Multistimuli Responsive Micelles Formed by a Tetrathiafulvalene

Jun 6, 2011 - Cite this:Langmuir 27, 14, 8665-8671 .... Xiao-Jun Wang , Ling-Bao Xing , Bin Chen , Ying Quan , Chen-Ho Tung , Li-Zhu Wu. Organic ...
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Multistimuli Responsive Micelles Formed by a Tetrathiafulvalene-Functionalized Amphiphile Xiao-Jun Wang, Ling-Bao Xing, Feng Wang, Ge-Xia Wang, Bin Chen, Chen-Ho Tung, and Li-Zhu Wu* Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry & Graduate University, Chinese Academy of Sciences, Beijing 100190, P. R. China

bS Supporting Information ABSTRACT:

An electroactive tetrathiafulvalene (TTF)-functionalized amphiphile 1 was designed and synthesized to investigate its selfassembling behavior in water. Dynamic light scattering (DLS), 1H NMR, fluorescence spectrum, and cryogenic transmission electron microscopy (cryo-TEM) studies revealed that amphiphile 1 can form micelle-like aggregates via direct dissolution into water, and the micellar architectures could be disrupted either by addition of chemical oxidant Fe(ClO4)3 or by complexation with electron-deficient cyclobis(paraquat-p-phenylene) tetracation cyclophane (CBPQT4þ) to release encapsulated hydrophobic dye Nile Red from the interior of micelles.

’ INTRODUCTION Amphiphilic ensembles, namely those that carry both hydrophilic and hydrophobic segments in a determined proportion, can spontaneously self-assembly in solutions or at interfaces to generate a variety of well-defined nano- or microscopic architectures, such as micelles, vesicles, nanotubes, fibers, and rods.1 The incorporation of stimuli-responsive functional groups into these building blocks is of particular significance to engineer “smart” systems for use in optoelectronic materials, drug or gene delivery, and template synthesis.24 In general, these responsive self-assembling processes can be achieved by tuning the properties of functional groups in amphiphiles. Zhang et al.,1e for example, made use of noncovalent interactions to prepare a series of superamphiphiles and manipulate their self-assembly and disassembly simply by external triggers. Lee et al.1f developed responsive nanostructures via the self-assembly of small block molecules based on rigidflexible molecules in aqueous solution. Much to our surprise, although a large number of functional stimuli-responsive amphiphiles have been constructed during the past decades, the self-assembling behavior of tetrathiafulvalene and its derivatives (TTFs) in aqueous environment is far less explored. As one of the most famous organic famous electron donors, TTFs have been used as versatile building blocks in the design of organic metals and self-assembling architectures.5,6 In 1995, r 2011 American Chemical Society

Becher and Bryce realized that ππ stacking and hydrogenbonding interactions were effective in building supramolecular stacks.7 Recently, hydrogen-bonding and/or intermolecular ππ stacking interactions have been employed to establish well-defined nanostructures of organic molecules containing the TTF unit.8 Specifically, Zhang and co-workers utilized the unique redox properties of TTF moiety to tune the gelsol transition behaviors by oxidation and reduction as well as by reactions with electron acceptors.9 Zhao and Li reported the first self-assembling vesicles from TTF derivatives in organic solvents.10 In the present work, we wish to report a TTF-functionalized amphiphile 1 bearing p-phenyleneethynyleneTTF as a hydrophobic moiety and three triethylene glycol (TEG) monomethyl ether chains as hydrophilic tails (Scheme 1). Compared with TTF endfunctionalized poly(N-isopropylacrylamide) amphiphilic polymer11 described by Cooke and Woisel very recently, such a small molecular weight amphiphile12 simplifies the synthesis remarkably and has a well-defined structure. We envision that amphiphile 1 would assembly in water and respond to the applied stimuli, analogous to those Received: May 7, 2011 Revised: June 1, 2011 Published: June 06, 2011 8665

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Scheme 1. Chemical Structure of Amphiphile 1 and the Schematic Representation of Assembly and Disassembly of the Micelles

Scheme 2. Synthetic Routes to 1 and 1aa

a Reagents and conditions: (a) trifluoroacetic acid, CH2Cl2; (b) 4-iodobenzoic acid, PyBOP, TEA, DMF, CH2Cl2; (c) TMSA, [Pd(PPh3)4], CuI, TEA, THF; (d) K2CO3, CH3OH, CH2Cl2; (e) 2-iodotetrathiafulvalene, [Pd(PPh3)4], CuI, TEA, THF.

observed in organic solvents.10 As will be discussed later, this expectation was found to be the case. The self-assembling and disassembling processes are capable of realizing with the addition of either chemical oxidant Fe(ClO4)3 or electron-deficient cyclophane CBPQT4þ into the aqueous solution.

’ RESULTS AND DISCUSSION Synthesis and Self-Assembly of Amphiphile 1 in Water. The synthesis of amphiphile 1 was carried out under the typical Sonogashira coupling conditions with a relatively shorter reaction time and higher yield (Scheme 2). The starting N-Bocprotected compound 2 (see Scheme S1) with hydrophilic R group was deprotected under excess trifluoroacetic acid (TFA) in CH2Cl2. Subsequently, an excess of triethylamine (TEA) was slowly added to neutralize TFA in an icewater bath. The generated terminal amine was directly coupled with 4-iodobenzoic acid in the mixture of CH2Cl2 and DMF in the aid of benzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate (PyBOP) to give compound 3. The Sonogashira reaction of 3 with an excess (trimethylsilyl)acetylene (TMSA) yielded 4, which was then deprotected by excess K2CO3 in the mixture of CH3OH and CH2Cl2 to afford the terminal alkyne compound 5. Then, 5 was reacted with 2-iodotetrahiafulvalene in the presence of triethylamine (TEA) in THF to produce target amphiphilic compound 1, which was identified by 1H NMR and 13C NMR spectroscopy, matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF

Figure 1. Temperature-dependent transmittance at 700 nm of 1 (1  104 M) in aqueous solution.

MS), and satisfactory elemental analysis. As expected, amphiphile 1 was found very soluble both in organic solvents and in water. Owing to temperature-sensitive hydrogen-bonding ability of poly(ethylene glycol) functionality with water,13 it is suggested that the degree of hydration of the ethylene oxide chains would decrease with increasing temperature, thus resulting in a lower critical solution temperature (LCST) behavior. This was indeed observed as shown in Figure 1 (inset). The solution of amphiphile 1 becomes turbid upon heating, and the whole process was thermally reversible. The value of LCST was determined to be around 37 °C by the transmittance change of amphiphile 1 at 700 nm. Clearly, this thermoresponsive solution behavior is 8666

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Langmuir resulted from the dehydration of TEG chains and amide groups with increasing temperature. The self-assembly of amphiphile 1 can be performed by simply dissolving into water. Far from its 1H NMR spectra in organic solvents, the proton signals of amphiphile 1 in D2O were broad, weak, and upfield-shifted (Figure S1), which may be derived from the interaction between the TTF groups and the environmental change of 1, i.e., the formation of aggregates in water. Such aggregates was evidenced by fluorescence spectroscopy method, where organic dye Nile red (NR) was served as a probe. It is wellknown that NR is not soluble in water because of its strong hydrophobicity. No absorption and emission could be detected from its aqueous solution. When NR was introduced to the aqueous solution of amphiphile 1, as shown in Figure 2, the fluorescent intensity of NR remained almost unchanged at low concentration, but a sharp increase was clearly observed as the concentration of 1 over 1.6  105 M. No significant change in the fluorescence spectra of NR was observed for model compound 1a under the same conditions. These results suggest that amphiphile 1 aggregates in water and the dyes have been encapsulated inside the hydrophobic domain of the aggregators. Consistent with that obtained by the fluorescence spectroscopy method, the plot of the surface tension versus the concentration of amphiphile 1 further proved the formation of aggregates with critical aggregation concentration (CAC) value of 1.5  105 M (Figure S2). The aggregated species of 1 in aqueous solution was corroborated by dynamic light scattering (DLS) experiments. CONTIN analysis of the DLS autocorrelation function of 1 shows a

Figure 2. Fluorescence intensity of NR as a function of the concentration of 1 (9) and 1a (b) in water at ambient temperature (λex = 530 nm, λem = 635 nm).

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main distribution of hydrodynamic diameter (Dh) of the aggregates centered at ∼8 nm in aqueous solution (Figure 3a). Cryogenic transmission electron microscopy (cryo-TEM) was performed to gain a direct visualization of the size and morphology. As shown in Figure 3b and Figure S4, individual spherical micelles were clearly observed with the diameter in the range of 611 nm, in a good agreement with that obtained by DLS. As for the aqueous solution of reference 1a at the same concentration, however, the low DLS count rates (less than 12 kcps) and cryoTEM images suggest no aggregation for 1a under the similar conditions (Figure S5). These results further indicate that hydrophobic p-phenyleneethynyleneTTF unit is necessary for self-assembly of amphiphile 1 in water. In addition, a small amount of larger aggregates was observed around 73 nm with a close inspection of DLS data and cryo-TEM image of 1, suggesting the existence of vesicles in a small quantity (Figure S6). Disassembly by Chemical Oxidant Fe(ClO4)3. As we know, TTF moiety can be oxidized to its radical cation (TTF 3 þ) and dication (TTF2þ) sequentially and reversibly at low potentials. In the case of amphiphile 1, cyclic voltammetry (CV) experiment was carried out in water. Two reversible one-electron oxidation waves (E1/2) at þ316 and þ601 mV vs SCE, corresponding to the twostep oxidation (TTF f TTF•þ f TTF2þ), were detected (Figure S7). To exploit the influence of oxidized TTF on the amphiphilicity of 1 and the stability of micelles, we employed Fe(ClO4)3 as an oxidant to generate these oxidized states of 1 in aqueous and CH3CN solutions, respectively (Figure 4a and Figure S8). Monitored by absorption spectra, it was found that about 32 equiv of Fe(ClO4)3 was required to fully oxidize 1 in the aqueous solution, whereas only 2 equiv of Fe(ClO4)3 was needed to produce dication 12þ (TTF2þ) in CH3CN. Such differences could be interpreted by the fact that the TTF moiety is buried in the hydrophobic core of micelles that is not easily accessible for Fe(ClO4)3. Furthermore, electron spin resonance (ESR) of radical cation 1•þ (TTF•þ) showed four-line spectra in aqueous solution, while no splitting signal could be observed from that of 1•þ in CH3CN (Figure 4b and Figure S9). Such a difference was presumably induced by the spinspin coupling of TTF•þ units in 1•þ, which are close to each other in the hydrophobic inner core in aqueous solution.14 As shown in Figure 5, with continuous addition of Fe(ClO4)3 to a solution of 1 and NR, the fluorescence intensity of NR encapsulated into the hydrophobic core of micelles decreased as well as red-shifted to longer wavelength,15 indicative of the release of NR and the collapse of micellar architectures. According to the relative fluorescence intensity, 70% NR was found to be

Figure 3. DLS data (a) and cryo-TEM image of the micelles (b) for amphiphile 1 obtained at concentration of 9.0  105 M in aqueous solution. The DLS data are shown as the size probability distribution obtained by a CONTIN analysis. 8667

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Figure 4. (a) Absorption spectral changes of 1 (5  105 M) in aqueous solution with the concentration of Fe(ClO4)3. (b) ESR spectra of radical cation 1•þ (1  104 M); in water at room temperature.

Figure 5. Fluorescence spectra of NR in the aqueous solution of 1 (8.0  105 M) with the concentration of Fe(ClO4)3.

out of the micelles. The fluorescence spectra of either NR in the presence of Fe(ClO4)3 or the micelles of 1 with NR in the presence of NaClO4 have no significant changes (Figures S10 and S11), suggesting that the disassembly of micelle architectures was induced by the oxidation of TTF unit to more hydrophilic TTF2þ, together with the electrostatic repulsion between the oxidized species. Such disassembly was supported by the cryoTEM image of 1 upon fully oxidation of the TTF unit by an excess of Fe(ClO4)3 (Figure S12). Disassembly by Electron-Deficient Cyclophane CBPQT4þ. Because of the high π-electron-donating ability, TTFs can form stable charge-transfer complexes with electron-deficient species, tetracationic cyclobis(paraquat-p-phenylene) (CBPQT4þ).16 Herein, we took advantage of the complexation of 1 and CBPQT4þ in solution to disassembly the micelle architectures. As shown in Figure 6a, when amphiphile 1 and CBPQT4þ were mixed in water, a green solution appeared immediately, accompanied with a very broad charge-transfer band around 800 nm in the absorption spectra. Meanwhile, the CV patterns were remarkably affected by the presence of CBPQT4þ (Figure S7). The first oxidation peak for the complex shifted dramatically from þ316 to þ535 mV, whereas the second oxidation peak at þ601 mV was almost the same as that of 1 in aqueous solution. These observations indicate that CBPQT4þ ring moves away from the TTF unit in the charge-transfer complex just as soon as it is oxidized to the radical cation 1•þ. In the reducing cycle, the first reduction peaks of the dication TTF2þ are almost identical at þ531 mV, which means that the CBPQT4þ ring is close to the TTF unit

in 1 to influence the reduction of the radical cation TTF•þ back to its neutral form. Additional insight into the complexation of 1 and CBPQT4þ was gained by means of 1H NMR spectroscopy studies in D2O and CD3CN (Figure 6b and Figure S13). A mixture of 1 and CBPQT4þ (1:1) exhibited a quite different spectrum from that of amphiphile 1 itself in D2O. Upon addition of CBPQT4þ to solution, the broad and featureless peaks of 1 disappeared with emergence of notable splitting and shifting signals. Specifically, the proton H (]) resonance of TTF unit shifted to upfield position (Δδ = 0.17 ppm in D2O, 0.56 ppm in CD3CN), whereas the aromatic protons H (2, ]) neighboring the TTF unit shifted to downfield (Δδ = 0.22 for H (4) and 0.63 for H (2) in D2O; 0.16 for H (4) and 0.26 ppm for H (2) in CD3CN). These observations suggest the formation of charge-transfer complex between 1 and CBPQT4þ, leading to the strong shielding and deshielding effect of the aromatic rings in CBPQT4þ. In contrast to the upfield shift (Δδ = 0.15 ppm for H ([)) in CD3CN, the “abnormal” downfield shift of H ([, Δδ = 0.08 ppm) of TTF unit in CBPQT4þ aqueous solution could be explained as follows. The protons of TTF unit located in the inner core of micelles felt the strong shielding effect. When the TTF unit was trapped into the ring of CBPQT4þ, the shielding effect of CBPQT4þ ring is smaller than the deshielding effect induced by the disassembly of micelles. As a result, the H ([) of TTF unit was downfield-shifted in D2O upon addition of CBPQT4þ. The disassembling micelles of 1 upon complexation with CBPQT4þ were further studied using fluorescence and cryoTEM techniques. Figure 7a displayed the fluorescence spectra of 1 and NR with the addition of CBPQT4þ. In the beginning, the fluorescent intensity was slightly increased, possibly due to the reduction of electron transfer from the TTF unit in 1 to NR. Subsequently, the fluorescent intensity of NR decreased dramatically even to disappearance with the concentration of CBPQT4þ, while no significant changes could be observed from that of NR itself in water under the same condition (Figure S14). Clearly, the remarkable decrease in fluorescence intensity of NR was triggered by its release from the disassembling micelles upon complexation with CBPQT4þ. Such a disassembling fact was also confirmed by the cryo-TEM image of 1 in the presence of CBPQT4þ (Figure 7b). This disruption may be explained by considering the two factors: (1) the original hydrophobic part of 1 became more hydrophilic upon complexation with CBPQT4þ, and (2) the electrostatic repulsion interactions between these terminus tetracationic species caused the separations of charge-transfer complexes. 8668

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Figure 6. (a) Absorption spectra of 1 (5  105 M) in the absence and presence of CBPQT 3 4Cl (1.0 equiv) in H2O. (b) Partial 1H NMR spectra (400 MHz, D2O, 298 K) of 1 (3 mM, bottom), 1 þ 1.0 equiv of CBPQT 3 4Cl (middle), and CBPQT 3 4Cl (3 mM, top).

Figure 7. (a) Fluorescence spectra of NR and 1 (8.0  105 M) with the concentration of CBPQT 3 4Cl in water. (b) Cryo-TEM image of 1 (8.0  105 M) in the presence of CBPQT4þ (1.4 equiv).

’ CONCLUSIONS In conclusion, we have synthesized a redox-active TTF functionalized amphiphile 1 by the Sonogashira reaction in a good chemical yield. The amphiphilic 1 can self-assembly in water to form micellar aggregates. More interestingly, the micelle architectures could be disrupted either by the addition of chemical oxidant Fe(ClO4)3

or by the complexation with electron-deficient ring CBPQT4þ. This is, to the best of our knowledge, the first example of micelles based on a small organic molecule featuring electroactive TTF unit. It is anticipated that this research line can lead to the fabrication of new smarter aggregates, such as vesicle, which is actively undergoing in our research group. 8669

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’ EXPERIMENTAL SECTION 3: To a CH2Cl2 (30 mL) solution of 2 (8.03 g, 10.5 mmol) was added 20 mL of trifluoroacetic acid (TFA), and the mixture was stirred at room temperature for over 2 h. Then, an excess of triethylamine was added to neutralize TFA in the icewater bath. To the resulting mixture was added DMF (50 mL), 4-iodobenzoic acid (2.48 g, 10 mmol), and then PyBOP (6.24 g, 12 mmol). The solution was stirred at room temperature for another 1.5 h, then poured into water (200 mL), and extracted with CH2Cl2 (3  100 mL). The combined organic layer were washed with brine for more than eight times to remove DMF, dried over Na2SO4, and evaporated in vacuo to dryness. The crude product was purified by silica gel flash column chromatography (CH2Cl2/CH3OH, 100/1) to give 3 as colorless oil (7.61 g, 8.5 mmol, 85%). 1H NMR (400 MHz, CDCl3): δ 7.80 (d, J = 8.3 Hz, 2H), 7.64 (d, J = 8.4 Hz, 3H), 7.17 (s, 3H), 4.244.19 (m, 6H), 3.84 (t, J = 4.7 Hz, 4H), 3.79 (t, J = 5.1 Hz, 2H), 3.723.70 (m, 6H), 3.673.62 (m, 12H), 3.553.49 (m, 10H), 3.37 (s, 3H), 3.35 (s, 6H), 1.80 (s, 2H). 13C NMR (101 MHz, CDCl3): δ 167.9, 166.9, 152.5, 141.5, 137.7, 133.9, 129.4, 128.9, 107.4, 98.4, 72.4, 71.9, 70.7, 70.5, 69.8, 69.1, 59.0, 36.4, 36.2, 29.7. MALDITOF-MS: m/z calcd for C38H59IN2O14: 894.8; found: 917.4 [M þ Na]þ. 4: Compound 3 (0.89 g, 1.0 mmol), CuI (7.6 mg, 0.04 mmol), and Pd(PPh3)4 (23 mg, 0.02 mmol) were added to the mixture of anhydrous THF (40 mL) and TEA (20 mL) under Ar. While stirring, trimethylsilylethyne (0.12 g, 1.20 mmol) was injected through syringe. The reaction mixture was stirred at 5060 °C overnight under an Ar atmosphere and was monitored by TLC. Upon completion, the solution was evaporated in vacuo to dryness. The crude product was purified by silica gel flash column chromatography (CH2Cl2/CH3OH, 100/1) to give the compound 4 as a colorless oil (0.75 g, 0.87 mmol, 87%). 1H NMR (400 MHz, CDCl3): δ 7.82 (d, J = 8.2 Hz, 2H), 7.67 (s, 1H), 7.49 (d, J = 8.2 Hz, 2H), 7.44 (s, 1H), 7.17 (s, 2H), 4.204.16 (m, 6H), 3.81 (t, J = 4.8 Hz, 4H), 3.76 (t, J = 5.0 Hz, 2H), 3.703.68 (m, 6H), 3.623.60 (m, 12H), 3.523.49 (m, 10H), 3.34 (s, 3H), 3.32 (s, 6H), 1.78 (s, 2H), 0.23 (s, 9H). 13C NMR (101 MHz, CDCl3): δ 167.4, 166.9, 152.1, 140.8, 133.8, 131.7, 129.2, 126.9, 125.9, 106.8, 104.0, 96.5, 72.1, 71.6, 70.4, 70.3, 70.2, 69.4, 68.6, 58.7, 36.3, 36.2, 29.3, 0.3. MALDI-TOF-MS: m/z calcd for C43H68N2O14Si: 865.1; found: 865.5 [M]þ, 887.6 [M þ Na]þ, 903.7 [M þ K]þ. 5: To a CH2Cl2 (20 mL) and methanol (30 mL) solution of 4 (2.10 g, 2.43 mmol) was added K2CO3 (13.8 g, 10 mmol). The solution was stirred at room temperature for 15 min, then poured into water (100 mL), and extracted with CH2Cl2 (3  50 mL). The combined organic layer were washed with 1 M HCl (1  100 mL) and brine (3  150 mL), dried over Na2SO4, and evaporated in vacuo to dryness. The crude product was purified by silica gel flash column chromatography (CH2Cl2/CH3OH, 105/1) to give 5 as colorless oil (1.83 g, 2.31 mmol, 95%). 1H NMR (400 MHz, CDCl3): δ 7.89 (d, J = 8.3 Hz, 2H), 7.73 (s, 1H), 7.54 (d, J = 8.3 Hz, 2H), 7.48 (s, 1H), 7.23 (s, 2H), 4.25 (t, J = 4.6 Hz, 4H), 4.20 (t, J = 4.8 Hz, 2H), 3.83 (t, J = 5.1 Hz, 4H), 3.76 (t, J = 4.6 Hz, 2H), 3.713.69 (m, 6H), 3.653.61 (m, 12H), 3.553.51 (m, 10H), 3.36 (s, 3H), 3.34 (s, 6H), 3.18 (s, 1H), 1.82 (s, 2H). 13 C NMR (101 MHz, CDCl3): δ 167.4, 166.8, 152.1, 140.8, 134.1, 131.8, 129.2, 126.9, 124.9, 106.7, 82.6, 79.5, 72.1, 71.6, 70.4, 70.3, 70.2, 70.1, 69.4, 68.6, 58.6, 36.2, 36.1, 29.2. MALDI-TOF-MS: m/z calcd for C40H60N2O14: 792.3; found: 793.5 [M þ H]þ, 815.5 [M þ Na]þ. 1: To the mixture of anhydrous THF (30 mL) and TEA (30 mL) were added 5 (0.83 g, 1.05 mmol,), TTF-I (0.4 g, 1.20 mmol), CuI (3.8 mg, 0.02 mmol), and Pd(PPh3)4 (12 mg, 0.01 mmol) under Ar. The reaction mixture was refluxed over 12 h under an Ar atmosphere and was monitored by TLC. Upon completion, the solution was evaporated in vacuo to dryness. The crude product was purified by silica gel flash column chromatography (CH2Cl2/CH3OH, 90/1) to give the compound 1 as red oil (0.86 g, 0.89 mmol, 85%). 1H NMR (400 MHz, CDCl3): δ 7.85 (d, J = 8.5 Hz, 2H), 7.77 (s, 1H), 7.54 (s, 1H), 7.47 (d, J = 8.4 Hz, 2H), 7.17 (s, 2H), 6.60 (d, J = 2.3 Hz, 1H), 6.31 (s, 2H), 4.214.16 (m, 6H), 3.81 (t, J = 5.1 Hz, 4H), 3.76 (t, J = 4.7 Hz, 2H), 3.693.67 (m, 6H), 3.633.59 (m, 12H), 3.523.47

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(m, 10H), 3.34 (s, 3H), 3.32 (s, 6H), 1.79 (s, 2H). 13C NMR (101 MHz, CDCl3): δ 167.3, 166.6, 152.0, 140.7, 134.1, 131.2, 129.1, 127.0, 125.6, 124.6, 118.9, 118.7, 115.1, 106.6, 92.4, 72.0, 71.5, 70.3, 70.1, 69.3, 68.6, 58.6, 36.2, 29.2. MALDI-TOF-MS: m/z calcd for C46H62N2O14S4: 995.2; found: 993.7 [M]þ. Anal. Calcd (%) for C46H62N2O14S4: C, 55.51; H, 6.28; N, 2.81; found: C, 55.57; H, 6.33; N, 2.86.

’ ASSOCIATED CONTENT

bS

Supporting Information. Experimental details. This material is available free of charge via the Internet at http://pubs.acs.org.

’ AUTHOR INFORMATION Corresponding Author

*E-mail: [email protected]. Fax: þ86 10-8254 3580.

’ ACKNOWLEDGMENT We are grateful for financial support from the National Science Foundation of China (20732007, 20920102033, and 20972171), the Ministry of Science and Technology of China (2007CB808004, 2007CB936001, and 2009CB22008), and the Bureau for Basic Research of Chinese Academy of Sciences. We thank Prof. Dr. Zhibo Li (ICCAS, Beijing) and Dr. Gang Ji (IBP, Beijing) for their help on cryo-TEM. ’ REFERENCES (1) (a) Shimizu, T.; Masuda, M.; Minamikawa, H. Chem. Rev. 2005, 105, 1401–1444. (b) Wang, Y.; Xu, H.; Zhang, X. Adv. Mater. 2009, 21, 2849–2864. (c) Kim, J.-K.; Lee, E.; Lim, Y.-b.; Lee, M. Angew. Chem., Int. Ed. 2008, 47, 4662–4666. (d) Lee, H. Y.; Nam, S. R.; Hong, J.-I. Chem.—Asian J. 2009, 4, 226–235. (e) Zhang, X.; Wang, C. Chem. Soc. Rev. 2011, 40, 94–101. (f) Kim, H.-J.; Kim, T.; Lee, M. Acc. Chem. Res. 2010, 44, 72–82. (2) (a) Hill, J. P.; Jin, W.; Kosaka, A.; Fukushima, T.; Ichihara, H.; Shimomura, T.; Ito, K.; Hashizume, T.; Ishii, N.; Aida, T. Science 2004, 304, 1481–1483. (b) Hizume, Y.; Tashiro, K.; Charvet, R.; Yamamoto, Y.; Saeki, A.; Seki, S.; Aida, T. J. Am. Chem. Soc. 2010, 132, 6628–6629. (c) Alarcon, C. d. l. H.; Pennadam, S.; Alexander, C. Chem. Soc. Rev. 2005, 34, 276–285. (d) Zhang, X.; Rehm, S.; Safont-Sempere, M. M.; W€urthner, F. Nature Chem. 2009, 1, 623–629. (3) (a) Moon, K.-S.; Kim, H.-J.; Lee, E.; Lee, M. Angew. Chem., Int. Ed. 2007, 46, 6807–6810. (b) Zhang, S.; Zhao, Y. J. Am. Chem. Soc. 2010, 132, 10642–10644. (c) Klaikherd, A.; Nagamani, C.; Thayumanavan, S. J. Am. Chem. Soc. 2009, 131, 4830–4838. (d) Wang, C.; Chen, Q.; Wang, Z.; Zhang, X. Angew. Chem., Int. Ed. 2010, 49, 8612–8615. (4) (a) Lee, H.-i.; Wu, W.; Oh, J. K.; Mueller, L.; Sherwood, G..; Peteanu, L.; Kowalewski, T.; Matyjaszewski, K. Angew. Chem., Int. Ed. 2007, 46, 2453–2457. (b) Jiang, Y.; Wang, Y.; Ma, N.; Wang, Z.; Smet, M.; Zhang, X. Langmuir 2007, 23, 4029–4034. (c) Wang, C.; Chen, Q.; Xu, H.; Wang, Z.; Zhang, X. Adv. Mater. 2010, 22, 2553–2555. (d) Wang, Y.; Ma, N.; Wang, Z.; Zhang, X. Angew. Chem., Int. Ed. 2007, 46, 2823–2826. (e) Goodwin, A. P.; Mynar, J. L.; Ma, Y.; Fleming, G. R.; Frechet, J. M. J. J. Am. Chem. Soc. 2005, 127, 9952–9953. (5) (a) Yamada, J.; Sugimoto, T. TTF Chemistry: Fundamentals and Applications of Tetrathiafulvalene; Springer-Verlag: Heidelberg, 2004. (b) Canevet, D.; Salle, M.; Zhang, G.; Zhang, D.; Zhu, D. Chem. Commun. 2009, 2245–2269. (c) Puigmartí-Luis, J.; Schaffhauser, D.; Burg, B. R.; Dittrich, P. S. Adv. Mater. 2010, 22, 2255–2259. (d) Xu, C.H.; Sun, W.; Zhang, C.; Zhou, C.; Fang, C.-J.; Yan, C.-H. Chem.—Eur. J. 2009, 15, 8717–8721. (6) Geng, Y.; Wang, X.-J.; Chen, B.; Xue, H.; Zhao, Y.-P.; Lee, S.; Tung, C.-H.; Wu, L.-Z. Chem.—Eur. J. 2009, 15, 5124–5129 and references therein. 8670

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(7) Batsanov, A. S.; Svenstrup, N.; Lau, J.; Becher, J.; Bryce, M. R.; Howard, J. A. K. J. Chem. Soc., Chem. Commun. 1995, 1201–1202. (8) (a) Amabilino, D. B.; Puigmartí-Luis, J. Soft Matter 2010,  .; 6, 1605–1612. (b) Puigmartí-Luis, J.; Laukhin, V.; PerezdelPino, A Vidal-Gancedo, J.; Rovira, C.; Laukhina, E.; Amabilino, D. B. Angew. Chem., Int. Ed. 2007, 46, 238–241. (c) Puigmartí-Luis, J.; PerezdelPino,  .; Laukhina, E.; Esquena, J.; Laukhin, V.; Rovira, C.; Vidal-Gancedo, J.; A Kanaras, A. G.; Nichols, R. J.; Brust, M.; Amabilino, D. B. Angew. Chem., Int. Ed. 2008, 47, 1861–1865. (d) Wang, X.-J.; Xing, L.-B.; Cao, W.-N.; Li, X.-B.; Chen, B.; Tung, C.-H.; Wu, L.-Z. Langmuir 2010, 27, 774–781. (9) (a) Wang, C.; Zhang, D.; Zhu, D. J. Am. Chem. Soc. 2005, 127, 16372–16373. (b) Wang, C.; Chen, Q.; Sun, F.; Zhang, D.; Zhang, G.; Huang, Y.; Zhao, R.; Zhu, D. J. Am. Chem. Soc. 2010, 132, 3092–3096. (c) Wu, H.; Zhang, D.; Su, L.; Ohkubo, K.; Zhang, C.; Yin, S.; Mao, L.; Shuai, Z.; Fukuzumi, S.; Zhu, D. J. Am. Chem. Soc. 2007, 129, 6839–6846. (10) Zhang, K.-D.; Wang, G.-T.; Zhao, X.; Jiang, X.-K.; Li, Z.-T. Langmuir 2010, 26, 6878–6882. (11) Bigot, J.; Charleux, B.; Cooke, G.; Delattre, F.; Fournier, D.; Lyskawa, J.; Sambe, L.; Stoffelbach, F. O.; Woisel, P. J. Am. Chem. Soc. 2010, 132, 10796–10801. (12) (a) Zhang, X.; Chen, Z.; W€urthner, F. J. Am. Chem. Soc. 2007, 129, 4886–4887. (b) Fernandez, G.; Garcia, F.; Sanchez, L. Chem. Commun. 2008, 6567–6569. (c) Seo, S. H.; Chang, J. Y.; Tew, G. N. Angew. Chem., Int. Ed. 2006, 45, 7526–7530. (d) Ryu, J.-H.; Hong, D.-J.; Lee, M. Chem. Commun. 2008, 1043–1054. (e) Zhao, X.; Zhang, S. Chem. Soc. Rev. 2006, 35, 1105–1110. (13) (a) Smith, G. D.; Bedrov, D. J. Phys. Chem. B 2003, 107, 3095–3097. (b) Dormidontova, E. E. Macromolecules 2001, 35, 987–1001. (c) Jeong, B.; Bae, Y. H.; Kim, S. W. Macromolecules 1999, 32, 7064–7069. (14) Porel, M.; Ottaviani, M. F.; Jockusch, S.; Jayaraj, N.; Turro, N. J.; Ramamurthy, V. Chem. Commun. 2010, 46, 7736–7738. (15) (a) Stuart, M. C. A.; van de Pas, J. C.; Engberts, J. B. F. N. J. Phys. Org. Chem. 2005, 18, 929–934. (b) Minkenberg, C. B.; Florusse, L.; Eelkema, R.; Koper, G. J. M.; van Esch, J. H. J. Am. Chem. Soc. 2009, 131, 11274–11275. (16) Odell, B.; Reddington, M. V.; Slawin, A. M. Z.; Spencer, N.; Stoddart, J. F.; Williams, D. J. Angew. Chem., Int. Ed. Engl. 1988, 27, 1547–1550.

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dx.doi.org/10.1021/la201699t |Langmuir 2011, 27, 8665–8671