A doubly folded spacer in a self-assembled hybrid material

Article abstract of DOI:10.1039/b515260g

The hydrolysis of a bridged α,ω-bis(trialkynylstannylated) compound leads to a hybrid material ordered by self-assembly where the spacer forms two six-membered [1,2]oxastanninane rings by intramolecular coordination. The Royal Society of Chemistry 2006.

Full text of DOI:10.1039/b515260g

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A doubly folded spacer in a self-assembled hybrid material{
Hicham Elhamzaoui,a Bernard Jousseaume,*a Thierry Toupance,a Ce´cile Zakri,b Monique Biesemans,c
Rudolph Willemc and Hassan Allouchid
Received (in Cambridge, UK) 31st October 2005, Accepted 25th January 2006
First published as an Advance Article on the web 13th February 2006
DOI: 10.1039/b515260g
types: alkylene, arylene or mixed arylene–alkylene. This self-
assembly occurred spontaneously, without the use of surfactants.
The comparison of the tin–tin distances obtained from the crystal
structures of suitable starting compounds and the distances
between the polystannoxane walls showed that the latter
corresponded to fully extended spacers, as was observed in the
case of silicon-based hybrid materials with alkylene or mixed
alkylene–phenylene spacers.6 The work reported here describes the
preparation and a structural study of a bridged tin-based hybrid
material with a particular focus on the conformation of the spacer
which separates the metal atoms.
The hydrolysis of a bridged a,v-bis(trialkynylstannylated)
compound leads to a hybrid material ordered by self-assembly
where the spacer forms two six-membered [1,2]oxastanninane
rings by intramolecular coordination.
The combination of organic and inorganic components bonded
through a covalent bond at the nanometre scale leads to hybrid
materials with promising applications in various fields such as
coatings, membranes, electronics, optics, etc.1 Silicon-based hybrid
materials received considerable attention as minute changes in the
structure of the starting materials or in the preparation conditions
have a dramatic influence on their physical properties, specific
surface, porosity, texture and morphology.2 This is especially true
for bridged hybrids which, moreover, show the remarkable
property of self-assembly. Depending on the nature of the spacer
between the silicon atoms and on their preparation conditions, the
corresponding hybrids can self-assemble to give ordered materials
with dimensions of up to hundreds of nanometres. This
nanostructuration can be achieved by the use of surfactants and
usually results from the properties of the structure directing agent.3
However, a double organization can be reached with a short scale
one induced by the spacer and a medium scale one induced by the
surfactant.4 Nanostructuration is also possible by running solid
state hydrolysis/polycondensations where the starting materials are
used as templates5 or by the association of the organic bridges by
formation of hydrogen bonds.6 However, a precise picture of the
organization of the organic spacer, as deduced from X-ray data
which allow the measurement of the distance between the
polysiloxane planes, could only be performed in the very rare
cases where it corresponded to a fully extended organic spacer.6
The stability of tin–carbon bonds towards hydrolysis and the
recent development of suitable starting materials,7 alkynides
instead of the alkoxides usually employed in sol–gel chemistry,
has recently allowed the preparation of tin-based hybrid
materials.8 In addition, it was demonstrated that the use of
distannylated precursors leads to organized materials where walls
of polystannoxane units are separated by organic bridges of several
The synthesis of the precursor 4,49-bis(5-(triprop-1-ynylstannyl)-
pentyloxymethyl)biphenyl 2 started from the etherification of
4,49-bis(chloromethyl)biphenyl with but-3-enol, followed by the
hydrostannation of the corresponding diether with tricyclohexyltin
hydride. Electrophilic cleavage of the tricyclohexyltin groups with
tin tetrachloride afforded 4,49-bis(5-(trichlorostannyl)butyloxy-
methyl)biphenyl 1 in 96% yield. Compound 1 was characterized
by 119Sn NMR giving a signal at 2142.2 ppm indicative of strong
coordination of the tin by the oxygen atom in solution. Dilution
studies showed that the coordination was intramolecular and
variable temperature experiments (d 2174 ppm at 280 uC,
295 ppm at 80 uC) revealed that the open form of the trichloride
(a chemical shift of around 25 ppm is expected for uncoordinated
linear alkyl trichloroorganotins) was in fast equilibrium with the
cyclic form at room temperature (21% open form; 79% closed
form). The CP-MAS 119Sn chemical shift (d 2163 ppm) was
indicative of a closed form in the solid state. That was confirmed
by the cyclic conformation of the methylene chains and the short
distance (247 pm) between the tin and the oxygen atom in the
crystal structure of 1, which lies about inversion centers in
the crystal lattice (see Fig. 1).{ A similar distance was measured in
the crystal structure of methyl 3-trichlorostannylpropanoate which
shows the same conformation with a six-membered ring.9 The
hexachloride 1 was then alkynylated with a slight excess of
propynyllithium to give 2. Subsequently, a solution of 2 in THF
was added to a solution of water in THF. After 6 days at room
temperature the mixture was gelated and was aged for 28 days.
The hybrid 3 was filtered, washed with THF and dried at 120 uC
for 3 h under vacuum.
aLaboratoire de Chimie Organique et Organome´tallique, UMR-CNRS
5802, Universite´ Bordeaux 1, 351 cours de la Libe´ration, 33405 Talence,
France. E-mail: b.jousseaume@lcoo.u-bordeaux1.fr; Fax: +33 540006994
bCentre de Recherche Paul Pascal, UPR-CNRS 8641, Avenue A.
Schweitzer, 33600 Pessac, France
The IR spectrum of 3 showed the total disappearance of the
signal at 2166 cm21 characteristic for the triple bond stretching.
The hydrolysis of the tin–propynyl bonds in the starting
compound was thus complete. Microanalysis data and TGA
measurements were consistent with the presence of two tin atoms
per organic bridge, confirming the expected structure of 3. The
BET specific area was low (,2 m2 g21) and was only slightly
increased (12 m2 g21) when the hydrolysis of 2 was conducted
cHigh Resolution NMR Centre, Department of Polymer Science and
Structural Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, 1050
Brussels, Belgium
dLaboratoire de Chimie PhysiqueSPOT, EA 3857, Faculte´ de
Pharmacie, 31 Avenue Monge, 37200 Tours, France
{ Electronic supplementary information (ESI) available: Synthesis and
characterization of 1–3. See DOI: 10.1039/b515260g
1304 | Chem. Commun., 2006, 1304–1306
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The distance found between the polystannoxane walls is far
lower than that expected from a fully extended organic chain (dcalc
= 2.9 nm), the conformation adopted in tin-based hybrids where
the tin atoms are separated by polymethylene spacers.8 In the
present case, the distance lies in the same range as the distance
(dcalc = 1.85 nm) calculated from the measured tin–tin separation
found in 1 (1.60 nm), assuming a fully condensed network of tin
oxide without coordinated water. This result suggests the existence
of tilted organic chains with a tilt angle of about 23u, in the same
range as reported for a tin-based hybrid with a 4,49-dimethylene-
biphenyl spacer (19u) but smaller than the value of 30u reported for
ordered silicon-based hybrid materials.6
Our interpretation of these data is as follows. During the
hydrolysis of uncoordinated 2, substituting the carbon with the
oxygen atoms sufficiently enhances the electrophilicity of the tin
atoms such that a stabilizing coordination expansion at tin by the
oxygen atom of the chains, which are in a suitable position,
becomes possible. This intramolecular coordination leads to the
formation of two additional [1,2]oxastanninane-like six-membered
rings, as demonstrated for 1 in the solid state and even in solution.
Thus, the distance between the tin atoms is reduced by the
formation of these two rings, which leads to the short distance
between the tin oxide walls measured by PXRD. This explanation
is reinforced by the results obtained in the study of the hybrid
material 4 obtained after hydrolysis of 4,49-bis(1-(triprop-1-
ynylstannyl)butyl)biphenyl 5. Its PXRD spectrum showed a peak
at 4.3u corresponding to a distance of 2.01 nm between refractive
planes, while a distance of 2.05 nm was calculated from the crystal
structure of the corresponding hexachloride 6, which lies about
inversion centers in the crystal lattice. Thus, in the case of a non-
coordinating spacer of similar length, the alkylene chains of the
corresponding hybrid are extended, which confirms that the low
distance between the polystannoxane walls in 3 is due to the
specific folding of the side-chains of the spacer (see Scheme 1).
In conclusion, hydrolysis of distannylated alkynides, where the
tin atoms bear labile alkynyl groups and are separated by an
organic chain containing oxygen atoms, leads to a hybrid material
where the spacer is doubly folded by intramolecular coordination.
This remarkable organization appears to be unique in the
Fig. 1 ORTEP rendering of 1 with 60% probability displacement
ellipsoids. Distances between tin and oxygen atoms are indicated, and
highlighted with dashed lines.
under micro-emulsion conditions with Igepal 720 as a surfactant.8
The powder X-ray diffraction (PXRD) of hybrid 3 showed a peak
at low angle (2h = 5.2u) corresponding to a distance of 1.70 nm
between refractive planes (see Fig. 2). This is assigned to the
presence of polystannoxane walls separated by organic bridges.
The size of the ordered domains was between three and four
layers. The same result (2h = 5.2u) was recorded when the
hydrolysis of 2 was conducted in a biphasic medium (toluene
solution of 2–water), which shows that this phenomenon does not
depend on the reaction conditions.
Fig. 2 X-Ray powder diffraction patterns of 3 prepared in THF (thick
Scheme 1 Structural model for hybrid 3.
line) or in toluene (thin line).
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122, 5258; C. Yoshina-Ishii, T. Asefa, N. Coombs, M. J. MacLachlan
and G. A. Ozin, Chem. Commun., 1999, 2539; T. Asefa, M. Kruk,
M. J. MacLachlan, N. Coombs, H. Grondey, M. Jaroniec and G. A. Ozin,
J. Am. Chem. Soc., 2001, 123, 8520; G. Temtsin, T. Asefa, S. Bittner and
G. A. Ozin, J. Mater. Chem., 2001, 11, 3202; M. Kuroki, T. Asefa,
W. Whitnal, M. Kruk, C. Y. Ishi, M. Jaroniec and G. A. Ozin,
J. Am. Chem. Soc., 2002, 124, 13886; K. Landskron and G. A. Ozin,
Angew. Chem., Int. Ed., 2005, 44, 2; J. He, T. Kunitake and T. Watanabe,
Chem. Commun., 2005, 795.
4 S. Inagaki, S. Guan, T. Ohsuna and O. Terasaki, Nature, 2002, 416, 304;
M. P. Kapoor, Q. Yang and S. Inagaki, J. Am. Chem. Soc., 2002, 124,
15176; M. P. Kapoor, Q. Yang and S. Inagaki, Chem. Mater., 2004, 16,
1209; M. P. Kapoor, N. Setoyama, Q. Yang, M. Ohashi and S. Inagaki,
Langmuir, 2005, 21, 443.
chemistry of hybrid materials where linear arrangements of the
spacers have been found in the few cases where the organization
could be determined. This work opens the way to studies on the
modulation of the geometrical properties of hybrid materials by
weak interactions in their organic component.
The authors wish to thank the Aquitaine Region, the CNRS
(Material Program Grant) and the European Community (FAME
network of Excellence) for partial financial support of this work as
well as the Fund for Scientific Research-Flanders (Belgium)
(FWO) (Grant G.0016.02) and the Research Council of the VUB
(Grants GOA31, OZR362 and OZR875).
5 B. Boury and R. J. P. Corriu, Chem. Rec., 2003, 3, 120; F. Ben, B. Boury
and R. J. P. Corriu, Adv. Mater., 2002, 14, 1081; B. Boury, F. Ben and
R. J. P. Corriu, Angew. Chem., Int. Ed., 2001, 40, 2853; B. Boury,
R. J. P. Corriu, V. Le Strat, P. Delord and M. Nobili, Angew. Chem., Int.
Ed., 1999, 28, 3172; F. Ben, B. Boury, R. J. P. Corriu and V. Le Strat,
Chem. Mater., 2000, 12, 3249.
6 J. J. E. Moreau, L. Vellutini, J.-L. Bantignies, M. Wong Chi Man,
C. Bied, P. Dieudonne´ and J.-L. Sauvajol, J. Am. Chem. Soc., 2001, 123,
7957; J. J. E. Moreau, B. P. Pichon, M. Wong Chi Man, C. Bied,
J.-L. Bantignies, P. Dieudonne´ and J.-L. Sauvajol, Angew. Chem., Int.
Ed., 2004, 43, 203; J. J. E. Moreau, L. Vellutini, M. Wong Chi Man,
C. Bied, P. Dieudonne´, J.-L. Bantignies and J.-L. Sauvajol, Chem.–Eur.
J., 2005, 11, 1527.
Notes and references
¯
{ Crystal data for 1 : C22H28Cl6O2Sn2, Mr = 774.57, triclinic, P1, a =
7.0738(2), b = 7.4590(2), c = 14.2470(6) s, a = 101.473(1), b = 91.444(1), c
= 105.224(1)u, V = 708.46(4), Z = 1, rcalc =1.815 g cm23. Data collection:
Kappa-CCD area detector, Mo-Ka radiation, T = 150 K, 3192 unique
reflections, 2901 observed (I > 2s(I)), Rint = 0.0166, hmax = 27.5u. Structure
solved by direct methods and refined by full-matrix least-squares on
F2(SHELX-97), 146 parameters, R1 = 0.0247, wR2 = 0.0557. CCDC
288987.
¯
Crystal data for 6 : C20H24Cl6Sn2, Mr = 714.51, triclinic, P1, a =
6.616(3), b = 8.932(11), c = 10.654(8) s, a = 90.03(7), b = 90.44(5), c =
99.49(5)u, V = 621.0(9), Z = 1, rcalc = 1.911 g cm23. Data collection:
Kappa-CCD area detector, Mo-Ka radiation, T = 170 K, 1744 unique
reflections, 1571 observed (I > 2s(I)), Rint = 0.0871, hmax = 26.37u.
Structure solved by direct methods and refined by full-matrix least-squares
on F2(SHELX-97), 126 parameters, R1 = 0.0468, wR2 = 0.1185. Seven
aromatic bonds, the Sn–O bond and a C–C aliphatic bond were restrained
during the refinement. CCDC 288988. For crystallographic data in CIF or
other electronic format see DOI: 10.1039/b515260g
7 B. Jousseaume, M. Lahcini, M.-C. Rascle, C. Sanchez and F. Ribot,
Organometallics, 1995, 14, 685; B. Jousseaume, M. Lahcini, E. Fouquet
and B. Barbe, J. Org. Chem., 1994, 59, 8292; M. Biesemans, R. Willem,
S. Damoun, P. Geerlings, M. Lahcini, P. Jaumier and B. Jousseaume,
Organometallics, 1996, 15, 2237; P. Jaumier, B. Jousseaume, M. Lahcini,
F. Ribot and C. Sanchez, Chem. Commun., 1998, 369; M. Lahcini,
P. Jaumier and B. Jousseaume, Angew. Chem., Int. Ed., 1999, 38, 402;
B. Jousseaume, H. Riague, T. Toupance, M. Lahcini, P. Mountford and
B. R. Tyrrell, Organometallics, 2002, 21, 4590.
8 H. Elhamzaoui, B. Jousseaume, H. Riague, T. Toupance, P. Dieudonne´,
C. Zakri, M. Maugey and H. Allouchi, J. Am. Chem. Soc., 2004, 126,
8130.
1 Functional Hybrid Materials, ed. P. Go´mez-Romero and C. Sanchez,
Wiley-VCH, Weinheim, Germany, 2003.
2 K. J. Shea, D. A. Loy and O. Webster, J. Am. Chem. Soc., 1992, 114,
6700; H. W. Oviatt, K. J. Shea and J. H. Small, Chem. Mater., 1993, 5,
943; D. A. Loy and K. J. Shea, Chem. Rev., 1995, 95, 1431.
3 C. T. Kresge, M. E. Leonowicz, W. J. Roth, J. C. Vartuli and J. S. Beck,
Nature, 1992, 359, 710–712; Y. Lu, H. Fan, N. Doke, D. A. Loy,
R. A. Assink, D. A. LaVan and C. J. Brinker, J. Am. Chem. Soc., 2000,
9 R. A. Howie, E. S. Paterson, J. L. Wardell and J. W. Burley,
J. Organomet. Chem., 1983, 259, 71. See also: P. Jaumier,
B. Jousseaume, E. R. T. Tiekink, M. Biesemans and R. Willem,
Organometallics, 1997, 16, 5124; M. Biesemans, R. Willem, S. Damoun,
P. Geerlings, E. R. T. Tiekink, M. Lahcini, P. Jaumier and
B. Jousseaume, Organometallics, 1998, 17, 90.
1306 | Chem. Commun., 2006, 1304–1306
This journal is ß The Royal Society of Chemistry 2006