Tetrathiafulvalene mono- and bis-1,2,3-triazole precursors by click chemistry: Structural diversity and reactivity

Article abstract of DOI:10.1039/c4ob00148f

The donor ortho-dimethyl-TTF-(N-n-Bu-1,2,3-triazole) 1,5-isomer has been synthesized by click chemistry following a ruthenium-catalyzed azide-alkyne cycloaddition procedure. The single crystal X-ray analysis showed a planar conformation between the TTF an

Full text of DOI:10.1039/c4ob00148f

Volume 12 Number 20 28 May 2014 Pages 3139–3312
Organic &
Biomolecular
Chemistry
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ISSN 1477-0520
PAPER
Thomas Biet and Narcis Avarvari
Tetrathiafulvalene mono- and bis-1,2,3-triazole precursors by click
chemistry: structural diversity and reactivity

Organic &
Biomolecular Chemistry
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PAPER
Tetrathiafulvalene mono- and bis-1,2,3-triazole
precursors by click chemistry: structural diversity
and reactivity†
Cite this: Org. Biomol. Chem., 2014,
12, 3167
Thomas Biet and Narcis Avarvari*
The donor ortho-dimethyl-TTF-(N-n-Bu-1,2,3-triazole) 1,5-isomer has been synthesized by click chem-
istry following a ruthenium-catalyzed azide–alkyne cycloaddition procedure. The single crystal X-ray ana-
lysis showed a planar conformation between the TTF and triazole units and a set of intermolecular
interactions at the supramolecular level in the solid state. The same procedure allowed the preparation of
the corresponding ortho-dimethyl-TTF-bis(triazole) which was also structurally characterized. Because of
the steric hindrance, the triazole units are no longer planar with the TTF backbone. The reactivity of the
triazole ring has been investigated in protonation and alkylation reactions, monitored by UV-visible spec-
troscopy, which clearly showed the red shift of the intramolecular charge transfer band. A TTF-methyl-
triazolium salt has been isolated and analyzed by single crystal X-ray analysis. All of the TTF-triazoles and
triazolium salts are valuable precursors for radical cation salts due to their oxidation potentials and variety
of possible intermolecular interactions.
Received 20th January 2014,
Accepted 14th February 2014
DOI: 10.1039/c4ob00148f
www.rsc.org/obc
Introduction
Synthetic methods based on click chemistry strategies have
developed increasingly over the last decade,1 with one of the
most useful reactions being the copper-catalyzed azide–alkyne
cycloaddition (CuAAC) that allows the straightforward prepa-
ration of 1,2,3-triazoles (1,4-isomers).2 These heterocycles have
proved to be useful units in chemical sensing3 and peptidomi-
metic research,4 and are also interesting ligands towards tran-
sition metals.5 Alternatively, the 1,5-isomers of 1,2,3-triazoles
have been efficiently prepared by the azide–alkyne cyclo-
addition mediated by a ruthenium(II)-based catalyst.6 We have
recently employed both strategies for the synthesis of the new
electroactive ligands TTF-1,2,3-triazoles as 1,4- and 1,5-isomers
(Scheme 1),7 respectively, where the electroactive part is rep-
resented by the TTF (tetrathiafulvalene) unit, and in which
TTF and triazoles are directly connected. A large difference in
their electrochemical behavior was observed, e.g. much easier
oxidation for the 1,4-isomers than for the 1,5-isomers, and,
accordingly, in their relative kinetic stability. Moreover, coordi-
nation of the more stable 1,5-isomers to Cu(hfac)2 (hfac = hexa-
Scheme 1 TTF-1,2,3-triazoles.
fluoroacetylacetonate) fragments induced an unusual cathodic
shift of the oxidation potentials of TTF.
In the other few published examples of TTF-triazole
systems, with linkers of various lengths between TTF and tria-
zole,8 the latter serves mainly to connect other electroactive
moieties to TTF, such as perylene diimide9 or ferrocene.10
From a general point of view, the association of TTF with co-
ordinating groups within electroactive ligands11 represents a
powerful strategy to access either multifunctional molecular
materials, in which a combination of different physical
properties can be achieved,12 or electroactive catalysts.13 In
this respect, nitrogen-containing five-membered rings, such as
oxazolines,14 pyrazoles15 or imidazoles16 have been attached to
TTF, while the synthesis and coordination chemistry of TTF-
triazole ligands has been reported much more recently.7
Beside their use as ligands, the basicity and nucleophilicity of
the triazole ring should in principle allow for the modulation
of the intramolecular charge transfer and the electrodonating
Laboratoire MOLTECH-Anjou, Université d’Angers, CNRS, UMR 6200, UFR Sciences,
Bât. K, 2 Bd. Lavoisier, 49045 Angers, France. E-mail: narcis.avarvari@univ-angers.fr;
Fax: (+33)02 41 73 54 05; Tel: (+33)0241 73 50 84
†Electronic supplementary information (ESI) available. CCDC 982420–982423.
For ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/c4ob00148f
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character of TTF upon protonation or reaction with electro- enic) compound 5 which was further deprotected in the
philes.16b Moreover, the versatility of the two “click” strategies, presence of (n-Bu)4NF. The resulting TTF-bis(acetylene) 6 was
i.e. Cu versus Ru catalysis, guarantees the preparation of a then rapidly engaged in a double cycloaddition reaction with
whole library of TTF-triazoles by the appropriate choice of the benzyl azide following either the copper or the ruthenium-
acetylene and azide units. The substitution pattern, type of based catalysis (Scheme 3).
isomers, i.e. 1,4-versus 1,5-, and number of triazole units
While in the case of the Ru-catalyzed reaction the TTF-bis-
should have an important influence not only on the electro- (triazole) 8 was obtained in low yield (15%) as the bis(1,5-
chemical properties and coordination ability, but also on the isomer), the Cu-based catalysis afforded only the TTF-triazole-
supramolecular architectures in crystals, which ultimately acetylene 7 as the 1,4-isomer in even lower yield (10%) with no
determines the solid state properties of the derived materials. trace of the bis(triazole). The low yields are very likely attribu-
We report herein the synthesis, reactivity and solid state struc- ted to the sensitivity of the TTF-diacetylene 6 which partially
tures of TTF-mono and -bis(1,2,3-triazoles), together with degrades under the reaction conditions. Moreover, as pre-
those of a TTF-triazolium salt.
viously mentioned, the 1,4-isomers are less stable than the 1,5-
isomers,7 therefore compound 7, which is an intermediate
towards the desired bis(triazole), degrades before the second
acetylene unit reacts in the cycloaddition reaction. Neverthe-
less, a small amount of 7 could be purified by column chrom-
atography and characterized by 1H NMR and mass
spectrometry, yet the compound has a limited stability in air
even in the solid state.
Cyclic voltammetry measurements (see ESI†) show that the
oxidation potentials for the donor 2, of 0.45 and 0.85 V versus
SCE for E11/2 and E12/2 respectively, are identical to those for the
benzyl derivative 1. In the case of the bis(triazole) 8, anodic
shifts of 0.13 and 0.11 V for the first and second oxidation pro-
cesses are observed when compared to the mono(triazole) 1
(e.g. E11/2 = 0.44 V (1) and 0.57 V (8), E12/2 = 0.85 V (1) and 0.96 V
(8)), thus evidencing the withdrawing effect of the triazole ring
when connected to TTF as the 1,5-isomer.
Results and discussion
The TTF-triazole 1 (Schemes 1 and 2), with Me groups on TTF
and a benzyl (Bn) substituent on the nitrogen atom N1, was
synthesized as previously described by a Ru-catalyzed azide–
alkyne cycloaddition (RuAAC) reaction between the dimethyl-
TTF-acetylene and benzyl azide.7 In order to evaluate the influ-
ence of different substituents on the triazole ring, the ligand
TTF-triazole 2 with an n-butyl (n-Bu) group instead of Bn was
prepared following the same procedure by using n-butyl azide
(Scheme 2).
The donor ortho-dimethyl-TTF 3 is well suited for a selective
bis-functionalization, allowing us to attempt the preparation
of TTF-bis(triazoles) through both strategies. Accordingly, the
diiodo derivative 4 has been prepared upon the double lithia-
tion of 3 followed by treatment with perfluorohexyl iodide.
Then, a double Sonogashira coupling under classical con-
ditions with trimethylsilyl acetylene afforded the bis(acetyl-
The solid state structures of the mono(triazole) 2, bis(tria-
zole) 8, as well as the intermediate 5 (see ESI†), have been
determined by single crystal X-ray diffraction analysis.
The crystal structure of 1-butyl-5-(ortho-dimethyl-TTF)-
1,2,3-triazole (2)
The solid state structure of the benzyl derivative 1, previously
described,7 shows quasi-planarity between the TTF and tria-
zole units, with a dihedral angle of 6.0° and the s-trans confor-
mation, and the existence of short intermolecular S⋯S
contacts. In the case of 2, suitable crystals, as orange needles,
for X-ray analysis were obtained by the slow evaporation of the
Scheme 2 Synthesis of the TTF-mono(triazoles) 1 and 2.
Scheme 3 Synthesis of 7 and 8. Reaction conditions: (i) (n-Bu)4NF, THF–MeOH (1 : 1); (ii) CuI, PhCH2N3, CHCl3–DIPEA (1 : 1), 65 °C; (iii) Cp*RuCl-
(PPh3)2, PhCH2N3, THF, 65 °C.
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Fig. 3 Packing of 2 along the c axis with an emphasis on the N⋯S and
N⋯Hvinyl interactions.
Fig. 1 Molecular structure of 2 along with the numbering scheme.
structures of 17 and 2, one can disclose the planarity of the
system, suggesting conjugation between the two units.
The crystal structure of ortho-dimethyl-TTF-bis(1-benzyl-
1,2,3-triazol-5-yl) (8)
Single crystals of 8 as orange plates were obtained by vapour
diffusion of pentane into a solution of the compound in
methylene chloride. The donor crystallizes in the orthorhom-
bic system, with the non-centrosymmetric space group
P212121, with one independent molecule in the asymmetric
unit. The most striking peculiarity in the structure is the
non-planarity of the two triazole rings with respect to the
TTF backbone, with dihedral angles of 87.9° and 37.0°
for TTF⋯triazoleN1N2N3 and TTF⋯triazoleN4N5N6, respectively
(Fig. 4). This feature is very likely due to the steric hindrance
caused by the vicinity of the two heterocycles, which is com-
parable to the situation observed in the solid state structures
of TTF-mono(oxazolines)14a and TTF-bis(oxazolines).17 More-
over, the intramolecular π-stacking interaction established
between the triazole N4N5N6 and the Ph ring of the other tria-
zole unit, which are parallel at a distance of 3.4 Å, probably
also contributes to the stabilization of this conformation.
Bond lengths, such as the central C3vC4 bond and the
internal C–S bonds, have typical values for a neutral donor
(see ESI†).
Fig. 2 Columns of donors 2 with an emphasis on the N⋯S and S⋯S
intermolecular contacts. Hydrogen atoms have been omitted.
solvent from a 1 : 1 MeOH–CH2Cl2 solution. The compound
crystallizes in the monoclinic system, space group P21/c, with
one independent molecule in the unit cell. The conformation
between the TTF and triazole is s-trans when considering the
double bonds C5vC6 and C7vC8, with a very small value of
7.4° for the TTF⋯triazole dihedral angle (Fig. 1). The central
C3vC4 bond measures 1.260(4) Å, in agreement with the
neutral state of the donor.
At the supramolecular level the formation of columns is
observed, in which the donors are shifted with respect to each
other along the longitudinal axis in such a way that a triazole
ring stacks with the TTF unit below, with N⋯S and S⋯S con-
tacts of 3.55 and 3.72 Å, respectively (Fig. 2).
This arrangement is different to that encountered in the
structure of 1, where the formation of head-to-tail dimers was
observed. The columns of 2 further interact laterally along the
c axis through short N⋯S contacts and N⋯Hvinyl hydrogen
bonds of 2.87 and 2.83 Å, respectively (Fig. 3). Thus, the overall
supramolecular architecture results from the interplay of S⋯S,
N⋯S and N⋯H intermolecular interactions. As a general
feature of the TTF-mono(triazole) donors, when comparing the
Fig. 4 Molecular structure of 8 along with the numbering scheme.
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At the supramolecular level there is no short S⋯S inter-
molecular contact, very likely because of the presence of the
bulky benzyl groups on TTF. However, a network of inter-
molecular N⋯H interactions develops, particularly involving
the benzylic protons (see ESI†).
For the use of precursors such as the TTF-bis(triazole) 8 in
electrocrystallization experiments for the preparation of radical
cation salts, the replacement of the benzyl groups by less
bulky substituents, e.g. n-Bu as in 2, can be envisaged in order
to allow the occurrence of TTF⋯TTF intermolecular inter-
actions which are crucial for the establishment of conductivity
paths. It is clear that, when analysing the structures of 1,7
2
and 8, and also the other TTF-triazole derivatives,7 the pres-
ence of the triazole ring on TTF provides additional possibili-
ties for intermolecular interactions such as hydrogen bonding,
π–π stacking and donor–acceptor, and thus results in the emer-
gence of original architectures. Moreover, the unsubstituted
nitrogen atoms can in principle be protonated or alkylated,
which should allow for the modulation of the electron donor
character of TTF, the intra- and intermolecular charge transfer,
and the geometry of the compound.
Fig. 5 UV-vis absorption spectra of 8 (10−4 M in CH2Cl2) during the
stepwise addition of HBF4; the insets magnify the charge transfer band.
basic N atom. When the same type of experiment was per-
formed with the bis(triazole) 8, a first bathochromic shift of
14 nm was observed by adding up to 1 equivalent of HBF4, fol-
lowed by a second shift of 22 nm between 1 and 2 equivalents
of HBF4 (Fig. 5).
In order to isolate and characterize in detail a triazolium
salt, the precursor 1 was reacted with trimethyloxonium tetra-
fluoroborate (Me3O)BF4 to afford 9 (Scheme 4).
Protonation and alkylation studies with 1 and 8
The protonation of the mono(triazole) 1 and bis(triazole) 8,
both possessing benzyl substituents, has been monitored by
UV-vis spectroscopy. As previously described, in the UV-vis
spectra of TTF-triazoles, an absorption band is observed at
around λmax = 388–394 nm, corresponding to a partial charge
transfer from TTF to triazole, as determined by TD DFT calcu-
lations.7 In the bis(triazole) 8, this band is centered at 415 nm
The triazolium salt 9 was obtained as an analytically pure
brown solid, and suitable single crystals, as red blocks, were
grown by the slow diffusion of diethyl ether into a solution of
(Fig. 5), with the red shift with respect to the mono(triazole) 1 9 in acetonitrile. The cyclic voltammetry measurements show
anodic shifts of 0.07 and 0.06 V for the first and second oxi-
dation potentials respectively, when compared to the neutral
being in agreement with a smaller HOMO–LUMO gap when
compared to 1. Since the oxidation of 8 occurs at a more
anodic potential than the oxidation of 1, indicating a lower precursor 1 (see ESI†). In line with the observations from the
protonation experiment, a large red shift of 57 nm in the UV-
vis spectrum is observed for the charge transfer band which is
energy HOMO level for 8 than for 1, it can be concluded that
the variation ΔELUMO is larger than ΔEHOMO when going from
1 to 8. The protonation or alkylation of the triazole ring is now centred at 451 nm (see ESI†).
The final proof for the cationic structure of 9 was provided
by the single crystal X-ray analysis. The compound crystallizes
expected to increase its withdrawing character, and, conse-
quently, result in a red shift of the charge transfer band. The
ˉ
stepwise addition of up to 1 equivalent of HBF4 in a CH2Cl2 in the triclinic system, space group P1, with one independent
TTF-triazolium cation and one BF4 anion in the asymmetric
unit. As clearly observed (Fig. 6), the methylation took place at
solution of 1 indeed leads to a red shift of the charge transfer
band from 394 nm (1) to 422 nm ([1–H]+BF4−), with the exist-
ence of a clear isosbestic point at 416 nm (see ESI†). In the the N3 atom, which is the most nucleophilic. There is now
perfect planarity between the TTF and triazolium units, while
the Ph ring is perpendicular to the rest of the molecule.
The central C3vC4 bond length of 1.351(4) Å is in the
normal range for a neutral donor and compares very well with
same time, practically no variation of the position of the
high energy bands ranging between 250–350 nm is observed.
Further addition of HBF4 produces no further change to
the spectrum, in agreement with the presence of only one
Scheme 4 Alkylation of 1.
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HBF4, monitored by UV-visible spectroscopy. Moreover, a tria-
zolium salt was isolated and structurally characterized by
methylation with the strong electrophilic agent (Me3O)BF4. All
of these TTF-triazoles and derivatives constitute valuable
precursors for radical cation salts since they all possess good
electron donating properties. The coordinating properties of
triazoles can be also exploited, especially when associated to
pyridines within chelating ligands.18 These possibilities are
actively being investigated in our laboratory.
Experimental
General
Dry THF and diethyl ether were obtained from a solvent purifi-
cation system (LC Technology Solutions Incorporated). Nuclear
magnetic resonance spectra were recorded on
a Bruker
Advance DRX 300 spectrometer operating at 300 MHz for 1H
and 75 MHz for 13C. Chemical shifts are expressed in parts per
million (ppm) downfield from external TMS. The following
abbreviations are used: s, singlet; d, doublet; t, triplet; m, mul-
tiplet. MALDI-TOF MS spectra were recorded on a Bruker
Biflex-IIITM apparatus, equipped with a 337 nm N2 laser.
Elemental analyses were recorded using a Flash 2000 Fisher
Scientific Thermo Electron analyzer. IR spectra were recorded
on a Bruker FT-IR Vertex 70 spectrometer equipped with a
platinum diamond ATR accessory.
Fig. 6 Molecular structure of 9 along with the numbering scheme (up)
and a lateral view of the donor molecule (bottom).
the value of 1.350(5) Å in the neutral precursor 1. Nevertheless,
the most important structural effect of the methylation con-
cerns, as expected, the triazole ring, since in 9 the N–N dis-
tances have closer values, i.e. 1.326(4) Å for N1–N2 and 1.306(4)
Å for N2–N3, as an effect of the conjugation, and, moreover,
are shorter than the distances of 1.353(4) and 1.316(4) Å,
respectively, observed in the neutral triazole. In the packing
there is no short intermolecular S⋯S contact (see ESI†), yet
hydrogen bonds of F⋯H-type are established between the BF4
anions and vinylic, benzylic and NMe protons (see ESI†).
The compounds ortho-dimethyl-TTF 319 and ortho-
dimethyl-ethynyl-TTF20 were prepared according to the pub-
lished procedures.
1-Butyl-5-(ortho-dimethyl-tetrathiafulvalenyl)-1,2,3-triazole 2
In
a Schlenk tube, ortho-dimethyl-ethynyl-TTF (120 mg,
0.47 mmol), n-butyl azide (70 mg, 0.71 mmol) and Cp*RuCl-
(PPh3)2 (22 mg, 6 mol%) were dissolved in dry THF (8 mL).
The reaction mixture was heated at 65 °C overnight and con-
centrated under vacuum. The crude product was then purified
by chromatography over SiO2 (CH2Cl2–AcOEt 3 : 1 as the
eluent, Rf = 0.3) to yield 2 as an orange solid (130 mg, 78%).
Suitable single crystals for X-ray analysis were obtained by slow
evaporation of the solvent from a MeOH–CH2Cl2 (1 : 1) solu-
tion of 2.
Conclusions
The synthesis of TTF-bis(triazoles) as 1,4- and 1,5-isomers was
attempted following copper and ruthenium-catalyzed azide–
alkyne cycloaddition reactions, respectively. The access to
these bis(triazole) precursors proved to be much more proble-
matic than the preparation of TTF-mono(triazoles), very likely
because of the sensitivity of the TTF-bis(acetylene) precursor
and the TTF-triazole-acetylene intermediate, since only the
1,5-isomer of the ortho-dimethyl-TTF-bis(triazole) could be
prepared by ruthenium-based catalysis. The same reaction
allowed the preparation of TTF-mono(triazoles) with benzyl or
n-butyl substituents on the triazole ring. The substitution pat-
terns and number of triazole units greatly influences the solid
state structures of these electroactive precursors. As a general
structural feature, the triazole units engage in the solid state
1H NMR (CDCl3 + NEt3, 300 MHz) δ (ppm) 7.70 (s, 1H),
6.44 (s, 1H), 4.42 (t, 2H, J = 7.3 Hz), 1.99 (s, 6H), 1.91 (qt, 2H,
J = 7.3 Hz), 1.37 (sext, 2H, J = 7.3 Hz), 0.98 (t, 3H, J = 7.3 Hz);
{1H}13C NMR (CDCl3 + NEt3, 75 MHz) δ (ppm) 134.2, 129.4,
123.0, 122.9, 121.1, 119.8, 113.2, 106.5, 46.2, 32.13, 19.8, 13.8,
13.5; MS (MALDI-TOF) m/z = 354.7 (M+); Anal. calcd for
C14H17N3S4: C, 47.29; H, 4.82; N, 11.82; S, 36.07%, found:
C, 47.58; H, 4.75; N, 11.44; S, 35.83%.
2,3-Diiodo-6,7-dimethyltetrathiafulvalene 4
in intermolecular π–π interactions and hydrogen bonding, In a Schlenk tube, ortho-dimethyl-TTF 3 (600 mg, 2.58 mmol)
thus competing with the classical TTF⋯TTF interactions. was dissolved in dry diethyl ether (80 mL) under argon at
Modulation of the intramolecular charge transfer, TTF → tria- −78 °C. Diisopropylethylamine (798 µL, 5.68 mmol), followed
zole, was achieved by protonation of the triazole units with by butyllithium (3.55 mL, 5.68 mmol) (1.6 M solution in
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hexane) were then added to the solution. The reaction mixture ortho-Dimethyl-TTF-bis(1-benzyl-1,2,3-triazol-5-yl) 8
was stirred at −78 °C for one hour and a yellow precipitate
In a Schlenk tube, 6 (120 mg, 0.28 mmol), benzyl azide
appeared. Perfluorohexyl iodide (1.45 mL, 6.71 mmol) was
(112 mg, 0.85 mmol) and Cp*RuCl(PPh3)2 (14 mg, 6 mol%)
added and the reaction mixture was allowed to warm up slowly
were dissolved in dry THF (8 mL). The reaction mixture was
to room temperature and was stirred overnight. After evapor-
heated for 24 h at 65 °C and concentrated under vacuum. The
ation of the solvent, the crude product was purified by chrom-
crude product was then purified by chromatography over SiO2
atography over SiO2 (cyclohexane–CS2 1 : 1 as the eluent, Rf =
(CH2Cl2–AcOEt 1 : 1 as the eluent) to yield 8 as a beige solid
0.8), yielding 4 as a light red solid (662 mg, 53%).
(35 mg, 15%). Suitable single crystals for X-ray analysis were
1H NMR (CDCl3 + NEt3, 300 MHz) δ (ppm) 2.00 (s, 6H);
grown by vapour diffusion of pentane onto a CH2Cl2 solution
{1H}13C NMR (CDCl3 + NEt3, 75 MHz) δ (ppm) 128.4, 128.3,
of 8.
122.9, 114.5, 111.4, 77.2, 13.8; MS (MALDI-TOF) m/z = 483.7
1H NMR (CDCl3 + NEt3, 300 MHz) δ (ppm) 7.43–7.37 (m,
(M+); Anal. calcd for C8H6I2S4: C, 19.84; H, 1.25; S, 26.49%,
6H), 7.30–7.26 (m, 4H), 6.54 (s, 2H), 5.41 (s, 4H), 2.08 (s, 6H);
found: C, 20.66; H, 1.30; S, 26.54%.
{1H}13C NMR (CDCl3 + NEt3, 75 MHz) δ (ppm) 134.6, 134.5,
129.0, 128.9, 128.2, 127.2, 123.1, 121.7, 117.7, 65.7, 13.6; MS
2,3-Di(trimethylsilylethynyl)-6,7-dimethyltetrathiafulvalene 5
(MALDI-TOF) m/z = 545.2 (M+); Anal. calcd for C26H22N6S4: C,
In a Schlenk tube, 4 (500 mg, 1.03 mmol), Pd(PPh3)4 (60 mg, 57.12; H, 4.06; N, 15.37; S, 23.46%, found: C, 56.86; H, 4.20;
5 mol%) and CuI (20 mg, 10 mol%) were dissolved in dry THF N, 14.43; S, 21.96%.
(15 mL). Diisopropylamine (871 µL, 6.20 mmol) and trimethyl-
silylacetylene (882 µL, 6.20 mmol) were then added to the solu-
1-Benzyl-3-methyl-5-(6′,7′-dimethyltetrathiafulvalenyl)-
tion. The reaction mixture was heated at 60 °C overnight under
1,2,3-triazolium·BF4 9
argon. After evaporation of the solvent, the crude product was
In a Schlenk tube, 1 (35 mg, 0.09 mmol) was dissolved in a
6 mL mixture of acetonitrile–dichloromethane (1 : 1). Then, tri-
methyloxonium tetrafluoroborate (13.3 mg, 0.09 mmol) dis-
solved in acetonitrile (3 mL) was added and the solution,
which turned darker, was stirred for 1 h at room temperature.
Diethyl ether (10 mL) was added to the reaction mixture, and
the precipitate formed was filtered and washed with cold
dichloromethane and diethyl ether to yield 9 as a brown solid
(31 mg, 77%). Suitable single crystals for X-ray analysis were
grown by the slow diffusion of diethyl ether into an acetonitrile
solution of 9.
purified by chromatography over SiO2 (cyclohexane as the
eluent), yielding 5 as a purple solid (377 mg, 86%). Suitable
single crystals for X-ray analysis were obtained by the recrystal-
lization of 5 in acetonitrile.
1H NMR (CDCl3 + NEt3, 300 MHz) δ (ppm) 1.97 (s, 6H), 0.25
(s, 18H); {1H}13C NMR (CDCl3 + NEt3, 75 MHz) δ (ppm) 125.8,
122.7, 122.0, 114.0, 106.5, 99.7, 94.9, 13.8, −0.29; MS (MALDI-
TOF) m/z = 424.0 (M+); Anal. calcd for C18H24S4Si2: C, 50.89; H,
5.69; S, 30.19%, found: C, 51.21; H, 5.75; S, 30.05%.
2,3-Di(ethynyl)-6,7-dimethyltetrathiafulvalene 6
1H NMR (DMSO, 300 MHz) δ (ppm) 9.19 (s, 1H), 7.48–7.40
(m, 4H), 7.38–7.31 (m, 2H), 5.93 (s, 2H), 4.32 (s, 3H), 1.99
(s, 6H); {1H}13C NMR (DMSO, 75 MHz) δ (ppm) 134.1, 132.5,
132.3, 130.6, 129.6, 129.5, 128.9, 123.5, 113.9, 113.1, 104.7,
55.5, 13.9; MS (MALDI-TOF) m/z = 403.8 (M+); Anal. calcd
for C18H18BF4N3S4: C, 43.99; H, 3.69; N, 8.55; S, 26.10%,
found: C, 44.38; H, 3.96; N, 8.26; S, 25.68%.
To a degassed solution of 5 (150 mg, 0.35 mmol) in THF–
methanol (20 mL, 1 : 1 v/v), tetrabutylammonium fluoride (850
µL, 0.85 mmol) (1 M solution in THF) was added. The reaction
mixture was stirred at RT for 45 min and then the solvents
were removed under vacuum. The crude product was then puri-
fied by flash chromatography over neutral alumina (CH2Cl2 as
the eluent) to yield 6 as a light purple solid (70 mg, 71%)
which was directly engaged in the next step.
1H NMR (CDCl3 + NEt3, 300 MHz) δ (ppm) 3.44 (s, 2H), 2.00 X-Ray structure determination
(s, 6H).
Details of the data collection and solution refinement are
given in Table 1 (see also ESI† for 5). X-ray diffraction measure-
ments were performed on a Bruker Kappa CCD diffractometer,
ortho-Dimethyl-TTF-2′-(N-benzyl-1,2,3-triazol-5-yl)-3′-ethynyl 7
In a Schlenk tube, 6 (70 mg, 0.25 mmol), benzyl azide (90 mg, operating with a Mo Kα (λ = 0.71073 Å) X-ray tube with a graph-
0.75 mmol) and CuI (5.7 mg, 6 mol%) were dissolved in CHCl3 ite monochromator. The structures were solved (SHELXS-97)
(5 mL) and N,N-diisopropylethylamine (3 mL). The reaction by direct methods and refined (SHELXL-97) by full matrix
mixture was heated at 65 °C overnight and concentrated under least-square procedures on F2.21 All of the non-hydrogen atoms
vacuum. The crude product was then purified by chromato- were refined anisotropically. Hydrogen atoms were introduced
graphy over SiO2 (CH2Cl2–AcOEt 3 : 1, and a few drops of at calculated positions (riding model) and included in struc-
NEt3 as the eluent, Rf = 0.4) to yield 7 as an orange solid ture factor calculations, but not refined. Crystallographic data
(10 mg, 10%).
for the four structures have been deposited with the Cam-
1H NMR (CDCl3 + NEt3, 300 MHz) δ (ppm) 8.16 (s, 1H), bridge Crystallographic Data Centre, with the deposition
7.44–7.39 (m, 3H), 7.30 (m, 2H), 5.60 (s, 2H), 3.61 (s, 1H), 1.98 numbers CCDC 982420 (2), CCDC 982421 (5), CCDC 982422
(s, 6H); MS (MALDI-TOF) m/z = 413.2 (M+).
(8) and CCDC 982423 (9).
3172 | Org. Biomol. Chem., 2014, 12, 3167–3174
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Paper
Chem., 2002, 67, 3057; (c) J. E. Hein and V. V. Fokin, Chem.
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Chem. Soc. Rev., 2011, 40, 2848; (b) J. J. Bryant and
U. H. F. Bunz, Chem. - Asian J., 2013, 8, 1354.
Table 1 Crystal data and structure refinement for 2, 8 and 9
Compound
2
8
9
Empirical
formula
fw
C
14H17N3S4
C26H22N6S4
C18H18BF4N3S4
355.55
546.74
491.40
4 D. S. Pedersen and A. Abell, Eur. J. Org. Chem., 2011, 2399.
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Trans., 2007, 1273; (c) M. L. Gower and J. D. Crowley, Dalton
Trans., 2010, 39, 2371; (d) J. D. Crowley and E. L. Gavey,
Dalton Trans., 2010, 39, 4035; (e) H. Struthers, T. L. Mindt
and R. Schibli, Dalton Trans., 2010, 39, 675;
(f) D. Schweinfurth, J. Krzystek, I. Schapiro, S. Demeshko,
J. Klein, J. Telser, A. Ozarowski, C.-Y. Su, F. Meyer,
M. Atanasov, F. Neese and B. Sarkar, Inorg. Chem., 2013, 52,
6880.
6 (a) L. Zhang, X. Chen, P. Xue, H. H. Y. Sun, I. D. Williams,
K. B. Sharpless, V. V. Fokin and G. Jia, J. Am. Chem. Soc.,
2005, 127, 15998; (b) B. C. Boren, S. Narayan,
L. K. Rasmussen, L. Zhang, H. Zhao, Z. Lin, G. Jia and
V. V. Fokin, J. Am. Chem. Soc., 2008, 130, 8923.
T (K)
293(2)
293(2)
293(2)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
b (Å)
c (Å)
α (°)
β (°)
0.71073
Monoclinic
P21/c
0.71073
Orthorhombic
P212121
0.71073
Triclinic
ˉ
P1
5.3381 (5)
6.7025 (5)
19.621 (2)
20.267 (3)
90.00
90.00
90.00
2665.3 (6)
4
1.363
9.7854 (6)
11.173 (7)
11.332 (5)
70.909 (4)
81.108 (4)
68.833 (4)
1090.88 (11)
2
25.844 (19)
11.069 (10)
90.00
99.56 (7)
90.00
1505.9 (2)
4
1.568
γ (°)
V (Å3)
Z
Dc (g cm−3
Abs coeff
)
1.496
0.480
0.626
0.384
(mm−1
)
F(000)
744
0.6 × 0.1 ×
0.1
1136
0.6 × 0.3 × 0.08
504
0.8 × 0.4 × 0.4
Crystal size
(mm3)
θ range for data
collection (°)
Limiting indices −6 ≤ h ≤ 6,
3.15–27.50
2.71–24.03
−7 ≤ h ≤ 7,
2.35–27.00
−12 ≤ h ≤ 12,
−14 ≤ k ≤ 14,
−14 ≤ l ≤ 14
21 173
−33 ≤ k ≤ 32, −22 ≤ k ≤ 21,
7 T. Biet, T. Cauchy and N. Avarvari, Chem. - Eur. J., 2012, 18,
16097.
8 Y.-L. Zhao, W. R. Dichtel, A. Trabolsi, S. Saha,
I. Aprahamian and J. F. Stoddart, J. Am. Chem. Soc., 2008,
130, 11294.
−14 ≤ l ≤ 14
−23 ≤ l ≤ 20
13 973
Reflections
collected
Independent
reflections
Completeness
(%) to θ = 25.59°
Abs correction
Refinement
method
17 019
3380
98.1
4058
4719
98.1
98.9
9 K. Qvortrup, M. Å. Petersen, T. Hassenkam and
M. B. Nielsen, Tetrahedron Lett., 2009, 50, 5613.
Multi-scan
Full-matrix
Multi-scan
Full-matrix least Full-matrix least
Multi-scan
10 B.-T. Zhao, L.-W. Liu, X.-C. Li, G.-R. Qu, E. Belhadj, F. Le
Derf and M. Sallé, Tetrahedron Lett., 2013, 54, 23.
11 (a) D. Lorcy, N. Bellec, M. Fourmigué and N. Avarvari,
Coord. Chem. Rev., 2009, 253, 1398; (b) M. Shatruk and
L. Ray, Dalton Trans., 2010, 39, 11105.
12 (a) E. Coronado and P. Day, Chem. Rev., 2004, 104, 5419;
(b) L. Ouahab and T. Enoki, Eur. J. Inorg. Chem., 2004, 933;
(c) F. Riobé and N. Avarvari, Coord. Chem. Rev., 2010, 254,
1523.
least squares squares on F2
squares on F2
on F2
Data/restraints/
parameters
GOF on F2
Final R indices
[I > 2σ(I)]
R indices
(all data)
3380/0/190
4058/0/325
4719/0/271
1.011
R1 = 0.0579,
wR2 = 0.1453 wR2 = 0.0789
R1 = 0.1176, R1 = 0.0876,
wR2 = 0.1640 wR2 = 0.0923
0.393 and
−0.302
1.125
R1 = 0.0482,
1.132
R1 = 0.0657,
wR2 = 0.2094
R1 = 0.0804,
wR2 = 0.2255
1.328 and
−0.768
Largest diff.
peak and hole
0.196 and
−0.172
(e Å−3
)
13 (a) C. Réthoré, I. Suisse, F. Agbossou-Niedercorn,
E. Guillamón, R. Llusar, M. Fourmigué and N. Avarvari,
Tetrahedron, 2006, 62, 11942; (b) C. Réthoré, F. Riobé,
M. Fourmigué, N. Avarvari, I. Suisse and F. Agbossou-
Niedercorn, Tetrahedron: Asymmetry, 2007, 18, 1877.
14 (a) C. Réthoré, M. Fourmigué and N. Avarvari,
Chem. Commun., 2004, 1384; (b) C. Réthoré, M. Fourmigué
and N. Avarvari, Tetrahedron, 2005, 61, 10935;
(c) A. M. Madalan, C. Réthoré and N. Avarvari, Inorg. Chim.
Acta, 2007, 360, 233.
Acknowledgements
This work was supported by the CNRS, University of Angers
and the Ministry of Education and Research (grant to T.B.).
I. Freuze and C. Mézière are thanked for the MS analyses.
15 (a) W. Liu, J. Xiong, Y. Wang, X.-H. Zhou, R. Wang,
J.-L. Zuo and X.-Z. You, Organometallics, 2009, 28, 755;
(b) M. Nihei, N. Takahashi, H. Nishikawa and H. Oshio,
Dalton Trans., 2011, 40, 2154; (c) G.-N. Li, Y. Liao, T. Jin and
Y.-Z. Li, Inorg. Chem. Commun., 2013, 35, 27.
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