4
L. Duan et al. / Tetrahedron xxx (2016) 1e8
(
6
3
d, J ¼ 3.8 Hz, 2H), 6.86 (d, J ¼ 3.8 Hz, 2H), 6.56 (d, J ¼ 3.6 Hz, 2H),
3.2. Thermal stability and crystallinity
.41 (d, J ¼ 3.6 Hz, 2H), 3.90 (b, 4H), 2.97 (d, J ¼ 5.4 Hz, 2H), 1.83 (b,
H), 1.53e1.05 (m, 24H), 0.98e0.80 (m, 18H). Elementary Analysis
The thermal properties of BDTx-2TVTDPP and BDTy-2TVTDPP
Calculated for C114
H
130
N
4
O
4
S
12; C, 68.29; H, 6.54; N, 2.79; Found: C,
were investigated by thermogravimetric analysis (TGA), which
ꢀ
6
8.27; H, 6.58; N, 2.85. MALDI-MS (m/z): 2003.68; Found: 2003.828
were carried out under a N
2
atmosphere at a heating rate of 10 C/
þ
[M ].
min. The resulting TGA curves and their detailed data are shown in
Fig. S1 and Table 1, respectively. A thermal degradation tempera-
ꢀ
ture (T
d
) over 400 C is observed for both SMs at 5% weight loss.
2
.4.5. Synthesis of compound 8
To a solution of compound 4 (419 mg, 0.60 mmol) and com-
Furthermore, BDTy-2TVTDPP exhibits higher thermal stability than
BDTx-2TVTDPP owing to different substituted positions of BDT. In
order to further study their crystallinity, both differential scanning
calorimetry (DSC) and X-ray diffraction (XRD) were measured. The
resulting DSC and XRD curves are depicted in Figs. 2 and 3,
respectively. A single melting peak (T
and an obvious crystallization peak (T
TVTDPP are observed. Moreover, BDTx-2TVTDPP exhibits an
value by at least 50 C in comparison to BDTy-
TVTDPP, implying that BDTx-2TVTDPP has stronger intermolec-
ular interaction. In addition, three clearly visible diffraction peaks at
values of 5.9 , 17.6 and 24.8 are observed for the BDTx-
TVTDPP neat film, which correspond to its d-spacing of 15.0, 5.1
and 3.6 Å, respectively. However, there was no diffraction peak for
the BDTy-2TVTDPP neat film, indicating that BDTx-2TVTDPP has a
better crystallinity than BDTy-2TVTDPP in the neat films.
pound 7 (244 mg, 0.30 mmol) in THF (20 mL), which was degassed
with nitrogen atmosphere for 30 min at RT under stirring, was
added dropwise another solution of potassium tertbutoxide
(
84 mg, 0.64 mmol) in THF (6 mL). The reaction mixture was stirred
ꢀ
M
) over 209 C for both SMs
ꢀ
for 5 h at RT and 12 h at 60 C successively. After cooled to RT, the
resulting mixture was extracted with DCM (100 mL). The collected
organic phase was dried over anhydrous MgSO
was distilled off by rotary evaporation, the residue was purified by
silica gel column chromatography using DCM-PE (v/v, 2:1) as eluent
ꢀ
C
) of 186 C for BDTx-
2
4
. After the solvent
ꢀ
increased T
2
M
1
to give blue solid (410 mg, yield 68.6%). H NMR (400 MHz, CDCl
3
)
ꢀ
ꢀ
ꢀ
2q
d
ppm, 8.96 (d, J ¼ 4.0 Hz, 1H), 8.90 (d, J ¼ 3.4 Hz, 2H), 7.67 (d,
J ¼ 5.6 Hz, 2H), 7.62 (d, J ¼ 4.7 Hz, 2H), 7.53 (d, J ¼ 5.6 Hz, 2H), 7.38
s, 2H), 7.34 (d, J ¼ 4.1 Hz, 2H), 7.23 (s, 4H), 7.14 (d, J ¼ 9.4 Hz, 2H),
.07 (d, J ¼ 3.6 Hz, 2H), 4.03 (d, J ¼ 6.6 Hz, 8H),1.88 (s, 4H),1.37e1.25
m, 32H),, 1.01e0.74 (m, 24H). Elementary Analysis Calculated for
2
(
7
(
C
5
90
H
92Br
2
N
4
O
4
S
10; C, 60.93; H, 5.23; N, 3.16; Found: C, 60.96; H,
þ
3.3. Optical properties
.68; N, 3.18. MALDI-MS (m/z): 1773.27; Found: 1773.59 [M þ H ].
The UV-vis absorption spectra of BDTx-2TVTDPP and BDTy-
2TVTDPP in DCM solution (10 M) and thin film are shown in
ꢂ5
2.4.6. Synthesis of BDTy-2TVTDPP
Tributyl(thiophen-2-yl)stannane (9) (120 mg, 0.25 mmol) and
Fig. 4. It is found that both SMs have similar absorption spectra at
compound 8 (100 mg, 0.56 mmol) were dissolved in toluene
10 mL). Tris(dibenzylideneacetone)dipalladium (Pd (dba) , 2 mg)
the range of 300e700 nm with the maximum absorption peak
(lmax) around 600 nm in DCM solution. Furthermore, both SMs
(
2
3
and tri-o-tolylphosphine (4 mg) were then added and the mixture
was heated to 110 C and stirred for 4 h. After cooled to RT, the
resulting mixture was poured into 50 mL water and extracted with
DCM (50 mL). The collected organic phase was dried over anhy-
display a red-shift absorption spectrum in their thin films instead of
in DCM solution, implying that the intermolecular interaction is
enhanced in their thin films. Compared to BDTy-2TVTDPP, BDTx-
2TVTDPP shows an additional peak at long wavelength of 679 nm,
ꢀ
drous MgSO
4
. After the solvent was distilled off by rotary evapo-
which can be attributed to the extent of
p p interaction. This result
ꢂ
ration, the residue was purified by silica gel column
chromatography using DCM-PE(v/v, 4:1) as eluent to give blue solid
is agreed with the better packing of BDTx-2TVTDPP than BDTy-
2TVTDPP in the neat film. The calculated optical band gaps are
1.61 eV and 1.71 eV for BDTx-2TVTDPP and BDTy-2TVTDPP based
on the film absorptions, respectively (see Table 2).
1
(
85.7 mg, yield 76.5%). H NMR (400 MHz, CDCl
3
)
d
ppm, 9.01 (d,
J ¼ 3.9 Hz, 2H), 8.94 (d, J ¼ 3.2 Hz, 2H), 7.81 (d, J ¼ 5.5 Hz, 2H), 7.66
(
7
2
4
d, J ¼ 4.7 Hz, 2H), 7.58 (d, J ¼ 6.0 Hz, 4H), 7.49 (d, J ¼ 15.7 Hz, 2H),
.36 (d, J ¼ 3.9 Hz, 2H), 7.28 (d, J ¼ 3.5 Hz, 4H), 7.18 (d, J ¼ 15.7 Hz,
3.4. Electrochemical properties
H), 7.12 (d, J ¼ 2.9 Hz, 2H), 7.07 (d, J ¼ 3.3 Hz, 2H), 6.91 (s, 2H),
.20e3.98 (m, 8H), 2.94 (t, J ¼ 7.5 Hz, 4H), 1.94 (d, J ¼ 15.2 Hz, 2H),
Fig. 5 shows the cyclic voltammetry (CV) plots of the BDTx-
1
.87e1.73 (m, 4H), 1.35 (m, 48H), 1.05e0.83 (m, 36H). Elementary
2TVTDPP and BDTy-2TVTDPP based films. The onset oxidation
130 4 4
Analysis Calculated for C114H N O S12; C, 68.29; H, 6.54; N, 2.79;
Found: C, 68.36; H, 6.46; N, 2.75. MALDI-MS (m/z): 2003.68; Found:
and reduction potentials (Eox/Ered) of 0.78/ꢂ1.0 V for BDTx-
þ
2TVTDPP and 0.98/ꢂ1.0 V for BDTy-2TVTDPP are exhibited. As
2
004.073 [M ].
þ
the potential of Fc/Fc is 0.48 V vs Ag/AgCl measured in this work
þ
and the assumed energy level of ferrocene/ferrocenium (Fc/Fc )
37
3
. Results and discussions
is ꢂ4.8 eV below the vacuum level, the HOMO and LUMO energy
levels (EHOMO and ELUMO) of both SMs can be calculated according to
the equation: EHOMO ¼ ꢂ(Eox þ 4.32) eV; ELUMO ¼ ꢂ(Ered þ 4.32) eV.
Table 3 lists the resulting electrochemical data. As a result, the
3
.1. Synthesis of BDTx-2TVTDPP and BDTy-2TVTDPP
Scheme 1 illustrates the synthetic route of BDTx-2TVTDPP and
E
HOMO/ELUMO data of ꢂ5.1/ꢂ3.32 eV for BDTx-2TVTDPP and ꢂ5.3/
BDTy-2TVTDPP. Compounds 2, 3, 4, 7 and 9 were synthesized ac-
ꢂ3.32 eV for BDTy-2TVTDPP are calculated. It is obviously found
3
4e36
cording the reported literature.
the Witting reaction between compounds 3 and 4 in a yield of
9.3%. BDTx-2TVTDPP was prepared by the Still reaction between
Compound 5 was obtained by
Table 1
4
Thermal properties of BDTx-2TVTDPP and BDTy-2TVTDPP.
compounds 5 and 6 in a yield of 51.3%. Compound 4 reacted with
compound 7 to give compound 8. BDTy-2TVTDPP was prepared by
the Still reaction between compounds 8 and 9 in a yield of 76.5%.
Both target SMs were fully characterized by H NMR, MALDI-MS
spectra and elementary analysis.
ꢀ
a
ꢀ
ꢀ
T
c
SMs
T
d
( C)
T
m
( C)
( C)
BDTx-2TVTDPP
BDTy-2TVTDPP
406
429
263
209
186
e
1
a
The temperature at 5% weight-loss under nitrogen atmosphere.
Please cite this article in press as: Duan L, et al., The A-D-A type small molecules with isomeric benzodithiophene cores: Synthesis and influence