Design and synthesis of Sn-porphyrin based molecular gates

Article abstract of DOI:10.1021/ic902265e

The design, synthesis, and structural characterization, both in solution by 1H NMR and in the solid state by X-ray diffraction on single crystals, of a series of molecular gates based on Sn-porphyrin derivatives are presented. The molecular systemis based on a porphyrin core bearing at the meso positions either phenyl or pyridyl groups as a stator, octahedral Sn(IV) cation located at the center of the porphyrin as a hinge, and different handles connected to the porphyrin through Sn-O axial bonds. The stability of the complexes in the presence of different acids is also reported.

Full text of DOI:10.1021/ic902265e

1872 Inorg. Chem. 2010, 49, 1872–1883
DOI: 10.1021/ic902265e
Design and Synthesis of Sn-Porphyrin Based Molecular Gates
ꢀ
Aurelie Guenet, Ernest Graf, Nathalie Kyritsakas, and Mir Wais Hosseini*
ꢀ
Laboratoire de Chimie de Coordination Organique (UMR-CNRS 7140), Universite de Strasbourg,
Institut Le Bel, 4 rue Blaise Pascal, 67000 Strasbourg, France
Received November 16, 2009
1
The design, synthesis, and structural characterization, both in solution by H NMR and in the solid state by X-ray
diffraction on single crystals, of a series of molecular gates based on Sn-porphyrin derivatives are presented. The
molecular system is based on a porphyrin core bearing at the meso positions either phenyl or pyridyl groups as a stator,
octahedral Sn(IV) cation located at the center of the porphyrin as a hinge, and different handles connected to the
porphyrin through Sn-O axial bonds. The stability of the complexes in the presence of different acids is also reported.
Introduction
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may envisage either translational or rotational motors.1-28
Movement plays a fundamental role in the living world.2
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abiotic systems, the two pioneer investigations undertaken by
A molecular motor may be defined as a molecular archi-
tecture for which a movement may be induced by external
stimuli. The induced and controlled movement must take
*To whom correspondence should be addressed. E-mail: hosseini@
unistra.fr. Phone: 33 368851323. Fax: 33 368851325.
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r
pubs.acs.org/IC
Published on Web 01/22/2010
2010 American Chemical Society

Article
Inorganic Chemistry, Vol. 49, No. 4, 2010 1873
Figure 2. Schematic representation of a molecular gate based on a hinge
(gray square) and a handle (purple unit) bearing each one recognition site.
Opening and closing motions of the gate are induced by coordination of a
metal ion (green sphere) to the two recognition sites. The handle is
considered as the rotor and the hinge as the stator.
Figure 1. Schematic representation of three parts of a rotary motor:
stator (a), hinge complexed by the stator (b), and the rotor (c).
ion may be regarded as an external stimulus responsible for
the locking of the motion.
the groups of Stoddart-Balzani and by Sauvage and co-
workers must be quoted. In the case of Stoddart, following
the supramolecular approach, translational molecular mo-
tors based on the use of only organic moieties arranged in
rotaxane type structures have been described.9 On the other
hand, Sauvage and collaborators, using coordination chemi-
stry, described rotational motors based on induced changes
in the coordination number and geometry around metal
centers in catenane type architectures.10 The same group
has also reported a translational motor based on rotaxanes
bearing a redox active metal center. On the basis of the same
type of strategy, Sauvage and co-workers have also reported
an artificial mobile system qualified as a molecular muscle.20
Recently two other pertinent reports described molecular
motors based on thermal (Kelly et al.)11 or photochemical
(Feringa et al.)12 processes. Other types of molecular machi-
nes undergoing movement on surfaces such as cars,13 wheel-
barrows,14 and turnstiles15 have been also investigated.
Design of molecular machines still remains a challenging
task and continues to attract attention.16-32 For the design of
abiotic motors, four features must be taken into account: (i)
the amplitude of the movement, (ii) the speed of the move-
ment, (iii) the directionality of the movement, and (iv) the
reversibility of the process. These aspects are essential and
need further studies. A possible design of a rotary molecular
motor may be based on a three-part system (Figure 1): a
stator (a), a porphyrin bearing up to 4 peripheral coordina-
tion sites, a hinge (b), hypervalent Sn(IV) octahedral center
complexed by the tetraaza core of the porphyrin, and a rotor
(c), a molecular fragment, doubly attached to the hinge,
bearing a mono dentate coordination site oriented toward the
porphyrin backbone.
Herein, we report on our complete investigation dealing
with the design, synthesis, and structural investigations
of molecular gates based on the above-mentioned design
principles.
Results and Discussion
Design of the System. As stated above, the gate consists
of three main parts: a stator, a hinge, and a handle. The
stator is based on a porphyrin unit, the latter being the
candidate of choice since its meso positions can be sub-
stituted as desired.34 For the present study, the porphyrin
backbone was equipped with three phenyl groups and one
pyridine moiety as a monodentate coordinating site
(compounds 1 and 2). To impose outward orientation
of the coordinating site, the pyridine moiety was con-
nected to the porphyrin core at position 4. For compari-
son purposes, compounds 3 and 4, analogues of 1 and 2,
respectively, were prepared. Compound 3 is based on the
same handle as 1; however it does not contain a coordi-
nating site on the stator and thus its rotation should not
be altered by the presence of the metal cation. Compound
4 is an analogue of 3, but the handle was shortened by two
glycol units allowing thus to study the role played by the
length of the handle. Compound 5, which contains a
coordination site located on the stator and an oligoethyl-
eneglycol fragment as the handle was also prepared.
Finally, compound 6 bearing no coordination site was
synthesized. As for the hinge, Sn(IV), a strong oxophilic
Lewis acid adopting an octahedral coordination geometry,
was chosen.35 Indeed, its binding to the tetrapyrrolic core
of the porphyrin leads to a stable dicationic metallapor-
phyrin offering two apical positions in trans configuration
for the connection of the handle. Furthermore, the intro-
duction of the handle through the formation of two Sn-O
bonds leads to a neutral complex. Finally, the handle was
designed as a relatively flexible bis-monodentate ligand
possessing one central recognition site (pyridine) and two
terminal coordinating sites of the phenate type (resorcinol
moiety) allowing to connect the handle and the hinge
together. The pyridine and resorcinol units are connected
via spacers with variable length.
The viability of the approach, previously reported in a
communication,33 was demonstrated on a molecular gate.
The design of the latter is based on a stator bearing a single
coordination site oriented divergently from its center, a hinge
allowing to connect the handle, and a rotatable handle
equipped with a monodentate coordination site oriented
toward the hinge (Figure 2). In the absence of a metal ion,
the handle rotates freely about the hinge (open gate) whereas
in its presence, the gate is locked by binding of the metal by
both coordinating sites (closed gate). The action of the metal
The purpose of this study was essentially 3-fold: (1)
verify the coordination mode of the handle to the tin
porphyrin, (2) determine the appropriate size of the
(29) Kinbara, K.; Aida, T. Chem. Rev. 2005, 105, 1377–1400.
(30) Molecular machines; Kelly, T. R., Ed.; Topics in Current Chemistry;
Springer: Berlin, Heidelberg, 2005; Vol. 262.
(31) Browne, W. R.; Feringa, B. L. Nat. Nanotechnol. 2006, 1, 25–35.
(32) Kay, E. R.; Leigh, D. A.; Zerbetto, F. Angew. Chem., Int. Ed. 2007,
46, 72–191.
(33) Guenet, A.; Graf, E.; Kyritsakas, N.; Allouche, L.; Hosseini, M. W.
Chem. Commun. 2007, 2935–2937.
(34) (a) Lindsey, J. In The Porphyrin Handbook; Kadish, K. M., Smith,
K. M., Guilard, R., Eds.; Academic Press: San Diego, CA, 2000; Vol. 1, pp
45-118; (b) Lindsey, J. S. Acc. Chem. Res. 2009, DOI: 10.1021/ar900212t.
(35) Arnold, D. P.; Blok, J. Coord. Chem. Rev. 2004, 248, 299–319.

1874 Inorganic Chemistry, Vol. 49, No. 4, 2010
Guenet et al.
Scheme 1. Structures of Compounds 1-6 and Labelling of Hydrogen
Atoms
Scheme 3a
Scheme 2
a Reagents and conditions: (a) DHP, TFA, EtOAc, RT; (b) 1.5 M
NaOHaq, THF, RT; (c) CH3SO2Cl, Et3N, THF, RT; (d) 12, NaH, THF,
reflux; (e) HClaq, MeOH, RT.
dihydropyran in dry EtOAc gave 11 in 74% yield. The
hydrolysis of the latter by NaOH in a mixture of tetra-
hydrofuran (THF)/H2O afforded the compound 12 in
97% yield. It is worth noting that the direct protection of
resorcinol with DHP36 was found to be less efficient
(lower yields) and required a more tedious purification
step. The second starting material, compound 13, was
activated into its dimesylate derivative 14 in quantitative
yield upon reaction with methanesulfonyl chloride at
room temperature (RT) in THF and in the presence of
triethylamine. The reaction of 12 with 14 in the presence
of sodium hydride in refluxing THF during 2 days
afforded the pure compound 15 in 73% yield. Finally,
the deprotection of 15 under acidic conditions in metha-
nol at RT afforded the desired compound 7 in 68% yield.
Because of the introduction of the pyridine moiety, the
synthesis of the other two handles 8 and 9 required three
more synthetic steps (Scheme 4). Starting with 2,6-
bis-(hydroxymethyl)pyridine 16, its dichlorination by
thionyl chloride in dry THF37 afforded the compound
17 in 88% yield. On the other hand, starting either with 18
or 19, their monoprotection by the THP group affording
compounds 20 or 21 was achieved in 42% and 50% yields,
respectively, upon treatment at RT with dihydropyran in
dry chloroform and in the presence of pyridinium tosy-
late.38 It should be noted that, since the monoprotected
oligoethyleneglycols 20 and 21 are less volatile than the
diprotected derivatives, no chromatography was required
handle by varying the length of the spacer, and (3) find
appropriate stimuli to open and close the gate. Indeed,
free rotation of the handle around the hinge in the absence
of a stimulus is one of the prerequisites for the gate. To
tune these parameters, different prototypes of the gate
were prepared.
The first prototype (compound 6, Scheme 1), based on
hexaethyleneglycol as the handle bearing at its two ex-
tremities a resorcinol moiety 7 (Scheme 2), possesses no
specific coordination sites neither on the stator nor on the
handle. This compound was prepared to determine the
actual coordination mode of the bis-monodentate handle
to the tin atom (formation of discrete complex vs poly-
meric entities) and furthermore to demonstrate that the
rotation of the handle around the stator is not altered by
the presence of the metal. For the second type of proto-
types, either the handle (compound 3 and 4, Scheme 1) or
the stator (compound 5, Scheme 1) is equipped with a
pyridine as coordinating site. To determine the appro-
priate length of the two oligoethyleneglycol fragments
connecting the pyridine moiety to resorcinol groups,
based on Corey-Pauling-Koltun (CPK) models, two
handles differing only by the length of the spacer were
prepared (compounds 8 and 9, Scheme 2).
(36) Brown, P. E.; Lewis, R. A.; Waring, M. A. J. Chem. Soc., Perkin
Trans. 1 1990, 2979–2988.
(37) Rezzonico, B.; Grigon-Dubois, M. J. J. Chem. Res. (S) 1994, 142–
143.
(38) Acerete, C.; Bueno, J. M.; Campayo, L.; Navarro, P.; Rodriguez-
Franco, M. I. Tetrahedron 1994, 50, 4765–4774.
Synthesis of Handles. The synthesis of 7 was achieved in
five steps (Scheme 3). Starting with the monoprotected
resorcinol 10, its reaction, under acidic conditions, with

Article
Inorganic Chemistry, Vol. 49, No. 4, 2010 1875
Scheme 4a
Scheme 5. Structures of Compounds 30-34
Scheme 6. Structures of Compounds 35 and 36 and Labelling of
Hydrogen Atoms
a Reagents and conditions: (a) SOCl2, THF, reflux; (b) DHP, PPTS,
CHCl3, RT; (c) NaH, THF, reflux; (d) HClaq, MeOH, RT; (e)
pyrrole with benzaldehyde in refluxing propionic acid
under aerobic conditions. Compound 31 was obtained in
5% yield after chromatography, as previously described41
by mixing benzaldehyde, 4-pyridinecarboxaldehyde, and
pyrrole in refluxing propionic acid.
Synthesis of Tin Porphyrins. As stated above, the stator
(porphyrin backbone) was metalated with Sn(IV) behav-
ing as the hinge and allowing the introduction of the
handle.35 The metalation of 30 followed by in situ hydro-
lysis of the complex 30-SnCl2 was performed as pre-
viously described by Arnold et al.42 Compound 30
reacted with an excess of hydrated tin(II) chloride in
refluxing pyridine. The hydrolysis of the dichloro com-
plex 30-SnCl2 leading to the dihydroxy complex 32
(Scheme 5) was achieved in 50% yield by addition of
ammonia in the reaction medium followed by chroma-
tography on alumina.
ClSO2CH3, Et3N, THF, RT; (f) 12, NaH, THF, reflux; (g) HClaq
MeOH.
,
and simple drying of the crude mixture for 24 h under
vacuum gave the desired compounds in high yields and
large amounts.
Following a reported procedure,39 upon refluxing for
5 days a mixture of either 20 or 21 with 17 and sodium
hydride in dry THF, the functionalized pyridine deriva-
tives 22 and 23 were obtained in 69 and 65% yield,
respectively. Their deprotection affording the diol deri-
vatives 24 and 25 was achieved in 99% and 94% yield,
respectively, by treatment with a mixture of methanol/
aqueous HCl at RT. The activation of diols 24 and 25 into
their dimesylate derivatives, 26 and 27 respectively, was
achieved by treatment at RT with methanesulfonyl chlo-
ride in the presence of triethylamine in dry THF. The
introduction of the resorcinol moiety leading to com-
pounds 28 and 29 was done in 70% and 83% yield,
respectively, by reaction of either 26 or 27 with the
monoprotected resorcinol derivative 12 (Scheme 3) under
reflux for 3 days in dry THF and in the presence of NaH.
Finally, the desired compounds 8 and 9 were obtained in
88% and 99% yields, respectively, upon treatment at RT
of 28 or 29 with methanol/aqueous HCl.
The dihydroxy tin complex 33 was synthesized follow-
ing a similar procedure. However, since the use of chro-
matography to hydrolyze 31-SnCl2 was found to be
inefficient, its formation required two steps. Following
reported procedures43 the reaction of 31 with an excess of
SnCl2 2H2O afforded the dichloro complex 34 in 81%
yield. The hydrolysis of the latter was performed in 81%
yield using K2CO3 in a H2O/THF mixture.
3
Synthesis of Porphyrins. The two porphyrins consid-
ered as stators were the meso-substituted derivatives 30
and 31 (Scheme 5). Whereas compound 30 bears four
phenyl groups at the meso positions, porphyrin 31 is
equipped with a pyridine unit which should act as a
peripheral coordinating site. Following the method de-
scribed by Adler et al.,40 the meso-tetraphenylporphyrin
30 was prepared in 24% yield upon condensation of
Synthesis of Model Porphyrins Bearing 3-Methoxyphe-
nol as Axial Ligands. To study both the reactivity and the
structural features of tin porphyrins bearing two resorci-
nol groups in apical positions, 3-methoxyphenol was used
as a model axial ligand (Scheme 6). The substitution of the
hydroxo ligands by 3-methoxyphenol in both compounds
32 and 33 was achieved following the reported procedures
(41) Meng, G. Z. G.; James, B. R.; Skov, K. A. Can. J. Chem. 1994, 72,
1894–1909.
(42) Arnold, D. P. J. Chem. Educ. 1988, 65, 1111–1112.
(43) (a) Jo, H. J.; Jung, S. H.; Kim, H.-J. Bull. Korean Chem. Soc. 2004, 25,
1869–1873. (b) Crossley, M. J.; Thordarson, P.; Wu, R. A. S. J. Chem. Soc.,
Perkin Trans. 1 2001, 18, 2294–2302.
(39) Nakamura, Y.; Takeuchi, S.; Ohgo, Y.; Yamaoka, M.; Yoshida, A.;
Mikami, K. Tetrahedron 1999, 55, 4595–4620.
(40) Adler, A. D.; Longo, F. R.; Finarelli, J. D.; Goldmacher, J.; Assour,
J.; Korsakoff, L. J. Org. Chem. 1967, 32, 476–476.

1876 Inorganic Chemistry, Vol. 49, No. 4, 2010
Guenet et al.
Table 1. Selected 1H-NMR (300 MHz, CDCl3) Chemical Shifts (δ, ppm) for
3-Methoxyphenol, 35, and 36
Synthesis of Compound 2. Compound 2 was synthesized
by reaction of 33 with a small excess of 8 in dichloro-
methane at RT. Completion of the reaction was moni-
HR
Hβ
Hγ
Hδ
1
tored by H NMR. Indeed, the chemical shifts of the
3-methoxyphenol
35
36
6.44
1.43
1.41
6.44
1.50
1.48
7.14
5.53
5.53
6.51
5.37
5.38
protons located on the phenoxo units (Ha, Hb, Hc, Hd,
Scheme 1) and on the pyridine moiety (Hg, Hh, Hf)
belonging to the handle are affected by the magnetic
anisotropy of the porphyrin ring. As expected, whereas
protons located on the resorcinol moieties are consider-
ably upfield shifted, those corresponding to the pyridyl
unit are only slightly affected by the presence of the
porphyrin core (Table 3). After 6 days, compound 2
was obtained by recrystallization from a mixture of
toluene and n-hexane in 75% yield.
by Langford et al.44,45 Upon refluxing compounds 32 or
33 with an excess of 3-methoxyphenol in CHCl3, com-
plexes 35 and 36 were obtained after recrystallization in
85% and 78% yield, respectively.
The structural features of both 35 and 36 were studied
in solution by H NMR and in the solid state by X-ray
1
diffraction on single crystals.
In solution, as expected,35,46 owing to the magnetic
anisotropy of the porphyrin, the 1H NMR spectra of both
compounds exhibit significant upfield shifts of the proton
signals belonging to the mono protected resorcinol moiety.
In particular, protons R and β (Scheme 6) display a
chemical shift difference of about 5 ppm (Table 1). Further-
more, as expected, couplings between the two 117Sn and
119Sn isotopes and the β-pyrrolic protons, enabling the
assignment of the signals, were also observed.
Synthesis and Solid-State Structural Characterization
of Compounds 3 and 4. The synthesis of both complexes
was achieved at RT in 96% and 92% yield, respectively,
by reaction of 32 with 8 or 9 in chloroform. Again, the
1
completion of the reaction was monitored by H NMR
considering the chemical shifts of the protons located on
the phenoxo and on the pyridine units (Table 3). Inter-
estingly, for both 3 and 4, the rotation of the handle
around the hinge is not hindered as the signal correspond-
ing to the β-pyrrolic protons, easily assigned because of
the Sn-H coupling, appeared as a singlet.
In the crystalline phase, both compounds 3 (Figure 4a)
and 4 (Figure 4b) were characterized by X-ray diffraction
on single crystals. The latter were obtained by vapor
diffusion of n-hexane into a toluene solution containing
the complex.
The solid-state structures of both complexes 35 and 36
were determined by single-crystal X-ray diffraction. Com-
pounds 35 and 36 are isostructural (monoclinic system,
P2/c space group). Selected bond lengths and angles of 35
and 36 are given in Table 2. In both cases, the crystal
contains only the complex, and no solvent molecules are
present (Figure 3). The porphyrin core is almost perfectly
planar, and the Sn atom is located almost at the center of
Whereas, compounds 1 and 3 are isostructural, com-
pounds 3 and 4 are not isostructural. Indeed, whereas for
3, crystals (triclinic, P1) only contain the molecular unit, 4
crystallizes in the orthorhombic system (space group P2)
as a hexane solvate. However, the geometric parameters
of the porphyrin core for both compounds are only
slightly different (see Table 2). The structural features
are similar to those observed for 1. The Sn atom is located
almost at the center of the porphyrin ring and adopts an
almost octahedral geometry. No distortion of the plana-
rity of the porphyrin is observed. The four phenyl groups
are tilted with respect to the porphyrin plane
(C-C-C-C dihedral angles þ55.3°, -63.3°, -65.1°,
and -72.0° for 3 and þ70.1°, þ61.0°, -69.3°, and
-71.0° for 4). For both structures, a fragment of the
polyethyleneglycol chain is disordered.
The two solid-state structures show that both spacers
connecting the two resorcinol moieties to the pyridine
unit are long enough to allow free rotation of the handle
around the hinge as indeed observed in solution (see
above). However, inspection of CPK models as well
X-ray structures clearly shows that, in the case of 4, for
the inline disposition of the N atom of the pyridine moiety
of the handle and the C atom of one of the phenyl groups
of the porphyrin, the distance is too short to permit the
binding of a metal cation such as silver adopting the linear
coordination geometry, whereas for 3, the distance seems
to be perfectly adapted for such a process. For that
reason, the gate 1 bearing the same handle as 3 was
prepared.33 Furthermore, compound 2 was synthesized
to confirm the hypothesis made above on the length of
the handle.
˚
the four pyrrolic units (Sn-N ca. 2.09A; NSnN ca. 89.9° to
90.1° (cis), 179.9° (trans)). The Sn(IV) cation is six-coordi-
nated by four N atoms of the porphyrin and two O atoms of
˚
the two resorcinol groups (Sn-O ca. 2.05 A). The coordi-
nation geometry is essentially octahedral with an OSnO
angle of 179.9° and OSnN angles in the range 88.0 to 92.0°.
The two axial ligands adopt a trans configuration to the tin
atom and an anti arrangement of the two phenol groups.
The four aromatic meso substituents are tilted with respect
to the porphyrin plane (C-C-C-C dihedral angles
þ72.8°, þ67.6°, -63.3°, and -68.1°). The mean plane of
the phenol groups shows an angle of about 36° with respect
to the porphyrin plane. The parameters observed in the
solid-state structures of 35 and 36 are similar to those
already reported for other tin porphyrin complexes.45-48
Synthesis of Compound 1. The synthesis of the mole-
cular gate 1 was achieved by reaction of 33 with a small
excess of 9 in CHCl3 at RT. The evolution of the reaction
was monitored by 1H NMR. The pure compound 1 was
obtained in 97% yield after 18 days. As previously
reported by us in a communication,33 the latter was fully
characterized both in solution by NMR spectroscopy
and in the solid state by X-ray diffraction on single
crystals.
(44) Fallon, G. D.; Langford, S. J.; Lee, M. A. P.; Lygris, E. Inorg. Chem.
Commun. 2002, 5, 715–718.
(45) Fallon, G. D.; Lee, M. A. P.; Langford, S. J.; Nichols, P. J. Org. Lett.
2002, 4, 1895–1898.
(46) Langford, S. J.; Lee, M. A. P.; Macfarlane, K. J.; Weigold, J. A.
J. Inclusion Phenom. 2001, 41, 135–139.
(47) Fallon, G. D.; Lee, M. A. P.; Langford, S. J. Acta Crystallogr., Sect.
E 2001, 57, m564–m565.
(48) Nimri, S.; Keinan, E. J. Am. Chem. Soc. 1999, 121, 8978–8982.

Article
Inorganic Chemistry, Vol. 49, No. 4, 2010 1877
Table 2. Selected Bond Distances and Angles for Compounds 1, 3, 4, 6, 35, and 36
˚
dSn-O (A)
˚
dSn-N (A)
ΦOSnO (deg)
ΦNSnO (deg)
ΦNSnN trans (deg)
ΦNSnN cis (deg)
1a
3
4
6
35
36
2.052(4), 2.058(4)
2.050(10), 2.051(11)
2.040(4), 2.062(4)
2.071(3), 2.078(3)
2.049(3),
2.096(5), 2.104(5), 2.106(5), 2.107(5)
2.089(12), 2.090(10), 2.104(12), 2.105(11)
2.086(4), 2.089(4), 2.095(4), 2.097(4)
2.104(3), 2.112(3), 2.112(3), 2.123(3)
2.090(3), 2.094(3)
176.9
175.7
179.0
178.3
180.0
180.0
87.2-92.1
86.6-92.5
88.0-92.6
88.4-92.9
88.0-91.9
88.1-91.9
179.0-179.7
178.4
179.2-179.3
178.6-179.3
180.0
89.6-90.6
89.3-91.2
89.5-90.5
89.8-90.4
89.8-90.1
89.6-90.4
2.064(5)
2.105(5), 2.110(5)
180.0
a Previously reported, see ref 33.
Figure 3. Crystal structures of 35 (a) and 36 (b). For the latter, the
pyridine unit is disordered over 4 positions. H atoms are omitted for the
sake of clarity. For bond distances and angles, see text and Table 2.
Table 3. Selected 1H-NMR (300 MHz, CDCl3) Chemical Shifts (δ, ppm) for 3-6
and 7-9
Ha
Hb
Hc
Hd
Hf
Hg
Hh
3
4
5
6
7
8
9
1.38
1.33
1.30
1.35
6.49
6.42a
6.43a
1.53
1.55
1.51
1.59
6.42a
6.42a
6.43a
5.53
5.51
5.55
5.53
7.06
7.04
7.07
5.38
5.35
5.38
5.39
6.42a
6.42a
6.43a
4.74
4.76
7.34
7.45
7.42
7.70
Figure 4. Solid-state structures of 3 (a) and 4 (b). In both structures, a
fragment of the polyethyleneglycol units was found to be disordered. H
atoms and solvent molecules are omitted for the sake of clarity. For bond
distances and angles, see Table 2.
4.67
4.67
7.35
7.37
7.65
7.67
a Multiplet.
Synthesis of Compound 5. Compound 5 was synthesized
by reaction of 7 with compound 33 in dichloromethane at
RT for 4 days and was obtained in 78% yield. As for the
previous cases mentioned above, the completion of the
reaction was monitored by 1H NMR. Coordination of the
handle to the tin atom causes substantial upfield shifts of
the proton signals belonging to the phenoxo units (Ha,
Hb, Hc, Hd, Table 3). The β-pyrrolic protons, easily
assigned because of the Sn-H coupling, are not differ-
entiated upon coordination of the handle to the tin atom
indicating a free rotation of the handle around the hinge.
Synthesis and Solid-State Structural Characterization
of Compound 6. The synthesis of 6 was achieved following
a similar procedure as the one described above. In chloro-
form, the condensation of 7 with compound 32 at RT
afforded the compound 6 in 85% yield. Compound 6
exhibits the similar spectral characteristics as compound
5 (see Table 3).
Figure 5. Solid-state structure of 6. A fragment of the hexaethylenegly-
col unit was found to be disordered. Solvent molecules and H atoms are
omitted for the sake of clarity. For bond distances and angles, see Table 2.
vapor diffusion of n-hexane into a toluene solution of 6.
The compound 6 crystallizes (triclinic, P1) as a toluene
hemisolvate with two porphyrin units and one toluene
molecule in the unit cell (Figure 5). The geometric para-
meters of the porphyrin moiety are similar to those
observed for the compounds described above (see
Table 2). The porphyrin core is almost planar. The Sn
atom, located in the center of the porphyrin ring, is
hexacoordinated and surrounded by 4 N atoms (dSn-N
The solid-state structure of 6 was investigated by X-ray
diffraction on single crystals, the latter being obtained by

1878 Inorganic Chemistry, Vol. 49, No. 4, 2010
Guenet et al.
˚
in the range of 2.104 to 2.123 A) and two O atoms (dSn-O
˚
of 2.071 and 2.078 A).
Stability of the Sn-O bond in the Presence of Acids. The
compound 1 was designed as a molecular gate based on
the simultaneous binding of silver cation by both pyridine
units located on the stator and on the handle. Interest-
ingly, by considering the two pyridines as basic sites,
another alternative consisting in closing the gate by a
proton may also be envisaged. In that case, the locking of
the handle to the stator would take place by H-bonding
through the formation of a pyridinium-pyridine complex.
Although the stability of Sn porphyrin complexes in
acidic media was established, that is, the demetalation
occurs only under harsh conditions,35 to the best of our
knowledge, in the presence of competitive ligands, no
systematic study in solution dealing with the stability of
the axial Sn-O bond within phenate complexes has been
reported. To test our idea, we had first to study the
stability of the axial Sn-O bonds in the presence of
different acids. It should be noted that for such investi-
gation, one needs to consider both the strength of the acid
and the propensity of its conjugated base (anion) to bind
to the Sn atom complexed by the porphyrin core. Indeed,
one could expect a proton-catalyzed substitution of the
axial ligand (phenoxide type) by the anion of the acid.
Most of the studies reported so far deal essentially with
the stability of aryloxo complexes under hydrolytic con-
ditions.35 Nimri et al. reported that a tin porphyrin
complex bearing one R-naphthoxy and one chloride
anion as axial ligands was satisfactorily stable during
48 h under physiological conditions (50 mM phosphate
buffer, pH 7.4, [Cl-] = 0.1 M, 37 °C).48 However, the
solution was nevertheless composed of a mixture of
mono- and dichloro complexes.
Figure 6. Crystal structure of 37. Solvent molecules and H atoms are
omitted for the sake of clarity. For bond distances and angles see text.
Figure 7. Crystal structure of 38. The CF3 groups are disordered over
two positions. Solvent molecules and H atoms are omitted for the sake of
clarity. For bond distances and angles see text.
Scheme 7. Structures of Compounds 37 and 38
Complex 35 was used as a model. The reaction in the
presence of variable amounts of different acids in CD3CN
or CDCl3 at 25 °C, was monitored by 1H NMR by
observing the shifts associated with signals related to
the protons of resorcinol groups (γ, δ, and ε) and to the
β-pyrrolic protons (Scheme 6). Both HBF4 and trifluoro-
acetic acid (TFA) were used. They both induced the
decoordination of the monoprotected resorcinol moiety
and its substitution by fluoro or trifluoroacetate anions
respectively. For the addition of 1 or 2 equiv of HBF4 or
of geometric parameters to the one already reported for
the same complex.50 However, the two structures differ by
the presence of CH3CN solvent molecule in the present
case which leads to another crystal system, as well as
another space group. For the compound 38, no solvent
molecules were found to be included in the crystal
(triclinic, P1).
To study the role played by the binding ability of the
anion, weakly coordinating sufonate derivatives were
considered. Indeed, such anions have been described
previously as weak ligands for tin porphyrins.35 Thus,
trifluoromethanesulfonic acid (TfOH) and methanesul-
fonic acid (MsOH) were tested. In the case of 35, the
addition of TfOH leads to a rapid equilibrium between
different porphyrins (presence of five singlets exhibiting
Sn-H coupling, Figure 8). The singlet corresponding
to the β-pyrrolic protons of the starting material (δ =
9.09 ppm) completely disappeared after addition of
3 equiv of TfOH. In the meantime, a singlet correspond-
ing to the triflate complex (30-Sn(TfO)2) appeared
1
TFA, the H NMR study revealed the disappearance of
the complex 35 and the concomitant generation of
the 3-methoxyphenol as well as complexes 37 (signal at
9.43 ppm49)and 38 (signals at 9.33 ppm) (Scheme 7). For a
1
detailed description of H NMR spectra see Figures S1
(HBF4) and S2 (TFA) in the Supporting Information.
Furthermore, the solid state structures of both species
were determined by X-ray diffraction on single crystals
(see the X-ray section in the Supporting Information)
formed in the NMR tube upon slow evaporation (Figures
6 and 7). For the description of both structures see
the Supporting Information. The presence of F- anion
results from the dissociation of BF4-anion into BF3
and F-. The solid-state structure of 37 consists of
the difluorocomplex 37 and four CH3CN solvent mole-
cules. The structure obtained here is similar in terms
(49) Arnold, D. P.; Morrison, E. A.; Hanna, J. V. Polyhedron 1990, 9,
1331–1336.
(50) Arnold, D. P.; Tiekink, E. R. T. Polyhedron 1995, 14, 1785–1789.

Article
Inorganic Chemistry, Vol. 49, No. 4, 2010 1879
Table 4. Effect of the Addition of Triflic Acid to a CDCl3 Solution of 36 on the
Relative Percentage (%) of the Three Different Species Bearing 3-Methoxyphenol
Unit
36
mixed complex
free 3-methoxyphenol
1 equiv
2 equiv
3 equiv
46%
5%
0%
13%
28%
27%
41%
67%
73%
Table 5. Effect of the Addition of Methanesulfonic Acid to a CDCl3 Solution of
36 on the Relative Percentage (%) of the Three Different Species Bearing
3-Methoxyphenol Unit
36
mixed complex
free 3-methoxyphenol
1 eq
2 eq
3 eq
47%
18.5%
3%
11%
18.5%
18%
42%
63%
79%
acid added. Furthermore, three signals at -0.41 ppm,
-0.59 ppm, and -0.63 ppm are observed. These corre-
spond to methyl protons of the methanesulfonate anion
indicating the substitution of the methoxyphenol ligands
by sulfonate anions. Again, it is possible to determine the
relative amounts of each species in solution (Table 5).
Surprisingly, independent of the nature of the acid
added (MsOH or TfOH), the percentages of the three
species present in solution are roughly the same for all
three numbers of equivalents added. This indicates that
the amount of the different complexes in solution is not
only related to the pKa values of the acids added
(pKaMsOH ≈ -2, pKaTfOH ≈ -13) but also depends on
the binding propensity of the conjugated base. This
observation is in agreement with Langford’s statement.46
However, it is the opposite of what was reported by
Sanders et al. who observed a linear pKa dependence for
carboxylate anions.52 Thus, HBF4, TFA, TfOH, and
MsOH acids are not suitable as proton sources since all
four, although with not the same efficiency, lead to the
substitution of phenoxy type ligands by their counterions.
Binding of Agþ Cation to Compounds 1-6. As demon-
strated above, the use of acids as external stimulus to lock
the gate by H-bonding is not feasible. However, as
reported earlier in a communication,33 the locking pro-
cess may be achieved by silver cation in the case of 1. The
role of Agþ cation as an external stimulus was investi-
gated by 1H NMR for compound 2 possessing a shorter
handle when compared to compound 1 as well as for
prototypes 3-6. The choice of silver cation as external
stimulus was based on the following rationale. Owing to
its d10 electronic configuration, silver cation exhibits a
rather loose geometric demand and, as often observed
(see for example refs 53-58), in the presence of two pyr-
idine moieties, it adopts a linear coordination geometry
1
Figure 8. Portions of the H NMR spectra (300 MHz, CDCl3, 25 °C)
and assignment of signals between 1.1-7.2 ppm and 8.8-9.5 ppm for the
complex 35 in the presence of 0 (A), 1 (B), 2 (C), and 3 (D) equiv of triflic
acid. For assignment of H-atoms see Scheme 6. ( refers to the starting
porphyrin 35, ) and * refer to two new porphyrin derivatives, and the
black clover leaf refers to 30-Sn(TfO)2.
at 9.37 ppm.51 Upon addition of 1 or 2 equiv of TfOH,
3 singlets are observed for the methoxy protons
(ε, Scheme 6) of resorcinol moieties indicating the pre-
sence of 3 different species. Two out of the three signals
correspond to the free 3-methoxyphenol (δ=3.77 ppm)
and the initial complex 35 (δ = 2.95 ppm) respectively.
The third one corresponds to a mixed complex bearing
one methoxyphenol and another axial ligand (TfO- or
OH-). When 3 equiv of TfOH are added, the signal at
2.95 ppm corresponding to 35 disappeared implying the
substitution of both monoprotected resorcinol ligands by
TfO- or OH- groups. In solution, the relative concentra-
tion of these three different species may be quantified
by considering the integrations of the signals correspond-
ing to protons ε in 35 (δ=2.95 ppm), the mixed complex
(δ = 3.04 ppm) and the free (δ = 3.77 ppm) species
(Table S3, see Supporting Information).
Since the complex 36 bears a pyridine group attached to the
porphyrin moiety, the effect of the addition of TfOH was also
studied on this compound. The same type of behavior was
again observed (Figure S3, see Supporting Information).
Indeed, upon addition of TfOH to 36, the decoordination
of both methoxyphenolate type ligands and their replacement
by TfO- or OH- anions take place (Table 4).
The behavior of complex 36 in the presence of different
equivalents of MsOH, a weaker acid than TfOH, was also
studied under the same conditions (Figure S4, see Sup-
porting Information). Unfortunately, again, the intensity
of the signals related to the free 3-methoxyphenol is
enhanced upon increasing the number of equivalents of
(52) Hawley, J. C.; Bampos, N.; Sanders, J. K. M.; Abraham, R. J. Chem.
Commun. 1998, 661–662.
(53) Kondo, M.; Kimura, Y.; Wada, K.; Mizutani, T.; Ito, Y.; Kitagawa,
S. Chem. Lett. 2000, 818–819.
(54) Carlucci, L.; Ciani, G.; Proserpio, D. M.; Porta, F. Angew. Chem.,
Int. Ed. 2003, 42, 317–322.
(55) Bosch, E.; Barnes, C. L. Inorg. Chem. 2001, 40, 3234–3236.
(56) Bowmaker, G. A.; Effendy; Lim, K. C.; Skelton, B. W.;
Sukarianingsih, D.; White, A. H. Inorg. Chim. Acta 2005, 358, 4342–4370.
(57) Greco, N. J.; Hysell, M.; Goldenberg, J. R.; Rheingold, A. L.; Tor, Y.
Dalton Trans. 2006, 2288–2290.
(51) Smith, G.; Arnold, D. P.; Kennard, C. H. L.; Mak, T. C. W.
Polyhedron 1991, 10, 509–516.
(58) Engelhardt, L. M.; Pakawatchai, C.; White, A. H. J. Chem. Soc.,
Dalton Trans. 1985, 117–123.

1880 Inorganic Chemistry, Vol. 49, No. 4, 2010
Guenet et al.
Figure 10. Portions of the 1H NMR spectra (CD3CN, 400 MHz, 25 °C)
of 2 in the presence of 0 (A), 0.5 (B), 1 (C), 2 (D), and 3 (E) equiv of AgOTf
and assignments of signals (see Scheme 1) between 3 and 5 ppm. * refers to
new species formed.
Figure 9. Portions of the 2D Roesy correlation (1H-1H NMR,
CD3CN, 500 MHz, 25 °C) of 1 in the absence of any metal cation.
perfectly suited for the present design principle. More-
over, the binding affinity of pyridine for silver is high
enough to afford a stable complex. The latter is labile
allowing thus reversible coordination/decoordination
processes leading to closing and opening of the gate.
Finally, Ag(I) is diamagnetic and enables 1H NMR
studies of such dynamic systems.59,60 As reported earl-
ier,33 in the case of the molecular gate 1, free rotation of
the handle around the stator takes place in the absence of
any stimulus. Indeed, the only correlation peaks observed
on the Roesy spectrum of 1 correspond to chemically lin-
ked protons (Hm and Hn, Hh and Hg, Hf and Hg, Figure 9,
Scheme 1). This was explained by fast rotation of the
handle around the Sn-O bond. The same behavior is also
observed for the prototype 2.
For the gate 1, in the presence of 1 or 2 equiv of AgOTf,
the closing of the gate results in the appearance of new
correlation peaks owing to spatial proximity of the two
pyridine units (correlation peaks between proton Hn of
the stator and protons He4, He5, He6, and Hf of the handle,
see Figure S6 in Supporting Information). Compound 2
was also studied in the presence of Agþ to establish the
role played by the length of the handle on the simul-
taneous binding of the cation by both pyridine units. The
titration of 2 with different equivalents of Agþ was
investigated by 1H NMR in CD3CN. The same procedure
as for 1 was used.33 Binding of Agþ by 2 induces small
downfield shifts of the signal of Hf protons (Scheme 1,
Figure 10) as well as proton signals belonging to both pyri-
dine moieties (Hg, Hh, Hm, and Hn, Scheme 1, Figure 11).
The signals assigned to the β-pyrrolic protons are also
affected by the binding process. It is worth noting that in
the case of 2, the difference in the chemical shift observed in
the presence of up to 2 equiv of silver cation is much less
pronounced for all protons than in the case of 1 (Table 6).
Moreover, ROESY experiments (Figure S7, see Supporting
Information) performed when 1 equiv of Agþ was added
Figure 11. Portions of the 1H NMR spectra (CD3CN, 400 MHz, 25 °C)
of 2 in the presence of 0 (A), 0.5 (B), 1 (C), 2 (D), and 3 (E) equiv of AgOTf
and assignments of signals (see Scheme 1) between 7 and 9.5 ppm. * refers
to new species formed.
Table 6. Selected 1H-NMR Chemical Shifts Difference (in Hz) of Protons
Located on the Pyridine Moieties for 1-5 in the Presence of 0 and 2 equiv of
AgOTf
Hg
Hh
Hm
Hn
1a
2a
3b
4b
5c
155
25
12
>6*
>255*
>24*
24
>60*
5
70
3
6
6
12
a CD3CN, b CD3CN/CD2Cl2 8/2, c CD3CN/CD2Cl2 6/4, * Signals
hidden under other peaks.
showed no correlation peak between protons Hn and Hf
indicating the absence of spatial proximity of the two
pyridines. This may be due to the absence of the simulta-
neous binding of the cation by both pyridines. This observa-
tion correlates also with the small shifts observed upon
addition of the cation to the prototype 2.
It is worth noting that whereas for 1, the addition of
increasing amounts of Agþ cation leads to a single species,
that is, observation of a single set of signals, in the case of
^
(59) Bogdan, N.; Grosu, I.; Benoit, G.; Toupet, L.; Ramondenc, Y.;
ꢀ
Condamine, E.; Silaghi-Dumitrescu, I.; Ple, G. Org. Lett. 2006, 8, 2619–
2622.
(60) Chou, T.-C.; Hwa, C.-L.; Lin, J.-J.; Liao, K.-C.; Tseng, J.-C. J. Org.
Chem. 2005, 70, 9717–9726.

Article
Inorganic Chemistry, Vol. 49, No. 4, 2010 1881
2, the addition of the cation generates new species which
may correspond to polynuclear species and complexes
bearing CH3CN as secondary ligand (Figures 10 and 11).
The formation of these entities probably originates from
the shortening of the handle and consequently the dis-
tance between the two pyridine units located respectively
on the stator and the handle preventing thus the forma-
tion of the desired complex. This is in agreement with the
ROESY experiment described above.
The effect of binding of silver cation by the other four
prototypes 3-6 was also studied. For compounds 3-5
bearing a pyridine unit on the handle (for 3 see Figure S8
and Table S6 and for 4 see Figure S9 and Table S7 in the
Supporting Information) or on the stator (5, Figure S10
and Table S8 in the Supporting Information), in the
presence of Agþ cation, slight differences in the chemical
shifts were observed indicating some interactions between
the cation and the pyridine unit (Table 6). In the case of
the prototype 6, bearing no coordination site, as expected,
no change in the 1H NMR signals was observed
(Figure S11 and Table S9 in the Supporting Information).
Ethyl acetate, CH3CN, and CHCl3 were dried over molecular
sieves. All air and water sensitive experiments were carried out
under argon atmosphere using standard vacuum line techni-
ques. All chemicals were obtained commercially and used with-
out further purification, except pyrrole which was purified over
an alumina column before use.
1H-and 13C NMR spectra were acquired on either a Bruker
AV 300 (300 MHz), a Bruker AV400 (400 MHz), or a Bruker AV
500 (500 MHz) spectrometer, with the deuterated solvent as the
lock and residual solvent as the internal reference. Absorption
spectra were recorded using an Uvikon XL spectrophotometer.
Elemental analyses were performed by the Service de Micro-
analyses, ULP, Strasbourg. Matrix assisted laser desorption
ionization time-of-flight (MALDI-TOF) spectra were taken on
a Bruker autoflex II TOF TOF (equipped with a nitrogen laser
and used in reflectron mode) with dithranol (1,8,9-trihydroxy-
anthracene) as matrix. A microTOF LC (Bruker Daltonics,
Bremen) spectrometer equipped with an electrospray source
was used for the electrospray mass spectrometry measurements
(ES-MS).
Synthesis. Here, only the synthetic procedures for the prepara-
tion of the final compounds 1-6 are given. The detailed syntheses
of all the other 27 intermediates (7 -34) as wellas complexes 35 and
36 are described in the Supporting Information.
Compound 1. To a solution of 33 (25.6 mg, 0.033 mmol,
1 equiv) in dry CHCl3 (25 mL) was added dropwise a solution of
9 (21.6 mg, 0.037 mmol, 1.1 equiv) in dry CHCl3 (25 mL) at RT.
The mixture was stirred at RT for 18 days. The evolution of the
reaction was monitored by 1H NMR. The solvent was then
removed under vacuo. The crude product was recrystallized
by slow diffusion of n-hexane (75 mL) into a toluene solution
(17 mL) of the desired compound to afford purple crystals
(42.2 mg, 97%). Single crystals suitable for X-ray diffraction
were grown by vapor diffusion of n-hexane into a toluene
solution containing the desired compound. 1H NMR (CD3CN,
500 MHz, 25 °C): δ (assignments according to COSY and
Conclusions
The design of molecular gates is presented based on
porphyrin cores bearing at the meso positions either phenyl
or pyridyl groups acting as a stator, octahedral Sn(IV) cation
located at the center of the porphyrin behaving as a hinge,
and different resorcinol based handles connected to the
porphyrin through Sn-O axial bonds. All parts of the
molecular system have been finely tuned. For their prepara-
tion, a rather long stepwise synthetic strategy was developed.
In addition to classical characterization techniques, 7 of the
newly reported derivatives have been structurally studied in
the crystalline phase by X-ray diffraction methods on single
crystals. The stability of two model Sn-porphyrin complexes
bearing two monoprotected resorcinol moieties in the pre-
sence of different acids was studied in solution by 1H NMR.
Both the strength of the acid and the coordination propensity
of the anion were found to be important. Indeed, upon
addition of different acids (HBF4, TFA, MsOH, TfOH),
the substitution of the axial resorcinol group by the anion was
observed. This indicated that a proton can not be used as an
external stimulus. The gate was designed to function with
silver cation as effector. The systematic study carried out on
the gate 1 and its analogues 2-6 (prototypes) clearly demon-
strated the need for the simultaneous presence of the two
coordinating sites on the stator and on the handle. Further-
more, it allowed to determine the optimum distance between
the two parts, that is, the length of the handle, for the binding
of the cation by both sites.
1
4
ROESY 2D H-1H NMR experiments) 1.21 (t, J=2.3 Hz,
2H, Ha,), 1.41 (ddd, 3J=8.0 Hz, 4J=2.1 Hz, 4J=0.8 Hz, 2H, Hb),
3.12 (t, J=4.6 Hz, 4H, He1), 3.41 (m, 4H, He2), 3.49 (m, 4H,
3
He3), 3.55 (m, 4H, He4), 3.62 (m, 4H, He5), 3.67 (m, 4H, He6),
4.58 (s, 4H, Hf), 5.33 (ddd, 3J=8.2 Hz, 4J=2.4 Hz, 4J=0.8 Hz,
2H, Hd), 5.50 (t, 3J=8.1 Hz, 2H, Hc), 7.21 (d, 3J=7.8 Hz, 2H,
Hg,), 7.36 (t, 3J=7.8 Hz, 1H, Hh), 7.83-7.90 (m, 9H, Hi1, Hi2,
HJ1, HJ2), 8.13 (dd, 3J=4.1 Hz, 4J=1.6 Hz, 2H, Hm), 8.17-8.19
(m, 6H, Hk1, Hk2), 9.04 (dd, 3J=4.2 Hz, 4J=1.5 Hz, 2H, Hn),
9.09 (d, 3J=4.9 Hz, 2H, HL4), 9.10 (s, 4H, HL1, HL2), 9.12 (d, 3J=
4.9 Hz, 2H, HL3). 13C NMR (CD3CN, 125 MHz): δ (assign-
ments according to HSQC and HMBC 2D 1H-13C NMR
experiments) 67.0 (Ce1), 69.9 (Ce2), 70.92 (Ce6), 70.9 (Ce5), 71.0
(Ce3), 71.1 (Ce4), 74.6 (Cf), 103.7 (Ca), 104.4 (Cd), 110.5 (Cb),
119.7 (Cp), 120.7 (Cg), 123.5 (Cs, Cw), 127.6 (Cc), 128.0 (CJ1, CJ2),
129.6 (Ci1, Ci2), 130.3 (Cm), 133.0 (CL4), 133.9 (CL1, CL2), 134.1
(CL3), 135.7 (Ck1, Ck2), 138.2 (Ch), 141.5 (Ct, Cx), 147.1 (Cu, Cv,
Cr), 148.4 (Cq), 149.3 (Cn), 149.7 (Co), 157.0 (Ca2), 158.9 (Ca1),
159.3 (Cf1). Labeling of the hydrogen and carbon atoms is given
in the Supporting Information. UV-vis (CH2Cl2) λ max (nm)
(ε, mol-1 L cm-1) 425 (3.2 ꢀ 105), 560 (2.1 ꢀ 104), 600 (1.0 ꢀ
104). MALDI-TOF MS: m/z obsd 1319.43, calcd 1319.39 [(M þ
H)þ; M=C74H66N6O10Sn].
The design of other analogue systems based on porphyrin
units bearing at the meso positions different coordination
sites is currently under investigation. Modification of the
handle by increasing the denticity of its coordinating site for
example should allow the use of transition metal cations to
control the locking/unlocking of the gate. Work along these
lines is currently ongoing.
Compound 2. To a solution of 33 (30.3 mg, 0.040 mmol, 1
equiv) in dichloromethane (60 mL) was added a solution of 8
(20.9 mg, 0.042 mmol, 1.05 equiv) in dichloromethane (20 mL).
The resulting solution was stirred at RT during 6 days. After
removal of the solvent, the dark red residue was recrystallized by
slow diffusion of n-hexane into a toluene solution containing the
desired compound (37 mg, 75%). 1H NMR (CD3CN/CD2Cl2 8/
2, 500 MHz): δ (assignments according to COSY and ROESY
2D 1H-1H NMR experiments) 1.18 (t, 4J=2.3 Hz, 2H, Ha), 1.40
(ddd, 3J=8.0 Hz, 4J=2.1 Hz, 4J=0.9 Hz, 2H, Hb), 3.09-3.14
Experimental Section
General Procedures. Solvents were dried using standard
techniques: THF and CH2Cl2 were distilled over Na and
CaH2, respectively. Pyridine and Et3N were dried over KOH.

1882 Inorganic Chemistry, Vol. 49, No. 4, 2010
Guenet et al.
(m, 4H, He1), 3.39-3.44 (m, 4H, He2), 3.58-3.62 (m, 4H, He3),
3.70-3.74 (m, 4H, He4), 4.66 (s, 4H, Hf), 5.31 (dd, 3J=7.2 Hz, 4
J=2.5 Hz, 2H, Hd), 5.49 (t, 3J=8.0 Hz, 2H, Hc), 7.40 (d, 3J=
7.8 Hz, 2H, Hg), 7.76 (t, 3J=7.8 Hz, 1H, Hh), 7.82-7.92 (m, 9H,
Hi,J), 8.10-8.16 (m, 2H, Hm), 8.17 -8.22 (m, 6H, Hk), 9.02 (d,
3J=5 Hz, 2H, HL4), 9.03 (m, 2H, Hn), 9.07 (s, 4H, HL1,L2), 9.07
(d, 3J=6.5 Hz, 2H, HL3). 13C NMR (CD3CN/CD2Cl2 8/2, 100
MHz): δ (assignments according to HSQC and HMBC 2D
1H-13C NMR experiments) 66.4 (Ce1), 69.0 (Ce2), 70.1 (Ce4),
70.8 (Ce3), 74.1 (Cf), 102.7 (Ca), 103.0 (Cd), 109.8 (Cb), 118.4
(Cp), 120.1 (Cg), 122.4 (Cs,w), 126.4 (Cc), 127.0 (Ck), 128.5 (CJ),
129.3 (Cm), 131.8 (CL4), 132.8 (CL1,L2), 133.0 (CL3), 134.6 (Ci),
137.1 (Ch), 140.5 (Ct,x), 146.2 (Cq), 147.1 (Cr,u,v), 147.2 (Co),
148.4 (Cn), 155.7 (Ca1), 157.4 (Ca2), 158.3 (Cg1). UV-vis
(CH2Cl2) λ max (nm) (ε, mol-1 L cm-1) 424 (2.2 ꢀ 105), 560
(1.5 ꢀ 104), 600 (0.8 ꢀ 104) MALDI-TOF MS: m/z obsd
1231.30, calcd 1231.34 [(M-H) þ; M=C70H58N6O8Sn].
max (nm) (ε, mol-1 L cm-1) 425 (3.0 ꢀ 105), 561 (1.9 ꢀ 104), 601
(1.1 ꢀ 104). MALDI-TOF MS: m/z obsd 1230.31, calcd 1230.34
[(MþH)þ; M=C71H59N5O8Sn].
Compound 5. To a solution of 7 (6.1 mg, 0.013 mmol, 1 equiv)
in dichloromethane (5 mL) was added 33 (10 mg, 0.013 mmol, 1
equiv). The resulting solution was stirred at RT for 4 days. After
removal of the solvent, a violet powder was obtained which was
recrystallized in a mixture of toluene/n-hexane (12.2 mg, 78%).
1H NMR (CD2Cl2, 400 MHz): δ (assignments according to
COSY and ROESY 2D 1H-1H NMR experiments) 1.28 (t, 4J=
2.3 Hz, 2H, Ha), 1.53 (ddd, 3J=8.0 Hz, 4J=2.0 Hz, 4J=0.9 Hz,
2H, Hb), 3.14-3.16 (m, 4H, He1), 3.49-3.51 (m, 4H, He2),
3.60-3.63 (m, 4H, He3), 3.66-3.69 (m, 4H, He4), 3.71 (s, 8H,
H
e5,e6), 5.38 (ddd, 3J=8.0 Hz, 4J=2.3 Hz, 4J=0.8 Hz, 2H, Hd),
5.55 (t, 3J=8.0 Hz, 2H), 7.86-7.93 (m, 9H, Hi,J), 8.19 (dd, 3J=
4.2 Hz, 4J=1.5 Hz, 2H, Hm,), 8.27-8.29 (m, 3H, Hk), 9.11 (dd,
3J=3.6 Hz, 4J=1.2 Hz, 2H, Hn), 9.14 (d, 3J=4.8 Hz, 2H, HL3),
9.21 (s, 4H, HL1,L2), 9.23 (d, 3J=4.8 Hz, 2H, HL4). 13C NMR
(CD2Cl2, 100 MHz): δ (assignments according to HSQC and
HMBC 2D 1H-13C NMR experiments) 66.6 (Ce1), 69.5 (Ce2),
71.0 (Ce3,e4,e5,e6), 103.3 (Ca), 104.2 (Cd), 110.5 (Cb), 118.2 (Cp),
126.7 (Cc), 126.9 (Cs,w), 127.5 (Ci), 128.8 (CJ), 129.6 (Cm), 131.6
(Cq), 132.0 (CL3), 132.6 (CL1,L2), 132.8 (CL4), 135.0 (Ck), 140.5
(Ct,x), 146.1 (Cr), 147.2 (Cu,v), 148.5 (Co), 148.9 (Cn), 155.6 (Ca2),
Compound 3. To a solution of 32 (24.0 mg, 0.031 mmol, 1
equiv) in dry chloroform (10 mL) was added dropwise under
argon a solution of 9 (20.0 mg, 0.034 mmol, 1.1 equiv) in dry
chloroform (20 mL). The resulting mixture was stirred at RT
1
during 6 days. The reaction was monitored by H NMR. The
solvent was removed in vacuo. The resulting powder was
recrystallized by slow diffusion of n-hexane into a toluene
solution of 3 to afford a crystalline violet powder (40.0 mg,
96%). Single crystals suitable for X-ray diffraction were grown
by vapor diffusion of n-hexane into a toluene solution contain-
ing the desired compound. 1H NMR (CDCl3, 300 MHz): δ 1.38
(t, 4J=2.2 Hz, 2H, CHres), 1.53 (dd, 3J=7.7 Hz, 4J=2.1 Hz, 2H,
CHres), 3.16 (t, 3J=5.0 Hz, 4H, CH2O), 3.49 (t, 3J=5.0 Hz, 4H,
CH2O), 3.59 (m, 4H, CH2O), 3.64 (m, 4H, CH2O), 3.76 (m, 8H,
CH2O), 4.74 (s, 4H, ArCH2), 5.38 (dd, 3J=8.1 Hz, 4J=2.2 Hz,
2H, CHres), 5.53 (t, 3J = 8.0 Hz, 2H, CHres), 7.34 (d, 3J =
157.1 (Ca1). UV-vis (CH2Cl2) λ max (nm) (ε, mol-1 L cm-1
)
425 (2.0 ꢀ 105), 560 (1.3 ꢀ 104), 600 (0.7 ꢀ 104). MALDI-TOF
MS: m/z obsd 1198.17, calcd 1198.34 [(MþHþ); M =
C67H59N5O9Sn].
Compound 6. To a solution of 32 (50.2 mg, 0.066 mmol, 1
equiv) in dry chloroform (20 mL) was added dropwise under
argon a solution of 7 (33.8 mg, 0.073 mmol, 1.1 equiv) in dry
chloroform (30 mL). The resulting mixture was stirred at RT
during 5 days. The reaction was monitored by 1H NMR. After
removal of the solvent, the resulting powder was recrystallized
by slow diffusion of n-hexane into a toluene solution of 6
affording a crystalline dark red powder (68.3 mg, 85%). Single
crystals suitable for X-ray diffraction were grown by vapor
diffusion of n-hexane into a toluene solution containing the
compound. 1H NMR (CDCl3, 300 MHz): δ 1.35 (t, 4J=2.1 Hz,
2H, CHres), 1.59 (dd, 3J=7.7 Hz, 4J=2.0 Hz, 2H, CHres), 3.15 (t,
3J = 4.9 Hz, 4H, CH2O), 3.50 (t, 3J = 4.9 Hz, 4H, CH2O),
3.59-3.74 (m, 16H, CH2O), 5.39 (dd, 3J=7.9 Hz, 4J=2.2 Hz,
2H, CHres), 5.53 (t, 3J = 8.0 Hz, 2H, CHres), 7.78-7.86 (m,
12H, CHPh meta/para), 8.21-8.24 (m, 8H, CHPh ortho), 9.11 (s, 8H,
CHβ-pyrrolic, 4JSn-H=12.4 Hz). 13C NMR (CDCl3, 75 MHz): δ
66.3 (CH2O), 69.5 (CH2O), 70.6 (2ꢀCH2O), 70.9 (CH2O), 71.0
(CH2O), 103.2 (CH), 103.6 (CH), 110.4 (CH), 121.8 (Cquat),
126.3 (CH), 127.0 (CH), 128.3 (CH), 132.6 (CH), 134.9 (CH),
141.0 (Cquat), 147.3 (Cquat). UV-vis (CH2Cl2) λ max (nm) (ε,
mol-1 L cm-1) 425 (2.7 ꢀ 105), 561 (1.6 ꢀ 104), 600 (0.9 ꢀ 104).
3
7.5 Hz, 2H, CHPy), 7.42 (t, J=7.7 Hz, 1H, CHPy), 7.78 (m,
12H, CHPh meta/para), 8.19 (m, 8H, CHPh ortho), 9.07 (s, 8H,
CHβ-pyrrolic, 4JSn-H=12.6 Hz). 13C NMR (CDCl3, 75 MHz): δ
66.2 (CH2O), 69.6 (CH2O), 70.5 (CH2O), 70.7 (CH2O), 70.8
(CH2O), 70.9 (CH2O), 74.2 (CH2O), 103.2 (CH), 103.7 (CH),
110.4 (CH), 120.1 (CH), 121.8 (Cquat), 126.3 (CH), 126.9 (CH),
128.3 (CH), 132.5 (CH), 134.9 (CH), 137.2 (CH), 141.0 (Cquat),
147.2 (Cquat), 155.8 (Cquat), 157.0 (Cquat), 158.0 (Cquat). UV-vis
(CH2Cl2) λ max (nm) (ε, mol-1 L cm-1) 425 (3.2 ꢀ 105), 561
(2.0 ꢀ 104), 600 (1.3 ꢀ 104). Anal. Calcd. for C75H67N5O10Sn: C,
68.39; H, 5.13; N, 5.32. Found: C, 68.28; H, 5.11; N, 5.30.
MALDI-TOF MS: m/z obsd 1318.36, calcd 1318.19 [(MþH)þ;
M=C75H67N5O10Sn].
Compound 4. To a solution of 32 (42.1 mg, 0.055 mmol, 1
equiv) in dry chloroform (18 mL) was added dropwise under
argon a solution of 8 (30.2 mg, 0.060 mmol, 1.1 equiv) in dry
chloroform (34 mL). The resulting mixture was stirred at RT
during 4 days. The reaction was monitored by 1H NMR. After
removal of the solvent, the resulting powder was recrystallized
by slow diffusion of n-hexane into a toluene solution of 4
affording a crystalline dark red powder (62 mg, 92%). Single
crystals suitable for X-ray diffraction were grown by vapor
diffusion of n-hexane into a toluene solution containing the
compound. 1H NMR (CDCl3, 300 MHz): δ 1.33 (t, 4J=2.3 Hz,
2H, CHres), 1.55 (dd, 3J=7.9 Hz, 4J=1.8 Hz, 2H, CHres), 3.15
(m, 4H, CH2O), 3.48 (m, 4H, CH2O), 3.65 (m, 4H, CH2O), 3.75
(m, 4H, CH2O), 4.76 (s, 4H, ArCH2), 5.35 (ddd, 3J=8.0 Hz, 4J=
2.4 Hz, 4J=0.9 Hz, 2H, CHres), 5.51 (t, 3J=8.0 Hz, 2H, CHres),
7.45 (d, 3J=7.6 Hz, 2H, CHPy), 7.70 (t, 3J=7.6 Hz, 1H, CHPy),
7.78 (m, 12H, CHPh meta/para), 8.20 (m, 8H, CHPh ortho), 9.03 (s,
Anal. Calcd. for C68H60N4O9Sn H2O: C, 67.22; H, 5.11; N,
3
4.61. Found: C, 67.29; H, 5.19; N, 4.07. MALDI-TOF MS: m/z
obsd 1197.32, calcd 1197.34 [(MþH)þ; M=C68H60N4O9Sn].
X-ray Crystallography. Data (Tables S1 and S2, see the
Supporting Information) were collected on a Bruker SMART
CCD diffractometer with Mo-KR radiation. The structures
were solved using SHELXS-97 and refined by full matrix least-
squares on F2 using SHELXL-97 with anisotropic thermal
parameters for all non hydrogen atoms. The hydrogen atoms
were introduced at calculated positions and not refined (riding
model).
CCDC 755098-755104 contain the supplementary crystal-
lographic data for compounds 3-4, 6, and 35-38. These data
can be obtained free of charge via www.ccdc.cam.ac.uk/
data_request/cif.
8H, CHβ-pyrrolic,
4JSn-H = 12.4 Hz). 13C NMR (CDCl3, 75
MHz): δ 66.4 (CH2O), 69.4 (CH2O), 70.2 (CH2O), 71.0
(CH2O), 74.4 (CH2O), 103.3 (CH), 110.4 (CH), 120.4 (CH),
121.7 (Cquat), 126.2 (CH), 126.9 (CH),128.2 (CH), 129.0 (CH),
132.4 (CH), 134.9 (CH), 137.2 (CH), 141.0 (Cquat), 147.2 (Cquat),
155.8 (Cquat), 157.0 (Cquat), 158.1 (Cquat). UV-vis (CH2Cl2) λ
ꢀ
Acknowledgment. Universite de Strasbourg, International
Centre for Frontier Research in Chemistry (FRC), Strasbourg,
Institut Universitaire de France, the CNRS, and the Ministry of

Article
Inorganic Chemistry, Vol. 49, No. 4, 2010 1883
Education and Research are acknowledged for financial support
and for a scholarship to A.G. Dr. L. Allouche and J.-D. Sauer are
acknowledged for performing the 2-D NMR experiments.
of acids, 1H NMR spectra and Roesy spectra of 1-2 in
the presence of AgOTf, 1H NMR spectra of 3-6 in the
presence of AgOTf, and Tables of 1H NMR chemical
shifts for 1-6 in the presence of AgOTf. This material
is available free of charge via the Internet at http://
pubs.acs.org.
Supporting Information Available: Crystallographic data
1
in CIF format, H NMR Spectra of 35-36 in the presence