Catechol-appended TTF derivatives

Article abstract of DOI:10.1016/j.tetlet.2013.05.060

EDT-TTF-CONHCatOH, a catechol-appended TTF derivative, 5 was synthesized through a straightforward strategy. The electronic absorption and the electrochemical investigations as well as molecular orbital calculations for compounds 4 and 5 have been performed. The electrochemical measurements of 5 indicate that it is a suitable candidate for the formation of zwitterionic molecular solids and also two-component radical cation salts. The crystal structure of compound 5 reveals supramolecular dimers assembled via a set of O-H?O hydrogen bonds between the catechol and amide units.

Full text of DOI:10.1016/j.tetlet.2013.05.060

Accepted Manuscript
Catechol-appended TTF derivatives
Abdelkrim El-Ghayoury, Antoine Leliège, Magali Allain, Patrick Batail
PII:
S0040-4039(13)00828-9
DOI:
http://dx.doi.org/10.1016/j.tetlet.2013.05.060
TETL 42960
Reference:
To appear in:
Tetrahedron Letters
Received Date:
Revised Date:
Accepted Date:
13 March 2013
6 May 2013
14 May 2013
Please cite this article as: El-Ghayoury, A., Leliège, A., Allain, M., Batail, P., Catechol-appended TTF derivatives,
Tetrahedron Letters (2013), doi: http://dx.doi.org/10.1016/j.tetlet.2013.05.060
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Catechol-appended TTF derivatives
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Abdelkrim El-Ghayoury*, Antoine Leliège, Magali Allain, Patrick Batail*

1
Tetrahedron Letters
journal homepage: www.elsevier.com
Catechol-appended TTF derivatives
Abdelkrim El-Ghayourya*, Antoine Leliègea, Magali Allaina, Patrick Bataila*
a
LUNAM Université, Université d’Angers, CNRS UMR 6200, Laboratoire MOLTECH-Anjou, 2 bd Lavoisier, 49045 Angers Cedex, France
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
EDT-TTF-CONHCatOH, a catechol-appended TTF derivative, 5 was synthesized through a
straightforward strategy. The electronic absorption and the electrochemical investigations as
well as molecular orbital calculations for compounds 4 and 5 have been performed. The
electrochemical measurements of 5 indicate that it is a suitable candidate for the formation of
zwitterionic molecular solids and also two-component radical cation salts. The crystal structure
of compound 5 reveals supramolecular dimers assembled via a set of O–H···O hydrogen bonds
between the catechol and amide units.
Available online
2009 Elsevier Ltd. All rights reserved.
Keywords:
Tetrathiafulvalene; Catechol; Hydrogen bonds;
Electronic absorption; Cyclic voltammetry
Tetrathiafulvalene (TTF) and its many derivatives has been
the subject of numerous studies due to their use as precursors for
molecular conductors and superconductors.1 This is mainly due
to their strong electron donating which results in two sequential
and reversible oxidation processes, affording radical cation
(TTF•+) and dication (TTF2+) species.2 It is well known that
intermolecular interactions play a significant role in controlling
the electronic state, molecular arrangements, and solid-state
physical properties of these crystalline materials. Thus, efforts
have been devoted to direct the intermolecular interactions in
both the neutral, closed-shell molecules as well as in the
corresponding charge transfer complexes and radical cation
salts.3 Among these intermolecular supramolecular interactions,
hydrogen bonds are by far the most utilized ones. Accordingly,
examples of tetrathiafulvalene-based molecules bearing such
functionalities such as alcohols, Me3TTF(CHMeOH),4a
TTF(CH2OH)4,4b EDT-TTF-(CH2OH)n,4c-d thioamides,5 mono-6
and diamides,7 uracil derivatized TTFs,8 adenine-derivatized
In addition, catechols, because of the presence of the two
hydroxyl groups, can act as a hydrogen bond donor molecule and
as anion receptor.15 Surprisingly, only one example of TTF-based
catechol that presents both metal coordinating and hydrogen
bonding abilities has been reported so far.16
Here, we report on the chemistry and electronic properties of
two catechol-appended TTF derivatives namely EDT-TTF-
CONHCat, 4 and EDT-TTF-CONHCatOH, 5 as well as the
crystal structure of the deprotected EDT-TTF-CONHCatOH, 5
and evaluate the structure-directing ability of the amide and the
catechol moieties to form patterns of supramolecular interactions
via the dihydroxyl groups (Figure 1). Because of its dianion is
both a coordinating and hydrogen bond acceptor, TTF-Catechol,
4 is a promising candidate for the preparation of monomolecular
zwitterionic and/or two components molecular conducteurs, as
well as for the preparation of electroactive metal complexes.
TTF,9 the anilinium phosphonate PhNH3 Me3TTF-PO3H– and its
+
zwitterionic, one-electron oxidation product, [Me3TTF-PO3H-
]+.,10 and more recently aminoacid-appended TTF and its
zwitterionic form have been reported.11
Catechol or 1,2-dihydroxybenzene is well known to act as a
aromatic chelating ligand in its semiquinolate or catecholate
dianion forms for a large variety of metal cations.12 For example,
catechols have been used for the preparation of photo and proton
responsive functional metal complexes13 and metallomesogens.14
Figure 1: Multifunctionnal TTF-catechol derivatives
The synthesis protocol for EDT-TTF-CONHCat, 4 involves
the condensation reaction of the EDT-TTF acid chloride
intermediate and the protected aminocatechol. The EDT-TTF
core was chosen because of its well-recognized ability to direct
the formation of layered structures. As shown in Scheme 1, the
carbonate-protected catechol, 3 was prepared by reacting EDT-
TTF acyl chloride, whose synthesis has been previously
___________
* Corresponding authors. Tel.: +33 241735492 (A.E-G.); +33
241735492 (P.B.). fax: + 33 241735405.
E-mail adresses: abdelkrim.elghayoury@univ-angers.fr
patrick.batail@univ-angers.fr.

2
Tetrahedron
described,7a,17 with the protected aminocatechol 2.18 For the
V, Å3
1889.8(3)
1.638
protection of the 4-aminocatechol, the first attempts by the
procedure described by Ogura et al.19 and Cole et al.20 used a
ketone as the protecting group. However the yields of these
methods were very low and the purification of the desired
product proved rather difficult. We have therefore chosen the
carbonate route that consists in the reaction of 4-nitrocatechol
with phosgene using sodium hydroxide as a base to afford the
desired protected catechol 1 in 22 % yield. Although the yield
was low, the easy purification and the recovering of starting 4-
nitrocatechol from the reaction mixture make it a valuable route.
Another advantage of the carbonate protection is that the
deprotection occurs under very mild conditions such as an
aqueous/dioxane media. The hydrogenation reaction of 1 in the
presence of platinum oxide afforded the protected aminocatechol
2 in 92 % yield. The reaction of this protected aminocatechol 2
with EDT-TTF acid chloride gave the protected EDT-TTF-
Catechol 4 in 64 % yield. Refluxing the protected intermediate 4
in a mixture of water and dioxane afforded the desired EDT-
TTF-CONH-CatOH, 5 in 90 % yield.21
ρcalc., g/cm3
μ, cm-1
7.43
Θ
min-max, °
3.70-27.51
20247
4254
Reflections collected
Independent reflections
Rint
0.0571
253
No. of variables
GooF on F2
1.036
Final R [I > 2σ(I)]
0.0625
Compound 5 crystallizes in the monoclinic system, space
group P2/n. The asymmetric unit contains one independent EDT-
TTF-CONH-CatOH molecule 5 in general position and one half
independent crystallization solvent molecule of acetonitrile in
special position on a two-fold axe. Strong EDT-TTF bending is
observed (Figure 2) that is typical for TTF-based molecules in a
neutral state. The dihedral angle between the EDT subunit and
the central C2S4 fragment is close to 12.3°, the inner C=C double
bond length (d = 1.324(6) Å) and the C-S bonds amounting 1.76
Å within their TTF cores confirm the neutral state of the
molecule. Note that the TTF core and the amido-catechol unit are
almost parallel with a dihedral angle close to 5°.
Scheme 1: Synthesis of EDT-TTFCONH-CatOH, 5. Reagents
and conditions: (a) Phosgene, NaOH, Benzene, 22 %; (b)
H2/PtO2, AcOEt, 92 %; (c) THF, NEt3, 64 %; d) H2O/1,4-
dioxane, reflux, 90 %.
Figure 2. Side view of 5 showing the bent TTF molecule.
Compound 5 was obtained as single crystals and a complete
analysis of its structure has been carried out based on X-ray
diffraction data (Table 1). X-ray single-crystal diffraction data
were collected at 293K on a BRUKER-NONIUS KappaCCD
diffractometer, equipped with a graphite monochromator utilizing
MoKα radiation (λ = 0.71073Å). The structure was solved by
direct methods and refined on F2 by full-matrix least-squares
method, using SHELX97 package.22 Non-hydrogen atoms were
refined anisotropically and absorption was corrected by
SADABS program.23 The 3 H atoms on heteroatoms were found
by Fourier difference synthesis and all the other ones on carbon
atoms were included at calculated positions without refinement.
Intramolecular O–H···O hydrogen bonding within the catechol
group with a distance of 2.31(5) Å forces the other hydrogen to
be directed to the opposite direction. The latter interacts with an
oxygen atom from the amide group of the neighbouring molecule
by a strong O–H···Oamide bond (1.83 Å and d(OcatOH···Oamide) =
2.65 Å) resulting in the formation of dimers that are formed with
2
a rare R2 (16) motif (Figure 3). Additional weaker hydrogen
contacts (2.436(4) and 2.449(4) Å) occur between the two
oxygen atoms of the catechol and hydrogen atoms of two
neighbouring Csp2 of TTF molecules.
Table 1. Room temperature crystal data, data collection and
refinement details for EDT-TTF-CatOH, 5.
Chemical formula
Formula weight
Crystal system
Space group, Z
а, Å
C32H25N3O6S12
932.27
Monoclinic
P 2/n,
16.0614(6)
Figure 3: Pattern of intermolecular contacts in 5. Two
b, Å
5.7179(5)
20.830(2)
98.930(5)
molecules are linked by pairs of strong O–H···O hydrogen bonds
c, Å
2
forming R2 (16) cyclic motifs which interact through S···S
contacts to form double chains.
β, °

3
The dimers form a stack along b-axis and interact with
adjacent dimers through S...S contacts (d(S...S) being between
3.589(2) and 3.990(2) Å) to form a double chain arrangement of
the TTF-catechol molecules. Along the b-axis, the molecules
stack with an interplanar distance between the TTF core of 3.59
Å and are shifted from one to another with a distance of 4.08 Å.
In the a-direction, the columns of stacked parallel molecules are
alternating with a quasi perpendicular angle of rotation of 86.8°
(Figure 4).
eV) as compared with 5 (ΔE = 3.62 eV) and this is in
accordance with the batochromic shift in the electronic
absorption observed for 4 (λ = 410 nm) compared with 5 (λ =
388 nm).
HOMO -4.97 eV
HOMO -5.18 eV
LUMO -1.35 eV
LUMO -1.77 eV
EDT-TTF-CONH-Cat (4) EDT-TTF-CONH-CatOH (5)
Figure 6. HOMO-LUMO frontiers orbitals of the carbonate 4
and catechol 5.
Cyclic voltammetry experiments were performed in order to
evaluate the oxidation potentials of the new donor molecules.
The corresponding half-wave potentials for the two compounds
along with those of EDT-TTF for comparison are listed in Table
2. Compounds 4 and 5 oxidize reversibly at about the same
potential without any substantial difference between the protected
and the non protected diol. Compared with that of EDT-TTF, the
first oxidation potential is anodically shifted by approximatively
100 mV, as in the case of EDT-TTF-Amides confirming the
electron withdrawing effect of the amido group. These results
indicate that the two derivatives are capable, upon
electrochemical oxidation, to form stable radical cation salts. The
non-protected catechol derivative, because of the ionisable
dihydroxy groups, is able in combination with a templating bases
with various pH activities to form mono-component systems
(neutral zwitterionic solids) and/or two-component radical cation
salts. The use of bases with different pH activities such as
fumarates, bipyridines or sulphates are under investigation in
order to prepare such molecular solids.
Figure 4: Packing diagram of
perpendicular orientation of the columns of parallel molecules.
CH3CN and H are omitted for clarity.
5 showing the quasi
Table 2. Oxidation potentials (V vs SCE) for 4, 5 and for
EDT-TTF reference compound. C = 10-3 Mol.L-1 in CH2Cl2,
υ=100mV.S-1, Bu4NPF6 (10-1 mol.L-1).
Figure 5: Electronic absorption spectra of the two TTF
derivatives, 4 and 5 in dichloromethane (c = 5*10-5 mol.L-1).
1
2
Compound
E1/2
E1/2
The two TTF derivatives, carbonate 4 and catechol 5, exhibit
electronic absorption spectra with similar shapes (Figure 5). A
strong absorption band (extinction coefficient ε ≈ 1.4*104
EDT-TTF
0,015
0,12
0,11
0,20
0,45
0,44
4
5
dm3mol–1cm–1) at high energy (λ
=286 nm) and a moderate
max
absorption band in the region 380–500 nm.
Frontier orbitals (Figure 6) demonstrate that most of the
electron density of the HOMO is located on the TTF fragment,
while the LUMO is distributed over the benzene–amide–dithiol
ensemble with a larger contribution of the benzene ring in the
case of compound 4 because of the presence of the carbonate
group (an accepting group as compared with donating dihydroxy
from the catechol 5).16 Note that the difference in the HOMO–
LUMO energies is lower in the case of compound 4 (ΔE = 3.42
In
conclusion,
we
have
successfully
appended
tetrathiafulvalene cores with a catechol unit. These derivatives
are valuable ligands for the synthesis of electroactive metal

4
Tetrahedron
complexes as well as neutral zwitterionic solids and two
component radical cation salts.
18. In a three-necked flask, under nitrogen atmosphere, amino-carbonate
(0.05 g; 0.33 mmol) was dissolved in 10 mL of freshly distilled
tetrahydrofurane (THF) and mL of triethylamine was added.
solution of ethylenedithiotetrathiafulvaleneacidchloride (0.13 g,
1
Acknowledgments
A
0.36 mmol) in 10 mL of tetrahydrofuran was added dropwise. The
mixture was stirred, at room temperature, during 15 hours and THF
was distilled under vacuum. The resulting mixture was then
extracted from water using dichloromethane (3*75mL). The organic
phases were collected, dried over sodium sulfate and evaporated
under vacuum to afford an orange red solid. Yield (0.10 g, 64 %).
Prof. P. Leriche is acknowledged for his help regarding
calculations. Dr. D. Branzea is acknowledged for fruitful
discussion
Supplementary Material
λ
max(DCM)/nm 286 (ε/dm3 mol-1 cm-1 14000), 410 (1650). δH (300
MHz, DMSO), 10.49 (s, 1H, NH), 7.85 (s, 1H, CH=C, TTF), 7.79
(d, J=2.1Hz, 1H, CH, benzene), 7.45 (d, J=8.8Hz, 1H, CH, benzene),
7.40 (dd, J=2.1Hz, J=8.8Hz, 1H, CH, benzene); 3.40 (s, 4H, CH2).
δC (75 MHz, DMSO), δ 157.3 (N-C=O), 151.0 ((O)2C=O), 142.7
Crystallographic data for the structural analysis have been
deposited with the Cambridge Crystallographic Data Centre,
CCDC 928761 for compound 5.
(C=CBenzene), 139.1(C=CBenzene),
134.8
(C=CBenzene),
133.0
(C=C(TTF)), 127.1 (C=C(TTF)), 116.3 (C=C(TTF)). 115.4
(C=CBenzene), 113.0-112.7 (C=C(TTF)), 110.2 (C=CBenzene), 104.3
(C=CBenzene), 103.1 (C=C(TTF)), 29.5 (CH2-CH2). Elemental
analysis (%) calcd for C16H9NO4S6: C 40.75, H 1.92, N 2.97; found:
C 41.46, H 2.57, N 3.44. MALDI-TOF MS calcd : m/z = 470.9 Da,
found: m/z 470.9 [M]+, 516,9 (M++2Na).
References and notes
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A
solution
of
4
4,5-éthylènedithio-tétrathiafulvalène-1-
(0.1 g; 0,2mmol) in mixture of
amidobenzocarbonate
a
water/dioxane 30 mL (1/1, v/v) was refluxed for one hour.
Dichloromethane 200 ml was added to the reaction mixture for
extraction. The organic layer was dried, filtered off and the solvent
evaporated under vacuum to yield EDT-TTF-CONH-CatOH, 5 (0.08
g, 90 %) as an orange powder. Recrystallisation from ethyl acetate
afforded orange single crystals that were suitable for X-ray structure
determination. λmax(DCM)/nm 286 (ε/dm3 mol-1 cm-1 15200), 388
(2250). δH (300 MHz, DMSO), 9.96 (s, 1H, NH), 9.01 (s, 1H, OH),
8.72 (s, 1H, OH), 7.73 (s, 1H, CH=C, TTF), 7.10 (d, J=2.5Hz, 1H,
CH, benzene), 6.82 (dd, J1=2,5Hz, J2=8,6Hz, 1H, CH, benzene), 6.65
(d, J=8.6HZ, 1H, CH, benzene), 3.40 (s, 4H, CH2(7,8)). δC (75 MHz,
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m/z 444.6 [M].
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