using standard procedures. Their optoelectronic properties have been
investigated by cyclic voltammetry and optical absorption. The optical absorption has been measured
both in solution and thin film state.
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Oligothiophene
Dioxaborine
Dicyanovinyl
Organic solar cell
Absorber material
1. Introduction
stabilised radical cations and higher charged species, have been
obtained.9 By attaching tricyanovinyl (TCV) groups at both ends of
Oligothiophenes represent a powerful class of functional ma-
terials, which are often used for manufacturing a variety of opto-
electronic devices, such as organic light emitting diodes (OLEDs)1,2
and organic solar cells (OSCs).3e6 Their simple synthesis, high
thermal stability, and strong optical absorption in the visible or
near infrared region make them attractive as absorbers of OSCs.7
oligothiophenes, compounds of the general structure B with
Acc¼eC(CN)]C(CN)2 exhibiting a strong tendency to form stabi-
lised radical anions have been obtained.10,11 In recent studies, oli-
gothiophenes end-capped with dicyanovinyl (DCV) groups and
substituted by alkyl-chains at their backbone have been prepared
and characterised by spectroscopic as well as electrochemical
measurements.5,6,12
Here, we have synthesised a series of alkyl-group free oligo-
thiophenes end-capped with DCV and 1,3,2-(2H)-dioxaborine
(DOB) moieties. Like the TCV and DCV groups, the DOB moieties
have a relatively high electron affinity, which makes them suitable
for tuning the electronic properties of oligothiophenes.13 Until now,
their potential for application in organic semiconducting devices is
not fully explored. The absence of alkyl-chains has a significant
influence on the packing density of the compounds in solid state
and hence the morphology of thin films. Moreover, an influence on
the active layer of an organic heterojunction device is expected,
since the alkyl-chains can act as spacers between the molecules in
the bulk. Therefore, this has an influence on the charge carrier
transport in the layered systems.
Bandgap-engineering can be done both by enlarging the
tem and/or modifying the substituents at the -position of the
thiophene chain.8 The structural modification of a conjugated
-system by certain functional groups is one of the most common
p-sys-
a
,u
p
strategies with respect to their use as electronic materials
(Scheme 1). For instance, by attaching diarylamino moieties at both
ends of oligothiophenes, compounds of the general structure A
(Don¼NAr2) exhibiting strong electron donating properties, in-
dicated by low oxidation potentials and a high tendency to form
Although oligothiophenes end-capped with DCV14,15 and DOB16
moieties are known, a detailed series of these compounds has not
yet been studied. Therefore we have addressed this issue by pre-
paring several new DOB substituted oligothiopenes DOB2-nT
(n¼3,4) and DCV substituted oligothiophenes DCV2-nT (n¼3e6).
The focus lies on the absorption in solution and thin film. Other
important points are the electrochemical properties, investigated
by cyclic voltammetry.
Scheme 1. Donor (Don) and acceptor (Acc) substituted oligothiophenes A and B.
* Corresponding author. Tel.: þ49 351 463 42292; fax: þ 49 351 463 37065;
e-mail address: marion.wrackmeyer@iapp.de (M.S. Wrackmeyer).
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.09.004

8730
M.S. Wrackmeyer et al. / Tetrahedron 66 (2010) 8729e8733
2. Results and discussion
The absorption measurements were performed in dichloro-
methane (DCM). Thin films were prepared by thermal evaporation
in vacuum. To ensure the thermal stability of the compounds we
investigated them by DSC and found a thermal stability up to 320 ꢁC
for the DCV-materials and 275 ꢁC for the DOB-materials. The
electrochemical reduction potentials were measured by cyclic
voltammetry in DCM and the oxidation potentials in acetonitrile
using tetrabutylammonium hexafluorophosphate as electrolyte.
The data derived from these measurements are depicted in Table 1
and in Figs. 1 and 2.
Due to a restricted solubility, the optical absorption of DCV2-5T
and DCV2-6T could only be measured in thin films (Fig. 1 (right)).
The absorption maxima of the DCV derivatives in solution are found
at longer wavelengths than the maxima of the DOB derivatives with
the same number n of thiophene units (Fig. 1 (left), Fig. 2). In
general, a bathochromic shift is observed by increasing the number
n of thiophene units. In contrary, hypsochromic shifts are observed
in thin films by going from DCV2-5T (558 nm) to DCV2-6T (538 nm)
as well as going from solution to thin film for the DOB2-3T (470 nm
in DCM, 410 nm in thin film). This indicates that the molecular
interaction between oligothiophene molecules in solid state is
different from solution and that in thin films, this interaction can
2.1. Synthesis
The synthesis of both types of acceptor-substituted oligothio-
phenes starts from the parent thiophene 1 (Scheme 2). By using
standard procedures, it has been functionalised at first by reaction
with 2 equiv of BuLi in THF at ꢀ78 ꢁC, followed by addition of
2 equiv of tributylstannylchloride to yield 2.17,18 The DOB derivative
4 was synthesised by reacting the bromo compound 3 with acetic
anhydride in presence of BF3 etherate.19 Compound 5b was realized
by using the Vilsmeier reagent, POCl3 and DMF in the first step with
a yield of 84%.20 To obtain the corresponding bromo compound 6b,
the bromination was carried out with NBS in DMF to yield 6b
(96%).20 The DCV compounds 7 have been synthesised by reaction
with malonodinitrile in acetonitrile catalysed by triethylamine.21
The reaction has yields between 35 and 40% and results in dark
red products. Subsequently, the DOB derivative 4 and the DCV
compounds 7 were transformed into the target compounds DOB2-
nT (n¼3,4) and DCV2-nT (n¼3e6) (with n as the number of thio-
phene rings) by Stille-coupling with 2 as reagents and Pd(PPh3)4 as
catalyst.22
Scheme 2. Reaction scheme for the synthesis of DOB2-nT and DCV2-nT.
2.2. Optical and electronic properties
vary significantly. The broadening of the absorptions in the solid
state also indicates that there are more types of molecular in-
teractions (such as J-aggregates or H-aggregates25,26) in thin films
than in solution. The effect of the DOB compound can also be
explained by a strong solvatochromism. Measurements in different
solvents (polar and nonpolar) exhibit a wide range for the ab-
sorption maxima from 411 nm (in THF) to 493 nm (in DMSO). It is
worth mentioning that the DOB compounds have an extinction
coefficient about six times higher than the DCV compounds. Cal-
culation of the transition dipole moment (TDM) is part of future
investigation to explain this phenomenon.
To characterise the redox properties of the prepared compounds,
CV measurements were performed and the results are listed in
Table 1. For the compounds, which were sufficiently soluble in DCM
or acetonitrile, a reversible oxidation and reduction peak was
observed (exemplarily shown for DCV2-4T in Fig. 3). The oxidation
potentials decrease with growing n, whereas the reduction poten-
tials increase simultaneously to a smaller extent. These data in-
dicate that the increase in donor strengths with growing n is more
distinctive than the decrease in acceptor strength.
The optical and electronic properties of organic materials are
important parameters to determine their application in electronic
devices. The compounds listed in Table 1 are designed for working
in the absorbing (intrinsic) layer of an organic small molecule solar
cell.23,24
Table 1
Absorption maxima in solution and thin film, HOMO and LUMO energy levels from
CV for the compounds DOB2-nT and DCV2-nT
Compd
lmax [nm]
Oxidationa
Reductiona
in DCM
in thin-
film
E1/2
[V]
EHOMO
[eV]
E1/2
ELUMO
(
3
[L molꢀ1 cmꢀ1])
[V]
[eV]
DOB2-3T
DOB2-4T
DCV2-3T
DCV2-4T
DCV2-5T
DCV2-6T
470 (454,000)
482 (343,000)
488 (72,000)
517 (78,000)
d
410
486
495
547
558
538
1.39
1.07
1.42
1.02
d
ꢀ5.9
ꢀ5.5
ꢀ5.9
ꢀ5.5
d
ꢀ0.78
ꢀ1.07
ꢀ0.89
ꢀ0.92
d
ꢀ3.7
ꢀ3.4
ꢀ3.6
ꢀ3.4
d
d
d
d
d
d
a
Conditions: Pt-tip-electrode, Ag/AgCl, Pt wire; dry CH3CN (oxidn) and dry
CH2Cl2 (red); 0.1 mol Lꢀ1 Bu4NPF6; 100 mV sꢀ1; E1/2 recalculated to Fc (HOMO
ꢀ4.78 eV).27
The HOMO and LUMO energy levels were calculated from
the reduction and oxidation half-wave potential with reference

M.S. Wrackmeyer et al. / Tetrahedron 66 (2010) 8729e8733
8731
1.0
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
DCV2-3T in DCM
DCV2-3T in DCM
DCV2-3T
DCV2-3T
DCV2-4T in DCM
2-4T
DCV2-4T
DCV2-4T in DCM
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
DCV2-3T thin film
DCV2-5T
DCV2-5T
2-6T
DCV2-6T
DCV2-3T in thin film
DDCCVV2--44TTinthtihninfilmfilm
2
300
500
700
900
300
500
700
900
Wavelength [nm]
Wavelength [nm]
Fig. 1. Absorption spectra of DCV2-3T and DCV2-4T in solution (DCM) and thin film (left) and DCV2-nT (with n¼3e6) in vacuum processed thin films (right).
DOB2-3T in DCM
DOB2-3T in DCM
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
DOB2-4T in DCM
DOB2-4T in DCM
3. Conclusion
DOB2-3T thin film
DOB2-3T in thin film
DOB2-4T thin film
DOB2-4T in thin film
We have investigated the relationship between structure, opti-
cal and electronic properties of a series of acceptor-substituted
oligothiophenes, which are prepared for the absorbing (intrinsic)
layer of organic small molecule solar cells. Our work included the
investigation of two different acceptor groupsddicyanovinyl (DCV)
and 1,3,2-(2H)-dioxaborine (DOB). The synthesis of several accep-
tor-substituted thiophenes with chain-lengths varying from three
to six thiophene units for the case of the DCV compounds and three
and four for the DOB compounds was achieved.
A constant bathochromic tendency in relation to the chain-
length from three to five thiophene rings can be observed for the
DCV compounds. DCV2-6T shows a hypsochromic shift compared to
DCV2-4T and DCV2-5T in vacuum processed thin film.
Compared to the DCV compounds, the DOB compounds show an
outstandingly large extinction coefficient. Comparing the absorp-
tion of the DOB compounds with respect to their chain-lengths, we
discovered a smaller bathochromic shift than our studies revealed
from the DCV compounds. In solution and in thin film, the DOB
compounds showed a hypsochromic shift, that comes from a strong
solvatochromic behaviour of the molecules in solution.
300
500
700
900
Wavelength [nm]
Fig. 2. Absorption spectra of DOB2-nT (n¼3,4) in solution (DCM) and thin film.
The compounds with chain-length of three and four for both
acceptors have been investigated by CV, which yields information
about reversibility and that enlarging the chain-lengths of an
oligomer has larger influences on the HOMO energy level of the
molecules than on the LUMO energy level. Due to a restricted sol-
ubility of the compounds with five and six thiophene rings, a CV
analysis was not possible.
4. Experimental section
4.1. General
Fig. 3. Voltammogram of DCV2-4T.
All reactions were carried out under nitrogen atmosphere using
standard Schlenk techniques. The chemicals (standard and thio-
phene 1a, 2,20-bithiophene 1b, 2-bromothiophene 3 and 5-bromo-
2-carbaldehyde 6a) were purchased from commercial sources
(Aldrich, Alfa-Aeser and ABCR) and used without further purifica-
tion. The solvents were dried according to standard procedures.
2,5-Bis(tributylstannyl)thiophene 2a,17 5,50-bis(tributylstan-
nyl)-2,20-bithiophene 2b,18 2,2-bithiophene-5-carbaldehyde 5b,20
50-bromo-2,20-bithiophene-5-carbaldehyde 6b20 and 4-(2-bromo-
thienyl)-2,2-difluoro-6-methyl-1,3,2-(2H)-dioxaborine 419 were
prepared using literature procedures.
to ferrocene. The HOMO value of ferrocene is ꢀ4.78 eV in DCM
and ꢀ4.84 eV in acetonitrile (e.g., for DCM: EFMO¼ꢀ4.78ꢀ
[E1/2ꢀE1/2(Fc)]).27
The electron affinity is nearly the same for both acceptor groups.
The LUMO level is in a range between ꢀ3.4 eV for the substituted
quaterthiophene and ꢀ3.6 eV (DCV2-3T) to ꢀ3.7 eV (DOB2-3T) for
the terthiophene. The HOMO energy level of both terthiophenes
DOB2-3T and DCV2-3T is at ꢀ5.9 eV, the CV measurement reveals
values of ꢀ5.5 eV for the quaterthiophenes DOB2-4T and DCV2-4T.

8732
M.S. Wrackmeyer et al. / Tetrahedron 66 (2010) 8729e8733
4.1.1. General analytic methods. 1H and 13C NMR spectra were
recorded at room temperature with a Bruker DRX 500 P instrument
at 500.13 and 125.76 MHz. The assignment of quaternary C, CH,
CH2, CH3 was completed using DEPT spectra. Elemental analysis
was done with a Eurovektor Hekatech EA-3000 elemental analyzer.
n
¼3094 (w), 1618 (w), 1558 (m), 1529 (m), 1455 (w), 1424 (m), 1378
(m), 1350 (m), 1284 (w), 1155 (m), 1031 (s), 976 (m), 803 (m), 727
(m), 690 (m), 580 (m), 543 (m) cmꢀ1 1H NMR (500 MHz, CDCl3):
¼8.04 (dd, J¼3.9, 1.0, 2H), 7.85 (dd, J¼4.9, 1.0, 2H), 7.25 (dd, J¼4.8,
4.0, 2H), 6.77 (s, 1H), 1.55 (s, 6H); 13C NMR (125 MHz, CDCl3):
;
d
The UVevis spectra were measured with a PerkineElmer
l
25
d
¼191.6 (C), 174.9 (C), 138.1 (CH), 137.3 (C), 135.3 (CH), 132.7 (CH),
spectrometer. The IR spectra were recorded with a Thermo Nicolet
AVATAR 360 FTIR. The characteristic peaks are listed with an in-
tensity of s¼strong, m¼medium and w¼weak. Mass spectra were
recorded with a Bruker Esquire-LC 00084 instrument. Melting
points were measured with a Stuart apparatus and are uncorrected.
DSC measurements were performed with a Netzsch STA 449 C
under nitrogen atmosphere and with a heating rate of 10 K/min.
128.4 (CH), 126.8 (C), 96.7 (CH), 25.6 (CH3); MS (ESI, ꢀ10 V): m/z:
510.8 [Mꢀ].
4.3.2. 5,5000-Bis(2,2-difluoro-6-methyl-1,3,2-(2H)-dioxaborin-4-yl)-
2,20:50,200:500,2000-quaterthiophene (DOB2-4T). Compound DOB2-4T
was prepared from 2b and 4; mp: >300 ꢁC; C24H16B2F4O4S4: cal-
culated: C 48.51, H 2.71, S 21.58; found: C 48.75, H 2.68, S 21.12; IR
(ATR):
n
¼3137 (w), 3090 (w), 2873 (w), 1979 (w), 1548 (s),1500 (m),
4.1.2. CV-measurements. CV measurements were performed with
a Ag/AgCl-electrode in a typical three-electrode set-up. The con-
ducting salt was tetrabutylammoniumhexafluorophosphat (0.1 M/L)
(recrystallised from ethanol) and ferrocene as an internal standard.
The reduction potentials were measured in dichloromethane, the
oxidation potentials in acetonitrile. The step potential rate was
100 mV sꢀ1. The redox potentialswere recalculated in referencetothe
HOMO level of ferrocene.27
1434 (s), 1377 (m), 1353 (s), 1286 (m), 1256 (m), 1221 (m), 1132 (s),
1036 (s), 976 (m), 877 (m), 788 (s), 723 (m), 699 (s), 659 (m), 578
(m) cmꢀ1
;
1H NMR (500 MHz, DMSO-d6, 363 K):
d
¼8.37 (d, J¼4.3,
2H), 7.71 (d, J¼3.9, 2H), 7.68 (d, J¼4.3, 2H,), 7.43 (d, J¼3.9, 2H,), 7.08
(s, 2H), 2.39 (s, 6H); 13C NMR (125 MHz, DMSO-d6, 363 K):
d¼191.2
(C), 176.7 (C), 137.4 (C), 135.2 (CH), 134.3 (C), 132.7 (CH), 130.9 (C),
128.6 (CH), 126.3 (C), 125.7 (CH), 96.8 (CH), 24.7 (CH3); MS
(ESI, ꢀ10 V): m/z: 593.8 [Mꢀ].
4.1.3. Thin film preparation. The thin films were deposited on
quartz glass by thermal evaporation in vacuum. The base pressure
of the vacuum chamber was better than 10ꢀ6 mbar and the film
thickness monitored by a quartz crystal microbalance.
4.3.3. 5,500-Di(2,2-dicyanovinyl)-2,20:50,200-terthiophene (DCV2-3T).
Compound (DCV2-3T) was prepared from 2a and 7a; mp: 255 ꢁC;
C20H8N4S3: calculated: C 59.98, H 2.01, N 13.99, S 24.02; found: C
59.73, H 1.84, N 12.89, S 23.31; IR (ATR):
n
¼3081 (w), 3023 (w),
2982 (w), 2219 (m), 1573 (m), 1522 (m), 1474 (m), 1458 (w), 1424 (s),
1363 (m),1334 (s),1266 (m),1237 (m),1145 (m),1073 (m),1058 (m),
937 (m), 896 (w), 856 (m), 799 (m), 773 (s), 733 (m), 694 (m), 606
4.2. Synthesis
4.2.1. General instruction for the synthesis of 7. The carbaldehydes
6a or 6b and malononitrile (1.1 equiv) were suspended in aceto-
nitrile. The mixture was warmed to 50e60 ꢁC and a small amount
of triethylamine was added. The suspension was dissolved and
promptly a red precipitation was formed. After cooling to room
temperature the precipitation could be filtered and washed with
acetonitrile to give 7a and 7b in 35e40% yield.
(m), 536 (m) cmꢀ1
;
1H NMR (500 MHz, DMSO-d6):
d
¼8.65 (s, 2H),
7.90 (d, J¼4.3, 2H), 7.73 (m, 4H); 13C NMR (125 MHz, DMSO-d6):
d
¼152.3 (CH), 146.2 (C), 142.4 (CH), 136.7 (C), 134.4 (C), 129.6 (CH),
126.2 (CH), 114.6 (C), 113.9 (C) 75.3 (C); MS (ESI, ꢀ10 V): m/z: 398.8
[Mꢀ], 798.8 [(2M)ꢀ].
4.3.4. 5,5000-Di(2,2-dicyanovinyl)-2,20:50,200:500,2000-quaterthiophene
(DCV2-4T). Compound (DCV2-4T) was prepared from 2b and 7a;
mp: 298 ꢁC; C24H10N4S4: calculated: C 59.73, H 2.09, N 11.61, S
4.2.2. 2-Bromo-5-dicyanovinylthiophene 7a. Compound 7a was
prepared from 6a; mp: 156e158 ꢁC; 1H NMR (500 MHz, CDCl3):
26.58; found: C 59.62, H 1.79, N 10.53, S 26.79; IR (ATR):
n
¼3352
d
¼8.66 (s, 1H), 7.75 (d, J¼4.1, 1H), 7.56 (d, J¼4.1, 1H); 13C NMR
(w), 3087 (w), 3029 (w), 2217 (s), 1617 (w), 1565 (s), 1529 (s), 1508
(m), 1496 (w), 1418 (s), 1347 (m), 1323 (s), 1264 (s), 1144 (m),
1062 (s), 939 (m), 901 (w), 805 (m), 791 (s), 742 (m), 682 (w), 646
(125 MHz, CDCl3):
125.5 (C), 114.2 (C), 113.7 (C), 76.8 (C).
d
¼152.5 (CH), 141.3 (CH), 136.9 (C), 132.8 (CH),
(m), 603 (s), 548 (m) cmꢀ1 1H NMR (500 MHz, DMSO-d6, 353 K):
;
4.2.3. 50-Bromo-5-dicyanovinyl-2,20-bithiophene 7b. Compound 7b
was prepared from 6b; mp: 194e196 ꢁC; 1H NMR (500 MHz, DMSO-
d
¼8.54 (s, 2H), 7.93 (d, 4H, J¼4.2), 7.65 (d, 2H, J¼4.0), 7.63 (d, 2H,
J¼4.1), 7.52 (d, 2H, J¼3.9); 13C NMR (125 MHz, DMSO-d6, 353 K):
d6):
d
¼8.65 (s, 1H), 7.89 (d, J¼4.1, 1H,), 7.61 (d, J¼4.1, 1H), 7.52 (d,
d
¼151.5 (CH), 150.0 (C), 149.1 (C), 138.1 (C), 137.5 (C), 135.2 (C), 134.1
J¼4.0, 1H), 7.35 (d, J¼4.0, 1H); 13C NMR (125 MHz, DMSO-d6):
(C), 131.5 (CH), 130.1 (CH), 126.6 (CH), 125.5 (CH), 64.7 (C); MS
d¼152.6 (CH), 146.1 (C), 142.3 (CH), 136.3 (C), 133.9 (C), 132.6 (CH),
(ESI, þ10 V): m/z: 482.9 [Mþ].
128.5 (CH), 126.0 (CH), 114.8 (C), 114.6 (C), 113.9 (C), 75.2 (C).
4.3.5. 5,50000-Di(2,2-dicyanovinyl)-2,20:50,200:500,2000:5000,20000-quinque-
thiophene (DCV2-5T). Compound DCV2-5T was prepared from 2a
and 7b; mp: 285 ꢁC; C28H12N4S5: calculated: C 59.55, H 2.14, N 9.92,
4.3. General instruction for the synthesis of DOB2-nT and
DCV2-nT
S 28.39; found: C 59.28, H 2.11, N 9.74, S 28.66; IR (ATR):
n
¼3332
The acceptor-substituted bromo compounds 4 or 7 (2 equiv)
were dissolved in DMF and the catalyst (Pd(PPh3)4 3 mol %) was
added. The resulting mixture was heated to 80 ꢁC before adding the
stannylcompound 2 (1 equiv) and refluxed for 5e6 h. A pre-
cipitation was formed, which could be filtered after cooling to room
temperature and washed with DMF. The compounds were purified
by sublimation.
(w), 3098 (w), 3018 (w), 2811 (w), 2456 (w), 2199 (s), 2047 (w),
1617 (w), 1561 (s) 1519 (w), 1496 (m), 1474 (m), 1459 (w), 1408 (s),
1385 (s), 1343 (s), 1314 (s), 1262 (s), 1226 (s), 1133 (s), 1047 (s), 926
(s), 786 (s), 648 (s), 596 (s), 528 (s) cmꢀ1
.
4.3.6. 5,500000-Di(2,2-dicyanovinyl)-2,20:50,200:500,2000:5000,20000:50000,200000
-
sexithiophene (DCV2-6T). Compound (DCV2-6T) was prepared from
2b and 7b; mp: 300 ꢁC; C32H14N4S6: calculated: C 59.42, H 2.18, N
8.66, S 29.74; found: C 58.61, H 2.17, N 8.47, S 29.66; IR (ATR):
4.3.1. 5,500-Bis(2,2-difluoro-6-methyl-1,3,2-(2H)-dioxaborin-4-yl)-
2,20:50,200-terthiophene (DOB2-3T). Compound (DOB2-3T) was pre-
pared from 2a and 4; mp: 270 ꢁC; C20H14B2F4O4S3: calculated: C
46.90, H 2.76, S 18.78; found: C 46.83, H 2.71, S 18.53; IR (ATR):
n¼3144 (w), 3066 (w), 3025 (w), 2220 (m), 2051 (w), 1607 (w), 1569
(m), 1484 (w), 1424 (m), 1343 (m), 1260 (m), 1218 (m), 1144 (m),

M.S. Wrackmeyer et al. / Tetrahedron 66 (2010) 8729e8733
8733
8. Xia, P. F.; Feng, X. J.; Lu, J.; Tsang, S.-W.; Movileanu, R.; Tao, Y.; Wong, M. S. Adv.
Mater. 2008, 20, 4810.
9. Rohde, D.; Dunsch, L.; Tabet, A.; Hartmann, H.; Fabian, J. J. Phys. Chem. 2006,
1071 (m), 921 (m), 856 (m), 832 (s), 791 (s), 714 (s), 606 (s), 553
(s) cmꢀ1
.
110B, 8223.
10. Papenfus, T. M.; Burand, M. W.; Janzen, D. E.; Mann, K. R. Org. Lett. 2003, 5, 1535.
11. Xia, P. F.; Feng, X. J.; Lu, J.; Movileanu, R.; Tao, Y.; Baribeau, J.-M.; Wong, M. S.
J. Phys. Chem. C 2008, 112, 16714.
12. Liu, Y.; Zhou, J.; Wan, X.; Chen, Y. Tetrahedron 2009, 65, 5209.
13. Fabian, J.; Hartmann, H. J. Phys. Org. Chem. 2004, 17, 359.
14. Pfeiffer, M.; Schueppel, R.; Uhrich, C.; Petrich, A.; Leo, K.; Baeuerle, P.; Kilickiran,
P.; Brier, E. WO 2006092135, 2006; Chem. Abstr. 2006, 145, 317960.
15. Halik, M.; Schmid, G.; Davis, L. DE 2001-10152938 2001, US 2002-281828 2002,
US 2004-993117, 2004; Chem. Abstr. 2002, 137, 378622.
Acknowledgements
This work was funded by the German Federal Ministry of Edu-
cation and Research (BMBF) through the InnoProfile program
(03IP602).
Supplementary data
16. Zotti, G.; Zecchin, S.; Vercelli, B.; Berlin, A.; Grimoldi, S.; Pasini, M. C.; Raposo,
M. M. M. Chem. Mater. 2005, 17, 6492.
17. Hou, J.; Tan, Z.; Yan, Y.; He, Y.; Yang, C.; Li, Y. J. Am. Chem. Soc. 2006, 128, 4911.
18. Huang, J.; Miragliotta, J.; Becknell, A.; Katz, H. E. J. Am. Chem. Soc. 2007, 129,
9366.
Supplementary data associated with this article can be found in
the online version, at doi:10.1016/j.tet.2010.09.004.
19. Goerlitz, G.; Hartmann, H.; Nuber, B.; Wolff, J. J. J. Prakt. Chem. 1999, 341, 167.
20. Chen, R.; Yang, X.; Tian, H.; Wang, X.; Hagfeldt, A.; Sun, L. Chem. Mater. 2007, 19,
4007.
References and notes
21. Raposo, M. M. M.; Fonseca, A. M. C.; Kirsch, G. Tetrahedron 2004, 60, 4071.
22. Stille, J. K. Angew. Chem., Int. Ed. Engl. 1986, 25, 508.
23. Maennig, B.; Drechsel, J.; Gebeyehu, D.; Simon, P.; Kozlowski, F.; Werner, A.; Li,
F.; Grundmann, S.; Sonntag, S.; Koch, M.; Leo, K.; Pfeiffer, M.; Hoppe, H.;
Meissner, D.; Sariciftci, N. S.; Riedel, I.; Dyakonov, V.; Parisi, J. Appl. Phys. 2004,
79, 1.
24. Riede, M.; Mueller, T.; Tress, W.; Schueppel, R.; Leo, K. Nanotechnology 2008, 19,
424001/1.
25. Plekhanov, A. I.; Gorkovenko, A. I.; Orlova, N. A.; Simanchuk, A. E.; Shelkovni-
1. Mitschke, U.; Baeuerle, P. J. Mater. Chem. 2000, 10, 1471.
2. Mazzeo, M.; Pisignano, D.; Favaretto, L.; Barbarella, G.; Cingolani, R.; Gigli, G.
Synth. Met. 2003, 139, 671.
3. Videlot, C.; Kassmi, A. E.; Fichou, D. Sol. Energy Mater. Sol. Cells 2000, 63, 69.
4. Wynands, D.; Levichkova, M.; Riede, M.; Pfeiffer, M.; Baeuerle, P.; Rentenberger,
R.; Denner, P.; Leo, K. J. Appl. Phys. 2010, 107, 014517.
5. Schulze, K.; Uhrich, C.; Schüppel, R.; Leo, K.; Pfeiffer, M.; Brier, E.; Reinold, E.;
€
Bauerle, P. Adv. Mater. 2006, 18, 2872.
kov, V. V. High Energy Chem. 2009, 43, 607.
26. Li, Y.-X.; Tao, X.-T.; Wang, F.-J.; He, T.; Jiang, M.-H. Org. Electron. 2009, 10, 910.
27. Connelly, N. G.; Geiger, W. E. Chem. Rev. 1996, 96, 877.
6. Schulze, K.; Riede, M.; Brier, E.; Reinold, E.; Baeuerle, P.; Leo, K. J. Appl. Phys.
2008, 104, 074511.
7. Mishra, A.; Ma, C.-Q.; Baeuerle, P. Chem. Rev. 2009, 109, 1141.