Synthesis of novel alkyl- and aryl sulfides and thiols as precursors for self-assembled monolayers on gold

Article abstract of DOI:10.1055/s-2004-831163

A series of 4-alkyl-1-bromosulfanylbenzenes having S-methyl 2, S-t-butyl 3, S-trityl 4, S-benzyl S, and S-silylethoxymethyl 6 substituents were prepared and evaluated for their ability to form a monolayer consisting of an S-aryl adsorbate on Au (111) surf

Full text of DOI:10.1055/s-2004-831163

PAPER
2283
Synthesis of Novel Alkyl- and Aryl Sulfides and Thiols as Precursors for
Self-Assembled Monolayers on Gold
S
ulfides
a
nd Thiols
a
s
o
Precursors
f
o
h
r
Self-Asse
m
a
bled Mon
m
olayers on
G
old ed Touaibia, Marc-André Desjardins, Alexandre Provençal, Daniel Audet, Christelle Médard, Mario Morin,
Livain Breau*
Département de Chimie and Laboratoire de Synthèse Organique Appliquée, Département de Chimie, Université du Québec à Montréal,
Case Postale 8888, Succursale Centre-Ville, Montréal, Québec, H3C 3P8, Canada
E-mail: breau.livain@uqam.ca
Received 13 April 2004
the spectroscopic studies that were undertaken to address
Abstract: A series of 4-alkyl-1-bromosulfanylbenzenes having S-
issues that arose concerning the composition and regular-
ity of the monolayers, which resulted from the elec-
trodeposition of these sulfides.
methyl 2, S-t-butyl 3, S-trityl 4, S-benzyl 5, and S-silylethoxymethyl
6 substituents were prepared and evaluated for their ability to form
a monolayer consisting of an S-aryl adsorbate on Au (111) surface.
The monolayer was formed via the selective hydrolytic removal of
an alkyl group protecting the sulfur functionality upon adsorbtion
onto the gold surface. Thiols having variable carbon chain length
and a peripheral thiophene moiety 9, 10, 17, 18 and 23–26 were also
prepared.
In addition to synthesizing sulfides using mercurial thio-
lates complexes in combination with symmetrical
disulfides14 as well as those involving the coupling of a
thiol with a chloride or bromide catalyzed by Pd15,16 or
Ni,16 we developed an efficient method for the protection
of the thiol function of 1 as an S-t-butyl or S-trityl group
from their corresponding alcohols. Typically, formation
of the former involved the use of either isobutylene gas in
an acidic medium or the corresponding tert-butyl halide in
the presence of an organic base or a Lewis acid.17 Both
methods provided variable yields of 3. The use of tert-bu-
tyl alcohol, with acetic anhydride as a dehydrating agent,
led to good, reproducible yields of 3 (Scheme 1). This
method is general for the preparation of S-t-butyl aromatic
sulfides such as 4-nitro-tert-butylsulfanylbenzene18 and
2-tert-butylsulfanylnaphthalene.18a This method was used
to efficiently prepare S-trityl derivative 4 from triphenyl-
carbinol. In all cases the yields were equal to, or higher
than, those obtained from the substitution using the corre-
sponding t-butyl or trityl chloride.
Key words: 4-alkyl-1-bromosulfanyl benzenes, 4-thienylthiophe-
nols, thienylalkanethiols, self-assembled monolayers on gold
Conjugated organic materials have the potential to serve
as molecular components for electronic devices.1–4 The
broad applicability of conjugated thiol compounds in mo-
lecular electronics is based on their unique ability to form
well-ordered monolayers via a self-assembly process onto
gold or other metal surfaces.5–8 Unfortunately, it has re-
cently been shown that this property is not general for all
aromatic thiol compounds.8 Characterization of the self-
assembled monolayer molecular arrays which do serve as
active layers in electronic devices is an important step in
the search to understand and control molecular-scale elec-
tronics.
The substituents most suitable for adsorption onto a metal
surface include thiols (RSH),9 disulfides (RSSR), thioace-
tyls (RSCOCH3),10 and symmetric sulfides (RSR).11,12
Thiols and disulfides are found to adsorb dissociatively on
gold and form densely packed layers.13 Sulfides are found
to adsorb either molecularly or dissociatively into a thio-
late on gold. However, sulfides are simpler to synthesize
as no deprotection of the thiol is needed. An appropriate
protecting group for the sulfur-bearing moiety must be ro-
bust enough to remain intact throughout the various orga-
nometallic coupling reactions and must also be selectively
removable with formation of the monolayer. Hence, we
imagined the use of an asymmetric sulfide that would pro-
mote the selective dissociation upon adsorption. Herein,
we report an efficient synthesis of, and subsequent forma-
tion of, the monolayers from various alkyl aryl sulfides 3–
6, derived from 4-bromothiophenol (1). We also discuss
Br
Br
SR
SH
2 R =CH3
3 R = t-Bu
4 R = CPh3
1
R3COH, Ac2O,
AcOH, HClO4
PhCH2Br, Et3N
RCl, Et3N
5 R = CH2Ph
6 R = CH2O(CH2)2Si(CH3)3
Scheme 1
However, the use of a secondary or benzylic alcohol in the
same reaction with acetic anhydride leads to the formation
of the corresponding acetate. This occurs because these
alcohols are more nucleophilic and, thus are able to react
directly with acetic anhydride. Therefore, for this study,
the S-benzyl 5 and S-SEM 6 protecting groups were intro-
duced via a substitution reaction with benzyl bromide and
SEM chloride, respectively.
SYNTHESIS 2004, No. 14, pp 2283–2288
x
x.
x
x
.
2
0
0
4
Advanced online publication: 23.08.2004
DOI: 10.1055/s-2004-831163; Art ID: M02504SS
© Georg Thieme Verlag Stuttgart · New York

2284
M. Touaibia et al.
PAPER
left in the solution for three days, after which the surface
composition was analyzed using X-Ray photoelectron
spectroscopy (XPS). The 2p level of the sulfur and 3p lev-
el of the bromine, shown in Figure 1, were used to quan-
tify the amount of p-bromothiophenolate adsorbed onto
the surface. Quantification of the amount of adsorption for
those R groups of the compounds shown in Scheme 1 rel-
ative to p-bromothiophenolate moiety, following disso-
ciative adsorption, was calculated from their XPS
intensities. For example, an atomic ratio for I (Br)/I (S) of
1 indicates that only the p-bromothiophenolate (100%) is
adsorbed onto the gold whereas a ratio of 0 means that this
compound is not present at the surface (0%). Hence, this
allowed us to evalutate and compare the relative efficien-
cies of the leaving groups (t-butyl, benzyl, triphenylmeth-
yl, methyl, hydrogen and SEM). We found that a complete
(100%) monolayer of thiophenolate was formed by the p-
bromothiophenol. An almost complete (60%) monolayer
of thiophenolate was also formed by the t-butyl derivative
3 (Figure 1), although some tert-butylthiolate was also ad-
sorbed. A partial monolayer was formed by the SEM de-
rivative (10%) and no p-bromothiophenolate (0%) was
adsorbed in the case of the triphenylmethyl, benzyl and
methyl derivatives. Preliminary results showed higher
coverage for the electro-deposition of most of the thiophe-
nolate derivatives. These results will be reported else-
where.
Figure 1 XPS spectra of 3 adsorbed on a gold substrate (a) Br 3d
orbital region, (b) S 2p orbital region
S
S
2
S
AlCl3
87%
Br
68%
S-t-Bu
SH
9
7
3
2
We have also used a t-butyl protecting group for the syn-
thesis of an aromatic thiol. The syntheses of 9 and 10, as
shown in Scheme 2, were successful.
S
I
S
S
AlCl3
75%
57%
We were able to couple 1-bromo-4-tert-butylsulfanylben-
zene (3), with 3-bromothiophene and 2-iodothiophene,
assisted by nickel,20 via a reaction of the in situ prepared
4-tert-butylthiophenylmagnesium bromide. This process
led to sulfides 7 and 8, respectively. Then the S-t-butyl
moiety was selectively removed by treatment with alumi-
num trichloride followed by hydrolysis,18b providing 4-
(thien-3-yl)- (9)21 and 4-(thien-2-yl)benzenethiol (10), re-
spectively. Derivative 9 was found to form a polymeriz-
able monolayer on gold surface.21
SH
S-t-Bu
8
10
Scheme 2
Five p-bromothiophenolate derivatives were tested as pre-
cursors for monolayer self-assembly onto a gold substrate.
Adsorption was achieved by immersing a previously
cleaned gold film19 in a dilute solution (1 mM) of the com-
pound to be tested in 0.1 M ethanolic KOH. The film was
S
S
S
2
S
1) thiourea
2) NaOH
HBr
75%
Br
64%
61%
Br
OTBDMS
17
Br
15
SH
S
13
S
S
OR
11 R = H
12 R = TBDMS
2
1) thiourea
2) NaOH
S
Br
HBr
72%
60%
66%
OTBDMS
Br
SH
14
18
16
Scheme 3
Synthesis 2004, No. 14, 2283–2288 © Thieme Stuttgart · New York

PAPER
Sulfides and Thiols as Precursors for Self-Assembled Monolayers on Gold
2285
were dried using Na2SO4 and solvents were subsequently removed
by rotary evaporation.
We were particularly interested in those thiols and other
sulfides having more flexibility at the anchoring position
as this would enhance their utility to material science. To
this end, benzyl sulfides 17 and 18 were prepared as
shown in Scheme 3. Here, the known TBDMS ether 1322
was directly transformed into the corresponding benzyl
bromide 15 with HBr in acetic acid while subsequent sub-
stitution by thiourea, followed by hydrolysis, gave the de-
sired thiol 17. The isomeric 2-thienyl derivative 18 was
obtained from the same coupling reaction, this time with
2-bromothiophene.
1-Bromo-4-tert-butylsulfanylbenzene (3)
To a 100 mL flask containing glacial AcOH (46 mL) was added
60% HClO4 (10 mL), followed by Ac2O (8 mL). The stirred solu-
tion was cooled in an ice bath and 4-bromothiophenol (1; 6.03 g,
31.89 mmol) was added with stirring. This was followed by the ad-
dition of t-BuOH (6 mL, 63.79 mmol). The TLC (eluent: petroleum
ether) indicated the reaction was complete after 3 h, nonetheless the
reaction mixture was stirred overnight. However, H2O (60 mL) and
Et2O (60 mL) were added to the mixture and the phases separated.
The aqueous phase was extracted with Et2O (2 × 60 mL) and the
combined organic phases were washed with 20% aq NaOH until al-
kaline and then were washed with H2O until neutral. The organic
layers were dried (Na2SO4) and were rota-evaporated, leaving a yel-
low oil. The crude oil was vacuum distilled under vacuum to give a
colorless liquid; bp 140–145 °C/10 mm Hg; yield: 6.4 g (82%).
IR (film): 3072, 2961, 1468, 1384, 1363, 730 cm–1.
1H NMR (CDCl3): d = 1.28 [(s, 9 H, (CH3)3C], 7.46 (dd, 2 H,
J = 6.3, 2.1 Hz, H-2,6), 7.39 (dd, 2 H, J = 6.6, 2.1 Hz, H-3,5).
13C NMR (CDCl3): d = 30.84 [(CH3)3C], 46.09 [(CH3)3C], 123.42
(C-1), 131.61 (C-2,6), 131.80 (C-4), 138.88 (C-3,5).
Thiols with C-5 and C-10 chains and having a peripheral
2- or a 3-thienyl heterocycle were prepared using an
adapted literature procedure, which provided intermedi-
ates bromides 19–22.23–26 Substitution of the bromide
function by a thiol was accomplished as described above
providing thienylalkane thiols 23–26 (Scheme 4).
S
S
(CH2)n
Br
Br
(CH2)n
23 n = 5
HS
HS
1) thiourea
2) NaOH
19 n = 5
20 n = 10
GC/MS: m/z (%) = 190 (95), 189 (12), 188 (93), 109 (42), 108 (35),
57 (100), 41 (34) 29 (18).
24 n = 10
65–70%
S
1-Bromo-4-triphenylmethylsulfanylbenzene (4)
(CH2)n
S
(CH2)n
Compound 4 was prepared from triphenylmethanol (390 mg, 1.5
mmol) and 1 (189 mg, 1 mmol) using the procedure for the synthe-
sis of 3. Purification by chromatography (dissolved in a minimal
amount of CH2Cl2 and eluted with petroleum ether) gave 4 (88%
378 mg) as a white solid; yield: 378 mg (88%); mp 190 °C.
21 n = 5
22 n = 10
25 n = 5
26 n = 10
Scheme 4
IR (film): 3049, 747, 700 cm–1.
Melting points were determined with a Fisher-Johns melting point
apparatus and are uncorrected. IR spectra were recorded on a Per-
kin-Elmer 1600 FTIR instrument. 1H NMR spectra were recorded
using a Varian 300 MHz or on a Bruker AMX 2-500 MHz spec-
trometer. 13C NMR spectra were recorded at 75 or 125 MHz respec-
1H NMR (CDCl3): d = 7.13 (dd, 2 H, J = 6.8, 1.5 Hz, H-2,6), 6.80
(dd, 2 H, J = 6.8, 1.5 Hz, H-3,5), 7.42–7.38 (m, 6 H, H-2¢,6¢), 7.26–
7.20 (m, 9 H, H-3¢,5¢).
13C NMR (CDCl3): d = 70.91 [(Ph)3C], 122.16 (C-1), 126.82 (3 C,
C-4¢), 127.75 (6 C, C-2¢,6¢), 129.90 (C-3,5), 131.16 (6 C, C-3¢,5¢),
133.62 (C-4), 135.79 (C-2,6), 144.17 (3 C, C-1¢).
1
tively. Chemical shifts are reported in parts per million (d). H
Chemical shifts in CDCl3 were referenced to the residual CHCl3
(7.27 ppm); 13C chemical shifts were referenced to the solvent
(CDCl3, 77.03 ppm). Mass spectra were obtained using a GC-MS
(GCD plus gas chromatography-electron ionization detector, HPG
1800A GCD system) equipped with a 5% cross-linked Ph Me sili-
cone HP 19091 J-433 column. Elemental analyses were carried out
at the chemistry department of the Université de Montréal, Mon-
tréal, P.Q., Canada, on a Fisons Instrument SPA, model EA1108.
TLC was performed on silica gel F254 (E. Merck precoated glass
plates and visualized by UV irradiation or subjecting the plates to a
5% H2SO4–EtOH solution followed by heating. Separations were
carried out on silica gel (7749 Merck) using circular chromatogra-
phy (chromatotron®, model 7924, Harrison Research). 2-, 3-Bro-
mothiophene, 4-bromobenzenethiol (1), 4-bromothioanisole (2), (2-
trimethylsilyl)ethoxymethyl chloride, triphenylmethanol, and 4-
methoxyphenol were obtained from Aldrich Chemical Co. and were
used without further purification. 2-tert-Butylsulfanylnaphthalene
was obtained from AsInEx Express Gold Collection. 4-Nitro-tert-
butylsulfanylbenzene,18b compounds 12 and 1322as wells as the bro-
mides 19, 2023 and 21, 2226 were synthesized as previously reported.
Solvents were dried by distillation from drying agents as follows:
THF and Et2O (sodium/benzophenone), CH2Cl2 (P2O5), Et3N and
pyridine (CaH2). Petroleum ether used had bp 35–60 °C. All reac-
tions involving organometallic reagents and liquid salt syntheses
were carried out under dry N2. After reaction work-up, solutions
Anal Calcd for C25H19BrS: C, 69.61; H, 4.44; S, 7.43. Found: C,
69.66; H, 4.18; S, 7.05.
[2-(4-Bromophenylsulfanylmethoxy)ethyl]trimethylsilane (6)
4-Bromothiophenol (1; 486 mg, 2.57 mmol) and (2-trimethylsi-
lyl)ethoxymethyl chloride (442.7 mg, 2.66 mmol) were dissolved in
anhyd Et2O (30 mL). Et3N (470 mL, 3.37 mmol) was then added,
and the solution was stirred at r.t. After 2 h, the solvent was evapo-
rated, H2O (25 mL) and CH2Cl2 (25 mL) were added. The phases
were separated and the aqueous layer was extracted with CH2Cl2 (2
× 10 mL). The combined extracts were washed with H2O (3 × 10
mL), dried (Na2SO4) and rota-evaporated leaving a colorless vis-
cous liquid. Purification by chromatography (eluent: petroleum
ether) gave 6 as a colorless oil; yield: 697 mg (88%).
IR (film): 2951, 2891, 1248, 834, 811 cm–1.
1H NMR (CDCl3): d = 0.23 [s, 9 H, Si(CH3)3], 0.95 (t, 2 H, J = 8.2
Hz, CH2Si), 3.69 (t, 2 H, J = 8.2 Hz, CH2O), 4.98 (s, 2 H, SCH2O),
7.41 (dd, 2 H, J = 6.6, 2.2 Hz, H-2,6), 7.34 (dd, 2 H, J = 6.6, 2.2 Hz,
H-3,5).
13C NMR (CDCl3): d = –1.14 [Si(CH3)3], 17.69 (CH2Si), 66.05
(CH2O), 75.29 (SCH2O), 120.43 (C-1), 131.38 (C-2,6), 131.89 (C-
3,6), 135.61 (C-4).
GC/MS: m/z (%) = 103 (15), 122 (11), 73 (100).
Synthesis 2004, No. 14, 2283–2288 © Thieme Stuttgart · New York

2286
M. Touaibia et al.
PAPER
Anal Calcd for C12H19BrOSSi: C, 45.14; H, 5.95. Found: C, 45.23;
H, 6.16.
13C NMR (CDCl3): d = 120.09 (C-2¢), 126.06 (C-4¢), 126.34 (C-5¢),
127.04 (C-3,5), 129.34 (C-4), 129.86 (C-2,6), 133.45 (C-1), 141.50
(C-3¢).
3-(4-tert-Butylsulfanylphenyl)thiophene (7)
GC/MS: m/z (%) = 193 (M+ + 1, 16), 192 (M+, 100), 191 (47), 160
1-Bromo-4-tert-butylsulfanylbenzene (3; 400 mg, 1.63 mmol) and
anhyd THF (2 mL) were added, under N2, to a vessel containing Mg
turnings (47.6 mg, 1.96 mmol) and THF (10 mL) and the mixture
was refluxed for 6 h. The Grignard solution was subsequently trans-
ferred dropwise (over 30 min) to a second flask containing
Ni(dppp)Cl2 (26.5 mg, 3 mol%) and 3-bromothiophene (320.2 mg,
1.79 mmol), which was then refluxed for 12 h. After this, the reac-
tion mixture was hydrolyzed by adding it to 10% aq HCl (10 mL)
combined with ice water (10 mL), which was followed by the addi-
tion of Et2O (10 mL). The phases were separated and the aqueous
layer was extracted with Et2O (2 × 10 mL). The combined organic
phases were washed with H2O until neutral and dried (Na2SO4). The
solvent was removed under reduced pressure leaving a yellow resi-
due which was purified by chromatography (dissolved in a minimal
amount of CH2Cl2 and eluted with petroleum ether to give 7 as a
white solid; yield: 275 mg (68%); mp 96 °C.
IR (KBr): 3098, 2962, 1670, 1457, 1363, 1168, 689 cm–1.
1H NMR (CDCl3): d = 1.32 [s, 9 H, (CH3)3C], 7.41 (d, 2 H, J = 2.2
Hz, H-4¢,5¢), 7.50 (t, 1 H, J = 2.2 Hz, H-2¢), 7.57 (br s, 4 Harom).
13C NMR (CDCl3): d = 30.94 [(CH3)3C], 46.05 [(CH3)3C], 120.77
(C-2¢), 126.17 (C-4¢), 126.34 (C-3,5), 126.42 (C-5¢), 131.39 (C-1),
136.10 (C-4), 137.86 (C-2,6), 141.52 (C-3¢).
(14), 147 (42), 115 (20).
Anal Calcd for C10H8S2: C, 62.46; H, 4.19. Found: C, 62.24; H,
4.05.
4-(Thien-2-yl)benzenethiol (10)
Compound 10 was prepared from 8 (250 mg, 1.01 mmol) following
the same protocol as for 9 which gave 10 as a yellow solid; yield:
125 mg (65%). This solid was then recrystallized from Et2O; mp
110 °C.
IR (KBr): 3451, 3066, 2551, 1104, 811, 691 cm–1.
1H NMR (CDCl3): d = 3.49 (br s, 1 H, SH), 7.07 (dd, 1 H, J = 5.0,
3.7 Hz, H-4¢), 7.28 (s, 2 H, H-3¢,5¢), 7.29 (d, 2 H, J = 8.5 Hz, H-2,6),
7.49 (d, 2 H, J = 8.5 Hz, H-3,5).
13C NMR (CDCl3): d = 122.95 (C-3¢), 124.71 (C-5¢), 126.50 (C-
3,5), 128.04 (C-4¢), 129.82 (C-2,6 + C-1), 132.02 (C-4), 143.65 (C-
2¢).
GC/MS: m/z (%) = 192 (M+, 100), 191 (47), 160 (14), 147 (42) 115
(20), 96 (15).
Anal Calcd for C10H8S2: C, 62.46; H, 4.19. Found: C, 62.82; H,
3.64.
GC/MS: m/z (%) = 248 (M+, 12), 193 (14), 192 (100), 191 (22), 147
(22), 57 (14).
[(4-Bromobenzyl)oxy](tert-butyldimethyl)silane (12)
Compound 12 was prepared, as previously described, in 93%
yield.22
2-(4-tert-Butylsulfanylphenyl)thiophene (8)
IR (film): 2950, 2928, 2856, 1593, 1486, 1257, 1087, 1011, 838,
776 cm–1.
Compound 8 was prepared from 2-iodothiophene (1.18 g, 5.6
mmol) and 3 (1.25g, 5.1 mmol) using the procedure for the synthe-
sis of 7. Purification by chromatography (dissolved in a minimum
amount of CH2Cl2 and eluted with petroleum ether) gave 8 (58%
0.74 g) as a yellow solid; mp 105 °C.
tert-Butyldimethyl[4-thien-3-ylbenzyl)oxy]silane (13)
Compound 13 was prepared according to the literature22 and the 1H
NMR, 13C NMR and GC/MS were found to be identical to those re-
ported; mp 64 °C.
IR (KBr): 3010, 2961, 1592, 1399, 1363, 1166, 696 cm–1.
1H NMR (CDCl3): d = 1.32 [s, 9 H, C(CH3)3], 7.10 (dd, 1 H, J = 5.0,
3.7 Hz, H-4¢), 7.32 (dd, 1 H, J = 5.0, 0.8 Hz, H-5¢), 7.36 (dd, 1 H,
J = 3.7, 0.8 Hz, H-3¢), 7.54 (d, 2 H, J = 8.5 Hz, H-2,6), 7.59 (d, 2 H,
J = 8.5 Hz, H-3,5).
13C NMR (CDCl3): d = 30.94 [(CH3)3C], 46.19 [(CH3)3C], 123.54
(C-3¢), 125.30 (C-5¢), 125.73 (C-3,5), 128.13 (C-4¢), 131.77 (C-1),
134.70 (C-4), 137.89 (C-2,6), 143.56 (C-2¢).
IR (KBr): 3097, 2950, 2929, 2856, 1467, 1380, 1365, 1253, 1096,
1056, 839, 787 cm–1.
tert-Butyldimethyl[(4-thien-2-ylbenzyl)oxy]silane (14)
This compound was obtained as a white solid from the procedure
established for 13, this time using 12 (3.5 g, 11.6 mmol); yield: 2.1
g (66%); mp 50 °C.
GC/MS: m/z = 248 (M+, 12), 193 (14), 192 (100), 191 (22), 147
(18), 57 (14).
IR (KBr): 3075, 2954, 2927, 2854, 1500, 1460, 1376, 1256, 1094,
852, 830, 776 cm–1.
1H NMR (CDCl3): d = 0.13 (s, 6 H, 2 CH3), 0.97 [s, 9 H, C(CH3)3],
4.77 (s, 2 H, CH2), 7.09 (dd, 2 H, J = 5.0, 3.6 Hz, H-4¢), 7.28 (dd, 1
H, J = 5.0, 1.2 Hz, H-5¢), 7.31 (dd, 1 H, J = 3.6, 1.2 Hz, H-3¢), 7.35
(dt, 2 H, J = 8.4, 1.9 Hz, H-3,5), 7.60 (dt, 2 H, J = 8.4, 1.9 Hz, H-
2,6).
13C NMR (CDCl3): d = –5.23 [Si(CH3)2], 18.42 [SiC(CH3)3], 25.95
[SiC(CH3)3], 64.68 (OCH2), 122.83 (C-3¢), 124.50 (C-5¢), 125.80
(C-3,5), 126.65 (C-2,6), 127.94 (C-4¢), 133.05 (C-4), 140.79 (C-1),
144.41 (C-2¢).
4-(Thien-3-yl)benzenethiol (9)
To a 25 mL ice-cooled flask containing a solution of AlCl3 (88.7
mg, 0.67 mmol) in toluene (10 mL), was added dropwise a solution
of 3-(4-tert-butylsulfanylphenyl)thiophene (7; 275 mg, 1.11 mmol)
in toluene (3 mL). The resultant red reaction mixture was stirred at
r.t. for 30 min and then poured into ice (20 g). The aqueous phase
was extracted with toluene (2 × 20 mL) and the combined organic
phases were treated with 20% aq NaOH (3 × 15 mL) until alkaline
and then with 12 N HCl until a white precipitate had formed. This
solid was filtered and washed with cold H2O to afford 9 as a white
solid; yield: 185 mg (87%), which was then recrystallized from
Et2O; mp 138 °C.
GC/MS: m/z (%) = 304 (M+), 247 (17), 175 (5), 174 (13), 173 (100).
3-[4-(Bromomethyl)phenyl]thiophene (15)
A solution of tert-butyldimethyl[4-thien-3-ylbenzyl)oxy]silane (13;
700 mg, 2.30 mmol) in glacial AcOH (5 mL) was added to a chilled
vessel containing glacial AcOH (10 mL) and HBr (10 mL, 33% in
AcOH). The resulting mixture was stirred at 5 °C for 1 h, diluted
with H2O (50 mL) and extracted with Et2O (3 × 25 mL). The com-
bined organic phases were washed to neutrality with 5% aq NaOH
IR (KBr): 3357, 3100, 2554, 1106, 760 cm–1.
1H NMR (CDCl3): d = 3.49 (br s, 1 H, SH), 7.31 (dd, 2 H, J = 6.8,
1.8 Hz, H-2,6), 7.36 (dd, 1 H, J = 4.9, 1.4 Hz, H-5¢), 7.39 (dd, 1 H,
J = 4.9, 2.7 Hz, H-4¢), 7.42 (dd, 1 H, J = 2.7, 1.4 Hz, H-2¢), 7.48 (dd,
2 H, J = 6.8, 1.8 Hz, H-3,5).
Synthesis 2004, No. 14, 2283–2288 © Thieme Stuttgart · New York

PAPER
Sulfides and Thiols as Precursors for Self-Assembled Monolayers on Gold
2287
(4 × 50 mL), dried (Na2SO4) and rota-evaporated. The residue was
chromatographed with petroleum ether to yield 15 as white solid;
yield: 438 mg (75%); mp 106 °C.
13C NMR (CDCl3): d = 28.67 (CH2SH), 123.07 (C-3¢), 124.78 (C-
5¢), 126.21 (C-3,5), 128.0 (C-4¢), 128.55 (C-2,6), 133.25 (C-4),
140.38 (C-1), 143.98 (C-2¢).
IR (KBr): 3100, 2932, 1655, 1565, 1426, 1383, 1203, 1122, 836,
817, 728 cm–1.
GC/MS: m/z (%) = 206 (M+, 19), 174 (17), 173 (100), 171 (9), 128
(11).
The 1H NMR, 13C NMR and GC/MS were identical to those report-
Anal Calcd for C11H10S2: C, 64.04; H, 4.89; S, 31.08. Found: C,
63.86; H, 4.42, S, 30.85.
ed.22
2-[4-(Bromomethyl)phenyl]thiophene (16)
5-(Thien-3-yl)pentane-1-thiol (23)
The use of 14 (500 mg, 1.64 mmol) in the procedure for 15 followed
by purification of the crude product on silica gel gave 16 as a white
solid; yield: 300 mg (72%); mp 62 °C.
This product was obtained using the same procedure as for 17, this
time with 3-(5-bromopentyl)thiophene (19; 1.16 g, 4.97 mmol) and
thiourea (757 mg, 9.95 mmol) in abs EtOH as a pungent colorless
oil; yield: 570 mg (62%).
IR (KBr): 3067, 2962, 1607, 1501, 1426, 1227, 1208, 816, 702 cm–
.
IR (film): 3358, 3101, 2929, 2854, 2562, 1460, 1080, 834, 775 cm–1.
1
1H NMR (CDCl3): d = 4.53 (s, 2 H, CH2), 7.10 (dd, 1 H, J = 5.2, 3.6
Hz, H-4¢), 7.31 (dd, 1 H, J = 5.2, 1.1 Hz, H-5¢), 7.33 (dd, 1 H,
J = 3.6, 1.1 Hz, H-3¢), 7.41 (d, 2 H, J = 8.1 Hz, H-3,5), 7.60 (d, 2 H,
J = 8.1 Hz, H-2,6).
13C NMR (CDCl3): d = 33.28 (CH2Br), 123.49 (C-3¢), 125.21 (C-
5¢), 126.22 (C-3,5), 128.09 (C-4¢), 129.61 (C-2,6), 134.54 (C-1),
136.84 (C-4), 143.60 (C-2¢).
1H NMR (CDCl3): d = 1.34 (t, J = 7.8 Hz, 1 H, SH), 1.39–1.50 (m,
2 H, H-3), 1.65 (quin, J = 7.6 Hz, 2 H, H-4 or 2), 1.66 (quin, J = 7.4
Hz, 2 H, H-2 or 4), 2.54 (q, J = 7.4 Hz, 2 H, H-1), 2.65 (t, J = 7.6
Hz, 2 H, H-5), 6.93 (dd, J = 5.0, 1.2 Hz, 1 H, H-5¢), 6.95 (dd,
J = 3.1, 1.2 Hz, 1 H, H-2¢), 7.25 (dd, J = 5.0, 3.1 Hz, 1 H, H-4¢).
13C NMR (CDCl3): d = 24.52 (C-1), 27.96 (C-3), 29.95 (C-5), 30.08
(C-4), 33.81 (C-2), 119.92 (C-2¢), 125.18 (C-5¢), 128.16 (C-4¢),
142.76 (C-3¢).
GC/MS: m/z (%) = 254 (81BrM+, 3) 252 (79BrM+, 3), 174 (24), 173
(100), 128 (9), 87 (10).
GC/MS: m/z (%) = 186 (M+, 32), 153 (11), 98 (55), 97 (100).
Anal Calcd For C9H14S2: C, 58.01; H, 7.57; S, 34.41. Found: C,
57.93; H, 7.79; S, 34.27.
(4-Thien-3-ylphenyl)methanethiol (17)
A mixture of 3-[4-(bromomethyl)phenyl]thiophene (15; 583 mg,
2.30 mmol) and thiourea (351 mg, 4.60 mmol) in abs EtOH (20 mL)
was refluxed with stirring overnight and then poured into 10% aq
NaOH (15 mL). The resultant mixture was refluxed with stirring for
4 h, cooled to r.t., neutralized with 10% HCl (10 mL) and extracted
with CH2Cl2 (3 × 20 mL). The combined extracts were washed with
H2O (3 × 10 mL), dried (Na2SO4) and rota-evaporated leaving a col-
orless viscous liquid. Purification by chromatography (eluant: pe-
troleum ether) afforded 17 as a pungent white solid; yield: 289 mg
(61%); mp 94 °C.
10-(Thien-3-yl)decane-1-thiol (24)
The final product was obtained by mixing 3-(10-bromode-
cyl)thiophene (20; 1.11 g, 3.66 mmol) with thiourea (557 mg, 7.32
mmol) in abs EtOH, using the procedure described for 17; yield:
536 mg (57%); pungent colorless oil.
IR (film): 3103, 2922, 2852, 2566, 1465, 1152, 772, 632 cm–1.
1H NMR (CDCl3): d = 1.29–1.38 (m, 12 H, H-3 to H-8), 1.34 (t,
J = 7.7 Hz, 1 H, SH), 1.63 (quin, J = 7.1 Hz, 4 H, H-2,9), 2.53 (q,
J = 7.3 Hz, 2 H, H-1), 2.63 (t, J = 7.6 Hz, 2 H, H-10), 6.93 (dd,
J = 3.0, 1.1 Hz, 1 H, H-2¢), 6.94 (dd, J = 5.0, 1.1 Hz, 1 H, H-4¢), 7.25
(dd, J = 5.0, 3.0 Hz, 1 H, H-5¢).
13C NMR (CDCl3): d = 24.64 (C-1), 28.35 (C-3), 29.04 (C-4), 29.29
(C-8), 29.41 and 29.47 (C-5, C-6, C-7), 30.26 (C-10), 30.53 (C-9),
34.03 (C-2), 119.74 (C-2¢), 125.02 (C-5¢), 128.26 (C-4¢), 143.22 (C-
3¢).
IR (KBr): 3036, 2938, 2255, 1670, 1554, 1123, 855, 779 cm–1.
1H NMR (CDCl3): d = 1.79 (t, 1 H, J = 7.6 Hz, SH), 3.78 (d, 2 H,
J = 7.6 Hz, CH2S), 7.37 (dt, 2 H, J = 8.5, 2.0 Hz, H-2,6), 7.39 (d, 1
H, J = 1.7 Hz, H-4¢), 7.4 (d, 1 H, J = 2.7 Hz, H-5¢), 7.45 (dd, 1 H,
J = 2.6, 1.8 Hz, H-2¢), 7.34 (dt, 2 H, J = 8.2, 2.0 Hz, H-3,5).
13C NMR (CDCl3): d = 28.69 (CH2SH), 120.24 (C-2¢), 126.24 (C-
4¢), 126.26 (C-5¢), 126.72 (C-3,5), 128.48 (C-2,6), 134.70 (C-4),
140.00 (C-1), 141.90 (C-3¢).
GC/MS: m/z (%) = 256 (M+, 15), 111 (15), 98 (100), 97 (47).
GC/MS: m/z (%) = 206 (M+, 15), 174 (35), 173 (M+ – SH, 100), 171
(10), 128 (13).
Anal Calcd for C14H24S2: C, 65.57; H, 9.43; S, 25.00. Found: C,
65.39; H, 9.58; S, 24.77.
Anal Calcd for C11H10S2: C, 64.04; H, 4.89; S, 31.08. Found: C,
63.83; H, 4.40; S, 30.41.
5-(Thien-2-yl)pentane-1-thiol (25)
Compound 25 was prepared from 2-(5-bromopentyl)thiophene (21;
1 g, 4.3 mmol) following the procedure for 17. It was obtained as a
pungent colorless oil; yield: 0.5 g (63%).
(4-Thien-2-ylphenyl)methanethiol (18)
Compound 18 was obtained using the procedure for 17, this time
with 2-[4-(bromomethyl)phenyl]thiophene (16; 1.55 g, 6.13 mmol)
and thiourea (933 mg, 12.25 mmol). Product 18 was obtained as a
pungent white solid; yield: 750 mg (60%); mp 162 °C.
IR (film): 3068, 2928, 2853, 2564, 1459, 1439, 1254, 849, 822, 694
cm–1.
1H NMR (CDCl3): d = 1.35 (t, J = 7.8 Hz, 1 H, SH), 1.42–1.53 (m,
2 H, H-3), 1.62–1.76 (m, 4 H, H-2,4), 2.54 (q, J = 7.3 Hz, 2 H, H-
1), 2.85 (td, J = 7.8, 0.6 Hz, 2 H, H-5), 6.79 (dq, 1 H, J = 3.4, 1.2
Hz, 1 H, H-3¢), 6.93 (dd, 1 H, J = 5.1, 3.4 Hz, 1 H, H-4¢), 7.12 (dd,
1 H, J = 5.1, 1.2 Hz, 1 H, H-5¢).
13C NMR (CDCl3): d = 24.80 (C-1), 27.74 (C-3), 29.72 (C-5), 31.17
(C-4), 33.70 (C-2), 122.84 (C-5¢), 124.02 (C-3¢), 126.65 (C-4¢),
145.29 (C-2¢).
IR (KBr): 3063, 2919, 2550, 1905, 1659, 1604, 1495, 1423, 1250,
1110, 820 cm–1.
1H NMR (CDCl3): d = 1.79 (t, 1 H, J = 7.6 Hz, SH), 3.77 (d, 2 H,
J = 7.6 Hz, CH2), 7.09 (dd, 1 H, J = 5.0, 3.6 Hz, H-4¢), 7.28 (dd, 1
H, J = 5.0, 1.1 Hz, H-5¢), 7.31 (dd, 1 H, J = 3.6, 1.1 Hz, H-3¢), 7.34
(dt, 2 H, J = 8.5, 2.1 Hz, H-2,6), 7.57 (dt, 2 H, J = 8.5, 2.1 Hz, H-
3,5).
GC/MS: m/z (%) = 186 (M+, 16), 123 (16), 111 (12), 98 (18), 97
(100).
Synthesis 2004, No. 14, 2283–2288 © Thieme Stuttgart · New York

2288
M. Touaibia et al.
PAPER
Anal Calcd for C9H14S2: C, 58.01; H, 7.57; S, 34.41. Found: C,
57.76; H, 7.79; S, 34.31.
Rubinstein, I. Langmuir 1993, 9, 2974.
(9) Hasan, M.; Bethel, D.; Brust, M. J. Am. Chem. Soc. 2002,
124, 1132.
10-(Thien-2-yl)decane-1-thiol (26)
(10) (a) De Boer, B.; Meng, H.; Perepichka, D. F.; Zheng, J.;
Frank, M. M.; Chabal, Y. J.; Bao, Z. Langmuir 2003, 19,
4272. (b) Tour, J. M.; Jones, L. I. I.; Pearson, D. L.; Lamba,
J. J. S.; Burgin, T. P.; Whitesides, G. M.; Allara, D. L.;
Parikh, A. N.; Atre, S. J. Am. Chem. Soc. 1995, 117, 9529.
(11) Nuzzo, R. G.; Allara, D. L. J. Am. Chem. Soc. 1983, 105,
4481.
The synthetic procedure for 17, this time from 2-(10-bromode-
cyl)thiophene (22; 620 mg, 2.04 mmol) gave 26 as a pungent color-
less oil; yield: 350 mg (67%).
IR (film): 2923, 2851, 2359, 1458, 1438, 1236, 849, 818, 690 cm–1.
1H NMR (CDCl3): d = 1.29–1.55 (m, 13 H, SH, H-3 to H-8), 1.68
(quin, J = 7.2 Hz, 4 H, H-2,9), 2.69 (t, J = 7.2 Hz, 2 H, H-1), 2.82
(t, J = 7.7 Hz, 2 H, H-10), 6.78 (dt, J = 3.3, 1.1 Hz, 1 H, H-3¢), 6.92
(dd, J = 4.8, 3.3 Hz, 1 H, H-4¢), 7.11 (dt, J = 4.8, 1.1 Hz, 1 H, H-5¢).
13C NMR (CDCl3): d = 28.50 (C-1), 29.09 (C-3), 29.20, 29.31 and
29.45 (4 CH2, C4 to C-8), 29.90 (C-10), 31.78 (C-9), 39.17 (C-2),
122.70 (C-5¢), 123.87 (C-3¢), 126.61 (C-4¢), 145.83 (C-2¢).
(12) Danisman, M. F.; Casalis, L.; Baracco, G.; Scoles, G. J.
Phys. Chem. B 2002, 106, 11771.
(13) (a) Zhong, C. J.; Porter, M. D. J. Am. Chem. Soc. 1994, 116,
11616. (b) Zhang, M.; Anderson, M. R. Langmuir 1994, 10,
2807. (c) Beulen, M. W.; Huisman, B. H.; van der Heijden,
P. A.; van Veggel, F. C. J. M.; Simons, M. G.; Biemond, E.
M. E. F.; de Lange, P. J.; Reinhoudt, D. N. Langmuir 1996,
12, 6170. (d) Troughton, E. B.; Bain, C. D.; Whitesides, G.
M.; Nuzzo, R. G.; Allara, D. L.; Porter, M. D. Langmuir
1988, 4, 365.
GC/MS: m/z (%) = 256 (M+, 10), 111 (29), 97 (100).
Anal Calcd for C14H24S2: C, 65.57; H, 9.43; S, 25.00. Found: C,
65.18; H, 9.42; S, 25.06.
(14) Russell, G. A.; Ngoviwatchai, P.; Tashtoush, H. I.; Pla-
Dalmau, A.; Khanna, R. K. J. Am. Chem. Soc. 1988, 110,
3530.
Acknowledgment
(15) Barañano, D.; Hartwig, J. F. J. Am. Chem. Soc. 1995, 117,
2937.
M.T. and L.B. acknowledge the financial contribution of UQAM
for a fellowship. This work was also partially supported by Rese-
arch Grants from the Natural Sciences and Engineering Research
Council of Canada (NSERC). Special thanks to K. Walsh for provi-
ding assistance with the preparation of the manuscript.
(16) Li, G. Y. Angew. Chem. Int. Ed. 2001, 40, 1513.
(17) (a) Horton, J. R.; Stamp, L. M.; Routledge, A. Tetrahedron
Lett. 2000, 41, 9181. (b) Durden, J. A. Jr. US Patent
4304735, 1981; Chem. Abstr. 1982, 96, 85250. (c) Stuhr-
Hansen, N. Synth. Commun. 2003, 33, 641.
(18) (a) These examples were chosen to illustrate the generality
of our method. The physical and spectroscopic data for these
S-t-butyl sulfides were identical to those observed in the
literature. (b) Arai, I.; Yamaguchi, T.; Hida, Y. WO. Patent
0014060, 2000; Chem. Abstr. 2000, 222336.
References
(1) Vuillaume, D.; Lenfant, S. Microelectron. Eng. 2003, 70,
539.
(2) Xu, T.; Peterson, I. R.; Lakshmikantham, M. V.; Metzger, R.
M. Angew. Chem. Int. Ed. 2001, 40, 1749.
(19) Rifai, S.; Lopinski, G. P.; Ward, T. P.; Wayner, D. D. M.;
Morin, M. Langmuir 2003, 19, 8916.
(3) Waldeck, D. N. Science 1993, 261, 567.
(4) (a) Chen, J.; Lee, T.; Su, J.; Wang, W.; Reed, M. A. In
Encyclopedia of Nanoscience and Nanotechnology; Vol. 5,
Nalwa, H. S., Ed.; American Scientific Publisher: Stevenson
Ranch, California, 2004, 633. (b) Tour, J. M. Molecular
Electronics: Commercial Insights, Chemistry, Devices,
Architecture and Programming; World Scientific
Publishing Co.: Singapore, 2003.
(5) Gui, J. Y.; Stern, D. A.; Frank, D. G.; Lu, F.; Zapien, D. C.;
Hubbard, A. T. Langmuir 1991, 7, 955.
(6) Carron, K. T.; Hurley, L. G. J. Phys. Chem. 1991, 95, 9979.
(7) Bryant, M. A.; Joa, S. L.; Pemberton, J. E. Langmuir 1992,
8, 753.
(20) Tamao, K.; Kodama, S.; Nakajima, I.; Kumada, M.; Minato,
A.; Suzuki, K. Tetrahedron 1982, 38, 3347.
(21) Touaibia, M.; Benny, F.; Pilon, C.; Courtel, F.; Breau, L.;
Morin, M.; J. Phys. Chem. B; submitted, 2004.
(22) Naudin, E.; Ho, H.; Bonin, M. A.; Breau, L.; Bélanger, D.
Macromolecules 2002, 35, 4983.
(23) Baeuerle, P.; Wuerthner, F.; Heid, S. Angew. Chem., Int. Ed.
Engl. 1990, 29, 419.
(24) Buckel, F.; Persson, P.; Effenberger, F. Synthesis 1999, 953.
(25) Heejoon, A.; Myunghwan, K.; Sandman, D. J.; Whitten, J. E.
Langmuir 2003, 19, 5303.
(26) Lam, K. L. US Patent 6166003, 2000; Chem. Abstr. 2000,
133, 177092.
(8) (a) Frey, S.; Stadler, V.; Heister, K.; Eck, W.; Zharnikov,
M.; Grunze, M.; Zeysing, B.; Terfort, A. Langmuir 2001, 17,
2408. (b) Sabatani, E.; Cohen-Boulakia, J.; Bruening, M.;
Synthesis 2004, No. 14, 2283–2288 © Thieme Stuttgart · New York