Synthesis and Characterization of Two Tritylthio-Derivatives: 1-Bromo-3-Tritylthiopropane and 2-(Tritylthio)-Ethanethiol

Article abstract of DOI:10.1007/s10870-017-0703-1

Abstract: Two tritylthio-based compounds were synthesized: 1-bromo-3-tritylthiopropane 1 and 2-(tritylthio)-ethanethiol 2. They were characterized by infrared, NMR, UV–Vis absorption and fluorescence spectroscopy and single-crystal X-ray diffraction. The

Full text of DOI:10.1007/s10870-017-0703-1

J Chem Crystallogr
DOI 10.1007/s10870-017-0703-1
ORIGINAL PAPER
Synthesis and Characterization of Two Tritylthio-Derivatives:
1-Bromo-3-Tritylthiopropane and 2-(Tritylthio)-Ethanethiol
Rodney A. Tigaa1 · Ana de Bettencourt-Dias1
Received: 22 November 2016 / Accepted: 26 October 2017
© Springer Science+Business Media, LLC 2017
Abstract Two tritylthio-based compounds were synthe-
sized: 1-bromo-3-tritylthiopropane 1 and 2-(tritylthio)-
ethanethiol 2. They were characterized by infrared, NMR,
UV–Vis absorption and fluorescence spectroscopy and
single-crystal X-ray diffraction. The crystals of both com-
pounds crystallize in the monoclinic space group P21/c. The
unit cell dimensions of 1 are a = 7.4072 (9) Å, b = 9.6924
(11) Å, c = 25.652(3) Å, β = 90.023 (2)o, and V = 1841.7
(4) Å3, and of 2 are a = 15.3532 (8) Å, b = 14.1552 (7),
c = 7.8249 (4) Å, β = 94.5239 (8)o, and V = 1695.27 (15)
Å3. The packing structures of 1 and 2 are supported by
weak π−π and hydrogen bond interactions. Both 1 and 2
have absorption maxima at 257 nm, and emission maxima at
314 nm and 313 nm, respectively. The compounds differ by
the presence of the S-H stretching vibration at ~2550 cm−1
in 2 and its absence in 1, as observed in the infrared spectra.
Graphical Abstract Thermal ellipsoid plots of com-
pounds 1 and 2, with thermal ellipsoids at 50% probability.
Electronic supplementary material The online version of
this article (https://doi.org/10.1007/s10870-017-0703-1) contains
supplementary material, which is available to authorized users.
* Ana de Bettencourt-Dias
abd@unr.edu
1
Department of Chemistry, University of Nevada, Reno,
NV 89557, USA
Vol.:(0123456789)
1 3

J Chem Crystallogr
the surface energy of NPs and stabilize them [3]. Thiol-
containing compounds can also be used as a sulfur source,
which is especially important in crystal-bound thiol NPs [3].
Furthermore, Hollingsworth and co-workers have shown
that the concentration of thiols used during the surface cap-
ping can either enhance or diminish the photoluminescence
quantum yield of CdSe/ZnS core/shell NPs [9]. Compared
to free thiols, less reactive thioethers compounds such as
dendritic thioethers have been used to stabilize and control
the size of gold NPs [10]. As a result of the critical role that
these sulfur-containing compounds play in NP chemistry, it
is important to understand the structural and photophysical
properties of thiol building blocks such as tritylthio-alkyl
groups. To address this, we synthesized 1-bromo-3-tritylth-
iopropane, 1, following a procedure reported by Jagadish
and co-workers, and substituted the alkyl-bromide to gener-
ate 2-(tritylthio)-ethanethiol, 2 [4, 11]. We avoided the use
of thiiranes in the synthesis of 2 by modifying a procedure
developed by Chan and co-workers [12]. We then charac-
terized these two compounds by a combination of FT-IR,
NMR, UV–Vis absorption and fluorescence spectroscopy,
as well as single-crystal X-ray diffraction.
Experimental
All the chemicals used were of analytical grade, and the
solvents were dried by standard methods and degassed with
nitrogen prior to use. Unless otherwise noted, the reactions
were run under a nitrogen atmosphere.
Syntheses
Synthesis of 1-Bromo-3-Tritylthiopropane 1
5.432 g (19.7 mmol) of triphenyl-methyl-mercaptan and
8.0 mL (78.9 mmol) of 1,3-dibromopropane were dispersed
in 150 mL of acetonitrile and 20.915 g (151 mmol) of anhy-
drous potassium carbonate was added while stirring. After
stirring at room temperature overnight, the mixture was
filtered and the filtrate evaporated under reduced pressure
to yield a yellow oil that was recrystallized from hexanes
to yield 1 as a white powder (5.458 g, 70%). TLC (SiO2,
Keywords Tritylthio-derivatives · UV–Vis absorption ·
Fluorescence and infrared spectroscopy · X-ray diffraction ·
NMR
1
hexane/ethyl acetate, 1:1): Rf = 0.91. H NMR (CDCl3,
400 MHz): δ=7.42 (d, J=7.4 Hz, 6H, o-aryl-H), 7.29 (t,
J=7.5 Hz, 6H, m-aryl-H), 7.22 (t, J=7.1 Hz, 3H, p-aryl-
H), 3.33 (t, J=6.6 Hz, 2H, BrCH2), 2.33 (t, J=7.0 Hz, 2H,
SCH2), and 1.81 (p, J = 6.7 Hz, 2H, CH2CH2CH2) ppm.
13C NMR (CDCl3, 100 MHz): δ=144.73, 129.59, 127.93,
126.70, 32.29, 31.65 and 30.30 ppm.
Introduction
The use of thiol head groups as surface capping agents of
nanoparticles (NPs) is common practice [1–8]. They lower
1 3

J Chem Crystallogr
Synthesis of 2-(Tritylthio)-Ethanethiol 2
UV–Vis Absorption and Fluorescence
1.8 mL (21.4 mmol) of 1,2-ethanedithiol was added to a
10 mL 50% mixture of trifluoroacetic acid/dichlorometh-
ane. 0.250 g (0.63 mmol) of 1 was added and the mixture
stirred at room temperature overnight. The solvent was
removed by vacuum transfer and the concentrated oil re-
dissolved in chloroform (50 mL), followed by washing
with water (3×25 mL) and brine (3×50 mL). The organic
phase was dried over magnesium sulfate, filtered and con-
centrated under reduced pressure to yield a pale-yellow
oil that was purified by flash chromatography in 1:1 Hex/
EtOAc to give 2 as a clear oil (0.111 g, 52%). TLC (SiO2,
1.0×10−4 M stock solutions of each compound were pre-
pared by dissolving the appropriate amount in spectroscopic
grade acetonitrile, and transferring the required amount into
a 1.0 cm pathlength cuvette. Following this, the absorp-
tion spectrum of each compound was acquired on a Perkin
Elmer Lambda 35 UV–Vis spectrometer at 480 nm/min in
the range 600–200 nm at room temperature. The excitation
and emission spectra were recorded on a Horiba Jobin Yvon
Nanolog fluorimeter equipped with a 450 W (Ushio) xenon
lamp. The excitation/emission slits were set at 5/1 nm, with
integration time of 1.0 s and 1 nm increments. The instru-
ment was set to the front face mode at a 22.5° angle in order
to record the emission spectra at 77 K (frozen solution) and
at a 90° angle for measurements at 25.0 0.1 oC.
1
hexane/ethyl acetate, 1:1): Rf = 0.91. H NMR (CDCl3,
400 MHz): δ = 7.42 (d, J = 7.8 Hz, 6H, o-aryl-H), 7.29 (t,
J = 7.5 Hz, 6H, m-aryl-H), 7.22 (m, 3H, p-aryl-H), 2.47
(t, 2H, SCH2), 2.27 (q, J = 7.8 Hz, 2H, CH2SH), 1.42 (t,
J = 8.3 Hz, 1H, SH) ppm. 13C NMR (CDCl3, 100 MHz):
δ = 144.69, 129.57, 127.94, 126.75, 36.09 and 23.89 ppm.
Single-Crystal X-Ray Diffraction
Both compounds yielded X-ray quality single crystals after
recrystallization from acetonitrile. A suitable crystal was
mounted on a glass fiber and placed in the low-temperature
nitrogen stream of a Bruker SMART CCD area detector
diffractometer. A full sphere of data was collected using
graphite-monochromated Mo Kα radiation (λ=0.71073 Å)
source. Multi-scan absorption corrections were applied
using SADABS [13]. The structures were solved by direct
methods and refined by least square methods on F2 using
the SHELXTL program package [14]. The hydrogen atoms
were geometrically added and all the non-hydrogen atoms
refined anisotropically. The structures were deposited with
Spectroscopy
FT-IR
The infrared spectra of the compounds were recorded
using a Nicolet 6700 FT-IR instrument in the range
3500–590 cm−1 at 4 cm−1 resolution with 32 scans in ATR
mode. Before each acquisition, a background spectrum
was acquired to correct for CO2 and H2O interference.
NMR
1H and 13C NMR spectra were recorded using a Varian
NMR instrument operating at 400 MHz, while using deu-
terated chloroform (CDCl3) as solvent and tetramethylsi-
lane (TMS) as a reference.
K2CO3
S
Br
Br
Br
CH3CN
SH
1
S
SH
1,2-ethanedithiol
50% CH2Cl2/TFA
2
Fig. 1 FT-IR spectra of 1 and 2 with the S-H stretch region high-
Scheme 1 Syntheses of 1 and 2
lighted
1 3

J Chem Crystallogr
Fig. 2 1H NMR spectrum of 1 in CDCl3
Fig. 3 1H NMR spectrum of 2 in CDCl3
1 3

J Chem Crystallogr
the Cambridge Crystallographic Database and their refer-
ence numbers are CCDC 1430109 for 1 and 1430110 for 2.
Results and Discussion
Compounds 1 and 2 were synthesized by modified literature
procedures [4, 11] as shown in Scheme 1. While previously
isolated as oils, they were obtained in pure crystalline form,
which enabled characterization by single crystal X-ray dif-
fraction (vide infra). The FT-IR spectra of 1 and 2 show
bands in the ranges 3100–2800 cm−1 and 2000–1630 cm−1
that correspond to aliphatic and aromatic C–H vibrations,
as well as combination modes, respectively (Fig. 1). The
vibrational bands in the range 1500–1400 cm−1 and those
at 1592 cm−1 correspond to aromatic C–C and C=C vibra-
tions, respectively. In general, the FT-IR spectra of 1 and 2
Fig. 4 UV–Vis absorption spectra of 1 (black) and 2 (red) in acetoni-
trile
Fig. 5 Normalized excitation (black) and emission (red) spectra of a 1 and b 2 in acetonitrile
Fig. 6 Low temperature (77 K) phosphorescence excitation and emission spectra of a 1 and b 2 in acetonitrile
1 3

J Chem Crystallogr
Table 1 Crystallographic data and structure refinement of 1 and 2
resonance at 3.33 ppm in 1 to 2.47 ppm in 2, which is
explained by the additional shielding of these protons by the
two sulfur atoms. The resonance from the thiol (S-H) proton
of 2 appears as a triplet at 1.43 ppm (Fig. 3). Similarly, the
13C NMR spectra of 1 and 2 showed no significant differ-
ences in the aromatic region (Figs. S1, S2).
Compound
1
2
Formula
C22H21BrS
397.35
Monoclinic
P21/c
C21H20S2
336.49
Monoclinic
P21/c
M/g mol−1
Crystal system
Space group
Both 1 and 2 display absorption maxima attributed to
π–π* transitions at 257 nm and excitation maxima at 271 and
272 nm, respectively (Figs. 4, 5a, b) [16]. The molar extinc-
tion coefficient, ε, of 2 at 257 nm (2700 M−1cm−1) is larger
than that of 1 at 257 nm (2100 M−1cm−1), as supported by
the relatively intense absorption spectrum of 2 compared to
that of 1 (Fig. 4).
a/Å
b/Å
c/Å
α/deg
7.4072 (9)
9.6924 (11)
25.652 (3)
90
15.3532 (8)
14.1552 (7)
7.8249 (4)
90
β/deg
90.023 (2)
90
1841.7 (4)
100
94.5239 (8)
90
1695.27 (15)
100
γ/deg
V/Å3
Each compound displays emission bands with maxima
that are mirror images of the excitation/absorption spec-
tra and thus due to π*→π transitions at 314 nm for 1 and
313 nm for 2 (Fig. 5a, b). 77 K time-resolved emission spec-
tra show phosphorescence in the range 400–600 nm with
resolved vibrational fine-structure (Fig. 6). The measured
energy gap, Δν, between the peaks of each phosphorescence
spectrum was determined to be 1587.5 8.5 cm−1, and is
attributed to the aromatic C=C vibrations in the compounds.
These vibrations were also observed in the FT-IR spectra of
1 and 2 at 1592 cm−1 (Fig. 1).
T/K
Z
4
4
Dc/g cm−3
1.433
2.345
1.318
0.311
µ(Mo–Kα)/mm−1
Independent reflections,
5097
5868
R
int [Fo≥σ(Fo)]
0.0567
0.0392
Reflections collected
5174
1.096
6114
1.020
GoF on F2
R1, wR2 [I>2r(I)]
0.0412 (4080)
0.0324 (5121),
0.1335 (5097)
0.0921
(5868)
Both compounds crystallize in the monoclinic P21/c
space group with four molecules in the unit cell. Details
of the crystallographic data and refinement for 1 and 2 are
given in Table 1. The asymmetric units of 1 and 2 are shown
in Fig. 7. They display simple structures, with the expected
propeller shape of the trityl functional group for 1 and chain-
like structure of the alkyl groups. The trityl-C–S distances
are 1.862 and 1.871 Å and the C–Br and C–SH distances are
1.962 Å and 1.817 Å in 1 and 2, respectively. The latter two
are in good agreement with literature values of 1.966 Å for
C–Br and 1.808 Å for C–SH, respectively [17]. The packing
Largest diff. peak and hole/e
1.07, −1.18
0.54, −0.27
are indistinguishable, as the C–Br band of 1 appears in the
fingerprint region. In contrast, a band at ~2550 cm−1, which
corresponds to the S-H stretch is absent in the spectrum of 1,
but present in the spectrum of 2. This assignment is consist-
ent with literature values [6, 15].
1
The H NMR spectra of 1 and 2 show very similar
aromatic peaks in the 7.40–7.20 ppm region (Figs. 2, 3).
However, there is a significant upfield shift of the proton
Fig. 7 Thermal ellipsoid plots of the asymmetric units of a 1 and b 2, with thermal ellipsoids at 50% probability. Hydrogen atoms are omitted
for clarity
1 3

J Chem Crystallogr
structure of both compounds displays an alternating arrange-
ment of neighboring molecules in a zig-zag pattern (Fig. 8a,
b). The packing of 1 is supported by intermolecular C–H⋯π
interactions (Fig. 9a), [18–20] with C–H⋯π distances of
2.684–3.387 Å. 1 also shows a weak intramolecular hydro-
gen bond between a phenyl ring of the trityl functional group
and the bromine atom, with a C–H⋯Br distance of 3.066 Å,
[20] as shown in Fig. 9b. Despite the presence of the phe-
nyl rings, only extremely weak π–π stacking is observed, as
the planes spanned by phenyl rings on adjacent molecules
intersect at an angle of ~10°, while the centroid-to-centroid
distance is long at 6.152 Å. The packing of 2, on the other
hand, is supported by weak π–π stacking interactions of two
neighboring molecules, as shown in Fig. 10. The distance
between the parallel planes spanned by the phenyl rings is
3.3 Å and the centroid-to-centroid distance is 5.2 Å [21].
Fig. 8 Packing structures of a 1 along the a axis and b 2 along the c axis, with thermal ellipsoids at 50% probability. Hydrogen atoms are omit-
ted for clarity
Fig. 9 Ball-and-stick plot of 1 showing the a intermolecular C–H⋯π and b intramolecular C–H⋯Br interactions and relevant distances in Å
1 3

J Chem Crystallogr
Fig. 10 Ball-and-stick plot of 2 showing a the π–π interaction with an interplanar distance of 3.3 Å and a centroid-to-centroid distance of
5.244 Å and b the S-H⋯π interaction with distance 2.715 Å
5. Muhammad F, Qi W, Wang A, Gu J, Du J, Zhu G (2015) J Mater
Conclusion
Chem B 3:1597–1604
6. Yu Y, Rowland CE, Schaller RD, Korgel BA (2015) Langmuir
Two tritylthio-containing compounds were synthesized. 2
was synthesized for the first time without the use of thi-
iranes. Both compounds were characterized by FT-IR, NMR,
UV–Vis absorption and fluorescence spectroscopy. Since
they were, for the first time, obtained as solids, characteriza-
tion by single-crystal X-ray diffraction was possible. They
both belong to the monoclinic space group P21/c with sim-
ple packing structures supported by weak π–π and hydro-
gen bond interactions. Both compounds absorb and emit in
the UV, due to π–π* transitions, with vibrationally resolved
phosphorescence spectra.
31:6886–6893
7. Wang M, Niu W, Wu X, Li L, Yang J, Shuang S, Dong C (2014)
RSC Adv 4:25183–25188
8. Tigaa RA, Lucas GJ, de Bettencourt-Dias A (2017) Inorg Chem
56:3260–3268
9. Jeong S, Achermann M, Nanda J, Ivanov S, Klimov VI, Hol-
lingsworth JA (2005) J Am Chem Soc 127:10126–10127
10. Hermes JP, Sander F, Peterle T, Urbani R, Pfohl T, Thompson
D, Mayor M (2011) Chem Eur J 17:13473–13481
11. Raghunand N, Guntle GP, Gokhale V, Nichol GS, Mash EA,
Jagadish B (2010) J Med Chem 53:6747–6757
12. Chan WR, Taylor DR, Willis CR, Bodden RL, Fehlhaber HW
(1971) Tetrahedron 27:5081–5091
13. SADABS: v.2.01 (2001) An empirical absorption correction pro-
gram. Bruker AXS Inc, Madison, WI
Acknowledgements We thank the National Science Foundation
14. SHELXTL: v.6.10 (2001) Structure Determination Software Suite.
Sheldrick GM, Bruker AXS Inc, Madison, WI
NSF-CHE 1363325 for funding this work.
15. Ghatak A, Debnath GH, Mandal M, Mukherjee P (2015) RSC Adv
5:32920–32932
16. Pavia DL, Lampman GM, Kriz GS, Vyvyan JA (2008) Introduc-
tion to spectroscopy. Cengage Learning, Boston
References
17. Allen FH, Kennard O, Watson DG, Brammer L, Orpen AG, Taylor
R (1987) J Chem Soc Perkin Trans 2:S1–S19
1. Thomas KG, Kamat PV (2003) Acc Chem Res 36:888–898
2. Hines DA, Kamat PV (2014) ACS Appl Mater Interfaces
6:3041–3057
18. Dance I (2003) CrystEngComm 5:208–221
19. Dance I, Scudder M (2009) CrystEngComm 11:2233–2247
20. Desiraju GR, Steiner T (2001) The weak hydrogen bond: in struc-
tural chemistry and biology. Oxford University Press, Oxford
21. Hunter CA, Sanders JKM (1990) J Am Chem Soc 112:5525–5534
3. Turo MJ, Macdonald JE (2014) ACS Nano 8:10205–10213
4. Hocaoglu I, Cizmeciyan MN, Erdem R, Ozen C, Kurt A, Sen-
naroglu A, Acar HY (2012) J Mater Chem 22:14674–14681
1 3