Zinc- and palladium-porphyrin based turnstiles

Article abstract of DOI:10.1039/c2nj40657h

The design and synthesis of two new Zn(ii) and Pd(ii) strapped-porphyrin based molecular turnstiles have been achieved. These molecules are based on a porphyrin backbone as a stator and a handle as a rotor. The junction between the two parts is ensured by covalent bonds using two opposite meso positions. Both compounds have been characterised in solution by NMR spectroscopy and in the solid state by X-ray diffraction on a single crystal. The dynamic of the two systems have been investigated in solution by 1- and 2-D NMR techniques such as ROESY. The switching between the open and closed states is described. Whereas for the Pd(ii) complex, the handle freely rotates around the stator, for the Zn(ii) analogue owing to the presence of a water molecule bound to the zinc atom and hydrogen bonded to the pyridyl moiety of the rotor, the rotation is blocked. The unlocking of the rotational movement was achieved using an external agent, mainly dimethylaminopyridine as a strong coordinating ligand.

Full text of DOI:10.1039/c2nj40657h

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PAPER
Zinc– and palladium–porphyrin based turnstileswz
Thomas Lang, Ernest Graf,* Nathalie Kyritsakas and Mir Wais Hosseini*
Received (in Montpellier, France) 27th July 2012, Accepted 17th September 2012
DOI: 10.1039/c2nj40657h
The design and synthesis of two new Zn(II) and Pd(II) strapped-porphyrin based molecular
turnstiles have been achieved. These molecules are based on a porphyrin backbone as a stator and
a handle as a rotor. The junction between the two parts is ensured by covalent bonds using two
opposite meso positions. Both compounds have been characterised in solution by NMR
spectroscopy and in the solid state by X-ray diffraction on a single crystal. The dynamic of the
two systems have been investigated in solution by 1- and 2-D NMR techniques such as ROESY.
The switching between the open and closed states is described. Whereas for the Pd(II) complex,
the handle freely rotates around the stator, for the Zn(II) analogue owing to the presence of a
water molecule bound to the zinc atom and hydrogen bonded to the pyridyl moiety of the rotor,
the rotation is blocked. The unlocking of the rotational movement was achieved using an external
agent, mainly dimethylaminopyridine as a strong coordinating ligand.
Introduction
Results and discussion
The design and synthesis of molecular architectures for which
intramolecular movements can be controlled by external sti-
muli are a topic of interest (for review articles see ref. 1–8).
Many examples of rotaxanes9 and catenanes10 based systems
have been reported. Molecular motors functioning with
thermal11 or photochemical12 processes have been published.
Molecular cars13 and wheelbarrows14 have also been
described. Among the above-mentioned systems, molecular
turnstiles15 form a class of dynamic architectures subject to
rotational processes between a fixed (stator) and a mobile
(rotor) part. For this type of molecules, the switching
between an open and a closed state by an external stimulus
is challenging and of interest. We have previously reported
examples of turnstiles based either on Sn–porphyrin deriva-
tives16,17 or on a strapped-porphyrin for which the rotor
comprises a tridentate unit.18
The turnstile reported here is the strapped porphyrin 1
(Scheme 1). Its design is based on a meso tetraaryl porphyrin
as a stator and a strap as a rotor. It should be noted that the
designation of the two parts as a stator and as a rotor is
arbitrary and the rotational process is a relative movement of
one of the two parts around the other. The rational behind the
choice of the porphyrin backbone is based on its propensity to
bind a large variety of metal centres by its tetraaza macrocyclic
core and on available synthetic possibilities to incorporate the
strap. Examples of strapped porphyrins bearing a phenanthroline
Here, we report on the design, synthesis, characterization,
both in solution and in the crystalline phase, and on the
switching between the open and closed states of molecular
turnstiles based on strapped-porphyrins19 composed of a free
base meso tetraaryl porphyrin and its zinc20 or palladium
complexes and a covalently attached handle bearing a pyridyl
moiety as a monodentate coordinating site.
´
UMR UDS-CNRS 7140, Universite de Strasbourg, Institut Le Bel,
4 rue Blaise Pascal, CS90032 67081 Strasbourg, France.
E-mail: hosseini@unistra.fr, egraf@unistra
w This article is included in the All Aboard 2013 themed issue.
z CCDC 894032 and 894033. For crystallographic data in CIF or
other electronic format see DOI: 10.1039/c2nj40657h
Scheme 1 Strapped porphyrin 1, its Zn(II) and Pd(II) complexes 2 and
3 respectively, and the water complex 2ꢀH2O and the assignment of
H atoms.
c
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unit as a handle have been reported.21 The rotor is a mono-
dentate pyridyl coordinating unit bearing, in a symmetrical
fashion, two tetraethyleneglycol moieties at positions 2 and 6.
The pyridyl unit and the spacer are interconnected using ether
junctions. The connection between the porphyrin and the strap
is ensured by two covalent ether groups using the two meso
positions 5 and 15 on the porphyrin. For the attachment of the
handle to the aryl groups of the porphyrin, one may use the
ortho, meta or para position. In order to avoid (i) a rotational
barrier induced by the use of the ortho position, (ii) longer
spacer units between the porphyrin backbone and the pyridyl
moiety resulting from the improper angle imposed by the use
of the para position, the junction is achieved in a symmetrical
fashion using the meta position on both aryl groups in
positions 5 and 15. The remaining two meso positions 10
and 20 are occupied by two benzonitrile groups connected to
the porphyrin backbone using the position 4 of the aryl
moiety. The nitrile groups at the meso positions were intro-
duced as additional coordinating sites in order to explore the
possibility of locking the system by simultaneous binding of
external metal cations by both the peripheral site and the
pyridyl moiety of the handle. Their presence does not interfere
with the present study.
Scheme 2
The operational design of the turnstile (Fig. 1) is based on:
(i) free rotation (open state, Fig. 1a) of the rotor around the
stator as a consequence of the absence of specific interactions
between the two parts, (ii) introduction of the Zn(II) cation
within the macrocyclic coordinating moiety of the strapped
porphyrin 1 (Fig. 1b) affording the neutral complex 2
(Scheme 1). Owing to the propensity of Zn2+ cation to adopt
mainly a square based pyramidal geometry when complexed
by the tetraaza core of the porphyrin, the coordination of the
pyridyl unit of the rotor should lock the rotation process
leading thus to the closed state of the turnstile (Fig. 1b). In
order to prove the latter statement, the Zn2+ cation may be
replaced by Pd(II) (complex 3, Scheme 1) adopting the square
planar geometry without extension of its coordination sphere.
In that case, the locking process cannot take place and thus the
rotation of the rotor around the stator should not be altered
(Fig. 1c).
upon treatment with dihydropyrane (DHP) in CHCl3 (34%
yield). The latter was then condensed in the presence of NaH
in refluxing THF with the dichloro compound 724 affording
the compound 825 in 54% yield. Compound 7 was prepared in
82% yield in THF at room temperature upon treatment of 6
with SOCl2. The bis-OTHP derivative 8 was then deprotected
under acidic conditions affording the diol 9 in 88% yield. The
latter was quantitatively activated into its dimesylate
derivative 10. The handle 11 was obtained in the presence of
potassium carbonate in 96% yield in refluxing CH3CN upon
reaction with 3-hydroxybenzaldehyde 14.
Dipyrrylmethane 1322 was obtained in 63% yield upon
reaction of the aldehyde 12 with pyrrole in the presence of
TFA. Condensation, in a CH2Cl2–EtOH mixture and in the
presence of TFA, of the dialdehyde 11 with dipyrrylmethane
13 followed by oxidation in THF and in the presence of Et3N
using DDQ,26 afforded strapped-porphyrin 1 in 2% yield.
In order to increase the yield of the final step, another
synthetic strategy was explored. The compound 11 was con-
verted in 66% into its bisdipyrrylmethane derivative 15 by
reaction with an excess of pyrrole in the presence of TFA.
Unfortunately, this strategy did not enhance the yield of the
porphyrin formation. Indeed, the condensation of 15 in the
presence of TFA with the aldehyde 12 in a CH2Cl2–EtOH
mixture followed by oxidation using DDQ26 in the presence of
Et3N in THF afforded the porphyrin derivative 1 in 1% yield.
The Zn–porphyrin complex 2 was quantitatively obtained in
a CH2Cl2–MeOH mixture and at room temperature, upon
treatment of 1 with Zn(OAc)2. The Pd–porphyrin complex 3
was obtained in 66% yield in a refluxing CHCl3–MeOH
mixture, upon addition of Pd(OAc)2 to a solution of the
porphyrin 1.
The synthetic strategy adopted for the preparation of the
strapped porphyrin 1 (Scheme 2) was based on the condensa-
tion of the dipyrrylmethane 1322 and the a, o dialdehyde 11.
The latter was prepared from the commercially available
3-hydroxybenzaldehyde 14, tetraethyleneglycol 4 and 2,6-pyr-
idine diol 6.
Compound 4 was first converted at room temperature in the
presence of a catalytic amount of pyridinium para-toluenesul-
fonate (PPTS) into its mono-DHP protected derivative 523
The assignment of all hydrogen atoms of the strapped
porphyrins 1–3 was achieved at 25 1C in CD2Cl2 by 1- and
2-D NMR COSY and ROESY experiments. Using the same
Fig. 1 Schematic representation of strapped-porphyrins: (a) free base
(open state), (b) Zn–porphyrin (closed state), (c) Pd–porphyrin (open
state).
c
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technique, the dynamics of compounds 1–3 in solution
(CD2Cl2) was also studied at 25 1C.
For both porphyrins 1 and 3, a splitting of hydrogen atoms
For the Zn–porphyrin turnstile 2, the C2v symmetry of the
1
molecule is conserved. The H-NMR investigations revealed,
as expected, a drastic upfield shift of Hu and Hv atoms by
1.32 ppm and 0.53 ppm, respectively, implying the locking of
the handle and the positioning of this portion of the handle
within the anisotropic cone of the porphyrin backbone. The
0
of the benzonitrile moieties Ha, and Hb into Ha, Ha , and Hb,
Hb (Scheme 1) was observed. This differentiation, resulting
from the slow rotation of the handle around the porphyrin
core within the NMR time scale, is in agreement with a
previous study performed on an analogue system.18 The
binding of the Pd(II) cation by the tetraaza core of the
porphyrin has almost no influence on the H atoms of the
handle. Indeed, when compared to the parent compound 1,
signals corresponding to Hr and Hs of the pyridyl unit are only
slightly shifted by 0.03 ppm and 0.06 ppm respectively. The
same observation holds for Hu and Hv atoms belonging to the
tetraethyleneglycol units which are shifted by 0.08 ppm and
0.04 ppm, respectively (Fig. 2a and c). These observations
indicate the free rotation of the handle around the porphyrin
stator defining thus the open state of the turnstile.
0
observed splitting increase between Hb and Hb signals is
another argument in favour of a blocked rotation. However,
the pyridine Hr and Hs hydrogen atoms were found to be
downfield shifted by 0.35 ppm and 0.85 ppm, respectively
(Fig. 2b). This observation is not in agreement with a direct
binding of the Zn(II) cation located within the centre of the
porphyrin stator by the N atom of the pyridyl unit of the
handle. Indeed, if this was the case, one would expect upfield
shifts of Hr and Hs signals. Thus, the closed state of the
turnstile must result from an indirect interaction between the
handle and the stator. The 2-D ROESY sequence at room
temperature revealed, in addition to the expected correlations
between Hk and Hj and Hg, as also observed for 1 (Fig. 3a) and
3 (Fig. 3b), new correlations between Hg of the meso aromatic
groups and Hu, Hv and Hq belonging to the handle (Fig. 3c).
Furthermore, it also revealed the presence of correlations
between Hu, Hv and Hq and a water molecule (Fig. 3d). This
observation is consistent with the coordination of a water
molecule by the Zn cation and interacting with the handle
through a H-bond with the pyridyl moiety affording the
complex 2ꢀH2O (Scheme 1). This proposal also explains why
the proton signals of Hr and Hs of the pyridyl unit are slightly
downfield shifted. This hypothesis is substantiated in the
crystalline phase by the structural investigation on a single
crystal presented hereafter.
This statement was further confirmed by a 2-D ROESY
experiment at room temperature which revealed only the
expected correlations between Hk and Hj and Hg due to spatial
proximities resulting from the atomic connectivity in the free
strapped porphyrin 1 and its Pd complex 3 (Fig. 3a and b).
The solid state structures of both compound 2 and 3 were
studied by X-ray diffraction on single crystals obtained upon
slow diffusion of pentane into a CH2Cl2 solution of 2 (Fig. 4)
or 3 (Fig. 5).
Fig. 2 A portion (2.1–9.1 ppm) of the 1H-NMR spectra (CD2Cl2,
400 MHz, 25 1C) of 1 (a), 2 (b) and 3 (c). * and ¤ correspond to
residual CHCl3 and MeOH, respectively. For assignment of H atoms
see Scheme 1.
For the Zn–porphyrin 2ꢀH2O complex, the structural study
%
revealed that the crystal (triclinic, P1) in addition to the
complex 2 contains water and dichloromethane molecules
(Fig. 4). No noticeable deformation of the porphyrin
backbone is observed. The zinc cation is located above the
porphyrin mean plane (0.441 A). The coordination geometry
around the metallic centre is a slightly distorted square based
pyramid. Its coordination sphere is composed of all four
N atoms of the porphyrin core with Zn–N distances in the
Fig. 4 Solid state structure of compound 2ꢀH2O. One of the two
tetraethyleneglycol units connecting the handle to the porphyrin is
found to be disordered. Hydrogen atoms and solvent molecules are
omitted for clarity. For bond distances and angles, see text.
Fig. 3 Portions of the 2-D ROESY correlations for 1 (a), 3 (b) and 2
(c and d). * and ¤ correspond to residual chloroform and methanol,
respectively. For attribution of H atoms see Scheme 1.
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Fig. 5 Solid state structure of compound 3. Hydrogen atoms and
solvent molecules are omitted for clarity. One of the ethyleneglycol
units is found to be disordered. For bond distances and angles, see
text.
Fig. 6 Portion of the 1H NMR spectra (CD2Cl2, 300 MHz, 25 1C) of
2ꢀH2O (a) in the presence of 0 eq. (a), 1 eq. (b) and 2 eq. (c) of DMAP
and of the parent compound 1 (d). * corresponds to signals of
coordinated DMAP. For assignment of H atoms see Scheme 1.
2.063(3)–2.083(3)
A
range and N–Zn–N angles of
160.02(12)–160.97(12)1 (N–Zn–Ntrans), 87.67(11)–89.05(11)1
(N–Zn–Ncis). The water molecule occupies the apical
position with the Zn–O distance of 2.120(3) A and N–Zn–O
angles of 98.53(11)–100.49(11)1. The four meso substituents
are not coplanar but tilted with respect to the porphyrin mean
plane with CCCC dihedral angles of ꢁ67.51 and ꢁ71.21 for the
aryl units of the bridging handle and of ꢁ80.21 and 59.71 for
the benzonitrile groups. One of the two tetraethyleneglycol
units connecting the handle to the porphyrin is found to be
disordered. Interestingly, the water molecule is hydrogen
bonded to the pyridine nitrogen atoms of the handle with a
O–N bond distance of 2.915(4) A and NHO angles of 165(4)1.
signals appeared to be broadened. However, for the 1/1 mixture
of DMAP/2, in agreement with the coordination of DMAP to
the Zn cation, the signal corresponding to the CH3 groups was
found to be upfield shifted by 0.53 ppm. Upon increasing the
DMAP/2 ratio from 1 to 10, all signals of DMAP became
narrower and downfield shifted.
Conclusion
In conclusion, a new strapped-porphyrin based molecular
turnstile was designed, synthesized and characterised both in
solution and in the solid state. The turnstile is composed of a
porphyrin backbone (stator) equipped with a handle bearing a
pyridyl unit as a monodentate coordinating site (rotor). In the
absence of Zn(II) cation within the tetraaza core of the
porphyrin, the rotor freely rotates around the stator (open
state). In the presence of Pd(II) within the porphyrin core and
adopting a square planar geometry, again the free rotation of
the rotor around the stator is observed. In the presence
of Zn(II), adopting a square based pyramidal geometry, in
contrast with the initial design based on direct coordination of
Zn cation by the pyridyl unit, the rotation was found to be
locked (closed state) owing to the formation of a H-bond
between a water molecule coordinated to the metal centre and
the pyridyl moiety of the handle. The addition of DMAP, a
competitive ligand, to the turnstile in its closed state leads to the
open state of the turnstile. The use of rotors bearing tridentate
binding site and other metal centres either bound to the
porphyrin and/or to the rotor is currently under investigation.
Furthermore, taking advantage of the presence of the peripheral
nitrile coordinating sites, the locking of the turnstile using
additional metal centres is also currently explored.
%
For the Pd–porphyrin complex 3, the crystal (triclinic, P1) is
composed of the porphyrin 3, pentane and H2O solvent
molecules (Fig. 5). The latter occupy in the crystal the empty
space between compounds 3 without any specific interactions.
The porphyrin backbone is not distorted. The palladium
cation, located almost in the centre of the porphyrin core, is
tetracoordinated. The coordination geometry around the
metallic centre is almost square planar with Pd–N distances
in the 1.995(9)–2.024(10) A range and N–Pd–N angles of
178.3(4)–178.6(4)1 (N–Pd–Ntrans), 89.7(4)–90.6(4)1 (N–Pd–
N
cis). The meso substituents are tilted with respect to the
porphyrin mean plane with CCCC dihedral angle of ꢁ65.61
and ꢁ57.61 for the aryl units of the bridging handle and
ꢁ75.01 and 61.01 for the benzonitrile groups. One of the
glycol units is found to be disordered over two positions.
In order to unlock the turnstile, 1–10 equivalents of para-
dimethylaminopyridine (DMAP), a competitive ligand, was
added to 2 and the process monitored by 1H-NMR in CD2Cl2
at 25 1C (Fig. 6). As expected, upon addition of one equivalent
of DMAP (Fig. 6b), the open state of the turnstile was
restored. Indeed, by considering the ‘‘free-base’’ strapped-
porphyrin 1 as a reference (Fig. 6d), the presence of DMAP
caused a shift of all proton signals towards those observed for 1.
In particular, Hr and Hs hydrogen atoms of the pyridyl moiety
were upfield shifted by 0.16 ppm and 0.65 ppm respectively,
whereas Hu and Hv signals were downfield shifted by 1.30 ppm
Experimental
General procedure
0
and 0.55 ppm respectively. Furthermore, Hb and Hb signals
were found to be less differentiated. Upon further addition of
DMAP, no additional shift of signals of the turnstile was
observed (see Fig. 6c for addition of 2 eq. of DMAP).
Dealing with DMAP, due to the fast exchange dynamics, its
THF and triethylamine were distilled over sodium and KOH,
respectively. Analytical grade of CH2Cl2, CHCl3, EtOH and
MeOH was used without further purification. 1H- and 13C-NMR
spectra were acquired at 25 1C on either a Bruker AV 300,
c
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Bruker AV 400 or a Brucker AV 500 spectrometers. Deuterated
solvents were used as the lock and residual non deuterated
solvents as the internal references. Mass spectrometry analyses
were performed by the Service de Spectrometrie de Masse,
University of Strasbourg.
Method B. In a 100 mL two-necked round-bottom flask,
compound 15 (900 mg, 970 mmol, 1 eq.) and 4-cyanobenzal-
dehyde 12 (253 mg, 1.9 mmol, 2 eq.) were dissolved in 25 mL
of a CH2Cl2–EtOH (4/1) mixture. The solution was degassed
under argon for 15 min before TFA (215 mL, 2.9 mmol, 3 eq.)
was added. The reaction mixture was stirred under argon at
room temperature for 20 hours. Triethylamine (540 mL,
3.9 mmol, 4 eq.) was added to neutralize TFA and then, a
solution of DDQ (330 mg, 1.5 mmol, 1.5 eq.) in 10 mL of THF
was added and the reaction mixture was stirred at room
temperature for 16 hours. After removal of solvents, the
crude product was purified by chromatography (SiO2,
CH2Cl2–MeOH 1/0 to 97/3) affording the compound 1 in
1% yield (15 mg) as a purple solid.
X-ray crystal-structure analysis
Data were collected on a Bruker APEX8 CCD diffractometer
equipped with an Oxford Cryosystem liquid N2 device at
173(2) K using a molybdenum microfocus sealed tube
generator with mirror-monochromated Mo-Ka radiation
(l = 0.71073 A), operated at 50 kV/600 mA. The structure
was solved using SHELXS-97 and refined by fullmatrix least-
squares on F2 using SHELXL-97 with anisotropic thermal
parameters for all non-hydrogen atoms.27 The hydrogen
atoms were introduced at calculated positions and not
refined (riding model).
1H-NMR (CD2Cl2, 400 MHz) d (ppm): ꢁ2.94 (s, 2H, NHy),
2.88 (m, 4H, OCH2v), 3.00 (m, 4H, OCH2q), 3.14 (m, 4H,
OCH2p), 3.34 (m, 4H, OCH2o), 3.51 (m, 4H, OCH2n), 3.57 (s,
4H, OCH2u), 3.64 (m, 4H, OCH2m), 3.89 (m, 4H, OCH2l), 4.31
Crystals of 2 and 3 were obtained in a crystallization tube
(0.5 ꢂ 20 cm) at room temperature upon slow diffusion of
pentane into a solution of the complex in CH2Cl2 through a
buffer layer of pentane/CH2Cl2 (1/1).
3
(m, 4H, OCH2k), 6.15 (d, 2H, Pyr, J = 7.5 Hz), 6.46 (t, 1H,
Pys, 3J = 7.5 Hz), 7.36 (dd, 2H, Arj, 3J = 8.5 Hz, 4J =
2.0 Hz), 7.69 (t, 2H, Ari, 3J = 8.0 Hz), 7.76 (m, 2H, Arg), 7.88
(d, 2H, Arh, 3J = 7.5 Hz), 8.08 (d, 4H, Ara, 3J = 8.5 Hz), 8.33
Crystallographic data for 2: C138.5H131ClN14O23Zn2, M =
%
2525.81, triclinic, P1, a = 13.5277(4) A, b = 15.3111(7) A,
3
(m, 4H, Arb), 8.76 (d, 4H, b-pyrc, J = 4.5 Hz), 8.94 (d, 4H,
b-pyrd, 3J = 4.5 Hz). 13C-NMR (CD2Cl2, 100 MHz) d (ppm):
68.0, 69.7, 69.9, 70.0, 70.4, 70.5, 70.7, 71.0, 73.3, 112.0, 114.5,
119.1, 119.2, 120.7, 122.2, 127.7, 128.0, 130.7, 131.1, 132.3,
135.4, 136.3, 143.1, 147.0, 157.1, 157.7. MS (ESI) for
C69H65N7O10: 1152.30 g molꢁ1. m/z (M + Na+): calculated
= 1174.469; measured = 1174.497.
c = 17.7296(5) A, a = 86.083(3)1, b = 67.796(2)1, g =
77.863(3)1, U = 3323.7(2) A3, Z = 1, m = 0.454 mmꢁ1
,
refls measured: 34 801, independent refls: 14 673 [Rint
=
=
0.0240], final R indices [I 4 2s (I)]: R1 = 0.0782, wR2
0.2357, R indices (all data): R1 = 0.0969, wR2 = 0.2528, GOF
on F2: 1.063.
Crystallographic data for 3: C148H156N14O23Pd2, M =
%
2711.67, triclinic, P1, a = 14.8196(12) A, b = 17.1292(15) A,
Compound 2. In a 10 mL round-bottom flask, to a CH2Cl2
solution (3 mL) of compound 1 (9 mg, 7.8 mmol, 1 eq.) a
MeOH solution (3 mL) of zinc acetate (171 mg, 780 mmol,
100 eq.) was added. The reaction mixture was stirred at room
temperature for 2 hours. The mixture was successively washed
with water (3 ꢂ 10 mL) and a 10% aqueous solution of
NaHCO3 (3 ꢂ 10 mL). The organic phase was dried over
MgSO4 and the solvent removed under vacuum. The mixture
was dissolved in CH2Cl2 (5 mL) and the compound 2 was
quantitatively precipitated upon addition of pentane affording
after filtration 9.5 mg of a purple powder.
c = 17.1532(17) A, a = 63.953(3)1, b = 84.648(3)1, g =
64.883(3)1, U = 3518.9(5) A3, Z = 1, m = 0.328 mmꢁ1, refls
measured: 12 750, independent refls: 11654 [Rint = 0.0378], final
R indices [I 4 2s (I)]: R1 = 0.1132, wR2 = 0.2997, R indices
(all data): R1 = 0.1510, wR2 = 0.3255, GOF on F2: 1.416.
Owing to the weak diffraction power of the crystal, the data
collection was performed with a theta value of 251.
Synthesis
1H-NMR (CD2Cl2, 400 MHz) d (ppm): 2.25 (s, 4H,
OCH2u), 2.35 (m, 4H, OCH2v), 2.79 (m, 4H, OCH2p), 2.81
(m, 4H, OCH2q), 3.13 (m, 4H, OCH2o), 3.49 (m, 4H, OCH2n),
3.65 (m, 4H, OCH2m), 3.89 (m, 4H, OCH2l), 4.32 (m, 4H,
OCH2k), 6.50 (d, 2H, Pyr, 3J = 7.5 Hz), 7.31 (m, 3H, Pys, Arj),
7.62 (t, 2H, Ari, 3J = 8.0 Hz), 7.68 (br, 2H, Arg), 7.77 (d, 2H,
Arh, 3J = 7.5 Hz), 8.02 (m, 6H, Ara,b), 8.29 (d, 2H, Arb, 3J =
8.0 Hz), 8.77 (d, 4H, b-pyrc, 3J = 4.5 Hz), 8.95 (d, 4H, b-pyrd,
3J = 4.5 Hz). 13C-NMR (CD2Cl2, 100 MHz) d (ppm): 68.6,
69.3, 69.6, 69.6, 70.0, 70.5, 70.6, 70.9, 71.0, 111.5, 114.4, 118.7,
119.5, 120.0, 121.1, 122.6, 127.6, 128.1, 130.5, 131.5, 132.8,
135.0, 135.4, 137.8, 144.4, 148.3, 149.6, 150.5, 156.3, 157.5.MS
(ESI) for C69H63N7O10Zn: 1215.66 g molꢁ1. m/z (M + Na+):
calculated = 1236.382; measured = 1236.400.
Compounds 724 and 1322 have been prepared following
reported procedures.
Compound 1: Method A. In a 500 mL two-necked round-
bottom flask, dipyrrylmethane 13 (371 mg, 1.5 mmol, 1 eq.)
and compound 11 (1.05 g, 1.5 mmol, 1 eq.) were dissolved in
200 mL of a CH2Cl2–EtOH (95/5) mixture. The solution was
degassed under argon for 30 min before TFA (335 mL,
4.5 mmol, 3 eq.) was added. The reaction mixture was
stirred under argon at room temperature for 5 days. TFA
was neutralized by triethylamine (840 mL, 6 mmol, 4 eq.)
before a solution of DDQ (511 mg, 2.3 mmol, 1.5 eq.) in
50 mL of THF was added and the reaction mixture was further
stirred at room temperature for 16 hours. Solvents were
removed under vacuum and the crude product was purified
by chromatography (SiO2, CH2Cl2–MeOH 100/0 to 98/2) to
afford the compound 1 (34 mg, 2%) as a purple solid.
Compound 3. In a 50 mL round-bottom flask, to a solution
of the compound 1 (8.8 mg, 7.6 mmol, 1 eq.) dissolved in 20 mL
of a CHCl3–MeOH (95/5) mixture, a CHCl3 solution (5 mL)
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of palladium acetate (2.6 mg, 11.4 mmol, 1.5 eq.) was added.
Under argon, the mixture was heated at reflux for 16 hours
before solvents were removed under vacuum. The crude
product was purified by column chromatography (SiO2,
CH2Cl2–MeOH, 1/0 to 95/5) affording the compound 3
(6.3 mg, 66%) as an orange solid.
70.8, 74.0, 99.1, 120.1, 137.5, 157.9. Anal.: calculated for
C33H57NO12: C = 60.07%; H = 8.71%; N = 2.12%;
found: C = 59.95%; H = 9.07%; N = 1.88%.
Compound 9. In a 1 L round-bottom flask, compound 8
(3.62 g, 5.5 mmol, 1 eq.) was dissolved in a mixture of MeOH
(450 mL) and concentrated HCl (3 mL) and stirred at room
temperature for 5 hours. To the mixture, solid NaHCO3 was
added to neutralize the excess of HCl. Solvents were removed
under vacuum affording a white solid which was washed with
Et2O (5 ꢂ 100 mL), filtered and dried under vacuum to yield
the compound 9 (2.37 g, 88%) as a pale yellow oil.
1H-NMR (CDCl3, 300 MHz) d (ppm): 2.83 (br, 2H, OH),
3.58–3.75 (m, 32H, OCH2k–v), 4.67 (s, 4H, OCH2u), 7.38
(d, 2H, Pyr, 3J = 8.0 Hz), 7.71 (t, 1H, Pys, 3J = 8.0 Hz).
13C-NMR (CDCl3, 75 MHz) d (ppm): 61.8, 70.4, 70.5, 70.7,
70.8, 72.7, 74.0, 120.2, 137.6, 157.9. Anal.: calculated for
C23H41NO10 0.5 C4H10O: C = 56.80%; H = 8.77%; N =
2.65%; found: C = 56.79%; H = 8.70%; N = 2.62%.
1H-NMR (CD2Cl2, 400 MHz) d (ppm): 2.92 (m, 4H,
OCH2v), 3.07 (m, 4H, OCH2), 3.20 (m, 4H, OCH2p), 3.37
(m, 4H, OCH2o), 3.53 (m, 4H, OCH2n), 3.65 (m, 8H,
OCH2u,m), 3.89 (m, 4H, OCH2l), 4.30 (m, 4H, OCH2k), 6.18
(d, 2H, Pyr, 3J = 7.5 Hz), 6.52 (t, 1H, Pys, 3J = 7.5 Hz), 7.35
3
4
(dd, 2H, Arj, J = 8.0 Hz, J = 2.0 Hz), 7.68 (m, 4H, Arg,i),
7.82 (d, 2H, Arh, 3J = 7.5 Hz), 8.07 (m, 4H, Ara), 8.26 (m, 2H,
Arb), 8.32 (m, 2H, Arb), 8.72 (d, 4H, b-pyrc, 3J = 5.0 Hz), 8.91
(d, 4H, b-pyrd, 3J = 5.0 Hz). 13C-NMR (CDCl3, 125 MHz) d
(ppm): 68.0, 69.7, 69.8, 70.0, 70.3, 70.5, 70.7, 70.9, 73.2, 111.5,
114.9, 118.5, 119.2, 119.2, 121.2, 121.5, 127.6, 128.0, 130.8,
130.9, 132.2, 134.7, 136.6, 140.8, 141.0, 142.2, 146.2, 156.5,
157.1. MS (ESI) for C69H63N7O10Pd: 1255.37 g molꢁ1. m/z
(M + Na+): calculated = 1278.359; measured = 1278.358.
Compound 10. In a dry 250 mL two-necked round-bottom
flask, compound 9 (2.37 g, 4.8 mmol, 1 eq.) was dissolved in
100 mL of dry THF. Under argon, freshly distilled Et3N
(2.3 mL, 16 mmol, 3.4 eq.) and mesyl chloride (1.1 mL,
15 mmol, 3 eq.) were added and the reaction mixture stirred
at room temperature for 5 hours. After removal of the solvent,
the white solid was dissolved in CH2Cl2 (100 mL), washed with
water (3 ꢂ 75 mL) and a 5% solution of NaHCO3 (3 ꢂ
75 mL). The organic layer was dried over MgSO4, filtered and
solvent removed under vacuum to yield quantitatively the
compound 10 (3.11 g) as a yellow oil.
Compound 5. In a 2 L two-necked round-bottom flask,
tetraethyleneglycol 4 (37 mL, 216 mmol, 3 eq.) and pyridinium
para-toluenesulfonate (1.8 g, 7.2 mmol, 0.1 eq.) were dissolved
in 1 L of analytical grade CHCl3. Then, under argon, a
solution of DHP (6.6 mL, 72 mmol, 1 eq.) in 300 mL of
analytical grade CHCl3 was added dropwise. The reaction
mixture was stirred at room temperature for 2 days. The
organic layer was washed with a 10% solution of K2CO3
(4 ꢂ 400 mL) and brine (400 mL) and dried over MgSO4. The
solvent was removed and the residue dried under vacuum
overnight to yield the compound 5 (6.8 g, 34%) as a yellow oil.
1H-NMR (CDCl3, 300 MHz) d (ppm): 1.38–1.85 (m, 6H,
CH2(THP)), 2.83 (br, 1H, OH), 3.40–3.85 (m, 18H, OCH2,
OCH2(THP)), 4.58 (m, 1H, CH(THP)). 13C-NMR (CDCl3, 75
MHz) d (ppm): 19.6, 25.6, 30.7, 61.7, 62.4, 66.8, 70.1, 70.7,
70.8, 73.1, 99.1. Anal.: calculated for C13H26O6: C = 56.10%;
H = 9.42%; found: C = 56.53%; H = 9.23%.
1H-NMR (CDCl3, 300 MHz) d (ppm): 3.06 (s, 6H, CH3),
3.62–3.77 (m, 28H, OCH2v–l), 4.36 (m, 4H, OCH2k), 4.68
3
(s, 4H, OCH2u), 7.39 (d, 2H, Pyr, J = 8.0 Hz), 7.73 (t, 1H,
Pys, 3J = 8.0 Hz). 13C-NMR (CDCl3, 75 MHz) d (ppm): 37.9,
69.1, 69.4, 70.4, 70.7, 70.8, 73.9, 120.3, 137.8, 157.8. Anal.:
calculated for C25H45NO14S2: C = 46.36%; H = 7.00%; N =
2.16%; found: C = 46.35%; H = 6.87%; N = 2.05%.
Compound 8. In a dry 500 mL two-necked round-bottom
flask, sodium hydride (60% in oil) (900 mg, 22 mmol, 2.2 eq.)
was suspended at 0 1C in 150 mL of dry THF. A solution of
compound 5 (6.26 g, 22 mmol, 2.2 eq.) in dry THF (50 mL)
was added dropwise at 0 1C and the reaction mixture was
stirred at room temperature for 40 min. Then, a solution of
compound 7 (1.81 g, 10 mmol, 1 eq.) in dry THF (90 mL) was
added dropwise. The reaction mixture was heated at reflux for
5 days. The solvent was removed and the brown oily residue
was dissolved in CHCl3 and washed with water (4 ꢂ 100 mL)
and brine (2 ꢂ 100 mL), dried over MgSO4 and the solvent
removed under reduced pressure. The crude orange oil was
purified by chromatography (Al2O3, cyclohexane–ethyl
acetate 1/1 to 0/1) to yield the compound 8 (3.62 g, 54%) as
a yellow oil.
Compound 11
In a 500 mL two-necked round-bottom flask, 3-hydroxyben-
zaldehyde 14 (2.35 g, 19 mmol, 4 eq.) was dissolved in 200 mL
of dry CH3CN. K2CO3 (2.65 g, 19 mmol, 4 eq.) was added and
the reaction mixture stirred under argon at room temperature
for 2 hours. A solution of compound 10 (3.11 g, 4.8 mmol,
1 eq.) in 100 mL of dry CH3CN was added via cannula. The
reaction mixture was heated at reflux for 16 hours. The solvent
was removed under vacuum and the oily residue was dissolved
in CH2Cl2 (300 mL), washed with water (2 ꢂ 150 mL) and
successively with solutions of NaOH (0.1 M, 150 mL), HCl
(0.1 M, 150 mL) and brine (150 mL). The organic layer was
dried over MgSO4 and the solvent removed under vacuum to
yield the compound 11 (3.22 g, 96%) as a brown oil.
1H-NMR (CDCl3, 300 MHz) d (ppm): 1.47–1.87 (m, 12H,
CH2 (THP)), 3.45–3.90 (m, 36H, OCH2k–v, OCH2 (THP)), 4.62
(m, 2H, CH (THP)), 4.68 (s, 4H, OCH2u), 7.39 (d, 2H, Pyr, 3J =
1H-NMR (CDCl3, 300 MHz) d (ppm): 3.65–3.75 (m, 24H,
OCH2v–m), 3.87 (m, 4H, OCH2l), 4.18 (m, 4H, OCH2k), 4.67
(s, 4H, OCH2u), 7.19 (m, 2H, Ar), 7.35–7.44 (m, 8H, Ar, Pyr),
3
3
8.0 Hz), 7.72 (t, 1H, Pys, J = 8.0 Hz). 13C-NMR (CDCl3,
7.69 (t, 1H, Pys, J = 8.0 Hz), 9.95 (s, 2H, CHO). 13C-NMR
75 MHz) d (ppm): 19.6, 25.6, 30.7, 62.4, 66.8, 70.4, 70.7, 70.8,
(CDCl3, 75 MHz) d (ppm): 67.9, 69.7, 70.4, 70.7, 70.8, 71.0,
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74.0, 113.1, 120.1, 122.2, 123.7, 130.2, 137.9, 157.9,
159.5, 192.2.
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P. Gavina, M. C. Jimenez-Molero and J.-P. Sauvage, Acc. Chem.
Res., 2001, 34, 477.
Compound 15. In a 50 mL two-necked round-bottom flask,
in exclusion of light, a mixture of the compound 11 (2.88 g,
4.4 mmol, 1 eq.) and pyrrole (15 mL, 220 mmol, 50 eq.) was
degassed under argon for 15 min before TFA (130 mL,
0.4 mmol, 0.1 eq.) was added and the reaction mixture stirred
at room temperature for 40 min. Excess pyrrole was removed
under vacuum and the crude product was purified by chromato-
graphy (Al2O3, petroleum ether–ethyl acetate 1/1 to 0/1) to
yield the compound 15 (2.7 g, 66%) as a brown oil.
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1H-NMR (CDCl3, 300 MHz) d (ppm): 3.65 (m, 24H,
OCH2v–m), 3.79 (m, 4H, OCH2l), 4.03 (m, 4H, OCH2k), 4.62
(s, 4H, OCH2u), 5.41 (s, 2H, CH), 5.90 (m, 4H, pyr.), 6.12
3
(q, 4H, pyr., J = 3.0 Hz), 6.66 (m, 4H, pyr.), 6.77 (m, 6H,
Ar), 7.18 (dd, 2H, Ar, 3J = 9.0 Hz, 3J = 7.5 Hz), 7.35 (d, 2H,
Pyr, 3J = 7.5 Hz), 7.69 (t, 1H, Pys, 3J = 7.5 Hz), 8.15 (br, 4H,
NH). 13C-NMR (CDCl3, 75 MHz) d (ppm): 44.1, 67.4, 69.9,
70.4, 70.6, 70.8, 70.9, 107.2, 108.4, 112.9, 115.2, 117.3, 120.3,
121.2, 129.7, 132.5, 143.9, 157.7, 159.1.
Acknowledgements
We thank the University of Strasbourg, the International
Centre for Frontier Research in Chemistry (FRC), Strasbourg,
the Institut Universitaire de France (IUF), the Ministry of
Education and Research and the CNRS for financial support.
Thanks to Dr L. Allouche for NMR studies.
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