Tristhienylphenylamine - Extended dithiafulvene hybrids as bifunctional electroactive species

Article abstract of DOI:10.1039/c0ob00471e

Extended hybrid conjugated systems based on a trithienylphenylamine core with 1, 2 and 3 peripheral dithiafulvenyl units have been synthesized and studied by cyclic voltammetry and UV-Vis. absorption spectroscopy. Theoretical calculations have also been u

Full text of DOI:10.1039/c0ob00471e

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PAPER
Tristhienylphenylamine – extended dithiafulvene hybrids as bifunctional
electroactive species†
Emilie Ripaud, Philippe Leriche,* Nicolas Cocherel, Thomas Cauchy, Pierre Fre`re and Jean Roncali
Received 22nd July 2010, Accepted 29th October 2010
DOI: 10.1039/c0ob00471e
Extended hybrid conjugated systems based on a trithienylphenylamine core with 1, 2 and 3 peripheral
dithiafulvenyl units have been synthesized and studied by cyclic voltammetry and UV-Vis. absorption
spectroscopy. Theoretical calculations have also been undergone. The behaviour of these derivatives
which depends on the number of dithiafulvene moieties grafted of the central core is cleared up. One
polymer, obtained from derivative 3 presents polyelectrochromic properties.
Introduction
Results and discussion
Triphenylamine systems substituted with (oligo)thiophene func-
tionalities are in the focus of much interest.1 Thus, these derivatives
are interesting as active materials in organic electronic devices2 and
as block for electroactive polymers.3 In this trend, we have recently
described a series of triphenylamine-dithiafulvene hybrid systems
which have been incorporated in organic field effect transistors
and in solar cells.4 These derivatives present a very rich elec-
trochemistry and are potentially interesting as new electroactive
materials.5 Therefore, in the continuation of our current work on
hybrid systems associating TPA and dithiafulvene moieties, we
have focused our interest on compounds 1–3 which bear 1 to 3
dithiafulvene groups separated from the triphenylamine node by
one thiophene spacer (Chart 1). Their syntheses, electrochemical
and spectroscopic properties are presented as well as those
of corresponding polymers. Electrochemical and spectroscopic
experiments on compounds and corresponding polymers provide
a coherent picture of the behaviour of these derivatives.
Synthesis
Derivatives 1–3 have been synthesized by condensation of 4,5-
dimethylthio-2-thioxo-1,3-dithiole on aldehydes 4–6 (Scheme 1).6
Trisaldehyde 6 was obtained in 90% yield by Vilsmeier reaction
after treatment of the trithienylphenylamine with 4 equivalents
of POCl3/DMF.7 The use of 2 eq of POCl3/DMF led to a
mixture of derivatives 4, 5 and 6 in respectively 27, 25 and 20%
yields. This reaction well reproducible can be envisioned in large
scales and the purification of derivatives 4–6 is easy due to their
important difference of polarity. After condensation of dithioles
onto aldehyde functionalities in the presence of triethylphosphite,
the target compounds 1–3 were isolated by precipitation at
the end of the reaction by addition of petroleum ether or
methanol in the reaction mixture. Derivatives were then purified by
Chart 1
University of Angers, CNRS, MOLTECH-Anjou,
2 Bd Lavoisier,
49045, Angers, France. E-mail: philippe.leriche@univ-angers.fr; Fax: +33
(0)241735405; Tel: +33 (0)241735010
† Electronic supplementary information (ESI) available: UV-Vis spectra
of compounds 1–3 –Deconvoluated CV of compound 1, 2, 9 – CV of 7,
molecular orbital diagrams of 1–3, theoretical absorption spectrum of 1,
NMR spectra of compounds. See DOI: 10.1039/c0ob00471e
Scheme 1 Synthesis of compounds 1–6.
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Table 1 Theoritical, spectroscopic and electrochemical data for deriva-
tives 1–3
Table 1 lists the calculated HOMO and LUMO energies for
compounds 1–3. As the localizations of these later are analogous,
their energetic levels are very close together to leaving predict sim-
ilar electronic, spectroscopic and electrochemical measurements.
Nevertheless, passage from 1 to 3 leads to a slight increase of the
HOMO level accompanied with a gap decrease.
Thus, in UV-vis spectroscopy, all compounds present a broad
p–p* absorption band with a lmax which shows a slight red shift
from 422 to 436 nm when the number of dithiole rings grafted on
the trithienylphenylamine node increases from 1 to 3.
b
b
Cpnd lmaxa/nm
Epa1
Epa2
HOMO
LUMO
GAP
1
2
3
422
423
436
0.56
0.54–0.60
0.54
0.71
0.87
0.89
-4.96
-4.85
-4.78
-1.60
-1.62
-1.62
3.36
3.20
3.16
a 10-5 M in CH2Cl2; b oxidation peak vs. SCE measured from cyclic
voltammetry, <10-4 M of compounds in CH2Cl2 with 0.1 M Bu4NPF6
as supporting electrolyte, v = 100 mV s-1
Cyclic voltammetry was performed in methylene chloride in the
presence of 0.10 M tetrabutylammonium hexafluorophosphate as
supporting electrolyte. The CV of compounds 1–3 show at least
precipitation in mixtures of solvents or when necessary carefully
flash-chromatographied on neutral alumina gel in mixtures of
methylenechloride/hexane with 1% of triethylamine in order to
avoid oxidation. They all were satisfactorily characterized by
NMR and mass spectrometry.
1
two series of oxidation processes with anodic peak potentials Epa
2
and Epa in the 0.50-0.60 and 0.70–0.90 V regions. As shown in
Table 1, Epa1 is roughly independent of the number of dithiole rings
2
on the molecule, in contrast to Epa which shifts positively from
0.71 V for 1 to 0.89 V for 3. The number of electrons involved in
each redox process and the eventual formation of new compounds
upon oxidation depend on the number of dithiole rings grafted on
the trithienylphenylamine core.
Theoretical calculations, spectroscopic and electrochemical
measurements
The electronic properties of compounds 1–3 have been analyzed by
ab initio theoritical calculations, UV-Vis absorption spectroscopy
and cyclic voltammetry; the corresponding data are listed in Table
1. The geometries of compounds 1–3 have been optimized with
DFT calculations (see exp. Part). The HOMO and LUMO of
compound 1 are shown on Fig. 1 (More complete orbital diagrams
of the three compounds are presented on ESI†).
CV of compounds 1–3 are shown on Fig. 2, deconvoluated CV
of 1–2 are shown on ESI.† In diluted solution (<10-4 M) derivative
1 undergoes two 1 electron reversible oxidation processes at
0.56 and 0.71 V respectively (Table 1, Fig. 1, ESI†) leading to
stable radical cation and dication. Derivative 2 undergoes two
series of reversible oxidation waves. The first one, close to that
of 1, corresponds to two quasicoalescent 1 electron processes
respectively at 0.54 and 0.60 V. The second one at 0.87 V
corresponds at one electron as demonstrated on deconvoluated CV
(ESI†). Thus, the two first processes at 0.54 and 0.60 V correspond
to the oxidation of the dithiolilydene moieties as the last one at
higher potential can be attributed to the trithienylphenylamine
core. Fig. 1 (bottom) shows the first and third scans of the CV of
derivative 3. Since compound 3 undergoes polymerization in the
first cycle, it is difficult to attribute the different waves to monomer
or polymer. However, by comparison with the CV of Poly(3), (Fig.
5. bottom), the waves at 0.54, 0.89 V and 1.3 V can be attributed
to 3.
Note that the first oxidation waves of 1–3 are very close together
oscillating between 0.54 and 0.56 V what is in accordance with
theoritical calculations and shows that the processes are similar
in all cases. Moreover the relative intensities of the two redox
processes are correlated with the number of dithiole rings grafted
on the core; compound 1 presents two 1 electron processes,
derivative 2, two very close 1 electron processes followed by one
single electron process at higher potential. For 3, the relative
intensities are more difficult to determine as this derivative does
not undergo reversible processes. Nevertheless, the two processes at
0.54 and 0.89 V can be attributed to 3 and 1 electrons respectively.
Thus, for each compound 1–3, the first process(es) around 0.55 V
correspond(s) to the oxidation of the peripheric dithiole ring(s) as
the second one, at higher potential, is attributable to the central
trithienylphenylamine core. Moreover, the second oxidation po-
tential increases with the number of dithiole rings grafted on the
TPA core passing from 0.71 V for 1 to 0.89 V for 3. This behavior
can be explained by the intramolecular coulombic repulsions
which are higher in the tetracation 34+ than in the radical trication
Fig. 1 Frontrier orbitals of compound 1.
As generally observed for TPA derivatives, the three N–C
bonds of compounds are coplanar what is characteristic of
enamines. Steric hindrances between the phenyl rings grafted on
the central nitrogen atom generate the typical propeller shape of
the molecules.
The HOMO and LUMO levels of compound 1 (Fig. 1) are
mostly located on the arm which bears the dithiole ring with very
little contributions of nude thiophene rings. Note that the LUMO
of 1 is strongly quino¨ıdic. HOMO and LUMO localizations on
compounds 2 and 3 are analogous. Depending on the number of
dithiole rings (2 or 3), different combinations of the same HOMO
or LUMO than that of 1 form the frontier orbitals of compounds
2 and 3 (ESI†). TD-DFT calculations have been undergone for
derivative 1 and show unambiguously that the low lying energy
transition is centered on the arm which bears the dithiafulvene
group (ESI†).
∑
23+ and dication 12+. Thus, in dilute conditions 1 and 2 lead to
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Scheme 2
to the extended analogue of TTF11 8. This slightly stable com-
pound presents a trithienylphenylamine core substituted by three
extended analogues of TTF. Upon oxidation, this derivative does
not undergo polymerization but presents 3 reversible processes
at 3, 3 and 1 electrons at 0.45, 0.63 and 1.13 V respectively
(Fig. 3, ESI†). The two first processes are attributable to the
oxidation of the lateral extended TTFs in radical cations and
dications; the last single electron wave corresponds to the oxidation
of the central node. The blocking of the dithiafulvenyle positions
Fig. 2 CV of 1 (top), 2 (middle) and 3 (back, line 1st scan, dotted line 3rd
scan), CH2Cl2 TBAPF6 0.1 M 100 mV s-1.
stable oxidized species as 3 polymerizes. In more concentrated
conditions (around 10-3 M), the first oxidation process of 1 appears
less reversible and a blue coloration appears in solution around the
electrode what is characteristic of the formation of a new species
near the electrode. Considering the structures of molecules and
previous works based on thienylfulvalene systems,5,8 it is strongly
probable that a coupling reaction occurs at the vinyl linkage
connecting the dithiafulvene and the thienyl moieties. In the case
of 1, this coupling may lead to a sterically contraint extended TTF
while in that of 3 a polymeric system is expected.
In order to confirm this supposition and to eliminate an
hypothetical electrodeposition of the compound 3,9 we have
blocked the incriminate positions (Scheme 2). For this purpose
derivative 7 with 3 aldehyde functionalities has been synthesized
by Viels-Meyer reaction starting from 3.10 This later, engaged
in a WH reaction with the Akiba’s reagent of EDT-dithiole led
Fig. 3 CV of 8, CH2Cl2 TBAPF6 0.1 M 100 mV s-1.
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thus prevents the duplication of compounds what confirms the
localization of the coupling process.
oxidation potential is easier and leads to thicker films (Fig. 5, top).
Poly(3), studied in a free monomer electrolytic solution presents
two well discriminated processes with relative intensities of 3 and
1 at 0.6 and 0.74–0.8 V respectively (Fig. 5, bottom). These redox
processes very close to those of 3 are well reversible andcycling
up to the second redox process for an hundred cycles led the
film unchanged. Thus, poly(3) presents two reversible and well
disjointed redox processes.
This observation is sustained by chemical oxidation of 1 with
DDQ and HBF4.12 After reduction with zinc, compound 9,
which results from a coupling at the vinylic linkage is isolated
in 30% yield together with a large part of the starting material
(Scheme 3).
Scheme 3
The UV-vis. spectrum of 9 shows two maxima at 374 and 417
nm at higher energies than that of 1 at 422 nm. This behaviour
already observed for extended TTF is due to a lack of conjugation
consecutive to steric hindrances between the aromatic rings.8 For
the same reason, compound 9 presents two first reversible redox
processes at higher potentials than 1 at 0.70 and 0.86 V respectively
(ESI†).
At the higher potential of 1.5 V, compound 9 presents a third
non reversible peak. Recurrent oxidation until this later leads to
the difficult formation of a polymeric film on the surface of the
electrode. The polymer which results from thiophene-thiophene
couplings upon oxidation has been studied in a free monomer
electrolytic solution. Poly(9) shows a main intense process between
0.5 and 1 V with a maximum at 0.9 V followed by a less important
one centered on 1.1 V (Fig. 4).
Fig. 5 (top) Electropolymerization of 3, CH2Cl2 TBAPF6 0.1 M 100 mV
s-1 (bottom) CV trace of poly(3) deposited on Pt in CH3CN Bu4NPF6
0.1 M 100 mV s-1.
As a first evaluation of its electrochromic properties, derivative
3 has been electropolymerized on ITO. The film is stable in its
neutral state and can be stored several hours in ambient conditions
without degradation or oxidation. The maximum of absorption of
the yellow polymer in its neutral state is close to that of 3 at 437
nm. In CV, the film of poly(3) always presents two well disjoigned
reversible redox processes thus allowing to study the two oxidation
states by spectroelectrochemistry (Fig. 6).13 The first process leads
to a blue film with 2 maxima respectively at 403 nm and 703 nm.
Oxidation until the second process leads to a stable grey-violet film
which strongly absorbs in the IR region. During each oxidation
process the presence of isobestic points on the spectroscopic trace
confirms the stability of oxidized species.
Fig. 4 CV of poly(9) deposited on Pt, CH3CN Bu4NPF6 0.1 M 100 mV
s-1.
Conclusion
During this work we have synthesized three new hybrids incor-
porating a trithienylphenylamine core and one to three dithiaful-
venyle moieties. Electrooxidation of these compounds, cleared up
by chemical oxidation of 1 as well as by blocking of incriminate
As already mentioned, derivative 3 polymerizes at its first oxida-
tion state which leads to the trication radical 33+∑. Nevertheless, the
electropolymerization in potentiodynamic conditions at its second
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iments were carried out with a home-made cell on polymers
grown on ITO. Trithienylphenylamine was prepared from tris-
4-bromophenylamine as described in litterature.14
Computational details
The molecular orbitals have been calculated for the optimized
geometries of compound 1–3. A full geometry optimization for 1
and 2, and a constrained optimization (restricted to a C3 symmetry
point group) for 3 have been carried out using Density Functional
Theory (DFT) methods. All calculations were performed with the
hybrid adaptation of the PBE functional15–16 (usually referred as
PBE0) as implemented on the Gaussian09 program.17 A triple-z
quality basis set proposed by Weigend et al. has been used with
polarization functions for all atoms (TZVPP).18 Then the first
mono-electronic excitations (10 firsts) were computed using a Time
Dependant Density Functional Theory (TD-DFT) procedure with
the same program, functional and basis set as the optimization step
(see ESI†).
Compounds 4–5
To 500 mg (1 mmol) of tris[4-(2-thienyl)phenyl]amine dissolved
in 30 mL of 1,2-dichloroethane, 0.12 mL of dimethylformamide
(1.5 mmol) and 0.14 mL of phosphorus oxychloride (1.5 mmol)
are added. The mixture is heated to reflux under nitrogen and
kept stirred overnight. After cooling, 50 mL of methylene chloride
and 100 mL of saturated sodium acetate solution are added
and stirred 1 h. Then, the mixture is poured into water and
extracted with methylene chloride. The organic phase is separated,
washed with water and dried with magnesium sulfate. After
evaporation of solvent, the residue is purified by silica column
chromatography (methylene chloride as eluent) to give 140 mg of
[mono[4-(2-thienylformyl)phenyl]bis[4-(2-thienyl)phenyl] amine 4
(yield: 27%) and 140 mg of [bis[4-(2-thienylformyl)phenyl]mono[4-
(2-thienyl)phenyl]]amine 5 (yield: 25%). Compound 6 was also
obtained in 20% yield.
Fig. 6 Electronic absorption spectra of a film of poly(3) on ITO electrode
in CH3CN Bu4NPF6 0.1 M; (Top) from its reduced form at 0 V to 0.6 V;
(bottom) from 0.6 V to its fully oxidized form at 1 V. line (neutral and fully
oxidized states) – short dash (partially oxidized state at 0.6 V) – dotted
lines (intermediate states).
positions in 8, leads to dimerization or polymerization products
at the vinylic linkage between the thiophene and the dithiole rings.
Poly(3) allows the observation of two well resolved and reversible
redox processes. This polymer, electrogenerated on an ITO plate,
presents three coloured stable redox states and can be considered
as a first example of polychrome mixed TPA-TTF system. Efforts
are now in due course in order to get soluble and processable
polymers in this family.
Compound 4: NMR 1H (CDCl3): 9.87 (s, 1H)- 7.72 (d, 1H, 3J =
3
4 Hz)- 7.55 (m, 6H)- 7.33 (d, 1H, J = 4 Hz)- 7.27 (m, 4H)- 7.15
Experimental
(m, 6H)- 7.08 (dd, 2H, 3J = 3,5 Hz, 3J = 5 Hz); NMR 13C (CDCl3):
182.6; 154.3; 148.4; 145.9; 143.8; 141.5; 137.7; 130.0; 128.1; 127.4;
127.0; 126.8; 125.0; 124.5; 123.2; 123.1; 122.7; IR (C O) 1647
cm-1; SM (Malditof) C31H21NOS3: ms M+∑: 519.1, theo: 519,08;
HRMS M+ (calcd) (519.07798) 519.0780.
General experimental
1
Solvents were purified and dried using standard protocols. H-
NMR and 13C NMR spectra were recorded on a Bruker AVANCE
DRX 300 spectrometer; d are given in ppm (relative to TMS)
and coupling constants (J) in Hz. Matrix-assisted laser desorp-
tion ionization time-of-flight (MALDI-TOF) mass spectra were
recorded by a Bruker Biflex-III, equipped with a N2 laser (337 nm).
For the matrix, dithranol in CH2Cl2 was used. High resolution
mass spectra were recorded under FAB mode on a Jeol JMS 700
spectrometer. UV-visible optical data were recorded with a Perkin-
Elmer lambda 19 spectrophotometer. For cyclic voltammetry
(scan rate 100 mV cm-1), the electrochemical apparatus consisted
of a potentiostat EG&G PAR 273A and of a standard three-
electrode cell. As the working and counter electrodes, a platinum
foil and a platinum wire were used, respectively, while a SCE
electrode served as reference. Electrochemical experiments were
carried out in methylene chloride or acetonitrile (spectro grade)
containing 0.10 M tetrabutylammonium hexafluorophosphate
(Fluka puriss, used as received). Spectroelectrochemical exper-
1
Compound 5: NMR H (CDCl3): 9.87 (s, 2H)- 7.73 (d, 2H,
3
3J = 4 Hz)- 7.58 (m, 6H)- 7.34 (d, 2H, J = 4 Hz), 7.28 (m, 2H)-
3
3
7.17 (m, 6H)- 7.09 (dd, 1H, J = 3,5 Hz, J = 10 Hz); NMR 13C
(CDCl3): 182.7; 153.9; 147.9; 145.5; 143.6; 141.7; 137.7; 130.6;
128.1; 127.676; 127.5; 127.1; 125.6; 124.7; 123.9; 123.3; 122.9; IR
(C O) 1655 cm-1; SM (Malditof) C32H21NO2S3: ms M+∑: 547.1,
theo: 547.078; HRMS M+Na+ (calcd) (570.0627) 570.0629
[4-((4,5-bis(methylthio)-1,3-dithiol-2-ylidene)methyl)thienyl-
phenyl]dithienylphenylamine 1
100 mg (0.19 mmol) of [4-(5-formyl-2-thienyl)phenyl]-bis[4-(2-
thienyl)phenyl]amine 4 and 87 mg (2 eq) de 4,5-bis(methylthio)-
2-thioxo-1,3-dithioleare dissolved in 2 mL of boiling toluene
afterwhat 2 mL of dry triethylphosphite are added. The mixture
is refluxed 4 h under nitrogen atmosphere. After cooling and
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addition of methylenechloride, the mixture is washed with brine
and dried on magnesium sulfate. After evaporation of solvent the
residue is washed with methanol affording 220 mg of a pure rusty
solid.
Derivative 7
0.2 mL of phosphorus oxychloride and 0.3 mL of dry DMF
are added at 0 ◦C under nitrogen atmosphere in 30 mL of
methylenechloride.50 mg of derivative 3 (4.5 10-5 mol) are then
added and the mixture is refluxed overnight. After cooling, 50
mL of an aqueus solution of sodium acetate 4 M are added
and the mixture is stirred 2 h. The organic phase is then washed
with water and dried on magnesium sulfate. After evaporation of
the solvent, the residue is chromatographied on siliga gel using
methylenechloride as eluent. 30 mg of trisaldehyde 8 are isolated
as a red glassy solid. Yield: 56%; NMR1H (CDCl3): 9.53 (s, 3H)-
◦
yield: 38%; Decompª95 C; Rf 0.39 (EP/CH2Cl2 2 : 1); NMR
1H (CDCl3): 7.52 (d, 4H, 3J = 8.5 Hz)- 7.50 (d, 2H, 3J = 8.5 Hz)-
3
3
7.25 (m, 4H)- 7.19 (d, 1H, J = 4 Hz)- 7.14 (d, 4H, J = 9 Hz)-
7.14 (d, 2H, 3J = 8.5 Hz)- 7.08 (dd, 2H, 3J = 4 Hz et 3J =
5 Hz)-6.82 (d, 1H, J = 4 Hz)- 6.66 (s, 1H)- 2.47 (s, 3H)- 2.45
3
(s, 3H).; NMR 13C (CDCl3): 146.4- 146.3- 144.0- 142.5 139.3-
130.1- 129.3- 129.1- 128.1- 128.0- 126.9- 126.4- 125.3- 125.2-
125.1- 124.4- 124.3- 122.8- 122.5- 108.5- 19.2- 19.0; MS (Malditof)
C42H33NS9: ms M+∑: 902.8, theo: 902.9; SM (Malditof) C36H27NS7:
ms M+∑: 696.9, theo: 697.0; HRMS M+ (calcd) (697.0188)
697.0201
3
3
7.54 (d, 6H, J = 8.5 Hz)- 7.26 (d, 3H, J = 4.5 Hz)- 7.15 (d,
3
3
6H, J = 8.5 Hz)- 7.13 (d, 3H, J = 3.5 Hz)- 2.56 (s, 9H) 2.46 (s,
9H).NMR13C (CDCl3): 183.3- 161.3- 146.5- 143.9- 136.9- 134.2-
128.8- 127.4- 126.8- 126.4- 124.4- 122.8- 115.5- 19.3- 18.8.; HRMS
M+ (calcd): 1192.8755 (1192.8735)
Derivative 8
Bis-[4-((4,5-bis(methylthio)-1,3-dithiol-2-ylidene)methyl)thienyl-
phenyl]thienylphenylamine 2
18 mg of derivative 7 (1.5 10-5 mol) and 60 mg (1.9 10-4 mol) of the
phosphonate of ethylenedithiodithiole are dissolved in 5 mL of dry
THF under nitrogen atmosphere. 1.5 10-4 mol of t-BuOK (solution
1 M) are then added and a yellow powder immediately appears.
The mixture is stirred 1 h and 5 mL of methanol are added. After
1 h of flocculation, the powder is filtered, washed with methanol.
23 mg of derivative are isolated as a yellow powder. Yield: 89%; Rf
(CH2Cl2/EP 1/1): 0.4 – oxidation on the plate; NMR1H (CD2Cl2):
7.55 (d, 6H, 3J = 8.5 Hz)-7.26 (d, 3H, 3J = 4 Hz)- 7.14 (d, 6H, 3J =
8.5 Hz)- 6.94 (d, 3H, 3J = 3.5 Hz)- 5.20 (s, 3H)- 3.25 (m, 12H)- 2.44
(s, 9H) 2.38 (s, 9H); MS (Malditof)(calcd): (M+H, 1721.6) 1721.9
50 mg of dialdehyde 5 and 100 mg de 4,5-dimethoxy-2-thioxo-1,3-
dithiole are dissolved in 5 mL of boiling toluene afterwhat 1 mL
of dry triethylphosphiteis added. The mixture is refluxed 1 h 30
min under nitrogen atmosphere. After cooling 30 mL of petroleum
ether are added in the flask and the mixture is stirred one hour. The
pure yellow powder is then filtered, washed with petroleum ether
and dried. Yield: 70%; Rf 0.7 (CH2Cl2/EP); Tcompª107 ◦C; NMR
1H (CDCl3): 7.51 (d, 2H, 3J = 8.5 Hz)- 7.50 (d, 4H, 3J = 8.5 Hz)-
7.25 (m, 2H)- 7.19 (d, 2H, 3J = 4 Hz)- 7.13 (d, 2H, 3J = 8.5 Hz)-
7.12 (d, 4H, 3J = 8.5 Hz)- 7.07 (d*d, 1H, 3J = 5 Hz 3J = 3.5 Hz)-
3
6.82 (d, 2H, J = 4 Hz)- 6.66 (s, 2H)- 2.47 (s, 6H)- 2.45 (s, 6H);
Derivative 9
NMR13C (CD2Cl2):147.0- 146.9- 144.5- 143.0- 138.8- 130.8- 129.8-
129.6- 128.8- 128.6- 127.3- 126.8- 125.8- 125.6- 125.0- 124.9- 124-
8- 123.4- 123.0- 108.8- 19.5- 19.3; HRMS M+ (calcd) (902.95353)
902.95279
50 mg of 1 (7.2 10-5 mmol) are dissolved in 50 mL of dry diethyl
ether. Then 30 mg of DDQ, 0.4 mL of HBF4,H2O and two drops
of concentrated hydrochloric acid are added. The yellow solution
turns deep green and is stirred one hour at room temperature. After
addition of 50 mL dry diethyl ether the very thin powder is filtered
on celite (the filtrate is mostly composed by starting unoxidized
derivative). The green precipitate is dissolved in acetonitrile, an
excess of zinc is added and the mixture is stirred 45 min at room
temperature. After filtration of zinc, the solvent is evaporated and
the residue dissolved in methylenechloride; the organic phase is
washed with water and then dried on magnesium sulfate. After
evaporation of the solvent, the residue is chromatographied on
silica gel using EP/CH2Cl21/2 as eluent affording 15 mg (30%) of
a yellow glassy solid. NMR1H (CDCl3): 7.52 (d, 8H, 3J = 8.5 Hz)-
7.50 (d, 4H, 3J = 8.5 Hz)- 7.25 (m, 10H thiophene)- 7.19 (d, 2H,
Tris-[4-((4,5-bis(methylthio)-1,3-dithiol-2-ylidene)methyl)thienyl-
phenyl]amine 3
200 mg of Tris[4-(5-formyl-2-thienyl)phenyl]amine 6(3.5 10-4 mol)
and 6 eq. de 4,5-dimethoxy-2-thioxo-1,3-dithiole (470 mg) are
dissolved in 8 mL of boiling toluene afterwhat 2 mL of dry
triethylphosphite are added. The mixture is refluxed 1 h under
nitrogen atmosphere. After cooling, 30 mL of petroleum ether are
added in the flask and the mixture is stirred one hour. The yellow
powder is then filtered, washed with petroleum ether and dissolved
in methylenechloride. The organic phase is washed with water and
dried on magnesium sulfate. After evaporation of the solvent, the
residue is dissolved in the minimum of methylenechloride and
chromatographied on silica gel using EP/CH2Cl2 1/1 then 1/2
and then CH2Cl2 as eluent. 300 mg of the target are isolated
(elution withEP/CH2Cl2 1/1). Yield: 82%; Decompª189 ◦C; Rf
0.6 (EP/CH2Cl2 1/1); NMR1H (CDCl3): 7.49 (d, 6H, 3J = 8.5 Hz)-
7.18 (d, 3H, 3J = 3.5 Hz)- 7.01 (d, 6H, 3J = 8.5 Hz)- 6.81 (d, 3H, 3J =
3.5 Hz)- 6.65 (s, 3H)- 2.46 (s, 9H)- 2,44 (s, 9H); NMR 13C (CDCl3):
146.2- 142.4- 139.2- 130.0- 129.1- 128.0- 126.3- 125.2- 125.1-
124.3- 122.8- 108.5- 19.1- 19.0; HRMS M+ (calcd): (1108.8893)
1108.8893.
3
3
3J = 4 Hz)- 7.14 (d, 8H, J = 8.5 Hz)- 7.12 (d, 4H, J = 8.5 Hz)-
7.01 (d*d, 4H, 3J = 5 Hz 3J = 4 Hz)- 2.49 (s, 6H)- 2.45 (s, 6H).
Acknowledgements
Authors thank the PIAM of Angers for analytical experiments
and the french government for granting E. Ripaud.
Notes and references
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