DOI: 10.1002/chem.201403136

Full Paper

& Silica Materials

A General Method for Preparing Bridged Organosilanes with Pendant Functional Groups and Functional Mesoporous Organosilicas Kristy´na Brglov,[a, b] Achraf Noureddine,[a] Jana Hodacˇov,[b] Guillaume Toquer,[c] Xavier Catton,*[a, d] and Michel Wong Chi Man*[a]

Abstract: New organosilica precursors containing two triethoxysilyl groups suitable for the organosilica material formation through the sol-gel process were designed and synthesised. These precursors display alkyne or azide groups for attaching targeted functional groups by copper-catalysed azide–alkyne cycloaddition (CuAAC) and can be used for the preparation of functional organosilicas following two strategies: 1) the functional group is first appended by CuAAC under anhydrous conditions, then the functional material is prepared by the sol-gel process; 2) the precursor is first subjected to the sol-gel process, producing porous, clickable bridged silsesquioxanes or periodic mesoporous organosilicas (PMOs), then the desired functional groups are attached by means of CuAAC. Herein, we show the feasibility of both approaches. A series of bridged bis(triethoxysilane)s with dif-

Introduction Over the past years, organosilicas have attracted considerable interests owing to the numerous applications that result from the combined properties of the inorganic matrix and the functional organic groups.[1] Among the important fields where [a] Dr. K. Brglov,+ A. Noureddine,+ Dr. X. Catton, Dr. M. Wong Chi Man Institut Charles Gerhardt Montpellier (UMR 5253 CNRS-UM2-ENSCM-UM1) 8, rue de l’cole normale, 34296 Montpellier (France) E-mail: [email protected] [email protected]

ferent pending organic moieties was prepared, demonstrating the compatibility of the first approach with many functional groups. In particular, we demonstrate that organic functional molecules bearing only one derivatisation site can be used to produce bridged organosilanes and bridged silsesquioxanes. In the second approach, clickable PMOs and porous bridged silsesquioxanes were prepared from the alkyne- or azide-containing precursors, and thereafter, functionalised with complementary model azide- or alkyne-containing molecules. These results confirmed the potential of this approach as a general methodology for preparing functional organosilicas with high loadings of functional groups. Both approaches give rise to a wide range of new functional organosilica materials.

such hybrid materials are applied, supported catalysis,[2] controlled drug delivery,[3] extraction of pollutants,[4] selective uptake of rare earth metals,[5] luminescence[6] and sensing[7] are being intensively developed. Class II organosilicas,[8] in which the organic functionality is covalently linked to the siloxane network through stable SiC bonds are easily accessible and can be formed by four main routes (Scheme 1):[1–2]

[b] Dr. K. Brglov,+ Prof. J. Hodacˇov Department of Organic Chemistry Institute of Chemical Technology, Technick 5 16628 Praha 6 (Czech Republic) [c] Dr. G. Toquer Institut de Chimie Sparative de Marcoule (UMR 5257 CEA-CNRS-UM2-ENSCM) BP17171, 30207 Bagnols sur Cze (France) [d] Dr. X. Catton Univ. Grenoble Alpes, Inst NEEL F-38042 Grenoble (France) and CNRS, Inst NEEL, F-38042 Grenoble (France)

Scheme 1. Common routes to class II functional organosilicas.

+

[ ] These two authors contributed equally to this work. Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201403136. Chem. Eur. J. 2014, 20, 10371 – 10382

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Full Paper 1) The grafting of organo(trialkoxy)silanes on a preformed silica support. This synthetic method is the most commonly used for functionalising porous silicas including mesostructured MCM-41 and SBA-15 type materials[9] by reaction of the organo(trialkoxy)silane with the surface silanols. 2) The co-condensation reaction between a silica source (for example, TMOS, TEOS) and a functional organo(trialkoxy)silane, with or without structure-directing agents.[10] 3) The hydrolysis/condensation of bridged organo(trialkoxy)silanes, yielding the so-called bridged silsesquioxanes,[11] that inherently feature a high loading and a homogeneous distribution of the organic fragments within their structure. In this case no silica source is needed for the formation of an insoluble solid hybrid silica. In this family of hybrids, periodic mesoporous organosilicas (PMOs)[12] constitute a particular case of bridged silsesquioxanes, which are obtained by the hydrolysis/condensation of bridged precursors in the presence of structure-directing agents and are being developed for important applications.[12–13] 4) Post-synthetic reactions at the surface of functionalisable organosilicas. High yielding and selective click reactions, such as addition of amines to isocyanates or isothiocyanates, radical addition of thiols to alkenes or the coppercatalysed azide–alkyne cycloaddition (CuAAC),[14] are required to optimise the potential properties of these materials.[15] The latter reaction is very promising as it allows a fully regioselective coupling,[16] under mild conditions, of a wide variety of functional fragments, such as simple molecules, dyes, biomolecules or polymer fragments. “Clickable” SBA-15-N3 materials were first reported in 2009 for applications in catalysis[17] or covalent encapsulation of biomolecules.[18] They were obtained by the co-condensation method using tetraethylorthosilicate (TEOS) as silica source and (3-azidopropyl)triethoxysilane (AzPTES), for the clickable part, in the presence of the Pluronic P123 block copolymer as a structure-directing agent. Indeed, the CuAAC reaction on silica supports is carried out at room temperature and has proven to be almost quantitative. Moreover, the co-condensation strategy used to generate the clickable materials enables a homogeneous spatial distribution of the clickable azide fragments for low loadings of AzPTES, which is not achieved by the conventional grafting method.[17b] This approach was later used to generate functionalisable glasses, mesoporous silica nanoparticles and microdots arrays[19] particularly for extraction of radionuclides,[20] controlled drug delivery [3] and diagnosis. Even with a loading of 10 % AzPTES in the initial sol, the click reaction with a pyrene derivative was quantitative, thus showing the high potential of CuAAC as a post-synthesis functionalisation approach.[19a] Sols containing clickable organosilanes can also be processed by spin- or dip-coating as well as ink-jet printing, for applications as biosensors.[19c] In all these studies, the organosilanes used were nonetheless only monosilylated and were employed either in the co-condensation or grafting method. As previously mentioned, these two methods do not allow a high and regular loading of the Chem. Eur. J. 2014, 20, 10371 – 10382

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organic functions and thus polysilylated precursors, which lead to bridged silsesquioxanes upon hydrolysis/condensation, are suitable to reach this goal. We recently developed a very efficient synthesis of organo(triethoxy)silanes using CuAAC under anhydrous conditions from monosilylated azides or alkynes.[21] Although several polysilylated compounds have been synthesised through this cycloaddition reaction, this approach may somehow be limited to polyazide- or to polyalkyne-containing compounds (which are hazardous and may cause explosion or polymerisation). Moreover, the formation of PMOs, which are currently being developed for demanding applications,[12–13, 22] is known to be disfavoured with organo-bridged silanes bearing voluminous organic units. To achieve this goal, we envisioned the synthesis of a new series of clickable organobis(triethoxysilane)s and to investigate the potential of the CuAAC reaction to obtain clicked bridged organosilanes as new sol-gel precursors for functional bridged silsesquioxanes and, more interestingly, to provide a general method for the synthesis of clickable PMOs. Herein, we first describe the synthesis of clickable bridged organosilanes and their conversion into other new bridged organosilanes bearing pending functional groups by the CuAAC reaction (path A, Scheme 2), which are potential

Scheme 2. Overall synthetic scheme for the formation of functional bridged silsesquioxanes.

precursors for the formation of bridged silsesquioxanes with tuneable properties according to the previously clicked organic functions (path B). We then describe the synthesis and functionalisation of pure, clickable PMOs and related mesoporous bridged silsesquioxanes (path C then D) that inherently feature a very high loading of clickable fragments.[23]

Results and Discussion Paths A and B The preparation of bridged organosilanes by using the previously available methods was only possible when the functionality contained two anchoring groups (Scheme 3). In very specific cases, a ramifying bridged organosilane, such as bis(triethoxysilylpropyl)amine, was used to link organic molecules

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Full Paper functional fragments, such as esters, phosphonate esters, triethoxysilyl groups or even hydroxy-terminated chains, can also be linked, as well as alkylene, PEG or phenylidene bridging units. Finally, interesting functionalities for applications, such as the adenine, thymine, or tartrate fragments, can even be inserted. Once formed using the CuAAC methodology, these organosilane precursors can be hydrolysed and condensed to form hybrid silica materials through the Scheme 3. Two approaches for the synthesis of bridged organosilane precursors by sol-gel process. Solid, well cross-linked materials can using CuAAC. be obtained, even when the organic function is anchored through only one appendage. As a representative example, compound 4 c bearing the thymine function was bearing a single anchoring site.[24] We thus decided to broaden hydrolysed in ethanol using three equivalents of water per silithe scope of this strategy by using the CuAAC synthesis of con atom, under nucleophilic catalysis (4 c/H2O/NH4F = 1:6:0.03 organo(alkoxy)silanes[21] (Scheme 3). We designed new compound 1, whose structure is close to at 1 m in ethanol) at room temperature (Scheme 5).[25] A white N,N-bis(propargyl)triethoxysilylpropylamine, which we previgel was obtained after 12 h, which was aged for 48 h, then ously introduced,[21a] but consisting of a single propargyl funcworked up and dried. The resulting material, M-Thy, obtained as a powder, exhibits the typical IR broad band of a siloxane tion connected to two propyl(triethoxysilyl) groups through network (1000–1100 cm1) and the signature of the thymine a nitrogen atom (Scheme 4). This compound can be obtained functions (1677 cm1; see the Supporting Information, Figure S1). As evidenced by scanning electron microscopy (SEM), the powder consists of small aggregated nanoparticles (70-100 nm), as is often observed for bridged silsesquioxanes formed under nucleophilic catalysis (see the Supporting Information, Figure S2). Furthermore, N2 sorption revealed a very low porosity with a Brunauer–Emmett–Teller (BET) specific surface area of ca 38 m2 g1 (see the Supporting Information, Figure S3). Indeed, as already reportScheme 4. Preparation of clickable bridged organosilanes 1, 2 and 2’.

from the commercially available bis(triethoxysilylpropyl)amine, which can be transformed, as previously described, by reaction with propargyl bromide in the presence of CaH2 in THF.[21a] Interestingly, this compound can be safely prepared on a large scale (50 g) and purified by distillation under reduced pressure. Next, the complementary retrosynthesis was envisioned: bissilylated azide derivatives 2 and 2’ were synthesised (Scheme 4, n = 0 or 1). In this case, the alkylation was successful by using 1-azido-2-iodoethane or 1-azido-3-iodopropane with K2CO3 as a base, full conversions being achieved after 16 h in refluxing acetonitrile (Scheme 4). The CuAAC reactivity was then checked by using the previously optimised conditions. CuAAC usually proceeds with full conversion using 0.5 % molar equivalent of copper catalyst [CuBr(PPh3)3] in a dry THF/Et3N mixture at room temperature over 24 h, or, more interestingly, at 100 8C by using microwave irradiation (Pmax = 200 W) in only 5 min.[21] The products were isolated after removal of the solvent and elimination of the copper salts by extraction with pentane. Table 1 and Table 2 exemplify the possible formation of bridged organosilanes bearing a functional pending chain by using both synthetic approaches. Similar to our previous results on monosilylated compounds, full conversions with almost quantitative yields are obtained with a wide variety of structures and functionalities. Indeed, simple benzyl and hexyl groups can be inserted; Chem. Eur. J. 2014, 20, 10371 – 10382

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Scheme 5. Direct sol-gel synthesis of material MThy from 4 c.

ed, bridged silsesquioxanes are mostly obtained as non-porous materials, while the formation of porous networks in these materials has only been reported in few cases by using external templates.[12] Thus, to obtain porous functional bridged silsesquioxanes, a diversity-oriented synthesis starting from a single clickable PMO should be preferred. Path C and D The synthesis of porous, functional organosilicas, such as PMOs, still remains a challenge in materials chemistry. Indeed, whereas much effort has been devoted to the synthesis of mesoporous silica materials featuring different textures and morphologies, much less work has dealt with the formation of porous organosilicas, the preparation of such materials being

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Full Paper Table 2. CuAAC reaction of bissilylated azide 2 or 2’ with organic alkynes.[a]

Table 1. CuAAC reaction of bissilylated alkyne 1 with organic monoazides.[a]

Entry Product

1[b]

Product

Yield [%]

3 a 94

2[c]

3 b 95

3[d]

3 c 95

4

3 d 92

5[e]

3 e 97

6[d]

3 f 94

7[e]

3 g 91

8[d]

3 h 87

9[e]

Entry

Yield [%]

1

4a

98

2[b]

4b

91

3

4c

98

4

4d

96

5

4e

91

3 i 91

[a] Reaction conditions: alkyne (2 mmol), azide (2 mmol), [CuBr(PPh3)3] (0.01 mmol), THF/Et3N 1:1 (1 mL), microwave, 100 8C, 5 min. [b] DMF instead of THF. 10[d]

3 j 90

[a] Reaction conditions: alkyne (2 mmol), azide (2 mmol), [CuBr(PPh3)3] (0.01 mmol), THF/Et3N 1:1 (1 mL), microwave, 100 8C, 5 min. [b] 0.005 mmol of [CuBr(PPh3)3], reaction time 24 h at rt. [c] 0.005 mmol of [CuBr(PPh3)3]. [d] Reaction time: 20 min. [e] Reaction time: 10 min. Chem. Eur. J. 2014, 20, 10371 – 10382

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highly dependent on the structure of the starting organosilane. To date, merely small polysilylated compounds are known to produce “pure” PMOs (obtained without co-condensation of other silica sources). Only the rigid aromatic systems rule out this observation[12] and, even in this case, a small amount of added TEOS may be required to stabilise the PMO framework after the removal of the surfactant.[26] Therefore, post-synthetic functionalisation methods can be an alternative to obtain func10374

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Figure 1. FTIR spectra of PMO materials before (a) and after (b) CuAAC functionalisation: (left) alkyne-containing PMO reacting with ethyl 2-azidoacetate; inset: zoom on the n(CH) bands; (right) azide-containing PMO reacting with methyl pent-4-ynoate; inset: zoom on the azide band.

tional, porous materials from a single source of material. The CuAAC post-functionalisation method is a gold standard for incorporating fragile and voluminous organic fragments such as biomolecules or catalysts onto a preformed material, as the reaction can be performed at room temperature under aqueous conditions, which represents a significant progress compared with the conventional grafting method.[15] Therefore, we prepared clickable PMOs through sol-gel synthesis under acidic conditions with sodium cetyl stearyl sulphate (SHS) as external template, as already described for PMOs featuring tertiary amines.[27] The synthesis was performed by using a molar ratio (1 or 2)/HCl/SHS/H2O = 1:2:0.75:1000. After the materials were formed, they were continuously extracted in acidic ethanol, then the free amine group was released by using aqueous ammonia. The finally dried materials were characterised by using elemental analysis,

NMR and vibrational spectroscopies, powder X-ray diffraction, electron microscopies, TGA and N2 sorption analyses. M1 was obtained from precursor 1 featuring the alkyne group. FTIR spectroscopic analysis of M1 (Figure 1) revealed the formation of the siloxane framework, characterised by a typical broad band (1000–1200 cm1). The efficient removal of the surfactant is evidenced from the comparison of the materials before and after acidic extraction. Furthermore, the alkyne CspH vibration gives a typical absorption at 3294 cm1, while the CC bond vibration is only active in Raman (2105 cm1; see the Supporting Information, Figure S4). 13C CP-MAS solid-state NMR shows the expected signals at 79 and 75 ppm, characteristic of the alkyne carbon atoms, and at 11 ppm for the CH2Si carbon atom (Figure 2). CP-MAS 29Si NMR only shows T2 and T3 signals, with a condensation degree of 88 %, signifying an extended siloxane network without cleavage of the CSi bonds (see the

Figure 2. 13C NMR spectra of precursors and PMO materials; (left): solution NMR of 3 d (a) and of 1 (b); CP-MAS NMR spectra of M1 before (c) and after (d) CuAAC functionalisation with ethyl 2-azidoacetate; (right) solution NMR spectra of 4 a (a) and of 2 (b); CP-MAS NMR of M2 before (c) and after (d) CuAAC functionalisation with methyl pent-4-ynoate. The *, P and § symbols indicate spinning side bands, triphenylphosphine oxide (130–140 ppm) and CDCl3 signals (77 ppm), respectively. Chem. Eur. J. 2014, 20, 10371 – 10382

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Full Paper Supporting Information, Figure S5). Elemental analyses performed on the alkyne-containing material before surfactant removal are in good agreement with the formula, [O1.5Si(CH2)3]2NCH2CCH·C16H34SO4, which corresponds to a 1:1 adduct between the surfactant and the fully condensed monomer. However, whereas the extracted material does not contain any more surfactant (with no detectable sulfur), it still contains a high amount of water, as the C and N contents are far below the expected amounts, while their relative contents are in agreement with the theoretical ratio (see the Supporting Information, Table S1). This is confirmed by TGA analyses (see the Supporting Information, Figure S6) with a strong weight loss of around 17 % below 100 8C. Alkyne-based material M1 is thermally stable up to 220 8C. The weight losses between 200 and 300 8C (14 %) presumably arise from the decomposition of the pendant propargyl groups. Indeed, considering the ideal formula C9H15NO3Si2 the elimination of an acetylene molecule would result in a weight loss of around 11 %. Scanning electron micrographs (Figure 3 C) indicate that the material was obtained with a wormlike structure (ca 70–150 nm wide and 1– 5 mm long microrods), while the porous structure was revealed by transmission electron microscopy (Figure 3 A and B), confirming the 2D-hexagonal lattice as seen from the Fourier transform of the image. SAXS spectra of M1 (Figure 4, left) are characteristic of cylindrical mesopores with a 2D-hexagonal arrangement of the structure (P6 mm space group), with a distance between pores (that is, between the axes of neighbouring cylinders) of 5.0 nm.[28] According to the previously published results on similar materials synthesised under the same conditions,[27c] the pores are expected to have a diameter of 2.0 nm and, thus the wall thickness is calculated at 3.0  0.3 nm. Very similar features were observed for the azide–PMO obtained from 2. In this case, a very intense band is observed at Figure 3. TEM micrographs of M1 (A, B) and M2 (E, F). The insets represent the FFT of the zones enclosed by the square. SEM micrographs of M1 before 2098 cm1 in FTIR, which is typical for the azide function. The (C) and after (D) CuAAC with ethyl azidoacetate and of M2 before (G) and thermal stability of M2 is slightly lower than that of M1, with after (H) CuAAC with methyl pent-4-ynoate. a weight loss of 15 % starting at 180 8C (see the Supporting information, Figure S6). SAXS spectra (Figure 4, right) on the as-synthesised material are typical of a 2D-hexagonal arrangement (P6 mm space group) with a distance between pores of 4.4 nm and, thus, a wall thickness around 2.4 nm. Upon template removal,pffiffiffi the pseudo-Bragg peaks ( 3 q0) and (2 q0) tend to disappear, meaning the mesostructure order is partially lost. The first q0 peak is only displayed and it slightly shifts towards high q wavevector correof PMO materials with 2D-hexagonal structure (P6 mm space group) displaying the followsponding to an inter-reticular Figure 4. SAXS spectra p ing Bragg peaks: q0, 3q0, 2q0. Left: alkyne–PMO M1 before (dots), after (squares) template extraction and after distance lattice compaction of CuAAC reaction (triangles). Right: azide–PMO M2 before (dots), after the template removal (squares), and also 4  (that is, inter-reticular dis- after outgassing (triangles). In the latter curve, only the first q0 peak is displayed and a slight shift of q0 towards tance reduction). high q wave vector is observed. Chem. Eur. J. 2014, 20, 10371 – 10382

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Figure 5. FT-IR spectra of (left) mesoporous material M3 (a), M3 after exposure to CuSO4 and sodium ascorbate in H2O/tBuOH (b) and after CuAAC functionalisation with (c) diethyl 2-azidoethylphosphonate and (d) ethyl 2-azidoacetate. Inset: zoom on the 3050–3350 cm1 region; (right) mesoporous material M4 (a) M4 after exposure to CuSO4 and sodium ascorbate in H2O/tBuOH (b), and after CuAAC functionalisation with (c) methyl pentynoate, (d) propargylthymine.

After outgassing at much a lower temperature (50 8C) than the decomposition temperature determined by TGA, N2-sorption experiments were run on M1 or M2, without any N2 being adsorbed under the usual conditions. Complementary SAXS studies showed a decrease in the intensity upon outgassing, thus suggesting either a partial pore collapse or a partial pore obstruction phenomena resulting from a contrast in lower electronic density (Figure 4, right). However, in spite of this low stability under reduced pressure, we performed CuAAC on materials M1 and M2, using the usual CuSO4/sodium ascorbate catalytic system. Interestingly, as revealed by FTIR monitoring of the reaction (by calculating the surface ratio between the azide peak and the siloxane broad band), a conversion of ca 60 % was attained when M2 was reacted with methyl pentynoate (Figure 1). Similarly, a strong decrease of the CspH band at 3294 cm1 was observed when M1 was reacted with ethyl azidoacetate. Furthermore, the successful CuAAC was clearly evidenced by 13C solid-state NMR spectra. In both cases, prominent signals corresponding to the triazole carbon atoms (d 145 and 122 ppm) and to the ester functions (d 170 ppm) appear; in the case of alkyne-containing material M1, disappearance of the signals at 70– 80 ppm, which correspond to the alkyne functions, is also observed. This is in agreement with the very high conversion deduced from the FTIR spectra. This clearly shows that even if the mesoporosity could not be experimentally evidenced by N2 sorption, the porous structure was still open and enabled the reactants to diffuse to a significant extent within the material that was not outgassed. Notably, the external aspect of the material remained unchanged after CuAAC, as seen with the SEM micrographs (Figure 3, D and H). In addition, the M1 SAXS spectra (Figure 4, left) display, both after template removal and after CuAAC, the first pseudo-Bragg peak at the same q wave vector, implying that mesoporosity is kept, though the longrange order is partially lost upon CuAAC. Besides the latter PMO materials, mesoporous organosilicas were also obtained by using cetyltrimethylammonium bromide Chem. Eur. J. 2014, 20, 10371 – 10382

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(CTAB) under basic catalysis (molar ratio: (1 or 2)/CTAB/NH3/ H2O = 1:0.8:30:1500). Materials M3 and M4 exhibit FTIR (Figure 5) and NMR (see the Supporting Information, Figure S7) characteristics that are similar to those of M1 and M2, with even slightly higher condensation degrees at silicon (95 %). SEM and transmission electron microscopy (TEM images (Figure 6) show in both cases that the materials consist of ag-

Figure 6. TEM micrographs of mesoporous materials M3 (A) and M4 (D); SEM micrographs of M3 before (B) and after (C) CuAAC reaction with ethyl azidoacetate and M4 before (E) and after (F) CuAAC reaction with methyl pent-4-ynoate.

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Figure 7. N2-sorption isotherms of mesoporous material M3 after template extraction (squares) and after CuAAC functionalisation with (triangles) ethyl azidoacetate and (spheres) diethyl azidoethylphosphonate.

gregated nanoparticles (20–30 nm). Indeed, N2-sorption experiments (Figure 7) reveal significant specific surface areas (475 and 185 m2 g1 by the BET method for M3 and M4, respectively). The N2-sorption isotherm of M3 exhibits a typical H2 hysteresis loop,[29] with a sharp desorption at p/p8 = 0.4–0.5, which is consistent with the sorption of N2 in the voids between such small nanoparticles. In this case, no pseudo-Bragg peak can be detected by SAXS measurements. M3 and M4 SAXS spectra exhibit quite similar behaviour. At intermediate q values, a nonPorod regime (I(q) / q3) is shown, suggesting that the nanospheres have rough surfaces and the broad peak around 0.5 1 might correspond to the approximate distance between holes of 1.3 nm (see the Supporting Information, Figure S9). The reactivity of these mesoporous organosilicas was checked using model alkynes: the azide-functionalised material was almost quantitatively converted (89  10 %) when reacted with methyl pent-4-ynoate using the CuSO4–sodium ascorbate system, with a nearly complete disappearance of the N3 absorption band at 2100 cm1 (Figure 5) and a sharp and intense peak appearing at 1731 cm1 corresponding to the clicked ester functionality. A low intensity Csp2H band can also be distinguished at 3140 cm1, which highlights the formation of the triazole ring. Here also, the high conversion of the azide functions into triazoles could be evidenced by 13C solid-state NMR, with the appearance of prominent triazole (d 122 and 145 ppm) and ester (d 172 ppm) signals. Furthermore, a control experiment was performed by stirring M4 in a solution of copper(II) sulphate and sodium ascorbate in a water/t-butanol mixture in the absence of any alkyne. After prolonged stirring (65 h instead of 48 h for the CuAAC reactions), a 32 % decrease of the azide IR band at 2100 cm1 was observed (Figure 5). This is much less than the corresponding CuAAC experiment in the presence of methyl pent-4-ynoate (89 % decrease), for a significantly longer reaction time. Additionally, the preservation of the morphology of starting material M4 was here also evidenced by SEM and SAXS (see the Supporting Information, FigChem. Eur. J. 2014, 20, 10371 – 10382

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ure S9), revealing the preservation of the structure, which is expected owing to the high condensation at silicon (mostly T3 signals in 29Si CP-MAS NMR spectra), which prevents any rearrangement of the inorganic framework. At first sight, this very high yield of functionalisation for M4 seems counterintuitive as the materials are composed of dense nanospheres. However, the flexible nature of the organic fragments should favour the diffusion of small reactants within the structure. Indeed, we already reported that bridged silsesquioxanes with no surface area detectable by N2 sorption at 77 K displayed catalytic activities comparable with analogous catalysts grafted on SBA-15 materials.[30] We believe that here also the flexibility of the organic bridges at room temperature and the important roughness evidenced by SAXS enable the diffusion of small molecules within the structure and result in such high conversions. The reactivity of the alkyne material M3 towards various organic azides was also probed by FTIR (Figure 5) and solid-state NMR (see the Supporting Information Figure S8). In all cases, an important decrease of the FTIR CspH peak at 3294 cm1 and the concomitant formation of the triazole ring (Csp2H band at 3140 cm1) were observed, while no trace of remaining adsorbed organic azide (that would absorb at 2100 cm1) was detected. In 13C NMR, the signals of the alkyne carbons fully vanished while strong signals corresponding to the triazole (d 145 and 122 ppm) and ester groups (d 172 ppm) appeared. As observed in the N2-sorption isotherms (Figure 7), the click functionalisation results in an important decrease of the specific surface area and of the adsorbed volume of N2, which can be attributed to a shortening of the pores after the functionalisation takes place, but also to a densification of the structure. Using organic fragments containing phosphorus, it was possible to determine the extent of click grafting.[19a] Indeed, the P content after grafting diethyl 2-azidoethyl phosphonate on M3 was 4.7 %, with N/P and P/Si molar ratios of 4.5 and 0.17. From the latter value, a conversion of ca. 35 % can be calculated for this reaction. Finally, clickable material M4 was functionalised using propargylthymine. As observed by FTIR, a high conversion of ca. 78 % was achieved, as deduced from the ratio of the peak areas between the azide and siloxane absorptions, while the BET surface area was reduced from 185 to ca. 40 m2 g1. Interestingly, the compared FTIR spectra of the thymine-based materials obtained through paths A then B or C then D are mostly similar, with a strong absorption of the C=O groups at 1680 cm1 (see the Supporting Information, Figure S1). The main structural difference between the materials lies in their morphology (nanospheres of 70–80 nm from paths A–B, and 20–30 nm for paths C–D).

Conclusion The combination of CuAAC and sol-gel processing enables the formation of new functional bridged silsesquioxanes. On the one hand, a wide variety of bridged organosilanes are now available thanks to the CuAAC reaction of clickable organosilanes with functional alkynes or azides under strictly anhydrous conditions. We have shown in these studies that such bridged precursors can be obtained from organic molecules bearing

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Full Paper a single derivatisation site thanks to a ramified bis(trialkoxysilane), in contrast to the conventional bridged organosilanes, which are obtained by anchoring two or more triethoxysilyl groups on several sites of the organic moiety featuring the targeted functionality. This strategy will thus increase the variety of conceivable bridged silsesquioxanes. On the other hand, clickable porous bridged silsesquioxanes and PMOs have been synthesised. Their post-functionalisation using model alkynes and azides show that high conversions can be achieved, even for a functional fragment such as the thymine nucleobase. Notably, in the course of this study, we have shown that whatever the order of the combination of CuAAC and sol-gel reactions, thymine-based materials with similar characteristics could be obtained. Based on these methodological results, new materials with controlled nanostructure and with promising application in nanomedicine are being developed, which will be presented shortly.

Experimental Section General All the experiments were carried out using Schlenk techniques under a dry atmosphere of nitrogen. Microwave reactions were carried out in sealed tubes by using a CEM Discover Microwave Reactor equipped with an infrared temperature sensor. NMR spectra were recorded in dry CDCl3 at 298 K. 1H and 13C chemical shifts are reported in ppm relative to Me4Si, and 31P chemical shifts are reported in ppm relative to H3PO4. Solid state 13C and 29Si CP/MAS NMR experiments were recorded on a Varian VNMRS 400 MHz spectrometer by using a two-channel probe with ZrO2 rotors of diameter 7.5 mm and TMS as the reference for the chemical shifts. The SEM images were obtained with a Hitachi S-4800 apparatus after platinum metallisation. TEM micrographs were obtained by using a JEOL 1200 EX2 apparatus equipped with a SIS Olympus Quemesa 11 Mpixel camera. FTIR spectra were recorded using a Perkin100 spectrometer equipped with a mono internal reflexion ATR module. Raman spectra were recorded with a LabRAM ARAMIS (Horiba) spectrometer using a HeNe laser (633 nm). XRD measurements were carried out in 1.5 mm diameter glass capillaries at the Laboratoire Charles Coulomb (Montpellier). A copper rotating-anode X-ray source working at 4 kW with a multilayer focusing Osmic monochromator giving high flux and punctual collimation was employed with an image plate 2D detector. The smallangle X-ray scattering (SAXS) experiments were conducted using a Guinier–Mering setup with a 2D image plate detector. The X-ray source was a molybdenum anode, which delivered a high-energy monochromatic beam (l = 0.71 , E = 17.4 keV), providing structural information over scattering vectors q ranging from 0.01 to 1.5 1. Helium flowed between the sample and the image plate to avoid air adsorption. The sample acquisition time was 3600 s. Data corrections, radial averaging and absolute scaling were performed through standard procedures. The image azimuthal average was determined by the FIT2D software from ESRF (France).

Triethoxysilane 1 To a solution of bis(triethoxysilylpropyl)amine (12.8 g, 30.0 mmol) in moist THF containing 0.1 % H2O (100 mL), calcium hydride (3.16 g, 75 mmol) and propargyl bromide (80 wt % in toluene, 4.28 g, 36.0 mmol) were added successively. The reaction mixture Chem. Eur. J. 2014, 20, 10371 – 10382

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was stirred overnight at room temperature. After evaporation of the solvents, extraction of the reaction mixture with pentane and evaporation, a yellowish viscous oil was obtained, which was then purified by vacuum distillation (130 8C/2.102 mbar) giving a colourless liquid (13.2 g, 28.4 mmol). Yield: 95 %. 1H NMR (250 MHz, CDCl3): d = 3.81 (q, J = 7.0 Hz, 12 H), 3.38 (d, J = 2.3 Hz, 2 H), 2.56– 2.34 (m, 4 H), 2.13 (t, J = 2.3 Hz, 1 H), 1.65–1.46 (m, 4 H), 1.21 (t, J = 7.0 Hz, 18 H), 0.66–0.56 ppm (m, 4 H); 13C NMR (101 MHz, CDCl3): d = 79.0, 72.5, 58.4, 56.7, 41.83, 21.0, 18.4, 8.1 ppm; HRMS (ESI +): calcd for C21H46NO6Si2, 464.2864; found, 464.2871.

Triethoxysilane 2 A mixture of bis(triethoxysilylpropyl)amine (10.0 g, 23.5 mmol), 1azido-2-iodoethane (4.61 g, 23.5 mmol) and potassium carbonate (6.3 g, 46 mmol) in acetonitrile (100 mL) was stirred overnight at 85 8C in a sealed tube. After the mixture was concentrated, pentane was added then the solution was filtered and the filtrate was concentrated giving a yellowish oil (11.0 g, 22.3 mmol). Yield: 95 %. 1 H NMR (400 MHz, CDCl3): d = 3.81 (q, J = 7.1 Hz, 12 H), 3.25 (t, J = 6.4 Hz, 2 H), 2.65 (t, J = 6.4 Hz, 2 H), 2.46 (t, J = 7.4 Hz, 4 H), 1.54 (m, 4 H), 1.22 (t, J = 7.1 Hz, 18 H), 0.59 ppm (m, 4 H); 13C NMR (101 MHz, CDCl3): d = 58.6, 57.6, 53.7, 49.8, 20.7, 18.6, 8.1 ppm; HRMS (ESI +): calcd for C20H47N4O6Si2 : 495.3034; found: 495.3016.

Triethoxysilane 2’ A mixture of bis(triethoxysilylpropyl)amine (1.0 g, 2.3 mmol), 3-iodopropylazide (4.48 g, 2.3 mmol) and potassium carbonate (0.63 g, 4.6 mmol) in acetonitrile (20 mL) was stirred overnight at 85 8C in a sealed tube. The mixture was filtered and the filtrate was concentrated giving a yellowish oil (1.1 g, 2.2 mmol). Yield: 93 %. 1H NMR (250 MHz, CDCl3): d = 3.80 (q, J = 7.0 Hz, 12 H), 3.31 (t, J = 6.8 Hz, 4 H), 2.54–2.46 (m, 8 H), 2.38 (t, J = 6.9 Hz, 4 H), 1.75–1.61 (m, 4 H), 1.59–1.41 (m, 4 H), 1.21 (t, J = 7.0 Hz, 18 H), 0.61–0.49 ppm (m, 4 H); 13 C NMR (63 MHz, CDCl3): d = 58.5, 57.2, 51.1, 49.8, 26.9, 20.4, 18.4, 8.1 ppm; HRMS (ESI +): calcd for C21H49N4O6Si2 : 509.3191; found: 509.3174.

General procedure for the click reaction A microwave tube was filled under nitrogen with alkyne (2 mmol), azide (2 mmol/alkyne function), [CuBr(PPh3)3] (0.01 mmol/alkyne function), dry triethylamine (0.5 mL) and dry THF (0.5 mL) and then sealed. The mixture was irradiated under strong stirring at 100 8C (Pmax = 200 W) for 5 min. The completion of the reaction was checked by FTIR or TLC. The reaction mixture was allowed to cool, then the solvents were removed under vacuum. After addition of dry pentane, the mixture was filtered, and then the filtrate was concentrated to afford the title compound.

Triethoxysilane 3 a Yield: 94 %. 1H NMR (400 MHz, CDCl3): d = 7.37 (s, 1 H), 4.27 (t, J = 7.3 Hz, 2 H), 3.76 (q, J = 7.0 Hz, 12 H), 3.72 (s, 2 H), 2.42–2.34 (m, 4 H), 1.88–1.77 (m, 3 H), 1.58–1.48 (m, 4 H), 1.26 (bs, 8 H), 1.17 (t, J = 7.0 Hz, 18 H), 0.57–0.49 ppm (m, 4 H); 13C NMR (101 MHz, CDCl3): d = 145.9, 122.0, 58.3, 56.8, 50.2, 49.0, 31.2, 30.3, 26.2, 22.4, 20.5, 18.3, 13.9, 8.0 ppm; HRMS (ESI + ): calcd for C27H59N4O6Si2 : 591.3973; found: 591.3969.

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Full Paper Triethoxysilane 3 b

Triethoxysilane 3 h

1

Yield: 95 %. H NMR (400 MHz, CDCl3): d = 7.38–7.31 (m, 5 H), 7.25– 7.20 (m, 1 H), 5.50 (s, 2 H), 3.78 (q, J = 7.0 Hz, 12 H), 3.74 (s, 2 H), 2.44–2.34 (m, 4 H), 1.62–1.46 (m, 4 H), 1.19 (t, J = 7.0 Hz, 18 H), 0.59– 0.48 ppm (m, 4 H); 13C NMR (101 MHz, CDCl3): d = 146.5, 135.0, 129.1, 128.7, 128.0, 122.3, 58.3, 56.8, 54.1, 49.0, 20.5, 18.4, 8.0 ppm; HRMS (ESI +): calcd for C28H53N4O6Si2 : 597.3504; found: 597.3514.

Triethoxysilane 3 c

Yield: 87 %. 1H NMR (250 MHz, CDCl3): d = 7.38 (s, 2 H), 4.26 (t, J = 7.3 Hz, 4 H), 3.75 (q, J = 7.0 Hz, 24 H), 3.71 (s, 4 H), 2.45–2.30 (m, 8 H), 1.92–1.75 (m, 4 H), 1.63–1.43 (m, 8 H), 1.30–1.20 (bs, 12 H), 1.36 (t, J = 7.0 Hz, 36 H), 0.58–0.45 ppm (m, 8 H); 13C NMR (101 MHz, CDCl3): d = 145.8, 122.0, 58.3, 56.7, 50.1, 48.9, 30.3, 29.2, 28.9, 26.4, 20.4, 18.3, 7.9 ppm; HRMS (ESI +): calcd for C52H111N8O12Si4 : 1151.7399; found: 1151.7421.

Triethoxysilane 3 i

Yield: 95 %. 1H NMR (400 MHz, CDCl3): d = 7.41 (s, 1 H), 4.30 (t, J = 7.3 Hz, 2 H), 3.80 (q, J = 7.0 Hz, 12 H), 3.76 (s, 2 H), 3.62 (t, J = 6.6 Hz, 2 H), 2.63–2.55(m, 1 H), 2.42 (t, J = 8.0 Hz, 4 H), 1.92–1.82 (m, 2 H), 1.65–1.49 (m, 4 H), 1.37–1.23 (b, 14 H), 1.21 (t, J = 7.0 Hz, 18 H), 1.07 (t, J = 7.2 Hz, 2 H), 0.61–0.53 ppm (m, 4 H); 13C NMR (101 MHz, CDCl3): d = 145.9, 122.1, 63.0, 58.4, 56.8, 50.3, 49.1, 32.9, 30.4, 29.5, 29.4 (3C), 29.0, 26.5, 25.8, 20.5, 18.4, 8.0 ppm; HRMS (ESI +): calcd for C32H69N4O7Si2 : 677.4705; found: 677.4698.

Yield: 91 %. 1H NMR (250 MHz, CDCl3): d = 7.37 (bs, 2 H), 7.23 (s, 4 H), 5.49 (s, 4 H), 3.81 (q, J = 7.0 Hz, 24 H), 3.77 (s, 4 H), 2.47–2.32 (m, 8 H), 1.69–1.40 (m, 8 H), 1.19 (t, J = 7.0 Hz, 36 H), 0.61–0.44 ppm (m, 8 H); 13C NMR (101 MHz, CDCl3): d = 146.2, 135.4, 128.5, 122.2, 58.2, 56.6, 53.3, 48.8, 20.3, 18.2, 7.8 ppm; HRMS (ESI +): calcd for C50H99N8O12Si4 : 1115.6460; found: 1115.6447.

Triethoxysilane 3 j Triethoxysilane 3 d Yield: 92 %. 1H NMR (400 MHz, CDCl3): d = 7.56 (s, 1 H), 5.11 (s, 2 H), 4.23 (q, J = 7.2 Hz, 2 H), 3.76 (s, 2 H), 3.71 (q, J = 7.0 Hz, 12 H), 2.41 (m, 4 H), 1.56 (m, 4 H), 1.27 (t, J = 7.2 Hz, 3 H), 1.19 (t, J = 7.0 Hz, 18 H), 0.57–0.34 ppm (m, 4 H); 13C NMR (101 MHz, CDCl3): d = 166.3, 146.2, 123.7, 62.3, 58.3, 56.6, 50.8, 48.8, 20.5, 18.3, 14.1, 7.9 ppm; HRMS (ESI +): calcd for C25H53N4O8Si2 : 593.3402; found: 593.3407.

Triethoxysilane 3 e Yield: 97 %. 1H NMR (400 MHz, CDCl3): d = 7.41 (s, 1 H), 4.59– 4.40 (m, 2 H), 4.10–3.90 (m, 4 H), 3.71 (q, J = 7.0 Hz, 12 H), 3.67 (s, 2 H), 2.44–2.19 (m, 6 H), 1.49 (m, 4 H), 1.24 (t, J = 7.1 Hz, 6 H), 1.12 (t, J = 7.0 Hz, 18 H), 0.57–0.34 ppm (m, 4 H); 13C NMR (101 MHz, CDCl3): d = 145.9, 122.4, 62.0, 58.2, 56.6, 48.8, 44.3, 27.9, 26.5, 20.4, 18.2, 16.3, 7.8 ppm; HRMS (ESI +): calcd for C27H60N4O9Si2P: 671.3637; found: 671.3635.

Triethoxysilane 3 f Yield: 94 %. 1H NMR (400 MHz, CDCl3): d = 7.41 (s, 1 H), 4.30 (t, J = 7.2 Hz, 2 H), 3.78 (q, J = 7.0 Hz, 12 H), 3.77 (q, J = 7.0 Hz, 6 H), 3.75 (s, 2 H), 2.41 (t, J = 7.0 Hz, 4 H), 2.03–1.94 (m, 2 H), 1.63– 1.48 (m, 4 H), 1.19 (t, J = 7.0 Hz, 9 H), 1.18 (t, J = 7.0 Hz, 18 H), 0.62–0.51 ppm (m, 6 H); 13C NMR (101 MHz, CDCl3): d = 145.6, 122.3, 58.6, 58.4, 56.8, 52.5, 49.0, 24.4, 20.5, 18.4 (2C), 8.0, 7.6 ppm; HRMS (ESI + ): calcd for C30H67N4O9Si3 : 711.4216; found: 711.4212. Triethoxysilane 3 g Yield: 91 %. 1H NMR (400 MHz, CDCl3): d = 8.33 (s, 1 H), 7.91 (s, 1 H), 7.52 (s, 1 H), 6.14 (s, 2 H), 4.32 (t, J = 6.4 Hz, 2 H), 4.23 (t, J = 6.5 Hz, 2 H), 3.77 (q, J = 7.0 Hz, 12 H), 3.73 (s, 2 H), 2.52–2.46 (m, 2 H), 2.44– 2.36 (m, 4 H), 1.60–1.49 (m, 4 H), 1.17 (t, J = 7.0 Hz, 18 H), 0.58– 0.50 ppm (m, 4 H); 13C NMR (101 MHz, CDCl3): d = 155.8, 153.1, 146.4, 132.2, 132.1, 128.6, 122.7, 58.3, 56.9, 49.0, 46.8, 40.9, 30.5, 20.6, 18.4, 8.0 ppm; HRMS (ESI +): calcd for C29H56N9O6Si2 : 682.3892; found: 682.3894. Chem. Eur. J. 2014, 20, 10371 – 10382

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Yield: 90 %. 1H NMR (400 MHz, CDCl3): d = 7.17 (s, 3 H), 5.67 (s, 2 H), 5.64 (s, 4 H), 3.82 (q, J = 7.0 Hz, 36 H), 3.74 (s, 6 H), 2.61–2.31 (m, 21 H), 1.67–1.46 (m, 12 H), 1.23 (t, J = 7.0 Hz, 54 H), 0.66–0.41 ppm (m, 12 H); 13C NMR (101 MHz, CDCl3): d = 146.0, 139.6, 130.7, 121.7, 58.2, 56.6, 48.9, 20.2, 18.2, 16.5, 7.9, 0.9 ppm; HRMS (ESI +): calcd for C75H150N12O18Si6 : 1674.9807; found: 1674.9800.

Triethoxysilane 4 a Yield: 98 %. 1H NMR (400 MHz, CDCl3): d = 7.44 (s, 1 H), 4.33 (t, J = 6.5 Hz, 2 H), 3.71 (q, J = 7.0 Hz, 12 H), 3.67 (s, 3 H), 3.02 (t, J = 7.5 Hz, 2 H), 2.85 (t, J = 6.5 Hz, 2 H), 2.73 (t, J = 7.5 Hz, 2 H), 2.44 (m, 4 H), 1.47 (m, 4 H), 1.21 (t, J = 7.0 Hz, 18 H), 0.57–0.34 ppm (m, 4 H); 13 C NMR (101 MHz, CDCl3): d = 173.1, 145.8, 121.8, 58.2, 57.1, 54.2, 51.5, 48.7, 33.4, 20.9, 20.3, 18.2, 7.7 ppm; HRMS (ESI +): calcd for C26H55N4O8Si2 : 607.4069; found: 607.4048.

Triethoxysilane 4 b Yield: 91 %. 1H NMR (400 MHz, CDCl3): d = 8.34 (s, 1 H), 7.98 (s, 1 H), 7.63 (s, 1 H), 6.09 (s, 2 H), 5.46 (s, 2 H), 4.33 (t, J = 7.3 Hz, 2 H), 3.77 (q, J = 7.0 Hz, 12 H), 2.39 (t, J = 8 Hz, 2 H), 2.35 (t, J = 8 Hz, 4 H), 2.01–1.92 (m, 2 H), 1.51–1.40 (m, 4 H), 1.18 (t, J = 7.0 Hz, 18 H), 0.56– 0.49 ppm (m, 4 H); 13C NMR (101 MHz, CDCl3): d = 155.7, 153.1, 149.8, 142.2, 140.5, 123.1, 119.6, 58.4, 56.8, 50.7, 48.7, 36.7, 28.3, 20.2, 18.4, 8.0 ppm; HRMS (ESI +): calcd for C29H55N9O6Si2 : 681.3814; found: 681.3809.

Triethoxysilane 4 c Yield: 98 %. 1H NMR (400 MHz, CDCl3): d = 7.79 (s, 1 H), 7.30 (s, 1 H), 4.92 (s, 2 H), 4.35 (t, J = 6.4 Hz, 2 H), 3.80 (q, J = 7.1 Hz, 12 H), 2.85 (t, J = 6.3 Hz,2 H), 2.43 (m, 4 H), 1.87 (s, 3 H), 1.46 (m, 4 H), 1.20 (t, J = 7.1 Hz, 18 H), 0.51 ppm (m, 4 H); 13C NMR (63 MHz, CDCl3): d = 164.3, 150.9, 142.1, 140.4, 124.5, 111.2, 58.6, 57.2, 54.3, 49.2, 43.2, 20.4, 18.5, 12.5, 8.05 ppm; HRMS (ESI +): calcd for C28H55N6O8Si2 : 659.3620; found: 659.3617.

Triethoxysilane 4 d Yield: 96 %; 1H NMR (400 MHz, CDCl3): d = 7.35 (s, 2 H), 5.09 (q, J = 8.8 Hz, 2 H), 4.30 (s, 2 H), 4.11 (t, J = 7.8 Hz, 4 H), 3.52 (q, J = 7.2 Hz, 24 H), 2.41–2.25 (bs, 2 H), 2.21–2.05 (m, 12 H), 1.81–1.68 (m, 4 H), 1.28–1.55 (m, 8 H), 0.93 (t, J = 7.2 Hz, 36 H), 0.82–0.74 (m, 2 H), 0.34–

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Full Paper 0.24 ppm (m, 8 H); 13C NMR (101 MHz, CDCl3): d = 171.4, 142.0, 124.0, 67.3, 72.4, 58.5, 56.9, 50.7, 50.3, 28.4, 20.3, 18.5, 8.1 ppm; HRMS (ESI + ): calcd for C52H107N8O18Si4 : 1243.6780; found: 1243.679.

washings were repeated 5 times. The resulting material was dried under reduced pressure.

Acknowledgements

Triethoxysilane 4 e Yield: 91 %; 1H NMR (400 MHz, CDCl3): d = 7.55 (s, 2 H), 4.67 (s, 4 H), 4.38 (t, J = 7.2 Hz, 4 H), 3.81 (q, J = 7.1 Hz, 24 H), 3.69–3.60 (m, 16 H), 2.45 (t, J = 6.8 Hz, 4 H), 2.40 (t, J = 6.8 Hz, 8 H), 2.02 (m, 4 H), 1.50 (m, 8 H), 1.22 (t, J = 7.1 Hz, 36 H), 0.57 ppm (m, 8 H); 13C NMR (101 MHz, CDCl3): d = 145.0, 122.7, 70.65 (2C), 70.60, 69.7, 64.7, 58.4, 56.9, 50.9, 48.6, 28.5, 20.3, 18.4, 8.1 ppm; HRMS (ESI + ): calcd for C56H118N8O17Si4 : 1287.7770; found: 1287.7776.

The CNRS, the Agence Nationale pour la Recherche (ANR P2N 2010 MECHANANO and ANR P2N 2012 NanoptPDT), the Czech Science Foundation (P108/12/1356), the BARRANDE project (MSMT 7AMB12FR004), the French embassy in Prague (grant to KB), are gratefully acknowledged for financial support. We also thank Dr Philippe Dieudonn (LCC Montpellier) for XRD measurements and Prof Philippe Trens (ICG Montpellier) for fruitful discussions.

Synthesis of material M-Thy Precursor 4 c (0.46 g, 0.7 mmol) was dissolved in a solution of ethanol (1.4 mL, 42 mmol, [Si] = 1 m). Under vigorous stirring, distilled water (0.23 g, 4.2 mmol) was added together with NH4F (1 m in water, 14 mL, 14 mmol). The mixture was stirred vigorously for two minutes then kept at room temperature. A gel was obtained after 12 h. After 48 h of aging, the temperature was raised to 70 8C for 18 h. The resulted powder was washed with water, ethanol and acetone and finally dried at 40 8C under reduced pressure for 5 h. A light-green powder (365 mg) was obtained. IR (ATR): n˜ = 695, 777, 906, 1018, 1098, 1217, 1265, 1265, 1350, 1384, 1437, 1467, 1677, 2816, 2933, 3060, 3144 cm1.

Synthesis of POMs M1 and M2 Precursor 1 or 2 (2.0 mmol) was added to a mixture of sodium hexadecylsulphate SHS (containing 40 % of sodium stearyl sulphate, 531 mg, 1.5 mmol) in water (36 mL, 2.0 mol) and hydrochloric acid 1 m (4 mL, 4 mmol) at 60 8C. A white precipitate formed after 1 min. The mixture was stirred for 20 min at 60 8C then filtered and washed with water and ethanol. The white solid was dried at 70 8C for 12 h. The surfactant was eliminated by washing the solid with a solution consisting of 200 mL of ethanol and 10 mL of NH4NO3 in ethanol (20 g L1). Yields from 2.0 mmol of precursor: M1: 398 mg; M2: 381 mg.

Synthesis of mesoporous materials M3 and M4 Under vigorous stirring, compound 1 or 2 (1.0 mmol) was added to a mixture of CTAB (0.29 g, 0.8 mmol), distilled water (17 mL, 0.97 mol) and NH4OH (25 % wt, 2.3 mL, 30 mmol). The mixture was heated to 70 8C and stirred for 24 h. The molar ratio of the starting compounds was 1 or 2/CTAB/NH3/H2O = 1:0.79:30:1500. The material was recovered by evaporating the water. The surfactant was eliminated by repeated washing with a solution consisting of 100 mL ethanol and 5 mL of 37 % HCl. Yields from 2.0 mmol of precursor: M3: 245 mg; M4: 183 mg.

General procedure for CuAAC on the materials The clickable material (0.1 mmol) was incubated with the corresponding clickable partner (0.3 mmol) in the presence of copper sulphate CuSO4 (0.1 mmol) and sodium ascorbate (0.4 mmol) in 3 mL of water/t-butanol mixture (v/v: 1). The mixture was stirred vigorously at room temperature for 48 h. The material was recovered by centrifugation (26 000 rpm, 10 min) and washed with water, sodium N,N-diethyldithiocarbamate (0.1 m in methanol, 10 mL), methanol (10 mL) and acetone (10 mL). The last three Chem. Eur. J. 2014, 20, 10371 – 10382

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