Strapped-porphyrin-based molecular turnstiles

Article abstract of DOI:10.1002/chem.201200562

The synthesis of a series of molecular turnstiles that contained both H-bond-donor and -acceptor sites was achieved. Their structures were based on tetra-aryl X₂Sn^IV porphyrins (X=Cl or OH) as H-bond-acceptor sites that were equipped with a rotor that contained a pyridyldiamide moiety as a H-bond donor. In the solution phase, 1D and 2D NMR spectroscopic analysis showed that switching between the closed state, which resulted from the formation of intramolecular H-bonds, and the open state of the turnstile was achieved by using external H-bond-acceptor molecules, such as DMSO. The solid-state structure of the closed state of the turnstile was established by single-crystal X-ray diffraction. Re-turn to sender: Molecular turnstiles, which were based on strapped-type tetra-aryl X₂Sn ^IV porphyrins (X=Cl or OH) that contained both H-bond-donor and -acceptor sites, were prepared; switching between their open and closed states was studied in solution by 1D and 2D NMR spectroscopy. Copyright

Full text of DOI:10.1002/chem.201200562

FULL PAPER
DOI: 10.1002/chem.201200562
Strapped-Porphyrin-Based Molecular Turnstiles
Thomas Lang,[a] Ernest Graf,*[b] Nathalie Kyritsakas,[b] and Mir Wais Hosseini*[b]
Abstract: The synthesis of a series of
molecular turnstiles that contained
both H-bond-donor and -acceptor sites
was achieved. Their structures were
based on tetra-aryl X2SnIV porphyrins
(X=Cl or OH) as H-bond-acceptor
sites that were equipped with a rotor
that contained a pyridyldiamide moiety
as a H-bond donor. In the solution
phase, 1D and 2D NMR spectroscopic
analysis showed that switching between
the closed state, which resulted from
the formation of intramolecular H-
bonds, and the open state of the turn-
stile was achieved by using external H-
bond-acceptor molecules, such as
DMSO. The solid-state structure of the
closed state of the turnstile was estab-
lished by single-crystal X-ray diffrac-
tion.
Keywords: hydrogen bonds · mo-
lecular turnstiles · NMR spectrosco-
py · porphyrins · X-ray diffraction
Introduction
Controlling movement in molecular systems is a matter of
much current interest.[1–8] Among several approaches that
have been reported, the two that were based on rotaxanes[9]
and on catenanes[10] are particularly inspiring. Elegant exam-
ples of molecular motors that were based on thermal[11] or
photochemical[12] processes have been reported, whilst the
design of molecular cars,[13] wheelbarrows,[14] and turnstiles[15]
have also been published. We have previously reported the
synthesis of molecular gates[16] and turnstiles,[17] which were
based on Sn-porphyrin, derivatives that were composed of
a stator, a hinge, and a rotor.
Herein, we report the design and synthesis of strapped-
porphyrin-based molecular turnstiles in their closed (Fig-
ure 1b) and open states (Figure 1c) and the study of their
dynamics by using NMR spectroscopy.
A molecular turnstile may be defined as a two-component
system that is composed of a stator and a rotor as static and
mobile parts, respectively, that display intramolecular rota-
tional movement. Such movement is relative and thus one
may exchange the values of the two parts. For this type of
dynamic systems, the control of 1) movement and 2) direc-
tion are important considerations. For this first feature, im-
Figure 1. A strapped porphyrin (a) and a turnstile that contains both H-
bond-donor and -acceptor sites in its closed (b) and open states (c).
posing open and closed states with the possibility of switch-
ing between the two is of interest. The second aspect, that
is, control of the direction of the rotary movement, is rather
challenging and will not be discussed herein. To afford
a system that contains two distinct open and closed states, it
is compulsory to introduce specific reversible interactions,
such as H bonds or coordinate bonds between the stator and
the rotor.
Results and Discussion
Design of the system: For the design of molecular turnstiles,
the porphyrin backbone was a particularly interesting stator
for the following reasons: 1) by using two opposite meso po-
sitions, one may connect the rotor through robust covalent
bonds, thereby generating a strapped porphyrin[18] (Fig-
ure 1a); 2) by using the tetra-aza core, one may introduce
metal cations or metal complexes (Figure 1b) and thus set
up interactions between the stator and the rotor; 3) by using
the remaining two meso positions, one may equip the stator
with other interaction sites; 4) one may introduce a variety
of substituents onto the b-pyrrolic positions.
[a] Dr. T. Lang
Department of Chemistry
Chemistry Research Laboratory
University of Oxford, 12 Mansfield Road
Oxford, OX1 3TA (UK)
[b] Dr. E. Graf, N. Kyritsakas, Prof. Dr. M. W. Hosseini
Laboratoire de Chimie de Coordination Organique
UMR UdS-CNRS 7140
Institut Le Bel, Universitꢀ de Strasbourg
4 rue Blaise Pascal, CS 90032
67081 Strasbourg cedex (France)
Fax : (+33)368-85-13-25
Turnstiles 2 and 3 (Figure 2) were based on a meso-tetra-
arylporphyrin backbone that contained two benzonitrile
units on opposite meso positions and a rotor that was con-
E-mail: egraf@unistra.fr
hosseini@unistra.fr
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presence of hydrazine. More-
over, a pyridine diacid deriva-
tive (9) was converted into its
acyl chloride derivative (10)[22]
upon treatment with SOCl2 in
96% yield. Condensation of
compound 10 with compound 8
in the presence of triethylamine
afforded a,w-diol 11[23] in 96%
yield. The activation of the diol
into its dimesylate derivative
(12) was achieved in 92% yield
upon treatment with MsCl. The
desired compound (13) was ob-
tained in 62% yield upon con-
densation of dimesylate 12 with
3-hydroxybenzaldehyde (16) in
the presence of potassium car-
bonate in refluxing CH3CN. Di-
pyrromethane derivative 15 was
obtained from the reaction of
aldehyde 14 with pyrrole in the
presence of trifluoroacetic acid
(TFA) in 63% yield. Finally,
condensation of dialdehyde 13
with dipyrromethane derivative
15 in the presence of TFA in
CH2Cl2/EtOH, followed by oxi-
dation with DDQ[24] in THF, af-
forded the desired strapped
porphyrin (1) in 9% yield. The
formation of dichlorotin(IV)
Figure 2. Strapped porphyrins in their open (compounds 1 and 4) and closed states (compounds 2 and 3), to-
gether with the assignment of the H atoms.
complex
2 was achieved in
nected to the porphyrin through ether junctions by using the
remaining two meso positions. The two benzonitrile groups
were introduced for other purposes and their presence
didn’t interfere with the process described herein. The rotor
was symmetrical and was based on a 2,6-pyridyldiamide
moiety as a double-H-bond-donor site that was connected
to two tetraethyleneglycol spacers (Figure 2). To set up a hy-
drogen-bond-acceptor site, an X2SnIV moiety was introduced
within the tetra-aza core of the porphyrin, thereby affording
turnstiles 2 (X=Cl) and 3 (X=OH). For both compounds,
the closed and open states (4, X=Cl or X=OH) were stud-
ied in solution by using 1D and 2D NMR spectroscopy.
57% yield by treatment of compound 1 with SnCl2·2H2O in
pyridine.[25] Compound 1 was also converted into its dihy-
Synthesis of strapped porphyrins: Our synthetic strategy for
the preparation of strapped porphyrin 1 was based on the
condensation of dialdehyde 13 with functionalized dipyrro-
methane 15[19] (Scheme 1). The starting material for the syn-
thesis of compound 13 was tetraethyleneglycol 5, which was
transformed into its monotosylate derivative (6)[20] in 43%
yield upon treatment with TsCl in CH3CN in the presence
of triethylamine. The condensation of compound 6 with po-
tassium phthalimide at 1108C in DMF afforded compound 7
in 73% yield, which was subsequently transformed into
amino-derivative 8[21] in 90% yield by hydrazinolysis in the
Scheme 1. Intermediates used in the synthesis of compound 1.
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Strapped-Porphyrin-Based Molecular Turnstiles
FULL PAPER
droxy derivative (3) in 37% yield upon treatment with po-
tassium carbonate in CH2Cl2/MeOH followed by hydrolysis
on alumina.[26]
Structure and behavior of the strapped porphyrins: The
structure of compounds 1–3 was investigated in solution in
CD2Cl2, CD2Cl2/[D6]DMSO (9:1), and in pure [D6]DMSO
by using NMR spectroscopy. All hydrogen atoms were as-
signed by using 1D and 2D NMR techniques, such as COSY
and ROESY, at 208C (Figure 2).
At 258C, the 1H NMR spectrum of strapped porphyrin
1 in CD2Cl2 (Figure 3a) showed the presence of four dou-
blets, Ha, Ha’ and Hb, Hb’ (Figure 2), owing to the splitting
1
Figure 4. Region of the H NMR spectra (500 MHz, [D6]DMSO) of com-
pound 1 at 25 (a), 40 (b), 45 (c), 50 (d), 55 (e), 60 (f), 80 (g), and 1008C
(h).
Figure 3. 1H NMR spectra (500 MHz, 258C) of compounds 1 (a), 2 (b),
and 3 (c) in CD2Cl2 in the range d=5.75–9.45 ppm. 1H NMR spectra of
compound 3 in CD2Cl2/[D6]DMSO (9:1) (d) and pure [D6]DMSO (e).
For assignment of the H atoms, see Figure 2. The upfield shift of the NH
signal (t) was due to the shielding effect of the porphyrin ring.
of the H atoms on the benzonitrile moiety. Furthermore,
these signals appeared to be rather broad, thereby implying
a dynamic process. To investigate this process, we performed
a variable-temperature study in [D6]DMSO in the range 25–
1008C (Figure 4).
Figure 5. Region of the 2D ROESY correlations for compounds 1 (a), 2
(b), and 3 (c) in CD2Cl2. d) Region of the 2D ROESY correlations for
compound 3 in [D6]DMSO. For the assignment of the H atoms, see
Figure 2.
We found that, upon heating the solution in [D6]DMSO,
only two sharp doublets were observed, which corresponded
to protons Ha and Hb. The coalescence temperature for
proton Hb was about 558C, which corresponded to a rotation
rate of about 153 Hz, and an activation energy of about
67 kJ.
At room temperature, the 2D ROESY sequence only re-
vealed correlations between H atoms that were in close spa-
tial proximity to one another owing to the connectivity pat-
tern of the molecule (Figure 5a).
As expected from the design of dichloro-tin-strapped-por-
phyrin 2, the simultaneous presence of the pyridyldiamide
moiety on the handle, as a double-H-bond donor, and chlo-
ride anions, which were coordinated onto the SnIV cation
that was located in the center of the porphyrin backbone, as
H-bond acceptors led to the formation of CONH···Cl-type
H bonds, thereby affording the closed state of the turnstile.
The establishment of the H-bonds, which conserved the C2v
symmetry of the molecule, led to several characteristic fea-
tures. As expected, the 1H NMR spectrum (Figure 3b)
showed that the locking process led to a narrowing of the
signals that corresponded to the Ha, Ha’, Hb, and Hb’ pro-
tons. Furthermore, with respect to parent compound 1, a sig-
nificant upfield shift of about d=1.03 ppm was observed for
the NH (Ht) protons, as well as the reorganization of pro-
tons Hp, Hq, and Hv on the ethyleneglycol spacer. In addi-
tion, 2D ROESY measurements (CD2Cl2, 258C) revealed
new correlations (Figure 5b) between the Hg protons of the
meso-phenyl groups and the Hv atoms that were located on
the handle at the a position of the amide groups (for atom
labeling, see Figure 2).
The unlocking process that afforded the open state of
turnstile 2 (compound 4, X=Cl; Figure 2) was achieved by
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E. Graf, M. W. Hosseini et al.
using DMSO[27] as a H-bond-acceptor competitor. The pro-
cess was monitored by 1H NMR spectroscopy (Figure 6).
For turnstile 2, the locking process through the formation
of H bonds between the stator and the handle that had been
observed in CD2Cl2 was further confirmed in the crystalline
phase by using X-ray diffraction on a single crystal that was
obtained by slow diffusion of pentane into a solution of
compound 2 in CH2Cl2. Owing to the presence of disordered
solvent molecules, the structure (Figure 8) was solved by
using the SQUEEZE command.[28]
Figure 6. 1H NMR spectra (500 MHz, 258C) of compound 2 in CD2Cl2
(a), CD2Cl2/[D6]DMSO (9:1) (b), and [D6]DMSO (c).
Figure 8. Solid-state structure of turnstile 2; hydrogen atoms are omitted
for clarity except for the two NH atoms that were involved in H-bonding
interactions.
1
Indeed, by taking the H NMR spectrum of turnstile 2 in
CD2Cl2 as a reference (Figure 6a), the addition of 10%
[D6]DMSO caused a significant downfield shift of about d=
1.46 ppm of the Ht protons of the CONH group (Figure 6b).
In pure [D6]DMSO (Figure 6c), a downfield shift of about
d=2.73 ppm was observed for the same protons.
At 258C, as for the parent strapped porphyrin (1), the ob-
servation of four doublets Ha, Ha’ and Hb, Hb’ in
[D6]DMSO (Figure 2) for the H atoms of the benzonitrile
moiety of compound 2 indicated a dynamic rotational pro-
cess. Again, this process was investigated by variable-tem-
perature 1H NMR spectroscopy in the range 25–1008C
(Figure 7). We found that, upon heating the solution, only
two doublets, which corresponded to protons Ha and Hb,
were observed. The coalescence temperature for proton Hb
was about 858C, which corresponded to a rotation rate of
about 96 Hz and an activation energy of about 75 kJ.
This single crystal (monoclinic; space group: C2/c) was
composed of compound 2 and disordered solvent molecules.
The SnIV atom was hexacoordinated and almost located at
À
the center of the porphyrin core, with Sn N distances of d=
2.067–2.124 ꢂ with no distortion of the planarity of the por-
phyrin backbone. The remaining two apical positions on the
SnIV center were occupied by two chloride atoms with Sn
À
Cl distances of d=2.480 and 2.452 ꢂ. The coordination ge-
ometry around the metal center was almost octahedral, with
N-Sn-N, N-Sn-Cl, and Cl-Sn-Cl angles of 177.9–178.98 (N-
Sn-Ntrans), 89.5–90.58 (N-Sn-Ncis), 89.1–91.28, and 178.98 re-
spectively. The meso aryl substituents were tilted with re-
spect to the porphyrin plane, with CCCC dihedral angles of
À70.28 and 68.78 for the two phenyl moieties and À75.68
and 66.98 for the benzonitrile groups. One of the two chlo-
ride anions that were oriented towards the handle formed
weak hydrogen bonds with CONH groups with a NH···Cl
distance in the range 2.68–2.65 ꢂ and N-H-Cl angles in the
range 147.6–149.48.
Upon replacement of the two Cl atoms by OH groups to
afford turnstile 3 with C2v symmetry, as was the case for
compound 2, the closed state that resulted from the forma-
tion of CONH···OH H bonds in CD2Cl2 was again con-
firmed by both 1D and 2D NMR spectroscopy. Indeed, a sig-
nificant upfield shift of about d=1.29 ppm was observed for
the Ht signal (Figure 3c), along with reorganization of the
ethyleneglycol spacer (changes in the Hp, Hq and Hv signals
when compared to compounds 1 and 2).
As expected and, as observed for turnstile 2, the 2D
ROESY investigation (Figure 5c) in CD2Cl2 at room tem-
perature revealed new correlations between the Hg protons
of the meso-phenyl groups and the Hv atoms of the handle
1
Figure 7. Region of the H NMR spectra (500 MHz, [D6]DMSO) of com-
pound 2 at 25 (a), 40 (b), 60 (c), 80 (d), 85 (e), 90 (f), 95 (g), and 1008C
(h).
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(for atom labeling, see Figure 2). Furthermore, the two OH
groups that occupied the apical positions on the SnIV center
afforded two distinct signals at about d=À7.51 and
À6.49 ppm, which corresponded to the hydroxy groups that
pointed away from (Hw) and towards the handle (Hw’), re-
spectively (Figure 9a). The 2D ROESY study showed a cor-
Figure 10. Region of the 1H NMR spectra ([D6]DMSO, 500 MHz) of
compound 3 at 25 (a), 40 (b), 60 (c), 80 (d), 90 (e), 95 (f), 100 (g), and
1058C (h). For assignment of the H atoms, see Figure 2.
Figure 9. 2D ROESY correlations in the region of OH groups Hw and
Hwꢃ for compound 3 in CD2Cl2 (a), and for compound 4 (OH) in
[D6]DMSO (b). For the assignment of the H atoms, see Figure 2.
From the coalescence temperature of about 1008C, a rota-
tion rate of about 133 Hz and an activation energy of about
76 kJ were calculated.
relation between the Hw’ and Ht atoms (Figure 9a), thereby
further confirming the presence of the H bond between the
OH and CONH groups.
Conclusion
Again, unlocking turnstile
[D6]DMSO led to its open state (4, X=OH; Figure 2). First,
the behavior of turnstile 3 was studied by H NMR spectros-
3
by the addition of
We have synthesized a series of molecular turnstiles that
contained both H-bond-donor and -acceptor sites. The
design was based on tetra-aryl X2SnIV porphyrins (X=Cl or
OH) as H-bond acceptor sites that were equipped with
a rotor that contained a pyridyldiamide moiety as a H-bond
donor. The linkage of these two parts was achieved through
covalent bonds on the two opposite meso positions on the
porphyrin backbone. By using 1D and 2D NMR techniques,
we showed that switching between the closed state, which
was due to the formation of intramolecular H-bonds, and
the open state of the turnstile could be achieved by using
external H-bond-acceptor molecules, such as DMSO. The
formation of turnstiles by using metal cations to lock the ro-
tation of the rotor around the stator, based on the same
design principles, is currently under investigation.
1
copy at 258C in CD2Cl2/[D6]DMSO (9:1; Figure 3d). As ob-
served for compound 2, sharp signals were observed in the
1H NMR spectrum. When compared to compound 3, a down-
field shift of the Ht signal of about d=0.79 ppm was ob-
served, thereby implying the rupture of the H bond between
the NH and OH groups (Figure 3d); the same trend was
also observed in pure [D6]DMSO (Figure 3e). The Ht signal
at d=7.09 ppm, which corresponded to the CONH amide
group, was even more downfield shifted. 2D ROESY analy-
sis (Figure 5d) showed the disappearance of the correlation
between the Hg and Hv atoms that was observed for turn-
stile 3 in its closed state. Interestingly, the 2D ROESY inves-
tigation also revealed that the correlation between the Hw’
and Ht atoms (Figure 9a) for compound 3 disappeared in
[D6]DMSO (Figure 9b), thus indicating the unlocking of the
movement.
Experimental Section
General: CH3CN and DMF were dried over molecular sieves; THF and
triethylamine were distilled over sodium and KOH, respectively. Analyti-
cal grade CH2Cl2, EtOH, MeOH, and pyridine were used without further
purification. 1H- and 13C NMR spectra were acquired at 258C on either
Bruker AV 300, Brucker AV 400, Brucker AV 500, or Brucker AV 600
spectrometers with deuterated solvent to lock the spectra and residual
solvent as the internal reference. Absorption spectra were recorded on
an Uvikon XL spectrophotometer. IR spectra were recorded on a FTIR-
8400S ATR, Pike miracle germanium. MS was performed by the Service
de Spectrometrie de Masse, University of Strasbourg.
Interestingly, at 258C, the splitting of the Ha and Hb
atoms into four doublets (Ha, Ha’ and Hb, Hb’) for the
open state of turnstile 2 and its closed state (4, X=Cl) in
CD2Cl2 and in [D6]DMSO, respectively, was also observed
for compounds
3 and 4 (X=OH). Furthermore, in
[D6]DMSO, the two OH groups also remained differentiated
owing to the slow rotational movement of the handle on the
NMR timescale. To investigate the dynamics of this process,
variable-temperature 1H NMR spectroscopy in the range
25–1058C was performed on compound 3 in [D6]DMSO
(Figure 10).
The increase in temperature led to coalescence of the sig-
nals that corresponded to benzonitrile protons Ha and Ha’
and Hb and Hb’ (Figure 10 left), as well as of hydroxy pro-
tons Hw and Hw’ (Figure 10 right).
X-ray crystal-structure analysis: Data were collected on
a Bruker
APEX8 CCD Diffractometer that was equipped with an Oxford Cryosys-
tem liquid-N2 device at 173(2) K by using a molybdenum microfocus
sealed-tube generator with mirror-monochromated MoKa radiation (l=
0.71073 ꢂ) operated at 50 kV/600 mA. The structure was solved by using
SHELXS-97 and refined by full-matrix least-squares on F2 by using
SHELXL-97 with anisotropic thermal parameters for all non-hydrogen
atoms.[29] The hydrogen atoms were introduced at calculated positions
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E. Graf, M. W. Hosseini et al.
and not refined (riding model). Owing to the presence of disordered sol-
vent molecules, the SQUEEZE[28] command was used.
OCH2n), 3.72 (m; OCH2m), 4.00 (m, 4H; OCH2l), 4.56 (m, 4H; OCH2k),
5.87 (t, 2H, NHt; 3J=6.0 Hz), 7.43 (dd, 2H, 3J=8.5 Hz, 4J=2.5 Hz; Arj),
7.67 (t, 1H, 3J=7.5 Hz; Pys), 7.69 (t, 2H, 3J=8.0 Hz; Ari), 7.75 (d, 2H,
3J=7.5 Hz; Pyr), 7.77 (d, 2H, 3J=7.5 Hz; Arh), 8.10 (dd, 2H, 3J=8.0 Hz,
4J=1.5 Hz; Ara), 8.18 (dd, 2H, 3J=8.0 Hz, 4J=1.5 Hz; Ara’), 8.19 (br s,
2H; Arg), 8.30 (dd, 2H, 3J=8.0 Hz, 4J=1.5 Hz; Arb), 8.51 (dd, 2H, 3J=
Crystallographic data for strapped porphyrin 2: C69H61Cl2N9O10Sn; Mw =
1365.86; monoclinic; space group: C2/c; a=63.9066(17), b=10.1342(3),
c=25.7502(8) ꢂ; Z=8;
b=105.579(2)8;
U=16064.2(8) ꢂ3;
m=
0.438 mmÀ1; total reflns: 72794; unique reflns: 19772 [R
ACHTUNGTERN(NGNU int)=0.0648];
8.0 Hz, 4J=1.5 Hz; Arb’), 8.96 (d, 4H, 3J=4.5 Hz, J
pyrc), 9.20 ppm (d, 4H, 3J=5.0 Hz, J(Sn,H)=15.0 Hz; b-pyrd); 13C NMR
ACHTUNGTREN(NUGN Sn,H)=15.0 Hz; b-
final R indices [I> 2s(I)]: R1 =0.1138; wR2 =0.3093; R indices (all data):
R1 =0.1737; wR2 =0.3159; GOF on F2: 1.319. CCDC-867898 (2) contains
the supplementary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
Synthesis: Compounds 6,[20b] 10,[22] and 15[19] were prepared according to
literature procedures.
AHCTUNGTRENNUNG
(CD2Cl2, 150 MHz): d=37.4, 68.4, 68.8, 69.8, 70.0, 70.7, 70.8, 71.4, 112.8,
115.8, 119.2, 119.7, 122.5, 122.9, 123.8, 128.3, 128.8, 131.2, 131.4, 132.3,
133.9, 135.7, 136.3, 138.2, 142.1, 146.0, 146.5, 147.0, 148.2, 158.3,
163.3 ppm; IR (ATR): 2229 (CN), 1673 cmÀ1 (CO amide); UV/Vis
(CH2Cl2): lmax (e)=430 (5.6), 560 (4.2), 600 nm (3.9 molÀ1 dm3 cmÀ1).
1H NMR ([D6]DMSO, 600 MHz): d=À6.21 (br s, 1H; OH), À5.21 (br s,
1H; OH), 1.98 (q, 4H, 3J=6.5 Hz; NCH2v), OCH2q overlapped with
DMSO signal, 3.07 (m, 4H; OCH2p), OCH2o overlapped with water
signal, 3.46 (m, 4H; OCH2n), 3.63 (m; OCH2m), 3.90 (m, 4H; OCH2l),
4.46 (m, 4H; OCH2k), 7.09 (t, 2H, 3J=6.0 Hz; NHt), 7.47 (dd, 2H, 3J=
8.0 Hz, 4J=1.5 Hz; Arj), 7.75 (t, 2H, 3J=8.0 Hz; Ari), 7.78 (m, 4H; Pyr,
Compound 1: Compound 13 (650 mg, 896 mmol, 1 equiv) and compound
15 (443 mg, 1.8 mmol, 2 equiv) were dissolved under an argon atmos-
phere in CH2Cl2/EtOH (95:5, 100 mL) in a 250 mL dry two-necked
round-bottomed flask. In the dark, TFA (200 mL, 2.7 mmol, 3 equiv) was
added and the reaction mixture was stirred at RT for 2 days. First, trie-
thylamine was added to neutralize any excess TFA; then, a solution of
DDQ (610 mg, 2.7 mmol, 3 equiv) in THF (20 mL) was added and the
mixture was stirred overnight. After evaporation under reduced pressure,
the crude product was purified by column chromatography on silica gel
(CH2Cl2 to CH2Cl2/MeOH, 95:5) to yield compound 1 (100 mg, 9%) as
a purple powder.
3
3
Arh), 7.87 (t, 1H, J=7.5 Hz; Pys), 7.99 (br s, 2H; Arg), 8.31 (dd, 2H, J=
7.5 Hz, 4J=1.5 Hz; Ara), 8.36 (m, 4H; Ara’, Arb), 8.48 (dd, 2H, 3J=
7.5 Hz, 4J=1.5 Hz; Arb’), 8.93 (d, 4H, 3J=4.5 Hz, J
ACTHNUTRGNE(NUG Sn,H)=13.5 Hz; b-
pyrc), 9.05 ppm (d, 4H, 3J=5.0 Hz, J
ACTHNUTRGNEU(NG Sn,H)=13.5 Hz; b-pyrd). MS (ESI):
m/z calcd for C69H63N9O12Sn: 1330.371 [M+H]+; found: 1130.289.
Compound 7: Compound 6 (15.4 g, 44 mmol, 1 equiv) was dissolved in
dry DMF (150 mL) in a 500 mL two-necked round-bottomed flask. Potas-
sium phthalate (10 g, 54 mmol, 1.2 equiv) was added and the mixture was
heated under an argon atmosphere at 1208C overnight. After removal of
the solvent under vacuum, the residue was dissolved in distilled water
(250 mL) and extracted with CH2Cl2 (3ꢄ150 mL). The organic layer was
dried over MgSO4 and the solvent was removed under vacuum to afford
compound 7 (14.6 g, 73%) as an oil.
1H NMR (CDCl3, 300 MHz): d=3.54–3.76 (m, 14H; OCH2), 3.90 (t, 2H,
3J=6.0 Hz; OCH2), 7.69–7.72 (m, 2H; Ar), 7.83–7.86 ppm (m, 2H; Ar);
13C NMR (CDCl3, 75 MHz): d=37.4, 61.9, 68.1, 70.2, 70.5, 70.6, 70.8,
72.6, 123.4, 132.3, 134.1, 168.4 ppm; elemental analysis calcd (%) for
C16H21NO6: C 59.43, H 6.55, N 4.33; found: C 59.34, H 6.54, N 4.55.
1H NMR (CD2Cl2, 400 MHz): d=À2.92 (br s, 2H; NH), 2.29 (m, 4H;
3
OCH2p), 2.48 (t, 4H, J=6.0 Hz; OCH2q), 2.69 (m, 4H; OCH2o), 2.73 (q,
4H, 3J=6.0 Hz; NCH2v), 3.18 (m, 4H; OCH2n), 3.44 (m; OCH2m), 3.76
(m, 4H; OCH2l), 4.31 (m, 4H; OCH2k), 7.16 (m, 2H; NHt), 7.35 (dd, 2H,
3J=8.5 Hz, 4J=2.0 Hz; Arj), 7.45 (m, 1H; Pys), 7.70 (t, 2H, 3J=8.0 Hz;
Ari), 7.75 (d, 2H, 3J=8.0 Hz; Pyr), 7.81 (br s, 2H; Arg), 7.98 (d, 2H, 3J=
7.5 Hz; Arh), 8.08 (m, 4H; Araa’), 8.28 (m, 2H; Arb), 8.45 (m, 2H; Arb’),
8.78 (d, 4H, 3J=5.0 Hz; b-pyrc), 8.95 ppm (d, 4H, 3J=5.0 Hz; b-pyrd);
13C NMR (CD2Cl2, 100 MHz): d=38.5, 68.4, 68.7, 69.2, 69.9, 70.2, 70.3,
70.9, 115.3, 122.6, 124.2, 127.3, 128.0, 131.1, 132.3, 135.4, 138.4, 148.5,
157.9, 163.2; IR (ATR): 2228 (CN), 1674 cmÀ1 (CO amide); UV/Vis
(CH2Cl2): lmax (e)=418 (5.6), 516 (4.3), 550 (3.9), 589 (3.8), 646 nm
(3.6 molÀ1 dm3 cmÀ1); MS (MALDI-TOF): m/z calcd for C69H63N9O10
1178.478 [M+H]+; found: 1178.481.
:
Compound 8: Compound 7 (13 g, 40 mmol, 1 equiv) was dissolved in
EtOH (250 mL) in a 500 mL two-necked round-bottomed flask under an
argon atmosphere. Hydrazine monohydrate (4 mL, 82 mmol, 2 equiv)
was added and the solution was heated at reflux overnight. The reaction
mixture was acidified with 6m HCl (15 mL) and filtered. After removal
of the solvent, the residue was dissolved in EtOH (50 mL) and filtered
before distilled water (50 mL) was added and the mixture was filtered
again. Evaporation of the solvent under reduced pressure afforded a resi-
due that was dissolved in water and purified on a Dowex 50WX8 column
to afford compound 8 (7.1 g, 90%) as an oil.
1H NMR (CDCl3, 300 MHz): d=3.11 (t, 2H, 3J=5.0 Hz; OCH2), 3.60–
3.71 (m, 10H; NCH2, OCH2), 3.75–3.79 ppm (m, 4H; OCH2); 13C NMR
(CDCl3, 75 MHz): d=40.4, 61.2, 68.7, 69.9, 70.1, 70.4, 70.4, 72.7 ppm; ele-
mental analysis calcd (%) for C8H19NO4·0.5HCl·0.75H2O: C 42.71,
H 9.41, N 6.23; found: C 42.73, H 9.37, N 6.59.
Compound 2: In a 50 mL round-bottom flask, compound 1 (30 mg,
25 mmol, 1 equiv) and SnCl2·2H2O (23 mg, 100 mmol, 4 equiv) were dis-
solved in pyridine (15 mL) and the solution was refluxed overnight. The
solvent was removed under vacuum and the residue was filtered over
celite and the latter was washed with CH2Cl2. Removal of the solvent af-
forded the compound 2 (20 mg, 57%) as a purple solid.
1H NMR (CD2Cl2, 400 MHz): d=2.28 (br s, 4H; NCH2v), 2.60 (br s, 4H;
OCH2q), 3.05 (br s, 4H; OCH2p), 3.31 (br s, 4H; OCH2o), 3.45 (br s, 4H;
OCH2n), 3.65 (br s; OCH2m), 3.94 (br s, 4H; OCH2l), 4.42 (br s, 4H;
OCH2k), 6.13 (br s, 2H; NHt), 7.45 (d, 2H, 3J=8.0 Hz; Arj), 7.75 (t, 2H,
3J=8.0 Hz; Ari), 7.89 (m, 3H; Arh, Pys), 8.02 (br s, 2H; Arg), 8.06 (d, 2H,
3J=7.5 Hz; Pyr), 8.12 (d, 4H, 3J=7.5 Hz; Araa’), 8.21 (m, 2H; Arb), 8.34
(m, 2H; Arb’), 9.12 (d, 4H, 3J=5.0 Hz; b-pyrc), 9.37 ppm (d, 4H, 3J=
5.0 Hz; b-pyrd); 13C NMR (CD2Cl2, 100 MHz): d=38.1, 68.4, 68.8, 69.9,
70.1, 70.5, 71.3, 113.2, 115.3, 118.7, 122.9, 124.7, 128.5, 131.4, 132.4, 133.9,
135.3, 135.9, 138.8, 141.3, 144.8, 145.8, 146.8, 148.5, 158.0, 162.8 ppm; UV/
Vis (CH2Cl2): lmax (e)=431 (5.6), 562 (4.3), 602 nm (4.0 molÀ1 dm3 cmÀ1);
MS (ESI): m/z calcd for C69H61Cl2N9O10Sn: 1388.284 [M+Na]+; found:
1388.256.
Compound 11: Compound 8 (3.1 g, 16 mmol, 1.9 equiv) and triethylamine
(7 mL, 50 mmol, 6.3 equiv) were dissolved in dry CH2Cl2 (200 mL) in
a dry 500 mL two-necked round-bottomed flask under an argon atmos-
phere. Compound 10 (1.7 g, 8 mmol, 1 equiv) was dissolved under an
argon atmosphere in dry CH2Cl2 (100 mL) and added dropwise via a can-
nula. The reaction mixture was stirred overnight under an argon atmos-
phere at RT. After removal of the solvent under vacuum, the crude prod-
uct was purified by column chromatography on alumina (CH2Cl2 to
CH2Cl2/MeOH, 95:5) to afford compound 11 (4 g, 96%) as an oil.
Compound 3: Compound 2 (20 mg, 15 mmol, 1 equiv) and potassium car-
bonate (87 mg, 660 mmol, 44 equiv) were dissolved in CH2Cl2/MeOH
(4:1, 20 mL) in a 50 mL round-bottomed flask and heated to reflux for
5 h. The organic layer was washed with distilled water and dried over
MgSO4. After removal of the solvent under vacuum, the residue was pu-
rified by column chromatography on alumina (CHCl3 to CHCl3/MeOH,
98:2) to yield the desired compound 3 (7 mg, 37%) as a purple solid.
1H NMR (CD2Cl2, 600 MHz): d=À7.51 (br s, 1H; OHw), À6.49 (br s,
1H; OHw’), 1.67 (q, 4H, 3J=6.5 Hz; NCH2v), 2.34 (t, 4H, 3J=7.0 Hz;
OCH2q), 2.96 (m, 4H; OCH2p), 3.28 (m, 4H; OCH2o), 3.54 (m, 4H;
1H NMR (CDCl3, 300 MHz): d=3.36 (br s, 2H; OH), 3.58–3.71 (m, 32H;
3
3
NCH2, OCH2), 7.99 (t, 1H, J=8.0 Hz; Py), 8.32 (d, 2H, J=8.0 Hz; Py),
8.95 ppm (br s, 2H; NH). 13C NMR (CDCl3, 75 MHz): d=39.8, 61.9, 70.4,
70.4, 70.5, 70.6, 72.7, 124.9, 138.8, 149.1, 164.2 ppm; elemental analysis
calcd (%) for C23H39N3O10·0.5H2O: C 52.46, H 7.66, N 7.98; found:
C 52.55, H 7.90, N 7.95.
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Strapped-Porphyrin-Based Molecular Turnstiles
FULL PAPER
Compound 12: Compound 11 (2.9 g, 5.6 mmol, 1 equiv) and triethylamine
(2.4 mL, 17 mmol, 3 equiv) were dissolved in distilled THF (100 mL) in
a dry 250 mL three-necked round-bottomed flask under an argon atmos-
phere. Mesyl chloride (1 mL, 13 mmol, 2.3 equiv) was added and the re-
action mixture was stirred at RT for 2 h. After removal of the volatile
compounds, the residue was dissolved in CH2Cl2 (200 mL), washed with
aqueous NaHCO3 (5%, 3ꢄ200 mL), and dried over MgSO4. The organic
layer was evaporated to dryness under reduced pressure to yield com-
pound 12 (3.5 g, 92%) as an oil.
411; c) A. H. Flood, R. J. A. Ramirez, W.-Q. Deng, R. P. Muller,
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1H NMR (CDCl3, 300 MHz): d=3.07 (s, 3H; CH3), 3.63–3.73 (m, 28H;
NCH2, OCH2), 4.32–4.35 (m, 4H; OCH2), 8.01 (t, 1H, 3J=7.5 Hz; Py),
3
8.33 (d, 2H, J=7.5 Hz; Py), 8.37 ppm (br s, 2H; NH); 13C NMR (CDCl3,
75 MHz): d=37.8, 39.6, 69.1, 69.4, 70.0, 70.3, 70.5, 70.6, 70.7, 125.0, 138.9,
149.0,
154.0 ppm;
elemental
analysis
calcd
(%)
for
C25H43N3O14S2·0.5H2O: C 43.98, H 6.50, N 6.15; found: C 43.88, H 6.73,
N 6.64.
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Compound 13: 3-Hydroxybenzaldehyde 16 (3.2 g, 26 mmol, 4 equiv) and
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under vacuum, the residue was dissolved in CH2Cl2 (200 mL), washed
with aqueous NaHCO3 (5%, 3ꢄ200 mL) and 1m HCl (200 mL), dried
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1H NMR (CDCl3, 300 MHz): d=3.65–3.71 (m, 24H; NCH2, OCH2), 3.81
3
3
(t, 4H, J=4.5 Hz; OCH2), 4.13 (t, 4H, J=4.5 Hz; OCH2), 7.13–7.18 (m,
3
2H; Ar), 7.34–7.36 (m, 2H; Ar), 7.41–7.44 (m, 4H; Ar), 7.98 (t, 1H, J=
8.0 Hz; Py), 8.31 (d, 2H, 3J=8.0 Hz; Py), 8.42 (br s, 2H; NH), 9.95 ppm
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70.6, 70.6, 70.9, 113.0, 122.1, 123.8, 124.9, 130.2, 137.9, 138.8, 149.0, 159.4,
164.0, 192.2 ppm; elemental analysis calcd (%) for C37H47N3O12: C 61.23,
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Acknowledgements
We thank the University of Strasbourg, the International Centre for
Frontier Research in Chemistry (FRC), Strasbourg, the Institut Universi-
taire de France (IUF), the Ministry of Education and Research, and the
CNRS for financial support. We also thank Dr. L. Allouche for NMR
studies and C. Lee for the preliminary investigations.
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Received: February 20, 2012
Published online: && &&, 0000
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Strapped-Porphyrin-Based Molecular Turnstiles
FULL PAPER
Re-turn to sender: Molecular turn-
stiles, which were based on strapped-
type tetra-aryl X2SnIV porphyrins
(X=Cl or OH), that contained both
H-bond-donor and -acceptor sites were
prepared; switching between their
open- and closed states was studied in
solution by 1D and 2D NMR spectros-
copy.
Porphyrins
T. Lang, E. Graf,* N. Kyritsakas,
M. W. Hosseini* .............. &&&& — &&&&
Strapped-Porphyrin-Based Molecular
Turnstiles
Chem. Eur. J. 2012, 00, 0 – 0
ꢁ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
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These are not the final page numbers!