Octupolar derivatives functionalized with superacceptor peripheral groups: Synthesis and evaluation of the electron-withdrawing ability of potent unusual groups

Article abstract of DOI:10.1002/chem.201103460

Novel tripodal derivatives with a triphenylamine core and that bear "superacidifiers" (i.e., fluorinated sulfoximinyl blocks) or novel sulfiliminyl moieties as peripheral groups were synthesized. These new chromophores show strong absorption in the near-U

Full text of DOI:10.1002/chem.201103460

FULL PAPER
DOI: 10.1002/chem.201103460
Octupolar Derivatives Functionalized with Superacceptor Peripheral Groups:
Synthesis and Evaluation of the Electron-Withdrawing Ability of Potent
Unusual Groups
Cꢀdric Rouxel,[c] Cꢀline Le Droumaguet,[c] Yohan Macꢀ,[b] Sophie Clift,[b]
Olivier Mongin,[c, d] Emmanuel Magnier,*[b] and Mireille Blanchard-Desce*[a, c]
Abstract: Novel tripodal derivatives
with a triphenylamine core and that
bear “superacidifiers” (i.e., fluorinated
provide evidence of a linear correlation
between the Hammett constant (sp)
values and the electronic gap between
the ground and first excited state of
the three-branched derivatives. This in
turn was used to derive sp values of flu-
orinated sulfoximinyl moieties. These
EWGs show unprecedentedly high sp
values, up to 1.45 relative to 0.8 for
NO2. Also, by using this method, the
sulfiliminyl moiety was shown to exhib-
it similar EW strength as NO2, while
promoting improved transparency and
solubility. Finally, the superior EW
strength of the fluorinated sulfoximine
peripheral moieties was shown to
induce significant enhancement of the
two-photon absorption responses in the
red near-IR region of the three-
branched derivatives relative to similar
octupoles that bear more usual strong
EW groups. These characteristics (im-
proved nonlinear responses or trans-
parency) open new routes for the
design of nonlinear optical (NLO)
chromophores for optical limiting or
electro-optical modulation. Such build-
ing blocks could also be of interest for
optoelectronic applications, including
the development of solar cells.
sulfoximinyl blocks) or novel sulfil
ACHTUNGERTNiNUNG m-
ACHTUNGTRENNUNGinyl moieties as peripheral groups were
synthesized. These new chromophores
show strong absorption in the near-UV
region and emission in the visible
region. The fluorinated sulfoximinyl
moieties were found to behave as
potent auxochromic and electron-with-
drawing (EW) groups, thus leading to
redshifted absorption and emission.
These moieties promote a core-to-pe-
riphery intramolecular charge transfer
(ctp-ICT) transition, the energy of
which was found to be correlated to
their EW strength. In this study, we
Keywords: charge transfer · chro-
mophores · fluorinated substituents ·
sulfilimines · sulfoximines
Introduction
The unrivalled properties induced by the presence of fluo-
rine atoms into molecules has allowed considerable progress
in the life sciences (medicinal and agro-chemistry), energy,
as well as materials chemistry.[1] Furthermore, the electron-
withdrawing properties of fluorine-containing moieties as
well the improved transparency brought about by replacing
CH groups by CF groups (as illustrated in polymeric optical
fibers) has attracted considerable attention in the field of
optoelectronics materials. In particular, fluorinated moieties
have been used in several nonlinear optical (NLO) organic
chromophores (NLO-phores) both for second-order effects
(to give push–pull chromophores with large hyperpolariza-
bility b)[2] and third-order effects (including two-photon ab-
sorption).[2a,3] Sulfoxides and, to a greater extent, sulfones
are well known as excellent electron-withdrawing groups
(EWG)[4] and have proven to be of great interest for the
design of push–pull chromophores and NLO-phores while
ensuring suitable transparency, which is of high interest for
applications such as electro-optical modulation[2b,5] or optical
limitation.[6] By taking advantage of the increase in EW abil-
ity induced by the replacement of alkyl substituents by fluo-
rinated ones, we have shown previously that dipolar and oc-
[a] Dr. M. Blanchard-Desce
Univ. Bordeaux, Institut des Sciences Molꢀculaires
CNRS UMR 5255, 351 Cours de la Libꢀration
33405 Talence Cedex (France)
Fax : (+33)5-40-00-66-32
E-mail: m.blanchard-desce@ism.u-bordeaux1.fr
[b] Y. Macꢀ, S. Clift, Dr. E. Magnier
Institut Lavoisier de Versailles (ILV)
CNRS UMR 8180, Universitꢀ de Versailles
St Quentin en Yvelines, 45 avenue des Etats-Unis
78035 Versailles Cedex (France)
Fax : (+33)1-39-25-44-52
E-mail: magnier@chimie.uvsq.fr
[c] Dr. C. Rouxel, Dr. C. Le Droumaguet, Dr. O. Mongin,
Dr. M. Blanchard-Desce
Chimie et Photonique Molꢀculaires
CNRS UMR 6510, Universitꢀ de Rennes 1
Campus de Beaulieu, 35042 Rennes Cedex (France)
[d] Dr. O. Mongin
Institut des Sciences Chimiques de Rennes
CNRS UMR 6226, Universitꢀ de Rennes 1
Campus de Beaulieu, 35042 Rennes Cedex (France)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201103460.
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tupolar derivatives with perfluorinated sulfone moieties as
EWGs exhibit large third-order NLO responses, combined
with redshifted emission and strongly environmental-de-
pendent fluorescence.[3c,d,7] Following this route and with the
aim of further improving the core-to-periphery intramolecu-
lar charge transfer (ctp-ICT) properties, we wish to report
here the synthesis and characterization of three-branched
derivatives that bear “superacidifiers”[8] based on fluorinat-
ed sulfoximines as EW peripheral groups. In addition, we
explore the potentialities of fluorinated sulfilimine moieties
as original EWGs for the elaboration of ctp-ICT derivatives.
The experimental investigation of the auxochromic and fluo-
rochromic characteristics of these nonclassical substituents is
reported. By means of a comprehensive study of their spec-
troscopic (NMR and optical) properties, we describe corre-
lations that allow us to derive the unknown Hammett con-
stant (sp) values of the fluorinated EWGs. The studies
reveal unprecedentedly high sp values for fluorinated sulfox-
iminyl moieties and determine the EW ability of an original
sulfiliminyl moiety, which is shown to be as strong as NO2
but leads to improved transparency.
Figure 1. The three-branched triphenylamine-cored octupolar structure
that contains nitro end groups (model chromophore); sulfoxide (a),
sulfonyl (b), sulfiliminyl (c), and sulfoximinyl (d) EWGs.
Results and Discussion
Design: Three-branched triphenylamine-cored octupolar
chromophores exhibit an intense absorption band in the visi-
ble region, which is related to a ctp-ICT transition. They
also show highly polarity-sensitive emission due to the local-
ization of the excitation on a single branch prior to emis-
sion, thus giving rise to polar emissive excited states.[3d] This
behavior has led to the design of biphotonic fluorescent po-
larity probes.[3c] For biological imaging, it is highly desirable
to shift both absorption (by using two-photon excitation, for
instance) and emission in the visible towards the red region
to reduce toxicity and to allow imaging at increased depth
(in relation to reduced scattering and absorption by endoge-
nous chromophores). We have shown in an earlier study
that an efficient strategy to redshift both absorption and
emission and to enhance both the optical responses (hyper-
chromic shift) and the medium sensitivity consists of in-
creasing the electron-withdrawing strength of the peripheral
groups.[3d] We herein explore the potential of fluorinated su-
peracidifiers as “superacceptors” building blocks. We stress
that the use of such moieties in the molecular NLO domain
remains largely untouched, although potentialities for im-
proving the NLO response(s)/transparency trade-off are
quite attractive.
band of p-conjugated and aromatic systems. This last aspect
is particularly pronounced in so-called push–pull systems
when NO2 is used as a (strong) EWG.[10] However, the ad-
junction of NO2 auxochromic groups often leads to lower
fluorescence quantum yields (due to intersystem crossing in
relation with low-energy n–p* transitions) and also pro-
motes a marked decrease in solubility, particularly when
several nitro substituents are combined in the same molecu-
lar structure. Both of these drawbacks strongly reduce its
scope for the design of fluorescent probes. In that context,
our aim was to develop alternative powerful EWGs while
trying to control nonradiative decay to preserve fluores-
cence and maintain solubility in organic environments. We
have to keep in mind, however, that increased EWG
strength is expected to produce a redshifted absorption and
emission (due to the lowering of the lower electronic excited
state), which accordingly leads to a decrease in the fluores-
cence quantum yield due to combined decrease of the radia-
tive decay rate[11] and an increase in the nonradiative one. In
this context, we explore here the potentialities of fluorinated
sulfoximinyl[8,12] (d) as well as new fluorinated sulfiliminyl[13]
(c) groups in octupolar ctp-ICT compounds (Figure 1).
These EWG moieties will be compared to more classical
strong EWGs such as fluorinated sulfoxides (a) and sulfonyl
(b) moieties.
To ensure photostability and rigidity (to limit nonradiative
decay processes), we have selected phenyleneethynylene
(PE) connectors. An already described three-branched tri-
phenylamine-cored octupolar compound that bears nitro
end groups[9] will be used as
a
model chromophore
Synthesis and structural characterization: The synthesis of
octupolar chromophores 1–8 was achieved by means of
triple Sonogashira coupling between tris[4-(ethynylphenyl)]-
amine core 9[14] and bromo derivatives 10–17 that bear the
electron-withdrawing groups (Scheme 1). Whereas sulfoxide
(Figure 1), since the nitro moiety is the standard prototype
of strong EWGs. The nitro group (NO2) is well known as an
auxochromic substituent that promotes significant redshift
and increases the intensity of the low-energy absorption
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Octupolar Derivatives
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Scheme 1. a) [Pd
N
2ACHTUNGTERN(NUNG dba)3], CuI, PPh3, anhydrous toluene and
Et3N, 40 8C, 5 h (48% of 5, 59% of 6, and 36% of 7); c) [PdAHCTUNGTRENNUNG
10 was commercially available, molecules 11–17 were pre-
pared according to our recent methodology.[13] We have pre-
viously disclosed a straightforward preparation of fluorinat-
ed sulfilimines. The simple treatment of sulfoxides by tri-
fluoromethanesulfonic anhydride and a set of nitriles gave
rise to a wide range of sulfilimines. These sulfur(IV) deriva-
tives were then readily oxidized by potassium permanganate
under basic conditions to produce the corresponding NH-
sulfoximines. This methodology was a great improvement to
the seminal preparation of such compounds described by
Yagupolꢂskii.[15] In the last step, NH-sulfoximines were trans-
formed into derivatives 14 to 17 by treatment of their
sodium salt form with the appropriate electrophile
(Scheme 2).
To the best of our knowledge, the influence of sulfilimine
and sulfoximine groups, introduced as para substituents of
bromobenzene, has never been evaluated through palladi-
um-coupling reactions. We were pleased to validate our
Scheme 2. Reagents and conditions: a) Tf2O, acetonitrile, ꢀ158C; b) KMnO4, NaOH, H2O, RT; c) NaH then Tf2O or FSO2C4F9, CH2Cl2, 408C.
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E. Magnier, M. Blanchard-Desce et al.
strategy by the success of the original Sonogashira coupling
reactions. Compounds 1–4 with sulfoxide or sulfilimine end
groups were indeed obtained by the reaction of core 9 with
bromo derivatives 10–13, respectively, in the presence of
[PdACHTUNGTRENNUNG(PPh3)2Cl2] and CuI in toluene/Et3N. The overall yields
(in pure isolated compound) of these triple Sonogashira
couplings ranged from 41 to 52%, which corresponds to
average theoretical yields of 75 to 80% for a single coupling
reaction (although this description is somewhat misleading
since the reactivity of the intermediary bromides is modified
by the presence of the EWGs). Compounds 5–8, which bear
sulfoximine end groups, were obtained analogously from
core 9 and bromo derivatives 14–17. On account of their
pronounced sensitivity to water and nucleophilic bases, their
synthesis as well as their workup and purification required
strictly anhydrous conditions. In addition, in some cases, it
was also necessary to replace palladium(II) with palladi-
um(0) to reduce side reactions. Chromophores 5 and 6 were
obtained in yields similar to those obtained for 1–4, whereas
7 and 8 were obtained in lower yields (as isolated pure com-
pounds although conversion was found to be quite good)
due to their higher sensitivity to bases. This behavior nicely
illustrates the strong activating effect of the sulfoximine
function when a fluorinated group is attached to the sulfur
atom. This property has been highlighted by recent works
that describe electrophilic perfluoroalkylating reagents
based on the sulfoximine function.[16] In addition, we stress
that the activating effect of the electrophilic character of sul-
fur(IV) by fluorinated substituents is higher for sulfoximine
derivatives (d derivatives in Figure 1) than for sulfones
(b derivatives in Figure 1) since sulfones (such as compound
0) were previously found to be stable in various solvents
and their isolation from the Sonogashira reaction did not
raise particular difficulty when using standard workup and
chromatography conditions.[3c]
Figure 2. A) 1H NMR spectra of compound 2 in CDCl3. B) 1H NMR
spectra of compound 7 in CDCl3.
shifts (Dd) of acetylenic carbons Ca and Cb provides an in-
teresting probe for estimating the relative EW strengths of
the different terminal groups and allows for a relative rank-
ing of the series of EW moieties (including novel ones such
as sulfilimines). As expected, sulfoxides were found to be
the least powerful EW groups among the present series,
whereas fluorinated sulfoximines behave clearly as “super-
acceptors”.[8,15,17] Indeed, the Dd values for fluorinated sul-
foximines (i.e., compounds 5–8; Dd=10.25 ppm) are about
twice as large as those of fluorinated sulfoxides (i.e., com-
pounds 2 and 3) and more than ten times as large as for
TTA. As anticipated from previously reported data,[15] fluo-
rinated sulfoximinyl groups are found to behave as much
stronger EWGs than prototypical NO2 groups (Dd=
6.6 ppm). Hence the 13C NMR spectroscopic study of the
series of octupolar derivatives provides a sensitive way to
monitor the EW strength of terminal groups and can be
used as a tool to scrutinize subtle changes in the strength of
an EWG.[18] For instance, the marked increase in the EW
ability of the sulfoxide moieties by replacement of the hy-
drogen atoms of the alkyl chain with fluorine atoms is moni-
tored by the larger Dd values (5.3 ppm for 2 as compared to
3.1 ppm for 1, as shown in Table 1), as expected from sp
values reported in the literature for SOMe and SOCF3 (0.49
1
Compounds were characterized by H, 13C, 19F NMR spec-
1
troscopy, HRMS, and elemental analysis. H and 13C NMR
spectra (Figure 2 and 3) clearly show the electron-withdraw-
ing (EW) effect of terminal substituents on both proton and
13C chemical shifts. In particular, by comparing the data ob-
tained for the synthetic octupolar derivatives with those of
the tritolylamine (TTA) reference compound (A=H,
Figure 1), we note that the presence of EW peripheral moi-
eties induces deshielding of both Ha’ and Hb’ protons and, to
a lesser extent, of Ha and Hb protons (Table 1). It also gen-
erates a marked deshielding of 13Ca, which increases steadily
following the order 1!8 (Table 1), whereas 13Cb is slightly
shielded (Figure 3). This could be related to an intramolecu-
lar charge transfer in the ground state that generates posi-
tive or negative, respectively, charge density on correspond-
ing carbon atoms. We observe that the influence of the dif-
ferent EW groups on chemical shifts is much more pro-
1
nounced for 13C than for H, which is in agreement with the
increased sensitivity of 13C chemical shifts on charge density
(Table 1) and the lack (or minor contribution) of additional
effects, such as magnetic anisotropy, which also influence
proton chemical shifts. Hence, the difference in chemical
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Octupolar Derivatives
FULL PAPER
and 0.77, respectively) moieties. Lengthening the polyfluori-
nated chain allows for a slight increase in the EW strength
as evidenced by the comparison of sulfoxide (2 and 3) and
sulfoximine (5 and 8) derivatives. In the case of sulfoxi-
mines, this effect depends on the position of the fluorinated
1
chain: the lengthening of RF (Figure 1) allows for a slight
increase in the EW strength of sulfoximinyl moieties
(5 versus 7, and 6 versus 8), whereas this effect is saturated
2
for RF as seen in the comparison between the (5; 6) and (7;
8) pairs (Table 1). However, a consequence of the slightly
higher EW strength provided by C4F9 instead of CF3 is de-
tectable from the activation of the electrophilic reactivity of
sulfur(IV), which particularly results in a high sensitivity of
compounds 7 and 8 toward traces of nucleophiles (including
water). This is a typical illustration of the activation of the
electrophilic character of sulfur by fluorinated substituents.
The NMR spectroscopic study also allowed us to estimate
the EW strength of the novel partially fluorinated sulfilimin-
yl moiety (i.e., SACTHNURGTNEUNG(NAc)CF3). The measured Dd value for
compound 4 (Dd=6.3 ppm) is close to that of the nitro
moiety and lies between the corresponding fluorinated sulf-
oxides (Dd=3.3 ppm for compound 2) and fluorinated sul-
fones (Dd=8.0 ppm for compound 0). It indicates that fluo-
rinated sulfiliminyl moieties hold promise as EWGs for the
design of chromophores for optoelectronic applications. A
further gradual increase in the EW strength should be possi-
ble by lengthening the fluorinated substituent of the sulfil-
ACHUTNGERNiNUG mCAHUTNGTRENNiGUN nyl group and/or replacing the acetyl group by electron-
withdrawing groups such as nitro, cyano, triflyl, or imini-
um.[19]
The NMR spectroscopic study therefore provided a useful
ranking of the potent new fluorinated EWGs with respect to
prototypical ones. We could also establish evidence of a
linear correlation between the Dd values and the reported
sp values for sulfur(II)- and sulfur(IV)-fluorinated EW moi-
eties (Figure 4). Such a linear relationship allows one to
derive the unknown Hammett constant values for fluorinat-
ed sulfoxide SOC4F9 (0.75) and for the novel fluorinated sul-
filiminyl moiety S
(NSO2C4F9)CF3 was found to have a similar Dd value to SO-
(NSO2CF3)CF3, whereas sulfoximines SO(NSO2CF3)C4F9
and SO(NSO2C4F9)C4F9 were found to have slightly larger
sp values (about 1.4). The low dispersion of Dd values in
ACHTUNGTERNN(UNG NAc)CF3 (0.87). Finally, sulfoximine SO-
AHCTUNGTRENNUNG
Figure 3. Inset for acetylenic carbon atoms of 13C NMR spectra of octu-
polar compounds derived from TTA (in CDCl3).
A
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
1
Table 1. Electron-withdrawing effect on H and 13C chemical shifts for octupolar chromophores 0–8 in CDCl3.
Cpd
EWG
sp
d(Ha)
d(Hb)
d
(Haꢂ)
d
G
d=Caacetyl/d=Cbacetyl (Dd)
[ppm]
[ppm]
[ppm]
[ppm]
[ppm]
TTA
1
2
3
H
0.00[33]
0.49[4]
0.77[15]
7.08
7.10
7.12
7.12
7.11
7.125
7.13
7.20
7.16
7.16
7.15
7.44
7.46
7.48
7.49
7.47
7.49
7.50
7.57
7.53
7.53
7.52
7.35
7.65
7.78
7.79
7.85
8.225
8.01
8.15
8.12
8.12
8.12
7.52
7.62
7.73
7.73
7.71
7.65
7.76
7.89
7.85
7.85
7.85
89.3/89.2 (0.1)
91.3/88.2 (3.1)
93.1/87.8 (5.3)
93.3/87.9 (5.4)
93.9/87.6 (6.3)
94.4/87.8 (6.6)
95.5/87.5 (8.0)
97.5/87.3 (10.2)
97.5/87.3 (10.2)
97.7/87.4 (10.3)
97.7/87.4 (10.3)
SOMe
SOCF3
SOC4F9
[a]
–
–
[a]
4
S
G
model
0.81[33]
1.04[15]
1.39[15]
0
5
6
7
8
SO2CF3
SO
ACHTUNGTRENNUNG
[a]
SO
SO
U
–
–
–
[a]
[a]
SO
(NSO2C4F9)C4F9
[a] Unknown.
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E. Magnier, M. Blanchard-Desce et al.
Figure 4. Linear correlation between Hammett constants (sp) from the
literature for fluorinated sulfur(II) and sulfur(IV) moieties and difference
in chemical shifts (Dd) of acetylenic carbons in octupolar derivatives.
this series indicates that NMR spectroscopic methodology is
not sensitive enough to distinguish the EW strength of the
various fluorinated sulfoximine groups. Complementary
spectroscopic studies are thus required to yield more precise
accurate sp values in that particular case (vide infra).
Absorption and fluorescence properties: All octupolar com-
pounds show an intense absorption band in the near-UV-
blue-visible region and emission in the visible region
(Figure 5). Sulfoxides and sulfilimine derivatives (1–4) are
violet-blue emitters, whereas sulfoximines (5–8) are green
emitters. Absorption and fluorescence characteristics are
collected in Table 2. We observed a marked bathochromic
and hyperchromic shift of the low-energy absorption band
as well as a significant redshifted emission upon going from
fluorinated sulfones to corresponding fluorinated sulfoxi-
mine derivatives. A bathochromic and hyperchromic shift of
the low-energy absorption band as well as a marked redshift
of the emission is observed upon going from a fluorinated
sulfone derivative (0) to the corresponding fluorinated sul-
foximine derivatives 5 and 6 in relation to the increased EW
strength of peripheral groups (X,Y=O,O !X,Y=
Figure 5. Normalized absorption and emission spectra of octupolar chro-
mophores 1–4 (top) and 5–8 (bottom)
to sulfoxide derivative 2 (X=O!NAc), which is in agree-
ment with the stronger EW character of the peripheral
groups. In this case, however, no marked change of the ab-
sorption was observed, whereas a slight redshift of the emis-
sion as well as a decrease in the fluorescence quantum yield
was observed. Hence, although being comparable to NO2 in
terms of EW strength, the SACHTNUTRGENNG(U NAc)CF3 sulfiliminyl group
leads to improved transparency. Indeed, compound 4 was
found to be 20 nm more transparent than its NO2 analogue
(Table 2). This improved EWG character combined with the
enlarged transparency in the visible range could be of inter-
est for NLO applications,[2k] including optical limiting.[6]
Lengthening the fluorinated moiety also produces a bath-
ochromic shift of the emission, the effect being stronger in
2
O,NSO2RF ). A significant increase in the Stokes shift is also
noted in relation to the stronger EWG character. The same
phenomenon is observed for sulfilimine derivative 4 relative
Table 2. Photophysical data for octupolar chromophores 0–8 in toluene.
[a]
[d]
[g]
Cpd
EWG
labs
10ꢀ4 emax[b]
[cmꢀ1 mꢀ1
FWHM[c]
[cmꢀ1
lem
F[e]
Stokes shift[f]
[cmꢀ1
E0–0
[nm]
G
]
E
]
[nm]
G
]
[eV]
TTA
H
369
382
389
393.5
390
405
419
422
425.5
428.5
7.8
9.0
8.7
8.8
7.2
6.0
8.0
8.1
5.1
6.7
3500
3500
3700
3600
3800
3700
3700
3800
3800
3700
402
414
431
435
440
450
500
496
515
516
0.76
0.63
0.73
0.71
0.52
0.78
0.65
0.58
–
2220
2020
2510
2420
2910
2470
3870
3540
4070
3960
3.22
3.12
3.03
3.00
3.00
2.91
2.72
2.72
2.66
2.65
1
2
3
4
0
5
6
7
8
SOMe
SOCF3
SOC4F9
SACHTUNGTRENNUNG
SO
SO(NSO2C4F9)CF3
SO(NSO2CF3)C4F9
SO(NSO2C4F9)C4F9
(NSO2CF3)CF3
E
E
N
–
[a] Experimental one-photon absorption maximum. [b] Experimental molar extinction coefficient. [c] Half bandwidth. [d] Experimental one-photon
emission maximum. [e] Fluorescence quantum yield determined relative to fluorescein in 0.1n NaOH. [f] Stokes shift=(1/labsꢀ1/lem). [g] Electronic gap
(0–0 transition energy).
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Octupolar Derivatives
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the case of sulfoximine derivatives for the fluorinated
groups directly attached to the sulfur(IV) atom. We observe
that fluorinated derivatives (sulfoxides 2 and 3, sulfone 0,
and sulfoximines 5 and 6) are good fluorescence emitters
(F=0.6–0.8),[20] as is the case of the unsubstituted derivative
(TTA), but their emission is significantly redshifted (from
violet to blue-green). This offers clear evidence of the influ-
ence of strong peripheral EWGs in promoting core-to-
periphery intramolecular charge-transfer transitions.
mett constants are related to ground-state properties and
have been used to predict the effect of electroactive (EW or
electron-releasing) substituents on chemical-reaction kinet-
ics. The basis of this concept is a linear relationship between
thermodynamic (typically acidity of benzoic acid) and kinet-
ic data (reaction activation energy), thus leading to so-called
linear free-energy relationships (LFER).[24] We can there-
fore assume a similar relationship between thermodynamic
data and UV-visible excitation energy since electron-density
shifts are involved both in covalent bond breaking and for-
mation (reaction kinetics) and in the formation of an elec-
tronically excited state. We posit that such a correlation will
be particularly relevant for intramolecular charge-transfer
types of transition in which the role of electron-donating
and electron-releasing substituents is crucial. To test this hy-
pothesis, we investigated the variation of the electronic gap
(Table 2) as a function of the already known sp constants for
sulfonyl EWGs. We stress that it is important in doing so to
derive a valid value of the electronic gap between the
ground and excited state. Since the UV-visible absorption
bands of the octupolar derivatives investigated in the pres-
ent work are broad (due precisely to their ICT character),
the exact location of the 0–0 vibronic band is not straightfor-
ward. Hence, it is important to use both absorption and
emission (related to the ICT transition) characteristics to
derive the electronic gap from the two mirror bands (ab-
sorption and emission). We have done so by using the data
reported in the literature for octupolar derivatives that bear
sulfone peripheral groups and have double-bond linkers[3d]
instead of triple bond. As evidenced in Figure 7, a linear
As expected for ctp-ICT compounds, the fluorescence
properties of octupolar derivatives 1–8 showed a marked de-
pendency on solvent polarity (Figure 6).[21] A marked red-
Figure 6. Solvatochromic behavior of octupolar compounds 3 (top) and 4
(bottom).
shift of the emission band was observed with increasing sol-
vent polarity, whereas no such effect was observed for ab-
sorption. Such behavior, not observed with the unsubstituted
TTA compound, provides clear evidence that highly polar-
ized emissive excited states are produced—in agreement
with excitation localization on dipolar branches after excita-
tion prior to emission[22]—thanks to the presence of strong
peripheral EWGs.
Figure 7. Linear correlations between Hammett constants (sp) of terminal
moieties and electronic gaps of octupolar derivatives built from a triphe-
nylamine core. The + symbols represent experimental data using known
sp values, whereas diamonds represent the sp values derived from the
electronic gap of fluorinated sulfoximide octupoles.
correlation is indeed obtained, similar to linear free-energy
relationships,[24] whereby the reaction activation energy is re-
placed here by the ICT transition energy. Furthermore, by
using the sp values reported in the literature for the sulfone
moieties and derived from the NMR spectroscopic study for
the novel sulfilimine EWG (see above), a similar linear rela-
tionship is obtained for octupolar derivatives that have
triple-bond linkers and bear sulfone[3c] or sulfilimine moiet-
ies (Figure 7). Interestingly the same slope (equivalent to
Correlations and determination of Hammett constants: Due
to the ctp-ICT character of the p–p* transition of octupolar
derivatives 1–8, we might expect the corresponding electron-
ic gap (i.e., the difference in energy between relaxed ground
and excited states) to be correlated to the EW ability of the
peripheral groups. This assumption is secured by a series of
previous works that depict the linear relationship between
photophysical data and Hammett constants.[23] Indeed, Ham-
Chem. Eur. J. 2012, 00, 0 – 0
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E. Magnier, M. Blanchard-Desce et al.
the Taft parameter 1 for reaction kinetics) is obtained for
octupolar derivatives that have a double-bond and triple-
bond connector between the triphenylamine electron-releas-
ing core and the phenyl units that bear electron-withdrawing
peripheral substituents. This too emphasizes the analogy
with LFER whereby the Taft parameter is a characteristic of
the type of reaction and gives information about the nature
of the transition state.[24] In our case, the slope value gives
information of the nature of the transition and clearly points
to an ICT type of electronic transition. Hence, the ICT elec-
tronic gap—as long as it can be accurately determined as
the E00 energy from combined absorption and emission
data—represents an interesting tool for deriving sp values.
As such, it provides an additional spectroscopic tool that is
complementary to NMR spectroscopy, which has been used
as a method for deriving Hammett values, thanks to the
marked sensitivity of the chemical shifts of big nuclei (as
cross-sections could be measured by performing two-
photon-induced fluorescence experiments in solution.[25] On
the basis of an earlier theoretical study carried out by Cho
and co-workers,[26] which did show some correlation between
the maximum TPA cross-sections and Hammett constants of
electron-donating substituents of octupolar derivatives built
from a central electron-acceptor carbocation (typically in-
spired by prototypical crystal violet), our motivation was to
investigate if such dependency is general and valid for oppo-
site-type octupoles (i.e., those built from a central electron-
donor atom, such as triphenylamine derivatives).
The TPA spectra of the selected octupolar derivatives are
shown in Figure 8, whereas the maxima characteristics (posi-
tion and maximum cross-sections) are collected in Table 3.
We observed that the TPA spectra show typical characteris-
1
compared to H) toward electronic density.[8]
Whereas 13C NMR spectroscopy allows for a very precise
discrimination between various sulfur(II) and sulfur(IV) de-
rivatives (Table 1 and Figure 6), it does not allow for an
acute distinction between the EW strength of the different
fluorinated sulfoximine moieties (see the data for series of
compounds 5–8 in Table 1). In this case, however, the de-
pendency of the electronic gap on the EW strength is such
that it allows us to distinguish between these moieties
(Table 2) and to derive refined precise sp values for the dif-
ferent fluorinated sulfoximine moieties by using the linear
correlation between EW strength and the electronic gap
(Figure 7). Indeed, refined sp values larger than 1.4 are de-
rived from the ICT electronic gap for “superacceptor”
^
Figure 8. Two-photon absorption spectra of fluorinated sulfylimine 4 (
)
~
and sulfoximine 5 ( ) compared with that of related sulfonyl compound
*
0 ( ).
A
7
(SO-
A
ACHTUNGTRENNUNG
tics of octupolar derivatives: a low-energy TPA band that
corresponds to the lower (one-photon-allowed) excited
state, which is also slightly two-photon-allowed, plus an ad-
ditional stronger TPA band that peaks at higher energy and
corresponds to a strongly two-photon-allowed, one-photon-
forbidden excited state.[25b] The enhancement of this latter
band as well as energy splitting between the two states
strongly depend on the coupling between the dipolar bran-
ches.[7b,22a]
As seen in Figure 8, a major increase in the TPA bands
was observed for octupole 5, which bears fluorinated sulfox-
iminyl peripheral groups (sp =1.35), over octupole 0, which
bears fluorinated sulfonyl (SO2CF3; sp =1.04) terminal moi-
eties. As seen in Table 3, this leads to a maximum TPA re-
sponse that is almost twice as large as that of compound 0,
G
ACHTUNGTRENNUNG
refined sp values of 1.35. This indicates that the fluorinated
substituents directly linked to the sulfur(IV) atom connected
to the conjugated spacer has more influence on the optical
properties of the octupolar derivatives. This suggests that
further increasing the EW strength of this substituent could
be of interest. This also suggests that sulfur(II) moieties
(such as novel sulfilimines) could likely also be further engi-
neered to become stronger EW groups by lengthening the
fluorinated chain directly connected to the sulfur(II) atom.
Two-photon absorption: To assess the interest in the new
EWGs (fluorinated sulfoximine and sulfilimine) for the
design of NLO chromophores, we investigated the two-
photon absorption (TPA) re-
sponse in the red near-IR
Table 3. Two-photon absorption data for selected octupolar chromophores built from a triphenylamine core
and that bear novel (fluorinated sulfilimine (SII) or sulfoximide (SIV)) electron-withdrawing peripheral groups.
(NIR) region of octupolar de-
rivatives 5 and 4 and compared
their TPA response to that of
the related fluorinated sulfonyl
derivative 0 that bears a typi-
cally potent EWG. Thanks to
their fluorescence, their TPA
max1
TPA
max2
TPA
Cpd
EWG
sp
l
sm2 ax1
l
sm2 ax2
[nm]
[GM]
[nm]
[GM]
0
4
5
SO2CF3
1.04[15]
0.87[a]
1.35[a]
815
810
830
370
220
540
730
740
740
500
290
870
SACHTUNGTRENNUG
SOACHTUGNTRENNNUG
[a] This work.
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Octupolar Derivatives
FULL PAPER
although compound 5 is redshifted by only 15 nm. This sug-
gests that such compounds could be of interest for the
design of optical limiters for the protection of NIR sensors.
This is also more than twice as large as that of the related
octupole that bears dimesitylboryl peripheral moieties
(375 GM at 720 nm).[27] Conversely, the novel partially fluo-
rinated electron-withdrawing group SNAcCF3, which has a
lower sp value than fluorinated sulfonyl moiety SO2CF3
(i.e., 0.87 instead of 1.04) and improved transparency by
about 15 nm, leads to a maximum TPA cross-section that is
about twice as small as octupole 0. In that series of related
compounds (i.e., octupoles with the same core and conjugat-
ed path but different EWGs), the NLO responses are thus
directly correlated to the EW strength, which shows that a
linear correlation between the strength of peripheral groups
can also be demonstrated for octupoles built from an elec-
tron-donating core (Figure 9).[28] Such behavior can be inter-
preted within the framework of essential-state models.[26,29]
relative to fluorinated sulfonyl moieties, which are known to
be among the strongest neutral EWGs for NLO). Due to
their unprecedented electron-withdrawing ability, these
“superacceptor” moieties lead to enhanced TPA response of
octupolar derivatives and should also be of interest for
second-order NLO applications (such as electro-optical
modulation) as well as for different optoelectronic applica-
tions, including solar cells.[30] Finally, we have also deter-
mined the EW ability of an original, partially fluorinated,
sulfiliminyl moiety, SACHTUNTRGNEUNG(NAc)CF3, which was found to be close
to that of the nitro moiety while providing improved trans-
parency and solubility. This represents a promising NLO-
chromic building block for an improved tradeoff between
transparency, solubility, and NLO responses. In addition,
subtle tuning of the EW ability could possibly be achieved
by playing with the replacement of hydrogen atoms with flu-
orine atoms or by replacement of the acetyl moiety with
some other EW moiety. This opens a new route for the
design of novel fluorinated sulfiliminyl moieties with adjust-
able NLO/fluorescence properties. Further investigation
along this direction is currently in progress.
Experimental Section
Synthetic procedures: Synthetic procedures and characterization data for
all octupolar chromophores are given below, and those for intermediate
compounds can be found in the Supporting Information.
Tris{4-[(4-nitrophenyl)ethynyl]phenyl}amine: Air was removed from a
solution of 9 (200 mg, 0.631 mmol) and 1-iodo-4-nitrobenzene (534 mg,
2.145 mmol, 3.4 equiv) in toluene/Et3N (4:1; 9 mL) by blowing argon for
20 min. Then CuI (7.1 mg, 0.037 mmol) and [PdACHTNUGTRNEG(UN PPh3)2Cl2] (26 mg,
Figure 9. Linear correlation between Hammett constants (sp) and maxi-
mum two-photon absorption cross-section (sm2 ax) of octupolar derivatives.
0.037 mmol) were added, and the mixture was stirred at 408C for 16 h.
After evaporation of the solvents, the residue was purified by column
chromatography (CH2Cl2/AcOEt 95:5) to yield the title compound
(218 mg, 51%).[9] 1H NMR (200 MHz, CDCl3): d=8.24 (d, J=8.8 Hz,
6H), 7.66 (d, J=8.6 Hz, 6H), 7.50 (d, J=8.6 Hz, 6H), 7.13 ppm (d, J=
8.8 Hz, 6H); 13C NMR (100.62 MHz, CDCl3): d=147.2, 146.9, 133.3,
132.0, 130.2, 124.1, 123.5, 117.1, 94.4, 87.8 ppm.
Given the improved transparency and solubility that the
SNAcCF3 group provides over NO2, using such moieties as
EW end groups in suitable quadrupolar derivatives could be
of interest for the design of NLO-phores for optical limita-
Tris(4-{[4-(methylsulfinyl)phenyl]ethynyl}phenyl)amine (1): Air was re-
moved from a solution of 9 (75 mg, 0.2363 mmol) and 10 (181 mg,
0.8271 mmol, 3.5 equiv) in toluene/Et3N (4:1; 5 mL) by blowing argon for
tion in the visible region.[6] Hence, sulfoximinyl and sulfil
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
20 min. Then CuI (2.7 mg, 0.0142 mmol) and [PdACHTUNGTRNEG(UN PPh3)2Cl2] (10 mg,
mentary (in terms of transparency/NLO-response tradeoff)
EW building blocks for the design of NLO-phores.
0.0142 mmol) were added, and the mixture was stirred at 408C for 16 h.
After evaporation of the solvents, the residue was purified by column
1
chromatography (CH2Cl2/AcOEt 98:2) to yield 1 (74 mg, 43%). H NMR
(300.13 MHz, CDCl3): d=7.65 and 7.62 (AA’BB’, J
7.46 and 7.10 (AA’XX’,
ACHTUNGTRENNUNG
JACHTUNGTRENNUNG
13C NMR (75.47 MHz, CDCl3): d=146.8, 145.1, 132.9, 132.2, 126.3, 124.0,
123.5, 117.6, 91.3, 88.2, 43.8 ppm; HRMS (ES+): m/z: calcd for
C45H33NO3NaS3 [M+Na]+: 754.15148; found: 754.1514.
Conclusion
On the basis of comprehensive spectroscopic studies (com-
bined NMR, absorption, and fluorescence), we have been
able to determine exact sp values for closely related fluori-
nated sulfoximinyl moieties. These building blocks show un-
precedented EW ability, as demonstrated by their unique sp
values (up to 1.45 relative to 0.8 for NO2 and 1.0 for
SO2CF3). These moieties can thus be used not only as “su-
peracidifiers” but also as “superacceptor” groups. This sig-
nificant enhancement of EW strength leads to major TPA
enhancement in octupolar derivatives (by a factor of two
Tris[4-({4-[(trifluoromethyl)sulfinyl]phenyl}ethynyl)phenyl]amine
Air was removed from a solution of 9 (341 mg, 1.077 mmol) and 11 (1 g,
3.662 mmol, 3.4 equiv) in toluene/Et3N (4:1; 16 mL) by blowing argon for
20 min. Then CuI (12 mg, 0.0646 mmol) and [PdACHTNUGTRNEG(UN PPh3)2Cl2] (45 mg,
0.0646 mmol) were added, and the mixture was stirred at 408C for 16 h.
After evaporation of the solvents, the residue was purified by column
(2):
chromatography (heptane/CH2Cl2 50:50) to yield
2
(463 mg, 48%).
(A,X)=
JACHTUNGRTEN(NUNG A,X)=8.7 Hz, 12H);
1H NMR (300.13 MHz, CDCl3): d=7.78 and 7.73 (AA’BB’, J
ACHTUNGTRENNUNG
8.6 Hz, 12H), 7.48 and 7.12 ppm (AA’XX’,
13C NMR (75.47 MHz, CDCl3): d=147.1, 134.7, 133.1, 132.4, 129.1, 125.9,
124.6 (q, J=335.4 Hz), 124.1, 117.2, 93.1, 87.8 ppm; 19F NMR
Chem. Eur. J. 2012, 00, 0 – 0
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E. Magnier, M. Blanchard-Desce et al.
(282.37 MHz, CDCl3): d=ꢀ74.3 ppm (s, 9F; CF3); HRMS (ES+): m/z:
0.015 mmol) were added. The reaction mixture was heated at 408C for
5 h. After removing solvents, the residue was purified by column chroma-
tography (heptane/CH2Cl2, gradient from 60:40 to 30:70) to yield 7
(161 mg, 36%). 1H NMR (300.13 MHz, CDCl3): d=8.11 and 7.85
calcd for C45H24NO3F9S3 [M]+ : 893.07746; found: 893.0769.
C
Tris[4-({4-[(nonafluorobutyl)sulfinyl]phenyl}ethynyl)phenyl]amine
(3):
Air was removed from a solution of 9 (200 mg, 0.63 mmol) and 12
(900 mg, 2.132 mmol, 3.4 equiv) in toluene/Et3N (4:1; 9 mL) by blowing
argon for 20 min. Then CuI (7.1 mg, 0.0373 mmol) and [PdACHTUNGTRNEG(UN PPh3)2Cl2]
(26 mg, 0.037 mmol) were added, and the mixture was stirred at 408C for
(AA’XX’, JACTHUNRTGENNUG(A,X)=8.7 Hz, 12H), 7.52 and 7.16 ppm (AA’XX’, JACHTUNGTRENNUNG(A,X)=
8.7 Hz, 12H); 13C NMR (75.47 MHz, CDCl3): d=147.5, 134.3, 133.6,
133.0, 131.1, 128.2, 124.3, 118.8 (q, J=320.5 Hz), 116.6, 97.7, 87.4 ppm;
19F NMR (282.37 MHz, CDCl3): d=ꢀ125.7 (m, 6F; CF2), ꢀ119.4 (m, 6F;
CF2), ꢀ110.0 (d, J=248.3 Hz, 3F; AB system, SCFAFB), ꢀ105.3 (d, 3F;
AB system, SCFAFB), ꢀ80.5 (t, J=9.6 Hz, 9F; CF3), ꢀ78.7 ppm (s, 9F;
SO2CF3).
16 h. After evaporation of the solvents, the residue was purified by
column chromatography (pentane/CH2Cl2 50:50) to yield
47%). 1H NMR (200.13 MHz, CDCl3): d=7.79 and 7.73 (AA’BB’, J-
(A,X)=8.7 Hz, 12H), 7.49 and 7.12 ppm (AA’XX’, (A,X)=8.6 Hz,
3 (463 mg,
A
JACHTUNGTRENNUNG
12H); 13C NMR (75.47 MHz, CDCl3): d=147.1, 133.9, 133.2, 132.3, 129.4,
126.7, 124.1, 117.2, 93.3, 87.9 ppm; 19F NMR (188 MHz, CDCl3): d=
ꢀ126.6 (m, 6F; CF2), ꢀ122.9 (d, J=245.3 Hz, 3F; AB system, SCFAFB),
ꢀ121.6 (m, 6F; CF2), ꢀ111.7 (d, 3F; AB system, SCFAFB), ꢀ81.3 ppm
(m, 9F; CF3); HRMS (ES+): m/z: calcd for C54H24NO3F27NaS3 [M+Na]+:
1366.03794; found: 1366.0377.
Tris{4-[(4-{S-(nonafluorobutyl)-N-[(nonafluorobutyl)sulfonyl]sulfonimi-
doyl}phenyl)ethynyl]phenyl}amine (8). Air was removed from a solution
of 9 (49 mg, 0.152 mmol) and 17 (366 mg, 0.0.508 mmol, 3.3 equiv) in tol-
uene/Et3N (10:1; 3.3 mL) by blowing argon for 20 min. Then CuI (1.8 mg,
0.0092 mmol) and [PdACHTUNGTRNEG(UN PPh3)2Cl2] (6.5 mg, 0.0092 mmol) were added, and
the mixture was stirred at 408C for 15 h. After evaporation of the sol-
vents, the residue was purified by column chromatography (heptane/
CH2Cl2 50:50) to yield 8 (89 mg, 26%). 1H NMR: d=8.12 and 7.85
Tris[4-({4-[S-(trifluoromethyl)-N-(acyl)sulfinimidoyl]phenyl}ethynyl)phe-
nyl]amine (4): Air was removed from
a solution of 9 (280 mg,
(AA’XX’, JACTHUNRTGENNUG(A,X)=8.7 Hz, 12H), 7.52 and 7.15 ppm (AA’XX’, JACHTUNGTRENNUNG(A,X)=
0.867 mmol) and 13 (953 mg, 3.034 mmol, 3.4 equiv) in toluene/Et3N (4:1;
13 mL) by blowing argon for 20 min. Then CuI (10 mg, 0.052 mmol) and
8.7 Hz, 12H); 13C NMR (75.47 MHz, CDCl3): d=147.5, 134.2, 133.6,
133.0, 131.1, 128.3, 124.3, 116.7, 97.7, 87.4 ppm; 19F NMR (282.37 MHz,
CDCl3): d=ꢀ126.0 (m, 4F; CF2), ꢀ121.0 (m, 2F; CF2), ꢀ119.4 (m, 2F;
CF2), ꢀ111.9 (dt, J=76.1, 13.6 Hz, 2F; CF2), ꢀ109.7 (d, J=243.5 Hz, 1F;
AB system, SCFAFB), ꢀ105.2 (d, 1F; AB system, SCFAFB), ꢀ80.7 (t, J=
9.8 Hz, 3F; CF3), ꢀ80.5 (t, J=9.7 Hz, 3F, CF3); HRMS (ES+): m/z: calcd
for C66H24N4O9F54NaS6 [M+Na]+: 2256.89975; found: 2256.8997.
[Pd
red at 408C for 16 h. After evaporation of the solvents, the residue was
purified by column chromatography (CH2Cl2/EtOH 97:3) to yield
(459 mg, 52%). 1H NMR (300.13 MHz, CDCl3): d=7.85 and 7.71
(AA’XX’, (A,X)=8.5 Hz, 12H), 7.48 and 7.11 (AA’XX’, (A,X)=
ACHTUNGTRENNUNG(PPh3)2Cl2] (37 mg, 0.052 mmol) were added, and the mixture was stir-
4
J
N
JACHTUNGTRENNUNG
8.7 Hz, 12H), 2.24 ppm (s, 9H); 13C NMR (75.47 MHz, CDCl3): d=183.9,
147.1, 133.2, 132.8, 130.0, 128.6, 125.9, 124.1, 124.1 (q, J=323.9 Hz), 93.9,
87.6, 23.9 ppm; 19F NMR (282.37 MHz, CDCl3): d=ꢀ64.0 ppm (s, 9F,
CF3); HRMS (ES+): m/z: calcd for C51H34N4O3F9S3 [M+H]+:
1017.16494; found: 1017.1643.
Photophysical methods: All photophysical properties measurements have
been performed with freshly prepared air-equilibrated solutions at room
temperature (298 K). UV/Vis absorption spectra were recorded using a
Jasco V-570 spectrophotometer. Steady-state and time-resolved fluores-
cence measurements were performed on dilute solutions (ꢁ10ꢀ6 m, opti-
cal density<0.1) contained in standard 1 cm quartz cuvettes using an Ed-
inburgh Instruments (FLS920) spectrometer in photon-counting mode.
Fully corrected emission spectra were obtained for each compound at
lex =lmabasx with an optical density at lex ꢂ0.1 to minimize internal absorp-
tion. Fluorescence quantum yields were measured according to literature
procedures.[31]
Tris{4-[(4-{S-(trifluoromethyl)-N-[(trifluoromethyl)sulfonyl]sulfonimi-
doyl}phenyl)ethynyl]phenyl}amine (5): Air was removed from a solution
of 9 (49.6 mg, 0.156 mmol) and 14 (230 mg, 0.547 mmol) in anhydrous tol-
uene/dry Et3N (5:1; 3.5 mL). Then PPh3 (2.5 mg, 9.38 mmol), CuI (1.8 mg,
9.38 mmol), and [Pd2ACHTUNGTRENNUNG(dba)3] (dba=dibenzylideneacetone; 8.6 mg,
9.38 mmol) were added. The reaction mixture was heated at 408C for 5 h.
After removing solvents, the residue was purified by column chromatog-
raphy (heptane/CH2Cl2, gradient from 60:40 to 30:70) to yield 5 (101 mg,
Two-photon absorption (TPA) measurements were conducted by investi-
gating the two-photon-induced fluorescence in solution. Two-photon-ex-
cited fluorescence spectroscopy was performed using a mode-locked
Ti:sapphire laser that generated 150 fs-wide pulses at a 76 MHz repeti-
tion rate, with a time-averaged power of several hundreds of mW (Co-
herent Mira 900 pumped using a 5 W Verdi). The fluorescence from the
sample was collected in epifluorescence mode. The emission and the re-
sidual excitation light were removed using a barrier filter. The emission
spectra were corrected for the wavelength dependence of the detection
efficiency using correction factors established through the measurement
of reference compounds with known fluorescence emission spectra. The
emission intensities at each excitation wavelength were shown to depend
quadratically on the excitation power. The two-photon emission spectra
were found to correspond to those obtained with standard one-photon
excitation. Absolute values for the two-photon excitation action cross-
sections s2F were obtained according to the method described by Xu
and Webb.[25a] For the 700–980 nm excitation window, 10ꢀ4 m fluorescein
in aqueous 0.01m NaOH was used as a reference, and corrections for the
refractive index of the solvent were applied.[32]
1
48%). M.p. 117–1188C; H NMR (300.13 MHz, CDCl3): d=8.15 and 7.89
(AA’XX’, JACHTUNGTRENNUNG(A,X)=8.5 Hz, 12H), 7.57 and 7.20 ppm (AA’XX’, JACHTUNGTRNE(NUGN A,X)=
8.5 Hz, 12H); 13C NMR (75.47 MHz, CDCl3): d=147.5, 134.1, 133.6,
133.1, 130.6, 126.8, 124.3, 119.9 (q, J=328.8 Hz), 118.9 (q, J=321.5 Hz),
116.7, 97.5, 87.3 ppm; 19F NMR (282.37 MHz, CDCl3): d=ꢀ78,4 (s, 9F;
CF3), ꢀ75.2 ppm (s, 9F; CF3); HRMS (LSIMS+, mNBA): m/z: calcd for
C48H24N4O9F18S6 [M]+ : 1333.95802; found: 1333.9578.
C
Tris{4-[(4-{S-(trifluoromethyl)-N-[(nonafluorobutyl)sulfonyl]sulfonimi-
doyl}phenyl)ethynyl]phenyl}amine (6). Air was removed from a solution
of 9 (79 mg, 0.2506 mmol) and 15 (500 mg, 0.8769 mmol, 3.5 equiv) in tol-
uene/Et3N (6:1; 5.8 mL) by blowing argon for 20 min. Then PPh3 (4.0 mg,
0.015 mmol), CuI (3.0 mg, 0.015 mmol), and [Pd2ACHTNUTRGNE(UNG dba)3] (14.0 mg,
0.015 mmol) were added. The reaction mixture was heated at 408C for
5 h. After removal of the solvents, the residue was purified by column
chromatography (heptane/CH2Cl2, gradient from 60:40 to 30:70) to yield
6
(263 mg, 59%). 1H NMR (300.13 MHz, CDCl3): d=8.12 and 7.85
(AA’XX’, JACHTUNGTRENNUNG(A,X)=8.8 Hz, 12H), 7.53 and 7.16 ppm (AA’XX’, JACHTUNGTRNE(NUGN A,X)=
8.8 Hz, 12H); 13C NMR (75.47 MHz, CDCl3): d=147.5, 134.1, 133.6,
133.1, 130.6, 128.2, 124.3, 119.9 (q, J=328.0 Hz), 118.9 (q, J=321.5 Hz),
116.6, 97.5, 87.3 ppm; 19F NMR (282.37 MHz, CDCl3): d=ꢀ126.0 (m, 6F;
CF2), ꢀ121.6 (m, 6F; CF2), ꢀ111.9 (m, 6F; CF2), ꢀ80.7 (m, 9F; CF3),
ꢀ75.4 ppm (s, 9F; CF3); HRMS (ES+): m/z: calcd for C57H24N4O9F36S6
Acknowledgements
[M]+ : 1783.92928; found: 1783.9299; m/z: calcd for C57H24N4O9F36NaS6
C
[M+Na]+: 1806.91905; found: 1806.91926.
We thank Rꢀgion Bretagne for a fellowship to C.L.D. The financial sup-
port of the Centre National de la Recherche Scientifique (CNRS) is ac-
knowledged. We are grateful to Vincent Hugues for his assistance in
TPA measurements. Y.M. thanks GlaxoSmithKline and CNRS for finan-
cial support (BDI grant), and S.C. thanks the Erasmus Program.
Tris{4-[(4-{S-(nonafluorobutyl)-N-[(trifluoromethyl)sulfonyl]sulfonimi-
doyl}phenyl)ethynyl]phenyl}amine (7): Air was removed from a solution
of 9 (79 mg, 0.2506 mmol) and 16 (500 mg, 0.8769 mmol, 3.5 equiv) in tol-
uene/Et3N (6:1; 5.8 mL) by blowing argon for 20 min. Then PPh3 (4.0 mg,
0.015 mmol), CuI (3.0 mg, 0.015 mmol), and [Pd2ACHTNUTRGNE(UNG dba)3] (14.0 mg,
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Octupolar Derivatives
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Received: November 3, 2011
Revised: June 25, 2012
Published online: && &&, 0000
Chem. Eur. J. 2012, 00, 0 – 0
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E. Magnier, M. Blanchard-Desce et al.
Electron-Withdrawing Groups
C. Rouxel, C. Le Droumaguet,
Y. Macꢀ, S. Clift, O. Mongin,
E. Magnier,*
M. Blanchard-Desce* . . . . . . . &&&& — &&&&
Octupolar Derivatives Functionalized
with Superacceptor Peripheral
Groups: Synthesis and Evaluation of
the Electron-Withdrawing Ability of
Potent Unusual Groups
Superacceptors: A series of tripodal
derivatives with a triphenylamine core
and superacceptor-fluorinated periph-
eral groups was synthesized (see
figure). A linear correlation between
the Hammett constant (sp) and the
electronic gap E0–0 was established; sp
values up to 1.45 were derived. Such
electron-withdrawing strength was
shown to enhance the two-photon
absorption responses.
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These are not the final page numbers!