Photodynamic Activity of C70 Caged within Surface‐Cross‐Linked Liposomes

[70]Fullerene (C₇₀) encapsulated into a surface‐cross‐linked liposome, a so‐called cerasome, was prepared by an exchange reaction incorporating C₇₀?γ‐cyclodextrin complexes into lipid membranes. Fullerene exchange in a cerasome‐incorporated C₇₀ (CIC₇₀), as well as in a lipid‐membrane‐incorporated C₇₀ (LMIC₇₀), was completed within 1 min with stirring at 25 °C. CIC₇₀ was more resistant to lysis than LMIC₇₀ towards lysing agents such as surfactants. Furthermore, the photodynamic activity of CIC₇₀ in HeLa cells was similar to that of LMIC₇₀, indicating that C₇₀ can act as a photosensitizing drug (PS) without release from cerasome membranes. Thus, in contrast with general drug‐delivery systems (DDSs), which require the drug to be released from the interior of liposomes, carriers for PSs for use in photodynamic therapy (PDT) do not necessarily need to release the drug. These results indicate that DDSs with high morphological stability can increase the residence time in blood and achieves tumor‐selective drug delivery by the enhanced permeability and retention (EPR) effect.     

Size‐ and Orientation‐Selective Encapsulation of C70 by Cycloparaphenylenes

The size‐ and orientation‐selective formation of the shortest‐possible C₇₀ peapod in solution and in the solid state by using the shortest structural unit of an “armchair” carbon nanotube (CNT), cycloparaphenylene (CPP), has been studied. [10]CPP and [11]CPP exothermically formed 1:1 complexes with C₇₀, thereby giving the resulting peapods. A van′t Hoff plot analysis revealed that the formation of these complexes in 1,2‐dichlorobenzene was mainly driven by entropy, whereas the theoretical calculations suggested that the formation of the complex in the gas phase was predominantly driven by enthalpy. C₇₀ was found to exist in two distinct orientations inside the CPP cavity, namely “lying” and “standing”, depending on the specific size of the CPP. The theoretical calculations and the X‐ray crystallographic analysis revealed that the interactions between [10]CPP and the short axis of C₇₀ in its lying orientation were isotropic and similar to those observed between [10]CPP and C₆₀. However, the interactions between [11]CPP and C₇₀ in its standing orientation were anisotropic, thereby involving the radial deformation of [11]CPP into an ellipsoidal shape. This “induced fit” maximized the van der Waals interactions with the long axis of C₇₀. Theoretical calculations revealed that the deformation occurred readily with low energy loss, thus suggesting that CPPs are highly radially elastic molecules. These results also indicate that the same type of radial deformation should occur in CNT peapods that encapsulate anisotropic fullerenes.     

Efficient Synthesis,Structure, and Complexation Studies of Electron‐Donating Thiacalix[n]dithienothiophene

A series of thiacalix[n]dithiothiophenes (n=4–10) was prepared by a facile method and X‐ray analysis was used to determine the molecular structures of square‐ (4‐mer) and pentagonal‐shaped macrocycles (5‐mer). In the cyclic voltammograms, reversible multielectron redox processes, which are due to electronic delocalization, were observed at low oxidation potentials. The cyclic 4‐mer acted as a “Janus‐head” cavitand for two C₆₀ molecules, whereas the 5‐ and 6‐mer formed stable 1:1 complexes with C₆₀ .     

Efficient Synthesis,Structure, and Complexation Studies of Electron‐Donating Thiacalix[n]dithienothiophene

A series of thiacalix[n]dithiothiophenes (n=4–10) was prepared by a facile method and X‐ray analysis was used to determine the molecular structures of square‐ (4‐mer) and pentagonal‐shaped macrocycles (5‐mer). In the cyclic voltammograms, reversible multielectron redox processes, which are due to electronic delocalization, were observed at low oxidation potentials. The cyclic 4‐mer acted as a “Janus‐head” cavitand for two C₆₀ molecules, whereas the 5‐ and 6‐mer formed stable 1:1 complexes with C₆₀ .     

Photodynamic Activity of Fullerenes and Other Molecules Incorporated into Lipid Membranes by Exchange

An effective exchange method is described whereby liposomal drug carriers of hydrophobic guest biomolecules are used to incorporate the guests into lipid membranes. The exchange method transfers the guest molecule from a cyclodextrin cavity to a liposome in water. Lipid‐membrane‐incorporated fullerenes (LMIC_x: x = 60 or 70) prepared by the exchange method have much higher liposomal stability and fullerene water solubility than those prepared by conventional methods. The LMIC₆₀ have high photodynamic activities with respect to human cancer cells under 350–500 nm excitation. Furthermore, the LMIC₆₀ bilayers, containing light‐harvesting antenna molecules in addition to the C₆₀, showed improved activities at the optimal wavelength for photodynamic therapy.

     

Heteroanalogues of PCBM: N‐Bridged Imino‐PCBMs for Organic Field‐Effect Transistors

Crossing the bridge : Two isomeric iminofullerenes, [5,6]‐open azafulleroid 1 and [6,6]‐closed aziridinofullerene 2 , were prepared by cycloaddition of an organic azide to C₆₀. These “azalogues” enable the study of the effects of the bridging atom in a fullerene cage, that is, C₆₀‐like (5,6‐open) versus PCBM‐like (6,6‐closed), as a function of their π systems (PCBM=[6,6]‐phenyl‐C₆₁‐butyric acid methyl ester).

     

Hydrophobicity‐Driven Self‐Assembly of an Eighteen‐Membered Honeycomb Lattice with Almost Classical Spins

The design and synthesis of model compounds that do not exist naturally is one of the important targets in modern coordination chemistry. Herein, an eighteen‐membered honeycomb structure with equal numbers of Mn^II (s=5/2) and Gd^III (s=7/2) metal centers has been prepared, for the first time, by using a hydrophobic force‐directed self‐assembling process. Due to the weakly coupled Gd^III pairs, the magnetic properties are mainly determined by eight‐membered chains in the experimentally considered temperature range. These [Mn₄Gd₄] ”finite‐size“ chains, albeit with large Hilbert space, can be fully resolved by the high‐temperature series expansion and the powerful finite‐temperature Lanczos method, which reveal that the exchange‐couplings between the metal centers are antiferromagnetic and consistent with the magnetization measurement. Interestingly, from the surface‐engineering point of view, the [Mn₄Gd₄] chains are ”precisely“ assembled into a 2D honeycomb pattern, which is potentially desirable in the design of weakly coupled qubits.     

Liquid‐Crystalline Mixed [5 : 1]Hexa‐adducts of [60]Fullerene. Preliminary Communication

A liquid‐crystalline mixed [5 : 1]hexa‐adduct of [60]fullerene was synthesized by addition of two different malonate derivatives onto C₆₀. The hexa‐adduct derivative 2 was prepared by a stepwise synthetic procedure (fullerene→mono‐adduct of C₆₀→hexa‐adduct of C₆₀). Cyanobiphenyl and octyloxybiphenyl derivatives were selected as mesogens. The malonate derivatives showed either a monotropic nematic phase or a monotropic smectic A phase, and the hexa‐adduct derivative gave rise to an enantiotropic smectic A phase.     

Isoindigo‐3,4‐Difluorothiophene Polymer Acceptors Yield “All‐Polymer” Bulk‐Heterojunction Solar Cells with over 7 % Efficiency

Poly(isoindigo‐alt‐3,4‐difluorothiophene) (PIID[2F]T) analogues used as “polymer acceptors” in bulk‐heterojunction (BHJ) solar cells achieve >7 % efficiency when used in conjunction with the polymer donor PBFTAZ (model system; copolymer of benzo[1,2‐b:4,5‐b′]dithiophene and 5,6‐difluorobenzotriazole). Considering that most efficient polymer‐acceptor alternatives to fullerenes (e.g. PC₆₁BM or its C₇₁ derivative) are based on perylenediimide or naphthalenediimide motifs thus far, branched alkyl‐substituted PIID[2F]T polymers are particularly promising non‐fullerene candidates for “all‐polymer” BHJ solar cells.     

Stimuli‐Responsive Water‐Soluble Fullerene (C60) Polymeric Systems

This review documents the advances in stimuli‐responsive water‐soluble fullerene (C₆₀) polymeric systems. Stimuli‐responsive polymers, when grafted onto C₆₀ impart “smart” and “responsive” characteristics, and these novel materials adopt various morphologies when subjected to external stimuli, such as pH, temperature, and salt. Various synthetic approaches for producing C₆₀‐polymers are outlined and discussed. The responsive behavior, water solubility, and self‐assembly characteristics of these C₆₀‐polymers make them attractive for applications such as drug delivery, temperature sensors, and personal care.     

[6,6]‐Open and [6,6]‐Closed Isomers of C70(CF2): Synthesis,Electrochemical and Quantum Chemical Investigation

Novel difluoromethylenated [70]fullerene derivatives, C₇₀(CF₂)_n (n=1–3), were obtained by the reaction of C₇₀ with sodium difluorochloroacetate. Two major products, isomeric C₇₀(CF₂) mono‐adducts with [6,6]‐open and [6,6]‐closed configurations, were isolated and their homofullerene and methanofullerene structures were reliably determined by a variety of methods that included X‐ray analysis and high‐level spectroscopic techniques. The [6,6]‐open isomer of C₇₀(CF₂) constitutes the first homofullerene example of a non‐hetero [70]fullerene derivative in which functionalisation involves the most reactive bond in the polar region of the cage. Voltammetric estimation of the electron affinity of the C₇₀(CF₂) isomers showed that it is substantially higher for the [6,6]‐open isomer (the 70‐electron π‐conjugated system is retained) than the [6,6]‐closed form, the latter being similar to the electron affinity of pristine C₇₀. In situ ESR spectroelectrochemical investigation of the C₇₀(CF₂) radical anions and DFT calculations of the hyperfine coupling constants provide evidence for the first example of an inter‐conversion between the [6,6]‐closed and [6,6]‐open forms of a cage‐modified fullerene driven by an electrochemical one‐electron transfer. Thus, [6,6]‐closed C₇₀(CF₂) constitutes an interesting example of a redox‐switchable fullerene derivative.     

Addition of S‐Heterocyclic Carbenes to Fullerenes: Formation and Characterization of Dithiomethano‐Bridged Derivatives

The reactions of novel S‐heterocyclic carbenes (SHCs), which were prepared by the cycloaddition of disilenes and digermenes to CS₂, with C₆₀ and Sc₃N@I_h‐C₈₀ afforded the corresponding methano‐bridged fullerenes. The [6,6]‐closed and [6,6]‐open structures were characterized for the SHC adducts of C₆₀ and Sc₃N@I_h‐C₈₀, respectively. These derivatives exhibited relatively low oxidation potentials, indicative of the electron‐donating effects of the SHC addends. The electronic properties of the SHC derivatives were clarified by the density functional theory calculations.     

Synthesis of new methylated thieno[2,3‐a] and [3,2‐b]carbazoles by reductive cyclization of 6‐(2′‐Nitrophenyl)benzo[b]thiophenes obtained by palladium‐catalyzed cross‐coupling isabel

The synthesis of new methylated thieno[2,3‐a] and [3,2‐b]carbazoles (5) (R=H) was achieved by a palladium‐catalyzed cross‐coupling, intramolecular reductive cyclization sequence of reactions. The cyclization precursors 6‐(2′‐nitrophenyl)benzo[b]thiophenes (3) were obtained by Suzuki cross‐coupling of 6‐boronated methylbenzo[b]thiophenes intermediates (2) with 2‐bromo or iodonitrobenzene. The boronated intermediates (2) were prepared via bromine‐lithium exchange followed by boron transmetalation and coupled in situ using Pd(OAc)₂ giving thus a “one‐pot” three steps reaction from the 6‐bromobenzo[b]thio‐phenes (1) to the cyclization precursors (3) . In the reductive cyclization step, N‐ethylthienocarbazoles (5) (R=Et) were also obtained. Several experiments have been made varying the amount of triethylphosphite and the time of reaction, to avoid their formation.     

Ionic Liquid‐Carbon Nanotube Modified Screen‐Printed Electrodes and Their Potential for Adsorptive Stripping Voltammetry

Compared with paraffin oil, the use of ionic liquids as a binder in carbon paste type electrodes was shown to greatly enhance the accumulation of analytes, as illustrated with 17α‐ethynylestradiol as a model. The ionic “liquid” n‐octyl‐pyridinium hexafluorophosphate [C₈py][PF₆] was most efficient among several ionic liquids investigated. Such preconcentration allowed a [C₈py][PF₆]‐multiwalled carbon nanotubes (MWCNTs) (95 : 5 w/w) composite electrode to be useful for adsorptive stripping voltammetry. Screen‐printed electrodes modified with [C₈py][PF₆]‐MWCNTs were developed and were able to achieve high sensitivity during adsorptive stripping voltammetric measurements under optimised conditions.     

A halide‐free pyridinium‐substituted η3‐cycloheptatrienide–Pd complex

We report the synthesis and characterization of a novel 4‐(dimethylamino)pyridinium‐substituted η³‐cycloheptatrienide–Pd complex which is free of halide ligands. Diacetonitrile{η³‐[4‐(dimethylamino)pyridinium‐1‐yl]cycloheptatrienido}palladium(II) bis(tetrafluoroborate), [Pd(C₂H₃N)₂(C₁₄H₁₆N₂)](BF₄)₂, was prepared by the exchange of two bromide ligands for noncoordinating anions, which results in the empty coordination sites being occupied by acetonitrile ligands. As described previously, exchange of only one bromide leads to a dimeric complex, di‐μ‐bromido‐bis({η³‐[4‐(dimethylamino)pyridinium‐1‐yl]cycloheptatrienido}palladium(II)) bis(tetrafluoroborate) acetonitrile disolvate, [Pd₂Br₂(C₁₄H₁₆N₂)₂](BF₄)₂·2CH₃CN, with bridging bromide ligands, and the crystal structure of this compound is also reported here. The structures of the cycloheptatrienide ligands of both complexes are analogous to the dibromide derivative, showing the allyl bond in the β‐position with respect to the pyridinium substituent. This indicates that, unlike a previous interpretation, the main reason for the formation of the β‐isomer cannot be internal hydrogen bonding between the cationic substituents and bromide ligands.     

Alkali‐Metal Trichloroacetates for Dichloromethylenation of Fullerenes: Nucleophilic Addition‐Substitution Route

The first experimental evidence that fullerenes react with alkali‐metal trichloroacetates through a nucleophilic addition‐substitution route, yielding dichloromethylenefullerenes as the final products, is reported. The intermediates, C₆₀(CCl₃)^? and C₇₀(CCl₃)^? anions, have been isolated in their protonated forms as ortho‐C₆₀(CCl₃)H, as well as three ortho and one para isomer of C₇₀(CCl₃)H. The structures were unambiguously determined by means of ¹H, ¹³C, and ¹H–¹³C HMBC NMR spectroscopy along with UV/Vis spectroscopy. The observed regiochemistry was analyzed with the aid of quantum chemical calculations. Conversion of the protonated compounds into the [6,6]‐closed C_60/70(CCl₂) cycloadducts under basic conditions can be effected only for the ortho isomers, whereas para‐C₇₀(CCl₃)H decomposes back into pristine C₇₀.     

Metallo‐supramolecular block copolymer micelles: Improved preparation and characterization

Micelles prepared from amphiphilic block copolymers in which a poly(styrene) segment is connected to a poly(ethylene oxide) block via a bis‐(2,2′:6′,2″‐terpyridine‐ruthenium) complex have been intensely studied. In most cases, the micelle populations were found to be strongly heterogeneous in size because of massive micelle/micelle aggregation. In the study reported in this article we tried to improve the homogeneity of the micelle population. The variant preparation procedure developed, which is described here, was used to prepare two “protomer”‐type micelles: PS₂₀‐[Ru]‐PEO₇₀ and PS₂₀‐[Ru]‐PEO₃₇₅. The dropwise addition of water to a solution of the compounds in dimethylformamide was replaced by the controlled addition of water by a syringe pump. The resulting micelles were characterized by sedimentation velocity and sedimentation equilibrium analyses in an analytical ultracentrifuge and by transmission electron microscopy of negatively stained samples. Sedimentation analysis showed virtually unimodal size distributions, in contrast to the findings on micelles prepared previously. PS₂₀‐[Ru]‐PEO₇₀ micelles were found to have an average molar mass of 318,000 g/mol (corresponding to 53 protomers per micelle, which is distinctly less than after micelle preparation by the standard method) and an average hydrodynamic diameter (d_h) of 18 nm. For PS₂₀‐[Ru]‐PEO₃₇₅ micelles, the corresponding values were M = 603,000 g/mol (31 protomers per micelle) and d_h = 34 nm. The latter particles were found to be identical to the “equilibrium” micelles prepared in pure water. Both micelle types had a very narrow molar mass distribution but a much broader distribution of s values and thus of hydrodynamic diameters. This indicates a conformational heterogeneity that is stable on the time scale of sedimentation velocity analysis. The findings from electron microscopy were in disagreement with those from the sedimentation analysis both in average micelle diameter and in the width of the distributions, apparently because of imperfections in the staining procedure. The preparation procedure described also may be useful in micelle formation from other types of protomers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4458–4465, 2004     

Synthesis of highly water soluble C60 end‐capped vinyl ether oligomers with well‐defined structure

Highly water soluble [60]fullerene (C₆₀) end‐capped vinyl ether (VE) oligomers with well‐defined structure were synthesized by living cationic polymerization technique. The addition reaction between 1‐octynylfulleride anion and oligomeric cationic species of VEs with pendant acetoxyl or malonic ester functions afforded the precursor C₆₀ end‐capped oligomers. The living VE oligomers were prepared by living cationic polymerization of diethyl 2‐(vinyloxy)ethylmalonate (VOEM) and 2‐acetoxyethyl vinyl ether (AcOVE) by the CH₃CH(OR)Cl/ZnI₂ [R = CH₂CH₂OCOCH₃ and CH₂CH₂CH(COOEt)₂, respectively] initiating system. The precursors were obtained as dark brown gummy solid in 33 and 72% yield for AcOVE and VOEM, respectively. UV‐vis and ¹³C NMR spectroscopy indicated the formation of 1,2‐disubstituted dihydrofullerene derivatives. Hydrolysis of the precursors proceeded quantitatively to give the water‐soluble C₆₀ end‐capped oligomers having oligo(sodium 2‐vinyloxyethylmalonate) [oligo(VOEMNa)] and oligo(2‐hydroxyethyl vinyl ether) [oligo(HOVE)] moieties. Solubility measurements revealed the water‐soluble C₆₀ end‐capped oligomer with oligo(VOEMNa) chain to have the excellent aqueous solubility compared to that of the water‐soluble C₆₀ derivatives thus far known; the maximum solubility in water is 96.6 mg/mL, which corresponds to 25.9 mg/mL of the C₆₀ moiety. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3578–3585, 2000     

Self‐Assembly of Fullerene‐Based Janus Particles in Solution: Effects of Molecular Architecture and Solvent

Two molecular Janus particles based on amphiphilic [60]fullerene (C₆₀) derivatives were designed and synthesized by using the regioselective Bingel–Hirsh reaction and the click reaction. These particles contain carboxylic acid functional groups, a hydrophilic fullerene (AC₆₀), and a hydrophobic C₆₀ in different ratios and have distinct molecular architectures: 1:1 (AC₆₀–C₆₀) and 1:2 (AC₆₀–2C₆₀). These molecular Janus particles can self‐assemble in solution to form aggregates with various types of micellar morphology. Whereas vesicular morphology was observed for both AC₆₀–C₆₀ and AC₆₀–2C₆₀ in tetrahydrofuran, in a mixture of N,N‐dimethylformamide (DMF)/water, spherical micelles and cylindrical micelles were observed for AC₆₀–C₆₀ and AC₆₀–2C₆₀, respectively. A mechanism of formation was tentatively proposed based on the effects of molecular architecture and solvent polarity on self‐assembly.     

Transient Absorption Spectral characterization of Electron Transfer between Fullerenes（C60／C70）and N,N,N’，N’—Tetra（p—methylphenyl）—4,4’—diamino—1,1’—diphenyl Sulphide（TPDAS）

In search of new systems with a photoexcited redox pair which exhibits a strong and stable photoinduced absorption band to understand the photophyscial and photochemical properties of electron transfer between fullernes (C60/C70) and organic donor[N,N,N’，N’-tetra(p-methylphenyl)-4,4’-diamino-1,1’-diphenyl sulphide(TPDAS)],we studied characteristic absorption spectra in the near-IR region obtained from 532nm nanosecond laser flash photolysis of a mixture of the fullerenes (C60/C70) and TPDAS in polar solvents.When fullerenes (C60/C70)were photoexcithed,the rise of the radical anion of fullerenes (C60/C70)with the rapid decay of their excited triplet states were observed in benzonitrile.It can be deduced that the electron transfer reaction does take place from TPDAS to excithed triplet state of rullerens(C60/C70).The rate consants(ket)and quantum yiekls(φet) of this process have been also evaluated.