Highly selective and sensitive Hg2+ fluorescent sensors based on a phosphane sulfide derivative

Article abstract of DOI:10.1039/b821682g

A series of fluorescent sensor molecules based on a phosphane sulfide derivative were designed and synthesized. The effect of the distance between the complex entities as well as the number and the length of fluorophores was investigated using both steady

Full text of DOI:10.1039/b821682g

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PAPER
www.rsc.org/obc | Organic & Biomolecular Chemistry
Highly selective and sensitive Hg2+ fluorescent sensors based on a phosphane
sulfide derivative
Minh-Huong Ha-Thi,a Mae¨l Penhoat,b Ve´ronique Michelet*b and Isabelle Leray*a
Received 3rd December 2008, Accepted 30th January 2009
First published as an Advance Article on the web 10th March 2009
DOI: 10.1039/b821682g
A series of fluorescent sensor molecules based on a phosphane sulfide derivative were designed and
synthesized. The effect of the distance between the complex entities as well as the number and the
length of fluorophores was investigated using both steady-state and time-resolved fluorescence
methods. The complexation behavior of these sensor molecules, which have a distinct affinity for Hg2+,
is reported. The coordination of Hg2+ induces a photoinduced electron transfer from fluorophore to the
complexed mercury and results in a significant decrease of the fluorescence. Theses sensors exhibit very
low detection limits in CH3CN/H2O (80/20 v:v) and excellent sensitivity to Hg2+ over other potentially
interfering cations such as Na+, K+, Mg2+, Ca2+, Cu2+, Ag+, Zn2+, Cd2+ and Pb2+.
Introduction
Mercury is certainly the most toxic of the heavy metals, and causes
environmental and health problems;1 a wide variety of symptoms
including digestive, kidney and especially neurological diseases
are observed upon exposure. Thus, the level of this detrimental
ion is the object of several official norms, the World Health
Organisation having established in 2004 a guideline for drinking-
water quality which included a mercury maximal value of 1 mg L-1.2
Currently the level of this detrimental ion is measured by analytical
techniques (atomic absorption, atomic emission and inductively
coupled plasma spectroscopy), which require complicated and
sophisticated instrumentation. The use of fluorescent molecular
sensors offers numerous advantages in terms of sensitivity, selec-
tivity, response time and low cost.3–5 A large number of fluorescent
molecular sensors for Hg2+ have therefore been proposed so far, but
many have limitations, including irreversibility, incompatibility
with aqueous solutions and lack of selectivity.6,7 Recently, some
examples that can overcome these problems have been described
in the literature, but the design of new efficient systems remains of
current interest.8–11
We have previously reported the synthesis and the photophysical
characterization of new fluorescent molecular sensors based
on phosphane oxide12,13 and phosphane sulfide derivatives.14,15
In particular, the compound DDPES1 was found to be very
selective and sensitive for the Hg2+ ion, the detection limit being
3.8 nM. Since there has been no previous study on such fluorescent
probes, we wished to evaluate the properties of a wider family,
varying the length and the number of the phenylethynyl arms
(Scheme 1, compounds 2 and 4). Anticipating that the nature
of the complexing unit might be of major importance, we also
Scheme 1 Fluorescent phosphane sulfide probes.
=
=
wanted to prepare a P O/P S mixed ligand 3. In order to study
the influence of steric hindrance, the preparation of fluorescent
sensors containing only two polyphenyl ethynyl fluorophores
(PSPO and PSPS) was targeted. In this paper, we report a detailed
study based on our preliminary research with the emphasis
on new derivatives (Scheme 1), their spectroscopic properties,
and a thorough investigation of cation-induced photophysical
changes and complexing properties, with the aim of studying the
relationship between the structures of the fluorescent molecular
sensors and their mercury-complexing ability.
Results and discussion
aInstitut d¢Alembert, Laboratoire PPSM (CNRS UMR 8531), ENS
Cachan, 61 Avenue du President Wilson, 94235, Cachan cedex, France.
E-mail: isabelle.leray@ppsm.ens-cachan.fr; Fax: +33 1 4740 2454; Tel: +33
1 4740 2704
Synthesis
Starting from the commercially available 4-bromotrimethylsilyl-
phenyl acetylene 6, phosphorylation using the Grignard derivative
in the presence of 1,2-bis(dichlorophosphano)ethane afforded the
formation of tetraarylated phosphanes (Scheme 2). Treatment
with elemental sulfur gave the thiophosphano product, which
bLaboratoire de Synthe`se Se´lective Organique et Produits Naturels,
E.N.S.C.P., UMR7573, 11 rue P. et M. Curie, 75231, Paris Cedex
05, France. E-mail: veronique-michelet@enscp.fr; Fax: +33 14407 1062;
Tel: +33 1 4427 6744
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Table 1 Photophysical properties of thiophosphano derivatives in
CH3CN/H2O (9:1 with DPPES2 and 8:2 with the others)
a
Product
labs /nm
e/104 M-1 cm-1
lem/nm
UF
PS3 (5)
336
313
334
334
335
15
15
20
12
11
444
405
440
440
437
0.54
0.1
0.32
0.55
0.32
DPPES1 (1)
DPPES2 (2)
PSPO (3)
PSPS (4)
a Maxima of the absorption labs (nm) and of steady-state emission lem (nm),
molar absorption coefficient e (104 M-1 cm-1), and fluorescence quantum
yield UF (with 10% error).
Scheme 2 Syntheses of DPPES1 (1) and DPPES2 (2) ligands.
was then desilylated. The resulting phosphane sulfide 715 was a
key intermediate for the preparation of 1 and 2. The Sonogashira
cross-coupling16 between the phosphano product 7 and the iodides
8a17 or 8b was then performed in the presence of 10 mol% of Pd
catalyst and 10 mol% of copper iodide and led to the desired
ligands 1 and 2 in 50% and 33% yield, respectively.
In order to study the influence of the number of fluorescent
arms for the complexation properties, we also synthesized the
non-symmetrical derivatives 3 and 4 (Scheme 1). The structures
of these ligands were also designed for a comparison of the
affinity toward the mercury ion between the phosphane oxide and
sulfide groups. As the desymmetrization step was not possible
starting from 7, we decided to take advantage of the func-
tionalization of methyldichlorophosphane (9). Scheme 3 shows
the complete synthetic pathway for the two non-symmetrical
derivatives PSPO and PSPS. The classic Grignard derived from
(4-bromophenyl)trimethylsilylacetylene 6 was phosphorylated
with methyldichlorophosphine (9).13 The phosphorus atom was
sulfurized in the presence of elemental sulfur in toluene to give the
thiophosphano product 10 in 86% yield. Then, a treatment with
a hindered base, lithium 2,2,6,6-tetramethylpiperidine (LTMP),18
followed by the addition of chlorodiphenylphosphane oxide
Scheme 3 Syntheses of the ligands PSPO (3) and PSPS (4). Reagents and
conditions : i) Mg, THF, 50 ◦C, 1.5 h then Cl2PCH3 (9), THF, RT, 18 h, 46%;
ii) S8, toluene, 95 ◦C, 4 h, 86%; iii) LTMP (2.3 equiv), THF, RT, -40 ◦C,1 h
30 min then Ph2P(O)Cl (1.1 equiv), -40 ◦C, THF, 4 h (53%). iv) K2CO3
(2 equiv), CH2Cl2, MeOH, RT, 4 h, 92%; v) a) LTMP (2.3 equiv), THF, RT,
-40 ◦C, 1 h 30 min then Ph2PCl (1.1 equiv), -40 ◦C, THF, 4 h, b) S8, toluene,
95 ◦C, 4 h, 22%; vi) K2CO3 (2 equiv), CH2Cl2, MeOH, RT, 4 h, 97%;
∫
vii) 6 mol% Pd(PPh3)4, 12 mol% CuI, I–C6H4–C C–C6H4–O(CH2)3CO2Et
(8b), Et3N, toluene, 50 ◦C, 64% (X = O), 36% (X = S).
are summarized in Table 1. All the fluorophores show an intense
absorption band in the near-UV region. The absorption spectra
of the long-arm fluorophores (DPPES2 (2), PSPO (3) and PSPS
(4)) are similar to the reference fluorophore PS3 (5). The molar
absorption coefficient at the maximal absorption wavelength is
almost proportional to the number of fluorescent arms, indicating
a weak interaction between the chromophores in the ground state.
Only in the case of short fluorescent arm compound DPPES1
(1) is a blue shift observed, as a result of the decrease in the
p-conjugated chain. The fluorescence of the compounds are
intense in the visible region, with quantum yields ranging from
0.1 to 0.54. A large Stokes shift and the unresolved vibronic
structure of the fluorescence spectra of the compounds indicate
the formation of an intramolecular charge transition. A blue shift
and a decrease in the fluorescence quantum yield are observed
for the fluorophore DPPES1 (1) due to the decrease of the
chromophoric length. However, this compound could be inter-
esting thanks to its better solubility in organoaqueous solvents
(CH3CN/H2O).
=
=
gave the mixed P O/P S ligand in 53% yield. The addition of
chlorodiphenylphosphane followed by a phosphorus sulfuriza-
tion step led to the disulfide phosphane ligand in 22% yield.
Desilylation using K2CO3 in CH2Cl2/MeOH afforded the desired
phosphane sulfides 11 and 12 in 92% and 97% yields, respectively.
Sonogashira cross-coupling reactions between the thiophosphano
products 11/12 and the iodide 8b were then performed in the
presence of 6 mol% palladium catalyst and 12 mol% copper
iodide, affording the final thiophosphanes PSPO (3) and PSPS
(4) in 64% and 36% isolated yields, respectively. Phosphane
sulfide PS3 (5) was prepared according to a previously described
procedure.14
Photophysical properties of the ligands
The absorption and fluorescence spectra of the thiophosphano
ligands are shown in Fig. 1 and their photophysical characteristics
In order to have further information on the photophysical
properties of the fluorophores, we performed time-resolved
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Table 2 Analysis of the fluorescence decays of thiophosphano derivatives in CH3CN/H2O (8:2 and 9:1 for DPPES2 (2)) (lexc = 330 nm)
2
Product
lem/nm
t1/ns
a1
t2/ns
a2
t3/ns
a3
c
R
DPPES1 (1)
370
400
450
400
444
500
444
440
500
0.32
0.32
0.32
1.03
1.03
1.03
1.24
1.16
0.86
0.52
0.59
0.70
0.70
0.80
0.71
1.00
1.00
0.92
4.05
4.05
4.05
6.14
6.14
6.14
—
0.00
0.01
0.03
0.05
0.03
0.04
—
0.02
0.02
0.02
0.25
0.25
0.25
—
0.48
0.40
0.27
0.17
0.19
0.19
—
1.41
1.37
1.33
1.04
1.10
1.14
1.21
1.19
1.3
DPPES2 (2)
PS3 (5)
PSPO (3)
PSPS (4)
—
0.23
—
0.08
—
—
—
—
Fig.
2
Fluorescence decays of the thiophosphano derivatives in
CH3CN/H2O 8:2 and 9:1 (DPPES2 (2)), lexc= 330 nm.
the fluorescence decays of DPPES1 (1) and DPPES2 (2) are
more complicated and tri-exponential model is needed to obtain
satisfactory fits. Time-resolved fluorescence measurements were
done at different observation wavelengths and global analysis was
used to fit the decays. The obtained decay times and preexponential
factors fitted are displayed in Table 2. As we demonstrated in the
case of phosphane oxide fluorophores,13 the three components
observed for the symmetric thiophosphano derivatives could be
explained in the following way. Considering at first the long
fluorescent arm derivative DPPES2 (2), the medium component of
around 1 ns, which is very close to the lifetime of PS3 (5) or PSPO
(3), may be attributed to the emission of the monomer. The longer
component (6.1 ns), dominating at the long-wavelength part of the
spectra, is assumed to correspond to an excimer formation. The
shortest component (0.25 ns) could be attributed to the decay of
the monomer able to form an excimer.19,20 The same behaviour can
be found in the case of short fluorescent arm derivative DPPES1
(1). The only difference is that the time constants are shorter due
to the decrease of the fluorophore length. All these data suggest,
as previously observed for phosphane oxide derivatives,13 the
presence of different conformers: one may envisage the presence
of an expanded structure (leading to monomer emission) and
a sandwich-like geometry (responsible for preformed excimer
emission).
Fig. 1 Absorption spectra (a) and corrected normalized emission spectra
(b) of thiophosphano derivatives in CH3CN/H2O (8:2 and 9:1 with
DPPES2 (2)). lexc = 340 nm for PS3, PSPO, PSPS, lexc = 324 nm for
DPPES1 and lexc = 343 nm for DPPES2.
fluorescence measurements by the single-photon counting method
with picosecond laser excitation. The fluorescence decays of
the compounds are displayed in Fig. 2. Satisfactory fits can
2
be obtained by considering a single exponential (c < 1.25)
R
for the reference compound PS3 (5) and the non-symmetrical
derivative PSPO (3). Those results suggest the presence of only one
emitting species, as in the case of phosphane oxide derivatives.13
The fluorescence decay of PSPS (4) is almost mono-exponential
in form, with only a small secondary component. In contrast,
Cation-induced photophysical changes
Complexation studies of mercury with PSPO (3), PSPS (4) and
DPPES1 (1) were performed in a mixture CH3CN/H2O 8:2 at
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pH 4.0 with practical applications in mind.6 The choice of pH 4
was made in order to prevent precipitation of the mercury cation
(especially for the stock solution for the complexation studies).
Furthermore, since these compounds do not contain any pH-
sensitive function, no effect was observed upon changing the pH
of the solution. For the symmetric long-arm derivative DPPES2
(2), CH3CN/H2O 9:1 at pH 4.0 was used because of inade-
quate solubility of the compound with four long phenylethynyl
arms.
The evolution of the absorption spectra (a) and the emission
spectra (b) of PSPO (3) and PSPS (4), upon complexation with
Hg2+ are displayed in Fig. 3 and Fig. 4, respectively. The insets in
Fig. 3b and Fig. 4b show a decrease of the fluorescence intensity at
438 nm upon progressive addition of Hg2+. Mercury complexation
induces a bathochromic shift of the absorption spectra, because
of an enhancement of the electron-withdrawing character of the
phosphane sulfide and oxide groups due to interaction of their
oxygen and sulfur atoms with the Hg2+. A strong decrease of the
fluorescence is observed upon mercury complexation for these
two compounds, which can be attributed to an electron transfer
between the excited fluorophore to the complexed mercury cation,
as previously shown for the DPPES1 (1).15
Fig. 4 Absorption (7.1 ¥ 10-6 M) (a) and corrected emission (3.0 ¥ 10-7 M)
(b) spectra of PSPS (4) in the presence of an increasing concentration of
Hg2+ in CH3CN/H2O 8:2 at pH 4.0. lexc = 344 nm. Inset: Calibration curve
as a function of mercury concentration.
Global analysis of the evolution of the absorption and the emis-
sion spectra upon mercury binding (by means of the SPECFIT
program) reveals that the formation of complexes of different
stoichiometries (1:2, 1:1 and 2:1); the apparent stability constants
are provided in Table 3.
For the PS3 (5) ligand, two complexes are successively formed
with stoichiometries of 1:2 (ML2) and 1:1 (ML). These stoichiome-
tries have been previously reported for mercury complexes with
Table 3 Stability constantsa of thiophosphano derivatives with mercury
Product
logb11 (HgL)a
logb12 (HgL2)
logb21 (Hg2L)
PS3 (5)
5.0 0.2
8.2 0.1
8.4 0.4
10.7 0.4
6.9 0.2
11.7 0.1
—
15.5 0.5
19.2 0.6
—
—
—
PSPO (3)
DPPES1 (1)
PSPS (4)
13.8 0.4
16.5 0.4
13.8 0.2
DPPES2 (2)
a
Fig. 3 Absorption (7.1 ¥ 10-6 M) (a) and corrected emission (9.6 ¥ 10-7 M)
(b) spectra of PSPO (3) in the presence of an increasing concentration of
Hg2+ in CH3CN/H2O 8:2 at pH 4.0. lexc = 344 nm. Inset: Calibration curve
as a function of mercury concentration.
È
˘
j
] [ ]
MiLj
Î
˚
bij =
i
M
L
[
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21–23
=
the thiophosphano derivatives R3P S (R = Me and Ph).
As
previously shown for DPPES1 (1), the three complexes were
formed successively, with very high stability constants in the
case of PSPS (4). The observed stoichiometries are in agree-
ment with the results previously reported on the compound
Ph2P(S)CH2P(S)Ph2.23 The stability constants of PSPS (4) with
mercury are slightly higher than those found for DPPES1 (1),
probably because of the higher flexibility with the compound
containing only two phenylethynyl groups. In contrast, the
complexation with mercury is less effective with DPPES2 (2)
compared to DPPES1 (1) because of higher steric hindrance. Thus
the formation of a ML2 complex has not been observed for this
compound.
In contrast, the formation of only one complex with a 1:1
stoichiometry is observed with PSPO (3). As can be seen from
Fig. 3a, there is a clear isobestic point at 344 nm, which indicates
the presence of a single evolution from 0 to 1 equivalents
corresponding to the formation of a single 1:1 complex. Its stability
constant is also lower than in the case of DPPES1 (1) or PSPS
(4), which can be explained by the preference of mercury for the
softer sulfur atom rather than the harder oxygen atom.24 This is
also the reason why a complex ML2 is not observed for PSPO (3),
since the affinity of the phosphine oxide group for mercury is not
sufficient to form a complex.
The calibration curves shown in the inset of Fig. 3b and Fig. 4b
represent the fluorescence intensities at 438 nm as a function of
Hg2+ concentration for PSPO (3) and PSPS (4). The detection
limits, calculated as three times the standard deviation of the
background noise, were found to be 4.8 mg L-1 (23.9 nM) and
1.8 mg L-1 (8.9 nM) for PSPO (3) and PSPS (4), respectively.
These values are slightly higher than that obtained for DPPSE1
(1), but they remain close to the level defined by the World
Health Organization.2 A linear response as a function of mercury
concentration was obtained from 0 to 162 and 200 mg.L-1 for
PSPO (3) and PSPS (4), respectively.
Fig. 6 Absorption (a) and emission (b) spectra (lexc = 340 nm) of PSPS
(4) and its complexes in CH3CN/H2O 8:2 at pH 4.0.
was observed upon addition of a large excess of these interfering
cations. Except for Ag+ with PSPS (4), the stability constants of
the complexes of these ions were too low to be determined. The
stability constants obtained in the case of Ag+ complexes with
PSPS (4) were logK11 = 6.1 and logK12 = 11.1. The selectivity
toward Hg2+, expressed as the ratio of the apparent stability
constants, was found to be higher than 104. In contrast to PSPS
(4), this ion induced no significant effect on the absorption and
fluorescence of PSPO (3) ligand, because of the weak interaction
of the phosphine oxide group with this cation. The compound
PSPO (3) consequently shows an outstanding performance
in terms of selectivity towards Hg2+ over all the interfering
cations.
The competition-based fluorescence profiles for these cations
are shown in Fig. 7 and Fig. 8 for PSPO (3) and PSPS
(4), respectively. No significant change of the sensor response
is observed despite a large excess of interfering cations being
added. Only Cd2+ slightly modifies the fluorescence response with
PSPO (3). This behavior was not observed in the case of PSPS
(4) derivative, which can be explained by the better affinity of
cadmium for the phosphane oxide groups than the phosphane
sulfide groups. In contrast with PSPS (4), the addition of Ag+ in
large excess (10-3 M) does not modify the complexation of PSPO
(3) with Hg2+.
The binding abilities of PSPO (3) and PSPS (4) over a
range of other cations including alkali (Na+, K+), alkaline-earth
(Ca2+, Mg2+) and transition metal ions (Cd2+, Pb2+, Cu2+, Zn2+,
Ag+) were evaluated. Fig. 5 and Fig. 6 show the fluorescence
spectra of these fluorophores and their complexes, determined by
titration experiments. No significant change of the fluorescence
Fig. 7 IF/I0 response of PSPO (3) (lexc = 340 nm, lem = 438 nm) in
CH3CN/H2O (8:2 v/v) at pH = 4 in the presence of Hg2+ (1.5 mM) and
interfering ions Na+, K+, Ca2+ at 1 mM; Zn2+, Ag+ at 0.1 mM; Cu2+, Cd2+
Pb2+ at 0.05 mM.
,
In the case of PSPS (4) derivative, we have observed that Ag+
was the main interfering ion. However, the addition of mercury
Fig. 5 Absorption (a) and emission (b) spectra (lexc = 344 nm) of PSPO
(3) and its complexes in CH3CN/H2O 8:2 at pH 4.0.
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0.04–0.063 mm Art. 11567 silica gel. 1H NMR, 13C NMR, and 31
P
NMR were recorded on Bruker AV 300 or AV 400 instruments.
All signals were expressed as ppm downfield from Me4Si for
1H and 13C NMR and from H3PO4 for 31P NMR used as an
internal standard (d). Coupling constants (J) are reported in Hz
and refer to apparent peak multiplicities. Melting points were
measured in open capillary tubes. Mass spectrometry analyses
were performed at the Ecole Nationale Supe´rieure de Chimie de
Paris by using a Hewlett-Packard HP 5989 A instrument. Direct
introduction experiments were performed by chemical ionization
with ammonia. Elemental analyses and high-resolution mass
spectra were performed at the Institut de Chimie des Substances
Naturelles.
Fig. 8 IF/I0 response of PSPS (4) (lexc = 340 nm, lem = 438 nm) in
CH3CN/H2O (8:2 v/v) at pH = 4 in the presence of Hg2+ (0.6 mM) and
interfering ions Na+, K+, Ca2+ at 1 mM; Zn2+, Cd2+ at 0.05 mM and Ag+,
Pb2+, Cu2+ a` 10-5 M.
always leads to fluorescence quenching thanks to its higher affinity
constant of Hg2+ than Ag+. The Fig. 8 shows a remarkably high
selectivity of the PSPS for Hg2+.
Synthesis
Methylene-bis(4-trimethylsilylethynylphenyl)phosphane.
To
569 mg (43 mmol) of activated Mg under argon, a solution
of (4-bromophenylethynyl)trimethylsilane (5.41 g, 21.3 mmol) in
anhydrous THF (12.5 ml) was added in one portion. The mixture
was then heated at 55 ◦C for 2h and then canulated to a solution
of C◦H3PCl2 (942 ml, 10.65 mmol) in anhydrous THF (12.5 ml)
Conclusion
We have described the synthesis, the photophysical and complex-
ing properties of a new family of fluorescent molecular sensors
based on phosphorus ligands. The photophysical studies revealed
interesting properties of this new family: an intense absorption
band in near-UV region and an intense fluorescence band in
the visible region. Time-resolved fluorescence experiments clearly
demonstrated that the non-symmetrical ligands (PSPO (3) or
PSPS (4)) behave like the mono-thiophosphane compound PS3
(5): there is therefore no interaction between the chromophores
in these multichromophoric fluorophores. However, as previously
observed for the phosphane oxide ligand, interactions between the
fluorescent arms have been revealed for the symmetrical ligands
(DPPES1 (1), DPPES2 (2)), through the presence of several time
constants in the fluorescence decays.
◦
at 0 C. The reaction mixture was stirred at 0 C for 30 minutes
and then for 18h at room temperature. The reaction was then
quenched with a solution of saturated aqueous NH4Cl (20 ml)
and water (5 ml). After extraction, drying (Na2SO4), and filtration,
the volatiles were evaporated and the crude oil was purified
by flash chromatography (eluant: CH2Cl2–dichloromethane 9:1)
to afford the corresponding product as a white solid (1.92 g,
46%).
M.p. 114 C. H NMR (CDCl3, 300 MHz): d 7.39 (m, 4H),
7.31 (m, 4H), 1.58 (d, 3H, J = 3.52 Hz), 0.24 (s, 18H). 13C NMR
(CDCl3, 75 MHz): d 140.8, 140.6, 132.1, 131.9, 131.8, 126.8, 123.3,
104.8, 95.4, 12.59, 12.3, 0.0. 31P NMR (CDCl3, 121 MHz): d -25.6.
MS (ESI): C23H29PSi2: m/z: 392 [M + H]+.
◦
1
The fluorescent molecular sensors PSPS (4), PSPO (3) and
DPPES1 (1) showed remarkable sensitivity to and selectivity for
Hg2+ in acetonitrile/water media. The addition of mercury ions to
solutions of these compounds induces an significant bathochromic
shift of the absorption spectra and a complete quenching of the
fluorescence spectra. The selectivity of these systems for Hg2+ over
other metal ions is remarkably high, and their estimated detection
limit is compatible with the level defined by the World Health
Organization for drinking water.
Methylene-bis(4-trimethylsilylethynylphenyl)phosphane sulfide
10. To
a solution of methylene-bis(4-trimethylsilylethynyl-
phenyl)phosphane (1.923 g, 4.9 mmol) in toluene (80 ml), 156 g
(4.9 mmol) of S8 were added and the reaction was heated at 95 ◦C
for 4h under argon. The solvent was evaporated under reduced
pressure and the crude yellow solid was purified by filtration on
a short pad of silica gel (eluant: AcOEt) to afford a white solid
(1.78 g, 86%).
◦
1
M.p. 124 C. H NMR (CDCl3, 300 MHz): d 7.52 (m, 4H),
7.25 (m, 4H), 2.24 (d, 3H, J = 13.23 Hz), 0.25 (s, 18H). 13C
NMR (CDCl3, 75 MHz): d 134.3, 133.2, 132.3, 132.1, 130.8,
130.6, 126.8, 103.8, 97.8, 22.1, 21.3, 0.0. 31P NMR (CDCl3,
121 MHz): d 35.7. MS (ESI): C23H29PSi2S: m/z: 424 [M + H]+.
HRMS (TOF MALDI) calcd for C23H29PSi2SNa 447.1164, found
447.1191 [M + Na]+.
Experimental section
General
Reagents were commercially available from Acros, Aldrich, or
Avocado and were used without further purification unless oth-
erwise stated. Chloroform and acetonitrile (spectrometric grade
from Aldrich or SDS) were employed as solvents for absorption
and fluorescence measurements. Sodium thiocyanate, potassium
thiocyanate, calcium perchlorate, zinc perchlorate, cadmium per-
chlorate, lead(II) perchlorate, silver(I) perchlorate and mercury(II)
perchlorate, from Aldrich or Alfa Aesar, were of the highest quality
available and were vacuum-dried over P2O5 prior to use. The
solution at pH 4.0 was prepared with perchloric acid (99.99%)
in water. Column chromatography was performed with E.Merck
Bis(4-trimethylsilylethynylphenyl)phosphanthioyl-diphenylphos-
phanoylmethane. A solution of LTMP was prepared for 5 min-
utes at 0 ◦C from n-BuLi (2.5 M) (460 ml, 1.15 mmol) and TMPH
(195 ml, 1.15 mmol) in 1 mL◦of THF under argon. This solution
was then cannulated at -40 C to a solution of methylene-bis(4-
trimethylsilylethynylphenyl)phosphane sulfide (212 mg, 0.5 mmol)
in THF (2 mL) under argon. The mixture was stirred for 1h30
at 40 ◦C and 114 ml (0.6 mmol) of diphenylphosphinic chloride
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were added dropwise to this solution at -40 ◦C under argon.
The solution was stirred for 4h at -40 ◦C then quenched with
saturated aqueous NH4Cl solution (5 ml) and extracted with
dichloromethane (5 ml). The organic layer was dried (Na2SO4),
filtered and evaporated under reduced pressure. The crude yellow
solid was purified by flash chromatography (eluant: CH2Cl2 to
CH2Cl2/AcOEt 9:1, Rf(CH2Cl2) = 0.2) to afford the correspond-
ing product as a white solid (166 mg, 53%). M.p. 202 ◦C. 1H NMR
(CDCl3, 300 MHz): d 7.84 (m, 4H), 7.62 (m, 4H), 7.48 (m, 2H), 7.39
(m, 8H), 3.71 (m, 2H), 0.28 (s, 18H). 13C NMR (CDCl3, 75 MHz): d
133.2, 132.2, 132.0, 131.9, 131.9, 131.7, 131.1, 131.0, 130.8, 128.8,
128.6, 126.9, 126.9, 104.0, 97.7, 39.2, 38.6, 38.5, 37.9, 0.0. 31P NMR
(CDCl3, 121 MHz): d 36.0 (d, J = 16 Hz), 23.4 (d, J = 16 Hz). MS
(IC): C35H38OP2SSi2: m/z: 624 [M + H]+. HRMS (MALDI) calcd
for C35H39OP2SSi2 625.1730, found 625.1752 [M + H]+.
Bis(4-ethynylphenyl)phosphanthioyl-diphenylphosphane thioyl
methane 12. According to the experimental procedure to pre-
pare bis(4-ethynylphenyl)phosphanthioyl-diphenyl phosphanoyl
methane and starting from a solution of bis(4-trimethylsilyl-
ethynylphenyl)phosphinthioyl-diphenyl phosphanthioylmethane
(160 mg, 0.25 mmol) in mmol in a mixture of dichloromethane
(2 ml) and MeOH (4 ml) with 68 mg (0.1 mmol) of K2CO3, 121 mg
of desired product was obtained as a white solid (97%). M.p.
86 C. H NMR (CDCl3, 300 MHz): d 7.59–7.66 (m, 8H), 7.19-
7.29 (m, 10H), 3.81 (t, 2H, J = 13.4 Hz), 3.05 (s, 2H). 13C NMR
(CDCl3, 75 MHz): d 131.3, 131.2, 131.1, 130.5, 130.3, 130.2,
130.1, 130.0, 129.8, 127.3, 127.1, 127.0, 124.3, 81.1, 78.7, 37.6
(t, J = 44.3 Hz). 31P NMR (CDCl3, 121 MHz): d 35.1 (d, J =
14 Hz), 35.0 (d, J = 14 Hz). MS (IC): C29H22P2S2: m/z: 496
[M + H]+.HRMS (ES) calcd for C29H22P2S2Na : 519.0536, found
519.0541 [M + Na]+.
◦
1
Bis(4-trimethylsilylethynylphenyl)phosphanthioyl-diphenyl phos-
phanthioylmethane. According to the experimental procedure
to prepare bis(4-trimethylsilyl ethynylphenyl)phosphanthioyl-
diphenyl phosphanoyl methane, and starting from the solu-
tion of LTMP (1.15 mmol in 1 ml of THF), the methylene-
bis(4-trimethylsilylethynylphenyl)phosphane sulfide (212 mg,
0.5 mmol), the diphenylphosphane chloride Ph2PCl (104 mL,
0.6 mmol), the phosphane product was obtained. This product
was not isolated and directly engaged in the sulfuration with
S8 (1 equiv.) added dropwise after solubilisation in toluene.
The mixture was then stirred at 95 ◦C for 4h. Then volatiles
were evaporated and the corresponding mixture of phosphane
sulfide (2/3) and phosphane oxide (1/3) was purified by flash
chromatography (eluant: cyclohexane/CH2Cl2 1:1) and trituration
with a small amount of AcOEt to afford 70 mg (22%) of the
desired product as a white solid. M.p. 91 C. H NMR (CDCl3,
300 MHz): d 7.75 (m, 8H), 7.36 (m, 10H), 3.93 (t, 2H, J = 13.4 Hz),
0.25 (s, 18H). 13C NMR (CDCl3, 75 MHz): d 132.8, 132.7, 132.5,
132.4, 132.3, 132.2, 131.8, 131.8, 131.7, 131.7, 131.6, 131.6, 131.3,
131.2, 131.1, 131.1, 131.0, 130.9, 128.8, 128.6, 128.5, 126.9, 126.8,
103.9, 97.8, 39.4, 0.0. 31P NMR (CDCl3, 121 MHz): d 35.2 (d, J =
14 Hz), 34.8 (d, J = 14 Hz). MS (IC): C35H38P2S2Si2: m/z: 640
[M + H]+. HRMS (MALDI) calcd for C35H39P2S2Si2 : 641.1502,
found 641.1478 [M + H]+.
Bis-4-[ethyl4-(4-di(phenyleneethynylene)-phenoxy)butyrate]
phosphinthioyl-diphenylphosphynoyl methane PSPO (3). To a
solution of bis(4-ethynylphenyl)phosphanthioyl-diphenyl phos-
phanoylmethane (40 mg, 0.083 mmol) and in toluene (4 ml) and
triethylamine (2 ml), 130 mg of 8b (0.30 mmol, 3.6equiv.) are
added. The mixture is degassed under argon and CuI (2 mg,
12 mol%) and Pd(PPh3)4 (5 mg, 6 mol%) are added quickly. The
reaction mixture is then stirred for 20h at 50 ◦C under argon. The
volatiles are evaporated in vacuo and the residue is dissolved in
dichloromethane (10mL). The organic layer is washed with HCl
(10%), dried (Na2SO4), filtrated and the solvents are evaporated
under reduced pressure. The crude product is then purified by flash
chromatography (silica gel: CH2Cl2 100% to CH2Cl2/acetone 1:1)
to afford the desired product PSPO (58 mg, 64%) as an yellow
solid. M.p. 147 ◦C. 1H NMR (CDCl3, 300 MHz): d 7.81–7.88 (m,
4H), 7.51–7.58 (m, 4H), 7.28–7.45 (m, 22H), 6.78 (d, J = 8.81 Hz,
4H), 4.07 (q, 4H, J = 7.2 Hz), 3.95 (t, 4H, J = 6.1 Hz), 3.69
(dd, J = 13 Hz and 15 Hz), 2.43 (t, 4H, J = 7.34 Hz), 2.03 (m,
4H), 1.17 (t, J = 7.2 Hz, 6H). 13C NMR (CDCl3, 75 MHz): d
173.1, 159.1, 133.1, 132.0, 131.9, 131.8, 131.7, 131.5, 131.4, 131.2,
130.8, 130.7, 128.7, 128.5, 126.8, 126.7, 124.1, 122.0, 115.1, 114.6,
91.9, 91.8, 90.1, 87.8, 66.8, 60.5, 38.3, 30.7, 24.6, 14.2. 31P NMR
(CDCl3, 121 MHz): d 36.2 (d, J = 15 Hz), 23.4 (d, J = 13 Hz).
HRMS (TOF MALDI) calcd for C69H59O7P2S [M]+ 1093.3471,
found. 1093.3451.
◦
1
Bis(4-ethynylphenyl)phosphanthioyl-diphenylphosphanoyl me-
thane 11. To a solution of bis(4-trimethylsilylethynylphenyl)-
phosphanthioyl-diphenylphosphanoylmethane
(160
mg,
Bis-4-[ethyl 4-(4-di(phenylene ethynylene)-phenoxy)butyrate]
phosphanthioyl-diphenylphosphanthioylmethane PSPS (4). To a
solution of bis(4-ethynylphenyl)phosphinthioyl-diphenyl phos-
phinthioylmethane (47 mg, 0.09 mmol) and in toluene (4 ml)
and triethylamine (2 ml), 123 mg of 8b (0.28 mmol, 3.2equiv.)
are added. The mixture is degassed under argon and CuI (2 mg,
12%mol) and Pd(PPh3)4 (5 mg, 6%mol) are added quickly. The
reaction mixture is then stirred for 20h at 50 ◦C under argon. The
volatiles are evaporated in vacuo and the residue is dissolved in
dichloromethane (10mL). The organic layer is washed with HCl
(10%), dried (Na2SO4), filtrated and the solvents are evaporated
under reduced pressure. The crude product is then purified by
flash chromatography (silica gel: CH2Cl2 100% to CH2Cl2/acetone
1:1) to afford the desired product (36 mg, 36%) as an yellow
solid.
0.26 mmol) in a mixture of dichloromethane (2 ml) and
MeOH (4 ml), 77 mg (0.1 mmol) of K2CO3 were added and the
reaction was stirred at room temperature for 4h. After complete
conversion 4 mL of water were added and the mixture was
extracted with dichloromethane (5 mL). The organic layer was
then dried (Na2SO4), filtrated and evaporated in vacuo. The crude
oil was then triturated in Et2O/cyclohexane (1:1) to afford a white
solid (116 mg, 92%).
◦
1
M.p. 193 C. H NMR (CDCl3, 300 MHz): d 7.83–7.91 (m,
4H), 7.54–7.61 (m, 4H), 7.32–7.43 (m, 8H), 3.71 (dd, J = 15 Hz
and 15 Hz, 2H), 3.19 (s, 2H). 13C NMR (CDCl3, 75 MHz): d
131.9, 131.8, 131.7, 130.7, 130.6, 128.6, 128.5, 82.6, 79.9, 39.0,
38.4, 38.3, 37.7. 31P NMR (CDCl3, 121 MHz): d 36.1 (d, J =
16 Hz), 23.4 (d, J = 15 Hz). MS (IC): C29H22OP2S: m/z: 480
[M + H]+. HRMS (ES) calcd for C29H22OP2SNa: 503.0764, found
503.0796 [M + Na]+.
M.p. 111 ◦C. 1H NMR (CDCl3, 300 MHz): d 7.76–7.69 (m, 8H),
7.42–7.28 (m, 20H), 6.78 (dd, 4H, J = 1.8 Hz and 8.8 Hz,), 4.07
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(q, 4H, J = 7.2 Hz), 3.97–3.87 (m, 6H), 2.44 (t, 4H, J = 7.3 Hz,),
2.04 (m, 4H), 1.18 (t, 6H, J = 7.2 Hz,). 13C NMR (CDCl3, 75 MHz):
d 173.1, 159.1, 133.1, 132.7, 132.6, 132.5, 132.2, 132.1, 132.0, 131.8,
131.7, 131.6, 131.4, 131.3, 131.2, 131.0, 130.9, 128.5, 128.3, 126.7,
126.7, 124.1, 122.0, 115.0, 115.0, 114.6, 92.0, 91.8, 90.0, 87.8, 66.8,
60.5, 39.9, 39.3, 38.7, 30.7, 24.5, 14.2. 31P NMR (CDCl3, 121
MHz): d 35.3 (d, J = 14 Hz), 35.1 (d, J = 14 Hz). MS (FIA)
C69H59O7P2S: m/z: [M-H]+ 1109.
non-linear regression modeling by the Levenberg–Marquardt
method.26
Acknowledgements
This work was supported by the National Research Agency
program CP2D ”FLUOSENSIL”. We are grateful to J.-P. Lefevre
and J.-J. Vachon for their assistance in tuning the single-photon
timing instrument. M.H.H.T. is grateful to the Ministe`re de
l’Education et de la Recherche for a grant (2004–2007). M.P.
thanks the CNRS for a post-doctoral grant (2005–2006).
Ethylene 1,2-bis-4-[ethyl 4-(4-di(phenylene ethynylene)-phe-
noxy)butyrate]diphosphane sulfide DPPS2 (2). To a solution of
ethylene 1,2-bis(4-trimethylsilylethynylphenyl)diphosphane sul-
fide 625,15 (50 mg, 0.085 mmol) in toluene (5 ml) and triethylamine
(2 ml) and 240 mg of 8b (0.55 mmol, 6.5equiv.) are added. The
mixture is degassed under argon and CuI (1.6 mg, 12%mol) and
Pd(PPh3)4 (9.8 mg, 10%mol) are added quickly. The reaction
mixture is then stirred for 20h at 50 ◦C under argon. The
volatiles are evaporated in vacuo and the residue is dissolved in
dichloromethane (10mL). The organic layer is washed with HCl
(10%), dried (Na2SO4), filtrated and the solvents are evaporated
under reduced pressure. The crude product is then purified by flash
chromatography (silica gel: CH2Cl2 100% to CH2Cl2/acetone 1:1)
to afford the desired product DPPES2 (2) (51 mg, 33%) as a
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brownish solid. H NMR (CDCl3, 300 MHz): d 7.77 (m, 8H),
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