Tetrathiafulvalene-hydroxyamides and -oxazolines: Hydrogen bonding, chirality, and a radical cation salt

Article abstract of DOI:10.1016/j.tet.2005.08.104

Racemic and enantiopure ethylenedithio-tetrathiafulvalene (EDT-TTF) derivatives featuring β-hydroxyamide or oxazoline (OX) groups bearing methyl or isopropyl substituents have been synthesized starting from the corresponding amino alcohols. Crystal structure analysis shows in the case of the racemic methyl-β-hydroxyamide donor the development of a unique hydrogen bond network, characterized by short CO?H-O and N-H?O-H intermolecular distances. The enantiopure (S)-EDT-TTF-methyl-OX crystallizes in the monoclinic non-centrosymmetric space group P2₁, whereas the isopropyl counterparts, (R)-and (S)-EDT-TTF-isopropyl-OX, crystallize in the orthorhombic non-centrosymmetric space group P2₁2₁2 ₁. All of them adopt a s-trans conformation in which TTF and oxazoline units are coplanar. Electrocrystallization experiments with the racemic EDT-TTF-methyl-OX, in the presence of (nBu₄) ₂Mo₆Cl₁₄ as supporting electrolyte, afford a radical cation salt, formulated as [(±)-EDT-TTF-methyl-OX] ₂Mo₆Cl₁₄, in which the donors associate in strong dimers, which further stack along the b direction to form quasi-homochiral helix-like ribbons.

Full text of DOI:10.1016/j.tet.2005.08.104

Tetrahedron 61 (2005) 10935–10942
Tetrathiafulvalene-hydroxyamides and -oxazolines: hydrogen
bonding, chirality, and a radical cation salt
*
´
Celine Rethore, Marc Fourmigue and Narcis Avarvari
*
´
´
´
´ ´ ´ ´ ˆ
Laboratoire de Chimie, Ingenierie Moleculaire et Materiaux d’Angers, UMR 6200, Universite d’Angers, UFR Sciences, Bat. K, 2 Bd.
Lavoisier, 49045 Angers Cedex, France
Received 20 July 2005; revised 25 August 2005; accepted 30 August 2005
Available online 19 September 2005
Abstract—Racemic and enantiopure ethylenedithio-tetrathiafulvalene (EDT-TTF) derivatives featuring b-hydroxyamide or oxazoline (OX)
groups bearing methyl or isopropyl substituents have been synthesized starting from the corresponding amino alcohols. Crystal structure
analysis shows in the case of the racemic methyl-b-hydroxyamide donor the development of a unique hydrogen bond network, characterized
by short C]O/H–O and N–H/O–H intermolecular distances. The enantiopure (S)-EDT-TTF-methyl-OX crystallizes in the monoclinic
non-centrosymmetric space group P21, whereas the isopropyl counterparts, (R)-and (S)-EDT-TTF-isopropyl-OX, crystallize in the
orthorhombic non-centrosymmetric space group P212121. All of them adopt a s-trans conformation in which TTF and oxazoline units are
coplanar. Electrocrystallization experiments with the racemic EDT-TTF-methyl-OX, in the presence of (nBu4)2Mo6Cl14 as supporting
electrolyte, afford a radical cation salt, formulated as [(G)-EDT-TTF-methyl-OX]2Mo6Cl14, in which the donors associate in strong dimers,
which further stack along the b direction to form quasi-homochiral helix-like ribbons.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
structures may accommodate the enantiomers exchanging
places. It is well established that structural disorder can
strongly influence the electronic conductivity in molecular
conductors,5 therefore the chirality can already play a
paramount role at this level. A straightforward strategy to
introduce chirality within TTF based materials lies in the
utilization of chiral TTF’s as precursors for radical cation
salts, although the complementary strategy, consisting of
the use of chiral counter-ions with achiral donors can be
envisioned, as recently described in the BEDT-TTF (bis-
ethylenedithio-tetrathiafulvalene) salt with the chiral anti-
mony (L)-tartrate dimer, [Sb2(L-tart)2]2K.6 The advantage
of the former strategy, despite more synthetically-demand-
ing efforts than for the second one, is that, once the synthesis
of a chiral donor optimized, a large panel of anions, be they
chiral or achiral, can be explored.
The introduction of chirality within conducting molecular
materials based on tetrathiafulvalene (TTF) derivatives, a
well known class of organosulfur electron donors exten-
sively studied in the search for molecular conductors and
superconductors,1 currently receives a growing interest, also
encouraged by Rikken et al.’s recent report of electrical
magnetochiral anisotropy in chiral carbon nanotubes.2 This
feature is in line with the quest for multifunctional
molecular materials, a trend of much interest in con-
temporary materials science, aiming at combining in the
solid state at least two physical properties, such as
conductivity and optical activity.3 The question of whether
the chirality influences the electrical properties of TTF
based radical cation salts had been previously addressed by
Dunitz and others, but the lack of suitable enantiopure
materials together with their racemic form did not allow
deeper investigations.4 Yet, structural differences between
racemic and enantiomeric forms may occur, since enantio-
pure radical cation salts are expected to suffer less from
structural disorder than the racemates, whose crystal
The first examples of enantiopure TTF derivatives were
described by Dunitz and Wallis,7 and since then other chiral
TTF’s were synthesized, most of them featuring a
functionalized BEDT-TTF skeleton.8 The latter, along
with closely related donors, have been recently extensively
Keywords: Tetrathiafulvalenes; Chirality; Oxazolines; Crystalline struc-
tures; Electrocrystallization; Radical cation salts.
*
Corresponding authors. Tel.: C33 2 41 73 50 84; fax: C33 2 41 73 54 05;
e-mail addresses: marc.fourmigue@univ-angers.fr;
narcis.avarvari@univ-angers.fr
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.08.104

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C. Rethore et al. / Tetrahedron 61 (2005) 10935–10942
10936
surveyed by Wallis et al.4 Moreover, enantiopure TTF
derivatives containing chiral binaphthyl frameworks9 or
oxazoline rings10 were also synthesized. The latter were
tested as ligands in the catalytic allylic substitution reaction,
showing though a rather modest catalytic activity.
(G) or enantiopure (R) and (S) amino alcohols, namely
alaninol and valinol, were reacted with 1, and, after stirring
at room temperature for up to 12 h and chromatographic
work up, the corresponding EDT-TTF-b-hydroxyamides
2a–c and 3a–c were isolated and characterized by spectro-
scopic methods and elemental analysis (Scheme 1). An
X-ray crystal structure analysis was undertaken for
compound 2a (vide infra). Note these are the first examples
of TTF’s bearing both amide and alcohol functional groups,
whereas numerous homofunctional derivatives of either
amide,13,14 thioamide15 or alcohol16 type were described so
far. Subsequently, cyclization reactions in the presence of
methanesulfonyl chloride (MsCl) and triethylamine were
performed on b-hydroxyamides to yield the series 4a–c
(methyl) and 5a–c (isopropyl) of (G), (R) and (S) EDT-
TTF-oxazolines (EDT-TTF-OX). All analytical data and
elemental analyses are in good agreement with the proposed
structures. Suitable single crystals for X-ray analysis were
obtained for the enantiopure donors 4c, 5b and 5c.
In a recent communication we briefly described the
straightforward synthesis of EDT-TTF (ethylenedithio-
tetrathiafulvalene) substituted with a chiral 4-methyl-
oxazoline and a diphenylphosphino group.11 The chirality
provided by the oxazoline ring is perfectly controlled and
easily introduced in the synthesis by the use of racemic or
enantiopure amino alcohols. By synthesizing the EDT-TTF-
Me-Oxazolines (EDT-TTF-OX), our purpose was to access
a class of chiral donors, which could serve as precursors for
chiral molecular materials. Indeed, this strategy proved to
be highly promising for future developments, since we
succeeded in preparing the first complete series of mixed-
valence metallic salts based on chiral tetrathiafulvalenes
bearing the (R)-, (S)-, or racemic (G)-methyl-oxazoline
heterocycle and the AsFK6 monoanion. The single crystal
conductivity for the enantiopure salts was one order of
magnitude higher than that of the racemic one, very likely
because of the structural disorder observed in the latter.12 In
the present paper, we describe the detailed synthesis and
characterization of chiral EDT-TTF-b-hydroxyamides and
-oxazolines, in methyl and isopropyl series, in their racemic
and (R) and (S) enantiopure forms. In depth analyses of
crystal structures of racemic Me-hydroxyamide, enantio-
pure (S)-Me-oxazoline and (R) and (S)-iPr-oxazolines are
2.2. X-ray crystal structures of donors
Suitable single crystals for the b-hydroxyamide 2a were
obtained upon recrystallization in ethyl acetate. The donor
crystallizes in the monoclinic system, space group P21/c,
with one independent molecule in the unit cell. As expected
for a racemic mixture, both enantiomers, related to each
other through the inversion center, are present in the
structure. Selected bond lengths are listed in Table 1.
presented, along with that of a radical cation salt of racemic
EDT-TTF-Me-oxazoline with the Mo6Cl anion, obtained
upon electrocrystallization.
All values are typical for a neutral TTF, which, in this case,
is moderately folded along both S/S hinges, that is,
15.33(18)8 for S1/S2 and 19.9(3)8 for S3/S4, as often
encountered within crystalline structures of such neutral
donors. The amide group is coplanar with the TTF unit, and
disposed in an antiparallel manner with respect to C7]C8
and C9]O1 double bonds, as evidenced in Figure 1.
Certainly, the most peculiar feature in the crystalline
structure of 2a is the hydrogen bond network established
thanks to amide and alcohol groups. As observed for another
b-hydroxyamide,17 both functionalities participate as
hydrogen bond donor and acceptor groups, with the
carbonyl oxygen atom O1 acting as acceptor towards the
alcoholic proton H2 and the amidic proton H1 as donor
towards the alcoholic oxygen atom O2. The consequence of
the balance between these requirements and the typical
intermolecular S/S van der Waals contacts and stacking
tendency of TTF type derivatives, is the organization of the
donors in infinite ladders along a, through two types of
hydrogen bond motifs (Fig. 1). Indeed, according to M.
Etter’s nomenclature,18 one can identify R22(14) and R22(10)
rings, characterized by short and rather linear hydrogen
bonds of C]O/H–O and N–H/O–H type, respectively.
2K
14
2. Results and discussion
In order to introduce a chirality center on the oxazoline ring,
our first choice to use a methyl substituent was motivated by
the concern to have a minimum steric bulk, provided by the
redox inert oxazoline part of the donor, in the radical cation
salts of EDT-TTF-OX. This feature would favor a
maximization of p–p overlap and van der Waals
intermolecular interactions in the solid state. Secondly, in
a parallel series of donors, an isopropyl substituent was used
instead of methyl, in order to gain in solubility, but also to
insure a steric protection for potential catalytic applications.
2.1. Synthesis
It is well established that EDT-TTF-COCl (1) smoothly
reacts with primary amines to afford in good yields
secondary amides.13 Paralleling this strategy, two racemic
Scheme 1. Reagents and conditions: (i) (G), (R) or (S)-alaninol for 2a–c and valinol for 3a–c, NEt3, THF, 12 h, rt; (ii) NEt3, THF, MsCl at 0 8C, then 20 h at
50 8C.

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C. Rethore et al. / Tetrahedron 61 (2005) 10935–10942
10937
˚
Table 1. Selected bond lengths (A) and torsion dihedral angles (8) for 2a, 4c, 5b, 5c and (4a)2Mo6Cl14
2a
4c
5b
5c
(4a)2Mo6Cl14
˚
Bond lengths (A)
1.317(9)
C3–C4
C5–C6
C7–C8
C7–C9
C17–C18
C5–S4
C5–S3
C6–S2
C6–S1
1.322(11)
1.339(8)
1.337(10)
1.500(10)
1.336(5)
1.339(4)
1.333(5)
1.449(5)
1.314(8)
1.332(7)
1.322(10)
1.468(13)
1.338(8)
1.398(7)
1.330(8)
1.454(8)
1.393(8)
1.723(5)
1.716(5)
1.732(5)
1.712(5)
1.335(8)
1.342(12)
1.448(14)
1.752(7)
1.761(7)
1.761(7)
1.751(7)
1.756(3)
1.748(3)
1.753(3)
1.763(3)
1.749(7)
1.760(7)
1.743(7)
1.760(7)
1.753(7)
1.766(6)
1.731(6)
1.761(6)
Torsion angles (8)
S1/S2
S3/S4
15.33(18)
19.9(3)
5.8(2)
3.1(2)
13.5(3)
21.6(5)
14.6(3)
21.0(5)
0.43(9)
3.95(9)
S7/S8
S9/S10
2.73(6)
2.56(13)
Oxazoline/TTF (s-trans)
Oxazoline/TTF (s-trans)
oxazoline/TTF (s-cis)
7.3(5)
8.7(6)
10.1(7)
3.9(2) (N1)
15.3(4) (N2A)
18.6(5) (N2B)
Furthermore, the donors stack along b, with the shortest S/
were obtained upon recrystallization in a THF/cyclohexane
1:1 mixture. Like its enantiomeric counterpart 4b, the
oxazoline 4c crystallized in the monoclinic non-centrosym-
metric space group P21, with one independent molecule in
the unit cell. Note the s-trans conformation (Fig. 2) of the
donor, with bond lengths in the typical range for a neutral
TTF and only slight folding about S/S hinges. TTF and
oxazoline units are coplanar, with the corresponding
dihedral angle amounting at 7.3(5)8, an important feature
in view of obtaining radical cation salts based on EDT-TTF-
Me-OX 4a–c.
˚
S intermolecular distance amounting at 3.58 A. Clearly, the
presence of amide and alcohol groups within the same donor
allows original hydrogen bond supramolecular patterns in
the TTF series, with respect to homofunctional derivatives,
whose crystalline structures have been recently extensively
reviewed.19
The donors 4c stack along the b direction, leading to a
herring bone type packing (Fig. 3), which is the mirror
image of the 4b packing.
In the case of oxazoline derivatives 4 and 5, two planar
conformations are possible, namely s-cis and s-trans, if one
considers the mutual orientations of the C7]C8 and C9]N
double bonds. In the crystalline structure of 4b, previously
published,11 the conformation was s-trans, with TTF and
oxazoline units lying in the same plane. Single crystals of 4c
Furthermore, formation of isopropyl-oxazolines 5a–c was
also confirmed by X-ray diffraction analyses, on single
crystals obtained upon slow evaporation of a ethyl acetate
solution, for both enantiomers R (5b) and S (5c). They are
isostructural and crystallized in the non-centrosymmetric
orthorhombic space group P212121, with one independent
molecule in the unit cell. As represented in Figure 4, 5b and
5c are the images each other in a mirror plane, and, like their
methyl analogue 4c, adopt a quasi-planar s-trans confor-
mation, with torsion angles TTF/oxazoline amounting at
8.7(6) and 10.1(7)8, respectively. Geometrical parameters
(Table 1) are in the expected range.
Interestingly, the packing of 5b and 5c is completely
different when compared with 4b, since in these cases the
Figure 1. Hydrogen bond network in the crystalline structure of 2a.
Hydrogen atoms at C11 and C12 have been omitted for clarity.
˚
Intermolecular distances (A) and angles (8): O1/O2A (Kx, 1Ky, Kz)
2.62, O1/H2A 1.96, O1–H2A–O2A 137.0 for R22(14) ring; N1/O2B
(K1Kx, 1Ky, Kz) 2.82, H1/O2B 1.99, N1–H1–O2B 160.0 for R22(10)
ring.
Figure 2. ORTEP view of (S)-EDT-TTF-OX 4c (thermal ellipsoids set at
50% probability).

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C. Rethore et al. / Tetrahedron 61 (2005) 10935–10942
10938
reversibility of the processes. The corresponding half-wave
potentials for all the compounds are listed in Table 2.
Both mono-electronic oxidations are fully reversible, with
potential values very similar to that of EDT-TTF-amides
(0.66 and 0.92 V vs SCE for E11/2 and E21/2, respectively).13
As already mentioned (vide supra),12 we recently described
a first complete series of mixed-valence metallic salts
obtained upon electrocrystallization of the donors 4a–c with
the AsFK6 monoanion. This time the (TBA)2Mo6Cl14
dianionic salt was used as supporting electrolyte in a series
of electrocrystallization experiments with the same 4a–c
donors. Unlike the case of the AsFK6 monoanion, with the
2K
14
Mo6Cl
dianion only the racemic TTF-OX 4a afforded
suitable single crystals for X-ray analysis, of a salt
formulated as (4a)2Mo6Cl14, whereas crystalline plates of
poor quality were obtained for the enantiopure 4b and 4c.
Table 2. Oxidation potentials (V vs SCE, nBu4NPF6, 0.1 M in CH2Cl2 at
0.1 VsK1, at 20 8C)
E11/2
E12/2
Figure 3. Packing diagram of 4c.
2a–c
3a–c
4a–c
5a–c
0.60
0.60
0.63
0.63
1.09
1.09
1.11
1.11
2.4. Crystal structure of (4a)2Mo6Cl14
The salt crystallizes in the monoclinic system, space group
P21/c, with two independent donor molecules in general
positions and two half-clusters located on inversion centers
in the unit cell. According to the stoichiometry within the
salt, both donor molecules are oxidized into radical cations,
which is also confirmed by the variation of C]C and C–S
central bonds, that is, elongation for C5]C6 and C17]C18
and shortening for C–S when compared to neutral donors
(Table 1). As expected for fully oxidized donors the TTF
units are practically planar, with folding angles about S/S
hinges close to 08. Interestingly, one donor (OX1) adopts a
s-trans conformation, being coplanar with the TTF core,
whereas the other (OX2) is disordered on two positions,
corresponding to both R (0.75) and S (0.25) enantiomers on
the same site, the first as s-trans and the second as s-cis
conformers, with moderate TTF/oxazoline dihedral angles
(Fig. 6 and Table 1).
Figure 4. View of the two enantiomers 5b and 5c.
donors arrange in pairs, almost perpendicular to each other
along b, as observed in Figure 5.
2.3. Redox properties of donors
In order to evaluate the redox properties of the donors
synthesized so far we have performed cyclic voltammetry
experiments to determine the oxidation potentials and the
There is no organic–inorganic segregation within the
2K
structure, but rather Mo6Cl
dianions wrapped in helix-
14
like ribbons of donors developing along b (Fig. 7).
Interestingly, the ribbons are homochiral if we consider
only the major enantiomer (sofZ0.75) in the case of OX2.
As often observed in the case of fully oxidized TTF-based
donors, the radical cations strongly dimerize within the
ribbons, in a ‘head-to-tail’ conformation, to form dicationic
[(4a)2]2C species.
The dimerization occurs between the two independent
donor molecules OX1 and OX2 and within this dyad there
˚
are intermolecular S/S contacts as short as 3.37–3.45 A,
with a bHOMO–HOMO interaction energy overlap, calculated
by the extended Hu¨ckel method, amounting at 0.86 eV
(interaction I). Longer intra-ribbon S/S contacts, in the
Figure 5. Packing diagram of 5c.

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C. Rethore et al. / Tetrahedron 61 (2005) 10935–10942
10939
synthesized. X-ray crystal structure of the racemic methyl-
b-hydroxyamide, with an emphasis on the hydrogen bond
network in which both amide and alcohol groups are
involved, is described. The hydrogen bond donor and
acceptor requirements are entirely fulfilled by the establish-
ment of C]O/H–O and N–H/O–H intermolecular
interactions. Furthermore, X-ray structures of enantiopure
S-methyl and R- and S-isopropyl oxazolines, which crystal-
lized in non-centrosymmetric space groups, are analyzed. A
radical cation salt involving the racemic EDT-TTF-methyl-
2K
14
oxazoline and the Mo6Cl
anion was synthesized. Its
crystalline structure shows association of radical cations in
dimers, characterized by a high energy overlap interaction,
and formation of quasi-homochiral ribbons out of donor
molecules. The use of these electroactive b-hydroxyamides
and oxazolines as precursors for chiral molecular materials
is currently being investigated.
4. Experimental
Figure 6. View of the two independent donor radical cations in the structure
of (4a)2Mo6Cl14. The bottom molecule corresponds to the disordered
enantiomers on the same site, with the S one, in a s-cis conformation,
having darkened bonds and the methyl carbon atom C24B in black.
Hydrogen atoms have been omitted for clarity.
4.1. General comments
Dry CH2Cl2 was obtained by distillation over P2O5 and THF
was distilled over sodium and benzophenone. Nuclear
magnetic resonance spectra were recorded on a Bruker
Avance DRX 500 spectrometer operating at 500.04 MHz
1
for H, 125.75 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, multiplet; b, broad. MALDI-TOF MS spectra
were recorded on Bruker Biflex-IIITM apparatus, equipped
with a 337 nm N2 laser. Elemental analyses were
performed by the ‘Service d’Analyse du CNRS’ at Gif/
Yvette, France.
4.2. General procedure for b-hydroxy amides
In anhydrous THF (10 mL) 0.2 mL of the appropriate
aminoalcohol (2.46 mmol) was diluted, and then 0.55 mL of
dry triethylamine (3.95 mmol) was added. The colorless
solution thus obtained was stirred for 10 min under N2
before dropwise addition of a solution of freshly prepared
ethylenedithio-tetrathiafulvalene carbonyl chloride (1)
(0.700 g, 1.96 mmol) in 30 mL dry THF. The orange
resulting solution was stirred for 6–12 h at room tempera-
ture. Then the mixture was filtered through a pad of Celitew
and concentrated under reduced pressure. The crude product
was chromatographed through silica gel, with THF as
eluent, to give the hydroxy-amides as orange-red solids.
Figure 7. Mixed organic-inorganic slabs in the structure of (4a)2Mo6Cl14
.
Hydrogen atoms and oxazoline rings have been omitted for clarity.
Calculated bHOMO–HOMO interaction energies are as follows: interaction I
OX1/OX2 (Kx, Ky, 1Kz) 0.86 eV, interaction II OX1/OX2 (x, 0.5Ky,
0.5Cz) 0.15 eV.
˚
range of 3.6–3.8 A, are observed between the dyads, with a
much weaker interaction of only 0.15 eV (interaction II).
˚
Inter-ribbons S/S distances are over 4 A, quite larger than
the sum of van der Waals radii of two sulfur atoms.20 The
strong structural and energetic dimerization observed herein
would, very likely, lead to an insulating behavior. Yet, the
preparation of this radical cation salt demonstrates once
again that the new class of donors is suitable for the
synthesis of racemic or enantiopure molecular materials.
4.2.1. 2-(C/K)-N-(1-Hydroxy-propyl)-ethylenedithio-
tetrathiafulvalene-amide (2a). From (C/K)-alaninol
(0.19 g), orange solid (0.57 g, 73% yield), mp 166–
167 8C. 1H NMR (CDCl3): d 1.24 (d, 3JZ6.8 Hz, 3H,
2
CH3), 3.30 (s, 4H, S–CH2–CH2–S), 3.59 (dd, JZ11.0 Hz,
3JZ5.4 Hz, 1H of CH2O), 3.72 (dd, 3JZ11.0 Hz, 2JZ
3.7 Hz, 1H of CH2O), 4.14 (m, 1H, NH–CH–CH2O), 5.76
(d, 3JZ7.0 Hz, 1H, NH), 7.11 (s, 1H, ]CH). IR (KBr, cmK
1): 1571 (nC]C), 1615 (nC]O), 3186 (nOH). m/z (MALDI-
TOF): 395.08 (MC). Anal. Calcd for C12H13NO2S6: C,
36.43; H, 3.31; N, 3.54. Found: C, 36.53; H, 3.35; N, 3.42.
3. Conclusions
Two series of racemic and enantiopure EDT-TTF-b-
hydroxyamides
and
EDT-TTF-oxazolines
were

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4.2.2. 2-(R)-N-(1-Hydroxy-propyl)-ethylenedithio-tetra-
thiafulvalene-amide (2b). From (R)-alaninol (0.32 g, air
sensitive) and 1.2 g of EDT-TTF-COCl, red solid (0.84 g,
formed mesylate disappeared, as monitored by TLC:
AcOEt/cyclohexane 2:1. Then the mixture was filtered
through a pad of Celitew and concentrated under reduced
pressure. The crude product was chromatographed on silica
gel (AcOEt/cyclohexane 2:1) to give a yellow-orange solid.
Recrystallization in acetonitrile (or a mixture of THF and
cyclohexane) affords orange crystalline solids.
1
63% yield), mp 148–150 8C. H NMR (CDCl3): d 1.24 (d,
3JZ6.8 Hz, 3H, CH3), 3.30 (s, 4H, S–CH2–CH2–S), 3.60
(dd, 3JZ11.0 Hz, 2JZ5.4 Hz, 1H of CH2O), 3.72 (dd, 3JZ
11.0 Hz, 2JZ3.7 Hz, 1H of CH2O), 4.13 (m, 1H, NH–CH–
3
CH2O), 5.78 (d, JZ7.3 Hz, 1H, NH), 7.11 (s, 1H, ]CH).
IR (KBr, cmK1): 1571 (nC]C), 1615 (nC]O), 3186 (nOH). m/
4.3.1. (C/K)-2-(Ethylenedithio-tetrathiafulvalenyl)-4-
methyl-oxazoline (4a). From 0.2 g of 2a, orange-yellow
solid (0.16 g, 83% yield), mp 181–186 8C. 1H NMR
z
(MALDI-TOF): 394.96 (MC). Anal. Calcd for
C12H13NO2S6: C, 36.43; H, 3.31; N, 3.54. Found: C,
36.63; H, 3.37; N, 3.47.
3
(CDCl3): d 1.31 (d, JZ6.6 Hz, 3H, CH3), 3.29 (s, 4H, S–
3
CH2–CH2–S), 3.88 (t, JZ2JZ7.9 Hz, 1H of CH2O, Hsyn
/
3
3
3
4.2.3. 2-(S)-N-(1-Hydroxy-propyl)-ethylenedithio-tetra-
thiafulvalene-amide (2c). From (S)-alaninol (0.26 g, air
sensitive) and 1.05 g of EDT-TTF-COCl, red solid (0.93 g,
CH3), 4.31 (qdd, JZ9.2 Hz, JZ7.9 Hz, JZ6.6 Hz, 1H,
N–CH–CH2O), 4.45 (dd, JZ9.2 Hz, 2JZ7.9 Hz, 1H of
3
CH2O, Hanti/CH3), 6.97 (s, 1H, ]CH). 13C NMR (CDCl3):
d 21.8 (CH3), 30.8, 30.9 (S–CH2–CH2–S), 63.1 (CH–N),
75.5 (CH2O), 107.9, 114.3, 115.0, 116.5 (2C]C), 125.1
(]CH), 126.6 (]C–C]N), 157.3 (C]N). IR (KBr, cmK1):
1571 (nC]C), 1634 (nC]N). m/z (MALDI-TOF): 376.93
(MC). Anal. Calcd for C12H11NOS6: C, 38.17; H, 2.94; N,
3.71. Found: C, 38.05; H, 2.97; N, 3.62.
1
80% yield), mp 148–150 8C. H NMR, IR and MS spectra
are identical with those of 2b. Anal. Calcd for
C12H13NO2S6: C, 36.43; H, 3.31; N, 3.54. Found: C,
36.57; H, 3.41; N, 3.42.
4.2.4. 2-(C/K)-N-(1-Hydroxy-3-methylbutyl)-ethylene-
dithio-tetrathiafulvalene-amide (3a). From (C/K)-vali-
nol (0.18 g), orange crystals (0.3 g, 52% yield), mp 176–
177 8C. 1H NMR (CDCl3): d 0.96 (d, 3JZ6.8 Hz, 3H, CH3),
4.3.2. (R)-2-(Ethylenedithio-tetrathiafulvalenyl)-4-
methyl-oxazoline (4b). From 0.84 g of 2b, orange crystals
3
1
0.99 (d, JZ6.8 Hz, 3H, CH3), 1.93 (m, 1H, CH–(CH3)2),
(0.74 g, 92% yield), mp 202–203 8C. H NMR (CDCl3): d
3.30 (s, 4H, S–CH2–CH2–S), 3.74 (d, 3JZ3.7 Hz, 2H,
CH2O), 3.79 (m, 1H, NH–CH–CH2O), 5.75 (d, 3JZ8.5 Hz,
1H, NH), 7.12 (s, 1H, ]CH). IR (KBr, cmK1): 1571
(nC]C), 1615 (nC]O), 3186 (nOH). m/z (MALDI-TOF):
423.03 (MC). Anal. Calcd for C14H17NO2S6: C, 39.69; H,
4.04; N, 3.31. Found: C, 39.82; H, 4.05; N, 3.24.
1.31 (d, 3JZ6.7 Hz, 3H, CH3), 3.29 (s, 4H, S–CH2–CH2–S),
3.88 (t, 3JZ2JZ7.9 Hz, 1H of CH2O, Hsyn/CH3), 4.31 (qdd,
3JZ9.2 Hz, 3JZ7.9 Hz, 3JZ6.7 Hz, 1H, N–CH–CH2O),
4.45 (dd, 3JZ9.2 Hz, 2JZ7.9 Hz, 1H of CH2O, Hanti/CH3),
6.97 (s, 1H, ]CH). 13C NMR (CDCl3): d 21.1 (CH3), 30.1,
30.2 (S–CH2–CH2–S), 62.3 (CH–N), 74.8 (CH2O), 107.1,
113.5, 114.3, 115.8 (2C]C), 124.3 (]CH), 125.9 (]C–
C]N), 156.6 (C]N). IR (KBr, cmK1): 1571 (nC]C), 1634
(nC]N). m/z (MALDI-TOF): 376.94 (MC). Anal. Calcd for
C12H11NOS6: C, 38.17; H, 2.94; N, 3.71. Found: C, 38.43;
H, 2.93; N, 3.68.
4.2.5. 2-(R)-N-(1-Hydroxy-3-methylbutyl)-ethylene-
dithio-tetrathiafulvalene-amide (3b). From (R)-valinol
(0.472 g) and 1.28 g of EDT-TTF-COCl, orange solid
1
(1.34 g, 88% yield), mp 163–164 8C. H NMR (CDCl3): d
3
3
0.96 (d, JZ6.8 Hz, 3H, CH3), 0.98 (d, JZ6.8 Hz, 3H,
CH3), 1.93 (m, 1H, CH–(CH3)2), 3.30 (s, 4H, S–CH2–CH2–
S), 3.74 (d, 3JZ4.2 Hz, 2H, CH2O), 3.80 (m, 1H, NH–CH–
4.3.3. (S)-2-(Ethylenedithio-tetrathiafulvalenyl)-4-
methyl-oxazoline (4c). From 0.93 g of 2c, orange crystals
3
1
CH2O), 5.75 (d, JZ8.5 Hz, 1H, NH), 7.12 (s, 1H, ]CH).
(0.65 g, 73% yield), mp 202–203 8C. H NMR, 13C NMR,
IR (KBr, cmK1): 1571 (nC]C), 1615 (nC]O), 3186 (nOH).
m/z (MALDI-TOF): 422.91 (MC). Anal. Calcd for
C14H17NO2S6: C, 39.69; H, 4.04; N, 3.31. Found: C,
39.91; H, 4.12; N, 3.17.
IR and MS spectra are identical with those of 4b. Anal.
Calcd for C12H11NOS6: C, 38.17; H, 2.94; N, 3.71. Found:
C, 38.16; H, 2.87; N, 3.75.
4.3.4. (C/K)-2-(Ethylenedithio-tetrathiafulvalenyl)-4-
isopropyl-oxazoline (5a). From 0.25 g of 3a, orange solid
(0.21 g, 88% yield), mp 156–157 8C. H NMR (CDCl3): d
4.2.6. 2-(S)-N-(1-Hydroxy-3-methylbutyl)-ethylene-
dithio-tetrathiafulvalene-amide (3c). From (S)-valinol
(0.556 g) and 1.48 g of EDT-TTF-COCl, orange solid
(1.48 g, 84% yield), mp 163–164 8C. 1H NMR, IR and
MS spectra are identical with those of 3b. Anal. Calcd for
C14H17NO2S6: C, 39.69; H, 4.04; N, 3.31. Found: C, 39.89;
H, 4.15; N, 3.18.
1
3
3
0.88 (d, JZ6.7 Hz, 3H, CH3), 0.97 (d, JZ6.7 Hz, 3H,
CH3), 1.81 (m, 1H, CH–(CH3)2), 3.29 (s, 4H, S–CH2–CH2–
S), 4.03 (m, 1H, N–CH–CH2O), 4.06 (t, 3JZ2JZ7.3 Hz, 1H
of CH2O, Hsyn/iPr), 4.45 (dd, 2JZ7.3 Hz, 3JZ1.3 Hz, 1H of
CH2O, Hanti/iPr), 6.95 (s, 1H, ]CH). 13C NMR (CDCl3): d
18.6 (CH3), 19.5 (CH3), 30.8, 30.9 (S–CH2–CH2–S), 33.2
(CH–(CH3)2), 71.5 (CH–N), 73.5 (CH2O), 107.7, 114.3,
115.0, 116.9 (2C]C), 125.2 (]CH), 126.3 (]C–C]N),
157.1 (C]N). IR (KBr, cmK1): 1564 (nC]C), 1641 (nC]N).
m/z (MALDI-TOF): 404.89 (MC). Anal. Calcd for
C14H15NOS6: C, 41.45; H, 3.73; N, 3.45. Found: C, 41.14;
H, 3.86; N, 3.36.
4.3. General procedure for oxazolines
To a solution of hydroxy-amide 2–3 (5.06 mmol) and dry
triethylamine (1.5 mL, 10.76 mmol) in 150 mL of dry THF,
cooled at 0 8C, was added in one portion methanesulfonyl
chloride (0.8 mL, 10.34 mmol). After stirring at 0 8C for
30 min, another portion of triethylamine was added
(6.3 mL, 45.2 mmol), then the reaction mixture was heated
at 50 8C for approximately 20 h, that is, until the initially
4.3.5. (R)-2-(Ethylenedithio-tetrathiafulvalenyl)-4-iso-
propyl-oxazoline (5b). From 1.34 g of 3b, orange solid

´ ´
C. Rethore et al. / Tetrahedron 61 (2005) 10935–10942
10941
Table 3. Crystal and structure refinement data for 2a, 4c, 5b, 5c and (4a)2Mo6Cl14
2a
4c
5b
5c
(4a)2Mo6Cl14
Elemental formula
Formula weight
Crystal system
Space group
C12H13NO2S6
395.64
Monoclinic
P21/c
6.5992(9)
16.143(2)
15.824(2)
90
98.466(17)
90
1667.4(4)
4
0.821
293(2)
12937
3056
1162
0.057, 0.111
0.179, 0.140
C12H11NOS6
377.58
Monoclinic
P21
6.3167(5)
7.7578(7)
16.2434(12)
90
99.960(9)
90
783.99(11)
2
0.865
293(2)
6116
2911
2719
0.037, 0.101
0.040, 0.104
C14H15NOS6
405.63
C14H15NOS6
405.63
C24H22Cl14Mo6N2O2S12
1827.10
Monoclinic
P21/c
19.433
13.634
22.395
90
92.96
90
5925.7
4
2.313
293(2)
68687
13514
8169
0.044, 0.097
0.102, 0.115
Orthorhombic
P212121
6.4416(5)
14.3025(15)
19.3132(16)
90
90
90
1779.3(3)
4
0.768
293(2)
14353
3455
1907
0.058, 0.122
0.121, 0.145
Orthorhombic
P212121
6.4450(6)
14.313(2)
19.360(2)
90
90
90
1785.9(4)
4
0.765
293(2)
11220
3455
1247
0.043, 0.071
0.150, 0.094
˚
a (A)
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
3
˚
Cell volume, V (A )
No. of formula units/cell, Z
Absorption coefficient (mmK1
Temperature (K)
Total no. of refl. measured
No. of unique refl.
No. of ‘observed’ refl. (IO2sI)
R1, wR2 (‘observed’ data)a
R1, wR2 (all data)a
)
a R(Fo)ZSkFojKjFck/SjFoj; Rw(F2o)Z[S[w(F2oKFc2)2]/S[w(F2o)2]]1/2
.
1
(1.22 g, 95% yield), mp 150–151 8C. H NMR (CDCl3): d
least-square procedures on F2.21 Hydrogen atoms were
introduced at calculated positions (riding model), included
in structure factor calculations but not refined. All the heavy
atoms, but C24A and C24B in the structure (4a)2Mo6Cl14,
have been refined anisotropically. Crystallographic data have
been deposited with the Cambridge Crystallographic Data
Center as supplementary publication no. CCDC 262767–
262771 (CIF files). Copies of these data can be obtained free
of charge on application to CCDC, 12 Union Road,
Cambridge CB21EZ, UK (e-mail: deposit@ccdc.cam.ac.uk).
3
3
0.87 (d, JZ6.7 Hz, 3H, CH3), 0.97 (d, JZ6.7 Hz, 3H,
CH3), 1.81 (m, 1H, CH–(CH3)2), 3.29 (s, 4H, S–CH2–CH2–
S), 4.01–4.08 (m, 2H, N–CH–CH2O and 1H of CH2O,
2
3
Hsyn/iPr), 4.33 (dd, JZ7.4 Hz, JZ1.3 Hz, 1H of CH2O,
Hanti/iPr), 6.95 (s, 1H, ]CH). 13C NMR (CDCl3): d 18.0
(CH3), 18.9 (CH3), 30.1, 30.2 (S–CH2–CH2–S), 32.5 (CH–
(CH3)2), 70.9 (CH–N), 72.8 (CH2O), 106.9, 113.6, 114.3,
116.2 (2C]C), 124.5 (]CH), 125.6 (]C–C]N), 156.4
(C]N). IR (KBr, cmK1): 1564 (nC]C), 1641 (nC]N). m/z
(MALDI-TOF): 404.90 (MC). Anal. Calcd for
C14H15NOS6: C, 41.45; H, 3.73; N, 3.45. Found: C, 41.59;
H, 3.85; N, 3.41.
4.6. Theoretical calculations
The overlap interaction energies (bHOMO–HOMO) were of
extended-Hu¨ckel type.22 A modified Wolfsberg-Helmholtz
formula was used to calculate the non-diagonal Hmn
values.23 Double-z orbitals for C, S, N and O were used.
4.3.6. (S)-2-(Ethylenedithio-tetrathiafulvalenyl)-4-iso-
propyl-oxazoline (5c). From 1.48 g of 3c, orange solid
1
(1.35 g, 95% yield), mp 150–151 8C. H NMR, 13C NMR,
IR and MS spectra are identical with those of 5b. Anal.
Calcd for C14H15NOS6: C, 41.45; H, 3.73; N, 3.45. Found:
C, 41.47; H, 3.79; N, 3.36.
4.7. Cyclic voltammetry
Cyclic voltammetry studies were performed in a three-
electrode cell equipped with a platinum millielectrode of
0.126 cm2 area, an Ag/AgCl reference and a platinum wire
counter-electrode. The electrolytic media involved a
0.1 mol LK1 solution of (n-Bu4N)PF6 in dichloromethane.
All experiments have been performed at room temperature
4.4. Electrocrystallization
Two-compartment cell was used together with platinum
electrodes (2 cm long, 1 mm in diameter) and a current of
1 mA at room temperature (20G2 8C). [(n-Bu)4N]2Mo6Cl14
0.015 M in CH2Cl2 (20 mL) was used as electrolyte with the
donor 4a (5 mg), dissolved in the anodic compartment.
Electrolysis was performed during 7 days, after which air
stable plate-shaped crystals were harvested on the anode and
washed with little CH2Cl2.
at 0.1 V sK1
.
Acknowledgements
`
Financial support from the CNRS, Ministere de l’Education
et de la Recherche (grant for C.R.) and University of Angers
is gratefully acknowledged.
4.5. X-ray crystallography
Details about data collection and solution refinement are
given in Table 3. Data were collected on a Stoe Imaging
Plate System (IPDS) for the structures 2a, 4c, 5b and 5c and
on a Bruker-CCD System for the structure (4a)2Mo6Cl14,
both operating with a Mo Ka X-ray tube with a graphite
monochromator. The structures were solved (SHELXS-97)
by direct methods and refined (SHELXL-97) by full-matrix
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