Dimerization of monobenzoylated monopyrrolotetrathiafulvalene

Article abstract of DOI:10.1055/s-0031-1289739

Introduction of one benzoyl functional group into the 4-position of monopyrrolotetrathiafulvalene (MPTTF) affords MPTTF derivatives incorporating one hydrogen-bonding donor and one acceptor. This results in dimerization of the MPTTF derivatives in solutio

Full text of DOI:10.1055/s-0031-1289739

1126
PAPER
Dimerization of Monobenzoylated Monopyrrolotetrathiafulvalene
Dimerization of
M
e
onobenzoy
n
late
d
Monop
t
yrrolotetrathi
A
a
fulvalene . Nielsen,* Andrew D. Bond, Karina R. Larsen
Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
Fax +45 66158780; E-mail: kan@ifk.sdu.dk
Received 9 January 2012; revised 2 February 2012
1. EtMgBr (5 equiv)
Abstract: Introduction of one benzoyl functional group into the 4-
position of monopyrrolotetrathiafulvalene (MPTTF) affords MPTTF
derivatives incorporating one hydrogen-bonding donor and one
acceptor. This results in dimerization of the MPTTF derivatives in
solution and in the solid state.
THF, 30 min
2. 2 (7.5 equiv), THF, 15 min
or
3 (6.0 equiv), THF, 5 h
C5H11
S
S
S
S
S
S
NH
C5H11
2: benzoyl chloride
3: 4-cyanobenzoyl chloride
1
Key words: tetrathiafulvalene, functionalization, benzoylation,
dimerization, pyrroles
R1
Tetrathiafulvalenes1 (TTFs) have attracted significant at-
tention for many years due to the discovery of TTF con-
taining organic metals,2 and superconducting3 salts, and
for their use in molecular systems such as chemical
sensors,4 switches,5 and electronic devices.6 In continua-
tion of our work on the development of useful monopyrrolo-
tetrathiafulvalene7 (MPTTF) building blocks, we report that
introduction of one benzoyl group in the 4-position of the
MPTTF unit 1 (Scheme 1) results in novel MPTTF deriv-
atives 4a and 4b carrying one hydrogen-bonding donor
(pyrrole NH proton) and one hydrogen-bonding acceptor
(carbonyl oxygen). The MPTTF units 4a and 4b self-as-
semble in solution and in the solid state to form the dimer-
ic structures 4a·4a and 4b·4b.
1. NaH, DMF, r.t., 30 min
2. MeI, DMF, r.t., 1.5 h
or
O
C5H11
S
S
S
S
S
S
n-PrI, DMF, r.t., 24 h
NH
C5H11
4a: R1 = H, 86%
4b: R1 = CN, 60%
O
C5H11
S
S
S
S
S
N
R2
C5H11
S
5a: R2 = Me, 85%
5b: R2 = n-Pr, 77%
Monobenzoylation of MPTTF 17 in its 4-position was car-
ried out according to a modified literature8 procedure
(Scheme 1). Addition of 5.0 equivalents of ethylmagne-
sium bromide to an anhydrous THF solution of MPTTF 1,
followed by the addition of either 7.5 equivalents of ben-
zoyl chloride (2) or 6.0 equivalents of 4-cyanobenzoyl
chloride (3), gave after fifteen minutes or five hours, re-
spectively, one major spot on thin-layer chromatography.
Column chromatographic purifications gave the
monobenzoylated MPTTF units 4a and 4b (Scheme 1) as
orange and red solids in 86 and 60% yield, respectively.
Recrystallization was carried out by diffusion of a MeOH
solvent layer into a CH2Cl2 solution: 4a was isolated as
fine orange plates and 4b as fine dark red plates. We have
also prepared N-alkylated derivatives, for which dimer-
ization should not be expected on account of removal of
the NH donor. The N-alkylations (Scheme 1) were carried
out by deprotonation of 4a using excess sodium hydride
followed by the addition of either iodomethane or 1-io-
dopropane, resulting in the isolation of 5a and 5b in 85
and 77% yield, respectively.
Scheme 1 Synthesis of monobenzoylated MPTTF derivatives 4a,
and 4b, and the N-alkylated derivatives 5a, and 5b starting from the
MPTTF unit 1
For the analytically pure products 4a, 4b, 5a, and 5b,
high-resolution matrix-assisted laser desorption/ioniza-
tion mass spectrometry HRMS (MALDI-FT) showed ex-
act masses m/z 551.0597, 576.0549, 565.0765, and
593.0971, respectively, corresponding to M•+ (calcd mass
m/z M•+ 551.0573, 576.0526, 565.0726, and 593.1043).
The UV-Vis spectra of 1, 4a, 4b, 5a, and 5b (Figure 1)
showed strong absorbance in the region between 200 and
400 nm. In the region between 400 and 600 nm (insert in
Figure 1) higher absorbance was observed for 4a, 4b, 5a,
and 5b than for the parent MPTTF unit 1. This change in
absorbance is attributed to electron delocalization from
the electron-rich MPTTF unit to the electron-withdrawing
benzoyl substituent. Solution oxidation potentials
(Table 1) obtained from cyclic voltammograms revealed
two pairs of reversible redox waves for all compounds
(Figure 2a), corresponding to oxidation to the radical cat-
ion (MPTTF•+) and then to the dication (MPTTF2+). From
differential pulse measurements (Figure 2b) it can be seen
that each oxidation corresponds to an equal number of
electrons. Table 1 summarizes the oxidation potentials
SYNTHESIS 2012, 44, 1126–1130
x
x.
x
x.
2
0
1
2
Advanced online publication: 08.03.2012
DOI: 10.1055/s-0031-1289739; Art ID: T002712SS
© Georg Thieme Verlag Stuttgart · New York

PAPER
Dimerization of Monobenzoylated Monopyrrolotetrathiafulvalene
1127
obtained. In all cases, higher oxidation potentials are ob-
served for the MPTTF derivatives than for the parent
MPTTF unit 1. For 4a, changes in the first and second ox-
idation potential of DE1 = 80 mV and DE2 = 80 mV were
observed, whereas for 4b slightly larger changes of
DE1 = 100 and DE2 = 90 mV were observed. This differ-
ence is attributed to the electron-withdrawing nature of
the CN group of the 4-cyanobenzoyl substituent. Cyclic
voltammetry of the N-alkylated products 5a and 5b result-
ed in a smaller change for the second oxidation potential
(DE2 = 60 mV) compared to 4a (DE2 = 80 mV).
Figure 1 UV-Vis absorption spectra of 1, 4a, 4b, 5a, and 5b (2.0 ×
10–5 M) recorded in MeCN at 298 K
Table 1 Oxidation Potentials E1/21 and E1/22 of the MPTTF Deriva-
tives 1, 4a, 4b, 5a, and 5b Determined by Cyclic Voltammetrya
Figure 2 (a) Cyclic voltammetry and (b) differential pulse spectra
of 1, 4a, 4b, 5a, and 5b recorded in MeCN at 298 K
Compound E1/21 (V)
E1/22 (V)
0.44
DE1 (V) 1
–
DE2 (V) 1
–
MPTTF unit, by approximately 8 and 42°, respectively, in
4b, and by approximately 15 and 72°, respectively, in 5a.
1
0.12
0.20
0.22
0.20
0.20
Results from the X-ray crystal structure analysis encour-
aged us to investigate the dimerization of 4a and 4b in so-
lution. Upon dilution of a concentrated solution of 4b
(156–2.0 mM, see Figure S25 in the Supporting Informa-
tion), a significant upfield peak shift Dd = 0.76 ppm for
the NH proton was observed. This indicates that the MPTTF
unit forms intermolecular aggregates in solution. By
fitting the data (for 4a, see Figures S23 and S24 in the
4a
4b
5a
5b
0.52
0.08
0.10
0.08
0.08
0.08
0.09
0.06
0.06
0.53
0.50
0.50
a Cyclic voltammetry conditions: Ag/AgNO3 electrode, Pt electrode,
20 °C, Bu4NPF6 (0.1 M in MeCN), scan rate 0.1 V s–1. Concentration
of compound: 10–3 M.
Single crystals of 4b and 5a suitable for X-ray diffraction
analysis were obtained by diffusion of a MeOH solvent
layer into a CH2Cl2 solution containing the compound.
The structure analysis of 4b (Figure 3) contains intermo-
lecular hydrogen bonds that produce a centrosymmetric
4b·4b dimer structure in the solid state. The two hydrogen
bonds in the dimer are formed between the NH proton
from one molecule of 4b to the carbonyl oxygen of the
second molecule of 4b. For the MPTTF unit 5a (Figure 4),
elimination of the NH proton means that dimer formation
is not observed. For both structures, the carbonyl group
and the benzene ring are twisted out of the plane of the
Figure 3 X-ray crystal structure of 4b showing the dimer formation
4b·4b; H atoms are omitted except for the NH protons
© Thieme Stuttgart · New York
Synthesis 2012, 44, 1126–1130

1128
K. A. Nielsen et al.
PAPER
2-[4,5-Bis(pentylthio)-1,3-dithiol-2-ylidene]-4-benzoyl-1,3-
dithiolo[4,5-c]pyrrole (4a)
MPTTF (1; 0.22 g, 0.50 mmol) was dissolved in anhyd THF (5 mL)
in an atmosphere of argon. EtMgBr (0.83 mL of a 3.0 M solution in
Et2O, 2.5 mmol) was slowly added over a period of 5 min at r.t.,
causing an exothermic reaction with evolution of gas and a color
change from yellow to orange. The reaction mixture was stirred at
r.t. for 30 min, whereafter benzoyl chloride (2; 0.53 g, 0.44 mL,
3.75 mmol) was added over a period of 5 min, causing a color
change from orange to dark red. The mixture was stirred for 15 min
at r.t. before sat. aq NH4Cl (5 mL) was carefully added. The result-
ing suspension was extracted with CH2Cl2 (50 mL), then the organic
phase was washed with H2O (3 × 20 mL) and dried (MgSO4). Evap-
oration of the solvent gave a dark red oil, which was purified by col-
umn chromatography (200 mL SiO2, Ø = 4 cm; CH2Cl2) to give 4a
as an analytically pure orange solid; yield: 0.24 g (86%). Recrystal-
lization from CH2Cl2–MeOH gave 4a as fine orange plates; mp
105–107 °C.
Figure 4 X-ray crystal structures of 4b and 5a; H atoms are omitted
except for the NH protons
IR (KBr): 1605 cm–1.
Supporting Information), assuming a monomer to dimer
equilibrium, dimerization constants KD = 1.0 and 2.0 M–1
were obtained for 4a and 4b, respectively.
1H NMR (CDCl3/TMS): d = 0.89 (t, J = 6.8 Hz, 3 H), 0.89 (t,
J = 6.8 Hz, 3 H), 1.23–1.42 (m, 8 H), 1.54–1.68 (m, 4 H), 2.78 (t,
J = 7.6 Hz, 2 H), 2.80 (t, J = 7.6 Hz, 2 H), 6.89 (s, 1 H), 7.47–7.56
(m, 2 H), 7.58–7.65 (m, 1 H), 7.73–7.78 (m, 2 H), 9.76 (br s, 1 H).
13C NMR (CDCl3/TMS): d = 13.9 (2 overlapping peaks), 22.2, 22.2,
29.3, 29.4, 30.6, 30.6, 36.2, 36.2, 112.4, 116.5, 117.9, 122.4, 124.0,
127.4, 127.6, 128.0, 128.9, 130.2, 132.4, 137.2, 183.8.
HRMS (MALDI-FT): m/z calcd for C25H29NOS6•+: 551.0573;
found: 551.0597.
CV (MeCN, vs. Ag/AgNO3): E1/22 = 0.20 V, E1/22 = 0.52 V.
UV-Vis (MeCN, 298 K): lmax = 430 nm, e = 4645 L mol cm–1.
In conclusion, we have developed a synthetic method that
allows the parent MPTTF unit 1 to be monobenzoylated in
the 4-position, and demonstrated that the resulting MPTTF
unit 4a can be N-alkylated in good yields. Further, it was
shown that the MPTTF units 4a and 4b form dimers in so-
lution and this was also established for 4b in the solid
state, utilizing hydrogen bonding between the pyrrole NH
proton and the carbonyl oxygen, and thereby demonstrat-
ing control of the intermolecular arrangement between
MPTTF units.
Anal. Calcd for C25H29NOS6 (551.9): C, 54.41; H, 5.30; N, 2.54; S,
34.86. Found: C, 54.53; H, 5.29; N, 2.61; S, 34.96.
All reactions were carried out under a dry N2 atmosphere unless oth-
erwise stated. Benzoyl chloride was distilled under reduced pres-
sure prior to use. All other chemicals were purchased from
commercial sources and were used as received. Solvents were dried
according to literature procedures.9 TLC was carried out using alu-
minum sheets pre-coated with silica gel 60 F254 (Merck 5554). The
plates were inspected under UV light (254 nm) and, if required, de-
veloped in I2 vapor. Column chromatography was carried out using
silica gel 60F (Merck 9385, 0.040–0.063 mm). Melting points were
determined on a Büchi melting point apparatus and are uncorrected.
1H NMR (300 MHz) and 13C NMR (75 MHz) spectra were recorded
on a Gemini-300BB instrument, using TMS or the residual solvent
as the internal standard, which were assigned on the basis of Nudel-
man.10 Fourier transform matrix-assisted laser-desorption/ioniza-
tion mass spectrometry (FT–MALDI–MS) was performed on an
IonSpec 4.7 Tesla Ultima Fourier Transform mass spectrometer,
utilizing a 2,5-dihydroxybenzoic acid (DHP) matrix. Electrochemi-
cal experiments were carried out at r.t. in N2-purged MeCN solution
with an Autolab/PGSTAT 10 instrument interfaced to a personal
computer, using cyclic voltammetry (CV) technique. Working and
counter electrodes were made of Pt, and the reference electrode was
Ag/AgNO3. The concentration of the examined compounds was 10–3
M and 0.10 M n-Bu4NPF6 was added as supporting electrolyte.
Cyclic voltammograms were obtained with a sweep rate of 100
mV s–1. The half-wave potentials E1/2 reported were obtained from
an average of the cathodic and anodic cyclic voltammetric peaks.
Ultraviolet-visible (UV-Vis) measurements were performed on a
Shimadzu UV-1601PC instrument at 298 K. Microanalyses were
performed by the Atlantic Microlab, Inc., Atlanta, Georgia, USA.
X-ray diffraction data were collected using a Bruker Nonius X8-
APEXII instrument with MoKa radiation.
2-[4,5-Bis(pentylthio)-1,3-dithiol-2-ylidene]-4-(4-cyanoben-
zoyl)-1,3-dithiolo[4,5-c]pyrrole (4b)
MPTTF (1; 0.30 g, 0.67 mmol) was dissolved in anhyd THF (3 mL)
in an atmosphere of argon. EtMgBr (1.12 mL of a 3.0 M solution in
Et2O, 3.35 mmol) was slowly added over a period of 5 min at r.t.,
causing an exothermic reaction with evolution of gas and a color
change from yellow to orange. The reaction mixture was stirred at
r.t. for 30 min, whereafter 4-cyanobenzoyl chloride (3; 0.68 g,
4.0 mmol) was added in one portion, causing a gas evolution and a
color change from orange to dark red. The mixture was stirred for 5
h at r.t. before a solution of sat. aq NH4Cl (5 mL) was added care-
fully. The suspension was extracted with CH2Cl2 (100 mL), the or-
ganic phase washed with H2O (3 × 50 mL), and dried (MgSO4).
Evaporation of the solvent gave a dark red oil, which was purified
by column chromatography (300 mL SiO2, Ø = 4.5 cm; CH2Cl2–
MeOH, 19:1) to give 4b as an analytically pure dark red solid; yield:
0.23 mg (60%). Recrystallization from CH2Cl2–MeOH gave 4b as
fine dark red plates suitable for X-ray crystal structure analysis; mp
168–169 °C.
IR (KBr): 2231, 1601 cm–1.
1H NMR (CDCl3/TMS): d = 0.90 (t, J = 7.1 Hz, 6 H), 1.22–1.42 (m,
8 H), 1.55–1.68 (m, 4 H), 2.80 (t, J = 7.2 Hz, 2 H), 2.80 (t, J = 7.3
Hz, 2 H), 6.95 (d, J = 3.1 Hz, 1 H), 7.79–7.85 (m, 4 H), 9.51 (br s,
1 H).
13C NMR (CDCl3/TMS): d = 13.9 (2 overlapping peaks), 22.2 (2
overlapping peaks), 29.3, 29.4, 30.6, 30.6, 36.2, 36.3, 113.9, 115.8,
116.3, 117.4, 118.0, 123.2, 123.4, 127.6, 127.6, 128.5, 130.8, 132.7,
140.9, 181.7.
HRMS (MALDI-FT): m/z calcd for C26H28N2OS6•+: 576.0526;
found: 576.0549.
Synthesis 2012, 44, 1126–1130
© Thieme Stuttgart · New York

PAPER
Dimerization of Monobenzoylated Monopyrrolotetrathiafulvalene
X-ray Crystal Data11
1129
CV (MeCN, vs. Ag/AgNO3): E1/21 = 0.22 V, E1/22 = 0.53 V.
UV-Vis (MeCN, 298 K): lmax = 430 nm, e = 4510 L mol cm–1.
Crystal data for 4b: empirical formula C26H28N2OS6; formula
weight 576.86; triclinic; space group P1; a = 8.7845(15) Å,
Anal. Calcd for C26H28N2OS6 (576.9): C, 54.13; H, 4.89; N, 4.86; S,
33.35. Found: C, 54.07; H, 4.82; N, 4.98; S, 33.61.
b = 9.4268(16)
Å,
c = 17.316(3)
Å,
a = 99.188(4)°,
b = 93.327(3)°, g = 108.269(3)°; V = 1335.2(4) Å3; Z = 2;
Dcalcd = 1.435 Mg m–3; l = 0.7107 Å; absorption coefficient = 0.536
mm–1;
F(000) = 604;
0.55 × 0.13 × 0.02 mm.
T = 120(2)
K;
crystal
size =
2-[4,5-Bis(pentylthio)-1,3-dithiol-2-ylidene]-4-benzoyl-5-meth-
yl-1,3-dithiolo[4,5-c]pyrrole (5a)
MPTTF (4a; 22.1 mg, 0.040 mmol) was dissolved in anhyd DMF
(2 mL) and the solution was degassed with N2 for 15 min before
NaH (0.016 g of a 60% suspension in mineral oil, 0.40 mmol) was
added in one portion. The reaction mixture was stirred for 30 min at
r.t., causing the initially yellow solution to become orange. MeI
(0.04 mL, 85.2 mg, 0.6 mmol) was added in one portion, causing a
new color change from orange to yellow. The reaction mixture was
stirred for 1 h and then purged with N2, followed by the addition of
brine (10 mL). The yellow precipitate was filtered, then washed
with H2O (2 × 10 mL) and MeOH (10 mL). After drying in vacuo,
the yellow solid was purified by column chromatography (50 mL
SiO2, Ø = 2.5 cm; CH2Cl2) to give 5a as an analytically pure orange
solid; yield: 19.2 mg (85%); mp 81–82 °C.
Crystal data for 5a: empirical formula C26H31NOS6; formula weight
565.88; monoclinic; space group P21/c; a = 16.124(2) Å,
b = 5.3533(5) Å, c = 32.152(4) Å, a = 90°, b = 99.778(4)°,
g = 90°; V = 2734.9(5) Å3; Z = 4; Dcalcd = 1.374 Mg m–3;
l = 0.7107 Å; absorption coefficient = 0.521 mm–1; F(000) = 1192;
T = 180(2) K; crystal size = 0.25 × 0.03 × 0.01 mm.
Supporting Information for this article is available online at
http://www.thieme-connect.com/ejournals/toc/synthesis.
Acknowledgment
IR (KBr): 1629 cm–1.
This work was supported by the Danish Natural Science Research
Council (FNU, project no. 272-08-0047) and the University of
Southern Denmark (SDU).
1H NMR (CDCl3/TMS): d = 0.89 (t, J = 6.9 Hz, 6 H), 1.24–1.41 (m,
8 H), 1.60 (sext, J = 7.3 Hz, 4 H), 2.75 (t, J = 7.3 Hz, 2 H), 2.79 (t,
J = 7.3 Hz, 2 H), 3.95 (br s, 3 H), 6.69 (s, 1 H), 7.46–7.54 (m, 2 H),
7.57–7.64 (m, 1 H), 7.67–7.73 (m, 2 H).
References
HRMS (MALDI-FT): m/z calcd for C26H31NOS6•+: 565.0724;
found: 565.0765.
(1) (a) Canevet, D.; Sallé, M.; Zhang, G.; Zhang, D.; Zhub, D.
Chem. Commun. 2009, 2245. (b) Segura, J. L.; Martín, N.
Angew. Chem. Int. Ed. 2001, 40, 1372; Angew. Chem. 2001,
113, 1416. (c) Becher, J.; Jeppesen, J. O.; Nielsen, K. Synth.
Met. 2003, 133-134, 309. (d) Bryce, M. R. J. Mater. Chem.
2000, 10, 589. (e) Schukat, G.; Fanghänel, E. Sulfur Rep.
1996, 18, 1.
CV (MeCN, vs. Ag/AgNO3): E1/21 = 0.20 V, E1/22 = 0.50 V.
UV-Vis (MeCN, 298 K): lmax = 430 nm, e = 4980 L mol cm–1.
Anal. Calcd for C26H31NOS6 (565.9): C, 55.18; H, 5.52; N, 2.48; S,
34.00. Found: C, 55.14; H, 5.41; N, 2.41; S, 34.26.
(2) Ferraris, J.; Cowan, D. O.; Walatka, V. V. Jr.; Perlstein, J. H.
J. Am. Chem. Soc. 1973, 95, 948.
2-[4,5-Bis(pentylthio)-1,3-dithiol-2-ylidene]-4-benzoyl-5-pro-
pyl-1,3-dithiolo[4,5-c]pyrrole (5b)
(3) (a) Jérome, D.; Mazaud, A.; Ribault, M.; Bechgaard, K.
J. Phys. Lett. 1980, 41, L95. (b) Jérome, D. Chem. Rev.
2004, 104, 5565.
MPTTF (4a; 22.1 mg, 0.040 mmol) was dissolved in anhyd DMF
(2 mL) and the solution was degassed with N2 for 15 min before
NaH (0.016 g of a 60% suspension in mineral oil, 0.40 mmol) was
added in one portion. The reaction mixture was stirred for 30 min at
r.t., causing the initially yellow solution to become orange. 1-Io-
dopropane (5.9 mL, 10.2 mg, 0.06 mmol) was added in one portion.
The reaction mixture was stirred for 24 h and then purged with N2,
followed by the addition of brine (10 mL). The yellow precipitate
was filtered, then washed with H2O (2 × 10 mL) and MeOH
(10 mL). After drying in vacuo, the yellow solid was purified by
column chromatography (50 mL SiO2, Ø = 2.5 cm; CH2Cl2) to give
the title compound 5b as an analytically pure orange solid; yield:
18.3 mg (77%); mp 64–65 °C.
(4) (a) Nielsen, K. A.; Bähring, S.; Jeppesen, J. O. Chem. Eur. J.
2011, 17, 11001. (b) Park, J. S.; Derf, F. L.; Bejger, C. M.;
Lynch, V. M.; Sessler, J. L.; Nielsen, K. A.; Johnsen, C.;
Jeppesen, J. O. Chem. Eur. J. 2010, 16, 848. (c) Nielsen, K.
A.; Cho, W.-S.; Sarova, G. H.; Petersen, B. M.; Bond, A. D.;
Becher, J.; Jensen, F.; Guldi, D. M.; Sessler, J. L.; Jeppesen,
J. O. Angew. Chem. Int. Ed. 2006, 45, 6848; Angew. Chem.
2006, 118, 7002. (d) Nielsen, K. A.; Cho, W.-S.; Lyskawa,
J.; Levillain, E.; Lynch, V. M.; Sessler, J. L.; Jeppesen, J. O.
J. Am. Chem. Soc. 2006, 128, 2444. (e) Nielsen, K. A.; Cho,
W.-S.; Jeppesen, J. O.; Lynch, V. M.; Becher, J.; Sessler, J.
L. J. Am. Chem. Soc. 2004, 126, 16296.
(5) (a) Jeppesen, J. O.; Perkins, J.; Becher, J.; Stoddart, J. F.
Angew. Chem. Int. Ed. 2001, 40, 1216; Angew. Chem. 2001,
113, 1256. (b) Jeppesen, J. O.; Nielsen, K. A.; Perkins, J.;
Vignon, S. A.; Di Fabio, A.; Ballardini, R.; Gandolfi, M. T.;
Venturi, M.; Balzani, V.; Becher, J.; Stoddart, J. F. Chem.
Eur. J. 2003, 9, 2982. (c) Nygaard, S.; Leung, K. C.-F.;
Aprahamian, I.; Ikeda, T.; Saha, S.; Laursen, B. W.; Kim,
S.-Y.; Hansen, S. W.; Stein, P. C.; Flood, A. H.; Stoddart, J.
F.; Jeppesen, J. O. J. Am. Chem. Soc. 2007, 129, 960.
(6) (a) Collier, C. P.; Mattersteig, G.; Wong, E. W.; Lou, Y.;
Beverly, K.; Sampaio, J.; Raymo, F. M.; Stoddart, J. F.;
Heath, J. R. Science 2000, 289, 1172. (b) Luo, Y.; Collier,
C. P.; Jeppesen, J. O.; Nielsen, K. A.; Delonno, E.; Ho, G.;
Perkins, J.; Tseng, H.-R.; Yamamoto, T.; Stoddart, J. F.;
Heath, J. R. ChemPhysChem 2002, 3, 519. (c) Flood, A. H.;
IR (KBr): 1631 cm–1.
1H NMR (CDCl3/TMS): d = 0.89 (t, J = 7.0 Hz, 6 H), 0.93 (t,
J = 7.4 Hz, 3 H), 1.23–1.42 (m, 8 H), 1.60 (sext, J = 7.4 Hz, 4 H),
1.79 (sext, J = 7.2 Hz, 2 H), 2.75 (m, J = 7.4 Hz, 4 H), 4.28 (br s, 2
H), 6.75 (s, 1 H), 7.46–7.53 (m, 2 H), 7.57–7.64 (m, 1 H), 7.66–7.72
(m, 2 H).
HRMS (MALDI-FT): m/z calcd for C28H35NOS6•+: 593.1043;
found: 593.0971.
CV (MeCN, vs. Ag/AgNO3): E1/21 = 0.20 V, E1/22 = 0.50 V.
UV-Vis (MeCN, 298 K): lmax = 430 nm, e = 4250 L mol cm–1.
Anal. Calcd for C28H35NOS6 (593.98): C, 56.62; H, 5.94; S, 32.39.
Found: C, 56.86; H, 5.95; S, 32.47.
© Thieme Stuttgart · New York
Synthesis 2012, 44, 1126–1130

1130
K. A. Nielsen et al.
PAPER
Stoddart, J. F.; Steuerman, D. W.; Heath, J. R. Science 2004,
306, 2055. (d) Green, E.; Choi, J. W.; Boukai, A.;
Bunimovich, Y.; Johnston-Halperin, E.; Delonno, E.; Luo,
Y.; Sheriff, B. A.; Xu, K.; Shin, Y. S.; Tseng, H.-R.;
Stoddart, J. F.; Heath, J. R. Nature 2007, 445, 414.
(9) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals; Pergamon Press: New York, 1988.
(10) Gottlieb, H. E.; Kotlyar, V.; Nudelman, A. J. Org. Chem.
1997, 62, 7512.
(11) CCDC 861255 (4b) and CCDC 861256 (5a) contain the
supplementary crystallographic data for compounds
described in this paper. These data can be obtained free of
charge at www.ccdc.cam.ac.uk/conts/retrieving.html [or
from the Cambridge Crystallographic Data Centre, 12 Union
Road, Cambridge CB2 1EZ, UK; fax: +44(1223)336033,
E-mail: deposit@ccdc.cam.ac.uk].
(7) Jeppesen, J. O.; Takimiya, K.; Jensen, F.; Brimert, T.;
Nielsen, K.; Thorup, N.; Becher, J. J. Org. Chem. 2000, 65,
5794.
(8) (a) Cho, W.-S.; Kim, H. J.; Littler, B. J.; Miller, M. A.; Lee,
C.-H.; Lindsey, J. S. J. Org. Chem. 1999, 64, 7890. (b)Lee,
C.-H.; Li, F.; Iwamoto, K.; Dadok, J.; Bothner-By, A. A.;
Lindsey, J. S. Tetrahedron 1995, 51, 11645.
Synthesis 2012, 44, 1126–1130
© Thieme Stuttgart · New York