Giant Fullerene Polyelectrolytes Composed of C60Building Blocks with an Octahedral Addition Pattern and Discovery of a New Cyclopropanation Reaction Involving Dibromomalonates

We report here on the facile synthetic access of a new family of bis‐, tetra‐, hexa‐, and heptafullerenes (prototypes I–IV), which can be easily converted into very water soluble polyelectrolytes with up to 60 charges located on their periphery. Their very regioselective formation is based on the use of C2v‐symmetrical pentakisadducts 3 and hexakisadducts 2 as key intermediates. All fullerene moieties incorporated in these macromolecular structures involve a complete or partial octahedral addition pattern. Tripod‐shaped tetrafullerenes 9 a,b (type II), which can accumulate up to thirty positive or negative charges, are very soluble in acidic or basic water, respectively. Hexafullerenes 13 a,b (type III) were synthesized via isoxazolinofullerenes 10 followed by photolytic cleavage of the isoxazoline group. The giant heptafullerene 1 b (type IV) representing the anionic counterpart of the previously synthesized polyelectrolyte 1 a can store up to 60 negative charges on its periphery within a defined three‐dimensional structure. We also discovered a new cyclopropanation reaction of C60 involving dibromomalonates and 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU). This reaction allows even for the highly regioselective formation of hexakisadducts with an octahedral addition pattern without requiring activation with reversibly binding addends such as 9,10‐dimethylanthracene (DMA).

On the shoulders of giants: A giant heptafullerene (see figure) is one of four new prototypes of large fullerene‐based polyelectrolytes with a precisely defined structure. The key intermediates for the construction of these macromolecules were synthesized from the C2v‐symmetrical pentakisadducts in excellent yields.

cycloaddition; fullerenes; photochemistry; polyelectrolytes; regioselectivity

The perfect spherical shape of C60 allows for the construction of highly symmetrical derivatives, in which exohedral addends are bound, for example, in octahedral positions of the fullerene cage.1 The resulting three‐dimensional nanostructures with precisely defined symmetry and shape are appealing candidates for the development of unprecedented supramolecular architectures and advanced materials.2–10 Fullerene hexakisadducts with an octahedral addition pattern are of special interest owing to a structure motif, which is unique in organic chemistry. One of the most important reactions to yield Th‐symmetrical hexakisadducts is the template‐mediated sixfold cyclopropanation of C60 with 9,10‐dimethylanthracene (DMA).11, 12 The thermally reversible Diels–Alder reaction between C60 and DMA creates an equilibrium mixture containing precursor adducts such as e‐C60‐(DMA)2 and e,e,e‐C60(DMA)3 templates that direct subsequent cycloadditions into the remaining equatorial sites. This procedure has been used to synthesize a large number of Th‐symmetrical hexakisadducts C66(COOR)12 with a broad variety of terminal groups R in good yields.2, 10, 13–18 Recently Sun and co‐workers developed an alternative method for the synthesis of Th‐symmetrical hexakisadducts.19, 20 Using a significantly increased amount of CBr4, no DMA was necessary in the synthesis of a variety of hexakisadducts.21–26 So far only a few water‐soluble hexakisadducts involving an octahedral addition pattern have been reported. Examples are mixed [3:3]hexakisadducts containing ammonium or carboxylic acid termini10, 27, 28 or amphiphilic [5:1]hexakisadducts leading to the formation of shape‐persistent micelles.29, 30 Recently, we reported on the synthesis of dumbbell‐shaped bisfullerenes bearing 20 negative or positive charges at their periphery and a Janus dumbbell containing both ammonium and carboxylic acid termini.15, 31 We reported also on a heptafullerene 1 a

that can store up to 60 positive charges. The latter is an example of a type IV architecture, as represented in Figure 1.

Hexakisadduct 2 a

bearing five malonate residues with tert‐butoxycarbonyl (Boc)‐protected terminal amino groups as well as one free malonate group suitable for further cyclopropanation of a fullerene core was the key intermediate for both the synthesis of the Janus dumbbell and heptafullerene 1 a. Recently, we introduced a simple method for the selective synthesis of C2v‐symmetrical pentakisadducts 3

with an incomplete octahedral addition pattern.24 The facile access to these interesting molecules was achieved by using an isoxazoline motif as a protection group. After completion of the octahedral addition pattern, the protection group can easily be removed by irradiation with light. By using such C2v‐symmetrical pentakisadduct precursors we were able to synthesize, for example, the hexakisadduct 2 b, which represents an anionic pendent of 2 a, in excellent yields.24

We now report on a significant extension of this concept of constructing well‐defined fullerene‐based polyelectrolytes: 1) two bisfullerenes containing up to 20 positive or negative charges (type I), 2) two tetrafullerenes containing up to 30 positive or negative charges (type II), 3) two hexafullerenes containing up to 50 positive or negative charges (type III), and 4) a heptafullerene that can store up to 60 negative charges on its periphery (type IV; Figure 1). Such well‐defined polyelectrolytes offer exciting perspectives for a variety of applications. For example, pronounced Coulomb interactions with other types of electrolytes such as DNA could form the basis for gene delivery or self‐assembly of new bio‐organic hybrid materials.

To improve the synthesis of 2 a15 we adopted the same reaction conditions that we already used for the synthesis of 2 b24 (Scheme 1). Pentakisadduct 3 f was reacted with cyclo[2]malonate 4 in the presence of CBr4 and DBU. Owing to the quantitative regioselectivity of cyclopropanation reactions on fullerene pentakisadducts the purification was possible by simple flash chromatography. Thus 2 a was isolated in 76 % yield. In analogy to the synthesis of 2 b the symmetrical bisfullerene 5 a could also be isolated with 6.4 % yield as a side product.

Treatment of the dumbbell‐shaped symmetrical bisfullerenes 5 a and 5 b (type I, Figure 1) with neat trifluoroacetic acid leads to a quantitative conversion of the N‐Boc groups to the corresponding ammonium salts or cleavage of the acid‐labile tert‐butyl esters, respectively (Scheme 2). In neutral and slightly acidic water the solubility of 6 a is comparatively low. However, if the solution is acidified a significant increase of the solubility is observed, which results in the formation of a bright yellow solution. The icosa‐anionic bisfullerene 6 b shows excellent solubility in both neutral and basic water.

For the synthesis of tetrafullerene polyelectrolytes (type II, Figure 1) we allowed e,e,e‐trisadduct 7 to react with 2 a or 2 b in the presence of a large excess amount of CBr4 (100 equiv) and DBU (12 equiv) (Scheme 3). After stirring for one week both tetrafullerenes 8 were pre‐purified by flash chromatography, followed by preparative recycling gel permeation chromatography (GPC).

The 13C NMR spectrum of 8 b displays only two signals, at δ=141 and 146 ppm, for all 144 sp2 C atoms of the three peripheral hexakisadducts (Figure 2). Owing to the lower symmetry of the central hexakisadduct, two sets of signals, each consisting of six signals, can be assigned to its 48 sp2 C atoms. In the region between δ=45.51 and 46.87 ppm three signals appear for the malonate‐bridge carbon atoms with an intensity ratio of 1:1:6. In the region δ=69.28–69.52 ppm four signals exhibit the typical upfield shift for the hexakisadduct sp3 C atoms. It is worth mentioning that in the spectrum of 8 a the signals of the inner, less symmetric fullerene did not appear in the spectrum (see the Supporting Information). This is owing to the fact that, in general, unreasonably long measurement times are necessary to resolve all of the weaker signals. High‐resolution ESI mass spectra of 8 a and 8 b revealed the molecular‐ion peaks. Structural characterization of 8 a and 8 b was completed by 1H and 13C NMR, UV/Vis, and IR spectroscopy. To achieve water solubility, 8 a,b were deprotected by treatment with neat trifluoroacetic acid (TFA; Scheme 3). The water solubility of 9 a and 9 b is strongly dependent on the pH value. At lower pH (pH 3), the amino groups of 9 a are protonated, which results in high water solubility. At higher pH (pH 10), the carboxylic acids of 9 b exist as their conjugated bases, so under these conditions the molecule shows high water solubility as well.

When treating 1032–34 with a tenfold excess amount of 2 a or 2 b under modified cyclopropanation conditions,20 [5:1]hexakisadducts 11 a and 11 b were obtained in 26–28 % yield (Scheme 4). Separation from side products with an incomplete octahedral addition pattern was achieved by preparative recycling GPC. The isoxazoline protective group was removed by irradiation with a halogen flood light in the presence of a large excess amount of maleic anhydride (200 equiv) to give 12 a and 12 b with 75–76 % isolated yield after flash chromatography. To achieve water solubility, 12 a and 12 b were deprotected by treatment with neat TFA.

Figure 3 compares the 1H NMR spectra of protected [5:1]hexakisadduct 11 b, hexafullerene 12 b, and deprotected hexafullerene 13 b. The duplets at δ=6.64 and 7.85 ppm in the spectrum of 11 b can be clearly assigned to the aromatic protons of the isoxazoline moiety. The absence of these signals in the spectrum of 12 b, as well as the absence of the signal of the dimethylamino group at δ=2.95 ppm clearly reflects the successful cleavage of the isoxazoline moiety. The signals of the macrocycles overlap with the more shielded signals of the tert‐butyl malonate (H5–H7). The absence of the signal of the tert‐butyl group in the spectrum of 13 b as well as the downfield shift of the signal of the methylene group adjacent to the acid group clearly demonstrates the quantitative cleavage of the acid‐labile tert‐butyl esters. Despite the very high molecular weight it was possible to obtain a high‐resolution mass spectrum of 11 b as a sixfold charged anion. In the mass spectrum of 11 a the sixfold and sevenfold charged anion was detected. However, the intensity was too poor to detect the monoisotopic molecular ion peak. The absence of the dimethylanilino group results in a dramatic decrease of the ionizability of compounds 12 a and 12 b. Thus, only two broad signals in the region of 2700–3500 or 2400–3100 mass/charge were found for 12 a and 12 b.

For the synthesis of an anionic counterpart of 1 a we treated 2 b with C60 under modified cyclopropanation conditions (Scheme 5).20 After stirring for one week we isolated a product that is responsible for the highest molecular weight peak by preparative recycling GPC. UV‐visible and NMR spectroscopy of the isolated molecule showed the typical characteristics of clean fullerene hexakisadducts. However ESI mass spectrometry only revealed the molecular‐ion peak of a hexafullerene. Thus, we increased the reaction time to three weeks. During the purification of the new reaction mixture by preparative recycling GPC another peak with higher molecular weight developed. The corresponding reaction product was isolated with 3.2 % yield. High‐resolution ESI mass spectrometry of this compound revealed the molecular‐ion peak of 14. The low yield, as well as the long reaction time is supposed to result from high steric hindrance in 14. Cleavage of the acid‐labile tert‐butyl esters was achieved by stirring in neat TFA.

As a byproduct in the synthesis of the polyfullerene adducts we isolated the dibrominated malonates 15 a and 15 b in yields between 63 and 89 % based on the used excess amount of 2 a and 2 b. It is worth mentioning that only the dibrominated malonates, but no monobrominated or free malonate was observed. Vigorous stirring of a solution of 15 a or 15 b in toluene together with a saturated solution of ammonium chloride in the presence of zinc dust for two days resulted in a nearly quantitative debromination (Scheme 6).

The debromination reaction can easily be monitored by TLC. Figure 4 compares the 13C NMR spectra of 15 b and 2 b. The signal for the malonate carbon bridge atom (C22) of 15 b at δ=51.29 ppm exhibits a typical downfield shift of dibrominated malonates.35 This trend can be further followed for the α‐CH2 group (C20) for which the chemical‐shift difference between the free malonate and the dibrominated malonate is almost 3 ppm.

It is supposed that under modified cyclopropanation reaction conditions, with the large excess amount of CBr4, bromination of the malonates is a relatively fast reaction. However, even after a reaction time of one week, cyclopropanation of the fullerene core still occurs. To explore this behavior further we treated C60 with a tenfold excess of diethyl dibromomalonate with DBU. After one hour, the TLC control shows that half of the C60 starting material was converted to the monoadduct. After one more day, a mixture of tetra‐, penta‐, and hexakisadducts was detected by TLC. Such a reaction cannot be explained with the classic cyclopropanation reaction mechanism, which is expected to proceed by means of an enolate. To explain these unexpected results we suggest a reaction mechanism that is shown in Scheme 7. It is known that C60 reacts with DBU with the formation of diradical 16 (a), which forms zwitterions 17 (b) upon a radical recombination process.36 In a next step either a nucleophilic substitution of bromine (c), or a nucleophilic attack of the C60 anion to the dibromomalonate (d) could take place. Cleavage of the remaining bromide (e) or substitution of the DBU cation (f) could now take place, both affording a cyclopropanated fullerene adduct. It is still not clear why the modified cyclopropanation affords hexakisadducts in such excellent yields. In the postulated mechanism, single‐charged fullerene species are present. So these monoanions could undergo a “walk‐on‐sphere” rearrangement.37, 38 A thermodynamic control of the hexakisadduct synthesis would explain the excellent yields obtained. Further studies on the mechanism are currently on the way.

We have synthesized and characterized a series of new bis‐, tetra‐, hexa‐, and heptafullerenes with a precisely defined structure. The corresponding C60 building blocks involve octahedrally arranged addition patterns. After acidic deprotection of the peripheral carboxy or amino groups water‐soluble oligoelectrolytes with up to 60 charges were obtained. The key intermediates 2 a,b required for the construction of these macromolecules were synthesized from the corresponding pentakisadducts in excellent yields. Dumbbell‐shaped bisfullerenes 6 a,b obtained as byproducts from this synthesis approach exhibit good water solubility under acidic or basic conditions, respectively. Tripod‐shaped tetrafullerenes 9 a,b generated from the e,e,e‐trisadduct 7 show the same pH‐dependent solubility. The corresponding transformation of the isoxazolinofullerene 10 followed by photolytic cleavage of the isoxazoline moiety yielded the hexafullerenes 13 a,b, which can store up to 50 negative or positive charges in their periphery. Heptafullerene 1 b, which is the anionic pendent of 1 a, can store up to 60 negative charges in its periphery and is highly soluble in basic water. We have also discovered a new cyclopropanation reaction of C60, namely, the reaction of the fullerene with dibromomalonates in the presence of DBU. This reaction even allows for the highly regioselective formation of hexakisadducts with an octahedral addition pattern without requiring activation with reversibly binding addends such as 9,10‐dimethylanthracene (DMA). We suggest a reaction mechanism involving singly charged fullerene species. These can undergo a “walk‐on‐sphere” rearrangement allowing for thermodynamic control and explaining the high yields of hexakisadducts.

General: All chemicals were purchased from chemical suppliers and were used without further purification. C60 99.0 % was purchased from IOLITEC nanomaterials. All analytical reagent‐grade solvents were purified by distillation. Thin layer chromatography (TLC): Merck HPTLC silica gel 60 F254. Detection: UV lamp or KMnO4 chamber. Flash chromatography (FC): Interchim puriFlash 430. PuriFlash Column 15 Silica HP‐Silica 15 μ. Preparative recycling HPLC: Software Shimadzu LCSolution 1.24 SP1, System Controller SCL‐10AVP, Solvent Delivery Pump LC‐8A, UV/Vis Detector SPD‐10A. Auto Injector SIL‐10A and Fraction Collector FRC‐10A were connected to the system controller but not to the flow line. A 2 mL sample loop connected to a valve unit FCV‐20AH2 was used for manual sample loading. A second Valve Unit FCV‐20AH2 was used to switch between closed‐loop recycling and collection mode. GPC columns: Machery‐Nagel Nucleogel GFC 500–10 (600×25 mm) and Agilent Technologies PLgel 10 μm MIXED‐D (300×25 mm) connected in series. HPLC‐grade chloroform (VWR) was used for the separations with a flow rate of 10 mL min−1. UV/Vis spectroscopy: Varian Cary 5000 UV‐visible‐NIR spectrophotometer. The absorption maxima λmax are given in nm, the extinction coefficients ε in [M−1 cm−1], shoulders are indicated as sh. Infrared spectra (IR): Bruker FTIR Tensor 27 (Pike MIRacle ATR, diamond) and Varian FTIR 660 (Pike Gladi ATR, diamond). The spectra were measured as pure solids or oils. All absorptions are given in wavenumbers $\tilde \nu $ [cm−1]. MS spectrometry: Bruker maXis 4G and Bruker micrOTOF II focus TOF mass spectrometer were used in ESI mode. NMR spectroscopy: JEOL JNM EX 400, Bruker Avance 300, and Bruker Avance 400. Chemical shifts are referenced to residual protic impurities in the solvents (1H) or the deuterated solvent itself (13C) and reported relative to external SiMe4. The resonance multiplicities are indicated as s (singlet), d (doublet), t (triplet), and m (multiplet); nonresolved and broad resonances as br. Compounds 2 b,243 f,244,395 b,247,39 and 1032–34 were prepared by methods reported previously in the literature.

Compounds 2 a and 5 a: Pentakisadduct 3 f24 (532 mg, 165 μmol, 1.0 equiv), cyclo[2]malonate 439 (353 mg, 824 μmol, 5.0 equiv), and CBr4 (82.0 mg, 247 μmol, 1.5 equiv) were dissolved in dry toluene (25 mL) under a nitrogen atmosphere. DBU (73.9 μL, 495 μmol, 3.0 equiv) was added over 5 min. The reaction mixture was stirred for 24 h and the crude product was purified by flash column chromatography (silica gel; toluene/ethyl acetate 60:40→35:65) affording 2 a (459 mg, 126 μmol, 76.3 %) and 5 a (36.4 mg, 5.30 μmol, 6.43 %) as yellow solids. Compound 2 a: Rf=0.56 (toluene/ethyl acetate 1:1); 1H NMR (400 MHz, CDCl3, RT): δ=1.29 (m, 48 H; CH2), 1.37 (s, 90 H; CH3), 1.40 (m, 28 H; CH2), 1.63 (m, 28 H; CH2), 3.03 (m, 20 H; CH2NH), 3.30 (s, 2 H; OCCH2CO), 4.09 (t, 3J=6.6 Hz, 4 H; OCH2), 4.19 (m, 24 H; OCH2), 4.75 ppm (br, 10 H; NH); 13C NMR (100.5 MHz, CDCl3, RT): δ=25.64 (10 C; CH2), 26.01, 26.03 (4 C; CH2), 26.45 (10 C; CH2), 28.42 (10 C; CH2), 28.52 (30 C; CH3), 28.61, 28.67 (4 C; CH2), 29.47, 29.49 (4 C; CH2), 30.03 (10 C; CH2), 40.58 (10 C; CH2NH), 42.34 (1 C; OCCH2CO), 45.47, 45.57, 45.58, 45.60 (6 C; OCCCO), 65.66 (2 C; OCH2), 66.98 (10 C; OCH2), 67.20 (2 C; OCH2), 69.20, 69.22, 69.26 (12 C; C60‐sp3), 79.01 (10 C; C(CH3)3), 141.29, 141.30, 141.35, 145.93, 145.97, 146.01 (48 C; C60‐sp2), 156.26 (10 C; COOtBu), 164.04, 164.08, 164.17 (12 C; CO), 166.70 ppm (2 C; CO); FTIR (ATR): $\tilde \nu $=608, 669, 715, 760, 780, 865, 990, 1042, 1080, 1167, 1213, 1263, 1365, 1391, 1456, 1514, 1691, 1743, 2859, 2932, 3349 cm−1; UV/Vis (CH2Cl2): λmax (ε)=245 (97 100), 271 (74 800), 281 (79 600), 317 (50 100), 335 nm (40 700 M−1 cm−1); HRMS (ESI): m/z calcd for C207H254N10O48+2 Na2+: 1846.8763 [M+2 Na2+]; found: 1846.8794. Compound 5 a: Rf=0.47 (toluene/ethyl acetate 1:1); 1H NMR (400 MHz, CDCl3, RT): δ=1.31 (m, 88 H; CH2), 1.40 (s, 180 H; CH3), 1.42 (m, 48 H; CH2), 1.66 (m, 48 H; CH2), 3.06 (m, 40 H; CH2NH), 4.22 (m, 48 H; OCH2), 4.76 ppm (br, 20 H; NH); 13C NMR (100.5 MHz, CDCl3, RT): δ=25.77 (20 C; CH2), 26.27 (4 C; CH2), 26.58 (20 C; CH2), 28.54 (20 C; CH2), 28.64 (60 C; CH3), 28.72 (4 C; CH2), 29.75 (4 C; CH2), 30.15 (20 C; CH2), 40.68 (20 C; CH2NH), 45.55, 45.64, 45.65, 45.67 (12 C; OCCCO), 67.06, 67.34 (24 C; OCH2), 69.26, 69.28, 69.32 (24 C; C60‐sp3), 79.09 (20 C; C(CH3)3), 141.24, 141.28, 141.29, 141.31, 141.33, 145.87, 145.90, 145.96, 146.00 (96 C; C60‐sp2), 156.22 (20 C; COOtBu), 163.99, 164.03, 164.04 ppm (24 C; CO); FTIR (ATR): $\tilde \nu $=608, 669, 715, 760, 780, 865, 990, 1042, 1080, 1167, 1213, 1263, 1365, 1391, 1456, 1514, 1691, 1743, 2859, 2932, 3349 cm−1; UV/Vis (CH2Cl2): λmax (ε)=245 (187 000), 271 (144 000), 282 (153 000), 316 (95 800), 334 nm (77 400 M−1 cm−1); HRMS (ESI): m/z calcd for C392H472N20O88+3 H+2 Na2+: 3458.1547 [M+3 H+2 Na2+]; found: 3458.1592.

Compound 6 a: Bisfullerene 5 a (28.7 mg, 4.18 μmol) was dissolved in pure TFA (5 mL) and the solution was stirred at room temperature for 24 h. The excess amount of TFA was removed under vacuum and coevaporated with methanol several times to give 6 a as a yellow solid (24.2 mg, 4.14 μmol, 99.0 %). 1H NMR (400 MHz, CD3OD, RT): δ=1.42 (m, 88 H; CH2), 1.65 (m, 48 H; CH2), 1.74 (m, 48 H; CH2), 2.93 (t, 3J=7.4 Hz, 40 H; CH2NH), 4.34 ppm (m, 48 H; OCH2); 13C NMR (100 MHz, CD3OD, RT): δ=26.62 (20 C; CH2), 27.09, 27.10 (20 C; CH2), 27.30 (4 C; CH2), 28.55 (20 C; CH2), 29.45 (20 C; CH2), 29.86 (4 C; CH2), 30.79 (4 C; CH2), 40.78 (20 C; CH2NH), 47.70, 47.80, 47.82 (12 C; OCCCO), 68.42 (20 C; OCH2), 68.81 (4 C; OCH2), 70.74, 70.77, 70.82 (24 C; C60‐sp3), 118.48 (q, 1J=292 Hz, 20 C; CF3COO−), 142.85, 142.85, 142.88, 142.89, 142.91, 142.93, 147.01, 147.02, 147.04, 147.08, 147.12 (96 C; C60‐sp2), 163.32 (q, 2J=34 Hz, 20 C; CF3COO−), 165.03, 165.10, 165.11 ppm (24 C; CO); FTIR (ATR): $\tilde \nu $=670, 720, 761, 799, 835, 899, 976, 1081, 1129, 1177, 1199, 1226, 1271, 1353, 1396, 1430, 1464, 1531, 1673, 1741, 2861, 2936 cm−1; UV/Vis (MeOH): λmax=242, 271, 280, 315, 333 nm.

Compound 6 b: Bisfullerene 5 b24 (24.3 mg, 3.86 μmol) was dissolved in pure TFA (5 mL) and the solution was stirred at room temperature for 24 h. The excess amount of TFA was removed under vacuum and coevaporated with methanol several times to give 6 b as a yellow solid (19.6 mg, 3.79 μmol, 98.2 %). 1H NMR (400 MHz, CD3OD, RT): δ=1.41 (m, 56 H; CH2), 1.61 (m, 40 H; CH2), 1.72 (m, 48 H; CH2), 2.28 (t, 3J=7.3 Hz, 40 H; CH2CO), 4.33 ppm (m, 28 H; OCH2); 13C NMR (100 MHz, CD3OD, RT): δ=25.83 (20 C; CH2), 26.85 (20 C; CH2), 27.14 (4 C; CH2), 29.55 (20 C; CH2), 29.83 (4 C; CH2), 30.51 (4 C; CH2), 35.05 (20 C; CH2CO), 47.59, 47.72, 47.75 (12 C; OCCCO), 68.36 (20 C; OCH2), 68.64 (4 C; OCH2), 70.73, 70.76, 70.78, 70.83 (24 C; C60‐sp3), 142.85, 142.90, 142.92, 142.94, 147.06, 147.08, 147.09, 147.14, 147.18 (96 C; C60‐sp2), 165.07, 165.08, 165.15 (24 C; CO), 177.82 ppm (20 C; COOH); FTIR (ATR): $\tilde \nu $=668, 713, 759, 826, 870, 939, 988, 1078, 1204, 1261, 1353, 1400, 1458, 1701, 1735, 2864, 2938 cm−1; UV/Vis (MeOH): λmax=244, 271, 280, 316, 333 nm.

Compound 8 a: Compound 2 a (121 mg, 33.0 μmol, 6.0 equiv), 739 (7.47 mg, 5.50 μmol, 1.0 equiv), and CBr4 (182 mg, 550 μmol, 100 equiv) were dissolved in dry toluene (2 mL) under a nitrogen atmosphere. DBU (9.87 μL, 66.0 μmol, 12.0 equiv) was added. The reaction mixture was stirred for 7 days and filtered through a silica‐gel plug with toluene→ethyl acetate. The product was purified by preparative recycling GPC affording 8 a (5.0 mg, 0.406 μmol, 7.39 %) and 15 a (42.4 mg, 11.1 μmol, 33.6 % based on 2 a) as yellow solids. Compound 8 a: Rf=0.46 (toluene/ethyl acetate 1:1); 1H NMR (400 MHz, CDCl3, RT): δ=0.81 (m, 3 H; CH2), 1.14 (m, 18 H; CH2), 1.27–1.48 (m, 231 H; CH2), 1.41 (270 H; CH3), 1.58 (m, 9 H; CH2), 1.66 (m, 87 H; CH2), 3.07 (m, 60 H; CH2NH), 4.23 (t, 3J=6.2 Hz, 72 H; OCH2), 3.97, 4.12, 4.30, 4.67 (m, 24 H; OCH2), 4.77 ppm (br, 30 H; NH); 13C NMR (100.5 MHz, CDCl3, RT): δ=25.75 (30 C; CH2), 26.24 (18 C; CH2‐macrocycles), 26.56 (30 C; CH2), 28.52 (30 C; CH2), 28.63 (90 C; CH3), 28.73 (18 C; CH2‐macrocycles), 29.69 (18 C; CH2‐macrocycles), 30.13 (30 C; CH2), 40.68 (30 C; CH2NH), 45.66 (24 C; OCCCO), 67.09, 67.38 (48 C; OCH2), 69.31, 69.35, 69.51 (48 C; C60‐sp3), 79.14 (30 C; C(CH3)3), 141.44, 146.03, 146.15 (192 C; C60‐sp2), 156.36 (30 C; COOtBu), 164.18 ppm (48 C; CO); FTIR (ATR): $\tilde \nu $=419, 526, 667, 713, 757, 864, 990, 1044, 1078, 1164, 1210, 1257, 1364, 1390, 1456, 1513, 1708, 1740, 2857, 2926, 3356, 3405 cm−1; UV/Vis (CH2Cl2): λmax (ε)=245 (353 000), 271 (275 000), 282 (285 000), 316 (179 000), 335 nm (144 000 M−1 cm−1); HRMS (ESI): m/z calcd for C714H804N30O156+5 Na5+: 2481.907937 [M+5 Na5+]; found: 2481.909286.

Compound 9 a: Compound 8 a (4.0 mg, 0.325 μmol) was dissolved in pure TFA (5 mL) and the solution was stirred at room temperature for 24 h. The excess amount of TFA was removed under vacuum and coevaporated with methanol several times to give 9 a as a yellow solid (3.7 mg, 0.320 μmol, 98.5 %). 1H NMR (400 MHz, CD3OD, RT): δ=0.88 (m, 3 H; CH2), 1.19 (m, 18 H; CH2), 1.27–1.49 (m, 231 H; CH2), 1.58 (m, 9 H; CH2), 1.66 (m, 84 H; CH2), 1.74 (m, 87 H; CH2), 2.93 (t, 3J=7.6 Hz, 60 H; CH2NH), 4.34 ppm (m, 96 H; OCH2); 13C NMR (100.5 MHz, CD3OD, RT): δ=26.65 (30 C; CH2), 26.93, 27.39, 27.84 (18 C; CH2‐macrocycles), 27.13 (30 C; CH2), 28.58 (30 C; CH2), 29.52 (30 C; CH2), 29.86 (18 C; CH2‐macrocycles), 30.56, 30.70, 30.88 (18 C; CH2‐macrocycles), 40.79 (30 C; CH2NH), 47.80 (24 C; OCCCO), 68.45, 68.80 (48 C; OCH2), 70.78, 71.16 (48 C; C60‐sp3), 116.29 (q, 1J=283 Hz, 30 C; CF3COO−), 142.92, 142.97, 146.99, 147.09, 147.22 (192 C; C60‐sp2), 159.29 (q, 2J=42 Hz, 30 C; CF3COO−), 165.08, 165.14 ppm (48 C; CO); FTIR (ATR): $\tilde \nu $=670, 715, 760, 798, 835, 890, 990, 1043, 1082, 1128, 1200, 1263, 1355, 1394, 1433, 1462, 1530, 1673, 1739, 2854, 2923 cm−1; UV/Vis (MeOH): λmax=243, 271, 280, 315, 333 nm.

Compound 8 b: Compound 2 b24 (116 mg, 34.5 μmol, 6.0 equiv), 739 (7.80 mg, 5.75 μmol, 1.0 equiv), and CBr4 (191 mg, 575 μmol, 100 equiv) were dissolved in dry toluene (2 mL) under a nitrogen atmosphere. DBU (10.3 μL, 69.0 μmol, 12.0 equiv) was added. The reaction mixture was stirred for 7 days and filtered through a silica‐gel plug with toluene→ethyl acetate. The product was purified by preparative recycling GPC affording 8 b (6.9 mg, 0.604 μmol, 10.5 %) and 15 b (38.0 mg, 10.8 μmol, 31.3 % based on 2 b) as yellow solids. Compound 8 b: Rf=0.52 (toluene/ethyl acetate 8:2); 1H NMR (400 MHz, CDCl3, RT): δ=0.78 (m, 3 H; CH2), 1.14 (m, 18 H; CH2), 1.36 (m, 111 H; CH2), 1.41 (270 H; CH3), 1.58 (m, 81 H; CH2), 1.68 (75 H; CH2), 2.19 (t, 3J=7.6 Hz, 60 H; CH2CO), 4.22 (t, 3J=6.6 Hz, 72 H; OCH2), 3.97, 4.12, 4.29, 4.66 ppm (m, 24 H; OCH2); 13C NMR (100.5 MHz, CDCl3, RT): δ=24.80 (30 C; CH2), 25.48 (30 C; CH2), 26.21, 26.30, 26.55, 26.82 (18 C; CH2‐macrocycles), 28.29 (90 C; CH3), 28.35 (30 C; CH2), 28.63, 28.68, 28.73, 28.97 (18 C; CH2‐macrocycles), 29.35, 29.56, 29.67, 29.73 (18 C; CH2‐macrocycles), 35.49 (30 C; CH2CO), 45.51 (18 C; OCCCO), 45.72 (3 C; OCCCO), 46.87 (3 C; OCCCO), 66.91, 67.11, 67.16, 67.27 (48 C; OCH2), 69.28, 69.34, 69.47, 69.52 (48 C; C60‐sp3), 80.26 (30 C; C(CH3)3), 141.37, 146.10 (144 C; C60‐sp2), 140.84, 140.90, 141.02, 142.18, 142.24, 142.32, 145.13, 145.24, 145.60, 145.87, 146.45, 146.98 (48 C; C60‐sp2), 163.52, 163.91, 163.97, 164.09 (48 C; CO), 173.11 ppm (30 C; COOtBu); FTIR (ATR): $\tilde \nu $=466, 527, 667, 714, 756, 845, 943, 990, 1076, 1148, 1208, 1258, 1365, 1459, 1725, 2853, 2933 cm−1; UV/Vis (CH2Cl2): λmax (ε)=245 (277 000), 272 (209 000), 282 (222 000), 317 (143 000), 335 nm (115 000 M−1 cm−1); HRMS (ESI): m/z calcd for C684H714O156+4 Na4+: 2878.68821 [M+4 Na4+]; found: 2878.69575.

Compound 9 b: Compound 8 b (5.9 mg, 0.516 μmol) was dissolved in pure TFA (5 mL) and the solution was stirred at room temperature for 24 h. The excess amount of TFA was removed under vacuum and coevaporated with methanol several times to give 9 b as a yellow solid (4.9 mg, 0.503 μmol, 97.5 %). 1H NMR (400 MHz, CD3OD, RT): δ=0.90 (m, 3 H; CH2), 1.14 (m, 18 H; CH2), 1.41 (m, 111 H; CH2), 1.60 (m, 81 H; CH2), 1.72 (75 H; CH2), 2.29 (m, 60 H; CH2CO), 4.33 ppm (m, 96 H; OCH2); 13C NMR (100.5 MHz, CD3OD, RT): δ=25.84 (30 C; CH2), 26.88 (30 C; CH2), 27.29 (18 C; CH2‐macrocycles), 29.61 (30 C; CH2), 30.09 (18 C; CH2‐macrocycles), 30.87 (18 C; CH2‐macrocycles), 35.00 (30 C; CH2CO), 47.64 (24 C; OCCCO), 68.41 (48 C; OCH2), 70.78 (48 C; C60‐sp3), 142.89, 147.16 (192 C; C60‐sp2), 165.15 (48 C; CO), 177.74 ppm (30 C; COOH); FTIR (ATR): $\tilde \nu $=665, 671, 714, 759, 827, 940, 991, 1078, 1205, 1262, 1354, 1398, 1460, 1705, 1738, 2859, 2930 cm−1; UV/Vis (MeOH): λmax=244, 271, 281, 315, 333 nm.

Compound 11 a: Compound 2 a (235 mg, 64.3 μmol, 10.0 equiv), 1032–34 (5.68 mg, 6.43 μmol, 1.0 equiv), and CBr4 (213 mg, 643 μmol, 100 equiv) were dissolved in dry toluene (6 mL) under a nitrogen atmosphere. DBU (19.2 μL, 129 μmol, 20.0 equiv) was added. The reaction mixture was stirred for 7 days and filtered through a silica‐gel plug with toluene→ethyl acetate. The product was purified by preparative recycling GPC affording 11 a (32.5 mg, 1.70 μmol, 26.4 %) and 15 a (82.0 mg, 21.5 μmol, 33.4 % based on 2 a) as yellow solids. Compound 11 a: Rf=0.21 (toluene/ethyl acetate 1:1); 1H NMR (400 MHz, CDCl3, RT): δ=1.32 (m, 240 H; CH2), 1.40 (s, 450 H; CH3), 1.43 (m, 140 H; CH2), 1.66 (m, 140 H; CH2), 2.95 (s, 6 H; N(CH3)2), 3.06 (m, 100 H; CH2NH), 4.22 (m, 120 H; OCH2), 4.78 (br, 50 H; NH), 6.64 (d, 3J=8.5 Hz, 2 H; Hmeta), 7.86 ppm (d, 3J=8.2 Hz, 2 H; Hortho); 13C NMR (100.5 MHz, CDCl3, RT): δ=25.76 (50 C; CH2), 26.27 (20 C; CH2), 26.58 (50 C; CH2), 28.53 (50 C; CH2), 28.65 (170 C; CH3, CH2), 29.72, 29.76 (20 C; CH2), 30.14 (50 C; CH2), 40.26 (2 C; N(CH3)2), 40.68 (50 C; CH2NH), 45.53, 45.63 (35 C; OCCCO), 67.06 (50 C; OCH2), 67.31 (20 C; OCH2), 69.26, 69.30 (70 C; C60‐sp3), 79.08 (50 C; C(CH3)3), 141.30, 145.89 (240 C; C60‐sp2), 156.22 (50 C; COOtBu), 164.03 ppm (70 C; CO); FTIR (ATR): $\tilde \nu $=464, 525, 661, 713, 758, 862, 986, 1042, 1076, 1164, 1209, 1247, 1363, 1390, 1455, 1691, 1740, 2857, 2928, 3345 cm−1; UV/Vis (CH2Cl2): λmax (ε)=245 (511 000), 271 (394 000), 282 (416 000), 315 (277 000), 333 nm (219 000 M−1 cm−1).

Compound 11 b: Compound 2 b24 (281 mg, 83.6 μmol, 10.0 equiv), 1032–34 (7.38 mg, 8.36 μmol, 1.0 equiv), and CBr4 (277 mg, 836 μmol, 100 equiv) were dissolved in dry toluene (7 mL) under a nitrogen atmosphere. DBU (25.0 μL, 167 μmol, 20.0 equiv) was added. The reaction mixture was stirred for 7 days and filtered through a silica‐gel plug with toluene→ethyl acetate. The product was purified by preparative recycling GPC affording 11 b (41.9 mg, 2.37 μmol, 28.4 %) and 15 b (126 mg, 35.9 μmol, 42.9 % based on 2 b) as yellow solids. Compound 11 b: Rf=0.45 (toluene/ethyl acetate 8:2); 1H NMR (400 MHz, CDCl3, RT): δ=1.35 (m, 180 H; CH2), 1.41 (s, 450 H; CH3), 1.58 (m, 120 H; CH2), 1.68 (m, 120 H; CH2), 2.18 (t, 3J=7.4 Hz, 100 H; CH2CO), 2.95 (s, 6 H; N(CH3)2), 4.21 (t, 3J=6.4 Hz, 120 H; OCH2), 6.64 (d, 3J=9.1 Hz, 2 H; Hmeta), 7.85 ppm (d, 3J=8.4 Hz, 2 H; Hortho); 13C NMR (100.5 MHz, CDCl3, RT): δ=24.82 (50 C; CH2), 25.50 (50 C; CH2), 26.26, 26.28 (20 C; CH2), 28.31 (150 C; CH3), 28.37 (50 C; CH2), 28.70 (20 C; CH2), 29.72, 29.76 (20 C; CH2), 35.50 (50 C; CH2CO), 40.24 (2 C; N(CH3)2), 45.47 (35 C; OCCCO), 66.89 (50 C; OCH2), 67.28 (20 C; OCH2), 69.23, 69.30 (70 C; C60‐sp3), 80.22 (50 C; C(CH3)3), 111.73 (2 C; Cmeta), 129.72 (2 C; Cortho), 141.23, 145.95 (240 C; C60‐sp2), 163.93 (70 C; CO), 172.96 ppm (50 C; COOtBu); FTIR (ATR): $\tilde \nu $=665, 672, 714, 759, 846, 942, 989, 1043, 1077, 1147, 1208, 1259, 1365, 1391, 1457, 1723, 2862, 2934 cm−1; UV/Vis (CH2Cl2): λmax (ε)=245 (557 000), 272 (424 000), 282 (453 000), 316 (305 000), 333 nm (241 000 M−1 cm−1); HRMS (ESI): m/z calcd for C1054H1120N2O241+6 Na6+: 2966.247203 [M+6 Na6+]; found: 2966.238496.

Compound 12 a: Compound 11 a (31.7 mg, 1.66 μmol, 1.0 equiv) was dissolved together with maleic anhydride (32.6 mg, 332 μmol, 200 equiv) in dry toluene under a nitrogen atmosphere. The reaction mixture was irradiated with a halogen floodlight (500 W) while being cooled by a water bath to 15 °C for 24 h. The reaction mixture was filtered through a silica‐gel plug with toluene→ethyl acetate. The solution was concentrated and the product was purified by flash column chromatography (silica gel; toluene/ethyl acetate 60:40→20:80) affording 12 a (22.1 mg, 1.26 μmol, 75.9 %) as a dark yellow solid. Rf=0.33 (toluene/ethyl acetate 1:1); 1H NMR (400 MHz, CDCl3, RT): δ=1.32 (m, 240 H; CH2), 1.41 (s, 450 H; CH3), 1.43 (m, 140 H; CH2), 1.66 (m, 140 H; CH2), 3.07 (m, 100 H; CH2NH), 4.22 (m, 120 H; OCH2), 4.78 ppm (br, 50 H; NH); 13C NMR (100.5 MHz, CDCl3, RT): δ=25.79 (50 C; CH2), 26.34 (20 C; CH2), 26.60 (50 C; CH2), 28.56 (50 C; CH2), 28.67 (170 C; CH3, CH2), 29.82 (20 C; CH2), 30.17 (50 C; CH2), 40.70 (50 C; CH2NH), 45.67 (35 C; OCCCO), 66.63 (20 C; OCH2), 67.09 (50 C; OCH2), 69.29 (70 C; C60‐sp3), 79.11 (50 C; C(CH3)3), 141.34, 145.93 (240 C; C60‐sp2), 156.25 (50 C; COOtBu), 164.06 ppm (70 C; CO); FTIR (ATR): $\tilde \nu $=526, 661, 713, 756, 863, 987, 1042, 1076, 1164, 1210, 1364, 1391, 1454, 1512, 1693, 1740, 2858, 2929, 3354 cm−1; UV/Vis (CH2Cl2): λmax (ε)=245 (301 000), 271 (222 000), 281 (225 000), 315 (164 000), 333 nm (134 000 M−1 cm−1).

Compound 12 b: Compound 11 b (39.4 mg, 2.23 μmol, 1.0 equiv) was dissolved together with maleic anhydride (43.7 mg, 446 μmol, 200 equiv) in dry toluene under a nitrogen atmosphere. The reaction mixture was irradiated with a halogen floodlight (500 W) while being cooled by a water bath to 15 °C for 24 h. The reaction mixture was filtered through a silica‐gel plug with toluene→ethyl acetate. The solution was concentrated and the product was purified by flash column chromatography (silica gel; toluene→toluene/ethyl acetate 65:35) affording 12 b (29.3 mg, 1.67 μmol, 74.9 %) as a dark yellow solid. Rf=0.47 (toluene/ethyl acetate 8:2); 1H NMR (400 MHz, CDCl3, RT): δ=1.36 (m, 180 H; CH2), 1.41 (s, 450 H; CH3), 1.58 (m, 120 H; CH2), 1.68 (m, 120 H; CH2), 2.19 (t, 3J=7.3 Hz, 100 H; CH2CO), 4.22 ppm (t, 3J=6.4 Hz, 120 H; OCH2); 13C NMR (100.5 MHz, CDCl3, RT): δ=24.84 (50 C; CH2), 25.52 (50 C; CH2), 26.28 (20 C; CH2), 28.33 (150 C; CH3), 28.39 (50 C; CH2), 28.73 (20 C; CH2), 29.79 (20 C; CH2), 35.52 (50 C; CH2CO), 45.50 (35 C; OCCCO), 66.92 (50 C; OCH2), 67.29 (20 C; OCH2), 69.26, 69.31 (70 C; C60‐sp3), 80.27 (50 C; C(CH3)3), 141.26, 145.99 (240 C; C60‐sp2), 163.96 (70 C; CO), 173.02 ppm (50 C; COOtBu); FTIR (ATR): $\tilde \nu $=486, 527, 591, 670, 714, 755, 845, 945, 989, 1076, 1147, 1209, 1365, 1456, 1723, 2860, 2931 cm−1; UV/Vis (CH2Cl2): λmax (ε)=244 (331 000), 272 (245 000), 281 (251 000), 316 (174 000), 335 nm (139 000 M−1 cm−1).

Compound 13 a: Compound 12 a (3.4 mg, 0.179 μmol) was dissolved in pure TFA (5 mL) and the solution was stirred at room temperature for 24 h. The excess amount of TFA was removed under vacuum and coevaporated with methanol several times to give 13 a as a yellow solid (3.3 mg, 0.173 μmol, 96.6 %). 1H NMR (400 MHz, CD3OD, RT): δ=1.42 (m, 240 H; CH2), 1.65 (m, 140 H; CH2), 1.74 (m, 140 H; CH2), 2.93 (t, 3J=7.4 Hz, 100 H; CH2NH), 4.34 ppm (m, 120 H; OCH2); FTIR (ATR): $\tilde \nu $=722, 761, 799, 842, 1130, 1187, 1265, 1396, 1441, 1671, 2939, 3208 cm−1; UV/Vis (MeOH): λmax=243, 271, 280, 315, 334 nm.

Compound 13 b: Compound 12 b (4.0 mg, 0.228 μmol) was dissolved in pure TFA (5 mL) and the solution was stirred at room temperature for 24 h. The excess amount of TFA was removed under vacuum and coevaporated with methanol several times to give 13 b as a yellow solid (3.3 mg, 0.224 μmol, 98.2 %). 1H NMR (400 MHz, CDCl3, RT): δ=1.41 (m, 180 H; CH2), 1.66 (m, 120 H; CH2), 1.72 (m, 120 H; CH2), 2.33 (t, 3J=7.2 Hz, 100 H; CH2CO), 4.27 ppm (t, 3J=6.1 Hz, 120 H; OCH2); FTIR (ATR): $\tilde \nu $=610, 662, 675, 714, 827, 940, 988, 1077, 1166, 1206, 1261, 1356, 1436, 1456, 2854, 2924 cm−1; UV/Vis (CH2Cl2): λmax=244, 271, 281, 317, 335 nm.

Compound 14: Compound 2 b24 (110 mg, 32.7 μmol, 10.0 equiv), C60 (2.36 mg, 3.27 μmol, 1.0 equiv), and CBr4 (109 mg, 327 μmol, 100 equiv) were dissolved in dry toluene (2 mL) under a nitrogen atmosphere. DBU (9.78 μL, 65.5 μmol, 20.0 equiv) was added. The reaction mixture was stirred for 21 days and filtered through a silica‐gel plug with toluene→ethyl acetate. The product was purified by preparative recycling GPC affording 14 (2.2 mg, 0.105 μmol, 3.22 %) and 15 b (40.9 mg, 11.6 μmol, 35.5 % based on 2 b) as yellow solids. Rf=0.45 (toluene/ethyl acetate 8:2); 1H NMR (400 MHz, CDCl3, RT): δ=1.37 (m, 216 H; CH2), 1.42 (s, 540 H; CH3), 1.59 (m, 144 H; CH2), 1.69 (m, 144 H; CH2), 2.19 (t, 3J=7.4 Hz, 120 H; CH2CO), 4.23 ppm (t, 3J=6.4 Hz, 144 H; OCH2); 13C NMR (100.5 MHz, CDCl3, RT): δ=24.87 (60 C; CH2), 25.56 (84 C; CH2), 28.37 (180 C; CH3), 28.43 (60 C; CH2), 28.84 (24 C; CH2), 29.93 (24 C; CH2), 35.55 (60 C; CH2CO), 45.52 (42 C; OCCCO), 66.94, 66.96 (84 C; OCH2), 69.30 (84 C; C60‐sp3), 80.27 (60 C; C(CH3)3), 141.31, 146.03, 146.10 (336 C; C60‐sp2), 163.98 (84 C; CO), 173.00 ppm (60 C; COOtBu); FTIR (ATR): $\tilde \nu $=624, 662, 675, 714, 757, 845, 943, 989, 1078, 1148, 1212, 1259, 1366, 1391, 1456, 1724, 2856, 2927 cm−1; UV/Vis (CH2Cl2): λmax (ε)=245 (475 000), 270 (380 000), 281 (379 000), 317 (244 000), 335 nm (192 000 M−1 cm−1); HRMS (ESI): m/z calcd for C1242H1332O288+7 Na7+: 3001.983272 [M+7 Na7+]; found: 3001.979202.

Compound 1 b: Compound 14 (1.8 mg, 0.0863 μmol) was dissolved in pure TFA (5 mL) and the solution was stirred at room temperature for 24 h. The excess amount of TFA was removed under vacuum and coevaporated with methanol several times to give 1 b as a yellow solid (1.5 mg, 0.0857 μmol, 99.3 %). 1H NMR (400 MHz, CDCl3, RT): δ=1.37 (m, 216 H; CH2), 1.63 (m, 144 H; CH2), 1.69 (m, 144 H; CH2), 2.30 (t, 3J=7.6 Hz, 120 H; CH2CO), 4.24 ppm (t, 3J=5.6 Hz, 144 H; OCH2); FTIR (ATR): $\tilde \nu $=607, 617, 664, 673, 714, 759, 826, 940, 987, 1043, 1077, 1165, 1205, 1261, 1354, 1436, 1458, 1734, 2855, 2925 cm−1; UV/Vis (CH2Cl2): λmax=245, 271, 281, 317, 335 nm.

Compound 15 a: Compound 15 a was obtained as a byproduct in the synthesis of 8 a and 11 a. Rf=0.58 (toluene/ethyl acetate 1:1); 1H NMR (400 MHz, CDCl3, RT): δ=1.32 (m, 48 H; CH2), 1.40 (s, 90 H; CH3), 1.42 (m, 28 H; CH2), 1.66 (m, 28 H; CH2), 3.06 (m, 20 H; CH2NH), 4.22 (m, 24 H; OCH2), 4.26 (t, 3J=6.6 Hz, 4 H; OCH2), 4.76 ppm (br, 10 H; NH); 13C NMR (100.5 MHz, CDCl3, RT): δ=25.72 (10 C; CH2), 25.90, 26.09 (4 C; CH2), 26.53 (10 C; CH2), 28.49 (10 C; CH2), 28.60 (30 C; CH3), 28.64 (4 C; CH2), 29.42, 29.54 (4 C; CH2), 30.11 (10 C; CH2), 40.66 (10 C; CH2NH), 45.52, 45.63, 45.65, 45.66 (6 C; OCCCO), 51.37 (1 C; OCCBr2CO), 67.07 (10 C; OCH2), 67.24 (2 C; OCH2), 68.97 (2 C; OCH2), 69.27, 69.29, 69.32 (12 C; C60‐sp3), 79.11 (10 C; C(CH3)3), 141.35, 141.36, 141.41, 141.42, 145.97, 146.01, 146.05, 146.09 (48 C; C60‐sp2), 156.32 (10 C; COOtBu), 163.51 (2 C; CO), 164.10, 164.15 ppm (12 C; CO); FTIR (ATR): $\tilde \nu $=622, 658, 714, 732, 760, 780, 827, 864, 989, 1041, 1079, 1165, 1211, 1245, 1364, 1391, 1455, 1513, 1691, 1742, 2857, 2929, 3350 cm−1; UV/Vis (CH2Cl2): λmax (ε)=245 (108 000), 270 (84 200), 281 (86 500), 317 (55 200), 335 nm (44 100 M−1 cm−1); HRMS (ESI): m/z calcd for C207H252Br2N10O48+H+2 Na2+: 1925.2907 [M+H+2 Na2+]; found: 1925.2902.

Debromination was possible by using the following procedure: 15 a (173 mg, 45.4 μmol) was dissolved in toluene (25 mL). Zinc powder (1 g) and a saturated solution of NH4Cl (25 mL) were added to the solution and the mixture was vigorously stirred for 48 h. The mixture was filtered and the toluene layer was extracted with 10 % citric acid, a saturated solution of NaHCO3, brine, and water. The solvent was removed under vacuum and the product was filtered through a silica‐gel plug (toluene/ethyl acetate 50:50) to give 2 a as a yellow solid (157 mg, 43.0 μmol, 94.7 %).

Compound 15 b: Compound 15 b was obtained as a byproduct in the synthesis of 14, 8 b, and 11 b. Rf=0.59 (toluene/ethyl acetate 8:2); 1H NMR (400 MHz, CDCl3, RT): δ=1.32 (m, 36 H; CH2), 1.38 (s, 90 H; CH3), 1.55 (m, 24 H; CH2), 1.65 (m, 24 H; CH2), 2.16 (t, 3J=7.6 Hz, 20 H; CH2CO), 4.19 (m, 24 H; OCH2), 4.23 ppm (m, 4 H; OCH2); 13C NMR (100.5 MHz, CDCl3, RT): δ=24.68 (10 C; CH2), 25.37 (10 C; CH2), 25.81, 25.99 (4 C; CH2), 28.18 (30 C; CH3), 28.25 (10 C; CH2), 28.41, 28.55 (4 C; CH2), 29.33, 29.44 (4 C; CH2), 35.37 (10 C; CH2CO), 45.37, 45.40, 45.42 (6 C; OCCCO), 51.29 (1 C; OCCBr2CO), 66.80 (10 C; OCH2), 67.04 (2 C; OCH2), 68.88 (2 C; OCH2), 69.18, 69.22 (12 C; C60‐sp3), 80.14 (10 C; C(CH3)3), 141.25, 141.28, 145.96, 145.98, 146.00, 146.03 (48 C; C60‐sp2), 163.41 (2 C; CO), 163.96, 163.98, 164.02 (12 C; CO), 172.99 ppm (10 C; COOtBu); FTIR (ATR): $\tilde \nu $=634, 673, 715, 734, 759, 846, 942, 989, 1043, 1078, 1148, 1209, 1260, 1366, 1392, 1417, 1457, 1724, 2862, 2933 cm−1; UV/Vis (CH2Cl2): λmax (ε)=245 (94 300), 272 (71 000), 281 (76 200), 317 (48 300), 335 nm (39 100 M−1 cm−1); HRMS (ESI): m/z calcd for C197H222Br2O48+Na+: 3536.3190 [M+Na+]; found: 3536.3280.

Debromination was possible by using the following procedure: 15 b (151 mg, 42.9 μmol) was dissolved in toluene (25 mL). Zinc powder (1 g) and a saturated solution of NH4Cl (25 mL) was added to the solution and the mixture was vigorously stirred for 48 h. The mixture was filtered and the toluene layer was extracted with 10 % citric acid, a saturated solution of NaHCO3, brine, and water. The solvent was removed under vacuum and the product was filtered through a silica‐gel plug (toluene/ethyl acetate 80:20) to give 2 b as a yellow solid (134 mg, 39.9 μmol, 93.0 %).

We thank the Deutsche Forschungsgemeinschaft (SFB 953 (Synthetic Carbon Allotropes) and HI 468/13‐4) for financial support.

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Graph: 1 Bis‐, tetra‐, hexa‐, and heptafullerene motifs for the construction of spherical polyelectrolytes. Type I: Bisfullerene with two identical sets of addends; type II: tetrafullerene with three identical sets of addends; type III: hexafullerene with five identical sets of addends; type IV: heptafullerene with six identical sets of addends.

Graph: image_n/nfig001.gif

Graph: 1 Synthesis of 2 a and 5 a: a) CBr4, DBU, toluene, 24 h.

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Graph: 2 Synthesis of 6 a and 6 b: a) TFA, 24 h.

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Graph: 3 Synthesis of 8 a,b and 9 a,b: a) CBr4, DBU, toluene, 7 d; b) TFA, 24 h.

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Graph: 2 13C NMR spectrum of 8 b (100.5 MHz, RT, CDCl3).

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Graph: 4 Synthesis of 11 a,b, 12 a,b, and 13 a,b: a) CBr4, DBU, toluene, 7 d; b) maleic anhydride, hν, toluene, 24 h; c) TFA, 24 h.

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Graph: 3 1H NMR spectrum of 11 b (top), 12 b (middle), and 13 b (bottom) (400 MHz, RT, CDCl3).

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Graph: 5 Synthesis of 14 and 1 b: a) CBr4, DBU, toluene, 21 d; b) TFA, 24 h.

Graph: image_n/nsch005.gif

Graph: 6 Debromination of 15 a and 15 b: a) zinc dust, NH4Cl, water, toluene, 2 d.

Graph: image_n/nsch006.gif

Graph: 4 13C NMR spectrum of 15 b and 2 b (100.5 MHz, RT, CDCl3).

Graph: image_n/nfig004.gif

Graph: 7 Supposed mechanism of the modified hexakisadduct synthesis.

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Graph: miscellaneous_information