Synthesis and crystal structure of 5,12-diphenyl-6,11-bis(thien-2-yl)tetracene

Article abstract of DOI:10.1016/j.molstruc.2008.02.007

5,12-Diphenyl-6,11-bis(thien-2-yl)tetracene (1) was prepared by reduction of 5,12-diphenyl-6,11-bis(thien-2-yl)-6,11-tetracenediol (3) with NaBH₃CN in the presence of weak Lewis acid ZnI₂. A rearranged byproduct, 6,11-dihydro-5,12-diphenyl-6,6′-bis(thien-2-yl)-11,11′-dihyd rotetracene (5), was also obtained under this condition. Treatment of compound 3 with HI or other strong Lewis acid led to rearrangement and afforded 5,12-diphenyl-6,6′-bis(thien-2-yl)tetracene-11-one (4). The structures of compounds 1, 4 and 5 were confirmed by single crystal X-ray diffraction. The central tetracene rings of molecules 1 are twisted and assemble into arrays with slip parallel molecules in the crystal structure. There is no π-π overlap among the tetracene rings or among the pendant phenyl rings and thienyl rings.

Full text of DOI:10.1016/j.molstruc.2008.02.007

Available online at www.sciencedirect.com
Journal of Molecular Structure 889 (2008) 265–270
www.elsevier.com/locate/molstruc
Synthesis and crystal structure of 5,12-diphenyl-6,
11-bis(thien-2-yl)tetracene
Yanhui Hou a, Xiaoliu Chi b, Xiangjian Wan a, Yongsheng Chen a,*
a Key Laboratory for Functional Polymer Materials and Center for Nanoscale Science and Technology, Institute of Polymer Chemistry, College of Chemistry,
Nankai University, Weijin Road 94, Tianjin 300071, China
b Department of Chemistry, Texas A&M University – Kingsville, Kingsville, TX 78363, USA
Received 21 January 2008; received in revised form 9 February 2008; accepted 11 February 2008
Available online 19 February 2008
Abstract
5,12-Diphenyl-6,11-bis(thien-2-yl)tetracene (1) was prepared by reduction of 5,12-diphenyl-6,11-bis(thien-2-yl)-6,11-tetracenediol (3)
with NaBH3CN in the presence of weak Lewis acid ZnI2. A rearranged byproduct, 6,11-dihydro-5,12-diphenyl-6,60-bis(thien-2-yl)-11,
110-dihydrotetracene (5), was also obtained under this condition. Treatment of compound 3 with HI or other strong Lewis acid led to
rearrangement and afforded 5,12-diphenyl-6,60-bis(thien-2-yl)tetracene-11-one (4). The structures of compounds 1, 4 and 5 were confirmed
by single crystal X-ray diffraction. The central tetracene rings of molecules 1 are twisted and assemble into arrays with slip parallel mol-
ecules in the crystal structure. There is no p–p overlap among the tetracene rings or among the pendant phenyl rings and thienyl rings.
Ó 2008 Elsevier B.V. All rights reserved.
Keywords: Tetracene; Crystal structure; Synthesis; Rearrangement; Reduction
1. Introduction
peculiar electronic and optoelectronic materials, which
has been successfully used in many organic semi-conductor
devices [13–15]. Herein we wish to report the synthesis of a
new thienyl substituted rubrene derivative, 5,12-diphenyl-
6,11-bis(dithien-2-yl)tetracene (1) (Chart 1). Although
chemical structure of compound 1 is very similar to that
of rubrene, the synthesis procedure and the crystal struc-
ture of 1 are obviously different from those of rubrene.
And two rearranged compounds were also obtained, unex-
pectedly. Their structures were all confirmed by the single
crystal X-ray diffractions.
The polycyclic aromatic hydrocarbon (PAH), rubrene
(5,6,11,12-tetraphenyltetracene) has been widely investi-
gated for more than three decades [1,2]. Over past few
years, rubrene has offered one of the best materials for
organic electronic and optoelectronic devices due to its
high mobility. And it has been successfully used in organic
light-emitting diodes (OLED) [3–5] and organic field-effect
transistors (OFETs) [6–9]. For its wide variety of interest-
ing properties, there has been an increasing interest in the
synthesis of new specifically substituted rubrene derivatives
in the last years. However, these rubrene derivatives were
mostly prepared by introduction of substituent on the pen-
dant phenyl rings, rather than directly on the tetracene
backbone ring [10–12]. As an electron-rich substituent, thi-
enyl has been used as a popular building block for many
2. Experimental
2.1. General
NMR spectra were obtained on a Bruker AC-300 Spec-
trometer (300-MHz) as CDCl3 solution using TMS as the
internal standard. Elemental analyses were performed
using a Thermo Electron FLASH/EA 1112 instrument.
Mass spectra were carried out on a Thermofinnigan LCQ
*
Corresponding author. Tel.: +86 22 23500693; fax: +86 22 23499992.
E-mail address: yschen99@nankai.edu.cn (Y. Chen).
0022-2860/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2008.02.007

266
Y. Hou et al. / Journal of Molecular Structure 889 (2008) 265–270
for C38H24OS2: C, 81.40; H, 4.31; O, 2.85; S, 11.44%.
Found: C, 81.44; H, 4.26; O, 2.81; S, 11.49%.
S
2.2.3. 5,12-Diphenyl-6,11-bis(thien-2-yl)tetracene (1) and
6,11-dihydro-5,12-diphenyl- 6,60-bis(thien-2-yl)-11,
110-dihydrotetracene (5)
S
A suspension of diol 3 (0.64 g, 1.1 mmol), ZnI2 (1.01 g,
3.4 mmol) and NaBH3CN (0.69 g, 11 mmol) in 1,2-dichlo-
roethane (10 mL) was refluxed (under argon and protected
from light) for 20 h. After cooling to room temperature,
dichloromethane (30 mL) was added and the solids were
filtered off. The clear filtrated was washed with diluted
HCl (3 M, 3 ꢁ 30 mL) and dried (MgSO4), then concen-
trated in vacuum. The residue was purified by column
chromatography (SiO2, eluent–hexanes) to give compound
1 (yield 57%) as red crystals and the byproduct 5 as white
crystals (yield 30%).
rubrene
1
Chart 1. Chemical structures of rubrene and compound 1.
Advantage mass spectrometer. All reagents are commer-
cially available and purified by standard methods prior to
use. 6,11-Diphenyl-5,12-tetracenequinone (2) was synthe-
sized as described in the literature [16].
Compound 1 was a red solid: Mp 248–250 °C. 1H NMR
(400 MHz, CDCl3): d 7.57–7.54 (m, 2H), 7.42 (broad, 2H),
7.23–7.13 (m, 14H), 6.93 (broad, 2H), 6.73 (broad, 2H),
6.44 (broad, 2H). MS (EI) m/z 544 (M+). Elemental anal-
ysis calcd for C38H24S2: C, 83.79; H, 4.44; S, 11.77%.
Found: C, 83.85; H, 4.47; S, 11.68%.
2.2. Synthesis
2.2.1. 5,12-Diphenyl-6,11-bis(thien-2-yl)-6,11-tetracenediol (3)
To 6,11-diphenyl-5,12-tetracenequinone (5.1 g, 12.5 mmol)
in 150 ml dry THF at ꢀ78 °C under argon atmosphere,
1 M 2-thienyllithium THF solution (30 mL) was added
slowly. The mixture was allowed to slowly warm up to
room temperature and stirred overnight. The reaction
was worked up with aqueous solution of saturated NH4Cl,
and extracted with Et2O. The combined organic extracts
were dried (MgSO4) and then concentrated in vacuum.
The resulting solid was washed thoroughly with 4:1 hex-
anes–Et2O to give an off-white solid (yield 87%). Mp 172–
174 °C. 1H NMR (400 MHz, d-acetone): d 7.62 (d,
J = 7.4 Hz, 2H), 7.48–7.45 (m, 4H), 7.31 (t, J = 7.4 Hz,
2H), 7.20–7.19 (m, 2H), 7.09–6.98 (m, 8H), 6.65 (t,
J = 4.3 Hz, 2H), 6.44 (d, J = 5.4 Hz, 2H), 6.22 (d,
J = 7.5 Hz, 2H), 5.62 (s, 2H). MS (EI) m/z 578 (M+). Ele-
mental analysis calcd for C38H26O2S2: C, 78.86; H, 4.53; O,
5.53; S, 11.08%. Found: C, 78.79; H, 4.51; O, 5.58; S,
11.12%.
Compound 5 was a white solid: Mp 286–288 °C. 1H
NMR (400 MHz, d-acetone):
d 7.62–7.53 (m, 3H),
7.44–7.39 (m, 3H), 7.28 (t, J = 6.6 Hz, 1H), 7.17
(t, J = 7.4 Hz, 1H), 7.07–6.90 (m, 10H), 6.83 (d, J =
6.8 Hz, 2H), 6.65–6.60 (m, 4H), 3.86 (s, 2H). MS (EI)
m/z 546 (M+). Elemental analysis calcd for C38H26S2: C,
83.48; H, 4.79; S, 11.73%. Found: C, 83.54; H, 4.75; S,
11.71%.
2.3. X-ray crystallography
The diffraction-quality single crystals of 1, 4, 5 were
mounted on glass fibers in random orientation using
epoxy-glue. Bruker SMART 1000 CCD automatic diffrac-
tometer was used for data collection at T = 294(2) K
using graphite monochromated MoKa-radiation (k =
˚
0.71073 A). The structures were solved by direct methods,
and all non-hydrogen atoms were subjected to anisotropic
refinement by full-matrix least squares on F2 using the
SHELXTL package. More details on data collection and
structure calculation are summarized in Table 1. Crystallo-
graphic data for all structures reported here have been
deposited with the Cambridge Crystallographic Data Cen-
tre; CCDC numbers are given in Table 1.
2.2.2. 5,12-Diphenyl-6,60-bis(thien-2-yl)tetracene-11-one (4)
To a 50 mL Et2O solution of diol 3 (1.15 g, 2 mmol),
57% HI water solution (50 mL) was added at room tem-
perature. The mixture was stirred for 0.5 h before addi-
tion of
a
saturated aqueous solution of sodium
metabisulfite. The aqueous portion was extracted with
Et2O, and the combined organic extracts immediately
dried (MgSO4) and concentrated in vacuo to give a
red solid, which was recrystallized from CHCl3–acetone
to give 4 as a bright red crystalline solid (yield 82%).
Mp 262–264 °C; 1H NMR (400 MHz, CDCl3): d 7.82
(d, J = 7.6 Hz, 1H), 7.64–7.51 (m, 4H), 7.45–7.43
(m, 2H), 7.39–7.29 (m, 2H), 7.21–7.18 (m, 3H), 7.08–
7.06 (m, 4H), 7.02–6.97 (m, 2H), 6.71 (d, J = 3.7 Hz,
2H), 6.64 (t, J = 5.1 Hz, 2H), 6.57 (d, J = 8.1 Hz, 2H).
MS (ESI) m/z 561 (MH+). Elemental analysis calcd
3. Results and discussion
3.1. Synthesis
The key intermediate, 5,12-diphenyl-6,11-bis(thien-2-
yl)-6,11-tetracenediol (3), was synthesized, by the addition
of 5,12-diphenyl-6,11-tetracenequinone (2) with thienylli-
thium (Scheme 1), and fully characterized. HI has been
used widely to reduce tetracenediols for rubrene derivatives

Y. Hou et al. / Journal of Molecular Structure 889 (2008) 265–270
267
Table 1
Experimental data for the X-ray diffraction studies of prepared compounds at 294(2) K
1
4
5
No. in CCDC
Empirical formula
Formula weight
Crystal system
Space group
659,313
C38H24S2
544.69
Monoclinic
P21/c
22.036(4)
8.8034(17)
30.252(6)
90
659,311
659,312
C38H26S2
546.71
Monoclinic
P21/n
18.463(6)
8.190(3)
18.624(7)
90
98.288(6)
90
2786.7(16)
4
C38H24OS2ꢂ1.5C4H8O
668.85
Monoclinic
C2/c
35.265(5)
9.4510(14)
23.373(4)
90
115.779(3)
90
7014.7(18)
8
˚
a (A)
˚
b (A)
˚
c (A)
a (°)
b (°)
c (°)
104.921(4)
90
5671(2)
3
˚
V (A )
Z
8
Dcalcd (mg/m3)
Crystal size (mm)
1.276
1.267
1.303
0.22 ꢁ 0.20 ꢁ 0.18
0.20 ꢁ 0.18 ꢁ 0.14
0.20 ꢁ 0.16 ꢁ 0.10
l (mmꢀ1
F (000)
)
0.214
0.191
0.218
2272
2816
1144
h Range for data col. (°)
1.39–25.02
ꢀ16 h 6 26,
ꢀ10 6 k 6 10,
ꢀ36 6 l 6 33
100
1.80–25.01
ꢀ39 6 h 6 41,
ꢀ11 6 k 6 10,
ꢀ27 6 l 6 19
98.4
1.45–25.02
ꢀ21 6 h 6 21,
ꢀ9 6 k 6 5,
ꢀ22 6 l 6 21
98.1
Index ranges
Completeness (%)
Reflections collected/unique
Rint
28,527/10,019
0.1077
17,383/6084
0.0618
13,229/4832
0.1674
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
10,019/0/721
1.008
6084/269/501
1.064
4832/167/399
1.030
R1 = 0.0691,
wR2 = 0.1491
R1 = 0.1981,
wR2 = 0.1984
0.313 and ꢀ0.422
R1 = 0.0760,
wR2 = 0.1920
R1 = 0.1561,
wR2 = 0.2468
0.509 and ꢀ0.384
R1 = 0.0783,
wR2 = 0.1488
R1 = 0.2369,
wR2 = 0.2049
0.330 and ꢀ0.369
R indices (all data)
Largest diff. peak and hole (e Aꢀ3
)
S
O
O
Th OH
2 ThLi, THF
-78 oC
HI
+
25 C
˚
Th
HO
Th Th
O
S
S
Th=
2
3
1
4
(<1%)
Scheme 1. Synthesis of compound 3. Reaction of 3 with HI mainly to give rearranged compound 4.
[16]. However, when 5,12-diphenyl-6,11-bis(thien-2-yl)-
6,11-tetracenediol (3) was reacted with HI acid under the
literature condition, the expected 5,12-diphenyl-6,11-
bis(thien-2-yl)tetracene (1) was produced in rather small
yield (<1%) and the main product was a rearranged com-
pound, 5,12-diphenyl-6,60-bis(thien-2-yl)tetracene-11-one
(4, Scheme 1). The structure of compound 4 was confirmed
by single crystal X-ray diffraction study (Fig. 1). Appar-
ently, the unexpected product 4 is formed by migration
of the thienyl ring.
tic acid. Similarly, this method also converted the diol 3
mainly to the rearranged product 4. It is obvious that
the thienyl ring on the tetracene migrates quite easily
under strong Lewis acid condition such as in HI or ace-
tic acid. We noticed that the reduction of analogous
anthracenediol derivatives was successfully achieved by
treating them with ZnI2 (as weak Lewis acid) and
NaBH3CN (as reductant) in 1,2-dichloroethane [20]. So
we used the same method to reduce the diol 3. Indeed,
this condition gave the desired compound 1 with 57%
yield (Scheme 2). Interestingly, another byproduct was
isolated under this condition. By X-ray crystallographic
analysis, we found that it was another rearranged com-
Indeed, some electron-rich substituents favor rear-
rangement in the preparation of substituted anthracene
and pentacene derivatives [17–19]. We also used KI/
NaH2PO2 to try the reduction reaction in refluxing ace-
pound,
6,11-dihydro-5,12-diphenyl-6,60-bis(thien-2-yl)-

268
Y. Hou et al. / Journal of Molecular Structure 889 (2008) 265–270
Fig. 2. Molecular structure of compound 5. Thermal ellipsoids have been
drawn at the 30% probability level.
Fig. 1. Molecular structure of compound 4. Thermal ellipsoids have been
drawn at the 30% probability level.
3.2. Crystal structures
Compound 4 easily crystallized as bright red prisms
from tetrahydrofuran (THF) in monoclinic space group
C2/c (Z = 8). The crystal structure of 4 consists of one mol-
ecule of 4 and two THF solvate molecules, one with partial
occupancy (50%). Compound 5 crystallized as white prisms
from CHCl3–acetone in monoclinic space group P21/n
(Z = 4). Lattice parameters and other crystallographical
data of 4 and 5 are given in Table 1.
11,110-dihydrotetracene 5 (Fig. 2). Because NaBH3CN
can reduce ketones and alcohols to the corresponding
alkanes in the presence of ZnI2 [18,21], we suspect that
this byproduct was formed by the reduction of the
rearranged product 4. Although the side-reactions
seemed inevitable, this reduction condition provided
acceptable yield of compound 1. The absorption and
The single crystal suitable for the X-ray diffraction
study of compound 1 was grown from CH2Cl2–MeOH
solution. Compound 1 crystallizes in the common mono-
clinic space group P21/c (Z = 8). The crystal structure of
compound 1 is depicted in Fig. 4. Two molecules of 1
were present in the crystal as crystallographically indepen-
dent molecules. Clearly, the tetracene ring of 1 is twisted,
photoluminescent (PL) spectra of compound
1 in
CH2Cl2 solution are presented in Fig. 3. The maximum
absorption of compound 1 is at 300 nm. And there also
have broad weak absorptions about at 450–550 nm.
Compound
1 shows strong orange fluorescence in
CH2Cl2 solution [kmax(CH2Cl2) = 589 nm, quantum
yield = 45%].
S
Th OH
ZnI2
NaBH3CN
+
+
ClCH2CH2Cl, refluxing
Th Th
HO Th
S
S
Th=
5
1 (57%)
Scheme 2. Reaction of 3 with ZnI2 and NaBH3CN to give compound 1 and rearranged compound 5.

Y. Hou et al. / Journal of Molecular Structure 889 (2008) 265–270
269
is 36°. The stacking of molecules 1 is illustrated in
Fig. 5. The tetracene rings of molecules 1 assemble into
an array with slip parallel molecules and the adjacent
two molecules are not face to face directly in the array.
The separation between two adjacent parallel molecules
˚
is 6.8 A. This length is larger than the typical van der
Waals interaction distance in a C–C p-stack [22,23]. So
there is no p–p stacking interaction among the tetracene
rings in the arrays. Also because of the twist of the tetra-
cene ring, the pendant phenyl rings and thienyl rings have
no overlap in the individual molecule. These structure
characteristics are quite different from that of rubrene
[9,22], where the tetracene ring is nearly planar and the
tetracene rings form p–p overlap in the crystal. The
replacement of the two pendant phenyl rings with two thi-
enyl rings results in significant change of the molecular
structures.
Fig. 3. UV–vis absorption and photoluminescence (PL) spectra of
compound 1 measured in dilute CH2Cl2 solution. Compound 1 shows
strong orange fluorescence [kmax(CH2Cl2) = 589 nm].
We had expected that compound 1 might show high
mobility. Thus high pure single crystal of compound 1
was grown by horizontal physical vapor transport in a
stream of ultra high purity argon. We have fabricated
not as expected as planar. To the two independent mole-
cules, the twist directions of the tetracene rings are
reversed and the two twist angels are different. The end
to end twist of molecule I is 27.9°; that of molecule II
Fig. 4. (a) Molecular structure of compound 1; both of the crystallographically independent molecules are shown. (b) Stereoview of the
crystallographically independent molecules. Thermal ellipsoids have been drawn at the 30% probability. To the two independent molecules, the twist
directions of the tetracene rings are reversed.

270
Y. Hou et al. / Journal of Molecular Structure 889 (2008) 265–270
Acknowledgements
We gratefully acknowledge the financial support from the
NSFC (#20644004, #20774047), MoST (#2006CB932702)
and NSF of Tianjin City (#07JCYBJC03000).
Appendix A. Supplementary data
Crystallographic data for all structures reported here
have been deposited with the Cambridge Crystallographic
Data Centre; CCDC numbers are given in Table 1. Copies
of the data can be obtained free of charge on application to
CCDC, e-mail: deposit@ccdc.cam.ac.uk.
References
[1] B.E. Algar, B. Stevens, J. Phys. Chem. 74 (1970) 3029.
[2] P.B. Merkel, W.G. Herkstoeter, Chem. Phys. Lett. 53 (1978) 350.
[3] Y.C. Tsai, J.H. Jou, Appl. Phys. A 89 (2006) 243521.
[4] W.C.H. Choy, Y.S. Wu, C.H. Chen, K.W. Cheah, Appl. Phys. A 81
(2005) 517.
[5] Y. Qiu, Y.D. Gao, L.D. Wang, P. Wei, L. Duan, D.Q. Zhang, G.F.
Dong, Appl. Phys. Lett. 81 (2002) 3540.
[6] A.L. Briseno, S.C.B. Mannsfeld, M.M. Ling, S.H. Liu, R.J. Tseng, C.
Reese, M.E. Roberts, Y. Yang, F. Wudl, Z.N. Bao, Nature 444 (2006)
913.
[7] N. Stingelin-Stutzmann, E. Smits, H. Wondergem, C. Tanase, P.
Blom, P. Smith, D. de Leeuw, Nat. Mater. 4 (2005) 601.
[8] E. Menard, A. Marchenko, V. Podzorov, M.E. Gershenson, D.
Fichou, J.A. Rogers, Adv. Mater. 18 (2006) 1552.
Fig. 5. Packing structure of molecule 1 in single crystal. Hydrogen atoms
have been omitted for clarity and thermal ellipsoids have been drawn at
the 30% probability level. The tetracene rings of molecules 1 assemble into
an array with slip parallel molecules.
FET devices using its single crystals, but disappointedly no
FET property was observed. This is probably due to the
twist of the tetracene ring of 1 as discussed above, which
makes it difficult to form the enhanced intermolecular
p–p overlap as rubrene, and no FET property could be
observed.
[9] V.C. Sundar, J. Zaumseil, V. Podzorov, E. Menard, R.L. Willett, T.
Someya, M.E. Gershenson, J.A. Rogers, Science 303 (2004) 1644.
[10] C.T. Brown, T.K. Hatwar, M.L. Rick, US Patent 2005271899.
[11] T. Tsujioka, Japanese Patent 2003073664.
[12] Y. Hamada, T. Tsujioka, Japanese Patent 2003055652.
´
[13] A.R. Murphy, J.M.J. Frechet, Chem. Rev. 107 (2007) 1066.
[14] I.F. Perepichka, D.F. Perepichka, H. Meng, F. Wudl, Adv. Mater. 17
(2005) 2281.
4. Conclusions
[15] N. Somanathan, S. Radhakrishnan, Int. J. Mod. Phys. B 19 (2005)
4645.
[16] J.A. Dodge, J.D. Bain, A.R. Chamberlin, J. Org. Chem. 55 (1990)
4190.
[17] M. Smet, J.V. Dijk, W. Dehaen, Tetrahedron 55 (1999) 7859.
[18] N. Vets, M. Smet, W. Dehaen, Synlett (2005) 217.
[19] N. Vets, H. Dilie¨n, S. Toppet, W. Dehaen, Synlett (2006) 1359.
[20] M. Smet, J.V. Dijk, W. Dehaen, Synlett (1999) 495.
In summary, 5,12-diphenyl-6,11-bis(thien-2-yl)tetra-
cene (1) was successfully synthesized by the reduction
of
5,12-diphenyl-6,11-bis(thien-2-yl)-6,11-tetracenediol
(3) with NaBH3CN in the presence of ZnI2. Because
of the thienyl migration, two rearranged products, 4
and 5, were also obtained. The structure of 1 is quite
different from that of rubrene and the significant twist
of the tetracene ring of 1 destroys the p–p overlap
existed in rubrene.
´
´ ´
[21] C.K. Lau, C. Dufresne, P.C. Belanger, S. Pietre, J. Scheigetz, J. Org.
Chem. 51 (1986) 3038.
[22] O.D. Jurchescu, A. Meetsma, T.T.M. Palstra, Acta Cryst. B 62 (2006)
330.
[23] A. Bondi, J. Phys. Chem. 68 (1964) 441.