Molecular asterisks with a persulfurated benzene core are among the strongest organic phosphorescent emitters in the solid state

Article abstract of DOI:10.1016/j.dyepig.2014.04.036

A series of functionalized persulfurated benzene molecules were synthesized. Their photophysical properties and crystal structures were analyzed. All compounds are non-emitting in solution at room temperature, but in a sharp contrast, quantum yields can be very high (up to 100%) in the solid state at 298 K or in a rigid matrix at low temperatures. This is a consequence of a decrease of intramolecular rotations and motions, but conformational and rotamer issues along with substituent effects might also play a role. These compounds are among the rare examples of highly phosphorescent organic materials, due to a Crystallization Induced Phosphorescence or to an Aggregation Induced Phosphorescence. Compound 1 is among the most phosphorescent solid known to date. They thus represent an alternative to heavy metal ion-based triplet emitters in solid state.

Full text of DOI:10.1016/j.dyepig.2014.04.036

Accepted Manuscript
Molecular asterisks with a persulfurated benzene core are among the strongest
organic phosphorescent emitters in the solid state
Andrea Fermi, Giacomo Bergamini, Romain Peresutti, Enrico Marchi, Myriam Roy,
Paola Ceroni, Marc Gingras
PII:
S0143-7208(14)00172-7
10.1016/j.dyepig.2014.04.036
DYPI 4364
DOI:
Reference:
To appear in: Dyes and Pigments
Received Date: 11 March 2014
Revised Date: 20 April 2014
Accepted Date: 25 April 2014
Please cite this article as: Fermi A, Bergamini G, Peresutti R, Marchi E, Roy M, Ceroni P, Gingras M,
Molecular asterisks with a persulfurated benzene core are among the strongest organic phosphorescent
emitters in the solid state, Dyes and Pigments (2014), doi: 10.1016/j.dyepig.2014.04.036.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to
our customers we are providing this early version of the manuscript. The manuscript will undergo
copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please
note that during the production process errors may be discovered which could affect the content, and all
legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT
Molecular asterisks with a persulfurated benzene core are among the strongest
organic phosphorescent emitters in the solid state
a,b
a
b,c
a
b
Andrea Fermi, Giacomo Bergamini, Romain Peresutti, Enrico Marchi, Myriam Roy, Paola
a
b
Ceroni, * and Marc Gingras *
a
Department of Chemistry “G. Ciamician” and Interuniversity Center for the Chemical Conversion of Solar
Energy (SolarChem), University of Bologna, Via Selmi 2, I-40126 Bologna, Italy.
E-mail: paola.ceroni@unibo.it; Tel: (+39)0512099535
b
CNRS, Aix-Marseille Université, CINAM UMR 7325, 163 avenue de Luminy, 13288 Marseille, France, E-
mail : marc.gingras@univ-amu.fr, Tel: (+33)(0)491829155
c
Present address: Institut Charles Gerhardt de Montpellier, UMR CNRS 5253, ENSCM-AM2N, 8, rue de
l’Ecole Normale, 34296 Montpellier Cedex 05, France.
Abstract
A series of functionalized persulfurated benzene molecules were synthesized. Their photophysical
properties and crystal structures were analyzed. All compounds are non-emitting in solution at room
temperature, but in a sharp contrast, quantum yields can be very high (up to 100%) in the solid state
at 298 K or in a rigid matrix at low temperatures. This is a consequence of a decrease of
intramolecular rotations and motions, but conformational and rotamer issues along with substituent
effects might also play a role. These compounds are among the rare examples of highly
phosphorescent organic materials, due to a Crystallization Induced Phosphorescence Emission
(CIPE) or to an Aggregation Induced Phosphorescence Emission (AIPE). They thus represent an
alternative to heavy metal ion-based triplet emitters in solid state.
1

ACCEPTED MANUSCRIPT
1
Introduction
In recent years, organic luminescent solids have become a cornerstone in materials science,
while covering several fields of application, such as stimuli responsive switches [ 1 , 2 ],
optoelectronic devices [3,4] and chemosensors [5,6]. Because of their availability and lower
toxicity, they represent an important alternative to heavy metal ion-based triplet emitters in the solid
state and to quantum dots incorporating toxic elements.
Luminescent organic materials and some supramolecular assemblies have been developed
and those architectures can exhibit very attractive physical, photochemical and chemical properties
[7,8]. However, it is well known that many organic luminophores have their emission highly or
totally quenched in the condensed phase, where aromatic molecules could self-aggregate by making
π-π interactions, thus self-perturbing their own π-systems [9,10]. This phenomenon is referred to as
Aggregation-Caused Quenching (ACQ). To the contrary, Aggregation Induced Emission (AIE)
results from a decrease of intramolecular rotations and motions, which engenders a luminescence
enhancement [11, 12, 13]. More recently, some attention was paid to AIPE (Aggregation Induced
Phosphorescence Emission), when a luminogen displays phosphorescence enhancement as a result
1
5
of aggregation [14, ]. This effect is most frequently observed for metal complexes involving
II
III
I
heavy atoms (e.g., Pt , Ir , Re ) whose presence can promote intersystem crossing and spin-
forbidden radiative transitions. On the other hand, the AIPE effect of organic molecules has been
rarely reported so far, and only scarce examples of organic phosphorescent solids displaying a high
quantum yield are known [16].
Along those lines, persulfurated benzene molecules are intriguing pigments, easily obtained
from cheap and commercial starting materials since their first synthesis in 1957 [17, 18]. However,
it is surprising that the photophysical properties of this family of compounds had remained
relatively unexplored [19, 20]. Only recently, hexakis(4-methyl-1-phenylthio)benzene (1, Figure 1)
2

ACCEPTED MANUSCRIPT
had been shown to exhibit enhanced photophysical properties with a very intense green
phosphorescence (Φ=1.0) when the molecule experiences a rigid environment (i.e. in a frozen
solution at low temperatures or in the solid phase) [21]. It is among the most phosphorescent
organic molecules known in the solid state.
Due to this exceptional feature, and in order to further study this family of compounds, five
other luminogens (2-6, Figure 1) were recently synthesized by varying their steric and electronic
characteristics. Sterically hindered derivatives 5 and 6 are unknown in the literature, and the
photophysical behaviors of 2-6 have never been reported. We wanted to screen compounds 1-6 to
empirically correlate their photophysical properties to some substituent effects, in the hope for
predicting and further modulating their properties. More importantly, we also devise these
experiments to voluntarily modify the conformational behavior of those molecules, which has
already been shown to be important in other family of luminogens involving AIE [14]. We first
focused on a hexathiobenzene core connected to six phenyl arms possessing variable steric
congestion at the ortho and meta positions, for modifying the molecular rotations and
conformations, in the hope for other strong AIE effects. A set of three compounds (4-6) in an
asterisk-like geometry comprises hindered groups at the ortho positions of the outer benzene rings.
As a second parameter, the electronic contribution was varied by appending groups with different
electron donating ability. The synthesis of all compounds is described, together with an analysis of
their molecular structure and crystal lattices (as determined by X-ray diffraction), their aggregation
state and properties, and their photophysical behavior as a function of temperature.
This work will thus open wider perspectives toward the uses of a new family of
phosphorescent molecules, while providing further insights into their photophysical and aggregation
properties, along with their interactions and conformations in the crystalline state.
2
Experimental section
3

ACCEPTED MANUSCRIPT
2.1 Materials, general methods and analytical equipment
All reagents and compounds were bought from Sigma-Aldrich, Alfa Aesar and TCI and
used without further purification, unless specifically mentioned. Solvents were purchased from
Sigma-Aldrich, Acros Organics or Carlo Erba (analytical or reagent grade) with a low water content
1
13
and stored over freshly activated 3Å molecular sieves (activated for 3 hours at 250°C). H and C
NMR were recorded on a Bruker Avance 250 spectrometer equipped with an automatic sampler.
1
13
Chemical shifts are provided in ppm relative to TMS (δ=0 ppm) for H (250 MHz) and C NMR
1
(
62.90 MHz). Otherwise, some internal standards came from the solvents used: CDCl ( H NMR:
3
1
3
1
13
δ=7.26 ppm; C NMR: 77.36 ppm) or DMSO-d ( H NMR: δ=2.50 ppm; C NMR: δ=39.5 ppm),
6
1
according to the literature data [22]. The resonance multiplicities in the H NMR spectra are
described as “s” (singlet), “d”(doublet), “t” (triplet), “q” (quartet), sept (septuplet), “m” (multiplet)
or “b” (broad). HRMS spectra using electrospray ionization (ESI) were recorded at the Spectropole
of Marseille (France) in triplicate with double internal standards on a QStar Elite (Applied
Biosystems SCIEX) instrument equipped with an atmospheric ionization source (API) and a TOF
analyzer in a positive mode. LRMS analyses were performed on a Shimadzu GC-MS QP2010SE
instrument equipped with a DI2010 direct introduction unit with an electronic impact ionization
source at 70eV. Infrared absorption spectra were recorded on solids with a Perkin-Elmer Spectrum
100 FT-IR spectrometer equipped with a universal ATR accessory (contact crystal: diamond). Thin-
®
Layer chromatography (TLC) was performed on precoated silica gel (Alugram SilG/UV gel)
2
54
aluminium plates from Macherey-Nagel. Flash chromatography was performed over silica gel 60,
Merck type 230-400 mesh (40-63 ꢀm). Melting points (uncorrected) were recorded on a IA9200
apparatus purchased from Thermo Fischer Scientific (Electrothermal) after a calibration with
standards. X-ray diffraction data were recorded at 203 K on a Bruker Nonius Kappa CCD
diffractometer using MoKα radiation (λ=0.71073 Å). Data collection was performed with
COLLECT (Nonius, 2001), cell refinement and data reduction with DENZO/SCALEPACK
4

ACCEPTED MANUSCRIPT
(Otwinowski & Minor, 1997). The determination of the hydrodynamic diameter distributions of the
nanocrystals was carried out from DLS measurements with a Malvern Nano ZS instrument with a
633 nm laser diode.
2.2 Photophysical measurements
Absorption spectra in the 190-1100 nm range were recorded at room temperature in
solutions contained in quartz cuvettes (optical pathlength 1 cm and 5 cm, Hellma®) by using a
Perkin Elmer λ40 spectrophotometer. Fluorescence and phosphorescence emission and excitation
spectra in the 250-900 nm range were recorded with a Perkin Elmer LS 50 spectrofluorimeter
equipped with Hamamatsu R928 photomultiplier. Room temperature spectra were recorded in
spectrofluorometric suprasil quartz cuvettes with 1 cm optical path. Lifetimes from 0.5 ns to 10 ꢀs
were measured by an Edinburgh FLS920 spectrofluorimeter equipped with a TCC900 card for data
acquisition in time-correlated single-photon counting experiments (0.5 ns time resolution) with a
pulsed diode laser. Lifetimes in the range between 10 ꢀs and 5 s were measured with the same
Perkin Elmer LS 50 spectrofluorimeter upon excitation with a pulsed Xe lamp (repetition
frequency: 5-50 Hz). Emission spectra in frozen matrix at 77 K were recorded using quartz (or
glass) tubes with an internal diameter of about 2 mm and a 20 cm length immersed in liquid
nitrogen. A transparent dewar (glass or quartz) with a cylindrical terminal part with a 1 cm external
diameter was employed. The device fits into the sample holder of the spectrofluorimeters
mentioned above. Measurements of emission spectra and lifetimes as a function of temperature
were performed by inserting a quartz cell into a cryostat equipped with a temperature controller
(model TC1) by Oxford Instruments. For solid samples, emission quantum yields were measured by
corrected emission spectra obtained from an apparatus consisting of a barium sulfate coated
integrating sphere (LabSphere, 4 inches diameter), a 450 W Xe lamp (λex tunable by a
monochromator supplied with the instrument) as light source, and a R928 photomultiplayer tube,
5

ACCEPTED MANUSCRIPT
following the procedure described by De Mello et al. [23]. The experimental errors are within: ±2
nm of the band maximum, 5% of the molar absorption coefficient, 10% of the lifetime
measurements, and 30% of the emission quantum yield in solid.
2.3 Synthesis and characterization
2.3.1 Hexakis(4-methyl-1-phenylthio)benzene (1) [24, 25]
This protocol is based on a previous work [23]. Hexachlorobenzene (4.506 g., 15.82 mmol,
.00 eq.), dry K CO (19.66 g., 142.2 mmol; 8.99 eq.) and p-thiocresol (18.061 g., 145.4 mmol;
1
9
2
3
.19 eq.) were added into a round bottom flask capped with a septum under an argon atmosphere.
Dry DMF (100 mL) was injected via a syringe and the mixture was stirred at 60°C for 40 hours. It
turned yellow and the completion of the reaction was monitored by TLC (SiO , n-hexane/EtOAc
2
8
5:15 v/v; R = 0.74). An aqueous solution of NaOH (2M, 100 mL) was poured into the flask while
f
stirring, and a yellow precipitate appeared. After collecting the solid by filtration, the crude product
was triturated with a solution of ethanol/H O (85:15 v/v; 50 mL) while stirring at reflux for 3 hours.
2
After cooling at RT, a filtration left a yellow solid, which was rinsed with ethanol (10 mL), with
diethyl ether (20 mL), and then dried under high vacuum (11.55 g, 14.24 mmol, 90%). For an
analytical purity, it was recrystallized from warm toluene to afford bright yellow crystals. The
characterization of 1 is in good agreement to the literature data [23, 26, 27]. M.p.: 201.9-202.3°C.
FT-IR (ATR diamond contact; solid sample): 3069 (CH arom), 3014 (CH arom), 2942 (CH ), 2862
3
-1 1
(
CH ), 1487, 1445, 1276, 1174, 1015 (CH arom), 805 (strong, CH arom) cm . H NMR (250.13
3
1
3
MHz, CDCl ) δ (ppm): 2.27 (s, 18H), 6.93 (d, J=8.1 Hz, 12H), 6.82 (d, J=8.2 Hz, 12H). C NMR
3
+
(
62.90 MHz, CDCl ) δ (ppm) 139.6, 136.5, 132.7, 131.6, 129.1, 21.3. MS (ESI , m/z): 811.0
3
+
+
[
M+H] , 833.0[M+Na] . Anal. Calcd for (C H S ): C, 71.07%, H, 5.22%, S, 23.72%; and Found:
48 42 6
C, 71.48%, H, 5.39%, S, 23.10%.
6

ACCEPTED MANUSCRIPT
2.3.2 Hexakis(phenylthio)benzene (2) [24], [26]
Hexachlorobenzene (5.075 g, 17.82 mmol, 1.00 eq.), dried K CO (21.906g, 158.50 mmol,
2
3
8.89 eq.) and thiophenol (19.00 mL, 185.89 mmol, 10.43 eq.) were added into an oven-dried round
bottom flask capped with a septum under an argon atmosphere. Dry DMF (100 mL) was injected
via a syringe and the mixture was stirred at 60°C for 46 hrs. The reaction was monitored by TLC
(
SiO , n-hexane/EtOAc: 85/15 v/v; R product= 0.5) and turned orange. After cooling at RT, an
2
f
aqueous solution of NaOH (2M, 100 mL) was poored into the flask while stirring, and a bright
yellow precipitate appeared. After collecting the solid by filtration, the crude product was triturated
in refluxing water-ethanol (15/85 v/v; 50 mL) for 3 hrs, cooled and filtered again, washed with
ethanol (10 mL) and diethyl ether (20 mL). It was dried under high vacuum and finally
recrystallized from warm toluene. After filtration, 2 was obtained as bright yellow needles
(
11.402g, 15.68 mmol, 88%). M.p.: 186.0-186.7°C. R = 0.68 (SiO , n-hexane-CH Cl : 50:50 v/v).
f 2 2 2
FT-IR (ATR diamond contact; solid sample): 3064 (CH), 3016 (CH), 2988 (CH), 1576 (C=C), 1474
-1 1
(
C=C), 1437 (C=C), 1265, 1073 (CH), 1022 (CH), 735 (strong, CH), 685 (CH) cm . H NMR
1
3
(
250.13 MHz, CDCl ) δ (ppm): 6.92-6.96 (m, 2H), 7.09-7.19 (m, 3H). C NMR (62.90 MHz,
3
+
+
+
CDCl ) δ (ppm): 136.5, 135.7, 131.2, 129.3, 127.3. MS (ESI , m/z): 726.9 [M+H] , 749.9 [M+Na] .
3
Anal. Calcd for C H S : C, 69.38%, H, 4.16%, S, 26.46%; and Found: C, 69.50%, H, 4.25%, S,
4
2
30 6
25.76%.
2.3.3 Hexakis(3-methoxy-1-phenylthio)benzene (3) [27]
Hexachlorobenzene (678.0 mg, 2.38 mmol, 1.00 eq.), dried K CO (2.95g, 21.4 mmol, 8.99
2
3
eq.) and 3-methoxy-1-thiophenol (2.70 mL, 22.0 mmol, 9.24 eq.) were added into a dry round
bottom flask capped with a septum under an argon atmosphere. Dry DMF (15mL) was injected via
7

ACCEPTED MANUSCRIPT
a syringe and the mixture was stirred at 80°C for 40 hrs. It turned from white to orange and the
completion was monitored by TLC (SiO , n-hexane/EtOAc : 60:40 v/v; R = 0.5). After cooling
2
f
and adding an aqueous NaOH solution (2M, 75mL), a bright yellow solid formed and it was
collected by filtration. It was then triturated in a ethanol/water solution (15:85 v/v; 15mL) for 4h,
filtered again, washed with ethanol and finally recrystallized from warm toluene. Hexakis(3-
methoxy-1-phenylthio)benzene 3 was obtained as some green-yellow crystals (1.675g, 1.85 mmol,
7
8%). M.p. 158–159°C (lit.141-144°C [29]). R = 0.17 (SiO , n-hexane-CH Cl : 50:50 v/v). FT-IR
f 2 2 2
(
ATR diamond contact; solid sample): 3069 (CH arom), 3004 (CH arom), 2936 (CH ), 2831 (CH ),
3 3
1
7
1
587 (C=C), 1573 (C=C), 1474 (C=C), 1418, 1279, 1223, 1035 (strong CH arom), 840 (CH arom),
-1
1
67 (strong, CH arom) cm . H NMR (250.13 MHz, CDCl ) δ (ppm) 3.69 (s, 18H), 6.56-6.48 (m,
3
1
3
2H), 6.63 (ddd, J = 8.3, 2.19, 1.02 Hz, 6H), 7.05 (t, J = 8.3 Hz, 6H). C NMR (62.90 MHz,
+
CDCl ) δ (ppm) 55.08, 111.90, 113.23, 120.09, 129.68, 139.00, 148.34, 159, 83. MS (ESI , m/z):
3
+
+
+
+
9
6
2
07.0 [M+H] , 924.0 [M+NH ] , 928.9 [M+Na] , 944.9 [M+K] . Anal. Calcd for C H O S : C,
4 48 42 6 6
3.55%, H, 4.67%, O, 10.58%, S, 21.21%; and Found: C, 63.54%, H, 4.74%, O, 10.40%, S,
1.14%.
2.3.4 Hexakis(2-methyl-1-phenylthio)benzene (4) [27]
Under an argon atmosphere, an oven-dried two necked flask fitted with a septum and a
lateral addition tube containing powder sodium hydride 95% (237 mg, 9.87 mmol, 10.5 eq) was
charged with hexachlorobenzene (267.7 mg; 0.94 mmol, 1.00 eq.) and 1,3-dimethyl-2-
imidazolidinone (6.0 ml) as a solvent. After adding o-thiocresol (1.054 g, 8.49 mmol, 9.00 eq.) via a
syringe while stirring, powder NaH 95% was gradually added by means of the lateral tube to the
cooled reaction at 5-8°C (ice-bath), while controlling the release of hydrogen gas. After most
evolution of the gas, the mixture was heated at 60°C for 96 hrs, generating a bright yellow color. A
yellow solid precipitated after adding an aqueous NaOH solution (2M, 60 ml). The solid was
8

ACCEPTED MANUSCRIPT
isolated by filtration and triturated by stirring with a mixture of ethanol/H O (4:1 v/v; 15 ml). The
2
product was then purified by column chromatography (eluent; petroleum ether-toluene: 70:30 v/v)
to afford sufficiently pure 4 (483.6 mg, 0.60 mmol, 63%). For analytical and X-ray structure
determination, the solid was recrystallized from boiling toluene to afford yellow crystals on cooling.
M.p.: 193-195°C (lit. 186-190°C [26]). R = 0.75 (SiO , n-hexane-CH Cl : 50:50 v/v). FT-IR (ATR
f
2
2
2
diamond contact; solid sample): 3058 (CH arom.), 2916 (CH ), 1588 (C=C), 1466 (C=C), 1454
3
-1 1
(
C=C), 1264, 1057 (CH arom), 1044 (CH arom), 739 (CH arom) cm . H NMR (250.13 MHz,
1
3
CDCl ) δ (ppm) 2.06 (s, 18H), 6.50 (dd, J=7.2 Hz, 1.5 Hz, 6H), 6.73-6.93 (m, 18H). C NMR
3
(
62.90 MHz, CDCl ): δ=20.5 (CH ), 126.4, 126.6, 128.5, 130.6, 136.8, 137.5, 148.6. HRMS (ESI,
3 3
CH OH, NH Ac 3 mM, + ion mode) calcd for C H S : m/z = 810.1611 Da, found m/z = 811.1679
3
4
48 42 6
+
[
M+H] . Anal. Calcd for C H S : C, 71.07%; H, 5.22%, S, 23.72%; and Found: C, 69.75%, H,
48 42 6
5.18%, S, 23.28%.
2.3.5 Hexakis(2-isopropyl-1-phenylthio)benzene (5)
A round bottom flask was charged with hexachlorobenzene (18.7 mg; 0.066 mmol, 1.00 eq)
and cesium carbonate (218.1 mg, 0.669 mmol, 10.1 eq). The flask content was dried under vacuum
to remove the last traces of water. Under anhydrous and argon conditions, dry 1,3-dimethyl-2-
imidazolidinone (0.60 ml) was injected via a syringe, followed by 2-isopropyl-1-thiophenol 90%
pure (90.5 mg; 0.100 ml, 0.594 mmol, 9.00 eq). The mixture was stirred at 100°C for 96 hrs. After
being cooled to RT, the mixture was poured into an aqueous NaOH solution (2M, 6.0 ml), extracted
with toluene (4x5ml) and washed with H 0 (2x10mL). The combined organic phases were dried
2
over anhydrous MgSO . After filtration and evaporation of the solvent, a solid was obtained. It was
4
then triturated for 30 min. in a solution of ethanol/H O (90:10 v/v; 5 ml) and collected by filtration.
2
A column chromatography (eluent; petroleum ether-toluene: 80:20 v/v) afforded 5 (52.6 mg, 0.053
mmol, 81%) as a yellow solid. For an analytical and X-ray structure determination, the product was
9

ACCEPTED MANUSCRIPT
recrystallized from boiling toluene. M.p.: 215-217°C. R = 0.41 (SiO , petroleum ether-CH Cl :
f
2
2
2
8
2
7
3
7
0:20 v/v). FT-IR (ATR diamond contact; solid sample): 3052 (CH arom), 2957 (CH, CH aliph.),
3
866 (CH, CH aliph.), 1588 (C=C), 1471 (C=C), 1434, 1276, 1047 (CH arom), 1031 (CH arom),
3
-1 1
44 (strong, CH arom) cm . H NMR (250.13 MHz, CDCl ) δ (ppm): 1.09 (d, J= 3.3 Hz, 36H),
3
.35 (sept, J=3.3 Hz, 6H), 6.56 (dd, J=7.9, 1.0 Hz, 6H), 6.93 (td, J=7.5, 1.6 Hz, 6H), 7.09 (td, J =
1
3
.6, 1.1 Hz, 6H), 7.17 (dd, J=7.8, 1.0 Hz, 6H). C NMR (62.90 MHz, CDCl ): δ= 23.6 (CH ), 30.7
3
3
(
CH(CH ) ), 125.7, 126.4, 126.7, 129.1, 137.5, 147.1, 150.4. HRMS (ESI, CH OH, NH Ac 3 mM,
3
2
3
4
+
+
ion mode) Calcd for C H S : m/z = 978.3489 Da, Found m/z = 979.3562 [M+H] . Anal. Calcd
60 66 6
for C H S : C, 73.57%, H, 6.79%, S, 19.64%; and Found: C, 73.74%, H, 6.94%, S, 19.81%.
6
0
66 6
2.3.6 Hexakis(2-methoxy-1-phenylthio)benzene (6)
Under an argon atmosphere, an oven-dried two necked flask fitted with a septum was
charged with hexachlorobenzene (127.8 mg; 0.449 mmol, 1.00 eq) and 1,3-dimethyl-2-
imidazolidinone (3.0 ml). After adding 2-methoxythiophenol (570 mg, 4.07 mmol, 500 µl, 9.06 eq)
via a syringe, NaH (60% in oil dispersion, washed dry with n-hexane, 138 mg, 5.75 mmol, 12.8 eq)
was gradually added by means of a lateral addition tube to the cooled reaction at 5-8°C (ice-bath).
A vigorous release of hydrogen gas was noticed. After most evolution of gas, the mixture was
heated at 80°C for 50 hrs. A bright yellow color appeared. The reaction mixture was then poured
into an aqueous NaOH solution (2 M, 10 ml) while stirring. A yellow-green solid precipitated. It
was isolated by filtration and washed several times with H O (100 mL). It was then triturated by a
2
vigorous stirring in an ethanol/H O solution (50:50 v/v; 15 mL). After another trituration in warm
2
toluene for removing traces of oil and organic impurities, filtration and drying, a bright yellow solid
was obtained (265.8 mg, 0.293 mmol, 65%). M.p: 248-249°C. FT-IR (ATR diamond contact; solid
sample): 3061 (CH arom), 3003 (CH arom), 2967 (CH ), 2934 (CH ), 2834 (CH ), 1576 (C=C),
3
3
3
1475 (C=C), 1458 (C=C), 1447 (C=C), 1431, 1274 (C-O), 1241,1065 (CH arom), 1022 (CH arom),
1
0

ACCEPTED MANUSCRIPT
-1 1
7
40 (CH arom) cm . H NMR (250.13 MHz, DMSO-d ): δ= 3.72 (s, 18H), 6.55 (d, J=6.6 Hz, 6H),
6
13
6
.82 (t, J=6.8 Hz, 6H), 6.92 (d, J=7.6 Hz, 6H), 7.10 (t, J=7.1 Hz, 6H). C NMR (62.90 MHz,
CDCl CDCl ): δ= 159.9, 148.4, 139.1, 129.7, 120.2, 113.3, 112.0, 55.1. HRMS (ESI, CH OH,
2
2
3
NH Ac 3 mM, + ion mode) Calcd for C H O S : m/z = 906.1306 Da, Found: m/z = 907.1377
4
48 48
6 6
+
[
M+H] .
3. Results and discussion
3.1 Synthesis
The target compounds were synthesized by exploiting multiple aromatic substitutions involving
functionalized thiophenolate salts and hexachlorobenzene (C Cl ) in a highly polar solvent such as
6
6
1,3-dimethyl-2-imidazolidinone (Scheme 1). This method represents a convenient way to obtain
aromatic persulfurated molecules by using relatively cheap materials in a one-step reaction [28, 29].
In order to produce compounds 1-6, as indicated in Figure 1, a series of functionalized thiophenols
incorporating various alkyl or alkoxyl substituents were chosen. In the presence of a bulkier group
(especially at ortho positions), the activation energy is expected to increase, so that the nucleophilic
attack becomes more difficult. The general synthetic procedure used an excess of thiol (ca. 9.0 eq
relative to C Cl ) and either sodium hydride or cesium carbonate as a base (9.0 eq. relative to C Cl )
6
6
6
6
to generate the thiolate anions. They then reacted with C Cl in a range of temperatures between 20-
6
6
100°C. Many reactions can proceed at 25°C but for ensuring a completion, longer reaction time and
higher temperatures were sometimes used. Compounds 1-6 were isolated in satisfactory yields (up
1
13
to 90%, unoptimized) and characterized by usual spectroscopic methods: H, C NMR, FT-IR and
mass spectrometry. The purity was ascertained by elemental analysis and sometimes by HPLC.
Most of them were purified by recrystallization up to an analytical grade, affording single crystals
for X-ray structure determination and analysis of the solid-state structure. Generally,
1
1

ACCEPTED MANUSCRIPT
hexakis(phenylthio)benzene derivatives show a good solubility in common organic solvents,
excepted for the ortho-methoxy derivative 6.
3.2 X-ray structure determination from monocrystals
Some crystallographic data are reported in Table 1. Molecule 1 crystallizes in a trigonal cell
(R-3 space group), while compounds 2-4 show a triclinic lattice (P-1). Structure 5 crystallized in a
monoclinic P 2/c cell. All molecules do not incorporate solvent molecules in their crystal lattice as
it is the case with some known clathrates [30]. Generally, most persulfurated benzene molecules
possessing divalent sulfur atoms surrounding the central benzene unit retain an alternating up and
down ababab conformation (a and b: above and below the plane of the central ring) in their
crystalline structure [20] (Figure 2).
On the contrary, compound 4 generates two crystallographically independent molecules (two
conformers: aababb and aaabbb) in the crystal lattice, in agreement with some published results
[
29]. Compound 5 exhibits two identical conformers (aabaab) rotated by 180° one with respect to
the other (Figure 3).
Additionally, for 1, 3, 4 and 5, which carry substituents on the external phenyl rings, we can
observe significant distorsions (non planarity, up to 10°) in the central benzene ring, especially for
molecule 3. This result suggests that distortion is caused by the arrangement and interactions of the
external units (arms). For instance, molecule 4 has a dissymmetric distortion in the central ring,
probably due to one edge-face interaction from a single peripheral phenyl rings from each of the
two conformers in the same crystal lattice. The peripheral rings do not show such a distorsion from
planarity.
1
2

ACCEPTED MANUSCRIPT
Table 1. Crystallographic data of molecules 1-5.
Compound
Empirical
Formula
Formula
weight
1
2
3
4
5
C H S
C H S
42 30
C H O S
48 42
C H S
48 42
C H S6
60 66
4
8
42
6
6
6
6
6
8
11.24
727.08
907.23
811.24
979.56
Crystal system
Space group
a [Ǻ]
trigonal
R-3
triclinic
P -1
triclinic
P -1
triclinic
P -1
monoclinic
P 2/c
21.203(2)
21.203(2)
8.0779(6)
90
9.6084(3)
10.2745(3)
10.6639(3)
68.537(2)
76.902(2)
65.519(2)
888.169
1
9.3151(2)
12.4942(2)
15.1208(4)
21.9167(4)
93.033(2)
98.286(2)
91.709(1)
4088.65
4
19.9876(3)
11.6249(2)
25.2014(3)
90
b [Ǻ]
11.9900(2)
12.0182(2)
116.685(1)
108.966(1)
92.710(1)
1104.15
1
c [Ǻ]
α [°]
β [°]
90
106.270(1)
90
γ [°]
120
3
Volume [Ǻ ]
3145.02
3
5321.14
4
Z
T [K]
203
203
203
203
203
R-factor [%]
0.053
0.0544
0.0529
0.0769
0.0664
The large interplanar distances (Å) between central persulfurated benzene rings in
compounds 1- 5 (Figure 4) suggests that no significant π-π-interaction takes place.
As for some substituent effects, we clearly observe that all ortho isopropyl groups lie outward
relative to the central phenyl plane in molecule 5 (Figure 3). Such structure could lead to peripheral
intermolecular Van der Walls interactions in the solid (lateral forces), while diminishing
intramolecular steric energy. This molecule presents rotamers around the C-S-C bonds different
1
3

ACCEPTED MANUSCRIPT
from those of all other structures 1-4. The bulkiness of the isopropyl groups seems responsible for
this observation.
3.3 Photophysical characterization
As expected, compounds 1-6 show similar absorption spectra in CH Cl at room
2
2
temperature (Figure 5): the lowest energy band indicates a maximum around 330 nm and a tail up to
50 nm. At higher energies (~295 nm) only 3 and 6 display a quite narrow absorption peak due to
4
the presence of the methoxy group at the meta and ortho positions on the outermost aromatic rings.
No significant emission is observed in air-equilibrated or oxygen-free solutions of compounds 1-6
in solution (Φem ≤ 0.001), while intense luminescence is observed for some compounds in the
powder state and at 77 K in a rigid matrix (CH Cl /CH OH: 1:1, v/v). In the solid state, the
2
2
3
emission bands display maxima between ca 490 and 525 nm (Figure 6), while in a rigid matrix,
spectra appear moderately blue-shifted with maxima between 490 and 510 nm (Figure S1 and Table
2). For powders and rigid matrices, emission lifetimes are in the ꢀs and ms timescale, respectively
(
Table 2), and they are consistent with a spin-forbidden radiative deactivation (T → S ).
1
0
The molecules under investigation display phosphorescence only when they experience a
sufficiently rigid environment (like in the solid state), slowing down radiationless deactivation of
excited states. This is a quite rare behavior, since most of the phosphorescent molecules with
emission lifetimes similar to those of 1-6 show emission both in deaerated solutions and rigid
environments [31]. This phenomenon has been recently ascribed to restriction of intramolecular
motions [21]: C-S-C bonds can actually rotate in solution, leading the external aromatic units the
generation of different rotamers with respect to the central benzene ring, thus allowing the molecule
to exchange vibrational and rotational energy with the solvent.
1
4

ACCEPTED MANUSCRIPT
3.3.1 Structural effects
A comparison among the persulfurated benzene molecules shows that there is a large difference
between the emission quantum yields in the solid state: starting from 6% for 5 up to 100% for 1.
For example, if we compare 1, 4 and 5, no significant emission band shift is observed (Figure 6a),
so that the substituents have a similar effect from the electronic point of view (1 and 4 are isomers),
but a substantial decrease of the emission quantum yield is observed in the same series (Table 2).
Before discussing possible correlations between crystal structure and emission properties in the
solid state, it is worth mentioning that we cannot exclude an effect due of the degree of crystallinity
on the emission quantum yield. Indeed, in the case of 4, the phosphorescence quantum yield drops
from 0.60 to 0.15 going from powder to a film formed by evaporation of a CHCl solution of 4 on a
3
quartz slide.
As pointed out before, the crystal structure shows that the central persulfurated benzene ring
in compounds 1, 3, 4 and 5 is not coplanar, but this does not indicate a correlation to the quantum
yields. By analyzing the different rotamers in the crystal structures, for compounds 1-4 we observed
a syn-periplanar alignment of one lone pair on a sulfur atom with the π-system of the persulfurated
benzene ring. Empirically and as a rule of thumb, those rotamers seem favorable to a
phosphorescence emission in this family of compounds 1-4. To the contrary, a steric hindrance
from large ortho substituents (iPr, OMe) seems to strongly modify rotamers and favorable lone
pairs (or empty sigma* orbitals) alignment with the central π-system. In short and most importantly
in the field of AIE, we emphasize here the importance of conformational effects, rotameric
orientation, on luminescence in this AIE process, and not only to a simple restriction of rotations or
molecular motions. However, the exact explanations remain unclear and further studies are needed
[32, 33].
1
5

ACCEPTED MANUSCRIPT
Table 2. Photophysical data of compound 1-6 under different experimental conditions.
Absorption
Emission
CH Cl -CH OH, 77
2
2
3
CH Cl , 298 K
Solid phase, 298 K
2
2
K
-
1
-1
Compound
λ / nm
326
323
325
316
328
322
ε / M cm
19200
19300
18500
20200
21600
19800
λmax / nm
505
τ / ms
4.0
λmax / nm
513
τ / ꢀs
3.0
Φ
1.0
0.6
0.3
0.5
a
1
2
3
4
5
6
502
3.6
515
12.1
6.8
500
4.1
522
509
6.2
522
15.8
5.3
512
8.9
526
0.06
0.07
505
4.0
487
6.8
a
The value reported in ref. 21 was lower due to the low crystallinity of the sample.
3.3.2 Temperature effect on phosphorescence
In order to better understand the emission properties of these materials, an analysis of luminescence
as a function of temperature has been carried out on compounds 4-6 in CH Cl :CH OH 1:1 (v/v)
2
2
3
solution. Starting at 298 K and decreasing the temperature, luminescence abruptly rises in intensity
at 115 K. This behavior seems to be independent from the type of substituent at the ortho positions
of the external phenyl units. It is observed an OFF-ON transition in a very narrow range of
temperatures for all three molecules (Figure 7a). In addition, the increase of emission intensities is
accompanied by a blue-shift in the emission band maxima (Figure 7b) suggesting a charge-transfer
character of the emissive excited states. Similar behavior is observed for 6 in butyronitrile (Figure
8a) where compound 6 is highly soluble: the temperature in which phosphorescence is switched on
is the same (Figure 8b), although the emission intensity changes are less abrupt that in
1
6

ACCEPTED MANUSCRIPT
CH Cl :CH OH matrix. This result confirms that isolated molecules dispersed in a rigid matrix are
2
2
3
responsible for the observed luminescence and no aggregate is formed at low temperature. Thus,
below 115 K, the glassy matrix works as a rigid cage in which molecules are blocked and non-
radiative deactivations are disfavored. Despite the presence of different bulky groups which can
affect the kinetic energy barrier involved in the intramolecular rotations, no significant differences
was evidenced by the emission profiles as a function of temperature.
3.4 Preparation of phosphorescent mesoscopic particles
In order to exploit the emission properties of 6 in fluid solution, the formation of mesoscopic
particles has been attempted by means of a reprecipitation method [34]. 800 ꢀl of a THF solution of
-5
6
(1.9 × 10 M) were introduced under sonication in 2 ml of H O: a colloid is readily obtained,
2
clearly showing opacity. The resulting suspension contains 71% H O, while the final concentration
2
-6
of 6 is 5.5× 10 M. Absorption spectrum (Figure 9a) displays a long tail due to the Mie scattering,
clearly indicating the presence of a particle dispersion, and similar band structure in the UV region
compared to 6 in THF solution. Moreover, emission spectrum shows an intense emission with a
maximum around 510 nm and a lifetime of 2.5 ꢀs, which still gives indication of a spin-forbidden
deactivation: emissive properties of the particles in aerated solution are therefore similar to those of
6
in powder at RT.
A DLS analysis evidenced a particle distribution with an average diameter of 430 nm and a
polydispersity index or circa 0.09. The colloid shows a great kinetic stability without the use of
polymeric stabilizers in solution: photophysical data are recorded on the same sample after 48 hours
without showing any significant differences.
1
7

ACCEPTED MANUSCRIPT
Conclusions
A series of six polysulfurated benzene derivatives 1-6 were synthesized and well characterized.
These asterisk molecules show negligible luminescence in both air-equilibrated and oxygen-free
solutions, but many are strong green phosphorescent emitters in the solid-state at 298 K (Φem up to
100%) or in a rigid matrix at 77 K. These molecules represent the first examples of a family of
highly phosphorescent organic materials, without the presence of heavy metal atoms, while
benefiting from Aggregation-Induced Phosphorescence Effect (AIPE) or Crystallization Induced
Emission (CIPE). The chemical structures determined from X-ray diffraction display different
crystal packing in their lattice, but more importantly, different conformers and rotamers in the
crystalline states. We thus believe that a conformational issue could also be responsible for the
differences observed in the phosphorescence emission and quantum yields in a rigid environment.
However, the restriction of molecular rotations and motions remains a major factor for observing
phosphorescence enhancement. A careful analysis of emission intensities in solution as a function
of the temperature, indicates that phosphorescence switches on at very close temperatures for three
hexasubstituted benzene derivatives 4-6, despite a size difference of the ortho groups, which can
affect the kinetic energy barrier involved in the intramolecular conformational change. This fact
supposes again a major role for the restriction of motions. Additionally, the intriguing
phosphorescent properties of these molecules can also be observed by synthesizing nanoparticles by
means of a simple reprecipitation method without using any stabilizing agent in solution.
We thus demonstrated that a new family of simple, easily available, and highly
phosphorescent luminogens contribute to further promote organic luminescent materials and solids,
without the use of heavy metals and their some strong disadvantages; e.g. environmental issues,
recycling, cost, cytotoxicity and world availability.
1
8

ACCEPTED MANUSCRIPT
Acknowledgments
This research is financially supported by the European Research Council ERC-StG (PhotoSi,
78912) and MIUR (FIRB RBFR10DAK6) in Italy. AF is grateful to a PhD scholarship obtained
2
from the Vinci program of the French–Italian University. MG, MR, RP and AF thank the French
National Center for Scientific Research (CNRS) and Aix-Marseille Université. We thank Dr. Guy
Félix for some help for HPLC. We are grateful to the Spectropole of Marseille, and to Dr. Michel
Giorgi for the X-ray structure studies.
References
1
Mutai T, Satou H, Araki K. Reproducible on-off switching of solid-state luminescence by controlling
molecular packing through heat-mode interconversion. Nature Mater. 2005; 4: 685-7.
Zhao Y, Gao H, Fan Y, Zhou T, Su Z, Liu Y, Wang Y. Thermally induced reversible phase
2
transformations accompanied by emission switching between different colors of two aromatic-amine
compounds. Adv. Mater. 2009; 21: 3165–9.
Shirota Y. Organic materials for electronic and optoelectronic devices. J. Mater. Chem. 2000; 10; 1-25.
3
4
Xiao L, Chen Z, Qu B, Luo J, Kong S, Gong Q, Kido J. Recent Progresses on Materials for
Electrophosphorescent Organic Light-Emitting Devices. Adv. Mater. 2011; 23: 926–52.
Yang Y, Su X, Carroll CN, Aprahamian I. Aggregation-induced emission in BF –hydrazone
5
2
(
BODIHY) complexes. Chem. Sci. 2012; 3: 610-3.
6
7
8
Zhou XJ, Chen C, Ren CX, Sun JK, Zhang J. Tunable solid-state photoluminescence based on proton-
triggered structural transformation of 4,4’-bipyridinium derivative. J. Mater. Chem. C 2013; 1: 744-50.
Grimsdale AC, Müllen K. The chemistry of organic nanomaterials. Angew. Chem. Int. Ed. 2005; 44:
5
592-629.
Liu H, Xu J, Li Y, Li Y. Aggregate nanostructures of organic molecular materials. Acc. Chem. Res.
010; 43: 1496-508.
2
9
1
Birks JB. Photophysics of aromatic molecules. London: Wiley; 1970.
0
Cornil J, dos Santos DA, Crispin X, Silbey R, Brédas JL. Influence of interchain interactions on the
absorption and luminescence of conjugated oligomers and polymers: a quantum-chemical
characterization. J. Am. Chem. Soc. 1998; 120: 1289-99.
Hong Y, Lam JWY, Tang BZ. Aggregation-induced emission: phenomenon, mechanism and
applications. Chem. Commun. 2009; 29: 4332-53.
Hong Y, Lam JWY, Tang BZ. Aggregation-induced emission. Chem. Soc. Rev. 2011; 40: 5361-88.
Chen J, Xie Z, Lam JWY, Law CCW, Tang BZ. Silole-Containing Polyacetylenes. Synthesis, thermal
stability, light emission, nanodimensional aggregation, and restricted intramolecular rotation.
Macromolecules 2003; 36: 1108-17
11
1
2
3
1
14
Zhao Q, Li L, Li F, Yu M, Liu Z, Yi T, Huang C. Aggregation-induced phosphorescent emission
(
AIPE) of iridium(III) complexes. Chem. Commun. 2008; 685-7.
1
5
Quartapelle Procopio E, Mauro M, Panigati M, Donghi D, Mercandelli P, Sironi A, D’Alfonso G, De
Cola L Highly Emitting Concomitant Polymorphic Crystals of a Dinuclear Rhenium Complex, J. Am.
Chem. Soc. 2010; 132: 14397–14399
See e.g.: a) Bolton O, Lee K, Kim HJ, Lin KY, Kim J. Activating efficient phosphorescence from
purely organic materials by crystal design. Nature Chem. 2011; 3: 205-10. b) Hirata S, Totani K,
16
1
9

ACCEPTED MANUSCRIPT
Zhang J, Yamashita T, Kaji H, Marder SR, Watanabe T, Adachi C. Efficient Persistent Room
Temperature Phosphorescence in Organic Amorphous Materials under Ambient Conditions. Adv.
Funct. Mater. 2013; 23: 3386-97. c) Xu J, Takai A, Kobayashia Y, Takeuchi M. Phosphorescence from
a pure organic fluorene derivative in solution at room temperature. Chem. Commun. 2013; 49: 8447-
4
9.
For hexakis(phenylthio)benzene Adams R, Reifschneider W, Nair MD. Croat. Chem. Acta 1957; 29:
77-85.
Adams R, Ferretti A. Thioethers from Halogen Compounds and Cuprous Mercaptides. II J. Am. Chem.
Soc. 1959; 81: 4927-31.
Gingras M, Pinchart A, Dallaire, C. Synthesis of p-Phenylene Sulfide Molecular Asterisks. Angew.
Chem. Int. Ed. 1998; 37:3149-51.
Gingras M, Raimundo JM, Chabre YM. Persulfurated aromatic compounds. Angew. Chem. Int. Ed.
17
2
1
8
19
20
21
2
006; 45: 1686–712.
Bergamini G, Fermi A, Botta C, Giovanella U, Di Motta S, Negri F, Peresutti R, Gingras M, Ceroni P.
A persulfurated benzene molecule exhibits outstanding phosphorescence in rigid environments: from
computational study to organic nanocrystals and OLED applications. J. Mater. Chem. C, 2013; 1:
2
717-24.
22
23
24
25
Gottlieb H E, Kotlyar V, Nudelman A. NMR chemical shifts of common laboratory solvents as trace
impurities. J. Org. Chem. 1997; 62: 7512-15.
De Mello JC, Wittmann HF, Friend RH. An improved experimental determination of external
photoluminescence quantum efficiency. Adv. Mater. 1997; 9: 230–2.
Tucker JHR, Gingras M, Brand H, Lehn J-M. Redox properties of polythiaarene derivatives. A novel
class of electron acceptors J. Chem. Soc. Perkin Trans. II 1997; 1303-07.
For previous syntheses of 1, see: (a) M. Arisawa, T. Suzuki, T. Ishikawa, M. Yamaguchi, Rhodium-
Catalyzed Substitution Reaction of Aryl Fluorides with Disulfides: p-Orientation in the
Polyarylthiolation of Polyfluorobenzenes J. Am Chem. Soc., 2008, 130, 12214-15; (b) Y. Suenaga, K.
Kitamura, T. Kuroda,-Sowa, M. Maekawa, M. Munakata, A zigzag chain coordination polymer
consisting of silver(I) ion having square planar geometry Inorg. Chim. Acta, 2002; 328: 105-10; (c) A.
D. U. Hardy, D. D. MacNicol, D. R. Wilson, A new approach for the design of inclusion compounds J.
Chem. Soc. Perkin Trans 2, 1979, 1011-19; (d) B. F. Malichenko, L.P. Robota, Zh. Org. Khim., 1975;
1
1: 778-82.
26
For previous syntheses of 2: (a) Suenaga Y, Kuroda-Sowa T, Maekawa M, Munakata M J.Chem.Soc.
Dalton Trans. 2000; 3620-23. (b) Pang L, Brisse F, Lucken EAC. Can. J. Chem. 1995; 73: 352-61.
Stack TDP, Holm RH. Subsite-differentiated analogs of biological [4Fe-4S] clusters: synthesis,
27
2+
solution and solid-state structures, and subsite-specific reactions. J. Am. Chem. Soc. 1988; 110: 2484-
9
4.
2
8
9
Maiolo F, Testaferri L, Tiecco M, Tingoli M. Fragmentation of aryl alkyl sulfides. A simple, one-pot
synthesis of polymercaptobenzenes from polychlorobenzenes. J. Org. Chem. 1981; 46: 3070-3.
MacNicol DD, Mallinson PR, Murphy A, Sym GJ. An efficient synthesis of hexa-substituted benzenes
and the discovery of a novel host conformation for hexakis (β-naphthylthio) benzene. Tetrahedron
Lett. 1982; 23: 4131-4.
2
30
McNicol DD. in Inclusion Compounds, (Atwood JL, Davies JED, MacNicol, DD. Edrs), Vol. 2, Chap.
5
, Structure and design of inclusion compounds: the hexa-hosts and symmetry considerations, Acad.
Press, London, 1984.
3
1
2
Montalti M, Credi A, Prodi L, Gandolfi MT. Handbook of Photochemistry. Boca Raton: Taylor &
Francis; 2006, chap. 3.
3
See e.g.: a) Zhou T, Li F, Fan Y, Song W, Mu X, Zhang H Wang Y. Hydrogen-bonded dimer stacking
induced emission of aminobenzoic acid compounds. Chem. Commun. 2009, 3199-201; b) Dong Y,
Lam JWY, Qin A, Li Z, Sun J, Sung HHY, Williams ID, Tang BZ. Switching the light emission of (4-
biphenylyl)phenyldibenzofulvene by morphological modulation: crystallization-induced emission
enhancement. Chem. Commun. 2007; 1, 40-2; c) Ren Y, Dong Y, Lam JWY, Tang BZ, Wong KS.
Studies on the aggregation-induced emission of silole film and crystal by time-resolved fluorescence
technique. Chem. Phys. Lett. 2005; 402, 468-73.
33
Virgili T, Forni A, Cariati E, Pasini D, Botta C, Direct Evidence of Torsional Motion in an
Aggregation-Induced Emissive Chromophore, J. Phys. Chem. C 2013; 117: 27161-66.
2
0

ACCEPTED MANUSCRIPT
34
See e.g.: Vitale S A, Katz J. L. Liquid Droplet Dispersions Formed by Homogeneous Liquid−Liquid
Nucleation:ꢀ “The Ouzo Effect” Langmuir, 2003; 19, 4105-4110.
2
1

ACCEPTED MANUSCRIPT
2
2

ACCEPTED MANUSCRIPT
Scheme 1. General synthesis of persulfurated benzene derivatives.
Figure 1. Chemical structures of phosphorescent molecular asterisks under study.
Figure 2. XRD structure of 1 (left) and 3 (right), ORTEP ellipsoids, 50% probability. Hydrogen atoms are omitted for
clarity.
Figure 3. XRD structure of 5 shows the same conformer (aabaab) in two different orientations. Sulfur atoms are
depicted in yellow, hydrogen atoms are omitted for clarity.
Figure 4. Crystal lattices and interplanar distances (Å) between central benzene rings in compounds 1-5.
Figure 5. (a) Absorption spectra of 1 (solid line), 2 (dashed line) and 3 (dashed-dotted line) in CH Cl solution at 298
2
2
K. (b) Absorption spectra of 4 (solid line), 5 (dashed line) and 6 (dashed-dotted) in CH Cl solution at 298 K.
2
2
Figure 6. Normalized emission spectra of (a) 1 (solid line), 2 (dashed line), 3 (dashed-dotted line) and (b) 4
solid line), 5 (dashed line) and 6 (dashed dotted line) in powder at 298 K. λ = 330 nm.
(
ex
Figure 7. (a) Normalized emission intensity changes at 510 nm of 4 (red circles), 5 (blue triangles) and 6 (green
squares) upon decreasing the temperature from 130 K to 95 K. (b) Changes in the emission band maximum upon
decreasing temperature from 140 K and 90 K. λ = 330 nm.
ex
Figure 8. (a) Emission spectra of 6 in butyronitrile upon decreasing the temperature from 180 K (red line) and 85 K
(
blue line). (b) Emission intensity changes of 6 in CH Cl :MeOH 1:1 (v/v) (blue circles) and butyronitrile (green
2 2
triangles) upon decreasing the temperature from 150 K to 85 K. λ = 330 nm.
ex
Figure 9. (a) Absorption (black solid line) and emission spectra (blue solid line) of a colloidal dispersion of 6 in air-
equilibrated THF-H O mixture at 298 K. For comparison purposes, the absorption spectrum of 6 in THF solution
2
(
dashed black line) and the emission spectrum of 6 in the solid phase (dashed blue line) are reported. λ = 330 nm. (b)
ex
Size distribution vs. recorded intensities (%) on an aqueous dispersion of 6; the green line refers to the cumulative
frequency distribution of the size of the nanoparticles.
2
3

ACCEPTED MANUSCRIPT
R
R
HS
R=
Cl
Cl
S
S
R
Cl
Cl
Cl
Cl
S
S
S
S
(
1) R= 4-Me,
R
R
(2) R= H,
(
(
(
(
3) R= 3-OMe,
4) R= 2-Me,
5) R= 2-iPr
Cs CO or NaH
2
2
3
0-100
C
O
6) R= 2-OMe,
R
R
MeN
NMe
6
3-90%
Scheme 1.
Figure 1
2
4

ACCEPTED MANUSCRIPT
Figure 2.
Figure 3.
2
5

ACCEPTED MANUSCRIPT
1
2
3
4
5
Figure 4.
2
6

ACCEPTED MANUSCRIPT
5
4
3
2
1
0
5
a
b
4
3
2
1
0
2
50
300
350
400
450
250
300
350
400
450
λ / nm
λ / nm
Figure 5.
1.0
0.8
0.6
0.4
0.2
0.0
1
0
.0
.8
a
b
0.6
0.4
0.2
0.0
4
50
500
550
600
650
450
500
550
600
650
λ / nm
λ / nm
Figure 6.
2
7

ACCEPTED MANUSCRIPT
5
70
60
1.0
0.8
0.6
0.4
0.2
0.0
a
b
5
550
540
530
520
510
500
100
110
120
130
100
110
120
130
140
T / K
T / K
Figure 7
3
0
a
1
.0
b
0
0
0
0
.8
.6
.4
.2
2
0
0
0
1
1
60
0.0
120
500
550
80
600
6
50
90
100
110
120
130
140
150
T / K
Figure 8.
2
8

ACCEPTED MANUSCRIPT
1.0
0.8
0.6
0.4
0.2
0.0
1
0
0
0
.0
.8
.6
.4
a
0.2
0.0
3
00
400
500
600
700
λ / nm
Figure 9.
2
9