Selenophene-Based Heteroacenes: Synthesis, Structures, and Physicochemical Behaviors

Article abstract of DOI:10.1021/acs.joc.8b02107

On the basis of three new building blocks, dithieno[3,2-b:2′,3′-d]selenophene (tt-DTS), diseleno[3,2-b:2′,3′-d]thiophene (tt-DST), and diseleno[3,2-b:2′,3′-d]selenophene (tt-DSS), four thiophene- and selenophene-based heteroacenes (3a-d) with up to seven

Full text of DOI:10.1021/acs.joc.8b02107

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Article
Selenophene-based Heteroacenes: Synthesis,
Structures, and Physicochemical Behaviors
Wan Xu, Mengjie Wang, Zhiying Ma, Zhen Shan, Chunli Li, and Hua Wang
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.8b02107 • Publication Date (Web): 02 Sep 2018
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Selenophene-based Heteroacenes: Synthesis, Structures, and
Physicochemical Behaviors
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Wan Xu, Mengjie Wang, Zhiying Ma, Zhen Shan, Chunli Li,* and Hua Wang*
E-mail: chunli79@126.com; hwang@henu.edu.cn
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Engineering Research Center for Nanomaterials, Henan University, Kaifeng, 475004,
China
Abstract
Based on three new building blocks, dithieno[3,2-b:2′,3′-d]selenophene (tt-DTS),
diseleno[3,2-b:2′,3′-d]thiophene (tt-DST) and diseleno[3,2-b:2′,3′-d]selenophene
(tt-DSS), four thiophene- and selenophene-based heteroacenes (3a-d) up to seven
fused rings were designed and synthesized. Another two selenophene-based
heteroacenes (1 and 2) with three and five fused rings were prepared. The molecular
structures of 1, 2, 3a and 3c were confirmed by single-crystal analysis. The results
showed that molecular structures, spectroscopy features and cyclic voltammetry
behaviors could be modulated by changing the heteroatoms from sulfur to selenium
for 3a-d or changing the numbers of selenophene rings for 1, 2 and 3d.
Introduction
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Heteroacenes based on thiophene have been widely studied in the field of
organic functional materials because of their extended conjugation, rigid planarity and
their significant potential for applications in electronic devices.1 Selenophene, bearing
a heavy element selenium (Se) with a large polarizable radius, possesses
advantageous properties compared with its lighter analog, namely, thiophene;
moreover, with narrow optical band gap, strong intermolecular interactions, and
well-aligned solid-state structure shows excellent charge-transport properties.2,3
In atomic engineering, a promising method, a subtle change in molecular
structure can significantly change the electronic, optical, and physical properties of a
material.4,5 Replacing sulfur with selenium might be a suitable method for fine-tuning
the structure and property of thiophene-based heteroacene. In our recent research
work, the inner helix climbs, turns in-plane, and the UV-vis absorption spectroscopy
feature of benzohetero[7]helicene can be modulated by changing the number of sulfur
and selenium atoms.6 Although different synthesis methods have been established for
thiophene-based heteroacenes,1d,7 the synthesis access to selenophene-based
heteroacenes remains high challenge, because of the generally high reactivity of the
C–Se bond and the weak orbital overlap when selenium atom is involved.4
Selenophene-based heteroacenes reported, usually have been prepared by
intramolecular cyclization of Se to an ethynyl group.8-12 Selenophene-based
heteroacenes containing two or three rings have been synthesized through the
intramolecular cyclization of substituted alkynes and 2,2′-biselenophene,8 and
including four9, five10 fused rings and selenophene as the outmost rings4, 9a, 11 have
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been obtained via the intramolecular cyclization of Se to an ethynyl group.
Yamaguchi et al. have reported the synthesis of thiophene- and selenophene-based
heteroacenes containing seven fused rings through intramolecular triple cyclization of
bis(o-haloaryl)diacetylenes and their single-crystal field-effect transistors properties.12
In the present work, intramolecular cyclization of dicarbanions and oxidative
photocyclization have been applied to prepare thiophene- and selenophene-based
heteroacenes. Three new building blocks, namely, tt-DTS, tt-DST and tt-DSS, and
four kinds of thiophene- and selenophene-based heteroacenes up to seven fused rings,
namely, 3a-d and selenophene-based heteroacenes with three and five fused rings,
namely, 1 and 2 are designed and synthesized. The crystal structures, spectroscopy
features, and cyclic voltammetry behavior of the synthesized thiophene- and
selenophene-based heteroacenes are studied. In addition, the energy levels and
electron cloud distribution of the highest occupied molecular orbitals (HOMO) and
the lowest unoccupied molecular orbitals (LUMO) orbitals are predicted.
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Results and Discussion
Synthesis of (TMS)2-tt-DTS, (TMS)2-tt-DST, (TMS)2-tt-DSS, 1, 2 and 3a-d
The synthetic route to 1 is shown in Scheme 1. 5,5′-bis(trimethylsilanyl)-3,3′-
diselenophene (5) was prepared from selenophene through our previously reported
methods.6b Following the deprotonate at the α positions in 5 with LDA, DMF was
added to produce dialdehyde 6. After intramolecular McMurry reaction of 6 using
TiCl4/Zn/pyridine, a new kind of selenophene-based heteroacene, namely, compound
1 was obtained. The total yield of 1 is 7.5% from selenophene through six step
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reactions.
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Scheme 1. Synthetic route to 1
The synthetic route to 2 is shown in Scheme 2. In the synthesis of 2,
2,5-bis(trimethylsilyl)seleno[3,2-b]selenophene (9) is the key intermediate and
oxidative photocyclization in the final synthetic step is the crucial step. After the
o
highly efficient bromine dance reaction of 4b by using LDA in THF at -78 C, I2 was
added to prepare dihalogenation derivative 7. Compound 8 was obtained in yield of
90% through the Sonogashira coupling reaction of 7 and ethynyltrimethylsilane. After
the intramolecular cyclization in the presence selenium of dicarbanion from the Br/Li
exchange on 8 with t-BuLi, 9 was obtained in 75% yield. Bromo-substituted
derivatives 10 could be generated by treating 9 with NBS in a mixture solvent
(HOAc-CHCl3, v/v = 1/8).6,7c Through the same preparation methods as 6 and 1,
aldehyde 11 and substituted ethylene 12 were synthesized in yields of about 40% and
60%, respectively. After the oxidative photocyclization of 12 in the presence of iodine
in dry toluene through irradiation of 450 W Hg medium pressure lamp for 40 minutes,
5,5'-bis(trimethylsilanyl)benzo[1,2-b:3,4-b']bis(seleno[3,2-b]- selenophene) (2) was
obtained in yields of 35%. The total yield of 2 is about 4.0% from 4b through seven
step reactions.
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Scheme 2. Synthetic route to 2
Scheme 3 shows the synthetic route of three novel thiophene- and selenophene-
based building blocks, namely, tt-DTS, tt-DST and tt-DSS. Compounds 13a and 13b
were prepared according to the literature methods.6b,8d-f The strategy for synthesis of
(TMS)2-tt-DTS, (TMS)2-tt-DST and (TMS)2-tt-DSS is the intramolecular cyclization
of the dicarbanion generated from 13a and 13b in the presence of selenium and
(PhSO2)2S, respectively. After the double Br/Li exchange on 13a and 13b with n-BuLi,
the cyclization with selenium generated [1,2]diseleninecyclohexadienes6b derivatives
(14a, 14b), instead of (TMS)2-tt-DTS and (TMS)2-tt-DSS with yield of 46% and 51%,
respectively. The structure of 14a and 14b were confirmed by NMR and HRMS
analyses. Compounds 14a and 14b were successfully converted into (TMS)2-tt-DTS
o
and (TMS)2-tt-DSS by heating 14a and 14b with Cu nanopowder at 145 C for 30
minutes without any solvent. (TMS)2-tt-DST was obtained with yield of 50% through
cyclization of the dicarbanion from 13b with (PhSO2)2S. The total yields of
(TMS)2-tt-DTS, (TMS)2-tt-DST and (TMS)2-tt-DSS are 3.2%, 3.8% and 3.8%,
starting from 4a, 4b and 4b, respectively.
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Scheme 3. Synthetic route to (TMS)2-tt-DTS, (TMS)2-tt-DST and (TMS)2-tt-DSS
The synthetic route of 3 (3a-d) is shown in Scheme 4. Compounds 3a-d were
synthesized from (TMS)2-tt-DTT,7c (TMS)2-tt-DTS, (TMS)2-tt-DST and
(TMS)2-tt-DSS, respectively, through four steps: bromination, formylation, McMurry
reaction, and photocyclization, and the total yields are 9%, 0.6%, 3%, and 4%,
respectively. The oxidative photocyclization in the presence of iodine in dry toluene
through irradiation of 450 W Hg medium pressure lamp is the crucial step in the
synthesis of 3.
2-Bromo-substituted derivatives 15a-d were prepared with the similar method
for making 10. Starting from (TMS)2-tt-DTT,7c (TMS)2-tt-DTS, (TMS)2-tt-DST, and
(TMS)2-tt-DSS, the yields are 80%, 75%, 80%, and 73%, respectively. Aldehydes
16a-d were obtained according to the similar preparation procedure to 6 and 11, by
quenching of the carbanions of 15a-d from the Li/Br exchange with DMF, the yields
are 60%, 15%, 52%, and 49%, respectively. After the intermolecular McMurry
reactions of 16a-d using TiCl4/Zn/pyridine, compounds 17a-d were synthesized with
yields of 65%, 60%, 41%, and 46%, respectively. After the oxidative photocyclization
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of 17a-d, four kinds of thiophene- and selenophene-based heteroacenes, namely, 3a-d
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were obtained in yields of 30%, 30%, 20%, and 23%, respectively.
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Scheme 4. Synthetic route to 3
Crystallographic Analyses for 9, 1, 2, 3a and 3c
The molecular structures of 9, 1, 2, 3a and 3c were confirmed by single-crystal
analysis (Figure 1). Compound 9 belongs to the monoclinic, space group P121/n1. In 9,
two selenophene rings are almost completely coplanar (Figure 1a and b) and dihedral
angle of two selenophene rings is 0.000(143)°. Compound 1 belongs to the
monoclinic, space group I12/a1. In 1, all the three rings are completely coplanar (Fig.
1c and d) and the torsion angle of C2–C3–C8–C9 is 1.629(785)°. With the formation
of benzene ring from 12, compound 2 was compressed with [5]helicene structure (Fig.
2a and b). Compound 2 belongs to the monoclinic, space group P121/c1. With the
formation of benzene ring from 17a and 17c, 3a and 3c were compressed into
[5]helicene-like structures containing seven fused rings (Figure 1g-j). Compound 3a
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belongs to the orthorhombic, space group P212121, and 3c belongs to the monoclinic,
space group C2/c. Five rings (ring-B to ring-F) in the middle of 3a and 3c form a
[5]helicene-like structure with slight twisting. Compounds 2, 3a and 3c were
compared in terms of the dihedral angle between ring-B and ring-F, the sum of the
three distortion angles derived from Se1, C4, C5, C10, C11, Se4 for 2, S5, C13, C12,
C7, C6, S2 for 3a and S2, C13, C12, C7, C6, S1 for 3c, the inner six atoms of from
ring-B to ring-F helix climbs, and the distance of two terminal heteroatoms (for 3a
and 3c); which increased with the increase of the numbers for selenium atoms (Table
1).
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Table 1. Dihedral anglesa (o), Distortion anglesb (o), Helix climbsc (Å) and Distanced (Å).
Compound
Dihedral angles
5.641(240)
Distortion angles
7.878(1821-1942)
13.276(1114-1185)
15.510(7850-8220)
Helix climbs
0.2490(28-29)
0.4530(16-17)
0.4626(6)
Distance
11.2867(39)
11.4741(12)
---
3a
3c
2
10.583(169)
11.711(131)
a dihedral angle between ring-B and ring-F; b defined by the sum of the three distortion angles
derived from Se1, C4, C5, C10, C11, Se4 for 2, S5, C13, C12, C7, C6, S2 for 3a and S2, C13,
C12, C7, C6, S1 for 3c; c the inner six atoms of from ring-B to ring-F helix climbs; ddefined by the
distance of two terminal heteroatoms (for 3a and 3c).
Compounds 3a and 3c possess a slightly distorted molecular geometry, leading to
a herringbone arrangement in their crystals (Figure S94, 95). In the crystal packings
of 3a and 3c, each 3a molecule interacts with seven adjacent molecules through
intermolecular interactions (S6-H21B (2.99 Å), S2-H23B (2.87 Å), C5-S3 (3.43 Å)
and C4-S3 (3.46 Å), Figure S94), and each 3c molecule interacts with six adjacent
molecules through intermolecular interactions (S1-H22B (2.98 Å), Se1-H21B (3.04
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Å), Se1-H21A (3.05 Å), C14-Se3 (3.43 Å), C15-Se3 (3.45 Å) and C10-Se4 (3.52 Å),
Figure S95). Such multiple interactions are normally considered to be beneficial for
their applications in organic electronic devices.2
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(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
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(i)
(j)
Figure 1. The crystal structures (ball and stick) for 9, 1, 2, 3a and 3c. (a) Top view for 9; (b) side
view for 9; (c) Top view for 1; (d) side view for 1; (e) Top view for 2; (f) side view for 2; (g) Top
view for 3a; (h) side view for 3a; (i) top view for 3c; (j) side view for 3c. All hydrogen atoms are
omitted for clarity.
Spectroscopy features and Electrochemical Properties
Figure 2. UV-vis absorption spectra of 1, 2 and 3a-d in CH2Cl2 ([C] = 1×10-5 M).
Spectroscopy features and cyclic voltammetry behaviors of 1, 2 and 3a-d were
studied. The UV-vis absorption spectra of 3a-d are generally similar in shape and
exhibit two major absorption bands within 250–355 nm (Band-I) and 335–440 nm
(Band-II) (Figure 2). The effect of gradually changing the heteroatoms from sulfur to
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selenium is evident in the UV-vis absorption profiles. The progressive red-shifts in
absorption spectra were found with the increasing of selenium atoms, with λmax values
peaked at 365 to 373 to 379 to 387 nm from 3a to 3d, respectively. Compounds 1, 2
and 3d exhibit the maximum absorption peaks significantly red-shifted from 313 to
355 and 387 nm, respectively, with increasing of the number of selenophene (Figure
2). As a result, the optical band-gaps estimated from the absorption edges gradually
narrowed down from 1 to 3d (Table S3). Six sulfur atoms were replaced gradually by
selenium atoms from 3a to 3d, the fluorescence intensity (Figure S85, 86),
fluorescence quantum yield (ΦF, Figure S87, Table S1), and fluorescence lifetime
rapidly decreased (Table S3). The decrease could be due to the fast intersystem
crossing from the excited singlet state to the triplet state based on the stronger
spin-orbit coupling arising from the heavy atom effect.13 In 2-methyl tetrahydrofuran
at 77 K, the fluorescence emission intensities of 3a-d increased compared with the
cases at room temperature, resulting in their fine structures. This phenomenon could
be due to the disappearance of non-radiative deactivation processes from molecular
vibrations and single bond rotation at 77 K (Figure S85).14
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The cyclic voltammetry (CV) results of 1 and 2 show irreversible oxidation
o
o
waves at E1 = +1.55 V for 1 and E1 = +1.37 V for 2. Compounds 3a-d show two
o
o
o
o
reversible waves at E1 = +1.31 V and E2 = +1.68 V for 3a, E1 = +1.27 V and E2 =
o
o
o
o
+1.60 V for 3b, E1 = +1.25 V and E2 = +1.57 V for 3c, and E1 = +1.22 V and E2 =
+1.53 V for 3d (vs Fc/Fc+, Figure S88). For compounds 1, 2 and 3a-d, the HOMO
levels gradually increased, the LUMO levels gradually decreased, and the optical
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band gaps gradually narrowed down (Table S3). The influence of the replacement of
sulfur with selenium of heteroacenes with seven fused rings (3a-d) is smaller than the
change of the number for selenophene rings (1, 2 and 3d). However, quantum
chemistry calculation was then conducted using Gaussian 09S1 to predict the energy
levels (Table S3) and electron cloud distribution of the HOMO and LUMO orbitals
for the six compounds. As presented in Figure 3, 1, 2, 3a-d possess very similar
HOMO and LUMO distributions, and their HOMO and LUMO orbitals are
distributed over the aromatic cores. The calculated HOMO and LUMO levels are
consistent with the experimental values (Table S3).
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Figure 3. Visualized of HOMO and LUMO distributions (b3lyp/6-31g*) for 1, 2, 3a-d.
In summary, three new building blocks, namely, tt-DSS, tt-DST and tt-DTS,
were developed, which can be used not only to build thiophene- and
selenophene-based heteroacenes but also to prepare new types of organic functional
materials based on selenophene.1e,15 On the one hand, four kinds of thiophene- and
selenophene-based heteroacenes, namely, 3a-d were successfully prepared using these
building blocks. On the other hand, selenophene-based heteroacenes with three, five
and seven fused rings, namely, 1, 2 and 3d were also synthesized from selenophene.
Their crystal packings exhibit multiple short contacts, such as S···H, S···C, Se···H,
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and Se···C interactions, which may benefit the OFET properties.1e,2 The UV-vis
absorption peaks gradually red-shifted and the optical band-gaps gradually narrowed
down with increasing the number of fused aromatic rings or replacing individual
atoms from S to Se. This study provides a strategy for fine-tuning the molecular
structure and its physicochemical behavior by replacing individual atoms or changing
the numbers of aromatic ring of heteroacenes. This work definitely exhibits the
intrinsic nature of fused heteroacenes and benefits both thiophene chemistry and
selenophene chemistry.
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Experimental Section
General Procedures and Materials Ether and tetrahydrofuran (THF) for use on
vacuum line were freshly distilled from sodium/benzophenone prior to use. t-BuLi
(pentane) and n-BuLi (hexane) were obtained from Energy Chemical, prior to use,
their concentrations were determined by titration with N-pivaloyl-o-toluidine.16
Column chromatography was carried out on silica gel (300-400 mesh). Analytical
thin-layer chromatography was performed on glass plates of Silica Gel GF-254 with
detection by UV. Standard techniques for synthesis under inert atmosphere, using
gasbag and Schlenk glassware equipped with an 8-mm PTFE vacuum stop-cock were
employed. 4a,6,8e-f 4b,6 building block of (TMS)2-tt-DTT and 15a7c were prepared
according to the literature methods. All starting materials and reagents were
commercially available.
1H NMR and 13C{1H}NMR spectra were recorded on 300 or 400 MHz NMR
instrument using CDCl3 as solvents. IR spectra were obtained using an FT-IR
instrument. HRMS analysis was carried out on a mass spectrometer equipped with
DART-Positive, MALDI_DHB and MALDI-FT_DHB. Melting point determination
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was taken on a Melt-Temp apparatus and was uncorrected. The X-ray crystallographic
analyses were performed using crystals of compounds 9, 1, 2, 3a and 3c with sizes of
0.39 × 0.25 × 0.22, 0.45 × 0.08 × 0.06, 0.30 × 0.19 × 0.14, 0.13 × 0.1 × 0.03 and 0.1 × 0.05 ×
0.03 mm3, respectively. The intensity data were collected with the
ω
scan mode (296
λ = 1.54184 Å).
9
10
11
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K) on a diffractometer with CCD detector using Cu K radiation (
α
The data were corrected for Lorentz and polarization effects, and absorption
corrections were performed using SADABS program.17 The crystal structures were
solved using the SHELXTL program and refined using full-matrix least-squares.18
Further details are in the deposited CIF files. Slow evaporation of solutions of 9, 1, 2,
3a and 3c in CHCl3-CH3OH (3:2 for 9, 1, 2 and 3a, 3:1, v/v) were employed for
growing single crystals. The fluorescence quantum yields (ΦF) of 3a-d are
characterized in dichloromethane with quinine sulfate in 0.1 N H2SO4 as the control.
Synthesis of 5,5′-bis(trimethylsilanyl)-3,3′-biselenophene-2,2′-dicarbaldehyde (6)
n-BuLi (2.30 mL, 2.49 M in hexane, 5.71 mmol, 2.20 equiv) was added dropwise
to diisopropylamine (0.81 mL, 5.71 mmol, 2.20 equiv) in dry ethyl ether (10 mL) at 0
o
oC. After 0.5 h at 0 C, the prepared LDA solution was transferred by syringe into a
solution of 5 (1.05 g, 2.60 mmol) in dry ethyl ether (40 mL) at -78 oC. After 2 h at -78
o
oC, DMF (0.60 mL, 7.60 mmol, 3.00 equiv) was added at -78 C and kept 1 h, then
the reaction mixture warmed up slowly to ambient temperature overnight. The
reaction mixture was quenched with H2O, extracted with CH2Cl2 (3 × 15 mL). The
organic layer was washed with saturated NaCl (20 mL) and water (2 × 20 mL), and
then dried over MgSO4. The residue was purified by column chromatography on
o
silica gel with petrol ether (60-90 C) HEX/CH2Cl2 (v/v = 2/1) as eluent to yield 6
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(0.42 g, 35%) as a brown solid, mp: 165-166 oC. 1H NMR (CDCl3, 300 MHz):
δ
(ppm)
5
6
7
9.59 (s, 2H), 7.64 (s, 2H), 0.38 (s, 18H). 13C{1H}NMR (CDCl3, 75 MHz):
δ
183.6,
8
9
160.8, 150.9, 146.3, 140.0, -0.1. MS (DART-Positive Ion Mode): m/z ) 461.0(83)
[M+]. HRMS (DART-FTICR) m/z: [M + H]+ Calcd for C16H22O2Se2Si2 462.9562;
Found 462.9559. IR (KBr): 3060, 2950, 1650, 1251, 954, 843 cm-1.
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Synthesis of 2,7
′-bis(trimethylsilanyl)benzo[1,2-b:4,3-b′]bis(selenophene) (1)
TiCl4 (0.22 mL, 1.96 mmol, 5.00 equiv) was carefully added into dry THF (20
o
o
mL) at 0 C. After keeping at 0 C for 20 min, zinc dust (0.26 g, 3.92 mmol, 10.00
o
equiv) was added, and then the mixture was refluxed at 100 C for 2 h. After that,
pyridine (0.16 mL, 1.96 mmol, 5.00 equiv) was added and the mixture was refluxed
for another 1 h. After cooling to ambient temperature, a solution of 6 (0.18 g, 0.39
mmol) in dry THF (10 mL) was added and the reaction mixture was refluxed at 100
o
oC for 18 h. The reaction was quenched with water at 0 C, then extracted with
CH2Cl2 (3 × 30 mL) and washed with saturated NaCl (25 mL) and H2O (2 × 25 mL),
and then dried over MgSO4. After removing the solvent in vacuum, the residue was
washed with Et2O (3 × 5 mL) to yield 1 (0.05 g, 30%) as a yellow solid, mp: 152-154
1
oC. H NMR (CDCl3, 400 MHz):
δ
(ppm) 8.18 (s, 2H), 7.81 (s, 2H), 0.41 (s, 18H).
148.0, 141.9, 140.1, 132.4, 121.4, 0.2. MS
13C{1H}NMR (CDCl3, 100 MHz):
δ
(DART-Positive Ion Mode): m/z ) 430.0(100) [M+ + 1]. HRMS (DART-FTICR) m/z:
[M]+ Calcd for C16H22Se2Si2 429.9590; Found 429.9586. IR (KBr): 3061, 2950, 1390,
1251, 954, 843 cm-1.
Synthesis of 4-bromo-5-iodo-2-(trimethylsilanyl)selenophene (7)
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9
n-BuLi (10.10 mL, 2.50 M in hexane, 25.34 mmol, 1.30 equiv) was added
dropwise to diisopropylamine (4.10 mL, 29.24 mmol, 1.50 equiv) in THF (20 mL) at
0 oC. After 0.5 h at 0 oC, the prepared LDA solution was transferred by syringe into a
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o
o
solution of 4b (5.50 g, 19.50 mmol) in THF (50 mL) at -78 C. After 6 h at -78 C,
iodine (7.42 g, 29.24 mmol, 1.50 equiv) was added to quench the reaction. The
reaction mixture was extracted with CH2Cl2 (3 × 15 mL) and washed with saturated
Na2S2O3 (20 mL) and H2O (2 × 20 mL), and then dried over MgSO4. After the
removal of the solvent under vacuum, the residue was purified by column
o
chromatography on silica gel with petrol ether (60-90 C) as eluent to yield 7 (7.56 g,
95%) as a orange liquid. 1H NMR (CDCl3, 300 MHz):
δ (ppm) 7.24 (s, 1H), 0.29 (s,
9H). 13C{1H}NMR (CDCl3, 75 MHz):
δ
155.9, 138.7, 123.1, 81.4, -0.1. MS
(MALDI-FT_DHB): m/z 407.8(30) [M+]. HRMS (MALDI-FT_DHB-FTICR) m/z:
[M]+ Calcd for C7H10BrISeSi 407.7945; Found 407.7936. IR (KBr): 3042, 2958, 2857,
963, 1251, 843 cm-1.
Synthesis of 4-bromo-5-(trimethylsilyl)ethynyl-2-(trimethylsilanyl)selenophene (8)
To a degassed THF (10 mL) solution of compound 7 (3.60 g, 8.82 mmol)
ethynyltrimethylsilane (1.20 mL, 9.26 mmol, 1.05 equiv), PdCl
2
(PPh
3
) (1.72 g, 2.45
2
mmol, 0.03 equiv), CuI (0.47 g, 2.45 mmol, 0.03 equiv) and PPh3 (0.07 g, 2.45 mmol,
o
0.03 equiv) were added. The resulting mixture was stirred for 10 h at 40 C, diluted
with water (50 mL), extracted with CH2Cl2 (3×20 mL), dried over MgSO . After the
4
removal of the solvent under vacuum, The residue was purified by column
o
chromatography on silica gel with petrol ether (60-90 C) as eluent to yield 8 (3.00 g,
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90%) as a pale yellow liquid. 1H NMR (CDCl3, 300 MHz)
δ
(ppm) 7.32 (s, 1H), 0.29
5
6
7
13
(s, 9H)，
0.26 (s, 9H). C{1H}NMR (CDCl3, 75 MHz):
δ
151.4, 138.4, 127.4, 118.1,
8
9
106.2, 97.8, -0.1, -0.2. MS (MALDI-FT_DHB): m/z ) 378.9(50) [M+]. HRMS
(MALDI-FT_DHB-FTICR) m/z: [M + H]+ Calcd for C12H19BrSeSi2 378.9447; Found
378.9449. IR (KBr): 3051, 2959, 2893, 1260, 954, 843 cm-1.
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Synthesis of 2,5-bis(trimethylsilyl)seleno[3,2-b]selenophene (9)
t-BuLi (22.00 mL, 1.18 M in n-pentane, 25.90 mmol, 2.05 equiv) was added
dropwise into a solution of 8 (4.78 g, 12.63 mmol) in Et2O (100 mL) at -78 °C, then
the reaction mixture was kept for 2 h. Dry Se (metals basis) (2.00 g, 25.30 mmol, 2.00
equiv) was added at -78 °C, the reaction mixture was kept at -78 °C for 1 h, then
warmed up slowly to ambient temperature overnight. The reaction mixture was
quenched with methanol at -78 °C, extracted with CH2Cl2 (3 × 25 mL) and then
washed with water (3× 30 mL). After drying over MgSO4, the solvent was removed
under vacuum. The residue was purified by column chromatography on silica gel with
petrol ether (60-90 °C) as eluent to yield 9 (3.59 g, 75%) as a pale yellow solid, mp:
o
1
127-128 C. H NMR (CDCl3, 300 MHz)
δ (ppm) 7.66 (s, 2H), 0.34 (s, 18H).
13C{1H}NMR (CDCl3, 75 MHz):
δ
150.3, 147.0, 131.0, 0.1. MS (MALDI-FT_DHB):
m/z ) 379.9(100) [M+]. HRMS (MALDI-FT_DHB-FTICR) m/z: [M]+ Calcd for
C12H20Se2Si2 379.9434; Found 379.9426. IR (KBr): 3042, 2958, 2883, 963, 843 cm-1.
Synthesis of 5-bromo-2-(trimethylsilanyl)seleno[3,2- ]selenophene (10)
b
The compound of 9 (0.80 g, 2.11 mmol) was dissolved in CHCl3 (20 mL), NBS
(0.45 g, 2.54 mmol, 1.20 equiv) was dissolved in 16 mL HOAc-CHCl3 (v/v = 1/8) and
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added dropwise under good stirring at 0 oC. After stirring for 2 h, the reaction mixture
was quenched with H2O and extracted with CH2Cl2 (3 × 10 mL), then washed with
saturated NaHCO3 (20 mL) and water (2 × 20 mL). The organic layer was dried over
anhydrous MgSO4. After the solvent was removed under vacuum, the residue was
washed with 3 × 5 mL hexane to yield 10. However, we could not obtained the pure
10 from the reaction mixture due to the too similar polarities from 9, 10 and
2,5-dibromoselenopheno[3,2-b]selenophene in the mixture. 1H NMR of crude product
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of 10, 1H NMR (CDCl3, 300 MHz)
δ
(ppm) 7.56 (s, 1H), 7.51 (s, 1H), 0.34 (s, 9H).
]selenophene-2-carbaldehyde (11)
Synthesis of 5-(trimethylsilanyl)seleno[3,2-
b
n-BuLi (0.91 mL, 2.40 M in hexane, 2.18 mmol, 1.05 equiv) was added dropwise
o
to 10 (0.80 g, 2.08 mmol) in THF (40 mL) at -78 oC. After 2 h at -78 C, DMF (0.32
o
mL, 4.15 mmoL, 2.00 equiv) was added at -78 C and kept 0.5 h, then the reaction
mixture warmed up slowly to ambient temperature overnight. The reaction mixture
was quenched with H2O, extracted with CH2Cl2 (3 × 15 mL). The organic layer was
washed with saturated NaHCO3 (20 mL) and water (2 × 20 mL), and then dried over
MgSO4. The residue was purified by column chromatography on silica gel with petrol
o
ether (60-90 C) HEX/CH2Cl2 (v/v = 2/1) as eluent to yield 11 (0.28 g, 40%) as a
brown solid, mp: 59-60 oC. 1H NMR (CDCl3, 400 MHz)
δ
(ppm) 9.87 (s, 1H), 8.19 (s,
184.7, 158.2,
1H), 7.74 (s, 1H), 0.38 (s, 9H). 13C{1H}NMR (CDCl3, 100 MHz):
δ
149.3, 148.8, 144.0, 134.9, 131.5, -0.1. MS (MALDI-FT_DHB): m/z 336.9(100)
[M+ + 1]. HRMS (MALDI-FT_DHB-FTICR) m/z: [M + H]+ Calcd for C10H12OSe2Si
336.9061; Found 336.9056. IR (KBr): 3061, 2959, 1668, 954, 833 cm-1.
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Synthesis of 1,2-bis(5-(trimethylsilanyl)seleno[3,2- ]selenophene-2-yl)ethene (12)
b
4
5
6
7
TiCl4 (0.43 mL, 3.89 mmol, 5.00 equiv) was carefully added into dry THF (30
8
9
o
o
mL) at 0 C. After keeping at 0 C for 20 min, zinc dust (0.51 g, 7.78 mmol, 10.00
10
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o
equiv) was added, and then the mixture was refluxed at 100 C for 2 h. After that,
pyridine (0.31 mL, 3.89 mmol, 5.00 equiv) was added and the mixture was refluxed
for another 1 h. After cooling to ambient temperature, a solution of 11 (0.26 g, 0.78
mmol) in dry THF (15 mL) was added and the reaction mixture was refluxed at 100
oC for 18 h. The reaction was quenched with water at 0 C, then extracted with
o
CH2Cl2 (3 × 30 mL) and washed with saturated NaHCO3 (25 mL) and H2O (2 × 25
mL), and then dried over MgSO4. After removing the solvent in vacuum, the residue
was washed with Et2O (3 × 5 mL) to yield 12 (0.15 g, 60%) as a yellow solid (a
o
1
mixture of cis and trans isomers), mp: 239-240 C. H NMR (CDCl3, 400 MHz)
δ
(ppm) 7.60 (s), 7.56 (s), 7.52 (s), 7.38 (s), 6.99 (s), 6.71 (s), 0.35 (s), 0.34 (s). The
ratio of integral areas of the peaks at 6.99 and 6.71 ppm is 1.02:1.24. 13C{1H}NMR
(C2D2Cl4, 353K, 100 MHz):
δ 150.8, 148.5, 145.1, 140.2, 131.1, 125.2, 124.3, 0.0.
MS (MALDI-FT_DHB): m/z ) 640.8(80) [M+ + 1]. HRMS (MALDI-FT_DHB-FTICR)
m/z: [M + H]+ Calcd for C20H24se4Si2 640.8150; Found 640.8145. IR (KBr): 3061,
2959, 1668, 954, 833 cm-1.
Synthesis of 4,4'-bis(trimethylsilanyl)benzo[1,2-b:3,4-b']bis(seleno[3,2-b] selenophene)6 (2)
To a solution of 12 (0.02 g, 0.03 mmol) in dry toluene (25 mL) and iodine (0.02
g, 0.09 mmol, 3.00 equiv) were added. The reaction solution was irradiated with a 450
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W unfiltered Hg medium pressure lamp for 40 minutes. The reaction was quenched
with saturated Na2S3O3 (10 mL). The reaction mixture was extracted with CH2Cl2 (3
× 10 mL) and washed with H2O (3 × 10 mL), and then dried over MgSO4. After
removing the solvent in vacuum, the crude product was purified by PTLC with petrol
10
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60
o
ether (60-90 C) HEX/CH2Cl2 (v/v = 3:1) as developer to yield 2 (0.007 g, 35%) as a
o
1
light red solid, mp: 276-277 C. H NMR (CDCl3, 400 MHz):
δ
δ
(ppm) 7.82 (s, 2H),
150.9, 141.5, 140.5,
7.81 (s, 2H), 0.46 (s, 18H). 13C{1H}NMR (CDCl3, 100 MHz):
139.4, 133.0, 131.3, 123.2, 0.3. MS (MALDI-FT_DHB): m/z ) 638.8(80) [M+ + 1].
HRMS (MALDI-FT_DHB-FTICR) m/z: [M]+ Calcd for C20H22Se4Si2 637.7921;
Found 637.7910. IR (KBr): 3042, 2950, 1474, 963, 843 cm-1
.
Synthesis of 3,3′-dibromo-5,5′-bis(trimethylsilanyl)-2,2′-dithienophene (13a)
n-BuLi (21.00 mL, 2.50 M in hexane, 52.90 mmol, 1.50 equiv) was added
dropwise to diisopropylamine (7.50 mL, 52.90 mmol, 1.50 equiv) in THF (20 mL) at
0 oC. After 0.5 h at 0 oC, the prepared LDA solution was transferred by syringe into a
solution of 4a (8.30 g, 35.30 mmol) in THF (200 mL) at -78 oC. After keeping at -78
oC for 6 h, dry CuCl2 (7.12 g, 52.90 mmol, 1.50 equiv) was added. The reaction
mixture was kept at -78 oC for 2 h, -55 oC for 2 h, then warmed up slowly to ambient
o
temperature overnight. The reaction mixture was quenched with methanol at -78 C,
extracted with CH2Cl2 (3 × 35 mL) and then washed with saturated NaCl (40 mL) and
H2O (2 × 40 mL), and then dried over MgSO4. After the removal of the solvent under
vacuum, the residue was purified by column chromatography on silica gel with petrol
ether (60-90 oC) as eluent to yield 13a (5.79 g, 70%) as a light yellow solid. 1H NMR
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(CDCl3, 400 MHz):
δ
(ppm) 7.46 (s, 2H), 0.33 (s, 18H) (this data is agreement with
5
6
7
8
the analyses reported in the literature).8e
Synthesis of 3,3 -dibromo-5,5 -di(trimethylsilanyl)-2,2′-diselenophene (13b) was
′
′
9
10
11
12
13
14
15
16
17
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synthesized according to the compound 13a procedure. 13b: light yellow solid in
1
yield of 75% (0.90 g). H NMR (CDCl3, 400 MHz):
δ (ppm) 7.46 (s, 2H), 0.33 (s,
18H) (this data is agreement with the analyses reported in the literature).8e
Synthesis of 2,7-bis(trimethylsilanyl)-dithieno[3,2-c:2′,3′-e][1,2]diseleninecyclohexadienes
(14a)
n-BuLi (5.40 mL, 2.50 M in hexane, 13.45 mmol, 2.10 equiv) was added
dropwise into a solution of 13a (3.00 g, 2.13 mmol) in Et2O (100 mL) at -78 oC, then
the reaction mixture was kept for 2 h. Dry Se (metals basis) (2.53 g, 32.00 mmol, 5.00
equiv) was added at -78 oC, the reaction mixture was kept at -78 oC for 2 h, -55 oC for
2 h, then warmed up slowly to ambient temperature overnight. The reaction mixture
o
was quenched with methanol at -78 C, extracted with CH2Cl2 (3 × 25 mL) and then
washed with water (3× 30 mL). After drying over MgSO4, the solvent was removed
under vacuum. The residue was purified by column chromatography on silica gel with
o
petrol ether (60-90 C) as eluent to yield 14a (1.67 g, 56%) as a red solid, mp:
o
1
148-149 C. H NMR (CDCl3, 300 MHz):
δ (ppm) 7.12 (s, 2H), 0.33 (s, 18H).
13C{1H}NMR (CDCl3, 75 MHz):
δ
140.9, 140.2, 134.8, 117.9, -0.3. MS
(DART-Positive): m/z ) 467.8 (100) [M+]. HRMS (MALDI-TOF) m/z: [M]+ Calcd for
C14H20Se2S2Si2 467.8875; Found 467.8875. IR (KBr): 3051, 2958, 2884, 1669, 1251,
991, 852 cm-1.
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2,7-Bis(trimethylsilanyl)-diseleno[3,2-c:2
(14b) was synthesized according to the compound 14a procedure. 14b: red solid in
yield of 51% (0.77 g), mp: 138-139 oC. 1H NMR (CDCl3, 400 MHz):
(ppm) 7.43 (s,
2H), 0.32 (s, 18H). 13C{1H}NMR (CDCl3, 100 MHz):
149.1, 146.3, 137.6, 118.0,
′,3′-e][1,2]diseleninecyclohexadienes
δ
10
11
12
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14
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δ
0.0. MS (MALDI-FT_DHB): m/z 561.78(100) [M+]. HRMS (MALDI-FT_DHB-
FTICR) m/z: [M + H]+ Calcd for C14H21Se4Si2 564.7837; Found 564.7835. IR (KBr):
3033, 2963, 1275, 983, 830 cm-1.
Synthesis of 2,6-bis(trimethylsilanyl)selenopheno[3,2-b:4,5-b']dithiophene ((TMS)2-tt-DTS)
The compound 14a (1.30 g, 2.79 mmol) and Cu nanopowder(0.89 g, 13.93 mmol,
o
5.00 equiv) were heated to 145 C without use of any solvent for 0.5 h. The residue
o
was purified by column chromatography on silica gel with petrol ether (60-90 C) as
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1
eluent to yield (TMS)2-tt-DTS (0.89 g, 82%) as a yellow solid. Mp: 118-119 C. H
NMR (CDCl3, 300 MHz):
(ppm) 7.39 (s, 2H), 0.36 (s, 18H). 13C{1H}NMR (CDCl3,
75 MHz): 141.8, 141.2, 136.8, 129.7, -0.1. MS (DART-Positive): m/z ) 388.0 (100)
δ
δ
[M+ + 1]. HRMS (MALDI-TOF) m/z: [M]+ Calcd for C14H20SeS2Si2 387.9710; Found
387.9720. IR (KBr): 3061, 2958, 2902, 1640, 1251, 991, 843 cm-1.
2,6-Bis(trimethylsilanyl)-diseleno[3,2-b:2
′,3'-d]selenophene
((TMS)2-tt-DSS)
was synthesized according to the compound (TMS)2-tt-DTS procedure.
o
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(TMS)2-tt-DSS: yellow solid in yield of 100% (0.43 g), mp: 132-133 C. H NMR
(ppm) 7.66 (s, 2H), 0.36 (s, 18H). 13C{1H}NMR (CDCl3, 100
(CDCl3, 400 MHz):
δ
MHz):
δ 149.1, 142.8, 139.8, 132.0, 0.2. MS (MALDI-FT_DHB): m/z )
466.71(96)[M+-15]. 481.86 (100) [M+]. HRMS (MALDI-FT_DHB-FTICR) m/z: [M +
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H]+ Calcd for C14H21Se3Si2 484.8672; Found 484.8668. IR (KBr): 3036, 2963, 1260,
937, 845 cm-1.
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Synthesis of 2,6-bis(trimethylsilanyl)-diselenopheno[3,2-b:2′,3'-d]thiophene ((TMS)2-tt-DST)
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n-BuLi (0.70 mL, 2.4 M in hexane, 1.68 mmol, 2.10 equiv) was added dropwise
into a solution of 13b (0.45 g, 0.80 mmol) in Et2O (30 mL) at -78 oC, then the reaction
mixture was kept for 2 h. (PhSO2)2S (0.26 g, 0.82 mmol, 1.02 equiv) was added at -78
o
o
oC, the reaction mixture was kept at -78 C for 2 h, -55 C for 2 h, then warmed up
slowly to ambient temperature overnight. The reaction mixture was quenched with
o
methanol at -78 C, extracted with CH2Cl2 (3 × 15 mL) and then washed with water
(3× 15 mL). After drying over MgSO4, the solvent was removed under vacuum. The
residue was purified by column chromatography on silica gel with petrol ether (60-90
oC) as eluent to yield (TMS)2-tt-DST (0.17 g, 49%) as a light red solid. Mp: 108-109
1
oC. H NMR (CDCl3, 400 MHz):
δ
(ppm) 7.63 (s, 2H), 0.36 (s, 18H). 13C{1H}NMR
(100 MHz, CDCl3):
δ 149.3, 145.1, 138.1, 129.2, 0.1. MS (DART- Positive): m/z)
435.92(100) [M+]. HRMS (DART-FTICR) m/z: [M + H]+ Calcd for C14H21SSe2Si2
436.9228; Found 436.9229. IR (KBr): 3040, 2947, 1275, 983, 845 cm-1.
Synthesis of 6-bromo-2-(trimethylsilanyl)dithieno[3,2-b:2′,3′-d]thiophene (15a)
(TMS)2-tt-DTT (0.44 g, 1.29 mmol) was dissolved in CHCl3 (20 mL), NBS
(0.24 g, 1.36 mmol, 1.05 equiv) was dissolved in 16 mL HOAc-CHCl3 (v/v = 1/8) and
added dropwise under good stirring at 0 oC. After stirring for 2 h, the reaction mixture
was quenched with H2O and extracted with CH2Cl2 (3 × 10 mL), then washed with
saturated NaHCO3 (20 mL) and water (2 × 20 mL). The organic layer was dried over
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anhydrous MgSO4. After the solvent was removed under vacuum, the residue was
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washed with 3 × 5 mL hexane to yield 15a (0.36 g, 80%) as a yellow solid. 1H NMR
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9
(CDCl3, 400 MHz):
δ (ppm) 7.35 (s, 1H), 7.27 (s, 1H), 0.37(s, 9H) (this data is
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agreement with the analyses reported in the literature).7c
6-Bromo-2-(trimethylsilanyl)selenopheno[3,2-b:4,5-b']dithiophen (15b) was
synthesized according to the compound 15a procedure. 15b: yellow solid in yield of
o
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75% (0.61 g), mp: 171-172 C. H NMR (CDCl3, 300 MHz):
δ
(ppm) 7.39 (s, 1H),
142.2, 140.3, 137.8,
7.29 (s, 1H), 0.36 (s, 9H). 13C{1H}NMR (CDCl3, 75 MHz):
δ
136.8, 132.6, 129.3, 126.2, 111.5, -0.2. MS (DART-Positive): m/z ) 393.9 (100) [M+].
HRMS (MALDI-TOF) m/z: [M]+ Calcd for C11H11BrS2SeSi 393.8420; Found
393.8426. IR (KBr): 3098, 2958, 1632, 1251, 991, 843 cm-1.
6-Bromo-2-(trimethylsilanyl)diselenopheno[3,2-b:2
synthesized according to the compound 15a procedure. 15c: yellow solid in yield of
80% (0.27 g), mp: 97-98 oC. 1H NMR (CDCl3, 300 MHz):
(ppm) 7.63 (s, 1H), 7.49
(s, 1H), 0.36 (s, 9H). 13C{1H}NMR (CDCl3, 75 MHz):
149.5, 143.8, 140.8, 137.8,
′,3′-d]thiophene (15c) was
δ
δ
129.2, 128.8, 126.2, 113.7, 0.1. MS (MALDI-FT_DHB): m/z ) 442.8 (22) [M+ + 1].
HRMS (MALDI-FT_DHB-FTICR) m/z: [M + H]+ Calcd for C11H12BrSSe2Si
442.7938; Found 442.7934. IR (KBr): 3073, 2948, 1266, 995, 854 cm-1.
6-Bromo-2-(trimethylsilanyl)diselenopheno[3,2-b:2
synthesized according to the compound 15a procedure. 15d: yellow solid in yield of
73% (0.08 g), mp: 81-89 oC. 1H NMR (CDCl3, 400 MHz):
(ppm) 7.66 (s, 1H), 7 .50
149.3, 142.0, 139.4, 138.9,
′,3′-d]selenophene (15d) was
δ
(s, 1H), 0.36 (s, 9H). 13C{1H}NMR (CDCl3, 100 MHz):
δ
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136.7, 131.5, 129.0, 113.6, 0.1. MS (MALDI-FT_DHB): m/z ) 488.7 (32) [M+ + 1].
HRMS (MALDI-FT_DHB-FTICR) m/z: [M + H]+ Calcd for C11H12BrSe3Si 490.7382;
Found 490.7379. IR (KBr): 3040, 2960, 1253, 960, 854 cm-1.
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Synthesis of 6-trimethylsilanyl-dithieno[3,2-b:2′,3'-d]thiophene-2-carbaldehyde
(16a)
n-BuLi (0.84 mL, 2.40 M in hexane, 2.03 mmol, 1.05 equiv) was added dropwise
to 15a (0.67 g, 1.93 mmol) in THF (30 mL) at -78 oC. After 2 h at -78 oC, DMF (0.30
o
mL, 3.86 mmoL, 2.00 equiv) was added at -78 C and kept 0.5 h, then the reaction
mixture warmed up slowly to ambient temperature overnight. The reaction mixture
was quenched with H2O, extracted with CH2Cl2 (3 × 15 mL). The organic layer was
washed with saturated NaHCO3 (20 mL) and water (2 × 20 mL), and then dried over
MgSO4. The residue was purified by column chromatography on silica gel with petrol
o
ether (60-90 C) HEX/CH2Cl2 (v/v = 2/1) as eluent to yield 16a (0.34 g, 60%) as a
o
1
brown solid. Mp: 146-147 C. H NMR (CDCl3, 400 MHz):
δ
(ppm) 9.95 (s, 1H),
182.8,
7.95 (s, 1H), 7.41 (s, 1H), 0.39 (s, 9H). 13C{1H}NMR (CDCl3, 100 MHz):
δ
147.8, 147.5, 143.6, 141.8, 137.5, 135.4, 130.5, 126.7, -0.3. MS (DART-Positive):
m/z ) 297.0 (100) [M+ + 1]. HRMS (DART-FTICR) m/z: [M + H]+ Calcd for
C12H13OS3Si 296.9893; Found 296.9890. IR (KBr): 3072, 2958, 2819, 1650, 1232,
982, 842 cm-1.
6-Trimethylsilanyl-selenopheno[3,2-b:4,5-b']dithiophene-2-carbaldehyde (16b)
was synthesized according to the compound 16a procedure. 16b: brown solid in yield
o
of 15% (0.08 g), mp: 149-151 C. 1H NMR (CDCl3, 300 MHz):
δ (ppm) 9.96 (s, 1H),
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7.98 (s, 1H), 7.45 (s, 1H), 0.39 (s, 9H). 13C{1H}NMR (CDCl3, 75 MHz):
δ 182.6,
5
6
7
8
9
146.8, 145.4, 143.2, 139.5, 139.2, 136.7, 133.3, 129.6, -0.3. MS (DART-Positive):
m/z ) 344.9 (100) [M+ + 1]. HRMS (DART-FTICR) m/z: [M+H]+ Calcd for
C12H13OS274SeSi 338.9396; Found 338.9397. IR (KBr): 3061, 2958, 2810, 1659, 991,
843 cm-1.
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6-Trimethylsilanyl-diselenopheno[3,2-b:2
was synthesized according to the compound 16a procedure. 16c: brown solid in yield
of 52% (0.15 g); Mp: 160-163 oC. 1H NMR (CDCl3, 300 MHz):
(ppm) 9.84 (s, 1H),
8.20 (s, 1H), 7.69 (s, 1H), 0.38 (s, 9H). 13C{1H}NMR (CDCl3, 75 MHz):
184.1,
′,3'-d]thiophene-2-carbaldehyde
(16c)
δ
δ
154.5, 149.1, 148.2, 142.4, 140.8, 138.2, 133.5, 128.9, 0.0. MS (MALDI-FT_DHB):
m/z ) 392.9(100) [M++1]. HRMS (MALDI-FT_DHB-FTICR) m/z: [M+H]+ Calcd for
C12H13OSSe2Si 392.8782; Found 392.8782. IR(KBr): 3066, 2960, 1642, 1219, 960,
831 cm-1.
6-Trimethylsilanyl-diselenopheno[3,2-b:2
was synthesized according to the compound 16a procedure. 16d: brown solid in yield
of 49% (0.11 g), Mp: 166-168 oC. 1H NMR (CDCl3, 300 MHz):
(ppm) 9.84 (s, 1H),
8.21 (s, 1H), 7.72 (s, 1H), 0.38 (s, 9H). 13C{1H}NMR (CDCl3, 75 MHz):
183.9,
′,3'-d]selenophene-2-carbaldehyde (16d)
δ
δ
154.0, 148.0, 147.3, 143.0, 140.3, 139.8, 136.2, 131.7, 0.0. MS (MALDI-FT_DHB):
m/z ) 440.8 (88) [M+ + 1]. HRMS (MALDI-FT_DHB-FTICR) m/z: [M + H]+ Calcd
for C12H13OSe3Si 440.8226; Found 440.8228. IR (KBr): 3068, 2948, 1666, 1243, 960,
831 cm-1.
Synthesis of 1,2-bis(6-trimethylsilanyl-dithieno[3,2-b:2′,3'-d]thiophene-2-yl)ethene (17a)
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TiCl4 (0.66 mL, 6.07 mmol, 5.00 equiv) was carefully added into dry THF (30
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o
o
mL) at 0 C. After keeping at 0 C for 20 min, zinc dust (0.79 g, 12.14 mmol, 10.00
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9
o
equiv) was added, and then the mixture was refluxed at 100 C for 2 h. After that,
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pyridine (0.49 mL, 6.07 mmol, 5.00 equiv) was added and the mixture was refluxed
for another 1 h. After cooling to ambient temperature, a solution of 16a (0.36 g, 1.21
mmol) in dry THF (15 mL) was added and the reaction mixture was refluxed at 100
o
oC for 18 h. The reaction was quenched with water at 0 C, then extracted with
CH2Cl2 (3 × 30 mL) and washed with saturated NaHCO3 (25 mL) and H2O (2 × 25
mL), and then dried over MgSO4. After removing the solvent in vacuum, the residue
was washed with Et2O (3 × 5 mL) to yield 17a (0.22 g, 65%) as a orange solid.
Mp: >300 oC. 1H NMR (CDCl3, 300 MHz):
δ
(ppm) 7.36 (s, 2H), 7.21(s, 2H), 7.08 (s,
143.7, 143.4, 143.0, 142.4,
2H), 0.38 (s, 18H). 13C{1H}NMR (CDCl3, 100 MHz):
δ
135.8, 129.4, 126.7, 121.8, 119.8, -0.3. MS (DART Positive Ion Mode): m/z )
561.0(100) [M+ + 1]. HRMS (DART-FT-ICR) m/z: [M + H]+ Calcd for C24H25S6Si2
560.9814; Found 560.9814. IR (KBr): 3065, 2951, 1390, 1251, 991, 833 cm-1.
1,2-Bis(6-trimethylsilanyl-selenopheno[3,2-b:4,5-b']dithiophen-2-yl)ethene (17b)
was synthesized according to the compound 17a procedure. 17b: orange solid in yield
o
1
of 60% (0.12 g), mp: >300 C. H NMR (CDCl3, 300 MHz):
δ
(ppm) 7.40 (s, 2H),
142.8,
7.25 (s, 2H), 7.08 (s, 2H), 0.38 (s, 18H). 13C{1H}NMR (CDCl3, 100 MHz):
δ
142.4, 141.3, 139.9, 137.4, 130.8, 129.6, 122.9, 121.6, -0.2. MS (DART-Positive): m/z
655.8 (100) [M+]. HRMS (MALDI-TOF) m/z: [M]+ Calcd for C24H24S4Se2Si2
655.8630; Found 655.8610. IR (KBr): 3070, 2958, 1623, 1251, 991, 843 cm-1.
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1,2-Bis(6-trimethylsilanyl-diselenopheno[3,2-b:2′,3'-d]thiophene-2-yl)ethene
4
5
6
7
8
(17c) was synthesized according to the compound 17a procedure. 17c: orange solid in
o
yield of 41% (0.04 g, a mixture of cis and trans isomers), mp: >300 C. 13C NMR
1
9
spectra were not recorded due to its poor solubility at 353K. H NMR (CDCl3, 400
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MHz) for a mixture of cis and trans isomers of 17c.
δ (ppm) 7.64 (s), 7.63 (s), 7.50 (s),
7.37 (s), 6.99 (s), 6.75 (s), 0.37 (s), 0.35(s). The ratio of integral areas of the peaks at
6.99 and 6.75 ppm is 0.60:1.00. MS (MALDI-FT_DHB): m/z ) 748.8 (90) [M+].
HRMS (MALDI-FT_DHB-FTICR) m/z: [M + H]+ Calcd for C24H25Se4S2Si2 752.7592;
Found 752.7592. IR (KBr): 3063, 2960, 984, 843 cm-1.
1,2-Bis(6-trimethylsilanyl-diselenopheno[3,2-b:2
′,3'-d]selenophene-2-yl)ethene
(17d) was synthesized according to the compound 17a procedure. 17d: orange solid
o
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in yield of 46% (0.03 g, a mixture of cis and trans isomers), Mp: >300 C. H NMR
(CDCl3, 400 MHz) for a mixture of cis and trans isomers of 17d. (ppm) 7.673 (s),
δ
7.668(s), 7.526 (s), 7.399 (s), 6.988 (s), 6.738 (s), 0.369 (s), 0.351 (s). The ratio of
integral areas of the peaks at 6.988 and 6.738 ppm is 1.00:0.93. 13C{1H}NMR
(C2D2Cl4, 353K, 100 MHz):
δ 149.8, 147.4, 143.1, 141.3, 139.9, 133.6, 131.7, 125.3,
124.8, 0.0. MS (MALDI-FT_DHB): m/z ) 844.7 (100) [M+ + 1]. HRMS
(MALDI-FT_DHB-FTICR) m/z: [M + H]+ Calcd for C24H25Se6Si2 848.6481; Found
848.6484. IR(KBr): 3050, 2948, 972, 843 cm-1.
Synthesis of 4,4'-bis(trimethylsilanyl)benzo[1,2-
thiophene) (3a)6
b:3,4-b']bis(dithieno[3,2-b:2′,3'-d]
To a solution of 17a (0.010 g, 0.018 mmol) in dry toluene (25 mL), iodine (0.014
g, 0.050 mmol, 3.00 equiv) was added. The reaction solution was irradiated with a
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450 W unfiltered Hg medium pressure lamp for 40 minutes. The reaction was
quenched with saturated Na2S3O3 (10 mL). The reaction mixture was extracted with
CH2Cl2 (3 × 10 mL) and washed with H2O (3 × 10 mL), and then dried over MgSO4.
After removing the solvent in vacuum, the crude product was purified by PTLC with
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petrol ether (60-90 C) HEX/CH2Cl2 (v/v = 3:1) as developer to yield 3a (0.003 g,
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30%) as a light yellow solid, mp: >300 C. H NMR (300 MHz, CDCl3):
δ
δ
(ppm)
144.3,
7.83(s, 2H), 7.51 (s, 2H), 0.42 (S, 18H), 13C{1H}NMR (100MHz, CDCl3):
144.2, 139.3, 136.0, 135.9, 129.9, 127.2, 126.6, 120.0, -0.1. MS (DART-Positive Ion
Mode): m/z ) 559.0 (96) [M+ + 1]. HRMS (DART-FTICR) m/z: [M + H]+ Calcd for
C24H23S6Si2 558.9657; Found 558.9656. IR (KBr): 3065, 2958, 1399, 1334, 1251, 991,
842 cm-1.
4,4'-Bis(trimethylsilanyl)benzo[1,2-b:3,4-b']bis(selenopheno[3,2-b:4,5-b']dithiophene)
(3b)6 was synthesized according to the compound 3a procedure. 3b: light yellow solid
in yield of 30% (0.005 g), mp: >300 oC. 1H NMR (CDCl3, 300 MHz):
2H), 7.53 (s, 2H), 0.42 (s, 18H). 13C{1H}NMR (CDCl3, 100 MHz):
δ
δ
(ppm) 7.83 (s,
143.8, 142.0,
139.0, 137.3, 133.5, 131.2, 130.0, 129.3, 119.9, -0.1. MS (DART-Positive): m/z )
653.8 (100) [M+]. HRMS (MALDI-TOF) m/z: [M]+ Calcd for C24H22S4Se2Si2
653.8474; Found 653.8495. IR (KBr): 3061, 2968, 1632, 1251, 991, 843 cm-1.
4,4'-Bis(trimethylsilanyl)benzo[1,2-b:3,4-b']bis(diseleno[3,2-b:2
′,3'-d]thiophene)
(3c)6 was synthesized according to the compound 3a procedure. 3c: light yellow solid
o
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in yield of 20% (0.0024 g), mp: 292-294 C. H NMR (CDCl3, 300 MHz):
7.81 (s, 2H), 7.78 (s, 2H) , 0.41 (s, 18H). 13C{1H}NMR (CDCl3, 100 MHz):
δ
(ppm)
δ
151.31,
145.23, 141.08, 137.93, 137.90, 131.23, 130.83, 128.83, 123.04, 0.18. MS
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