Supramolecular ruthenium-alkynyl multicomponent architectures: Engineering, photophysical properties, and responsiveness to nitroaromatics

Article abstract of DOI:10.1021/om400811z

A series of H-bonded supramolecular architectures were built from monofunctional M-Ci - C-R and bifunctional R-Ci - C-M-Ci - C-R trans-alkynylbis(1,2-bis(diphenylphosphino)ethane)ruthenium(II) complexes and π-conjugated modules containing 2,5-dialkoxy-p-p

Full text of DOI:10.1021/om400811z

Article
pubs.acs.org/Organometallics
Supramolecular Ruthenium−Alkynyl Multicomponent Architectures:
Engineering, Photophysical Properties, and Responsiveness to
Nitroaromatics
Rafik Gatri,†,‡ Ines Ouerfelli,†,‡ Mohamed Lofti Efrit,† Francoise Serein-Spirau,§ Jean-Pierre Lere-Porte,§
̧
̀
Pierre Valvin,∥ Thierry Roisnel,‡ Sebastien Bivaud,‡ Huriye Akdas-Kilig,‡ and Jean-Luc Fillaut*,‡
́
†Laboratoire de Synthes
Universitaire, Universite
̀
e Organique et Het
́
er
́
ocyclique, Dep
́
artement de Chimie, Faculte
́
des Sciences de Tunis, Campus
́
Tunis El Manar 2, 2092 Tunis, Tunisia
‡Institut des Sciences chimiques de Rennes, UMR 6226 CNRS-Universite
cedex, France
́
Rennes 1, Avenue du General Leclerc, 35042 Rennes
́
́
§AM2N UMR 5253 CNRS-Ecole Nationale de Chimie de Montpellier (ENSCM), 8 rue de l’Ecole Normale, 34296 Montpellier cedex
5, France
∥Laboratoire Charles Coulomb UMR 5221 CNRS-UM2, Dep
́
artement Semiconducteurs Mater
́ ́
iaux et Capteurs, Universite
Montpellier 2, Place Eugen
̀
e Bataillon, 34095 Montpellier cedex 5, France
S
* Supporting Information
ABSTRACT: A series of H-bonded supramolecular architectures were built
from monofunctional M−CC−R and bifunctional R−CC−M−CC−R
trans-alkynylbis(1,2-bis(diphenylphosphino)ethane)ruthenium(II) complexes
and π-conjugated modules containing 2,5-dialkoxy-p-phenylene. Incorporation
on each partner of a cyanuric end and of the complementary Hamilton
receptor provided the necessary means to keep the constituents together via
strong hydrogen bonding. Characterization of all architectures has been
performed on the basis of NMR and photophysical methods. In particular, the
formation of a Hamilton receptor/cyanuric acid complex has been exemplified
by an X-ray single-crystal structure determination. Both self-assembly and
accurate modification of the complementary blocks were ensured in such a way
that the resulting materials maintain the responsiveness of the electron-rich
2,5-dialkoxy-p-phenylene spacers toward nitroaromatics.
based supramolecular assemblies. Together with the versatility
of design and the easy access to both monofunctional M−C
C−R and bifunctional R−CC−M−CC−R alkynyl(1,2-
bis(diphenylphosphino)ethane)ruthenium(II) complexes, the
linear and rigid arrangement of atoms in the M−CC−R
structures makes them viable candidates to generate well-
defined and sterically hindered supramolecular architectures,8
as well as for applications in materials chemistry (electron
transfer, nonlinear optics, sensing, etc.).9−11 Using conforma-
tionally rigid trans-alkynyl ruthenium and π-conjugated organic
units containing 2,5-dialkoxy-p-phenylene as molecular mod-
ules bearing respectively Hamilton receptor and cyanuric acid
complementary units12,13 was expected to result in the
preparation of supramolecular architectures.
INTRODUCTION
■
The rational design of responsive multicomponent architec-
tures and materials with controlled geometries and properties is
key in organic (opto)electronics. In this context, the past
decade has witnessed an increasing interest toward supra-
molecular materials.1−6 The tailoring of supramolecular
materials relies on the full control over the self-assembly of
molecular modules with complementary recognition sites and
dedicated functions, with the expectation that the resulting
materials will exhibit distinctive properties and functions.7
Their practical use requires the optimization of their self-
assembly and controlled manipulation and the quantitative
study of their physicochemical properties and responsiveness to
external stimuli.
In this paper, we report on the design of multicomponent
organometallic based supramolecular architectures, in which
2,5-dialkoxy-p-phenylene containing π-conjugated organic units
were incorporated and the evaluation of the optical properties
(fluorescence, responsiveness to external stimuli) of the
resulting assemblies. A large part of this work was devoted to
the design and characterization of the ruthenium acetylide
A second part is dedicated to the responsiveness of these
architectures in which the fluorescence properties and
sensitivity of π-conjugated organic units containing 2,5-
dialkoxy-p-phenylene to the electron acceptor aromatic ring
Received: August 20, 2013
Published: January 29, 2014
© 2014 American Chemical Society
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Figure 1. Chemical structures of supramolecular assemblies formed from complexes 3 and 4 and from the conjugated cores 1a (Alk = C8H17), 1b
(Alk = C12H25), and 2.
of nitroaromatics14,15 were studied. This study presents an
example of how multiple hydrogen bonds could be employed
to construct multifunctional architectures, as an alternative way
to coordination-driven self-assembly to form tunable supra-
molecular coordination complexes (SCCs).16−18
Altogether, we demonstrate here that both self-assembly and
controlled manipulation of monofunctional M−CC−R and
bifunctional R−CC−M−CC−R alkynyl(1,2-bis-
(diphenylphosphino)ethane)ruthenium(II) complexes and π-
conjugated organic units containing 2,5-dialkoxy-p-phenylene
as complementary blocks can be ensured. In particular, we
discuss how the complementary blocks were designed in such a
way that the resulting materials exhibit distinctive properties, as
for instance fluorescence and responsiveness to nitroaromatics.
for their ability to form an ADAD−DADA pair, via quadruple
hydrogen bond formation.8 (1,2-Bis(diphenylphosphino)-
ethane)ruthenium(II) species were thus chosen as termini,
because of the versatility of design. Furthermore, with an
overall size of 1.2 nm,25,26 monofunctional M−CC−R and
bifunctional R−CC−M−CC−R rigid organometallic units
(M = (1,2-bis(diphenylphosphino)ethane)ruthenium(II)) con-
stitute ideal hindered building blocks to create an envelope
around the central sensitive units. Applying bifunctional R−
CC−M−CC−R units can also provide supramolecular
oligomeric species in which the cores containing 2,5-dialkoxy-p-
phenylene will be inserted through noncovalent bonds.
For these reasons, our approach focused on the design of
trans-[(dppe)2Ru(X)(CC−R)] bearing one (X= Cl) or two
(X = CC−R) Hamilton receptors at the remote end(s) of
alkynylruthenium derivatives 3 and 4 (Figure 1). Upon
complexation of the Hamilton receptor with cyanuric
derivatives, a six-point hydrogen bonding motif is formed that
has been proved to be relatively stable at moderate temperature
in nonpolar solvents.12,27−31 In furtherance of this design, an
important goal concerns the modification of the absorption and
emission properties of the 2,5-dialkoxy-p-phenylene cores in
these assemblies. Structural modifications of the core were thus
investigated to preserve the optical response of the central units
to nitroaromatics such as trinitrotoluene (TNT) or its
derivative 2,4-dinitrotoluene (DNT) within the assemblies.
1,4-Diethynyl-2,5-dialkoxybenzenes (6a,b) containing π-
conjugated organic units were first synthesized as central
RESULTS AND DISCUSSION
■
Methods. Various approaches by our group and others
provided evidence that the accurate design of functional alkynes
allows the versatile generation of discrete assemblies of rigid-
rod transition-metal σ-acetylides, featuring a controlled
geometry. For instance, alkynes substituted by nucleobases
and by urea-pyrimidinedione constitute valid candidates that
allow for the synthesis of transition-metal species capable of
acting as supramolecular synthons, both in solution and in the
solid state.19−24 In particular, trans-[(dppe)2Ru(Cl)(CC−
R)] (dppe = (1,2-bis(diphenylphosphino)ethane)) species
bearing terminal bis(acylamino)triazine moieties can be used
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a
Scheme 1. Synthesis of 1a,b
a
Reagents and conditions: (a) 2.3 equiv of (trimethylsilyl)acetylene (TMSA), 0.02 equiv of PdCl2(PPh3)2, 0.04 equiv of CuI, iPr2NH, THF, 60 °C,
16 h, then NaOH, MeOH, THF, room temperature, 5 h, 6a 85%, 6b 73%; (b) 7, 1 equiv of 4-iodoaniline, H2SO4, HNO3, 0°C, 3 h, 40%; (c) 8, 4.75
equiv of N,N′-carbonyldiimidazole, 5.9 mL of 1 M t-BuOK in THF, THF, 60 °C, 24 h, 77%; (d) 2.2 equiv of 6a or 6b, 9, 0.01 equiv of PdCl2(PPh3)2,
0.02 equiv of CuI, 0.02 equiv of PPh3, NEt3, THF, room temperature, 72 h, 1b 45%.
building blocks, to which cyanuric end groups were attached
through a Sonogashira coupling, leading to 1a,b (Scheme 1). N-
(4-Iodophenyl)isocyanuric acid (9) was previously obtained
from the reaction of 1-(4-iodophenyl)biuret (8)32 and N,N′-
carbonyldiimidazole in the presence of potassium tert-butoxide.
Long chains (6b) were necessary to ensure that the compounds
1 were sufficiently soluble. 1a was obtained as a yellow solid,
hardly soluble in hot THF and DMSO but not soluble enough
to allow for purification and characterization.
Conversely, 1b was soluble enough to be flash chromato-
graphed on silica gel successively with dichloromethane and
tetrahydrofuran as eluents and was further purified by
crystallization from hot methanol.
temperature for 48 h. 20 was finally obtained as a brown
product using a slight excess of potassium fluoride in methanol
at ambient temperature and characterized by NMR spectros-
copy and mass spectrometry.
The reaction of a slight excess (∼1.2 equiv) of [cis-
(Cl)(PPh2CH2CH2PPh2)2Ru][TfO] and alkyne 20 in dichloro-
methane at room temperature for 4 days resulted in the
formation of an intermediate vinylidene species.33 The reaction
was monitored by 31P NMR in order to ensure its completion.
This intermediate was clean enough to be used in the next step
and was then deprotonated using dry potassium tert-butoxide
(room temperature, 16 h). The resulting alkynyl compound
was washed with water before being purified by diphasic
recrystallization from dichloromethane/pentane (1/2) as a
yellow powder in approximately 30% yield. All the spectro-
scopic data of 3 are consistent with the proposed structure
(Scheme 3).
4 was obtained by modifying this procedure: the reaction of
3 equiv of alkyne 20 and [cis-(Cl)(PPh2CH2CH2PPh2)2Ru]-
[TfO] in dichloromethane at room temperature for 2 days
resulted in the formation of the same vinylidene species, as
monitored by 31P NMR. To this intermediate species were then
added successively 3 equiv of both KPF6 and triethylamine.
This mixture was stirred at 30 °C for 24 h, to ensure the
completion of the reaction as probed by 31P NMR (δ(CDCl3)
54.6 ppm). 4 was washed with water before being purified by
diphasic crystallization from dichloromethane/pentane (1/2) as
a yellow powder in approximately 50% yield. All products gave
In a second step, we synthesized the π-extended analogue 2
in four steps from 1,4-dibromo-2,5-dioctyloxybenzene (5a)
(Scheme 2).
The preparation of the ruthenium derivatives has been
adapted from previously reported procedures (Scheme 3).33
The alkyne 20 was obtained by classical Sonogashira coupling
and deprotection procedures from the precursor N,N′-bis[6-
(3,3-dimethylbutyrylamino)pyridin-2-yl]-5-iodoisophthalamide
(19).34 This precursor was obtained from the reaction of 5-
iodoisophthaloyl dichloride (18) and 2 equiv of N-(6-
aminopyridin-2-yl)-3,3-dimethylbutyramide (17), in the pres-
ence of triethylamine. 20 was achieved by the Sonogashira
coupling of 19 with (trimethylsilyl)acetylene (TMSA) in the
presence of PdCl2(PPh3)2 and CuI. The reaction was carried
out in a 1:1 mixture of THF and diisopropylamine at room
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a
Scheme 2.
a
Reagents and conditions: (a) 5a (2.00 g; 4.0 mmol), 2.25 equiv of n-BuLi, THF, −78°C, 3 h, then 2.25 equiv of DMF, −78 °C, 1 h, −78 °C to
room temperature, 2 h, 34%; (b) 14, 2.2 equiv of (7-bromo-9,9-dioctyl-9H-fluoren-2-yl)methyldiethylphosphonate, 2.6 equiv of t-BuOK, THF, 0 °C
to room temperature, overnight, 30%; (c) 15, 2.2 equiv of TMSA, 0.03 equiv of Pd(PPh3)2Cl2, PPh3 (10.0 mg, 0.083 equiv), and 0.03 equiv of CuI,
Et3N, THF, reflux, 70 h, then n-Bu4NF (0.9 mL 1 N solution in THF), THF, room temperature, 18 h, 71%; (d) 16, 3 equiv of 9, 0.1 equiv of
PdCl2(PPh3)2, 0.16 equiv of CuI, and 0.11 equiv of PPh3, NEt3, room temperature, 4 days, 70%.
satisfactory proton and 13C NMR and elemental analysis. The
31P NMR spectra of complexes 3 and 4 show a single sharp
singlet, which is consistent with the trans arrangement of the
diphosphine ligands around the ruthenium; as expected, these
signals appear at δ 49.8 ppm for the mono-alkynyl and δ 54.6
ppm for the bis-alkynyl complexes.8,11,35,36
The electronic absorption spectra of 3 and 4 in dichloro-
methane solution exhibit intense absorption bands at 250−305
nm and less intense bands at 365 nm (Table 1 and Figure S1
(Supporting Information)). With reference to previous
spectroscopic work on monofunctional M−CC−R and
bifunctional R−CC−M−CC−R organometallic units (M
= (1,2-bis(diphenylphosphino)ethane)ruthenium(II)), the
high-energy intense absorption bands are assigned to intra-
ligand (IL) transitions of the diphenylphosphine and alkynyl
ligands. The broad bands from 330 to 430 nm which show a
hyperchromic shift from 3 to 4 (3, ε = 12050 dm3 mol−1 cm−1;
4, ε = 30525 dm3 mol−1 cm−1) are assigned to dπRu → π*CCR
metal-to-ligand charge transfer (MLCT)37,38 transitions. These
complexes do not exhibit any luminescence at room temper-
ature.
nm. The band positions of UV−vis and fluorescence spectra are
thus almost the same for 1b with respect to that of the parent
1,4-bis(phenylethynyl)-2,5-bis(alkoxy)benzene compounds.39
The incorporation of the cyanuric termini does not bring
about changes to the electronic structure of the conjugated
core, even if a small bathochromic shift (∼5−10 nm) is
observed in absorption and emission with respect to 1,4-
bis(phenylethynyl)-2,5-bis(alkoxy)benzene models. We can
also observe that the lowest energy absorption band of 1b is
fully overlapped by the MLCT absorption of both 3 and 4,
while the absorption spectra of these complexes partially cover
the emission of 1b.
The absorption and emission spectra of 2 in dichloro-
methane clearly demonstrate the influence of the styryl
substitution and the insertion of fluorene units in the
conjugated core (Figure 2). The absorption spectrum shows
three main peaks from λ 320 to 370 nm and an intense broad
band, its maximum absorption peak being located at 420 nm,
which can be attributed to the π−π* transitions within the
molecular backbone.40 The bands at higher energy may result
from resonant interaction with the oxygen lone pairs.39 The
main emission peak appears at 475 nm, with a shoulder peak at
525 nm. The influence of the styryl substitution and the
insertion of fluorene units from 1b to 2 is thus reflected by a
large red shift of the longest wavelength absorption edge (57
The absorption spectrum of 1b in dichloromethane exhibits
two intensity maxima centered around 320 and 375 nm (Figure
S2 (Supporting Information)). 1b also exhibits fluorescence
emission with a maximum at 418 nm and a shoulder at ∼430
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a
Scheme 3.
a
Reagents and conditions: (a) 17, 1 equiv of NEt3, 0.5 equiv of 18, THF, 0 °C, 4 h, room temperature, 48 h, 85%; (b) 1.49 mmol of 19, 1.2 equiv of
TMSA, 0.015 equiv of PdCl2(PPh3)2, 0.03 equiv of CuI, 0.03 equiv of PPh3, NEt3, THF, room temperature, 48 h, 93%; (c) KF, MeOH, room
temperature, 16 h, 93%; (d) [ClRu(dppe)2][TfO], 0.9 equiv of 20, CH2Cl2, room temperature, 4 days, then t-BuOK, CH2Cl2, room temperature,
32%; (e) [ClRu(dppe)2][TfO] (250 mg, 0.23 mmol), 3 equiv of 20, CH2Cl2, 2 days, then 3 equiv of KPF6, 2.3 equiv of NEt3 30 °C, 24 h, 48%.
Table 1. Photophysical Data for Complexes 3 and 4 and 2,5-
Dialkoxybenzene Derivatives in Dichloromethane Solution
a
b
complex
λmax (nm) (ε, L mol−1 cm−1
)
λem (nm)
1b
2
318 (29850), 323 (28760), 377 (26520)
350 (24650), 364 (25273), 420 (42000)
309 (32000), 360 (12050)
418
475
3
4
308 (78015), 365 (30525)
a
b
Only the largest absorption maxima are given. Wavelength of
emission maximum on excitation at the absorption maximum.
nm; 2715 cm−1) and of the fluorescence spectrum (57 nm;
2871 cm−1), far from the lowest energy absorption bands of the
ruthenium complexes 3 and 4.
Solution-State 1H NMR Titrations. The association
constants of the supramolecular complexes 3·11 and 4·112
(see Scheme 4) were determined by 1H NMR titration
experiments. The experiments were performed by the stepwise
addition of 50 μL fractions of a 2.0 × 10−2 M solution of 11 to
0.4 mL of a 2.0 × 10−2 M solution of 3 or 1.0 × 10−2 M 4 in
CDCl3.
The resonances of the NHint and NHext protons can be
observed at δ 7.5 and 8.2 ppm as singlets, which is a
characteristic of Hamilton receptor derivatives in apolar, non
coordinating solvents such as CDCl3.13,41 Dilution studies (50−
100 μM) in CDCl3 revealed weak self-binding for compound 3
at room temperature (Figure S3 (Supporting Information)). A
Figure 2. Absorption (3 × 10−5 M in CH2Cl2) at 298 K and emission
(3 × 10−6 M in CH2Cl2; λex 410 nm) spectra of 2. The absorption
spectrum of 4 is indicated for comparison.
fit of the chemical shift data for NHext of 3 afforded estimated
maximum binding constant Kassoc values of 50 M−1 for dimer 3·
3. Upon complexation of the Hamilton receptor with the
cyanuric acid derivative 11, a six-hydrogen bonding motif was
expected to be formed. During this process, the NH resonances
of the Hamilton receptor underwent a continuous downfield
shift until the complete formation of the complexes was
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Scheme 4. Structures of the Molecules Used for the Self-Assembly NMR Studies of 3, 4, and 11
Figure 3. Self-assembly study between 3 and 11 (0, 0.5, 1.0, 1.5, 2.0, and 3.0 equiv of 11 from bottom to top). Stock solutions were prepared with
dissolved 3 (15 mg, 2 × 10−3 mol) and 11 (5.60 mg, 2 × 10−3 mol) in 5 mL of CDCl3. A 0.4 mL portion of the solution of 3 was titrated with 0.05
1
mL aliquots of the solution of 11. The mixture was kept at room temperature for /2 h, in order to ensure the establishment of H-bonding
associations.
obtained. After the addition of 0.5 equiv of 11, a broad signal
attributed to the NH protons of the cyanuric moiety was
observed at δ 13.0 ppm. The resonance of these NH protons
underwent a high-field shift and increased broadening in the
course of the experiment, due to fast exchange processes
between free and bound cyanurate (Figure 3, 3·11; Figure S4
(Supporting Information), 4·112).
stoichiometries (Figures S5 and S6 (Supporting Information)).
On the basis of these experiments, the association constants
Kassoc were determined using a nonlinear curve-fitting
procedure.42,43 The calculated values log K1 ≈ 4 (3:11) and
log K1K2 ≈ 8.7 (4:11) are in agreement with those reported
earlier for cyanuric Hamilton systems.28 The association
constants of the complexes 4:11 and 4:112 were thus calculated
to be in the same range (log K1 ≈ 4 and log K2 ≈ 4.7). These
findings suggest that the two receptor units in 4 almost act
A Job plot analysis of the titration data was carried out, which
confirmed the expected 1:1 (3:11) and 1:2 (4:11)
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independently and undergo continuous self-assembly and
disassembly processes.43,44
by units involved in hydrogen bonding are close to linearity
(<3°). Interestingly, the arms of the Hamilton receptor are
twisted with respect to the plane of the aromatic core (C(63)−
C(66)). The cyanuric unit thus forms a ∼45° angle with the
Ru−C(61)−C(62)−C(66) axis. Thus, the formation of the
cyanuric Hamilton receptor complex forces the branches of the
receptor to an important torsion, as revealed by the measure of
the C(O)−NH torsion angles (from 23.90 to 27.15° in 3:10)
in comparison to the values in a free Hamilton receptor (from
9.0 and 13.47°).28 More details are given in Figure S8
(Supporting Information).
Fluorescence Emission of 1b and 2 in the Presence of
3. The efficiency of emission of 1b in CH2Cl2 is strongly
affected by the presence of 3. Indeed, as shown in Figure 5a, the
emission intensity of 1b (2.0 × 10−6 M in dichloromethane)
decreased gradually with the introduction of increasing
amounts of 3 (λexc 375 nm). Conversely, the emission efficiency
of 2 remains unaffected by the introduction of large amounts of
3 (Figure 5b; λexc 410 nm). Its lifetime (approximately 0.9 ns)46
remains unchanged (Table S4 (Supporting Information)).
Note that the emission intensity of 2 also decreased gradually
with the introduction of increasing amounts of 3, when λexc is
375 nm (Figure S7 (Supporting Information)). This contrast-
ing behavior can be related to the large red shift of the longest
wavelength absorption edge (∼50 nm) and of the fluorescence
spectrum (∼50 nm), from 1b to 2. The lowest energy
absorption band of 2 is far from the lowest energy absorption
bands of the ruthenium complexes 3 and 4, whereas the lowest
energy absorption band of 1b is fully overlapped by the MLCT
absorption of both 3 and 4. The styryl substitution and the
insertion of fluorene units in the conjugated core of 2 is thus
essential for maintaining the efficiency of emission of π-
conjugated modules in the assemblies with 3.
Determination of the binding constants for supramolecular
oligomeric assemblies from 4 and 1b or 2 is a priori not
possible due to the underlying complex variety of equilibrating
species. However, it can be assumed that the two cyanuric
binding heads of the ditopic cyanurate wedges 1b and 2 exhibit
an affinity for the receptor heads of the ditopic Hamilton
system 4 comparable to that of the monotopic receptor 11.
X-ray Structure Determination of the Complex 3:10.
Single crystals suitable for X-ray structure determination of a
complex formed by the addition of 3 to a solution of 5-phenyl-
2,4,6-(1H,3H,5H)-pyrimidinetrione (10) in THF (10 is not
soluble in CH2Cl2), evaporation of the solvents, dissolution in
CH2Cl2, filtration, and slow diffusion of heptane gave us
unambiguous information about the hydrogen bonding in these
systems. Selected bond lengths and angles are given in Table S2
(Supporting Information). Details of the X-ray analysis are
given in Table S3 (Supporting Information). A plot of the
complex 3:10 is shown in Figure 4. The solid-state structure
Responsiveness to External Stimuli: Sensing DNT by
Fluorescence Quenching in Solution. The use of
compound 2 to detect amounts of 2,4-dinitrotoluene (DNT)
in CH2Cl2 solution by fluorescence quenching was evaluated.
DNT, which is an impurity of TNT, is safer and easier to detect
in the gas phase than 2,4,6-trinitrotoluene (TNT), which is one
of the most widely used compounds in industrial and military
explosives. The fluorescence quenching efficiency is normally
rated by the Stern−Volmer constant (Ksv). Such quenching
between an electron-rich fluorophore and DNT is generally
associated with an intermolecular photoinduced electron
transfer whose efficiency mainly relies on the π−π interaction
between the electron-poor DNT and the fluorophore. In
addition, the LUMO energy level of the fluorophore has to be
higher than the HOMO energy level of DNT.
The emission spectra of 2 in the presence of various
concentrations of DNT demonstrated efficient fluorescence
quenching. Excitation was performed at 430 nm, where neither
DNT nor 3 absorbs. As shown in Figure 6b, a linear plot
(Stern−Volmer plot) is obtained when the relative fluorescence
intensity (I°/I) is plotted as a function of the quencher
concentration ([Q]). The slope of the line gives the Stern−
Volmer constant (Ksv) and was thus evaluated at 56 L mol−1.
Similarly, the quenching efficiency by DNT of the
fluorescence of the 2·32 complex was studied: Two ratios (2
equiv of 3 vs 2 and 4 equiv of 3 vs 2) for the mixtures were
used in order to ensure the formation of the complex in
CH2Cl2. The final concentration of 2 remained constant for
each solution (4.8 × 10−6 M in CH2Cl2).
Figure 4. Drawing of complex 3:10 in the crystalline state: (a) top
view; (b) side view.
revealed a monomeric structure, in which the cyanuric head of
10 was hydrogen-bonded to the Hamilton receptor of trans-
[(dppe)2Ru(Cl)(CC−R)] (3). Most bond lengths and
angles about the Cl−Ru−C(61)−C(62)−C(63) unit in this
structure are classical. For instance, the Cl−Ru (2.492(1) Å),
Ru−C(61) (2.009(5) Å), C(61)−C(62) (1.202(6) Å), and
C(62)−C(63) (1.433(6) Å) data for this complex fall within
the range of those previously reported for related octahedral
trans-bis(bidentate phosphine)ruthenium alkynyl com-
plexes.8,11,36,45 The angles formed by the Ru−C(61)−C(62)
and C(61)−C(62)−C(63) bonds are close to linearity
(174.6(5) and 177.7(6)°).
The Hamilton receptor unit and the cyanuric acid head are
involved in a network of six hydrogen bonds. The hydrogen-
bond distances range from 2.06 and 2.14 Å. The angles formed
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Figure 5. (a) Changes of the PL intensity of 1b (3 × 10−6 M) in CH2Cl2 upon addition of 3 (0.0−3.0 equiv, λexc 375 nm). (b) Changes of the PL
intensity of 2 (3 × 10−6 M) in CH2Cl2 upon addition of 3 (0.0−3.0 equiv, λexc 410 nm).
Figure 6. (a, left) Changes of the PL intensity of 2 (4.8 × 10−6 M in CH2Cl2) when a DNT solution is added (0−10 mM, λexc 430 nm). (b, right)
Stern−Volmer plot extracted from the variation of the relative fluorescence intensity of 2 (I°/I) recorded at 475 nm for low concentrations of added
DNT (0−2.25 mM).
Figure 7. Stern−Volmer plots extracted from the variation of the relative fluorescence intensity of 2 (I°/I) recorded at 475 nm for low
concentrations of added DNT: (a, left) in the presence of 2 equiv of 3; (b, right) in the presence of 4 equiv of 3.
Detection limits for both 2 and 2·32 were determined to be 6
× 10−2 mM (see more details in the Supporting Informa-
tion).47,48 The response of 2 and 2·32 to commonly found
chemicals that may affect the detection of DNT was studied.
Values of Ksv determined for various aliphatic or aromatic
molecules are reported in Table S5 (Supporting Information).
The largest values of Ksv are observed for DNT (50 and 48 L
mol−1). The others values of Ksv are in the range 8−14 L mol−1
except for a nitroaliphatic compound (22 L mol−1). It can be
observed that the complexation of molecule 2 by 3 has no effect
on the selectivity of the detection of aromatic and aliphatic
species studied.
The quenching efficiency was determined from the Stern−
Volmer plot, the fluorescence signal measured at 475 nm, with
an excitation at 430 nm. The plots clearly showed that the
fluorescence quenching of the complex 2·32 upon addition of
aliquots of a DNT solution is similar to that of 2 under the
same conditions (see Figure 7). This qualitative observation is
confirmed by the Ksv values, 48 and 50 L mol−1 respectively, for
the two ratios (3:2 = 2 and 3:2 = 4). These values are not
significantly different from that of the free 2 system.
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Preparation of 1,4-Bis(alkyloxy)-2,5-diethynylbenzenes
(6a,b). 5a,b. A three-necked flask was equipped with a magnetic
stirrer, a condenser, and a funnel. To a mixture of 2,5-bis(alkyloxy)-
benzene (30 mmol), sodium acetate trihydrate (60 mmol), and acetic
̀
The nature of the interaction of the quenching agent with the
complex 2·32 and with the molecule 2 was interrogated by
fluorescence lifetime measurements, in order to determine the
nature of the observed quenching. Indeed, a linear Stern−
Volmer relationship may be observed if either a static or
dynamic quenching process is dominant. Meanwhile, static and
dynamic quenching can be distinguished by lifetime measure-
ments: dynamic quenching reduces the apparent fluorescent
lifetime, while static quenching merely reduces the apparent
concentration of the fluorophore but not the apparent lifetime,
being largely independent of the fluorescence intensity and
fluorophore concentration.49 For our systems, there are almost
no changes in the fluorescence lifetimes (∼0.9 ns) of the
emission with the addition of the quencher, as demonstrated by
the results shown in Table S4 and Figure S9 (Supporting
Information). This allows us to conclude that a static complex
may have been formed before the fluorophore is excited, and
thereby static quenching may apply in both cases.
acid (35 mL) was added bromine (3.0 mL, 60 mmol) dropwise, and
the mixture was stirred at room temperature overnight. A 100 mL
portion of ice/water was poured into the solution. The solids were
dissolved in dichloromethane, and the solution was washed with water
and then with 5% sodium carbonate, until the aqueous phase remained
neutral. The combined organic layers were dried with magnesium
sulfate. After removal of the solvent, the crude products were purified
by crystallization from pentane to give 5a,b as white powders.
5a (9.50 g, 64%). Anal. Calcd for C22H36Br2O2: C, 53.67; H, 7.37.
1
Found: C, 53.43; H, 7.16. H NMR (200.13 MHz, CDCl3, 297 K): δ
7.11 (s, 2H; Ar H), 3.97 (t, J = 6.5 Hz, 4H; OCH2), 1.79 (m, 4H;
OCH2CH2), 1.57−1.21 (m, 20H; CH2), 0.91 (t, 6H, J = 6.5 Hz; CH3).
13C NMR (50.32 MHz, CDCl3, 300 K): δ 147.6, 117.4, 110.9, 68.0,
31.9, 29.6, 29.3, 25.9, 22.6, 14.1.
5b (9.97 g, 74%). Anal. Calcd for C30H52Br2O2: C, 59.60; H, 8.67.
1
Found: C, 59.63; H, 8.76. H NMR (200.13 MHz, CDCl3, 297 K): δ
7.11 (s, 2H; Ar H), 3.93 (t, J = 6.4 Hz, 4H; OCH2), 1.79 (m, 4H;
OCH2CH2), 1.55−1.21 (m, 36H; CH2), 0.90 (t, J = 6.7 Hz, 6H; CH3).
13C NMR (50.32 MHz, CDCl3, 300 K): δ147.5, 117.4, 110.9, 68.0,
31.9, 29.7, 29.6, 29.4, 29.3, 29.2, 26.0, 22.7, 14.1.
These results demonstrate that the formation of the complex
2·32 does not significantly disturb the π−π interaction between
the electron-poor DNT and the fluorophore 2 in solution, even
on integration in a H-bonded supramolecular entity.50
1,4-Bis(octyloxy)-2,5-diethynylbenzene (6a). 1,4-Bis-
((trimethylsilyl)ethynyl)-2,5-bis(dodecyloxy)benzene was obtained
from 5a (3.00 g, 6.09 mmol) in THF (40 mL) and iPr2NH (20
mL). Under argon protection, (trimethylsilyl)acetylene (0.95 g, 14
mmol), PdCl2(PPh3)2 (90 mg, 0.13 mmol), and CuI (45 mg, 0.24
mmol) were added to the solution. The mixture was then stirred under
argon at 60 °C for 16 h. The solvent was then removed in vacuo. The
residue was dissolved in Et2O (50 mL) before being washed with H2O
(2 × 20 mL) and brine (20 mL). The organic phase was then dried
(Na2SO4). After the solvent was removed in vacuo, column
chromatography (SiO2, pentane/Et2O 97/3) was carried out to
provide 1,4-bis((trimethylsilyl)ethynyl)-2,5-bis(octyloxy)benzene as a
yellow oil (3.05 g, 95%), which was used without further purification
CONCLUSION
■
We have reported here the design of H-bonded supramolecular
complexes based on bulky monofunctional M−CC−R and
bifunctional R−CC−M−CC−R trans-alkynylbis(1,2-bis-
(diphenylphosphino)ethane)ruthenium(II) complexes and
complementary π-conjugated blocks. This study focused on
the integration of accurate 2,5-dialkoxy-p-phenylene cores,
owing to their high level of fluorescence and potential
sensitivity to the electron-acceptor aromatic ring of nitro-
aromatics. Self-assembly was ensured by the presence of
Hamilton receptor and cyanuric acid complementary termini.
In order to exemplify how such architectures can be employed,
we studied the physicochemical properties of various 2,5-
dialkoxy-p-phenylene cores within the resulting supramolecular
complexes as well as their responsiveness to nitroaromatics.
This quantitative study was essential to allow the accurate
design of extended conjugated cores, in such a way that the
supramolecular assemblies maintain the responsiveness of the
electron-rich 2,5-dialkoxy-p-phenylene spacers toward nitro-
aromatics.
1
for the next step. H NMR (200.13 MHz, CDCl3, 297 K): δ 6.91 (s,
2H; Ar H), 3.96 (t, J = 6.4 Hz, 4H; OCH2), 1.81 (m, 4H; OCH2CH2),
1.67−1.20 (m, 20H; CH2), 0.91 (t, 6H; CH3), 0.27 (s, 18H,
Si(CH3)3). 13C NMR (50.32 MHz, CDCl3, 300 K): δ 151.3, 117.4,
111.2, 106.8, 102.7, 68.1, 31.9, 29.6, 29.3, 25.9, 22.6, 14.1, 0.1.
1,4-Bis((trimethylsilyl)ethynyl)-2,5-bis(octyloxy)benzene (3.06 g,
5.81 mmol) was dissolved in a mixture of MeOH (30 mL) and
THF (10 mL). The reaction mixture was purged with an argon flow
for 15 min. A 2.25 mL portion of a 2.5 N NaOH solution was added.
The mixture was stirred at room temperature for 5 h. The solvents
were removed in vacuo. The residue was then dissolved in CH2Cl2 (5
mL) before being washed with H2O (2 × 3 mL) and brine (3 mL) and
dried (Na2SO4). After the solvent was removed in vacuo, column
chromatography (SiO2, CH2Cl2) was carried out to afford the product
6a as a yellowish solid (2.22 g, 89%). Anal. Calcd for C26H38O2: C,
EXPERIMENTAL SECTION
The synthesis and characterization of organic derivatives 10 and 11 is
described in the Supporting Information.
■
1
81.61; H, 10.02. Found: C, 81.59; H, 10.31. H NMR (200.13 MHz,
CDCl3, 297 K): δ 6.94 (s, 2H; Ar H), 3.97 (t, J = 6.6 Hz, 4H; OCH2),
3.35 (s, 2H; CH), 1.79 (m, 4H; OCH2CH2), 1.56−1.2 (m, 20H;
CH2), 0.91 (t, J = 5.1 Hz, 6H; CH3). 13C NMR (50.32 MHz, CDCl3,
300 K): δ 151.3, 117.4, 109.2, 81.9, 78.7, 68.1, 31.9, 29.7, 29.3, 25.9,
22.6, 14.1.
Preparation of the Dialkoxybenzene Derivatives with
Cyanuric Heads (Schemes 1 and 2). N-(4-Iodophenyl)isocyanuric
acid (9) was obtained from the reaction of 1-(4-iodophenyl)biuret
(8;32 250 mg, 0.82 mmol) in THF (8 mL) and N,N′-carbon-
yldiimidazole (640 mg, 3.9 mmol). A 5.9 mL portion of a 1 M
potassium tert-butoxide solution in THF was added to the solution.
The mixture was stirred under argon at 60 °C for 24 h. After the
solvent was removed in vacuo, 100 mL of ethyl acetate and 100 mL of
1 M HCl were added. The organic phase was washed twice with brine
and dried with sodium sulfate. After removal of the solvent in vacuo,
silica gel column chromatography (CH2Cl2/EtOAc; 2/1) was carried
out to afford the product 9 as a pale yellow powder (210 mg, 77%).
Anal. Calcd for C9H6IN3O3: C, 32.63; H, 1.83; N, 12.69. Found: C,
1,4-Bis(dodecyloxy)-2,5-diethynylbenzene (6b). Similarly, 1,4-bis-
((trimethylsilyl)ethynyl)-2,5-bis(dodecyloxy)benzene was obtained
from 5b (3.7 g, 6.09 mmol) and was used without further purification
1
for the next step (3.66 g, 94%). H NMR (200.13 MHz, CDCl3, 297
K): δ 6.93 (s, 2 H; Ar H), 3.97 (t, J = 6.4 Hz, 4 H; OCH2), 1.79 (m, 4
H; OCH2CH2), 1.46−1.26 (m, 36 H; −(CH2)−), 0.88 (t, J = 6.4 Hz,
6 H; CH3), 0.28 (s, 18H, Si(CH3)3). 13C NMR (50.32 MHz, CDCl3,
300 K): δ 153.9, 117.7, 113.2, 107.8, 103.6, 69.6, 31.9, 29.7, 29.6, 29.4,
29.2, 29.1, 25.9, 22.7, 14.0, 0.1.
1
32.12; H, 1.61; N, 12.58. H NMR (200.13 MHz, DMSO-d6, 297 K):
δ 11.60 (br, 2H,; NH), 7.82 (d, J = 6.5 Hz, 2H; C6H4), 7.16 (d, J = 6.5
Hz, 2H; C6H4). 13C NMR (50.32 MHz, DMSO-d6, 300 K): δ 149.6,
148.9, 137.7, 134.2, 131.6, 94.9.
1,4-Bis((trimethylsilyl)ethynyl)-2,5-bis(dodecyloxy)benzene (1.06
g, 1.66 mmol) was dissolved in THF (15 mL). The reaction mixture
was purged with an argon flow for 15 min. A 1.78 mL portion of tetra-
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n-butylammonium fluoride (1 M solution in THF) was added. The
mixture was stirred at room temperature for 2 h. The solvent was
removed in vacuo. The residue was then dissolved in Et2O (50 mL)
before being washed with H2O (2 × 30 mL) and brine (30 mL). The
organic phase was then dried (Na2SO4). After the solvent was
removed in vacuo, column chromatography (SiO2, pentane/CH2Cl2
9/1) was carried out to afford the product 6b as a yellow solid (624
mg, 77%). Anal. Calcd for C34H54O2: C, 82.53; H, 11.00. Found: C,
82.12; H, 10.61. 1H NMR (200.13 MHz, CDCl3, 297 K): δ 6.96 (s, 2
H), 3.98 (t, J = 6.4 Hz, 4 H; OCH2), 3.34 (s, 2 H; CH), 1.79 (m, 4 H;
OCH2CH2), 1.54−1.20 (m, 36 H; CH2), 0.9 (t, J = 6.4 Hz, 6 H; CH3).
13C NMR (50.32 MHz, CDCl3, 300 K): δ 153.8, 117.8, 113.2, 82.4,
79.8, 69.7, 31.9, 29.7, 29.6, 29.3, 29.2, 29.1, 25.9, 22.8, 14.1.
Preparation of 1a,b. 1a. Under argon protection, N-(4-
iodophenyl)isocyanuric acid (9; 477 mg, 1.44 mmol) and 6a (250
mg, 0.65 mmol) were dissolved in THF (20 mL). PdCl2(PPh3)2 (38
mg, 54 μmol), CuI (20 mg, 0.1 mmol), and distilled NEt3 (5 mL) were
added to the solution. The mixture was then stirred at room
temperature for 72 h. The solvent was then removed in vacuo. The
residue was washed several times with CH2Cl2 and ethyl acetate, giving
rise to a yellow solid, hardly soluble in hot THF and DMSO but not
soluble enough to allow for purification and characterization.
Tetra-n-butylammonium fluoride (0.9 mL of a 1 N solution in
THF) was added at room temperature to a stirred solution of this oil
(120 mg, 0.088 mmol) in 5 mL of THF. The reaction mixture was
stirred for 18 h at room temperature, under argon. The solvent was
removed in vacuo, and the residue was chromatographed on a silica gel
column with an n-pentane/CH2Cl2 mixture (90/10 v/v) as eluent. 16
was obtained as a yellow powder (140 mg, 71%). Anal. Calcd for
1
C88H122O2: C, 87.21; H, 10.15. Found: C, 87.87; H, 10.37. H NMR
(500.13 MHz, CDCl3, 297 K): δ 7.70 (d, J = 8.1 Hz, 2H), 7.66 (d, J =
8.1 Hz, 2H), 7.58−7.57 (m, 6H), 7.52 and 7.51 (d, 2 × 1H), 7.50 (br
s, 2H), 7.29 (br s., 2H), 7.27 (d, J = 16.5 Hz, 2H), 7.21 (s, 2H), 4.13
(t, 4H; OCH2), 3.18 (s, 2H; CH), 2.03 (m, 4H; OCH2CH2), 1.68−
1.05 (m, 68H; CH2), 0.94 (t, J = 6.8 Hz, 6 H; CH3), 0.85 (t, J = 7.2
Hz, 12 H; CH3), 0.65 (m, 8H; CH2). 13C NMR (50.32 MHz, CDCl3,
300 K): δ 151.6, 151.2, 151.0, 141.7, 139.9, 137.6, 131.2, 129.3, 127.0,
126,5, 125.5, 123.2, 121.0, 120.3, 120.0, 119.5, 110.6, 84.8, 69.6, 40.4,
31.9, 31.8, 30.1, 29.7, 29.6, 29.5, 29.4, 29.3, 26.4, 23.8, 22.7, 22.6, 14.2,
14.1.
2 was obtained from 16 (60 mg, 49 μmol), 50 mg (147 μmol) of N-
(4-iodophenyl)isocyanuric acid (9), PdCl2(PPh3)2 (4 mg, 4.41 μmol),
CuI (1.5 mg, 7.84 μmol), and PPh3 (1.5 mg, 5.39 μmol) in anhydrous
THF (10 mL) and distilled NEt3 (10 mL). The mixture was stirred at
room temperature for 4 days. After removal of the solvent, 2 was
dissolved in dichloromethane and purified by filtration on Celite (55
mg, 70%). Anal. Calcd for C106H132O8N6: C, 78.65; H, 8.22; N, 5.20.
Found: C, 77.97; H, 8.34; N, 5.38. 1H NMR (200.13 MHz, DMSO-d6,
297 K): δ 11.54 (br, 4H; NH), 7.69 (d, J = 8.1 Hz, 2H), 7.66−7.55
(m, 10H; aromatics), 7.51 and 7.50 (d, 2 × 1H), 7.48 (br s, 2H), 7.29
(br s, 2H), 7.26 (d, J = 16.0 Hz, 2H), 7.21 (s, 2H), 4.14 (t, 4H;
OCH2), 2.05 (m, 4H; OCH2CH2), 1.7−1.15 (m, 68H; −(CH2)−),
0.94 (t, J = 6.8 Hz, 6 H; CH3), 0.85 (t, J = 7.2 Hz, 12 H; CH3), 0.66
(m, 8H). 13C NMR (50.32 MHz, CDCl3, 300 K): δ 151.5, 151.1,
151.0, 149.7, 148.6, 141.7, 139.9, 137.7, 134.8, 131.8, 131.1, 129.7,
129.5, 127.0, 126.5, 125.3, 124.2, 123.1, 121.0, 120.5, 120.3, 119.7,
110.7, 94.9, 87.4, 69.6, 40.5, 31.8, 31.7, 30.1, 29.8, 29.7, 29.5, 29.3,
29.2, 26.4, 23.8, 22.9, 22.7, 14.2, 14.1.
1b. 1b was obtained from 6b (400 mg, 0.808 mmol), 590 mg (1.78
mmol)of N-(4-iodophenyl)isocyanuric acid (9), PdCl2(PPh3)2 (57
mg, 81 μmol), CuI (20 mg, 0.1 mmol), and PPh3 (50 mg, 0.19 mmol)
in anhydrous THF (10 mL) and distilled NEt3 (10 mL). The mixture
was then stirred under argon at room temperature for 72 h. The
solvent was then removed in vacuo. The residue was flash
chromatographed on silica gel, successively with dichloromethane
and tetrahydrofuran as eluents, providing 1b as a yellow solid, which
was further purified by crystallization from hot methanol (328 mg,
45%). Anal. Calcd for C52H64N6O8: C, 69.31; H, 7.16. Found: C,
1
69.21; H, 7.31. H NMR (200.13 MHz, DMSO-d6, 297 K): δ 11.52
(br, 4H; NH), 7.57 (d, J = 8 Hz, 4H; C6H4), 7.38 (d, J = 8 Hz, 4H;
C6H4), 7.19 (s, 2H; C6H2), 4.06 (t, J = 6.4 Hz, 4 H; OCH2), 1.49 (m,
4 H; OCH2CH2), 1.55−1.23 (m, 36H; CH2), 0.81 (t, J = 6.4 Hz, 6 H;
CH3). 13C NMR (50.32 MHz, CDCl3, 300 K): δ 154.4, 149.6, 148.7,
134.7, 131.8, 129.6, 124.2, 117.2, 114.4, 94.2, 87.3, 69.7, 32.4, 30.2,
29.9, 29.7, 29.6, 29.5, 25.4, 23.1, 14.0.
Preparation of the Ruthenium Derivatives with Appended
Hamilton Receptors (Scheme 3). 5-Iodoisophthaloyl Chloride
(18). 5-Iodoisophthalic acid (2 g, 6.84 mmol), prepared according to
the literature,34 was slowly added to thionyl chloride (8 mL, 110.15
mmol), under argon. This mixture was then stirred at reflux for 6 h.
After the mixture was cooled, the solvent was removed by distillation,
and the viscous residue was dried under vacuum overnight. 18 was
Preparation of 2. Preparation of 15. t-BuOK (1.15 g, 1.3 mmol)
was added to a solution of (7-bromo-9,9-dioctyl-9H-fluoren-2-
yl)methyldiethylphosphonate51 (710 mg, 1.1 mmol) and 2,5-
octyloxyterephthalaldehyde (200 mg, 0.5 mmol) in THF (20 mL) at
0 °C. The mixture was stirred overnight. The solution was filtered and
the solid washed with THF. The solvent was removed. The residue
was flash chromatographed on a silica gel column with pentane, which
provided 15 as a yellow solid (430 mg, 30%). Anal. Calcd for
1
used without further purification for the next step. H NMR (200.13
MHz, CDCl3, 297 K): δ 8.87 (t, J = 1.7 Hz, 1H), 8.59 (d, J = 1.7 Hz,
2H). 13C NMR (50.32 MHz, CDCl3, 300 K): δ 165.8, 145.2, 135.5,
132.6, 94.35.
1
N-(6-Aminopyridin-2-yl)-3,3-dimethylbutyramide (17). To a
solution of 2,6-diaminopyridine (2 g, 18.3 mmol) and triethylamine
(2.6 mL, 18.3 mmol) in THF (20 mL) was added (CH3)3CCH2COCl
(1.8 mL, 18.3 mmol) in THF (10 mL) dropwise over 2 h, at 0 °C,
under argon. This mixture was stirred at room temperature for 72 h.
Then the mixture was filtered and the solvent removed in vacuo. The
residue was flash chromatographed on a silica gel column with
dichloromethane and ethyl acetate (4/1) as eluent, which provided 17
as a white solid (1.74 g, 46%). Anal. Calcd for C11H17N3O·2H2O: C,
54.30; H, 8.70; N, 17.27. Found: C, 54.18; H, 8.80; N, 16.87. 1H NMR
(200.13 MHz, CDCl3, 297 K): δ 7.77 (br s, 1H; CONH), 7.55 (d, J =
7.9 Hz, 1H; Hpy), 7.42 (dd, J = 7.9 Hz, 1H; Hpy), 6.23 (dd, J = 7.9 Hz,
J = 0.7 Hz, 1H; Hpy), 4.35 (br s, 2H; NH2), 2.18 (s, 2H;
CH2C(CH3)3), 1.05 (s, 9H; C(CH3)3). 13C NMR (50.32 MHz,
CDCl3, 300 K): δ 170.3, 157.1, 149.9, 140.2, 104.2, 103.3, 51.6, 31.3,
29.8.
Preparation of 20. To a mixture of N-(6-aminopyridin-2-yl)-3,3-
dimethylbutyramide (17; 2.84 g, 13.7 mmol) and triethylamine (1.9
mL, 13.7 mmol) in THF (40 mL) at 0 °C was added 5-
iodoisophthaloyl dichloride (18; 2.24 g, 6.81 mmol) in THF (40
mL) over 1 h. The mixture was stirred at 0 °C for 3 h and at room
temperature for 48 h. The mixture was filtered, and the solid residue
was washed with THF. After removal of the solvent under vacuum,
C84H120Br2O2: C, 76.32; H, 9.16. Found: C, 76.34; H, 9.15. H NMR
(200.13 MHz, CDCl3, 297 K): δ 7.57 (d, J = 8.1 Hz, 2H; Ar H), 7.46
(br s, 4H; Ar H + CH), 7.38 (br s, 6H; ArH), 7.19 (br s, 4H; Ar H),
7.11 (s, 2H), 4.10 (t, J = 6.2 Hz, 4H; OCH2), 1.94 (m, 8H; CH2),
1.40−1.06 (m, 64H; −CH2−), 0.81 (t, J = 6.6 Hz, 18H, CH3), 0.62
(m, 8H, −CH2). 13C NMR (50.32 MHz, CDCl3, 300 K): δ153.2,
151.1, 150.8, 139.9, 139.6, 129.9, 129.2, 126.9, 126.1, 125.5, 123.0,
122.0, 120.9, 119.9, 110.5, 69.5, 55.3, 40.4, 31.9, 31.8, 30.0, 29.7, 29.5,
29.4, 29.3, 29.2, 26.4, 23.7, 22.7, 22.6, 14.1, 14.0.
Preparation of 16. 15 (200 mg, 0.485 mmol), Pd(PPh3)2Cl2 (10
mg, 0.015 mmol), PPh3 (10.0 mg, 0.04 mmol), and CuI (3 mg, 0. 016
mmol) were added to a degassed solution of triethylamine (15 mL)
and THF (5 mL). (Trimethylsilyl)acetylene (90 mg, 0.9 mmol) was
added slowly and dropwise to the suspension. The reaction mixture
was then stirred at reflux for 70 h. After the mixture was cooled, the
solvent was removed under reduced pressure, and the residue was
filtered over a short silica gel column with ether as eluent. A dark
yellow oil was obtained which was used without further purification for
1
the next step. H NMR (200.13 MHz, CDCl3, 297 K): δ 7.68 (d, J =
7.9 Hz, 2H), 7.63−7.56 (m, 10H), 7.46 (br s, 2H), 7.27 (d, J = 16.4
Hz, 2H), 7.21 (br s, 2H), 4.12 (t, 4H; OCH2), 2.00 (m, 4H;
OCH2CH2), 1.61−1.19 (m, 32H; CH2), 0.91 (t, J = 6.8 Hz, 6 H;
CH3), 0.85 (t, J = 7.2 Hz, 12 H; CH3), 0.62 (m, 8H), 0.08 (Si(CH3)3).
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N,N′-bis[6-(3,3-dimethylbutyrylamino)pyridin-2-yl]-5-iodoisophthala-
mide (19) was purified by chromatography on a silica gel column with
dichloromethane and ethyl acetate (3/1) as eluent and obtained as a
white powder (3.89, 85%). MS (ESI): m/z 693.1657 ([M + Na]+,
Anal. Calcd for C116H118N12O8P4Ru·CH2Cl2: C, 66.33; H, 5.71; N,
7.94. Found: C, 66.70; H, 5.73; N, 8.01. 31P{1H} NMR (CDCl3, 81
MHz, 297 K): δ 54.6. 1H NMR (500.13 MHz, CDCl3, 297 K): δ 8.27
(s, 4H; NH), 8.1 (d, 4H, J = 8 Hz; Hpyr), 8.08 (t, 2H, J = 1.6 Hz), 8.06
(d, 4H, J = 8 Hz), 7.81 (t, 4H, J = 8 Hz), 7.62 (s, 4H, NH), 7.56 (m,
16H), 7.26 (m, 12H), 7.07 (m, 16H), 2.63 (m, 8H; CH2), 2.29 (s, 8H;
CH2), 1.11 (s, 36H, C(CH3)3). 13C{1H} NMR (CDCl3, 125 MHz,
1
C30H35IN6O4Na requires 693.1662). H NMR (200.13 MHz, CDCl3,
297 K): δ 8.67 (br s, 2H; NH), 8.38 (br s, 2H; NH), 8.14 (s, 1H), 8.10
(s, 2H), 7.94 (m, 4H), 7.73 (d. J = 8.1 Hz, 2H), 2.27 (s. 4H;
CH2C(CH3)3), 1.11 (s, 18H; CH2C(CH3)3). 13C NMR (125.13 MHz,
CDCl3, 300 K): δ 170.4, 163.0, 149.7, 149.6, 140.6, 140.3, 136.2,
125.2, 109.8, 109.0, 94.6, 51.3, 31.2, 29.5.
1
3
297 K): δ 170.3, 164.7, 149.6, 140.9, 139.82, 136.4 (quint, JPC + JPC
= 12 Hz), 134.1, 131.8, 131.4, 129.2, 129.0, 127.4, 119.9, 115.6, 109.8,
1
3
51.9, 31.3, 29.8 (quint, JPC + JPC = 23 Hz).
N,N′-Bis[6-(3,3-dimethylbutyrylamino)pyridin-2-yl]-
((trimethylsilyl)ethynyl)isophthalamide was obtained from 19 (1 g,
1.49 mmol), PdCl2(PPh3)2 (12 mg, 0.022 mmol), CuI (4 mg, 0.044
mmol), and PPh3 (2 mg, 0.01 mmol) in anhydrous THF (30 mL) and
distilled NEt3 (15 mL). (Trimethylsilyl)acetylene (176 mg, 1.79
mmol) was added slowly and dropwise to the suspension. The reaction
mixture was then stirred at room temperature for 48 h. The solvent
was removed under reduced pressure, and the yellow solid (890 mg,
93%) was purified by chromatography on a silica gel column with a
CH2Cl2/EtOAc 7/1 mixture. MS (ESI): m/z 663.3107 ([M + Na]+,
C35H44N6O4SiNa requires 663.3091). 1H NMR (500.13 MHz, CDCl3,
297 K): δ 8.63 (br s, 2H; NH), 8.37 (br s, 2H; NH), 8.15 (s, 1H), 8.00
(s, 2H), 7.8 (m, 4H), 7.74 (d, J = 8 Hz, 2H), 2.29 (s, 4H;
CH2C(CH3)3), 1.12 (s, 18H; CH2C(CH3)3), 0.3 (s, 9H; Si(CH3)3).
13C NMR (125.13 MHz, CDCl3, 300 K): δ 170.4, 163.7, 150.0, 149.3,
140.7, 125.6, 134.0, 125.6, 124.9, 110.0, 109.5, 102.3, 97.7, 51.2, 31.2,
29.5, −0.6.
ASSOCIATED CONTENT
■
S
* Supporting Information
Text, figures, tables, and a CIF file giving supplementary
crystallographic data (CCDC 950259) for complex 3:10,
detailed preparation of compounds 10 and 11, determination
of association constants by NMR studies, structural data for
complex 3:10, lifetime measurements and selectivity studies,
and NMR spectra of main intermediates. This material is
available free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail for J.-L.F.: jean-luc.fillaut@univ-rennes1.fr.
Notes
Desilylation (500 mg, 0.783 mmol) was obtained by reaction with
KF (68 mg, 11.7 mmol) in MeOH (35 mL), at room temperature for
16 h. A classical workup (water, CH2Cl2) afforded 20 as a brown
powder (430 mg, 97%). MS (ESI): m/z 591.2694 ([M + Na]+,
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
1
■
C32H36N6O4Na requires 591.2695). H NMR (500.13 MHz, CDCl3,
The authors acknowledge the support of the CNRS and
DGRSRT under Grant 08/R 12-06.
297 K): δ 8.54 (br, 2H; NH), 8.44 (br, 2H; NH), 8.18 (s, 1H), 8.00 (s,
2H), 7.90 (m, 4H), 7.77 (d, J = 8 Hz, 2H; C6H3), 3.34 (s, 1H; CH),
2.29 (s, 4H; CH2C(CH3)3), 1.13 (s, 18H; CH2C(CH3)3). 13C NMR
(125.13 MHz, CDCl3, 300 K): δ 170.4, 163.5, 150.0, 149.3, 140.7,
135.2, 134, 126.1, 123.8, 119.9, 109.4, 81.2, 79.8, 51.3, 31.2, 29.5.
Synthesis of 3. In a Schlenk tube, [ClRu(dppe)2][TfO] (500 mg,
0.46 mmol) and 20 (235 mg, 0,414 mmol) were introduced under
argon and dissolved in 10 mL of freshly distilled and degassed
dichloromethane. This mixture was stirred at room temperature for 4
days. The completion of the reaction was monitored by 31P NMR
spectrometry (31P NMR (CH2Cl2 + CDCl3): s, 35.5 ppm). Potassium
tert-butoxide (51 mg, 0.46 mmol) was then added, and the mixture was
stirred for 2 h. A classical workup (water, CH2Cl2) afforded 3 as a
yellow solid (221 mg, 32%) after biphasic crystallization (CH2Cl2/
pentane). Anal. Calcd for C84H83ClN6O4P4Ru·1/2CH2Cl2: C, 65.75; H,
5.49; N, 5.44. Found: C, 65.56; H, 5.70; N, 5.09. 31P{1H} NMR
(CDCl3, 81 MHz, 297 K): δ 49.8. 1H NMR (500.13 MHz, CDCl3, 297
K): δ 8.40 (s, 2H; NH), 8.14 (d, 2H, J = 8 Hz; Hpyr), 8.03 (d, 2H;
Hpyr), 7.97 (s, 1H), 7.80 (t, 2H, J = 8 Hz), 7.63 (s, 2H; NH), 7.56 (m,
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