Synthesis of supramolecular cyclosiloxane ligands

Article abstract of DOI:10.1016/j.mencom.2009.03.007

The synthesis and properties of new polypodand ligands based on benzene or pyridine molecules, as well as their calix-shape derivatives, formed by the partial hydrolysis of pre-organized supramolecules are presented.

Full text of DOI:10.1016/j.mencom.2009.03.007

Mendeleev
Communications
Mendeleev Commun., 2009, 19, 75–77
Synthesis of supramolecular cyclosiloxane ligands
·
Blazej Gierczyk* and Grzegorz Schroeder
Faculty of Chemistry, Adam Mickiewicz University, 60-780 Poznan´, Poland. Fax: +48 61 8291 505;
e-mail: hanuman@amu.edu.pl, schroede@amu.edu.pl
DOI: 10.1016/j.mencom.2009.03.007
The synthesis and properties of new polypodand ligands based on benzene or pyridine molecules, as well as their calix-shape
derivatives, formed by the partial hydrolysis of pre-organized supramolecules are presented.
Podands make a large and important group of supramolecuar
ligands. Their properties could be designed via changing the
length, structure and flexibility of complexing arms (especially
the number of donor atoms and the hydrophobicity) or the
character and geometry of the ‘clipping’ centre (an atom or
group to which the arms are connected).1 This class of ligands
is especially interesting and important for industry, nanotech-
nology and laboratory applications because of low cost, simple
and fast synthesis and high versatility. Previously, we described
methods of synthesis of di- and tri(oxaalkyl) phosphates, tri(oxa-
alkyl) borates, bis(oxaalkyl) sulfates and di- and tri(oxaalkyl)
silicon podands. NMR, FTIR and calorimetric methods have
been used to study metal cation complexation. These ligands
form cation channels or cavities. In the FTIR spectra of these
complexes, the fast fluctuation of the cation was indicated
by a characteristic continuous absorption.2–6 In the reaction
of perfluoroarenes with sodium tris(alcoxysilyl)alkyl thiolate,
interesting new octopus-like polypodands could be obtained.
Their partial hydrolysis followed by spontaneous Si–O–Si bond
formation produces a cavity molecule of ionophore character.
OMe
O
Si(OMe)3
MeO
Si
O
O
(MeO)3Si
Si
O
O
O
Si
Si
O
O
O
O
S
S
S
S
O
OMe
O
Si
Si
O
S
S
S
S
Si(OMe)3
S
S
S
S
Si
O
O
H2O
O
Si
Si
(MeO)3Si
Si
MeO
S
S
S
S
O
S
S
Si(OMe)3
Si
OMe
Si(OMe)3
Si
O
MeO
1
5
F
F
(MeO)3SiCH2CH2CH2SNa
F
F
F
F
(MeOCH2CH2O)3SiCH2CH2CH2SNa
MeO
OMe
O
OMe
MeO
O
O
O
O
MeO
O
Si
MeO
O
OMe
O
Si
O
O
OMe
O
Si
Si
O
O
OMe
OMe
O
O
O
Si
O
O
O
S
O
S
S
O
OMe
OMe
O
O
S
S
S
S
S
S
Si
O
S
S
O
O
Si
Si
H2O
O
O
O
MeO
O
O
Si
Si
Si
O
OMe
O
O
S
O
Si
S
Si
O
O
MeO
O
Si
O
MeO
O
O
Si
Si
S
S
S
Si
O
O
Si
OMe
MeO
OMe
O
O
OMe
OMe
S
O
O
S
OMe
MeO
OMe
2
6
Scheme 1 Synthesis of hexakis[3-(trimethoxysilyl)propylthio]benzene 1, hexakis{3-[tris(2-methoxyethoxy)silyl]propylthio}benzene 2 and their partial
hydrolysis to cavity molecules 5 and 6.
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© 2009 Mendeleev Communications. All rights reserved.

Mendeleev Commun., 2009, 19, 75–77
OMe
O
Si(OMe)3
Si
MeO
Si
O
O
(MeO)3Si
O
O
O
Si
Si
O
O
O
S
S
O
OMe
O
Si
O
S
S
S
S
Si(OMe)3
S
S
S
S
Si
O
O
H2O
O
Si
Si
(MeO)3Si
N
Si
N
MeO
OMe
S
S
S
N
S
S
Si(OMe)3
Si
3
MeO
OMe
7
F
(MeO)3SiCH2CH2CH2SNa
F
F
F
F
N
(MeOCH2CH2O)3SiCH2CH2CH2SNa
MeO
OMe
O
OMe
OMe
MeO
O
O
O
O
MeO
O
Si
MeO
O
O
Si
O
O
OMe
O
Si
Si
O
OMe
OMe
O
O
O
Si
O
O
O
S
O
S
O
OMe
OMe
O
O
O
S
S
S
S
S
S
Si
O
S
S
O
O
Si
Si
H2O
O
O
O
MeO
O
Si
Si
N
N
O
OMe
O
O
O
Si
Si
O
O
O
O
MeO
O
Si
O
MeO
O
Si
Si
OMe
S
S
O
O
OMe
MeO
OMe
N
S
S
S
MeO
OMe
4
8
Scheme 2 Synthesis of pentakis[3-(trimethoxysilyl)propylthio]pyridine 3 and pentakis{3-[tris(2-methoxyethoxy)silyl]propylthio}pyridine 4 and their
partial hydrolysis to cavity molecules 7 and 8.
The octopus-like polypodands were obtained in the reaction
of sodium thiolates with perfluoroarenes.† The structures of
ligands obtained are presented in Schemes 1 and 2; 1H, 13C and
29Si NMR data of the ligands are collected in Tables 1 and 2
and in a footnote.‡ For all compounds, no 19F NMR signal of the
C–F fluorine atom was detected (only a weak line of the F– ion
occurred in the spectra of some samples). Elemental analysis
results of the calix-like compounds obtained are not satisfactory
(errors of 0.2–0.6%). It is probably caused by solvent encapsula-
tion or the complexation of sodium fluoride.‡ In the IR spectra
of compounds 1–4, the absence of absorption characteristic of
C–F and S–H bonds was confirmed. Hydrolysis and cyclization
during the formation of 5, 6 caused a decrease in Si–O–C (1090
and 820 cm–1) and SiOC–H (2840 cm–1) bands and the appearance
Table 1 1H NMR chemical shifts for compounds 1–8.
1H NMR, d/ppm
Compound
SCH2
CH2CH2CH2
CH2Si
OMe
SiOCH2
—
3.71 (m, 36H) 3.48 (m, 36H)
CH2OMe
1
2
3
4
5
6
7
8
2.65 (t, 12H)
2.63 (t, 12H)
2.71 (t, 4H), 2.62 (t, 6H)
2.70 (t, 4H), 2.63 (t, 6H)
2.70 (br., 12H)
2.70 (br. t, 12H)
2.70 (br., 4H), 2.60 (br., 6H)
2.70 (br., 4H), 2.60 (br., 6H)
1.74 (q,a 12H)
1.74 (q, 12H)
1.73 (m, 10H)
1.74 (m, 10H)
1.70 (br., 12H)
1.70 (br., 12H)
1.70 (br., 10H)
1.70 (br., 10H)
0.75 (t, 12H)
0.75 (t, 12H)
0.76 (t, 10H)
0.75 (t, 10H)
0.65 (br., 12H)
0.65 (br., 12H)
3.60 (s, 54H)
3.25 (s, 54H)
3.58b (s, 45H)
3.26 (s, 45H)
3.60 (br., 18H)
3.28 (s, 18H)
—
—
—
3.72 (m, 30H) 3.48 (m, 30H)
—
3.65 (m, 12H) 3.45 (m, 12H)
—
—
0.64b (br., 10H) 3.28b (br. s, 21H)
—
0.66b (br., 10H) 3.27 (s, 12H), 3.25 (br. s, 9H) 3.66; m, 14 H
3.43; m, 14H
aq – quintet. bPartly resolved into two lines.
Table 2 13C NMR chemical shifts for compounds 1–8.
13C NMR, d/ppm
Compound
SCH2
CH2CH2CH2
SiCH2
SiOCH2
CH2CH2OMe
OMe
‘core’ carbons
1
2
3
4
5
6
7
8
35.82
35.82
33.19, 35.70, 35.78
33.18, 35.70, 35.76
35.71
35.68
31.95, 33.73, 33.84
31.98, 33.71, 33.84
28.27
28.30
28.28, 27.93
28.25, 27.90
28.23
28.22
27.27, 26.63
27.20, 26.59
8.35
9.39
8.35, 8.29
9.27, 9.31
8.18
9.21
7.78, 8.03
8.64, 8.99
—
61.72
—
61.68, 61.79
—
61.77
—
73.69
—
73.68
—
73.72
—
51.40
58.43
51.40, 51.25
58.44
51.23
58.70
51.18, 51.23
58.11, 58.61
148.32
148.30
169.23, 159.11, 130.89
169.23, 159.12, 130.90
147.02
147.19
167.76, 159.00, 130.67
167.72, 159.01, 130.67
—
61.72, 61.84
73.12, 73.99
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Mendeleev Commun., 2009, 19, 75–77
of strong bands at 1060 and 890 cm–1, characteristic of Si–O–Si
compounds.
2
6 M+
Partial hydrolysis of compounds 1–4 produces calix-like
molecules. Unfortunately, the tendency to vitrification of pro-
ducts precludes obtaining them in crystalline form and ipso
MeO
MeO
O O
†
OMe MeO
O O
The NMR spectra were recorded at 293 K on a Varian Gemini 300
spectrometer using standard sequences and parameters. The 1H, 13C,
19F and 29Si NMR measurements were carried out in [2H8]THF, while
O
Si
MeO
MeO
1
the 23Na NMR spectra were measured in [2H3]acetonitrile. For H and
O
OMe
Si
29Si NMR spectra internal tetramethylsilane, for 19F – internal CFCl3
and for 23Na NMR external 1 M solution of NaCl in D2O were used as
standards. Because of poor solubility, in all cases saturated samples were
used. For ESI-MS spectra, a Waters/Micromass (Manchester, UK) ZQ
mass spectrometer equipped with a Harvard Apparatus syringe pump was
used. The sample solutions were prepared in acetonitrile at a concentra-
tion of 5×10–5 mol dm–3. The samples were infused into the ESI source
at a flow rate of 40 μl min–1. The ESI source potentials were 3 kV on
capillary, 0.5 kV on lens, 4 V on extractor and 40 V as cone voltage. The
source and desolvation temperatures were 120 and 300 °C, respectively.
Nitrogen was used as a nebulizing and desolvation gas at flow rates of
100 and 300 dm3 h–1, respectively. Elemental analysis was performed on
a Vario EL III (Elementar, USA) analyser.
O
S
S
S
O
Si
MeO
OMe
O
S
S
O
MeO
Si
O
OMe
S
O
O
Si
O O
MeO
OMe
Si
O
OMe
O O
MeO
MeO
MeO
OMe
All compounds used for synthesis were dried and deoxygenated by
standard procedures.
Scheme 3 Complexation of M+ ions by octopus-like Si podands.
General method of synthesis of hexakis/pentakis 3-trialkoxysilylpropylthio
benzene/pyridine 1–4. To 0.06 mol of 3-(trialkoxysilyl)propanethiol
dissolved in anhydrous THF (50 ml), 0.07 mol of NaH was added. The
suspension was vigorously mixed for 25 min (until hydrogen release
had stopped) and then 0.01 mol of hexafluorobenzene (or 0.012 mol of
pentafluoropyridine) in anhydrous THF (10 ml) was added dropwise.
After 24 h, the sodium fluoride precipitate was separated by centrifuga-
tion and the solvent was evaporated in a vacuum. The glassy residue was
dried in a vacuum at 325 K. The yields of octopus-like compounds were
above 95%, purity > 85% (NMR).
General procedure of the partial hydrolysis of compounds 1–4. To
0.01 mol of hexakis[3-(trialkoxysilyl)propylthio]benzene or pentakis-
[3-(trialkoxysilyl)propylthio]pyridine dissolved in 100 ml THF, a mixture
of water (0.06 or 0.05 mol, respectively) in 100 ml THF was added. The
solution was vigorously stirred for 10 h and the solvent was evaporated
in a vacuum. The compounds were obtained as glassy solids. After evapora-
tion, further dissolution was very difficult. The yield of the compounds
was above 95%, purity > 80% (NMR, MS).
facto their X-ray analysis. Additionally, the presence of some
impurities in the synthesized samples makes it difficult to
confirm their structures. Therefore, structures 5–8, presented in
Schemes 1 and 2 are only propositions (e.g., for 5 and 6 the
formation of isomers containing two six-membered trisiloxane
rings with a benzene ring between them is possible). Although
the formation of oligomers and some non-organized species
during hydrolysis is possible, the preferable intramolecular
cyclization could be clearly confirmed by ESI-MS measurements;‡
the signals corresponding to the proposed structures are the
major ones in the spectra. Preorganisation of an octopus-like
molecule before hydrolysis is probably caused by metal ions
existing in solution as impurities.
The 23Na NMR spectra of the mixtures of compounds 1–8
with NaClO4 (1:2 L/M+ molar ratio)‡ have confirmed the com-
plexing properties of the ligands. Compounds 1–4 due to the
presence of five or six ions binding areas could form complexes
of higher stoichiometry (up to 1:5 or 1:6, respectively; Scheme 3).
Low values of complexation induced shifts (CIS) for compounds
1 and 3 result from the structure of the ligand arms. The Si–O
group oxygen atoms are relatively ineffective as donors and, con-
sequently, Na+ ion binding constants are low. Compounds 2 and
4 form much stronger complexes with the ions due to the presence
of ether oxygen atoms in their structure.
‡
For 1: 29Si NMR, d: –60.29. Found (%): C, 40.62; H, 7.31; S, 15.40.
Calc. for C42H90O18S6Si6 (%): C, 40.55; H, 7.29; S, 15.46. 23Na NMR
for 1 + NaClO4, d: –6.32.
For 2: 29Si NMR, d: –61.92. Found (%): C, 46.03; H, 8.09; S, 9.36.
Calc. for C78H162O36S6Si6 (%): C, 45.99; H, 8.02; S, 9.44. 23Na NMR for
2 + NaClO4, d: –6.24.
For 3: 29Si NMR, d: –59.99, –60.11, –60.56. Found (%): C, 40.08;
H, 7.27; N, 1.30; S, 15.22. Calc. for C35H75NO15S5Si5 (%): C, 40.01;
H, 7.19; N, 1.33; S, 15.26. 23Na NMR for 3 + NaClO4, d: –6.32.
For 4: 29Si NMR, d: –60.09, –61.17. Found (%): C, 46.02; H, 8.19;
N, 0.77; S, 9.20. Calc. for C65H135NO30S5Si5 (%): C, 45.62; H, 7.95; N, 0.82;
S, 9.37. 23Na NMR for 4 + NaClO4, d: –6.23.
This work was supported by the Polish Ministry of Science
and Higher Education (grant no. R0501601, 2006–2008).
For 5: 29Si NMR, d: –68.78. Found (%): C, 37.50; H, 5.77; S, 19.51.
Calc. for C30H54O12S6Si6 (%): C, 37.24; H, 5.62; S, 19.88. 23Na NMR for
References
5 + NaClO4, d: –6.28. MS (ESI), m/z: 504.0 [C30H54S6O12Si6Na2]2+
=
[L + 2Na+].
1 E. Weber, in Encyclopædia of Supramolecular Chemistry, eds. J. L.
Atwood and J. W. Steed, Marcel Dekker Inc., New York, 2004, vol. 2,
p. 1106.
2 B. Le¸ska, R. Pankiewicz, G. Schroeder, B. Gierczyk and H. Maciejewski,
Catal. Commun., 2007, 9, 821.
3 B. Le¸ska, B. Gierczyk, K. Eitner, V. Rybachenko and G. Schroeder,
Supramol. Chem., 2004, 16, 303.
4 B. Gierczyk, B. Le¸ska, B. Brzezinski and G. Schroeder, Supramol. Chem.,
2002, 14, 497.
5 G. Schroeder, B. Gierczyk, B. Le¸ska, G. Wojciechowski, R. Pankiewicz,
For 6: 29Si NMR, d: –69.56. Found (%): C, 41.33; H, 6.71; S, 15.34.
Calc. for C42H78O18S6Si6 (%): C, 40.95; H, 6.38; S, 15.62. 23Na NMR for
6 + NaClO4, d: –6.20. MS (ESI), m/z: 638.0 [C42H78O18S6Si6Na2]2+
=
[L + 2Na+].
For 7: 29Si NMR, d: –67.90, –68.01. Found (%): C, 37.47; H, 6.00; N,
1.58; S, 18.45. Calc. for C27H51NO11S5Si5 (%): C, 37.43; H, 5.93; N,
1.62; S, 18.50. 23Na NMR for 7 + NaClO4, d: –6.29. MS (ESI), m/z: 455.5
[C27H51NO11S5Si5Na2]2+ = [L + 2Na+], 444.5 [C27H52NO11S5Si5Na]2+
[L + Na+ + H+].
=
B. Brzezinski and F. Bartl, J. Mol. Struct., 2002, 9, 607.
For 8: 29Si NMR, d: –68.20, –69.01. Found (%): C, 42.15; H, 7.00;
N, 1.09; S, 13.49. Calc. for C41H79NO18S5Si5 (%): C, 41.92; H, 6.78; N, 1.19;
S, 13.65. 23Na NMR for 8 + NaClO4, d: –6.20. MS (ESI), m/z: 609.5
·
6 B. Gierczyk, G. Schroeder, G. Wojciechowski, B. Rózalski, B. Brzezinski
and G. Zundel, Phys. Chem. Chem. Phys., 1999, 1, 4897.
[C41H79NO18S5Si5Na2]2+ = [L + 2Na+], 598.5 [C41H80NO18S5Si5Na]2+
[L + Na+ + H+].
=
Received: 1st August 2008; Com. 08/3197
– 77 –